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   11731篇
  免费   53篇
  国内免费   71篇
系统科学   69篇
丛书文集   29篇
教育与普及   21篇
理论与方法论   32篇
现状及发展   5469篇
研究方法   591篇
综合类   5516篇
自然研究   128篇
  2012年   207篇
  2011年   304篇
  2010年   78篇
  2009年   75篇
  2008年   205篇
  2007年   244篇
  2006年   250篇
  2005年   241篇
  2004年   207篇
  2003年   200篇
  2002年   253篇
  2001年   436篇
  2000年   430篇
  1999年   289篇
  1992年   236篇
  1991年   196篇
  1990年   219篇
  1989年   191篇
  1988年   201篇
  1987年   221篇
  1986年   190篇
  1985年   252篇
  1984年   228篇
  1983年   172篇
  1982年   177篇
  1981年   184篇
  1980年   171篇
  1979年   408篇
  1978年   340篇
  1977年   251篇
  1976年   290篇
  1975年   260篇
  1974年   272篇
  1973年   224篇
  1972年   244篇
  1971年   310篇
  1970年   375篇
  1969年   255篇
  1968年   308篇
  1967年   295篇
  1966年   250篇
  1965年   179篇
  1964年   101篇
  1959年   90篇
  1958年   162篇
  1957年   100篇
  1956年   91篇
  1955年   85篇
  1954年   77篇
  1948年   64篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
Summary Pronase and -chymotrypsin digested the major glycoprotein in the human and mouse red cell membranes and in SDS gel electrophoresis the glycoprotein disappeared accompanied by the appearance of a new band of lower mol.wt. However in the membranes of sheep, rat and rabbit, no digestion was demonstrated. The effects of pronase on anion permeability were almost identical for human and animal erythrocytes.  相似文献   
62.
Summary Neurohypophyseal blood flow increases in water-deprived rats. This increase is independent of vasopressin release, since it occurs even in rats with hereditary defect of hypothalamic vasopressin synthesis.Acknowledgment. The technical assistance of D. Vilimovská is acknowledged.  相似文献   
63.
Summary Abnormal-8-tetrahydrocannabidiol (ABN-8-THC) failed to elicit central nervous system and cardiovascular effects in laboratory animals. Abnormal-cannabidiol (ABN-CBD) was also devoid of overt behavioral effects but produced marked hypotension with only slight bradycardia in anesthesized dogs.Acknowledgment. This work was supported by NIDA (grant No. DA-00574-01 and DA-00490) and Virginia Heart Society (grant No. RR-05697)  相似文献   
64.
Summary Naja mossambica pallida venom administered i.v. (300 /kg) produces an initial brief fall in blood pressure, due to a direct myocardial depressant effect, and a sustained fall due to central depressant effect.This study was supported by University of Nairobi research grants (670–376). We also thank Mr E. Njogu for photographic assistance.  相似文献   
65.
Proton pump coupled to cytochrome c oxidase in mitochondria.   总被引:1,自引:0,他引:1  
M K Wikstrom 《Nature》1977,266(5599):271-273
  相似文献   
66.
Summary The free radical oxidation of 1 and 6-tetrahydrocannabinol has been examined by spin trapping techniques and intermediates that would lead to cannabinol have been trapped. The 1st step in the oxidation of 1-THC involves the removal of 3-H, while for 6-THC, either 2-H or 5-H. Intermediates were isolated which could be pyrolysed to the diene and cannabinol.  相似文献   
67.
Summary The transmitter substance released by nigro-thalamic fibres is proposed to be -aminobutyric acid, since picrotoxin blocked nigra-evoked monosynaptic inhibition of thalamic neurons.Supported by grants Nos 212009 and 311410 from Ministry of Education of Japan.The authors wish to thank Dr Marjorie Anderson, University of Washington, Seattle, for improving the English.  相似文献   
68.
Summary 4-Isothiocyanato-4-nitrodiphenylamine possessed anthelmintic activity againstNippostrongylus dubius andHymenolepis nana in mice andH. diminuta in rats as determined by both egg counts and recovery of parasites at autopsy. No activity was detected against the cestode,Spirometra mansonoides, in cats.This investigation was supported in part by grants AI-10512 and AI-09483 from the National Institutes of Health. The authors are indebted to Dr P.P. Weinstein for providing animals infected withSpirometra mansonoides.  相似文献   
69.
    
Summary InTambourissa religiosa (Monimiaceae), the flowers are pollinated at a hyperstigma formed by the mouth of the floral cup, and not at the carpels. This is an extraordinary feature in angiosperms.I thank Professor Dr W. Rauh, Institut für Systematische Botanik und Pflanzengeographie der Universität Heidelberg, for providing material from his green house collection (W. Rauh, No. M 138, coll. 1959) and Dr Christa Güssefeld-Schneider for fixing pollinated flowers.  相似文献   
70.
The enzymes which were extracted by autodigestion from the microsomal fractions of the pig kidney, liver and submaxillary gland and from the serum showed an immunochemical identity by a double immunodiffusion test. But the kidney enzyme had a different pI-value from the pI-values of the enzymes of other organs.  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