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   480221篇
  免费   165654篇
  国内免费   29746篇
  675621篇
  2018年   5973篇
  2017年   5643篇
  2016年   6975篇
  2015年   9197篇
  2014年   10309篇
  2013年   13662篇
  2012年   15322篇
  2011年   16105篇
  2010年   13064篇
  2009年   17034篇
  2008年   15111篇
  2007年   15326篇
  2006年   13413篇
  2005年   13085篇
  2004年   12703篇
  2003年   12189篇
  2002年   12536篇
  2001年   23572篇
  2000年   21690篇
  1999年   21605篇
  1998年   13132篇
  1997年   13082篇
  1996年   12320篇
  1995年   12284篇
  1994年   11684篇
  1993年   11421篇
  1992年   19413篇
  1991年   19282篇
  1990年   19302篇
  1989年   18527篇
  1988年   16850篇
  1987年   15812篇
  1986年   14765篇
  1985年   14261篇
  1984年   11694篇
  1983年   9897篇
  1982年   8474篇
  1981年   7640篇
  1980年   7389篇
  1979年   10663篇
  1978年   8809篇
  1977年   8135篇
  1976年   7678篇
  1975年   7862篇
  1974年   8368篇
  1973年   8255篇
  1972年   7898篇
  1971年   7245篇
  1970年   6238篇
  1969年   6111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Introduction  

Sj?gren's syndrome (SS) is a systemic autoimmune disease that mainly targets the exocrine glands. The aim of this study was to investigate the involvement of 87 proteins measured in serum and 75 proteins analyzed in saliva in spontaneous experimental SS. In addition, we intended to compute a model of the immunological situation representing the overt disease stage of SS.  相似文献   
992.
993.
A new class of Phycomyces behavioral mutants with enhanced tropic responses has been analyzed genetically to determine the number of genes involved and the nature of their expression. These hypertropic mutants carry pleiotropic nuclear mutations. Besides their effects on sensory behavior, they also affect morphology and meiotic processes. Behavioral analyses of heterokaryons containing hypertropic and wild-type nuclei in varying proportions show that the hypertropic mutations in strains L82, L84, L86, and L88 are strongly dominant. Conversely, the hypertropic mutations carried by the strains L83, L85, and L87 are strongly recessive. We performed recombination analyses between hypertropic mutants and mutants with diminished phototropism, affected in the seven genes madA to madG. We found no evidence of linkage between the hypertropic mutations and any of these mad mutations. From crosses, we isolated double mutants carrying hypertropic mutations together with madC (night blind) and madG (stiff) mutations. The behavioral phenotypes of the double mutants are intermediate between those of the parentals. Complementation analyses show that the three recessive hypertropic mutations affect the same gene, which we call madH. The expression of the recessive hypertropic allele becomes dominant in heterokaryons carrying madC and madH nuclei; the madC gene has been implicated separately with the photoreceptor at the input to the sensory pathway, while the madH gene is associated with the growth control output. This result suggests the physical interaction of both gene products, madH and madC, in a molecular complex for the photosensory transduction chain.  相似文献   
994.
The effects of mechanical injury on the skin, connective tissue, muscle and bone of the goldfish is described 28 days following the injury. There is evidence of a dynamic response but the apparent inability of muscle regeneration to any degree is noted.  相似文献   
995.
996.
997.
998.
999.
1000.
Abstract

The conformations of the chains constituting the hydrophilic component of alkyl monolayers and bilayers are investigated by performing molecular dynamics atomistic simulations on these systems at different temperatures. Several monitoring techniques are used to reveal the chain conformations, including atom pair radial distribution functions, evolutions of the torsional angles over thousands of timesteps, frequency distributions of the torsionl angles and ‘snapshot’ plots of the atomic configurations. These methods consistently testify to the stability of the trans (fully extended) character of the strain-free alkyl chains up to room temperature. The chains retain much of this conformation even when the layers are compressed by the application of pressure, to which the chains respond by ‘folding’ at the ends attaching them to the substrate planes while maintaining directions which are mainly normal to these planes. A non-zero gap between the layers is also maintained. A pressure of about 50 kbar abruptly causes all motion in the chains to cease, resulting in a highly ordered lattice structure.  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