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   1663725篇
  免费   156896篇
  国内免费   1747篇
  1822368篇
  2021年   18624篇
  2019年   16523篇
  2018年   19628篇
  2017年   18410篇
  2016年   29763篇
  2015年   44031篇
  2014年   52286篇
  2013年   78630篇
  2012年   50610篇
  2011年   42094篇
  2010年   48495篇
  2009年   48359篇
  2008年   38441篇
  2007年   37221篇
  2006年   40085篇
  2005年   41041篇
  2004年   39981篇
  2003年   37251篇
  2002年   34959篇
  2001年   52049篇
  2000年   49813篇
  1999年   45107篇
  1998年   27841篇
  1997年   27588篇
  1996年   26706篇
  1995年   24868篇
  1994年   24481篇
  1993年   23727篇
  1992年   37943篇
  1991年   36015篇
  1990年   34638篇
  1989年   35067篇
  1988年   32343篇
  1987年   30355篇
  1986年   28714篇
  1985年   30161篇
  1984年   28292篇
  1983年   24484篇
  1982年   23265篇
  1981年   22115篇
  1980年   20621篇
  1979年   23885篇
  1978年   21363篇
  1977年   20231篇
  1976年   18975篇
  1975年   19004篇
  1974年   19759篇
  1973年   20024篇
  1972年   17161篇
  1971年   15689篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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   
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.
999.
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   
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