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   154133篇
  免费   11465篇
  国内免费   50篇
  165648篇
  2023年   766篇
  2022年   938篇
  2021年   1954篇
  2020年   1602篇
  2019年   1671篇
  2018年   3497篇
  2017年   3070篇
  2016年   4540篇
  2015年   6722篇
  2014年   6765篇
  2013年   8976篇
  2012年   10852篇
  2011年   10082篇
  2010年   6359篇
  2009年   5118篇
  2008年   8053篇
  2007年   7955篇
  2006年   7286篇
  2005年   7251篇
  2004年   6938篇
  2003年   6198篇
  2002年   5531篇
  2001年   3512篇
  2000年   3403篇
  1999年   2992篇
  1998年   1279篇
  1997年   1115篇
  1996年   1091篇
  1995年   972篇
  1994年   981篇
  1993年   829篇
  1992年   2111篇
  1991年   1921篇
  1990年   1743篇
  1989年   1665篇
  1988年   1595篇
  1987年   1403篇
  1986年   1312篇
  1985年   1365篇
  1984年   1207篇
  1983年   976篇
  1982年   748篇
  1981年   738篇
  1980年   668篇
  1979年   993篇
  1978年   787篇
  1977年   676篇
  1975年   708篇
  1974年   728篇
  1973年   730篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Liver microsomal concentration of cytochrome P.450 is increased in animals which are fed diets rich in polyunsaturated fatty acids. On the other hand, the effects of phenobarbital are more important when the dietary fat is more unsaturated. The unsaturation index in liver microsomal phosphatidylcholines depends on the unsaturation of the dietary fats. The treatment with phenobarbital constantly results in a decrease of the unsaturation index of fatty acids both in lecithins and cephalins. The importance of the liver microsomal cytochrome P.450 increase and the importance of the unsaturation index decrease in liver microsomal lecithins, both promoted by phenobarbital, are in good agreement.  相似文献   
63.
The author describes the history of the concept of depression in modern psychiatry from the end of the Age of Enlightenment until today in three parts. In the first period (1793–1854), the opposition of general delusion (mania) and partial delusion (melancholia) prevails, without the problem of changes of the affective state being an issue. Only with the work of J. Guislain, and later of W. Griesinger, does the concept of mood disorders become a categorical form in mental pathology with the idea of psychological pain. The second period (1854–1926) is distinguished firstly by the works of J.P. Falret on circular insanity, and then those of V. Magnan, J. Ségnan, J. Séglas et Ph. Chaslin in France and E. Kraepelin in Germany. This period is characterized by the classical construction of periodic manicdepressive psychosis and takes into account the opposition of mania and melancholia. In the third period (1926–1977), the influences of phenomenology, psychoanalysis and structuralism predominate. Gradually melancholia loses its place at the core of this field, in favour of the concept of depression and this change now characterizes contemporary psychiatry.  相似文献   
64.
To obtain insight into the role of lipids in the translocation of extramitochondrially synthesized proteins, we studied the ability of apocytochrome c to pass lipid bilayers. With polyacrylamide gel electrophoresis, the digestion of externally added apocytochrome c by trypsin, enclosed in lipid vesicles, was followed. The experiments demonstrate that apocytochrome c is able to pass a lipid barrier and this process shows both a lipid- and protein specificity. The most probable molecular mechanisms involved in this phenomenon are discussed.  相似文献   
65.
66.
The anti-DNP response to DNP-BGG is substantially suppressed in guinea pigs sensitized to DNCB. The degree of antibody suppression varies with the mode of skin sensitization and with the degree of conjugation of the challenging immunogen. Suppression of the anti-HSA response was also induced by the prior injection of CFA.  相似文献   
67.
68.
69.
I.J.A. Urban  D. de Wied 《Life sciences》1982,31(22):2417-2424
The influence of systemically administered Des-Tyr1-α-endorphin (DTαE), Des-Tyr1-γ-endorphin (DTγE) and haloperidol on electroencephalographic (EEG) activity of the lateral septum complex (LSC) and the frontal cortex was studied in male rats. DTαE (2 μg) significantly increased whereas DTγE (10 μg) significantly decreased the amounts of activity in the 5 Hz band. In addition, DTαE promoted production of 15 - 20 Hz activity, while DTγE decreased the amount of 20 - 30 Hz activity. EEG activity exhibited a marked variability which persisted throughout the recording session following administration of the peptides. Haloperidol markedly decreased the proportion of 10 - 15 Hz activity. The alterations in EEG of the frontal cortex were similar to those in LSC but less pronounced. The differences in the time course and frequency bands affected suggest that the effects of peptides and haloperidol on EEG activity of LSC are not mediated by the same mechanisms.  相似文献   
70.
Following arteriolar occlusion, tissue oxygen concentration decreases and anoxic tissue eventually develops. Although anoxia first appears in the region most distal to the capillary at the venous end, it eventually spreads throughout the entire region of supply. In this paper the changing oxygen concentration, from the time of occlusion until the tissue is entirely anoxic, is examined mathematically. The equations governing oxygen transport to tissue are solved by iterating a nonlinear integral equation. This solution is valid until anoxia first appears. After anoxia develops it is necessary to solve a moving boundary problem. This is done using the method of matched asymptotic expansions, and accurate solutions are obtained for a wide range of physiological conditions.  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