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   1370261篇
  免费   128128篇
  国内免费   1449篇
  2021年   17864篇
  2019年   16201篇
  2018年   17817篇
  2017年   16530篇
  2016年   28149篇
  2015年   42486篇
  2014年   50526篇
  2013年   76806篇
  2012年   37202篇
  2011年   25865篇
  2010年   43686篇
  2009年   45114篇
  2008年   24493篇
  2007年   22406篇
  2006年   27608篇
  2005年   28648篇
  2004年   27592篇
  2003年   25446篇
  2002年   23486篇
  2001年   36094篇
  2000年   33493篇
  1999年   32912篇
  1998年   25789篇
  1997年   25756篇
  1996年   25210篇
  1995年   23390篇
  1994年   23149篇
  1993年   22413篇
  1992年   28827篇
  1991年   27392篇
  1990年   25682篇
  1989年   26429篇
  1988年   24218篇
  1987年   23089篇
  1986年   21952篇
  1985年   23822篇
  1984年   23385篇
  1983年   20729篇
  1982年   21115篇
  1981年   20155篇
  1980年   18922篇
  1979年   19530篇
  1978年   18372篇
  1977年   17559篇
  1976年   16701篇
  1975年   16143篇
  1974年   16555篇
  1973年   16824篇
  1972年   14261篇
  1971年   13119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
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   
942.
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   
943.
944.
945.
946.
947.
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   
948.
949.
Pieces of brain are fixed in formalin ammonium bromide for about 4 days at room temperature, and given the following treatment: After washing, dehydrating and clearing, embed in paraffin, section and mount. Deparaffinize sections and pass through graded alcohols to water. Sensitize in 5% sodium sulfite for 2 hours, wash in distilled water and impregnate with silver diamminohydroxide solution 2-5 minutes at room temperature. Reduce in 2% formalin, wash in distilled water and tone in gold chloride. Fix in 5% hypo, counterstain with 1% picric acid, dehydrate and cover in balsam. Equally good results are obtained by impregnating with Hortega's strong silver carbonate. The microglia, oligodendroglia, fibrous and protoplasmic astrocytes in the cat, rabbit, newborn and adult human are successfully stained by this method.  相似文献   
950.
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