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   1511828篇
  免费   143070篇
  国内免费   1506篇
  1656404篇
  2021年   18943篇
  2019年   16913篇
  2018年   19093篇
  2017年   17667篇
  2016年   29956篇
  2015年   45178篇
  2014年   53546篇
  2013年   80199篇
  2012年   45320篇
  2011年   34395篇
  2010年   47017篇
  2009年   47790篇
  2008年   31689篇
  2007年   29815篇
  2006年   34082篇
  2005年   34624篇
  2004年   33653篇
  2003年   30807篇
  2002年   28434篇
  2001年   40279篇
  2000年   37960篇
  1999年   36435篇
  1998年   26469篇
  1997年   26379篇
  1996年   25761篇
  1995年   23907篇
  1994年   23720篇
  1993年   22885篇
  1992年   31421篇
  1991年   29995篇
  1990年   28623篇
  1989年   29029篇
  1988年   26794篇
  1987年   25544篇
  1986年   24307篇
  1985年   26155篇
  1984年   25214篇
  1983年   22316篇
  1982年   22033篇
  1981年   21315篇
  1980年   19841篇
  1979年   21893篇
  1978年   19937篇
  1977年   18988篇
  1976年   18078篇
  1975年   17911篇
  1974年   18409篇
  1973年   18667篇
  1972年   16230篇
  1971年   14610篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Background  

Digital atlases provide a common semantic and spatial coordinate system that can be leveraged to compare, contrast, and correlate data from disparate sources. As the quality and amount of biological data continues to advance and grow, searching, referencing, and comparing this data with a researcher's own data is essential. However, the integration process is cumbersome and time-consuming due to misaligned data, implicitly defined associations, and incompatible data sources. This work addressing these challenges by providing a unified and adaptable environment to accelerate the workflow to gather, align, and analyze the data.  相似文献   
992.
993.
994.
The cavernicolous crustacean Antromysis juberthiei showed unexpected behavior when presented with food extract : it avoids the area of odor inflow. This avoidance reaction is reduced by removal of various combinations of antennae and disappears almost with bilateral removal of the first antennae (the aesthetasc-bearing antennules).  相似文献   
995.
A LIM motif is present in a pollen-specific protein.   总被引:5,自引:2,他引:3       下载免费PDF全文
R Baltz  J L Evrard  C Domon    A Steinmetz 《The Plant cell》1992,4(12):1465-1466
  相似文献   
996.
Summary The ability of microorganisms to produce hydantoinase and L-N-carbamoylase could be established by an overlay assay. Enzyme producing strains form clear areas around their colonies caused by the cleavage of D,L-indolylmethylhydantoin. A second overlayer with a tryptophan-auxotroph yeast enables us to detect microorganisms which are able to produce L-tryptophan from D,L-indolylmethylhydantoin.  相似文献   
997.
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   
998.
Verapamil is a calcium-channel blocking agent, commonly used for chronic treatment of heart conditions. We have previously demonstrated that verapamil acts as a co-mutagen in a bacterial mutagenicity test for some experimental anilinoacridine antitumour drugs. Within the anilinoacridines series there are several compounds which are apparently non-mutagenic (or very weak mutagens) in the absence of verapamil, but strong mutagens in its presence. We have now tested a wider range of materials for verapamil enhancement of mutagenicity, to include some of those to which persons on verapamil therapy might be exposed through life-style or occupation. Some verapamil enhancement of mutagenicity was seen with most mutagenic compounds including anticancer drugs, antiparasitic agents, one biological stain and one hair dye. A number of tricyclic antidepressants and biological stains were tested and found to be non-mutagenic. If these results extrapolate to mammalian cells, long-term verapamil therapy could potentially increase the effects of certain environmental mutagens.  相似文献   
999.
1000.
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