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   1601581篇
  免费   158308篇
  国内免费   1577篇
  1761466篇
  2021年   18316篇
  2019年   16344篇
  2018年   18399篇
  2017年   17063篇
  2016年   28804篇
  2015年   43393篇
  2014年   51555篇
  2013年   77826篇
  2012年   46140篇
  2011年   35993篇
  2010年   46166篇
  2009年   46799篇
  2008年   33966篇
  2007年   32503篇
  2006年   36271篇
  2005年   36670篇
  2004年   36072篇
  2003年   33493篇
  2002年   31408篇
  2001年   48440篇
  2000年   46313篇
  1999年   42106篇
  1998年   27417篇
  1997年   27403篇
  1996年   26657篇
  1995年   24824篇
  1994年   24500篇
  1993年   23887篇
  1992年   36145篇
  1991年   34412篇
  1990年   33144篇
  1989年   33449篇
  1988年   30641篇
  1987年   29769篇
  1986年   27850篇
  1985年   29460篇
  1984年   27704篇
  1983年   24374篇
  1982年   23429篇
  1981年   22218篇
  1980年   20785篇
  1979年   24296篇
  1978年   21758篇
  1977年   20500篇
  1976年   19499篇
  1975年   19472篇
  1974年   20393篇
  1973年   20577篇
  1972年   17715篇
  1971年   16402篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
973.
Five cases of coincident salmonellosis and ulcerative colitis are described. In three the diagnostic combination was recognized late. If corticosteroid therapy is given for the colitis once the combination is recognized, then simultaneous systemic antibiotic cover is advisable. One of the five patients died during corticosteroid therapy alone with salmonella septicaemia due to a usually non-invasive organism.  相似文献   
974.
Seven patients with “coeliac axis compression syndrome” are reported. Five were treated surgically, but only two did well. A survey of 200 healthy adults showed epigastric bruits in 6·5%; only one of these had dyspepsia, though dyspepsia was present in 12·5% overall.Caution is urged in attributing a causal relationship between coeliac axis compression and pain and in proceeding to arteriography when compression is suspected on clinical grounds.  相似文献   
975.
From experience in the Northampton/Kettering area 9 to 10% of all patients in a general hospital requiring care in an intensive therapy unit were aged 12 years or under. Fifty-nine children were admitted to the intensive therapy unit of Northampton General Hospital between May 1967 and August 1969. Of these, 22 had been injured in road traffic accidents, five were surgical emergencies, five had meningitis, four status epilepticus, and four respiratory infections.All of the 30 families interviewed were in favour of their child being admitted to the unit, and none considered that the experience had had any lasting adverse psychological effect on the child. It is suggested that certain carefully selected child patients do benefit from the facilities of an intensive therapy unit, and for this reason such units must be designed, equipped, and staffed with this in mind.  相似文献   
976.
S ummary . This paper describes the development and use of a selective diagnostic medium for the detection and enumeration of Clostridium perfringens in foods. The medium gives higher counts of Cl. perfringens and fewer false positives than existing media.  相似文献   
977.
978.
Morphogenesis and Homology in Arthropod Limbs   总被引:1,自引:0,他引:1  
Arthropods exhibit highly diverse limb morphologies rangingfrom unbranched walking legs to multibranched swimming paddles.Understanding morphogenesis in structurally diverse limbs canbe useful for ascertaining homologies between limbs. Structurallysimilar limbs have been produced by different evolutionary modificationsof morphogenesis in certain cases. Whereas it is easy to supportthe claim that whole arthropod limbs are homologous structures,I demonstrate that it is not always possible to draw well-foundedhomologies between parts of different limbs. This result isimportant with regard to general models of appendage developmentand evolution in arthropods because it clarifies contradictoryexplanations based exclusively on gene expression data.  相似文献   
979.
980.
Genetic programming for development in Drosophila   总被引:2,自引:0,他引:2  
  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