期刊文献+
共找到6,914篇文章
< 1 2 250 >
每页显示 20 50 100
Solid pseudopapillary tumor of the pancreas:A review of 553 cases in Chinese literature 被引量:124
1
作者 Yu, Peng-Fei Hu, Zhen-Hua +4 位作者 Wang, Xin-Bao Guo, Jian-Min cheng, xiang-Dong Zhang, Yun-Li Xu, Qi 《World Journal of Gastroenterology》 SCIE CAS CSCD 2010年第10期1209-1214,共6页
AIM:To sum up the clinical and pathological characte- ristics of solid pseudopapillary tumor (SPT) and the experience with it.METHODS: A total of 553 SPT patients reported in Chinese literature between January 1996 an... AIM:To sum up the clinical and pathological characte- ristics of solid pseudopapillary tumor (SPT) and the experience with it.METHODS: A total of 553 SPT patients reported in Chinese literature between January 1996 and January 2009 were retrospectively reviewed and analyzed. RESULTS: The mean age of the 553 SPT patients included in this review was 27.2 years, and the male to female ratio was 1:8.37. Their symptoms were non-specific, and nearly one third of the patients were asymptomatic. Computed tomography and ultraso-nography were performed to show the nature and location of SPT. Most of the tumors were distributed in the pancreatic head (39.8%), tail (24.1%), body andtail (19.5%). Forty-five patients (9.2%) were diagnosed as malignant SPT with metastasis or invasion. None of the clinical factors was closely related to the malignant potential of SPT. Surgery was the main therapeutic modality for SPT. Local resection, distal pancreatectomy and pancreatoduodenectomy were the most common surgical procedures. Local recurrence and hepatic metastasis were found in 11 and 2 patients, respectively, after radical resection. Four patients died of tumor progression within 4 years after palliative resection of SPT. The prognosis of SPT patients was good with a 5-year survival rate of 96.9%.CONCLUSION: SPT of the pancreas is a rare indolent neoplasm that typically occurs in young females. It is a low-grade malignancy and can be cured with extended resection. The prognosis of such patients is good although the tumor may recur and metastasize. 展开更多
关键词 Pancreatic neoplasm Solid pseudopapillary tumor DIAGNOSIS TREATMENT PROGNOSIS
下载PDF
舒张性心力衰竭诊断和治疗专家共识 被引量:110
2
作者 廖玉华 杨杰孚 +8 位作者 张健 程翔 谢明星 李新立 董吁钢 周京敏 伍伟锋 郭小梅 《临床心血管病杂志》 CAS 北大核心 2020年第1期1-10,共10页
心力衰竭(心衰)是一种异质性很强的复杂临床综合征,根据左室射血分数对心衰进行分类简便易行,但存在局限性。收缩性心衰(SHF)与舒张性心衰(DHF)病理生理机制不同,SHF应用神经激素拮抗剂治疗显著获益,DHF病理生理机制涉及系统性炎症、代... 心力衰竭(心衰)是一种异质性很强的复杂临床综合征,根据左室射血分数对心衰进行分类简便易行,但存在局限性。收缩性心衰(SHF)与舒张性心衰(DHF)病理生理机制不同,SHF应用神经激素拮抗剂治疗显著获益,DHF病理生理机制涉及系统性炎症、代谢紊乱、心外膜脂肪组织堆积、心肌微血管功能障碍、心肌纤维化等,DHF的有效治疗尚未明确。DHF诊断建议采用超声心动图提出的心功能诊断标准。目前DHF治疗策略包括对症治疗、探索性抗炎症和抗代谢药物治疗。为了减少心衰再住院率,神经激素拮抗剂适用于大多数SHF合并DHF患者的治疗。 展开更多
关键词 舒张性心力衰竭 病理生理 诊断 治疗
原文传递
三相不平衡及谐波对三相四线低压配电网线损的影响 被引量:57
3
作者 谢荣斌 杜帆 +2 位作者 程湘 周群 徐方维 《电力系统保护与控制》 EI CSCD 北大核心 2020年第21期22-30,共9页
针对三相四线制低压配电网中的线损问题,提出了在复合电能质量作用下的线损计算方法以及与单一电能质量作用下的线损比较方法。首先对三相不平衡引起的线损进行推导;其次依据叠加原理推导谐波条件下的线损;然后综合考虑和推导这两种电... 针对三相四线制低压配电网中的线损问题,提出了在复合电能质量作用下的线损计算方法以及与单一电能质量作用下的线损比较方法。首先对三相不平衡引起的线损进行推导;其次依据叠加原理推导谐波条件下的线损;然后综合考虑和推导这两种电能质量共同作用下的线损,并根据对称分量法对这两种电能质量在单独与共同作用下的线损进行比较。结果表明三相不平衡加剧谐波损耗,即谐波及三相不平衡共同存在时的线损大于各自单独存在时造成的线损之和。最后利用Matlab/Simulink仿真工具和chroma 6590可编程交流电源对每一部分均进行实验,验证了理论推导的正确性。 展开更多
关键词 谐波 三相不平衡 线损 MATLAB/SIMULINK chroma 6590可编程交流电源
下载PDF
Lipid metabolism reprogramming and its potential targets in cancer 被引量:52
4
作者 Chunming cheng Feng Geng +1 位作者 xiang cheng Deliang Guo 《Cancer Communications》 SCIE 2018年第1期291-304,共14页
Reprogramming of lipid metabolism is a newly recognized hallmark of malignancy.Increased lipid uptake,storage and lipogenesis occur in a variety of cancers and contribute to rapid tumor growth.Lipids constitute the ba... Reprogramming of lipid metabolism is a newly recognized hallmark of malignancy.Increased lipid uptake,storage and lipogenesis occur in a variety of cancers and contribute to rapid tumor growth.Lipids constitute the basic struc-ture of membranes and also function as signaling molecules and energy sources.Sterol regulatory element-binding proteins(SREBPs),a family of membrane-bound transcription factors in the endoplasmic reticulum,play a central role in the regulation of lipid metabolism.Recent studies have revealed that SREBPs are highly up-regulated in various cancers and promote tumor growth.SREBP cleavage-activating protein is a key transporter in the trafficking and activation of SREBPs as well as a critical glucose sensor,thus linking glucose metabolism and de novo lipid synthesis.Targeting altered lipid metabolic pathways has become a promising anti-cancer strategy.This review summarizes recent progress in our understanding of lipid metabolism regulation in malignancy,and highlights potential molecu-lar targets and their inhibitors for cancer treatment. 展开更多
关键词 Lipid metabolism CANCER SCAP SREBPs Fatty acids CHOLESTEROL Lipid droplets
原文传递
新型冠状病毒肺炎防控形势下急性心肌梗死诊治流程和路径的中国专家共识(第1版) 被引量:43
5
作者 卜军 陈茂 +39 位作者 程晓曙 董一飞 方唯一 葛均波 龚艳君 何奔 黄岚 霍勇 贾绍斌 蒋峻 李悦 李昭 梁春 刘学波 刘震宇 马翔 马依彤 钱菊英 沈成兴 沈涤非 沈雳 石瑞正 苏晞 孙英贤 唐熠达 王建安 吴岳 向定成 徐通达 徐亚伟 杨跃进 曾和松 张澄 张国刚 张瑞岩 张书宁 张运 张钲 郑博 周宁 《南方医科大学学报》 CAS CSCD 北大核心 2020年第2期147-151,共5页
自2019年12月以来,新型冠状病毒肺炎在武汉感染流行并迅速蔓延全国各地,根据国家整体防控方案,绝大部分地区启动限制出入、限制交通等措施。此特殊形势对于急性心肌梗死患者的转运救治流程提出了新的要求。急性心肌梗死发病急、致死性... 自2019年12月以来,新型冠状病毒肺炎在武汉感染流行并迅速蔓延全国各地,根据国家整体防控方案,绝大部分地区启动限制出入、限制交通等措施。此特殊形势对于急性心肌梗死患者的转运救治流程提出了新的要求。急性心肌梗死发病急、致死性高、最佳救治窗口期短、且容易合并呼吸系统感染及呼吸、循环衰竭,更加需要就地积极治疗。为规范管理、易化流程,现制定急性心肌梗死诊治流程和路径策略,其核心是就近原则、安全防护原则、溶栓优先原则、定点转运原则、远程会诊原则。对于急性心梗患者,应排查新型冠状病毒肺炎,针对发病时间窗,选择不同的治疗策略。在这一特殊时期,包括介入医师在内的心血管医生都应掌握溶栓的禁忌症和适应证。在急性心肌梗死患者的转运和治疗中,应严格掌握转运及手术指征,严格按照要求对感染者及医务工作者进行防护。 展开更多
关键词 新冠肺炎 心肌梗死 防护 转运 溶栓
下载PDF
区域经济高质量发展与科技金融政策的协调度研究 被引量:44
6
作者 程翔 杨小娟 张峰 《中国软科学》 CSSCI CSCD 北大核心 2020年第S01期115-124,共10页
区域经济高质量发展与科技金融政策的关系对社会发展至关重要。通过分析2007—2018年全国31个省份(港澳台除外)区域经济高质量发展与科技金融政策的协调度,对二者的协调状况做出评价。首先,以五大新发展理念出发,构建科学的区域经济高... 区域经济高质量发展与科技金融政策的关系对社会发展至关重要。通过分析2007—2018年全国31个省份(港澳台除外)区域经济高质量发展与科技金融政策的协调度,对二者的协调状况做出评价。首先,以五大新发展理念出发,构建科学的区域经济高质量发展评价指标体系,运用综合指数法测算各省市经济高质量发展水平;然后,制定科技金融政策打分手册,从政策力度、政策目标与政策措施三个维度对全国31个省份2007—2018年相关政策进行量化,分析科技金融政策的发展状况;最后,基于耦合协调度模型,分别从创新、协调、绿色、开放、共享五个角度计算经济发展与科技金融政策的协调度,最终测算两系统的总体协调度。结果表明:各地经济高质量发展与科技金融政策的协调状况存在较大差异。 展开更多
关键词 区域经济高质量发展 科技金融政策 耦合协调度模型 协调度
下载PDF
基于注意力机制的多通道CNN和BiGRU的文本情感倾向性分析 被引量:43
7
作者 程艳 尧磊波 +5 位作者 张光河 唐天伟 项国雄 陈豪迈 冯悦 蔡壮 《计算机研究与发展》 EI CSCD 北大核心 2020年第12期2583-2595,共13页
近年来,卷积神经网络(convolutional neural network,CNN)和循环神经网络(recurrent neural network,RNN)已在文本情感分析领域得到广泛应用,并取得了不错的效果.然而,文本之间存在上下文依赖问题,虽然CNN能提取到句子连续词间的局部信... 近年来,卷积神经网络(convolutional neural network,CNN)和循环神经网络(recurrent neural network,RNN)已在文本情感分析领域得到广泛应用,并取得了不错的效果.然而,文本之间存在上下文依赖问题,虽然CNN能提取到句子连续词间的局部信息,但是会忽略词语之间上下文语义信息;双向门控循环单元(bidirectional gated recurrent unit,BiGRU)网络不仅能够解决传统RNN模型存在的梯度消失或梯度爆炸问题,而且还能很好地弥补CNN不能有效提取长文本的上下文语义信息的缺陷,但却无法像CNN那样很好地提取句子局部特征.因此提出一种基于注意力机制的多通道CNN和双向门控循环单元(MC-AttCNN-AttBiGRU)的神经网络模型.该模型不仅能够通过注意力机制关注到句子中对情感极性分类重要的词语,而且结合了CNN提取文本局部特征和BiGRU网络提取长文本上下文语义信息的优势,提高了模型的文本特征提取能力.在谭松波酒店评论数据集和IMDB数据集上的实验结果表明:提出的模型相较于其他几种基线模型可以提取到更丰富的文本特征,可以取得比其他基线模型更好的分类效果. 展开更多
关键词 卷积神经网络 文本情感倾向性分析 双向门控循环单元 注意力机制 多通道
下载PDF
谷胱甘肽过氧化物酶GPX4在铁死亡中的作用与机制研究进展 被引量:43
8
作者 程峰 张庸 +2 位作者 王祥 窦晋涛 吴志浩 《现代肿瘤医学》 CAS 北大核心 2021年第7期1254-1258,共5页
谷胱甘肽过氧化物酶4(GPX4)是一种能够特异性催化谷胱甘肽将脂质过氧化物转化为类脂醇的硒蛋白,它在调节细胞铁死亡方面发挥着重要的作用。本文将对GPX4的蛋白结构、分子作用机制及其表达调控进行介绍,对其在铁死亡中的功能以及在癌症... 谷胱甘肽过氧化物酶4(GPX4)是一种能够特异性催化谷胱甘肽将脂质过氧化物转化为类脂醇的硒蛋白,它在调节细胞铁死亡方面发挥着重要的作用。本文将对GPX4的蛋白结构、分子作用机制及其表达调控进行介绍,对其在铁死亡中的功能以及在癌症等疾病中的应用进行系统综述,对未来存在的问题进行了分析与展望。 展开更多
关键词 GPX4 铁死亡 脂质过氧化 癌症
下载PDF
The second natural gas hydrate production test in the South China Sea 被引量:41
9
作者 Jian-liang Ye Xu-wen Qin +24 位作者 Wen-wei Xie Hai-long Lu Bao-jin Ma Hai-jun Qiu Jin-qiang Liang Jing-an Lu Zeng-gui Kuang cheng Lu Qian-yong Liang Shi-peng Wei Yan-jiang Yu Chunsheng Liu Bin Li Kai-xiang Shen Hao-xian Shi Qiu-ping Lu Jing Li Bei-bei Kou Gang Song Bo Li He-en Zhang Hong-feng Lu Chao Ma Yi-fei Dong Hang Bian 《China Geology》 2020年第2期197-209,共13页
Clayey silt reservoirs bearing natural gas hydrates(NGH)are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitabl... Clayey silt reservoirs bearing natural gas hydrates(NGH)are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitable by the first NGH production test conducted in the South China Sea in 2017.Based on the understanding of the first production test,the China Geological Survey determined the optimal target NGH reservoirs for production test and conducted a detailed assessment,numerical and experimental simulation,and onshore testing of the reservoirs.After that,it conducted the second offshore NGH production test in 1225 m deep Shenhu Area,South China Sea(also referred to as the second production test)from October 2019 to April 2020.During the second production test,a series of technical challenges of drilling horizontal wells in shallow soft strata in deep sea were met,including wellhead stability,directional drilling of a horizontal well,reservoir stimulation and sand control,and accurate depressurization.As a result,30 days of continuous gas production was achieved,with a cumulative gas production of 86.14×104 m3.Thus,the average daily gas production is 2.87×10^4 m^3,which is 5.57 times as much as that obtained in the first production test.Therefore,both the cumulative gas production and the daily gas production were highly improved compared to the first production test.As indicated by the monitoring results of the second production test,there was no anomaly in methane content in the seafloor,seawater,and atmosphere throughout the whole production test.This successful production test further indicates that safe and effective NGH exploitation is feasible in clayey silt NGH reservoirs.The industrialization of hydrates consists of five stages in general,namely theoretical research and simulation experiments,exploratory production test,experimental production test,productive production test,and commercial production.The second production test serves as an important step from the exploratory production test to exper 展开更多
关键词 Natural gas hydrates Second production test Horizontal well Reservoir stimulation Environmental impact NGH exploration trial engineering South China Sea
下载PDF
Chinese Multidisciplinary Expert Consensus on the Diagnosis and Treatment of Hyperuricemia and Related Diseases 被引量:39
10
作者 Zou, He-Jian Wu, Hu-Sheng +37 位作者 Zhou, Jing-Guo Zeng, Xue-Jun Dai, Lie Wu, Hua-xiang Zhu, Xiao-Xia Mei, Chang-Lin Hao, Chuan-Ming Chen, Nan Liu, Bi-cheng Chen, Jiang-Hua Yang, Li Nie, Jing Yu, Chen Peng, Ai Yu, Sheng-Qiang Li, Lin Ge, Jun-Bo Huo, Yong Zhang, Shu-Yang Chen, Yun-Dai Dong, Yu-Gang Liang, Chun Dai, Yu-xiang Gao, Xin Li, Chang-Gui Zhao, Jia-Jun Chen, Hai-Bing cheng, Zhi-Feng Lin, Huan-Dong Guan, Yang-Tai Wang, Kai Luo, Ben-Yan Dai, Ruo-Lian Jiang, Quan Xue, Luan Liang, Chao-Chao Chen, Ming Fan, Song 《Chinese Medical Journal》 SCIE CAS CSCD 2017年第20期2473-2488,共16页
INTRODUCTIONThe prevalence of hyperuricenlia (HUA) has increased in China in the recent years in relation to socioeconomic developments and changing lifestyles and diets, with a trend toward onset at younger age. HU... INTRODUCTIONThe prevalence of hyperuricenlia (HUA) has increased in China in the recent years in relation to socioeconomic developments and changing lifestyles and diets, with a trend toward onset at younger age. HUA has become the second most common metabolic disease after diabetes mellitus. Like gout, HUA is also associated with the occurrence and progression of disorders of the urinary, endocrine, metabolic, cardio-cerebrovascular, and other systems. 展开更多
关键词 CONSENSUS GOUT HYPERURICEMIA RECOMMENDATION Uric Acid
原文传递
数字经济如何影响我国消费型经济增长水平 被引量:37
11
作者 黄志 程翔 邓翔 《山西财经大学学报》 CSSCI 北大核心 2022年第4期69-83,共15页
通过测算2010—2017年我国31个省份的消费型经济增长水平,实证检验了数字经济对消费型经济增长的影响。结果显示,数字经济与消费型经济增长呈“正U型”关系。进一步分析发现,数字经济将先恶化后改善需求结构和消费结构使消费型经济增长... 通过测算2010—2017年我国31个省份的消费型经济增长水平,实证检验了数字经济对消费型经济增长的影响。结果显示,数字经济与消费型经济增长呈“正U型”关系。进一步分析发现,数字经济将先恶化后改善需求结构和消费结构使消费型经济增长水平先下降后上升;产业数字化与消费型经济增长呈“正U型”非线性关系,但数字产业化的影响不显著。此外,数字经济对消费型经济增长的影响存在区域差异,东部地区或沿海地区消费型经济增长水平先下降后上升,西部地区或内陆地区呈持续下降趋势,而对中部地区影响不显著。 展开更多
关键词 数字经济 数字产业化 产业数字化 消费水平 消费型经济增长
原文传递
Broadband diffusion of terahertz waves by multi-bit coding metasurfaces 被引量:38
12
作者 Li-Hua Gao Qiang cheng +15 位作者 Jing Yang Shao-Jie Ma Jie Zhao Shuo Liu Hai-Bing Chen Qiong He Wei-xiang Jiang Hui-Feng Ma Qi-Ye Wen Lan-Ju Liang Biao-Bing Jin Wei-Wei Liu Lei Zhou Jian-Quan Yao Pei-Heng Wu Tie-Jun Cui 《Light(Science & Applications)》 SCIE EI CAS CSCD 2015年第1期207-215,共9页
The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves.In the past decade,metamaterials with effective medium parameters o... The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves.In the past decade,metamaterials with effective medium parameters or gradient phases have been studied to control terahertz waves and realize functional devices.Here,we present a new approach to manipulate terahertz waves by using coding metasurfaces that are composed of digital coding elements.We propose a general coding unit based on a Minkowski closed-loop particle that is capable of generating 1-bit coding(with two phase states of 0 and 180°),2-bit coding(with four phase states of 0,90°,180°,and 270°),and multi-bit coding elements in the terahertz frequencies by using different geometric scales.We show that multi-bit coding metasurfaces have strong abilities to control terahertz waves by designing-specific coding sequences.As an application,we demonstrate a new scattering strategy of terahertz waves—broadband and wide-angle diffusion—using a 2-bit coding metasurface with a special coding design and verify it by both numerical simulations and experiments.The presented method opens a new route to reducing the scattering of terahertz waves. 展开更多
关键词 CODING DIFFUSION metasurface terahertz waves
原文传递
Reduction of tumorigenicity of SMMC-7721 hepatoma cells by vascular endothelial growth factor antisense gene therapy 被引量:33
13
作者 Yu cheng Tang Yu Li Guan xiang Qian Department of Biochemistry, Shanghai Second Medical University, Shanghai 200025, China 《World Journal of Gastroenterology》 SCIE CAS CSCD 2001年第1期22-27,共6页
AIM: To test the hypothesis to block VEGF expression of SMMC-7721 hepatoma cells may inhibit tumor growth using the rat hepatoma model. METHODS: Amplify the 200 VEGF cDNA fragment and insert it into human U6 gene cass... AIM: To test the hypothesis to block VEGF expression of SMMC-7721 hepatoma cells may inhibit tumor growth using the rat hepatoma model. METHODS: Amplify the 200 VEGF cDNA fragment and insert it into human U6 gene cassette in the reverse orientation transcribing small antisense RNA which could specifically interact with VEGF165, and VEGF121 mRNA. Construct the retroviral vector containing this antisense VEGF U6 cassette and package the replication-deficient recombinant retrovirus. SMMC-7721 cells were transduced with these virus and positive clones were selected with G418. PCR and Southern blot analysis were performed to determine if U6 cassette integrated into the genomic DNA of positive clone. Transfected tumor cells were evaluated for RNA expression by ribonuclease protection assays. The VEGF protein in the supernatant of parental tumor cells and genetically modified tumor cells was determined with ELISA. In vitro and in vivo growth properties of antisense VEGF cell clone in nude mice were analyzed. RESULTS: Restriction enzyme digestion and PCR sequencing verified that the antisense VEGF RNA retroviral vector was successfully constructed.After G418 selection, resistant SMMC-7721 cell clone was picked up. PCR and Southern blot analysis suggested that U6 cassette was integrated into the cell genomic DNA. Stable SMMC-7721 cell clone transduced with U6 antisense RNA cassette could express 200 bp small antisense VEGF RNA and secrete reduced levels of VEGF in culture condition. Production of VEGF by antisense transgene-expressing cells was 65+/-10 ng/L per 10(6) cells, 42045 ng/L per 10(6) cells in sense group and 485+/-30 ng/L per 10(6) cells in the negative control group, (P【 0.05). The antisense-VEGF cell clone appeared phenotypically indistinguishable from SMMC-7721 cells and SMMC-7721 cells transfected sense VEGF. The growth rate of the antisense-VEGF cell clone was the same as the control cells. When S.C. was implanted into nude mice, growth of antisense-VEGF cell lines was greatly inhibited compared with co 展开更多
关键词 Gene Therapy Animals Carcinoma Hepatocellular Cell Division DNA Polymerase III Endothelial Growth Factors Endothelium Vascular Enzyme-Linked Immunosorbent Assay Gene Expression Humans Liver Neoplasms LYMPHOKINES MICE Mice Nude Neovascularization Pathologic Promoter Regions (Genetics) RNA Antisense Research Support Non-U.S. Gov't Transduction Genetic Tumor Cells Cultured Vascular Endothelial Growth Factor A Vascular Endothelial Growth Factors
下载PDF
铝土矿分布特点、主要类型与勘查开发现状 被引量:36
14
作者 张海坤 胡鹏 +4 位作者 姜军胜 程湘 王建雄 刘江涛 向鹏 《中国地质》 CAS CSCD 北大核心 2021年第1期68-81,共14页
铝土矿是金属铝的主要来源,近年来,随着经济社会快速发展和城镇化逐步推进,中国铝需求量逐年走高。文章简要概括了铝土矿的分布特点、主要类型及主要资源国的铝土矿分布情况,着重介绍了最近几年铝土矿勘查开发的新进展,以深化对铝土矿... 铝土矿是金属铝的主要来源,近年来,随着经济社会快速发展和城镇化逐步推进,中国铝需求量逐年走高。文章简要概括了铝土矿的分布特点、主要类型及主要资源国的铝土矿分布情况,着重介绍了最近几年铝土矿勘查开发的新进展,以深化对铝土矿空间分布、地质特征的认识,把握铝土矿的勘查开发趋势。根据矿石成因,铝土矿主要分为红土型和岩溶型两类,前者主要分布在非洲西部、南美洲北部、印度、东南亚及澳大利亚北部和西南部,后者主要分布在南欧、加勒比海地区、亚洲西部和中国。铝土矿勘查方面,在铝土矿储量大国中,几内亚、俄罗斯、澳大利亚主要以对大型成熟铝土矿山的扩边增储工作为主,巴西、加纳、牙买加等国则主要以勘探新区为主。铝土矿开发方面,目前全球铝土矿主要生产国为澳大利亚、几内亚和中国,2019年三国合计铝土矿产量约占世界总产量的70%。2020年上半年,受新冠肺炎疫情影响,主要金属价格出现恐慌性大幅下跌。虽然近期主要金属价格有震荡反弹趋势,但以美国、巴西、印度等为代表的世界主要经济体仍深陷疫情泥潭,英国、法国、意大利等欧盟国家仍面临较大防控压力,全球也存在爆发第二波疫情的可能,在此背景下,铝土矿勘查开发形势仍存在很大变数。 展开更多
关键词 铝土矿 空间分布 主要类型 勘查开发现状
下载PDF
Engineering a New Chloroplastic Photorespiratory Bypass to In crease Photosynthetic Efficiency and Productivity in Rice 被引量:35
15
作者 Bo-Ran Shen Li-Min Wang +9 位作者 Xiu-Ling Lin Zhen Yao Hua-Wei Xu cheng-Hua Zhu Hai-Yan Teng Li-Li Cui E.-E. Liu Jian-Jun Zhang Zheng-Hui He Xin-xiang Peng 《Molecular Plant》 SCIE CAS CSCD 2019年第2期199-214,共16页
Over the past few years, three photorespiratory bypasses have been introduced into plants, two of which led to observable in creases in photos yn thesis and biomass yield. However, most of the experiments were carried... Over the past few years, three photorespiratory bypasses have been introduced into plants, two of which led to observable in creases in photos yn thesis and biomass yield. However, most of the experiments were carried out using Arabidopsis under controlled environmental conditions, and the increases were only observed under low-light and short-day conditions. In this study, we designed a new photorespiratory bypass (called GOC bypass), characterized by no reducing equivalents being produced during a complete oxidation of glycolate into CO2 catalyzed by three rice-self-originating enzymes, i.e., glycolate oxidase, oxalate oxidase, and catalase. We successfully established this bypass in rice chloroplasts using a multi-gene assembly and transformation system. Transgenic rice plants carrying GOC bypass (GOC plants) showed significant increases in photosynthesis efficiency, biomass yield, and nitrogen content, as well as several other CO2-enriched phe no types under both greenhouse and field conditions .Grain yield of GOC plants varied depending on seeding season and was increased significantly in the spring. We further demonstrated that GOC plants had significant advantages under high-light conditions and that the improvements in GOC plants resulted primarily from a photosynthetic CO2-concentrating effect rather than from improved energy balance. Taken together, our results reveal that engineering a newly designed chloroplastic photorespiratory bypass could increase photosynthetic efficiency and yield of rice plants grown in field conditions, particularly under high light. 展开更多
关键词 photorespiratory BYPASS PHOTOSYNTHETIC EFFICIENCY PRODUCTIVITY RICE
原文传递
中国自贸区金融改革与创新的实践研究——基于四大自贸区的金融创新案例 被引量:35
16
作者 程翔 杨宜 张峰 《经济体制改革》 CSSCI 北大核心 2019年第3期12-17,共6页
自由贸易试验区是我国新一轮改革开放的支点,发挥了试验区、桥头堡和排头兵的重要作用。金融领域的改革创新是自贸区建设的重要内容。本文系统整理了上海、天津、广东、福建四大自贸区近年来发布的330项金融创新案例,发现其具有数量多... 自由贸易试验区是我国新一轮改革开放的支点,发挥了试验区、桥头堡和排头兵的重要作用。金融领域的改革创新是自贸区建设的重要内容。本文系统整理了上海、天津、广东、福建四大自贸区近年来发布的330项金融创新案例,发现其具有数量多、涉及范围广、区域特色鲜明、复制性不强等特点和问题。未来建设自由贸易港,金融创新必须围绕服务实体经济提供多元化国际化金融工具与服务以及做好顶层设计对金融业开放进行合理、适度、有效监管两个中心展开。 展开更多
关键词 自由贸易区 金融创新 区域性特征
原文传递
基于LSTM神经网络的煤矿突水预测 被引量:35
17
作者 董丽丽 费城 +1 位作者 张翔 曹超凡 《煤田地质与勘探》 CAS CSCD 北大核心 2019年第2期137-143,共7页
针对煤层底板突水预测问题,在总结现有突水预测方法和理论的基础上,通过特征选择实验得出水压、距工作面距离、砂岩段厚度、煤层厚度、煤层倾角、断层落差、裂隙带、开采面积、采高、走向长度是影响突水发生的主要因素,这些因素具有复... 针对煤层底板突水预测问题,在总结现有突水预测方法和理论的基础上,通过特征选择实验得出水压、距工作面距离、砂岩段厚度、煤层厚度、煤层倾角、断层落差、裂隙带、开采面积、采高、走向长度是影响突水发生的主要因素,这些因素具有复杂、非线性的特点。提出基于长短时记忆(LSTM)神经网络构建的突水预测模型,将煤矿突水实例的数据作为样本数据对模型进行训练。最后,将LSTM神经网络模型与遗传算法–反向传播(GA-BP)神经网络模型和反向传播(BP)神经网络模型进行对比实验。实验结果表明,LSTM神经网络模型在测试集上的预测正确率更高,稳定性更好,更适用于煤层底板突水预测。 展开更多
关键词 长短时记忆 特征选择 煤层底板突水预测
下载PDF
科技金融政策是否提升了企业竞争力?——来自高新技术上市公司的证据 被引量:34
18
作者 程翔 张瑞 张峰 《经济与管理研究》 CSSCI 北大核心 2020年第8期131-144,共14页
在创新驱动发展战略背景下研究区域科技金融政策对微观企业竞争力的影响具有重要意义。宏观层面以2007—2017年全国31个省份颁布的科技金融政策作为研究对象,设计政策量化手册对科技金融政策进行文本量化;微观层面构建企业竞争力评价指... 在创新驱动发展战略背景下研究区域科技金融政策对微观企业竞争力的影响具有重要意义。宏观层面以2007—2017年全国31个省份颁布的科技金融政策作为研究对象,设计政策量化手册对科技金融政策进行文本量化;微观层面构建企业竞争力评价指标体系,选取A股558家高科技产业上市公司,通过实证模型研究区域科技金融政策对企业竞争力的影响。结果表明:科技金融政策与企业竞争力呈显著的正相关关系且具有一定滞后性;不同政策类型、不同市场类型、不同企业性质使得科技金融政策的实施效果不尽相同。 展开更多
关键词 科技金融政策 企业竞争力 高科技产业 政策量化
下载PDF
Extending the CONSORT Statement to moxibustion 被引量:32
19
作者 Chung-wah cheng Shu-fei Fu +11 位作者 Qing-hui Zhou Tai-xiang Wu Hong-cai Shang Xu-dong Tang Zhi-shun Liu Jia Liu Zhi-xiu Lin Lixing Lao Ai-ping Bo-li Zhang Bao-yan Liu Zhao-xiang Bian 《Journal of Integrative Medicine》 SCIE CAS CSCD 2013年第1期54-63,共10页
The STandards for Reporting Interventions in Clinical Trials Of Moxibustion (STRICTOM), in the form of a checklist and descriptions of checklist items, were designed to improve reporting of moxibustion trials, and t... The STandards for Reporting Interventions in Clinical Trials Of Moxibustion (STRICTOM), in the form of a checklist and descriptions of checklist items, were designed to improve reporting of moxibustion trials, and thereby facilitating their interpretation and replication. The STRICTOM checklist included 7 items and 16 sub-items. These set out reporting guidelines for the moxibustion rationale, details of moxibustion, treatment regimen, other components of treatment, treatment provider background, control and comparator interventions, and precaution measures. In addition, there were descriptions of each item and examples of good reporting. It is intended that the STRICTOM can be used in conjunction with the main CONSORT Statement, extensions for nonpharmacologic treatment and pragmatic trials, and thereby raise the quality of reporting of clinical trials of moxibustion. Further comments will be solicited from the experts of the CONSORT Group, the STRICTA Group, acupuncture and moxibustion societies, and clinical trial authors for optimizing the STRICTOM. 展开更多
关键词 MOXIBUSTION randomized controlled trials GUIDELINES
下载PDF
基于物联网的智能家居控制系统设计 被引量:32
20
作者 程翔 许正荣 张昆明 《传感器与微系统》 CSCD 北大核心 2021年第3期106-108,111,共4页
针对传统智能家居系统使用范围限制在近距离、控制方式单一的局限,提出了一种基于物联网(Io T)的智能家居控制系统设计方案,系统主要由STC12单片机节点、STM32主控制器、服务器组成。节点承载着受控家居器件,并通过NRF24L01无线射频模... 针对传统智能家居系统使用范围限制在近距离、控制方式单一的局限,提出了一种基于物联网(Io T)的智能家居控制系统设计方案,系统主要由STC12单片机节点、STM32主控制器、服务器组成。节点承载着受控家居器件,并通过NRF24L01无线射频模块与主控制器通信;主控制器提供操作界面,并通过Wi-Fi与服务器通信;服务器部署网站供用户访问。系统可通过主控制器在本地对家居进行控制,通过手机或电脑在远程对家居进行控制、采集与显示环境信息。系统可靠性强、功耗低,易于扩展。 展开更多
关键词 智能家居 物联网 单片机 无线通信
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部