期刊文献+
共找到48,789篇文章
< 1 2 250 >
每页显示 20 50 100
英汉文化动物词对比 被引量:169
1
作者 廖光蓉 《外国语》 CSSCI 北大核心 2000年第5期17-26,共10页
文化制约了动物词的意义演变而动物词的文化意义又折射出了丰富的文化内容由于文化内容文化传统和文化心理有异很多英汉文化动物词意义上差异较大容易造成理解和表达上的错误本文试图就以下几个带方向性的问题进行对比与分析文化动物词... 文化制约了动物词的意义演变而动物词的文化意义又折射出了丰富的文化内容由于文化内容文化传统和文化心理有异很多英汉文化动物词意义上差异较大容易造成理解和表达上的错误本文试图就以下几个带方向性的问题进行对比与分析文化动物词的总数各类动物词中文化动物词的数量多义文化动物词的数量文化意义类型及其文化成因并就如何对比与分析给出了范例 展开更多
关键词 动物词 英汉文化 文化内容 多义 对比 文化制约 词意 文化意义 文化成因 文化心理
全文增补中
On adjacent-vertex-distinguishing total coloring of graphs 被引量:175
2
作者 ZHANG Zhongfu, CHEN Xiang’en, LI Jingwen, YAO Bing, LU Xinzhong & WANG Jianfang College of Mathematics and Information Science, Northwest Normal University, Lanzhou 730070, China Department of Computer, Lanzhou Normal College, Lanzhou 730070, China +2 位作者 Institute of Applied Mathematics, Lanzhou Jiaotong University, Lanzhou 730070, China College of Information and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China Institute of Applied Mathematics, Chinese Academy of Sciences, Beijing 100080, China 《Science China Mathematics》 SCIE 2005年第3期289-299,共11页
In this paper, we present a new concept of the adjacent-vertex-distinguishing total coloring of graphs (briefly, AVDTC of graphs) and, meanwhile, have obtained the adjacent-vertex-distinguishing total chromatic number... In this paper, we present a new concept of the adjacent-vertex-distinguishing total coloring of graphs (briefly, AVDTC of graphs) and, meanwhile, have obtained the adjacent-vertex-distinguishing total chromatic number of some graphs such as cycle, complete graph, complete bipartite graph, fan, wheel and tree. 展开更多
关键词 graph PROPER TOTAL coloring adjacent-vertex-distinguishing TOTAL coloring adjacent-vertex-distinguishing TOTAL CHROMATIC number.
原文传递
立体车库发展的现状与挑战 被引量:107
3
作者 付翠玉 关景泰 《机械设计与制造》 北大核心 2005年第9期156-157,共2页
立体车库可以在很大程度上解决中国停车拥挤现状,但是立体车库在现实发展中还有许多发展限制因素。这里介绍了立体车库发展的挫折与机遇。
关键词 保有量 停车难 立体车库 改善
下载PDF
China's lakes at present:Number,area and spatial distribution 被引量:92
4
作者 MA RongHua YANG GuiShan +8 位作者 DUAN HongTao JIANG JiaHu WANG SuMin FENG XueZhi LI AiNong KONG FanXiang XUE Bin WU JingLu LI ShiJie 《Science China Earth Sciences》 SCIE EI CAS 2011年第2期283-289,共7页
Based on 11004 satellite images from CBERS CCD and Landsat TM/ETM,changes in the spatial characteristics of all lakes in China were determined following pre-established interpretation rules.This dataset was supported ... Based on 11004 satellite images from CBERS CCD and Landsat TM/ETM,changes in the spatial characteristics of all lakes in China were determined following pre-established interpretation rules.This dataset was supported by 6843 digital raster images(1:100000 and 1:50000),a countrywide digital vector dataset(1:250000),and historical literature.Comparative data were corrected for seasonal variations using precipitation data.There are presently 2693 natural lakes in China with an area greater than 1.0 km2,excluding reservoirs.These lakes are distributed in 28 provinces,autonomous regions and municipalities and have a total area of 81414.6 km2,accounting for-0.9% of China's total land area.In the past 30 years,the number of newly formed and newly discovered lakes with an area greater than 1.0 km2 is 60 and 131,respectively.Conversely,243 lakes have disappeared in this time period. 展开更多
关键词 China lake number lake area spatial distribution
原文传递
数据革命:从数到大数据的历史考察 被引量:74
5
作者 刘红 胡新和 《自然辩证法通讯》 CSSCI 北大核心 2013年第6期33-39,125-126,共7页
考察了数到大数据的历史演变进程,提出数据的发展可划分为三个阶段,即数的产生、科学数据的形成和大数据的诞生。数据的演变历程不仅显示出在其内涵和形式上发生了革命性的变化,而且引发了人类认识客观世界和社会管理的方法变革。指出,... 考察了数到大数据的历史演变进程,提出数据的发展可划分为三个阶段,即数的产生、科学数据的形成和大数据的诞生。数据的演变历程不仅显示出在其内涵和形式上发生了革命性的变化,而且引发了人类认识客观世界和社会管理的方法变革。指出,数据具有先天的精确性和实用性特征;计算方法与信息技术发展的结果必然导致大数据的诞生;数据的发展引致两次革命,即始于数据与自然哲学融合的第一次数据革命,展示了数据的基础性和依据性特征;第二次数据革命以大数据为标志,使万物皆数的理念成为现实。另外,数据使社会、经济、教育、文化、科技等领域的认识论和方法论发生了变革,其资源性的特征正在逐渐显露出来。 展开更多
关键词 数据 科学数据 大数据 数据革命
原文传递
An updated estimation of the risk of transmission of the novel coronavirus(2019-nCov) 被引量:67
6
作者 Biao Tang Nicola Luigi Bragazzi +3 位作者 Qian Li Sanyi Tang Yanni Xiao Jianhong Wu 《Infectious Disease Modelling》 2020年第1期248-255,共8页
The basic reproduction number of an infectious agent is the average number of infections one case can generate over the course of the infectious period,in a naïve,uninfected population.It is well-known that the e... The basic reproduction number of an infectious agent is the average number of infections one case can generate over the course of the infectious period,in a naïve,uninfected population.It is well-known that the estimation of this number may vary due to several methodological issues,including different assumptions and choice of parameters,utilized models,used datasets and estimation period.With the spreading of the novel coronavirus(2019-nCoV)infection,the reproduction number has been found to vary,reflecting the dynamics of transmission of the coronavirus outbreak as well as the case reporting rate.Due to significant variations in the control strategies,which have been changing over time,and thanks to the introduction of detection technologies that have been rapidly improved,enabling to shorten the time from infection/symptoms onset to diagnosis,leading to faster confirmation of the new coronavirus cases,our previous estimations on the transmission risk of the 2019-nCoV need to be revised.By using time-dependent contact and diagnose rates,we refit our previously proposed dynamics transmission model to the data available until January 29th,2020 and re-estimated the effective daily reproduction ratio that better quantifies the evolution of the interventions.We estimated when the effective daily reproduction ratio has fallen below 1 and when the epidemics will peak.Our updated findings suggest that the best measure is persistent and strict self-isolation.The epidemics will continue to grow,and can peak soon with the peak time depending highly on the public health interventions practically implemented. 展开更多
关键词 Novel coronavirus Emerging and reemerging pathogens Mathematical modeling Basic reproduction number Effective daily reproduction ratio
原文传递
D(β)-vertex-distinguishing total coloring of graphs 被引量:55
7
作者 ZHANG Zhongfu,LI Jingwen,CHEN Xiang’en,YAO Bing, WANG Wenjie & QIU Pengxiang Institute of Applied Mathematic, Lanzhou Jiaotong University, Lanzhou 730070, China College of Mathematics and Information Science, Northwest Normal University, Lanzhou 730070, China College of Information and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China 《Science China Mathematics》 SCIE 2006年第10期1430-1440,共11页
A new concept of the D(β)-vertex-distinguishing total coloring of graphs, i.e., the proper total coloring such that any two vertices whose distance is not larger than β have different color sets, where the color set... A new concept of the D(β)-vertex-distinguishing total coloring of graphs, i.e., the proper total coloring such that any two vertices whose distance is not larger than β have different color sets, where the color set of a vertex is the set composed of all colors of the vertex and the edges incident to it, is proposed in this paper. The D(2)-vertex-distinguishing total colorings of some special graphs are discussed, meanwhile, a conjecture and an open problem are presented. 展开更多
关键词 graph TOTAL coloring D(β)-vertex-distinguishing TOTAL coloring D(β)-vertexdistinguishing TOTAL CHROMATIC number.
原文传递
Principle of equipartition of entransy dissipation for heat exchanger design 被引量:46
8
作者 GUO JiangFeng,XU MingTian & CHENG Lin Institute of Thermal Science and Technology,Shandong University,Jinan 250061,China 《Science China(Technological Sciences)》 SCIE EI CAS 2010年第5期1309-1314,共6页
In the present work,a principle of equipartition of entransy dissipation(EoED) for heat exchanger design is established,which says that for a heat exchanger design with given heat duty and heat transfer area,the total... In the present work,a principle of equipartition of entransy dissipation(EoED) for heat exchanger design is established,which says that for a heat exchanger design with given heat duty and heat transfer area,the total entransy dissipation rate reaches the minimum when the local entransy dissipation rate is uniformly distributed along the heat exchanger.When the heat transfer coefficient is unfixed,the total entransy dissipation obtained by the EoED principle is less than that obtained by the principle of equipartition of temperature difference(EoTD).Furthermore,the exchanger effectiveness obtained by the EoED principle is larger than that obtained by the EoTD principle.When the heat transfer coefficient is fixed,the EoED principle is equivalent to the EoTD principle.We show that the equipartition of entropy production(EoEP) and EoED principles give rise to difference in entropy generation and entransy dissipation for a heat exchanger optimization design.The discrepancies are caused by distinct features of entropy production minimization and entransy dissipation minimization principles,the former is to optimize the design of heat exchanger by making the lost available work minimum,while the latter is not involved with heat-work conversion.It is found that the entropy generation number is not suitable for evaluating heat exchanger performance,since it directly depends on the inlet and outlet temperatures of working fluids.On the contrary,the entransy dissipation number is not directly related to the inlet and outlet temperatures of working fluids.Therefore,the entransy dissipation number is more suitable for serving as a criterion to evaluate heat exchanger performance. 展开更多
关键词 heat EXCHANGER ENTROPY production ENTROPY generation number entransy DISSIPATION entransy DISSIPATION number
原文传递
A mathematical model for simulating the phase-based transmissibility of a novel coronavirus 被引量:49
9
作者 Tian-Mu Chen Jia Rui +3 位作者 Qiu-Peng Wang Ze-Yu Zhao Jing-An Cui Ling Yin 《Infectious Diseases of Poverty》 SCIE 2020年第1期18-25,共8页
Background:As reported by the World Health Organization,a novel coronavirus(2019-nCoV)was identified as the causative virus of Wuhan pneumonia of unknown etiology by Chinese authorities on 7 January,2020.The virus was... Background:As reported by the World Health Organization,a novel coronavirus(2019-nCoV)was identified as the causative virus of Wuhan pneumonia of unknown etiology by Chinese authorities on 7 January,2020.The virus was named as severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)by International Committee on Taxonomy of Viruses on 11 February,2020.This study aimed to develop a mathematical model for calculating the transmissibility of the virus.Methods:In this study,we developed a Bats-Hosts-Reservoir-People transmission network model for simulating the potential transmission from the infection source(probably be bats)to the human infection.Since the Bats-HostsReservoir network was hard to explore clearly and public concerns were focusing on the transmission from Huanan Seafood Wholesale Market(reservoir)to people,we simplified the model as Reservoir-People(RP)transmission network model.The next generation matrix approach was adopted to calculate the basic reproduction number(R0)from the RP model to assess the transmissibility of the SARS-CoV-2.Results:The value of R0 was estimated of 2.30 from reservoir to person and 3.58 from person to person which means that the expected number of secondary infections that result from introducing a single infected individual into an otherwise susceptible population was 3.58.Conclusions:Our model showed that the transmissibility of SARS-CoV-2 was higher than the Middle East respiratory syndrome in the Middle East countries,similar to severe acute respiratory syndrome,but lower than MERS in the Republic of Korea. 展开更多
关键词 Novel coronavirus Mathematical model Basic reproduction number Next generation matrix TRANSMISSIBILITY
原文传递
恩诺沙星残留对土壤微生物数量及群落功能多样性的影响 被引量:45
10
作者 王加龙 刘坚真 +1 位作者 陈杖榴 陈林 《应用与环境生物学报》 CAS CSCD 北大核心 2005年第1期86-89,共4页
对不同浓度恩诺沙星作用于土壤后三大类微生物数量及群落功能多样性进行了研究. 结果表明,恩诺沙星残留对它们影响强弱顺序为:细菌>放线菌>真菌,其影响作用随浓度从每克土0.01 μg至10 μg的增加而加大,药物作用活性维持期为6~8... 对不同浓度恩诺沙星作用于土壤后三大类微生物数量及群落功能多样性进行了研究. 结果表明,恩诺沙星残留对它们影响强弱顺序为:细菌>放线菌>真菌,其影响作用随浓度从每克土0.01 μg至10 μg的增加而加大,药物作用活性维持期为6~8 d,但对真菌作用不明显. 相对较低浓度的恩诺沙星残留(每克土中0.1 μg,1 μg)不影响土壤微生物群落功能多样性,而相对较高浓度的恩诺沙星残留(每克土中10 μg)则降低了其微生物群落功能多样性. 图2 表2 展开更多
关键词 恩诺沙星残留 土壤微生物 数量 群落多样性
下载PDF
Effects of resource additions on species richness and ANPP in an alpine meadow community 被引量:44
11
作者 Zhengwei Ren Qi Li +5 位作者 Chengjin Chu Luqiang Zhao Jieqi Zhang Dexiecuo Ai Yingbo Yang Gang Wang 《Journal of Plant Ecology》 SCIE 2010年第1期25-31,共7页
Aims Theories based on resource additions indicate that plant species richness is mainly determined by the number of limiting resources.However,the individual effects of various limiting resources on species richness ... Aims Theories based on resource additions indicate that plant species richness is mainly determined by the number of limiting resources.However,the individual effects of various limiting resources on species richness and aboveground net primary productivity(ANPP)are less well understood.Here,we analyzed potential linkages between additions of limiting resources,species loss and ANPP increase and further explored the underlying mechanisms.Methods Resources(N,P,K and water)were added in a completely randomized block design to alpine meadow plots in the Qinghai-Tibetan Plateau.Plant aboveground biomass,species composition,mean plant height and light availability were measured in each plot.Regression and analysis of variance were used to analyze the responses of these measures to the different resource-addition treatments.Important Findings Species richness decreased with increasing number of added limiting resources,suggesting that plant diversity was apparently determined by the number of limiting resources.Nitrogen was the most important limiting resource affecting species richness,whereas Pand K alone had negligible effects.The largest reduction in species richness occurred when all three elements were added in combination.Water played a different role compared with the other limiting resources.Species richness increased when water was added to the treatments with N and P or with N,P and K.The decreases in species richness after resource additions were paralleled by increases in ANPP and decreases in light penetration into the plant canopy,suggesting that increased light competitionwas responsible for the negative effects of resource additions on plant species richness. 展开更多
关键词 ANPP BIODIVERSITY resource additions species richness number of limiting resources
原文传递
Relationship Between Grain Yield and Yield Components in Super Hybrid Rice 被引量:41
12
作者 HUANG Min ZOU Ying-bin JIANG Peng XIA Bing Md Ibrahim AO He-jun 《Agricultural Sciences in China》 CAS CSCD 2011年第10期1537-1544,共8页
Chinese super hybrid rice breeding project has developed many new varieties with great yield potential. It is controversial which yield component should be emphasized in super hybrid rice production. The present study... Chinese super hybrid rice breeding project has developed many new varieties with great yield potential. It is controversial which yield component should be emphasized in super hybrid rice production. The present study was conducted to compare super hybrid rice with common hybrid and super inbred rice and analyze contributions of yield components to grain yield of super hybrid rice under experimental conditions, and evaluate relationships between grain yield and yield components of super hybrid rice in farmer’s paddy fields. Field experiments were done in Changsha, Guidong, and Nanxian, Hunan Province, China, from 2007 to 2009. Eight super hybrid varieties, one common hybrid variety, and one super inbred variety were grown in each location and year. Rice production investigation was undertaken in high-yielding (Guidong), moderate-yielding (Nanxian), and low-yielding (Ningxiang) regions of Hunan Province, China, in 2009. Grain yield and yield components were measured in both the field experiments and rice production investigation. Super hybrid rice varieties outyielded common hybrid and super inbred varieties across three locations and years. Yield potential has been increased by 11.4% in super hybrid rice varieties compared with common and super inbred varieties. The higher yield of super hybrid varieties was attributed to improvement in panicle size. Panicles per m2 had the highest positive contribution to grain yield with the exception under yield level of 10.0 to 12.0 t ha-1, and was positively related to grain yield in farmer’s field at all of the high-, moderate-, and low-yielding regions. Our study suggests that panicle per m2 ought to be emphasized in super hybrid rice production. 展开更多
关键词 super hybrid rice YIELD panicle number panicle size
下载PDF
小学语文课本阅读量的现状与思考 被引量:41
13
作者 王贺玲 《河北师范大学学报(教育科学版)》 CSSCI 北大核心 2011年第12期76-81,共6页
对五套小学语文课本进行阅读量的现状考量,以不同时期人民教育出版社出版的课本,以及课程标准下北师大版、江苏版课本,进行纵向和横向比较研究。对五套课本的课文数、印张数作数据统计,对不同年段阅读量以及语言积累量的数值分布作比较... 对五套小学语文课本进行阅读量的现状考量,以不同时期人民教育出版社出版的课本,以及课程标准下北师大版、江苏版课本,进行纵向和横向比较研究。对五套课本的课文数、印张数作数据统计,对不同年段阅读量以及语言积累量的数值分布作比较分析,对课文编制内容类别与形式变化作进一步分析研究。在探究形成课文数递增变化的外在因素与内在因素的基础上,对内地版小学语文课本阅读量的现状进行思考,并提出课本阅读量的相对合理参考值。对小学语文课本的编写与修订具有参考价值,对教材的研究开扩了新的视角和空间。 展开更多
关键词 小学语文课本 阅读量 课文数 年段阅读量
下载PDF
我国全科医生数量和分布现状及需要量预测研究 被引量:40
14
作者 伍宝玲 龚韩湘 罗桢妮 《中国全科医学》 CAS 北大核心 2018年第1期13-17,共5页
目的了解我国全科医生数量和分布现状,并预测其未来需要量。方法以《2014中国卫生和计划生育统计年鉴》、《2016中国卫生和计划生育统计年鉴》以及《2016中国统计年鉴》为资料来源,收集2012—2015年我国及各地区全科医生数量和人口数。... 目的了解我国全科医生数量和分布现状,并预测其未来需要量。方法以《2014中国卫生和计划生育统计年鉴》、《2016中国卫生和计划生育统计年鉴》以及《2016中国统计年鉴》为资料来源,收集2012—2015年我国及各地区全科医生数量和人口数。采用SPSS 22.0统计软件进行描述性统计分析,采用灰色数列模型[GM(1,1)]模型以及人力人口比值法对2016—2020年我国全科医生的未来需要量进行预测。结果 2012—2015年,我国全科医生数量分别为109 794、145 511、172 597、188 649名,增长了78 855名,年均增长率为19.77%。截至2015年底,我国全国、东部、中部、西部地区取得全科医生培训合格证书的全科医生分别占63.76%(120 285/188 649)、60.06%(62 474/104 015)、65.20%(29 565/45 344)、71.89%(28 246/39 290);我国全国、东部、中部、西部地区每万人口拥有的全科医生数分别为1.37、1.83、1.05、1.06名,按2名全科医生/万人配置标准全科医生缺口数分别为86 275、9 787、40 764、34 976名。GM(1,1)模型预测,2016—2020年,按照自然增长趋势我国全科医生总数分别为220 314、253 728、293 101、339 928、396 228名。按照每万人口拥有2~3名全科医生的标准,人力人口比值法计算结果显示,预测我国2020年的全科医生总数为277 000~415 500名。结论近年来我国全科医生数增长较快,但普遍缺口较大,分布不均衡,合格全科医生比例也不高,应加强全科医生队伍建设力度,完善全科医生培养体系。 展开更多
关键词 全科医生 数量 分布 预测
下载PDF
Kinematics and dynamics of the Mesozoic orogeny and late-orogenic extensional collapse in the Sino-Mongolian border areas 被引量:38
15
作者 ZHENG Yadong 1 & WANG Tao2 1. Key Laboratory of Orogenic Belts and Crustal Evolution (Peking University), Ministry of Education, Beijing 100871, China 2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China 《Science China Earth Sciences》 SCIE EI CAS 2005年第7期849-862,共14页
The Sino-Mongolian border areas underwent two important tectonic events during Mesozoic time after late Paleozoic orogeny: a late Triassic to earlier Jurassic contractional event that resulted in a large-scale south-v... The Sino-Mongolian border areas underwent two important tectonic events during Mesozoic time after late Paleozoic orogeny: a late Triassic to earlier Jurassic contractional event that resulted in a large-scale south-vergent thrust during the orogeny and a late Jurassic-earlier Cretaceous extensional event in a north-south direction that formed a metamorphic core complex. The kinematic and dynamic analyses show that the thrust sheet moved southwards with a kinematic vorticity number of ca. -0.10 and sub-horizontal maximum compressive stress axis that belongs to a contraction-thickening shear. The upper plate of the late-orogenic detachment relatively moved in a 165°direction. The average kinematic vorticity in its earlier stage was 0.74 that belongs to simple shear dominated shearing and related to the maximum compressive stress axes dipping at ~66°, while the later average kinematic vorticity was ~0.55°that belongs to pure shear dominated shearing with sub-vertical maximum compressive stress axes. This suggests that the thrusting led to the crust thickened and the lower plate rocks that were originally located in the upper crust depressed through a brittle-ductile transition zone into the lower crust and became warmer. The heated rocks trended to uplift since their increasing volume and decreasing density while the loading of the upper-plate rocks increased due to the structural thickening. Under the combined effect of the loading and the thermal-uplifting, the ductile shear zone in between increased in its component of vertical pure shear. Once its pure-shear component exceeded its simple-shear one the ductile shear zone became an extension-thinned shear zone. This progressive transitional process reflects internal and essential temporal and spatial relationships: the extensional factor nucleated during the crust thickening by thrusting and increase of the extensional factor finally led to late-orogenic collapse. 展开更多
关键词 MESOZOIC thrusting late-orogenic collapse kinematic VORTICITY number stress state.
原文传递
农村剩余劳动力的新估计及其含义 被引量:37
16
作者 都阳 王美艳 《广州大学学报(社会科学版)》 2010年第4期17-24,共8页
利用具有全国代表性的抽样调查资料,测算农村劳动力资源的配置状况,并根据计量经济模型,预测样本中每一个劳动力的迁移概率。由此推算出在现有的劳动力市场状况和制度环境下,农业中可供转移的劳动力规模仅有几千万,是十分有限的,这一结... 利用具有全国代表性的抽样调查资料,测算农村劳动力资源的配置状况,并根据计量经济模型,预测样本中每一个劳动力的迁移概率。由此推算出在现有的劳动力市场状况和制度环境下,农业中可供转移的劳动力规模仅有几千万,是十分有限的,这一结果和中国仍然存在上亿的、大量的农村剩余劳动力的观点有很大差异。目前在农业部门就业的劳动力主要是受教育水平较低的中老年劳动力,要使他们真正为经济的持续发展发挥作用,需要相应的政策支持,即重视对中老年劳动力的培训,降低劳动力流动的成本,从而提高其非农工作的参与程度。 展开更多
关键词 农村劳动力 配置 外出 剩余劳动力 数量 政策
下载PDF
Twenty years of Chinese vascular plant novelties,2000 through 2019 被引量:34
17
作者 Cheng Du Shuai Liao +1 位作者 David E.Boufford Jinshuang Ma 《Plant Diversity》 SCIE CAS CSCD 2020年第5期393-398,共6页
From 2000 to 2019,11,895 new names or new additions to the Chinese vascular flora were proposed by 4226 individuals(4086 articles and 140 books),as documented in the Chinese Plant Names Index(CPNI).During those 20 yea... From 2000 to 2019,11,895 new names or new additions to the Chinese vascular flora were proposed by 4226 individuals(4086 articles and 140 books),as documented in the Chinese Plant Names Index(CPNI).During those 20 years,4407 new taxa of vascular plants were described from China,including 7 new families,132 new genera,3543 new species,68 new subspecies,497 new varieties and 160 new forms.Additionally,3562 new combinations and names at new rank and 306 new replacement names were also proposed.Among these various new names were 150 invalid names and 108 illegitimate names,including some that have not been resolved.Six hundred and forty three vascular plants were reported as new to China,while 2349 names were reduced to synonyms of 1406 taxa.The data show that the Chinese flora increased in size at the rate of about 200 taxa annually during those years.Despite the increased attention given to biodiversity in recent years,the evidence indicates that a large number of species in China have yet to be discovered.Further basic investigation of the Chinese flora is needed.Additionally,in the past two decades only 8.5%of the newly published species have been based on molecular evidence,but in the past five years such data have increased significantly,reaching about 20%.Molecular data will undoubtedly become increasingly significant in the discovery of new species in the coming years.Yunnan,Guangxi,Sichuan,Xizang and Taiwan were important sources of new discoveries,with more than 3300 new taxa and records from these five provinces.By area,Taiwan and Hainan,two islands in southern China,have the highest density of newly discovered species.Regional plant surveys are still needed,especially in areas in the southwest and on the southern islands. 展开更多
关键词 Novelties of Chinese vascular plants number of new taxa number of new name changes Authors of new taxa
下载PDF
香港古树名木的调查及保护问题 被引量:34
18
作者 刘东明 王发国 +3 位作者 陈红锋 易绮斐 曾庆文 邢福武 《生态环境》 CSCD 北大核心 2008年第4期1560-1565,共6页
采用实地调查并结合历史档案记载的方法对香港的古树名木进行了全面的普查,在香港193个地点调查到有古树分布,记录古树名木1332株,共计141种,隶属于46科95属。其中细叶榕Ficus microcarpa323株、樟树Cinnamomum camphora157株、荔枝Litc... 采用实地调查并结合历史档案记载的方法对香港的古树名木进行了全面的普查,在香港193个地点调查到有古树分布,记录古树名木1332株,共计141种,隶属于46科95属。其中细叶榕Ficus microcarpa323株、樟树Cinnamomum camphora157株、荔枝Litchi chinensis118株、龙眼Dimocarpus longan97株,4种古树株数之和超过香港古树名木总数的一半。香港古树主要分布在大埔区、中西区、北区和离岛区,四个区所含株数占古树总株数的60.66%,所含古树种数占香港古树总种数的78.72%。在香港116处风水林中,86处记录有古树分布,古树数量占调查到的古树数量的近50%。根据调查的结果,还对香港古树名木的保护措施进行了分析研究,旨在为其保育提供参考。 展开更多
关键词 香港古树名木 种类 数量 分布
下载PDF
几种常见鲤科养殖鱼类肌间刺的初步研究 被引量:34
19
作者 董在杰 黄代中 +5 位作者 李丽娟 袁新华 缪为民 陈奇渠 陆志兵 张炳良 《上海水产大学学报》 CSCD 北大核心 2006年第4期425-429,共5页
对鲢、鳙、团头鲂和异育银鲫肌间刺的数目、形态和分布进行分析研究,结果显示:鲢的肌间刺数目在117~124之间,鳙的肌间刺数目在116~133之间,团头鲂的肌间刺数目在114~129之间,异育银鲫的肌间刺数目在79~87之间。每条鱼左右两侧... 对鲢、鳙、团头鲂和异育银鲫肌间刺的数目、形态和分布进行分析研究,结果显示:鲢的肌间刺数目在117~124之间,鳙的肌间刺数目在116~133之间,团头鲂的肌间刺数目在114~129之间,异育银鲫的肌间刺数目在79~87之间。每条鱼左右两侧的肌间刺数目不完全相等,但总体上两侧肌间刺的数目接近。不同部位的肌间刺数目也有差异:躯干部轴上肌中的肌间刺数目最多,尾部轴上肌与轴下肌中的肌间刺数目基本相等。鲢、鳙、鲫和团头鲂的肌间刺形态都在10种以上。这几种鱼每条鱼的躯干部轴上肌中都有一根很细很短的“l”形刺,这根最短刺的长度在不同规格的鱼上差别并不大。 展开更多
关键词 鲤科鱼类 肌间刺 形态 数目 分布
下载PDF
鄱阳湖沙湖越冬白鹤的数量分布及其与食物和水深的关系 被引量:33
20
作者 吴建东 李凤山 James Burnham 《湿地科学》 CSCD 北大核心 2013年第3期305-312,共8页
为了摸清白鹤(Grus leucogeranus)的食物刺苦草(Vallisneria spinulosa)的资源状况和水深对白鹤活动的影响,于1999~2010年期间,对在鄱阳湖国家级自然保护区沙湖越冬的白鹤数量分布及其与食物刺苦草块茎和水深的关系进行了研究。... 为了摸清白鹤(Grus leucogeranus)的食物刺苦草(Vallisneria spinulosa)的资源状况和水深对白鹤活动的影响,于1999~2010年期间,对在鄱阳湖国家级自然保护区沙湖越冬的白鹤数量分布及其与食物刺苦草块茎和水深的关系进行了研究。在沙湖设置固定植物样线,每隔50~100m记录刺苦草及其块茎的数量和生物量,在视野能覆盖整个沙湖的制高点,定点观测白鹤的数量、分布和白鹤所处的水深。在这12a越冬期间,沙湖白鹤的多年总平均数量为46只,其中2002年、2006年和2009年冬季超过90只。11月至翌年1月是白鹤在沙湖比较稳定的时期,超过50只,其中12月是白鹤数量最多的月份,达到120只。白鹤在沙湖的中部偏南地带活动,北部和南端的数量很少。从栖息的植被带来看,白鹤几乎全部在以苦草(Vallisneria spp.)和眼子菜(Potamogeton spp.)为优势沉水植物的区域活动。沙湖刺苦草块茎的平均干重为5.92g/m2,2005年、2006年和2008年的干重接近或者超过12g/m2,2010年最少,仅为0.10g/m2。在1999-2010年期间,沙湖白鹤数量与刺苦草块茎干重不相关,隆冬12月至翌年1月的白鹤平均数量与刺苦草块茎干重的相关系数为r=0.231。在沙湖,有58.15%的白鹤在水深为5~27cm的环境中活动;其次,有30.63%的白鹤是在水深为40-45cm的环境中活动。而没有白鹤在旱地和水深及至腹部(46-50cm)的环境中活动。2010年鄱阳湖特大洪水对白鹤的影响比较大,发现有白鹤到草地上觅食的现象。 展开更多
关键词 白鹤 数量 食物 刺苦草 水深 鄱阳湖 沙湖
原文传递
上一页 1 2 250 下一页 到第
使用帮助 返回顶部