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   36898篇
  免费   99篇
  国内免费   89篇
系统科学   335篇
丛书文集   686篇
教育与普及   72篇
理论与方法论   168篇
现状及发展   17044篇
研究方法   1392篇
综合类   16834篇
自然研究   555篇
  2013年   223篇
  2012年   473篇
  2011年   1046篇
  2010年   201篇
  2008年   558篇
  2007年   604篇
  2006年   664篇
  2005年   654篇
  2004年   743篇
  2003年   612篇
  2002年   549篇
  2001年   1018篇
  2000年   992篇
  1999年   630篇
  1992年   616篇
  1991年   514篇
  1990年   560篇
  1989年   500篇
  1988年   514篇
  1987年   541篇
  1986年   536篇
  1985年   699篇
  1984年   534篇
  1983年   473篇
  1982年   420篇
  1981年   410篇
  1980年   523篇
  1979年   1160篇
  1978年   964篇
  1977年   942篇
  1976年   736篇
  1975年   848篇
  1974年   1162篇
  1973年   973篇
  1972年   1028篇
  1971年   1177篇
  1970年   1537篇
  1969年   1198篇
  1968年   1111篇
  1967年   1162篇
  1966年   975篇
  1965年   765篇
  1964年   229篇
  1959年   428篇
  1958年   691篇
  1957年   511篇
  1956年   429篇
  1955年   402篇
  1954年   415篇
  1948年   286篇
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
301.
The antibodies against estrogen receptor were obtained after injecting Rabbits with a cytoplasmic receptor fraction isolated from Calf uterus. The estrogen receptor was partially proteolysed by the action of trypsin and subsequently purified by affinity chromatography (purification 4,000 to 10,000 fold, to a purity of 5-20%). The affinity of the antibody for the proteolysed receptor is KD approximately 1 nM and serum titres have reached values of approximately 50 nM. The values remained constant after the third injection. Preliminary results indicate that the antibody has approximately the same affinity for "native" cytoplasmic estrogen receptor from Calf uterus, as well as for the "trypsinized" forms of estrogen receptor isolated from Calf uterine cytosol and Hen oviduct nuclei.  相似文献   
302.
Comparing cytotoxicity of tubulosine and of six newly synthesized pseudo-tubulosines in the Allium test, we have characterized all the current features of protein inhibition. Nevertheless cytotoxicity of the six pseudotubulosines is much weaker. Furthermore, "floating poles anaphasis", a disturbance characteristic of the action of tubulosine, has been found with a lesser intensity with the other compounds.  相似文献   
303.
In 10 sibships of haemophilic A patients, every one including 1 haemophilic brother with an antibody to factor VIII and 1 haemophilic brother without antibody, pattern of HLA segregation was analysed. All sibships were HLA haploidentical or different and not HLA identical. This fact suggested a linkage between the major histocompatibility complex and an "Ir" gene to factor VIII.  相似文献   
304.
Summary The active calcium transport along the small intestine of adult rat was shown to exhibit daily rhythmic variations of considerable amplitude. Both the light-dark cycle and the time of food presentation acted as synchronizers of the rhythm observed.This work has been supported by Polish Academy of Sciences within the project MR II.1.1.6.  相似文献   
305.
G Paz  Z T Homonnai 《Experientia》1979,35(10):1412-1413
Streptozotocin diabetic rats were infertile as a result of decreased Leydig cell function of the testes. The major changes found were: decreased number of Leydig cells and their spontaneous secretion of testosterone. No change in the receptors to LH on the Leydig cells was observed. LH was found to be obligatory for the regulation of Leydig cell function and fertility.  相似文献   
306.
R Foa  M T Kramers  D Catovsky 《Experientia》1979,35(2):269-270
The levels of membrane alkaline phosphatase have been measured on different lymphocyte fractions from human peripheral blood separated on bovine serum albumin discontinuous gradients. The peak in enzyme activity was observed in a non-T-, non-B-cell fraction, rich in "null" lymphocytes; the lowest values were found in the fraction with the highest proportion of T-cells.  相似文献   
307.
J R Martinez  O H Petersen 《Experientia》1979,35(10):1343-1345
Using an automated system for the analysis of amylase, the release of this enzyme was compared in superfused parotid gland segments from control and reserpine treated rats. Stimulant-evoked amylase release was delayed and of smaller magnitude in the glands of the treated animals and a reduction of the transmembrane K+ gradient caused a smaller and short lasting reduction in Ach-evoked release of amylase in the glands from these animals.  相似文献   
308.
A thymic extract (TE) was prepared from supernatant of mice thymic epithelial cultures according to the purification of thymosin. TE and thymosin stimulated, in vitro, the immune response of mouse against deep red blood cells.  相似文献   
309.
Summary Physostigmine in a dose of 0.1 mg/kg i.v. expressly stimulated the oxygen uptake in the rat cerebral cortex. This effect was blocked by propranolol and seems be mediated by catecholamines. Since atropine also antagonized the stimulant effect of physostigmine, it appears that the action of physostigmine is primarily cholinergic and that the adrenergic effect is a secondary phenomenon. The higher dose of physostigmine (0.4 mg/kg i.v.) caused a depression of rat brain oxygen uptake.This work was supported by a grant from Serbian Republic Scientific Fund (ZMNU SR Srbija), Belgrade (Yugoslavia).The authors wish to acknowledge the skilful technical assistance of Lj. Krsti.  相似文献   
310.
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