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   17766篇
  免费   39篇
  国内免费   55篇
系统科学   136篇
丛书文集   204篇
教育与普及   37篇
理论与方法论   78篇
现状及发展   7522篇
研究方法   867篇
综合类   8697篇
自然研究   319篇
  2013年   116篇
  2012年   290篇
  2011年   602篇
  2010年   119篇
  2008年   373篇
  2007年   348篇
  2006年   362篇
  2005年   372篇
  2004年   394篇
  2003年   323篇
  2002年   298篇
  2001年   527篇
  2000年   503篇
  1999年   356篇
  1992年   336篇
  1991年   240篇
  1990年   256篇
  1989年   247篇
  1988年   245篇
  1987年   251篇
  1986年   243篇
  1985年   338篇
  1984年   281篇
  1983年   182篇
  1982年   200篇
  1981年   175篇
  1980年   220篇
  1979年   505篇
  1978年   359篇
  1977年   372篇
  1976年   327篇
  1975年   369篇
  1974年   475篇
  1973年   439篇
  1972年   445篇
  1971年   510篇
  1970年   650篇
  1969年   545篇
  1968年   563篇
  1967年   512篇
  1966年   473篇
  1965年   349篇
  1964年   112篇
  1959年   191篇
  1958年   340篇
  1957年   232篇
  1956年   222篇
  1955年   179篇
  1954年   209篇
  1948年   165篇
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
121.
Summary Captopril in vitro (50–500 g/ml) increased3H-TdR incorporation in unstimulated and mitogen-stimulated cultures of rat lymphocytes. Unseparated spleen and lymph node cells of rats orally treated with captopril (50 mg/kg/day×4) showed decreased basal and mitogen stimulated3H-TdR incorporation. The removal of macrophages abrogated this inhibitory effect. Leucine aminopeptidase activity of macrophages was reduced — in vivo and in vitro — by captopril.Acknowledgments. The authors thank the Squibb Institute for Medical Research for the gift of Captopril. The excellent technical assistance of Ms B. Hasselriis, Ms B. Rumler and Ms E. Greve Petersen is gratefully acknowledged.  相似文献   
122.
123.
Summary The biochemical changes in the hemolymph and tissues were followed during regeneration of the optic tentacles of the snailCryptozona ligulata (Pulmonata-Stylommatophora). There is a remarkable increase in total carbohydrates in hemolymph and tissues and glycogen in tissues at the expense of free amino acids and fatty acids. It is clear that ablation of the optic tentacles stimulates carbohydrate synthesis through glyconeogenic routes. The optic tentacles regenerate completely in 18–21 days.  相似文献   
124.
Summary The defense secretion of soldiers ofReticulitermes lucifugus has been shown to contain, predominantly, (R)-(–)-(E,E)-geranyllinalool together with germacrene A and -farnesene.This report covers part of a collaborative study with J.-L. Clément, Lab. d'Evolution, Université P. et M. Curie, Paris, to whom we are grateful for supplies of material and discussions. We also thank Dr O.T. Jones for collections ofReticulitermes lucifugus.  相似文献   
125.
Summary In 2 independent samples of low-birth-weight infants the proportion of females and homozygotes for a series of polymorphic systems was higher in light-for-dates than in preterm babies. The observation seems to give support to the hypothesis that homozygosity for normal polymorphisms may decrease in general intrauterine growth rate. Since it is known that survival rate is strongly related to birth weight, a correlation between growth retardation and homozygosity may have a major role in the maintenance of such polimorphisms.We thank Prof. L. Ginzburg for helpful comments.  相似文献   
126.
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   
127.
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   
128.
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   
129.
Three acidic polysaccharide (AP) fractions and the prostaglandin-like substances (PLS) isolated from P. acnes were investigated regarding their chemotactic activities on polymorphonuclear leukocytes. Both AP's and PLS induced a significant chemotatic response, which suggests their involvement in inflammatory acne vulgaris.  相似文献   
130.
It was shown that, in physiological concentrations, insulin enhances, in vitro, the immunological phagocytosis of sensitized sheep erythrocytes by cultured mouse peritoneal macrophages. Insulin seems to stimulate macrophage phagocytosis as a cholinomimetic agonist by increasing the intracellular levels of cyclic GMP.  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