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   1631160篇
  免费   148644篇
  国内免费   1451篇
  2021年   18375篇
  2019年   16299篇
  2018年   19710篇
  2017年   18538篇
  2016年   29445篇
  2015年   43111篇
  2014年   51251篇
  2013年   77508篇
  2012年   48577篇
  2011年   40439篇
  2010年   48268篇
  2009年   48259篇
  2008年   37186篇
  2007年   36404篇
  2006年   38908篇
  2005年   40204篇
  2004年   39083篇
  2003年   36255篇
  2002年   34249篇
  2001年   47939篇
  2000年   45309篇
  1999年   41999篇
  1998年   27285篇
  1997年   26955篇
  1996年   26240篇
  1995年   24372篇
  1994年   24011篇
  1993年   23281篇
  1992年   35550篇
  1991年   34172篇
  1990年   32704篇
  1989年   33136篇
  1988年   30333篇
  1987年   29116篇
  1986年   27372篇
  1985年   28886篇
  1984年   27179篇
  1983年   24002篇
  1982年   22777篇
  1981年   21779篇
  1980年   20357篇
  1979年   23300篇
  1978年   21000篇
  1977年   19732篇
  1976年   19008篇
  1975年   19078篇
  1974年   19928篇
  1973年   20173篇
  1972年   17397篇
  1971年   15813篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
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   
994.
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   
995.
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   
996.
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   
997.
998.
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   
999.
1000.
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