期刊文献+
共找到118,635篇文章
< 1 2 250 >
每页显示 20 50 100
不同草莓品种果实品质的比较研究 被引量:44
1
作者 陈卫平 《江西农业学报》 CAS 2010年第9期46-48,共3页
以大棚草莓栽培品种丰香、明宝、雪蜜、红颊、章姬为试材,从果实外观品质和果实营养成分上对5个草莓品种进行了分析研究。结果表明,红颊和章姬草莓果实大,平均单果重分别为21.25和21.97 g,外形美观,富有光泽;在果实经济性状上红颊优于其... 以大棚草莓栽培品种丰香、明宝、雪蜜、红颊、章姬为试材,从果实外观品质和果实营养成分上对5个草莓品种进行了分析研究。结果表明,红颊和章姬草莓果实大,平均单果重分别为21.25和21.97 g,外形美观,富有光泽;在果实经济性状上红颊优于其他4个品种,果实酸甜适口,香味浓,口感好,品质极佳,果实硬度适中,耐贮运性好,是当前大棚草莓栽培中较为理想的优质大果型草莓品种。雪蜜和丰香草莓果实营养成分上无显著差异,但在耐储性上,雪蜜果实硬度较低,不利于远距离运输,而丰香草莓果实硬度达到了4.00 Pa/cm2,耐储性好。在实际栽培过程中应结合实际情况加以选用。明宝草莓果实颜色橙红色,光泽强,香气浓,酸甜适中,平均单果重为19.32 g,可溶性固形物、蛋白质、糖、酸和维生素C含量上在5个品种中处于中间位置,但其果实硬度最低,只有2.53 Pa/cm2,耐储性最差,适宜在当地自产自销。 展开更多
关键词 草莓品种 果实品质 比较研究 different Fruit Quality Study 果实硬度 草莓果实 果实营养成分 平均单果重 耐储性 丰香草莓 大棚草莓 草莓栽培 可溶性固形物 果实外观品质 果实经济性状 远距离运输 自产自销 中间位置
下载PDF
A new bearing fault diagnosis method based on modified convolutional neural networks 被引量:42
2
作者 Jiangquan ZHANG Yi SUN +3 位作者 Liang GUO Hongli GAO Xin HONG Hongliang SONG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第2期439-447,共9页
Fault diagnosis is vital in manufacturing system.However,the first step of the traditional fault diagnosis method is to process the signal,extract the features and then put the features into a selected classifier for ... Fault diagnosis is vital in manufacturing system.However,the first step of the traditional fault diagnosis method is to process the signal,extract the features and then put the features into a selected classifier for classification.The process of feature extraction depends on the experimenters’experience,and the classification rate of the shallow diagnostic model does not achieve satisfactory results.In view of these problems,this paper proposes a method of converting raw signals into twodimensional images.This method can extract the features of the converted two-dimensional images and eliminate the impact of expert’s experience on the feature extraction process.And it follows by proposing an intelligent diagnosis algorithm based on Convolution Neural Network(CNN),which can automatically accomplish the process of the feature extraction and fault diagnosis.The effect of this method is verified by bearing data.The influence of different sample sizes and different load conditions on the diagnostic capability of this method is analyzed.The results show that the proposed method is effective and can meet the timeliness requirements of fault diagnosis. 展开更多
关键词 BEARING Convolutional NEURAL networks different load DOMAINS FAULT identification RAW SIGNALS FAULT diagnosis
原文传递
Rhizospheric microbial communities are driven by Panax ginseng at different growth stages and biocontrol bacteria alleviates replanting mortality 被引量:33
3
作者 Linlin Dong Jiang Xu +7 位作者 Lianjuan Zhang Ruiyang Cheng Guangfei Wei He Su Juan Yang Jun Qian Ran Xu Shilin Chen 《Acta Pharmaceutica Sinica B》 SCIE CAS CSCD 2018年第2期272-282,共11页
The cultivation of Panax plants is hindered by replanting problems, which may be caused by plantdriven changes in the soil microbial community. Inoculation with microbial antagonists may efficiently alleviate replanti... The cultivation of Panax plants is hindered by replanting problems, which may be caused by plantdriven changes in the soil microbial community. Inoculation with microbial antagonists may efficiently alleviate replanting issues. Through high-throughput sequencing, this study revealed that bacterial diversity decreased,whereas fungal diversity increased, in the rhizosphere soils of adult ginseng plants at the root growth stage under different ages. Few microbial community, such as Luteolibacter, Cytophagaceae, Luteibacter, Sphingomonas,Sphingomonadaceae, and Zygomycota, were observed; the relative abundance of microorganisms, namely,Brevundimonas, Enterobacteriaceae, Pandoraea, Cantharellales, Dendryphion, Fusarium, and Chytridiomycota,increased in the soils of adult ginseng plants compared with those in the soils of 2-year-old seedlings. Bacillus subtilis 50-1, a microbial antagonist against the pathogenic Fusarium oxysporum, was isolated through a dual culture technique. These bacteria acted with a biocontrol efficacy of 67.8%. The ginseng death rate and Fusarium abundance decreased by 63.3% and 46.1%, respectively, after inoculation with B. subtilis 50-1. Data revealed that microecological degradation could result from ginseng-driven changes in rhizospheric microbial communities;these changes are associated with the different ages and developmental stages of ginseng plants. Biocontrol using microbial antagonists alleviated the replanting problem. 展开更多
关键词 Panax ginseng Microbial communities Replanting problem High-throughput sequencing different ages BIOREMEDIATION
原文传递
Moxibustion regulates inflammatory mediators and colonic mucosal barrier in ulcerative colitis rats 被引量:31
4
作者 Tie-Ming Ma Na Xu +3 位作者 Xian-De Ma Zeng-Hua Bai Xing Tao Hong-Chi Yan 《World Journal of Gastroenterology》 SCIE CAS 2016年第8期2566-2575,共10页
AIM: To observe the efficacy and mechanism of grain-sized moxibustion at different acupoints in a rat model of ulcerative colitis (UC). METHODS: Sprague-Dawley rats were randomly divided into control, UC model, grain-... AIM: To observe the efficacy and mechanism of grain-sized moxibustion at different acupoints in a rat model of ulcerative colitis (UC). METHODS: Sprague-Dawley rats were randomly divided into control, UC model, grain-sized moxibustion at a single acupoint (CV 12), grain-sized moxibustion at two acupoints (CV 12 and CV 4), grain-sized moxibustion at three acupoints (CV 12, CV 4, and ST 36), and medication groups (n = 8/group). The UC model was established by enema of trinitrobenzene sulfonic acid. Direct moxibustion was used once a day for 7 d. Disease activity index (DAI) was evaluated before and after the treatment. Morphologic changes of intestinal tissue were observed under an optical microscope. The expression of tumor necrosis factor (TNF)-alpha and p38 mitogen-activated protein kinase (p38MAPK) in colonic tissue was detected using Western blot, and the levels of occludin and zonula occludens-1 (ZO-1) mRNAs were detected using reverse transcription PCR. RESULTS: Compared with the control group, the intestinal mucosae were incomplete in the model group, glandular structures were irregular, and submucosae were edematous, hyperemic, and infiltrated with inflammatory cells. The DAI scores and expression of TNF-alpha and p38MAPK were increased significantly in the model group compared to controls (Ps < 0.01), while the mRNA levels of occludin and ZO-1 were reduced significantly (Ps < 0.01). Compared with the model group, colonic mucosa and the arrangement of glands were complete and regular in the treatment groups. DAI scores and the expression of TNF-alpha and p38MAPK were reduced significantly in moxibustion groups compared to controls (Ps < 0.01), while the mRNA levels of occludin and ZO-1 were increased significantly (Ps < 0.01). The improvements in the above indices in the three acupoints group and the medication group were superior to those in the single and two acupoints groups (all P < 0.05). CONCLUSION: Reduction of TNF-alpha and p38MAPK and increased expression of occludin and ZO-1 in colonic tissue rep 展开更多
关键词 different acupoints Grain-sized moxibustion Inflammatory factors Intestinal mucosal barrier Ulcerative colitis
下载PDF
Characteristics of land surface thermal-hydrologic processes for different regions over North China during prevailing summer monsoon period 被引量:28
5
作者 ZHANG Qiang ZENG Jian ZHANG LiYang 《Science China Earth Sciences》 SCIE EI CAS 2012年第11期1872-1880,共9页
The observation stations of Northern China are divided into three regions:the arid Northwest China,the Loess Plateau,and the cool Northeast China.The consistencies,differences,and associated mechanisms of land surface... The observation stations of Northern China are divided into three regions:the arid Northwest China,the Loess Plateau,and the cool Northeast China.The consistencies,differences,and associated mechanisms of land surface thermal-hydrologic processes among the three regions were studied based on the normalization of major variables of land surface thermal-hydrologic processes,using data collected during prevailing summer monsoon period(July and August,2008).It is shown that differences of surface thermal-hydrologic processes are remarkable among the three regions because of different impacts of summer monsoon.Especially their soil wet layers occur at different depths,and the average albedo and its diurnal variations are distinctly different.Surface net short-wave radiation in the Loess Plateau is close to that in the cool Northeast China,but its surface net long-wave radiation is close to that in the arid Northwest China.And the ratio of net radiation to global solar radiation in the cool Northeast China is higher than the other two regions,though its temperature is lower.There are obvious regional differences in the ratios of surface sensible and latent heat fluxes to net radiation for the three regions because of distinct contribution of sensible and latent heat fluxesto land surface energy balance.The three regions are markedly different in the ratio of water vapor flux to pan evaporation,but they are consistent in the ratio of water vapor flux to precipitation.These results not only indicate different influences of climate and environmental factors on land surface thermal-hydrologic processes in the three regions,but also show that summer monsoon is important in the formation and variation of the pattern of land surface thermal-hydrologic processes. 展开更多
关键词 different regions of North China prevailing summer monsoon period coordinated experiment land surface thermalhydrologic processes influence factors
原文传递
A comparative study of the specific surface area and pore structure of different shales and their kerogens 被引量:26
6
作者 CAO TaoTao SONG ZhiGuang +1 位作者 WANG SiBo XIA Jia 《Science China Earth Sciences》 SCIE EI CAS CSCD 2015年第4期510-522,共13页
The pore structures and controlling factors of several different Paleozoic shales from Southern China and their kerogens were studied using nitrogen adsorption and scanning electron microscopy methods. The results ind... The pore structures and controlling factors of several different Paleozoic shales from Southern China and their kerogens were studied using nitrogen adsorption and scanning electron microscopy methods. The results indicate that: 1) The specific surface area is 2.22-3.52 m2/g and has no correlation with the TOC content of the Permian Dalong Formation shales, nanopores are extremely undeveloped in the Dalong Formation kerogens, which have specific surface areas of 20.35-27.49 me/g; 2) the specific surface area of the Silurian Longmaxi Formation shales is in the range of 17.83-29.49 m2/g and is positively correlated with TOC content, the kerogens from the Longmaxi Formation have well-developed nanopores, with round or elliptical shapes, and the specific surface areas of these kerogens are as high as 279.84-300.3 m2/g; 3) for the Niutitang Formation shales, the specific surface area is 20.12-29.49 m2/grock and increases significantly with increasing TOC and smectite content. The Niuti- tang Formation kerogens develop a certain amount of nanopores with a specific surface area of 161.2 m2/g. Oil shale was also examined for comparison, and was found to have a specific surface area of 19.99 m2/g. Nanopores are rare in the Youganwo Formation kerogen, which has a specific surface area of only 5.54 m2/g, suggesting that the specific surface area of oil shale is due mainly to the presence of smectite and other clay minerals. The specific surface area and the number of pores present in shales are closely related to TOC, kerogen type and maturity, smectite content, and other factors. Low-maturity kerogen has very few nanopores and therefore has a very low specific surface area, whereas nanopores are abundant in mature to over- mature kerogen, leading to high specific surface areas. The Longmaxi Formation kerogen has more developed nanopores and a higher specific surface area than the Niutitang Formation kerogen, which may be due to differences in the kerogen type and maceral components. A high content of smectite may a 展开更多
关键词 different Paleozoic shales KEROGEN specific surface area NANOPORE MATURITY kerogen type
原文传递
Effect of Long-Term Application of K Fertilizer and Wheat Straw to Soil on Crop Yield and Soil K Under Different Planting Systems 被引量:25
7
作者 TAN De-shui JIN Ji-yun HUANG Shao-wen LI Shu-tian HE Ping 《Agricultural Sciences in China》 CAS CSCD 2007年第2期200-207,共8页
Effect of application of K fertilizer and wheat straw to soil on crop yield and status of soil K in the plough layer under different planting systems was studied. The experiments on long-term application of K fertiliz... Effect of application of K fertilizer and wheat straw to soil on crop yield and status of soil K in the plough layer under different planting systems was studied. The experiments on long-term application of K fertilizer and wheat straw to soil in Hebei fluvo aquic soil and Shanxi brown soil in northern China were begun in 1992. The results showed that K fertilizer and straw could improve the yields of wheat and maize with the order of NPK + St 〉 NPK 〉 NP + St 〉 NP, and treatment of K fertilizer made a significant difference to NP, and the efficiency of K fertilizer in maize was higher than in wheat under rotation system of Hebei. In contrast with Shanxi, the wastage of soil potassium was a more serious issue in the rotation system in Hebei, only treatment of NPK + St showed a surplus of potassium and the others showed a wane. K fertilizer and straw could improve the content of water-soluble K, nonspecifically adsorbed K, non-exchangeable K, mineral K, and total K in contrast to NP; however, K fertilizer and straw reduce the proportion of mineral K and improve proportion of other forms of potassium in the two locating sites. Compared with the beginning of orientation, temporal variability character of soil K content and proportion showed a difference between the two soil types; furthermore, there was a decrease in the content of mineral K and total K simultaneously in the two locating sites. As a whole, the effect of K fertilizer applied to soil directly excelled to wheat straw to soil. Wheat straw to soil was an effective measure to complement potassium to increase crop yield and retard the decrease of soil K. 展开更多
关键词 different planting systems long-term application of K fertilizer wheat straw to soil crop yield soil K
下载PDF
中国与加拿大高校实验技术人员队伍建设比较 被引量:25
8
作者 王友建 吴元学 岳进 《实验技术与管理》 CAS 2006年第7期130-131,138,共3页
该文从观念、体制和结构等3方面对中国和加拿大高校实验技术人员队伍建设之间的差异进行比较,从差异中寻求突破,提出了我国高校实验技术人员队伍建设的具体措施。
关键词 实验技术人员队伍建设 差异 TA制度 岗位聘任
下载PDF
Effect of Sancaijiangtang on plasma nitric oxide and endothelin-1 levels in patients with type 2 diabetes mellitus and vascular dementia:a single-blind randomized controlled trial 被引量:25
9
作者 Guo Qiang Cao Wenzhai +4 位作者 Zhao Huan Zhu Yuxia Yang Dongdong Zhong Sen Chen Qiu 《Journal of Traditional Chinese Medicine》 SCIE CAS CSCD 2015年第4期375-380,共6页
OBJECTIVE: To observe the effect of Sancaijiangtang powders on plasma nitric oxide and endothelin-1 levels. We sought to identify the common pathological link and mechanism of action for Traditional Chinese medicine i... OBJECTIVE: To observe the effect of Sancaijiangtang powders on plasma nitric oxide and endothelin-1 levels. We sought to identify the common pathological link and mechanism of action for Traditional Chinese medicine in type 2 diabetes mellitus and vascular dementia,and to explicate the material basis for treating the different diseases with the same method in Traditional Chinese Medicine.METHODS: In total,168 patients with type 2 diabetes mellitus and vascular dementia were enrolled in the study,and randomly divided into two groups by simple randomization. Patients in the treatment group received oral Sancaijiangtang powders with pioglitazone hydrochloride three times daily,while patients in the control group received pioglitazone hydrochloride alone. The treatment course was for12 weeks. Mini-mental state examinations(Chinese version) and Montreal Cognitive Assessments(Beijing version) were performed,and fasting plasma glucose,fasting insulin,hemoglobin A1 c,homeostasis model assessment of insulin resistance,plasma nitric oxide and endothelin-1 levels were measured before and after the treatment.RESULTS: The post-treatment levels for all measurements in both groups were better than pre-treatment levels(P < 0.05). The post-treatment levels for all measurements in the treatment group were better than the levels measured in the control group(P < 0.05).CONCLUSION: Type 2 diabetes mellitus and vascular dementia have common pathological mechanisms for insulin resistance and endothelium dysfunction. Sancaijiangtang powders could improve the release of nitric oxide and inhibit the secretion of endothelin-1. Therefore,the material basis exists for treating the different diseases with the same method in Traditional Chinese Medicine. 展开更多
关键词 Diabetes mellitus type 2 Dementia vascular Insulin resistance different diseases in same treatment Randomized controlled trial San-caijiangtang
原文传递
Research on the Performance of Supercritical CO_2 Dry Gas Seal with Different Deep Spiral Groove 被引量:20
10
作者 DU Qiuwan ZHANG Di 《Journal of Thermal Science》 SCIE EI CAS CSCD 2019年第3期547-558,共12页
The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kin... The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kinds of grooves are obtained. The influence of inlet temperature, inlet pressure, velocity and film thickness on performance is analyzed compared with air DGS. The average film pressure, open force and leakage decrease while the average face temperature and flow velocity increase as the spiral groove number increases. The average film pressure, average face temperature, open force and leakage of DGS with radial different deep groove are higher than those of DGS with circumferential different deep groove respectively under the same spiral groove number while the average flow velocity is the opposite. SCO_2 DGS can generate larger average film pressure, open force and leakage with lower average face temperature than air DGS. SCO_2 DGS could maintain better sealing performance despite larger leakage with the variations of inlet temperature, inlet pressure, velocity and film thickness. The variables hold a more remarkable influence on SCO_2 DGS compared with air DGS. 展开更多
关键词 SUPERCRITICAL carbon dioxide different DEEP SPIRAL GROOVE dry gas SEAL thermal-fluid-solid coupling method
原文传递
Energy-efficient Approach to Minimizing the Energy Consumption in An Extended Job-shop Scheduling Problem 被引量:20
11
作者 TANG Dunbing DAI Min 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2015年第5期1048-1055,共8页
The traditional production planning and scheduling problems consider performance indicators like time, cost and quality as optimization objectives in manufacturing processes. However, environmentally-friendly factors ... The traditional production planning and scheduling problems consider performance indicators like time, cost and quality as optimization objectives in manufacturing processes. However, environmentally-friendly factors like energy consumption of production have not been completely taken into consideration. Against this background, this paper addresses an approach to modify a given schedule generated by a production plarming and scheduling system in a job shop floor, where machine tools can work at different cutting speeds. It can adjust the cutting speeds of the operations while keeping the original assignment and processing sequence of operations of each job fixed in order to obtain energy savings. First, the proposed approach, based on a mixed integer programming mathematical model, changes the total idle time of the given schedule to minimize energy consumption in the job shop floor while accepting the optimal solution of the scheduling objective, makespan. Then, a genetic-simulated annealing algorithm is used to explore the optimal solution due to the fact that the problem is strongly NP-hard. Finally, the effectiveness of the approach is performed small- and large-size instances, respectively. The experimental results show that the approach can save 5%-10% of the average energy consumption while accepting the optimal solution of the makespan in small-size instances. In addition, the average maximum energy saving ratio can reach to 13%. And it can save approximately 1%-4% of the average energy consumption and approximately 2.4% of the average maximum energy while accepting the near-optimal solution of the makespan in large-size instances. The proposed research provides an interesting point to explore an energy-aware schedule optimization for a traditional production planning and scheduling problem. 展开更多
关键词 energy consumption MAKESPAN production planning and scheduling job-shop floor different cutting speeds
下载PDF
QTL editing confers opposing yield performance in different rice varieties 被引量:20
12
作者 Lan Shen Chun Wang +6 位作者 Yaping Fu Junjie Wang Qing Liu Xiaoming Zhang Changjie Yan Qian Qian Kejian Wang 《Journal of Integrative Plant Biology》 SCIE CAS CSCD 2018年第2期89-93,共5页
Grain yield is one of the most important and complex trait for genetic improvement in crops; it is known to be controlled by a number of genes known as quantitative trait loci(QTLs). In the past decade, many yield-c... Grain yield is one of the most important and complex trait for genetic improvement in crops; it is known to be controlled by a number of genes known as quantitative trait loci(QTLs). In the past decade, many yield-contributing QTLs have been identified in crops.However, it remains unclear whether those QTLs confer the same yield performance in different genetic backgrounds. Here, we performed CRISPR/Cas_9-mediated QTL editing in five widely-cultivated rice varieties and revealed that the same QTL can have diverse, even opposing, effects on grain yield in different genetic backgrounds. 展开更多
关键词 QTL editing confers opposing yield performance in different rice varieties Figure
原文传递
中、外十项全能运动员成绩差距原因及对策研究 被引量:16
13
作者 李继伟 任保国 《中国体育科技》 北大核心 2003年第10期38-42,56,共6页
通过文献资料调研、访问调查、数理统计、比较分析等方法 ,对我国与世界男子十项全能运动成绩差距原因进行比较研究。结果表明 :我国十项全能各单项成绩、技术等级发展不均衡 ,十项全能成绩与世界十项全能成绩比较差距较大 ,投掷项目是... 通过文献资料调研、访问调查、数理统计、比较分析等方法 ,对我国与世界男子十项全能运动成绩差距原因进行比较研究。结果表明 :我国十项全能各单项成绩、技术等级发展不均衡 ,十项全能成绩与世界十项全能成绩比较差距较大 ,投掷项目是影响我国十项全能发展的主要因素 ,并提出对策建议。 展开更多
关键词 中国 国外 十项全能 运动员 单项成绩 技术等级 投掷类项目 “全能能手” 训练力度
下载PDF
Soil Quality Assessment of Acid Sulfate Paddy Soils with Different Productivities in Guangdong Province,China 被引量:19
14
作者 LIU Zhan-jun ZHOU Wei +5 位作者 SHEN Jian-bo LI Shu-tian LIANG Guo-qing WANG Xiu-bin SUN Jing-wen AI Chao 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2014年第1期177-186,共10页
Land conversion is considered an effective measure to ensure national food security in China, but little information is available on the quality of low productivity soils, in particular those in acid sulfate soil regi... Land conversion is considered an effective measure to ensure national food security in China, but little information is available on the quality of low productivity soils, in particular those in acid sulfate soil regions. In our study, acid sulfate paddy soils were divided into soils with high, medium and low levels based on local rice productivity, and 60 soil samples were collected for analysis. Twenty soil variables including physical, chemical and biochemical properties were determined. Those variables that were significantly different between the high, medium and low productivity soils were selected for principal component analysis, and microbial biomass carbon (MBC), total nitrogen (TN), available silicon (ASi), pH and available zinc (AZn) were retained in the minimum data set (MDS). After scoring the MDS variables, they were integrated to calculate a soil quality index (SQI), and the high, medium and low productivity paddy soils received mean SQI scores of 0.95, 0.83 and 0.60, respectively. Low productivity paddy soils showed worse soil quality, and a large discrepancy was observed between the low and high productivity paddy soils. Lower MBC, TN, ASi, pH and available K (AK) were considered as the primary limiting factors. Additionally, all the soil samples collected were rich in available P and AZn, but deficient in AK and ASi. The results suggest that soil AK and ASi deficiencies were the main limiting factors for all the studied acid sulfate paddy soil regions. The application of K and Si on a national basis and other sustainable management approaches are suggested to improve rice productivity, especially for low productivity paddy soils. Our results indicated that there is a large potential for increasing productivity and producing more cereals in acid sulfate paddy soil regions. 展开更多
关键词 soil quality assessment acid sulfate paddy soil soil quality index different productivity
下载PDF
Influence of different weather events on concentrations of particulate matter with different sizes in Lanzhou,China 被引量:19
15
作者 Xinyuan Feng Shigong Wang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2012年第4期665-674,共10页
The formation and development of weather events has a great impact on the diffusion, accumulation and transport of air pollutants, and causes great changes in the particulate pollution level. It is very important to s... The formation and development of weather events has a great impact on the diffusion, accumulation and transport of air pollutants, and causes great changes in the particulate pollution level. It is very important to study their influence on particulate pollution. Lanzhou is one of the most particulate-polluted cities in China and even in the world. Particulate matter (PM) including TSP, PM〉10, PMzs-10, PM2.5 and PM1.0 concentrations were simultaneously measured during 2005-2007 in Lanzhou to evaluate the influence of three kinds of weather events - dost, precipitation and cold front - on the concentrations of PM with different sizes and detect the temporal evolution. The main results are as follows: (1) the PM pollution in Lanzhou during dust events was very heavy and the rate of increase in the concentration of PM2.5-10 was the highest of the five kinds of particles. During dust-storm events, the highest peaks of the concentrations of fine particles (PM2.5 and PM1.0) occurred 3 hr later than those of coarse particles (PM〉10 and PM/.5-10). (2) The major effect of precipitation events on PM is wet scavenging. The scavenging rates of particles were closely associated with the kinds of precipitation events. The scavenging rates of TSP, PM〉10 and PMa.5-10 by convective precipitation were several times as high as those caused by frontal precipitation for the same precipitation amount, the reason being the different formation mechanism and precipitation characteristics of the two kinds of precipitation. Moreover, there exists a limiting value for the scavenging rates of particles by precipitation. (3) The major effect of cold-front events on particles is clearance. However, during cold-front passages, the PM concentrations could sometimes rise first and decrease afterwards, which is the critical difference in the influence of cold fronts on the concentrations of particulate pollutants vs. gaseous pollutants. 展开更多
关键词 particulate matter with different sizes dust event precipitation event cold-front event
原文传递
不同环节灌溉用水效率及节水潜力分析 被引量:19
16
作者 崔远来 谭芳 郑传举 《水科学进展》 EI CAS CSCD 北大核心 2010年第6期788-794,共7页
以漳河灌区为例,在对灌区渠系进行等效概化的基础上,采用经验公式法进行不同工况下不同环节灌溉用水效率的分析计算。结果表明总干及干渠环节和分、斗、农渠环节的渠道水利用系数较大,而支干、分干和支渠环节的渠道水利用系数偏小,渠道... 以漳河灌区为例,在对灌区渠系进行等效概化的基础上,采用经验公式法进行不同工况下不同环节灌溉用水效率的分析计算。结果表明总干及干渠环节和分、斗、农渠环节的渠道水利用系数较大,而支干、分干和支渠环节的渠道水利用系数偏小,渠道断面大小、长度及防渗率是导致渠道水利用系数差异的主要原因。计算分析了不同条件下的灌溉用水效率阈值,达到相应阈值时的投资,以及净节水量和节水率,分析了投资与灌溉用水效率阈值及节水率的关系。表明随投资的增加灌溉用水效率及节水率均提高,但其过程符合报酬递减规律,且节水率的报酬递减速度更快。 展开更多
关键词 环节 灌溉用水效率 节水率 潜力分析 different water SAVING IRRIGATION EFFICIENCY 渠道水利用系数 阈值 投资 经验公式法 漳河灌区 渠道断面 计算分析 分析计算 递减速度 递减规律 等效概化 报酬 节水量
下载PDF
High-frequency (50 Hz) electroacupuncture ameliorates cognitive impairment in rats with amyloid beta 1–42-induced Alzheimer's disease 被引量:18
17
作者 Chao-Chao Yu Ying Wang +4 位作者 Feng Shen Li-Hong Kong Ya-Wen Wang Hua Zhou Lei Tang 《Neural Regeneration Research》 SCIE CAS CSCD 2018年第10期1833-1841,共9页
Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer’s disease.Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture.Rat models of Alzheimer’s disease were ... Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer’s disease.Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture.Rat models of Alzheimer’s disease were established by injecting amyloid beta 1–42(Aβ_(1–42))into the bilateral lateral ventricles.Electroacupuncture at 2,30,and 50 Hz was carried out at Baihui(GV20;15°obliquely to a depth of 2mm)and Shenshu(BL23;perpendicularly to 4–6 mm depth),once a day for 20 minutes(each),for 15 days,taking a break every 7 days.The Morris water maze test was conducted to assess the learning and memory.The expression levels of glycogen synthase kinase-3β(GSK-3β),p Ser9-GSK-3β,p Tyr216-GSK-3β,amyloid precursor protein and Aβ_(1–40) in the hippocampus were determined by western blot assay.Results demonstrated that electroacupuncture treatment at different frequencies markedly improved learning and memory ability,increased synaptic curvatures,decreased the width of synaptic clefts,thickened postsynaptic densities,and downregulated the expression of GSK-3β,amyloid precursor protein,and Aβ_(1–40).pSer9-GSK-3βexpression markedly decreased,while p Tyr216-GSK-3βexpression increased.High-frequency(50 Hz)electroacupuncture was more effective than low(2 Hz)or medium-frequency(30 Hz)electroacupuncture.In conclusion,electroacupuncture treatment exerts a protective effect against Aβ_(1–42)-induced learning and memory deficits and synapse-ultrastructure impairment via inhibition of GSK-3βactivity.Moreover,high-frequency electroacupuncture was the most effective therapy. 展开更多
关键词 nerve regeneration ELECTROACUPUNCTURE different frequencies Alzheimer's disease cognitive impairment HIPPOCAMPUS glycogen synthase kinase-3β synaptic curvatures width of synaptic cleft postsynaptic density Baihui(GV20) Shenshu(BL23) neural regeneration
下载PDF
论湿地功能及其保护 被引量:14
18
作者 钱芳 《哈尔滨学院学报》 2003年第9期54-59,共6页
本文从湿地的界定、类型及其功能三个方面详细介绍了湿地有关知识 ,并通过对中国湿地的特征、现状的研究 ,以及我国近年来对湿地保护所采取的措施、前景展望 ,揭示了保护湿地的紧迫性和重要性 ,以使湿地资源得到永续利用。
关键词 湿地 特征 环境保护 功能 中国
下载PDF
Characteristics of Soil Organic Carbon and Total Nitrogen in Rubber Plantations Soil at Different Age Stages in the Western Region of Hainan Island 被引量:17
19
作者 吴志祥 谢贵水 +2 位作者 陶忠良 周兆德 王旭 《Agricultural Science & Technology》 CAS 2010年第1期147-153,共7页
[Objective]The aim was to study on the characteristics of soil organic carbon and nitrogen in rubber (Hevea brasiliensis Muell-Arg) plantations at different age stages in the western region of Hainan Island,so as to... [Objective]The aim was to study on the characteristics of soil organic carbon and nitrogen in rubber (Hevea brasiliensis Muell-Arg) plantations at different age stages in the western region of Hainan Island,so as to evaluate the ecological benefits of rubber plantations and provide basic data for studying the effect of tropical land utilization/cover change on the global carbon and nitrogen cycle. [Method]The situs was in Danzhou city,western region of Hainan Island,and the samples were four kinds of rubber plantations soil at different ages and one kind of control check (pepper,Piper nigrum L.) soil. In this research,four quadrats were set up in each sample,and the size of each was 20 cm×20 cm. Four specimens were gathered from four layers of 0-15,15-30,30-45,45-60,and the average of them was the last analysis result of each sample. Soil density was measured by cutting ring method,soil containing and hygroscopic water was detected by oven drying method,soil organic carbon (SOC) was measured by low temperature heated outside potassium dichromate oxidation-colorimetry method,and soil total nitrogen (STN) was detected by semimicro Kjeldahl method. [Result]SOC contents of different layers in rubber plantations soil at different age stages (including the CK pepper soil,the same as below) varied little,and the content of SOC in surface layer (0-15 cm) was higher,while the underlayer (45-60 cm) was lower than the average value; there was significant difference in SOC content among different kinds of soil,and the content was of 6.03-7.78 g/kg,tapping young trees (7 years) CK pepper mature age trees (30 years) prophase of young trees (2 years) tapping trees (16 years); there was no significant difference in SOC storage among different kinds of soil,and the storage was of 61.33-74.29 t/hm2,mature age trees (30 years) tapping young trees (7 years) prophase of young trees (2 years) CK pepper tapping trees (16 years); there was significant difference in STN content 展开更多
关键词 different age stages of trees Rubber (Hevea brasiliensis) plantations Soil organic carbon (SOC) Soil total nitrogen (STN) Hainan Island
下载PDF
Recent Progress in Studies of the Variabilities and Mechanisms of the East Asian Monsoon in a Changing Climate 被引量:16
20
作者 Wen CHEN Lin WANG +4 位作者 Juan FENG Zhiping WEN Tiaojiao MA Xiuqun YANG Chenghai WANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2019年第9期887-901,共15页
Located in a monsoon domain,East Asia suffers devastating natural hazards induced by anomalous monsoon behaviors.East Asian monsoon(EAM)research has traditionally been a high priority for the Chinese climate community... Located in a monsoon domain,East Asia suffers devastating natural hazards induced by anomalous monsoon behaviors.East Asian monsoon(EAM)research has traditionally been a high priority for the Chinese climate community and is particularly challenging in a changing climate where the global mean temperature has been rising.Recent advances in studies of the variabilities and mechanisms of the EAM are reviewed in this paper,focusing on the interannual to interdecadal time scales.Some new results have been achieved in understanding the behaviors of the EAM,such as the evolution of the East Asian summer monsoon(EASM),including both its onset and withdrawal over the South China Sea,the changes in the northern boundary activity of the EASM,or the transitional climate zone in East Asia,and the cycle of the EASM and the East Asian winter monsoon and their linkages.In addition,understanding of the mechanism of the EAM variability has improved in several aspects,including the impacts of different types of ENSO on the EAM,the impacts from the Indian Ocean and Atlantic Ocean,and the roles of mid-to high-latitude processes.Finally,some scientific issues regarding our understanding of the EAM are proposed for future investigation. 展开更多
关键词 EAST ASIAN summer MONSOON EAST ASIAN winter MONSOON CHANGING CLIMATE MONSOON onset and withdrawal transitional CLIMATE zone different types of ENSO
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部