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   3690篇
  免费   207篇
  2022年   29篇
  2021年   72篇
  2020年   37篇
  2019年   55篇
  2018年   64篇
  2017年   68篇
  2016年   89篇
  2015年   124篇
  2014年   135篇
  2013年   181篇
  2012年   242篇
  2011年   220篇
  2010年   143篇
  2009年   126篇
  2008年   173篇
  2007年   149篇
  2006年   134篇
  2005年   131篇
  2004年   119篇
  2003年   88篇
  2002年   95篇
  2001年   93篇
  2000年   64篇
  1999年   73篇
  1998年   32篇
  1997年   30篇
  1996年   25篇
  1995年   25篇
  1992年   50篇
  1991年   61篇
  1990年   46篇
  1989年   57篇
  1988年   40篇
  1987年   50篇
  1986年   32篇
  1985年   73篇
  1984年   46篇
  1983年   51篇
  1981年   30篇
  1980年   41篇
  1979年   53篇
  1978年   33篇
  1977年   25篇
  1976年   27篇
  1975年   27篇
  1974年   32篇
  1973年   28篇
  1971年   34篇
  1970年   29篇
  1969年   33篇
排序方式: 共有3897条查询结果,搜索用时 15 毫秒
1.
Synthesis of a library of novel trans 6-methoxy-1,1-dimethyl-2-phenyl-3-aryl-2,3-dihydro-1H-inden-4-yloxy alkyl amines and their antimycobacterial activity against drug sensitive and multidrug resistant strains of Mycobacterium tuberculosis have been reported. All the new compounds in the series exhibited MIC between 1.56 and 6.25 μg/ml. Two compounds 1i and 1j with low MIC and low cytotoxicity showed significant reduction in CFU in infected mouse macrophages at 1× MIC concentration. The compound 1i inhibited the growth of M. tuberculosis in mice at 100 mg/kg dose with 1.35 log10 reduction of CFU in lungs tissue and was active against non-replicating Mycobacterium tuberculosis under anaerobic condition.  相似文献   
2.
Dr A C Srivastava has written to us to describe a case that raises the suggestion that people infected with the human immuno-deficiency virus (HIV) should carry identity cards. We asked two physicians, a general practitioner working with patients with the acquired immune deficiency syndrome (AIDS), and a general practitioner with a special interest in medical ethics to respond to the broad issues raised by Dr Srivastava''s letter.  相似文献   
3.
4.
Preface     
Molecular and Cellular Biochemistry -  相似文献   
5.
6.
Almost all primates experience seasonal fluctuations in the availability of key food sources. However, the degree to which this fluctuation impacts foraging behavior varies considerably. Eastern chimpanzees (Pan troglodytes schweinfurthii) in Nyungwe National Park, Rwanda, live in a montane forest environment characterized by lower primary productivity and resource diversity than low‐elevation forests. Little is known about chimpanzee feeding ecology in montane forests, and research to date predominantly relies on indirect methods such as fecal analyses. This study is the first to use mostly observational data to examine how seasonal food availability impacts the feeding ecology of montane forest chimpanzees. We examine seasonal changes in chimpanzee diet and fallback foods (FBFs) using instantaneous scan samples and fecal analyses, supported by inspection of feeding remains. Chimpanzee fruit abundance peaked during the major dry season, with a consequent change in chimpanzee diet reflecting the abundance and diversity of key fruit species. Terrestrial herbaceous vegetation was consumed throughout the year and is defined as a “filler” FBF. In contrast to studies conducted in lower‐elevation chimpanzee sites, figs (especially Ficus lutea) were preferred resources, flowers were consumed at seasonally high rates and the proportion of non‐fig fruits in the diet were relatively low in the current study. These divergences likely result from the comparatively low environmental diversity and productivity in higher‐elevation environments.  相似文献   
7.
8.
9.
10.
QSAR studies have been performed on the homologues of 3-triazines, using molecular connectivity index and van der Waal volume as structural parameters. The regression analysis has shown good correlation between antitumour activity and the two structural parameters.  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