首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   169篇
  免费   3篇
  国内免费   8篇
系统科学   16篇
丛书文集   3篇
理论与方法论   3篇
现状及发展   39篇
研究方法   15篇
综合类   104篇
  2022年   1篇
  2021年   1篇
  2018年   1篇
  2017年   1篇
  2016年   2篇
  2015年   3篇
  2014年   5篇
  2013年   6篇
  2012年   6篇
  2011年   6篇
  2010年   2篇
  2009年   4篇
  2008年   6篇
  2007年   7篇
  2006年   5篇
  2005年   11篇
  2004年   4篇
  2003年   14篇
  2002年   27篇
  2001年   18篇
  2000年   10篇
  1999年   3篇
  1998年   1篇
  1996年   1篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1982年   1篇
  1979年   1篇
  1977年   4篇
  1976年   4篇
  1975年   2篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1970年   4篇
  1969年   4篇
  1968年   3篇
  1967年   1篇
  1965年   1篇
  1955年   1篇
  1954年   1篇
排序方式: 共有180条查询结果,搜索用时 7 毫秒
41.
The bacterial genus Bartonella comprises 21 pathogens causing characteristic intraerythrocytic infections. Bartonella bacilliformis is a severe pathogen representing an ancestral lineage, whereas the other species are benign pathogens that evolved by radial speciation. Here, we have used comparative and functional genomics to infer pathogenicity genes specific to the radiating lineage, and we suggest that these genes may have facilitated adaptation to the host environment. We determined the complete genome sequence of Bartonella tribocorum by shotgun sequencing and functionally identified 97 pathogenicity genes by signature-tagged mutagenesis. Eighty-one pathogenicity genes belong to the core genome (1,097 genes) of the radiating lineage inferred from genome comparison of B. tribocorum, Bartonella henselae and Bartonella quintana. Sixty-six pathogenicity genes are present in B. bacilliformis, and one has been lost by deletion. The 14 pathogenicity genes specific for the radiating lineage encode two laterally acquired type IV secretion systems, suggesting that these systems have a role in host adaptability.  相似文献   
42.
椎弓根进钉通道数字化分析研究   总被引:1,自引:0,他引:1  
脊柱椎弓根内固定技术是恢复脊柱形态和功能的重要手段,如何安全有效地植入螺钉一直是临床应用研究十分关注的课题,本文将医学影像和医学三维重建技术与逆向工程技术结合,通过获取CT连续断层图像,重建椎骨三维数字解剖表面模型,应用逆向工程技术对三维数字解剖模型进行数字化三维定量分析与设计,探索建立定位,定量研究椎弓根进钉通道的方法,从椎骨整体三维空间上获得准确的进钉通道数据.  相似文献   
43.
44.
M Roux  M P Dubois 《Experientia》1976,32(5):657-658
Alpha-MSH, beta-MSH and ACTH have been localized in the cells of hypophyseal intermediate lobe by fluorescence histoimmunological technics. Elaboration and excretion of these polypeptides are enhanced after dehydration or adrenalectomy. The most evident variations are seen with alpha-MSH and ACTH after dehydration, with beta-MSH after adrenalectomy.  相似文献   
45.
In this paper, Cassava dregs are an outgrowth produced during starchy production which uses cassava as raw material. It is usually dropped out or used as cheap feedstuff. In order to make the best use of cassava dregs, increase industries' benefits and reduce castoffthis study developed a 'new technique which used cassava dregs as raw material to produce distilled spirits based on cassava dregs characteristics. The technique adopt solid-ferment procedure. At first, the ferment is processed by solid-state distilling, and then rectification extra care refinement; at last the tequila was produced with characteristics of simple and elegant fragrance and mellow-tasting.  相似文献   
46.
Endocrine-disrupting chemicals (EDCs) represent a broad class of exogenous substances that cause adverse effects in the endocrine system by interfering with hormone biosynthesis, metabolism, or action. The molecular mechanisms of EDCs involve different pathways including interactions with nuclear hormone receptors (NHRs) which are primary targets of a large variety of environmental contaminants. Here, based on the crystal structures currently available in the Protein Data Bank, we review recent studies showing the many ways in which EDCs interact with NHRs and impact their signaling pathways. Like the estrogenic chemical diethylstilbestrol, some EDCs mimic the natural hormones through conserved protein–ligand contacts, while others, such as organotins, employ radically different binding mechanisms. Such structure-based knowledge, in addition to providing a better understanding of EDC activities, can be used to predict the endocrine-disrupting potential of environmental pollutants and may have applications in drug discovery.  相似文献   
47.
本文论证了伯塞洛脱系统存在一个对应态定理,并给出了该系统的临界指数。  相似文献   
48.
针对空间网架螺栓节点球在特定的分度夹紧装置上进行自动编程数控加工的过程 ,讨论了加工过程中夹紧信息的识别与提取 ,并以数学语言加以描述 ,有利于用计算机语言编程 ,实现螺栓节点球数控加工过程中夹紧状态判别的自动化  相似文献   
49.
全国普通高校体育教育专业体操比赛的调查研究   总被引:2,自引:0,他引:2  
通过对全国普通高校体育教育专业体操团体比赛成绩的统计分析,认为各校运动队以良好的运动竞技表演接受了国家教育部的检查,深化了体育教学改革,并对存有不足提出相应的建议。  相似文献   
50.
Zhu P  Liu J  Bess J  Chertova E  Lifson JD  Grisé H  Ofek GA  Taylor KA  Roux KH 《Nature》2006,441(7095):847-852
Envelope glycoprotein (Env) spikes on AIDS retroviruses initiate infection of host cells and are therefore targets for vaccine development. Though crystal structures for partial Env subunits are known, the structure and distribution of native Env spikes on virions is obscure. We applied cryoelectron microscopy tomography to define ultrastructural details of spikes. Virions of wild-type human immunodeficiency virus 1 (HIV-1) and a mutant simian immunodeficiency virus (SIV) had approximately 14 and approximately 73 spikes per particle, respectively, with some clustering of HIV-1 spikes. Three-dimensional averaging showed that the surface glycoprotein (gp120) 'head' of each subunit of the trimeric SIV spike contains a primary mass, with two secondary lobes. The transmembrane glycoprotein 'stalk' of each trimer is composed of three independent legs that project obliquely from the trimer head, tripod-like. Reconciling available atomic structures with the three-dimensional whole spike density map yields insights into the orientation of Env spike structural elements and possible structural bases of their functions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号