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   1790262篇
  免费   173526篇
  国内免费   1809篇
  1965597篇
  2021年   18496篇
  2019年   16361篇
  2018年   19936篇
  2017年   18833篇
  2016年   29915篇
  2015年   43797篇
  2014年   51895篇
  2013年   78185篇
  2012年   52070篇
  2011年   44252篇
  2010年   48964篇
  2009年   48655篇
  2008年   40283篇
  2007年   39336篇
  2006年   41705篇
  2005年   42616篇
  2004年   41670篇
  2003年   38808篇
  2002年   36674篇
  2001年   60001篇
  2000年   58169篇
  1999年   51361篇
  1998年   28732篇
  1997年   28535篇
  1996年   27504篇
  1995年   25708篇
  1994年   25323篇
  1993年   24670篇
  1992年   43562篇
  1991年   41738篇
  1990年   40398篇
  1989年   40558篇
  1988年   37395篇
  1987年   35390篇
  1986年   33408篇
  1985年   34651篇
  1984年   31640篇
  1983年   27454篇
  1982年   25024篇
  1981年   23579篇
  1980年   22146篇
  1979年   27829篇
  1978年   24158篇
  1977年   22641篇
  1976年   21263篇
  1975年   21878篇
  1974年   22903篇
  1973年   23124篇
  1972年   20068篇
  1971年   18253篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
The capillaries of the cardiac muscle were investigated in the goat by means of light microscopy, transmission electron microscopy and scanning electron microscopy, and the following results were obtained. The capillaries of the working cardiac muscles were numerous, arranged mainly parallel to the long axis of muscle cells and formed dense elongated networks. On the contrary, those of the terminal Purkinje fibers were relatively few in number, oriented in various directions and formed loose and circularly meshed networks surrounding the fibers. Such findings were discussed in correlation with the physiology and functional morphology of various types of the cardiac muscle cells.  相似文献   
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.
979.
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   
980.
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