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   1603217篇
  免费   146663篇
  国内免费   1428篇
  2021年   18201篇
  2019年   16189篇
  2018年   19485篇
  2017年   18319篇
  2016年   29210篇
  2015年   42744篇
  2014年   50856篇
  2013年   76948篇
  2012年   46360篇
  2011年   37727篇
  2010年   47408篇
  2009年   47575篇
  2008年   34638篇
  2007年   33788篇
  2006年   36505篇
  2005年   37828篇
  2004年   36683篇
  2003年   34036篇
  2002年   31959篇
  2001年   47794篇
  2000年   45200篇
  1999年   41889篇
  1998年   27136篇
  1997年   26833篇
  1996年   26138篇
  1995年   24285篇
  1994年   23916篇
  1993年   23196篇
  1992年   35481篇
  1991年   34098篇
  1990年   32612篇
  1989年   33055篇
  1988年   30224篇
  1987年   29012篇
  1986年   27320篇
  1985年   28820篇
  1984年   27084篇
  1983年   23941篇
  1982年   22697篇
  1981年   21689篇
  1980年   20283篇
  1979年   23227篇
  1978年   20921篇
  1977年   19656篇
  1976年   18921篇
  1975年   19025篇
  1974年   19875篇
  1973年   20121篇
  1972年   17359篇
  1971年   15771篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
983.
984.
985.
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   
986.
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   
987.
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   
988.
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   
989.
990.
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   
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