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   17304篇
  免费   2053篇
  国内免费   5篇
  2021年   234篇
  2019年   139篇
  2018年   188篇
  2017年   183篇
  2016年   300篇
  2015年   471篇
  2014年   558篇
  2013年   725篇
  2012年   833篇
  2011年   855篇
  2010年   551篇
  2009年   490篇
  2008年   694篇
  2007年   739篇
  2006年   667篇
  2005年   639篇
  2004年   609篇
  2003年   562篇
  2002年   547篇
  2001年   490篇
  2000年   508篇
  1999年   445篇
  1998年   264篇
  1997年   215篇
  1996年   202篇
  1995年   187篇
  1994年   176篇
  1993年   183篇
  1992年   379篇
  1991年   294篇
  1990年   328篇
  1989年   290篇
  1988年   311篇
  1987年   318篇
  1986年   252篇
  1985年   281篇
  1984年   225篇
  1983年   234篇
  1982年   202篇
  1981年   183篇
  1980年   173篇
  1979年   242篇
  1978年   211篇
  1977年   184篇
  1976年   185篇
  1975年   171篇
  1974年   172篇
  1973年   183篇
  1972年   163篇
  1971年   135篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A procedure was developed for the detection of 2′,3′-cyclic nucleotide 3′-phosphohydrolase in myelin. This assay was sufficiently sensitive to detect the low levels of 2′,3′-cyclic nucleotide 3′-phosphohydrolase in human erythrocytes. The 2′,3′-cyclic nucleotide 3′-phosphohydrolase of human erythrocytes was determined to be exclusively associated with the inner (cytosolic) side of the membrane. Leaky ghostsand resealed ghosts were assayed for 2′,3′-cyclic nucleotide 3′-phosphohydrolase, (Ca2+/Mg2+-ATPase, and acetylcholinesterase activity, and the 2′,3′-cyclic nucleotide 3′-phosphohydrolase profile is the same as that of the (Ca2+/Mg2+)-ATPase, an established inner membrane maker.  相似文献   
32.
33.
34.
35.
36.
37.
When expressed in Escherichia coli, a truncated form of phytochrome (oat PHYA AP3 residues 464-1129) self associates to form a series of products ranging in size from monomers to aggregates of greater than 20 subunits. When these same phytochrome sequences are coexpressed with the chaperonins GroEL and GroES, the truncated phytochrome migrates as a native-like dimer in size exclusion chromatography and no higher-order aggregates were detected. GroEL and GroES inhibition of phytochrome aggregation in E. coli presumably occurs via the suppression of folding pathways leading to incorrectly folded phytochrome.  相似文献   
38.
Upper gastrointestinal endoscopy is a valuable diagnostic tool, but for an endoscopy service to be effective it is essential that it is not overloaded with inappropriately referred patients. A joint working party in Britain has considered the available literature on indications for endoscopy, assessed standard practice through a questionnaire, and audited randomly selected cases using an independent panel of experts and an American database system. They used these data to produce guidelines on the appropriate and inappropriate indications for referral for endoscopy, although they emphasise that under certain circumstances there may be reasons to deviate from the advice given. The need for endoscopy is most difficult to judge in patients with dyspepsia, and this aspect is discussed in detail. Early endoscopy will often prove more cost effective than delaying until the indications are clearer.  相似文献   
39.
40.
Macrophages are essential for normal wound repair and many of their effects on healing wounds are likely to be mediated by the secretion of cytokines. This study examines the appearance of messenger RNA (mRNA) for cachectin/tumor necrosis factor (TNF), IL 1, and macrophage inflammatory proteins 1 and 2 (MIP-1 and MIP-2), as well as the mature peptides, in a model of wound healing using wound chambers. RNA for all four cytokines can be detected in wound inflammatory cells by polymerase chain reaction amplification throughout the first 7 days. Cachectin/TNF and IL 1 protein levels peaked on the first day after wound chamber implantation, and MIP-1 and MIP-2 were detected only on day 3. The data suggest that these cytokines participate in the early inflammatory response to wounding.  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