全文获取类型
收费全文 | 1841489篇 |
免费 | 183628篇 |
国内免费 | 1829篇 |
专业分类
2026946篇 |
出版年
2021年 | 18552篇 |
2018年 | 19940篇 |
2017年 | 18736篇 |
2016年 | 29915篇 |
2015年 | 43807篇 |
2014年 | 51979篇 |
2013年 | 78186篇 |
2012年 | 53423篇 |
2011年 | 45848篇 |
2010年 | 49186篇 |
2009年 | 48804篇 |
2008年 | 41720篇 |
2007年 | 41153篇 |
2006年 | 43164篇 |
2005年 | 44064篇 |
2004年 | 43090篇 |
2003年 | 40200篇 |
2002年 | 37952篇 |
2001年 | 61764篇 |
2000年 | 60155篇 |
1999年 | 52834篇 |
1998年 | 28905篇 |
1997年 | 28803篇 |
1996年 | 27814篇 |
1995年 | 26015篇 |
1994年 | 25636篇 |
1993年 | 25031篇 |
1992年 | 45121篇 |
1991年 | 43349篇 |
1990年 | 42008篇 |
1989年 | 42016篇 |
1988年 | 38912篇 |
1987年 | 36807篇 |
1986年 | 34957篇 |
1985年 | 36307篇 |
1984年 | 33023篇 |
1983年 | 28673篇 |
1982年 | 25806篇 |
1981年 | 24459篇 |
1980年 | 22857篇 |
1979年 | 29589篇 |
1978年 | 25369篇 |
1977年 | 23859篇 |
1976年 | 22429篇 |
1975年 | 23284篇 |
1974年 | 24406篇 |
1973年 | 24555篇 |
1972年 | 21560篇 |
1971年 | 19523篇 |
1970年 | 17107篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
M R Miller 《The American journal of anatomy》1973,138(3):301-329
952.
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
953.
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
954.
A. J. Edwards J. D. Hamilton W. D. Nichol G. W. Taylor A. M. Dawson 《BMJ (Clinical research ed.)》1970,1(5692):342-345
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
955.
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
956.
Distribution and development of glutamine synthetase in the embryonic cerebral hemisphere 总被引:3,自引:0,他引:3
R Piddington 《The Journal of experimental zoology》1971,177(2):219-227
957.
P. Marion Handford 《Journal of applied microbiology》1974,37(4):559-570
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
958.
959.
960.
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