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   8048篇
  免费   33篇
  国内免费   36篇
系统科学   77篇
丛书文集   57篇
教育与普及   4篇
理论与方法论   73篇
现状及发展   4284篇
研究方法   463篇
综合类   3032篇
自然研究   127篇
  2018年   69篇
  2017年   70篇
  2016年   71篇
  2013年   58篇
  2012年   179篇
  2011年   299篇
  2010年   87篇
  2008年   203篇
  2007年   206篇
  2006年   209篇
  2005年   200篇
  2004年   191篇
  2003年   166篇
  2002年   176篇
  2001年   194篇
  2000年   202篇
  1999年   131篇
  1992年   114篇
  1991年   90篇
  1990年   94篇
  1989年   77篇
  1988年   63篇
  1987年   100篇
  1986年   86篇
  1985年   152篇
  1984年   101篇
  1983年   79篇
  1982年   89篇
  1981年   78篇
  1980年   99篇
  1979年   212篇
  1978年   191篇
  1977年   222篇
  1976年   142篇
  1975年   170篇
  1974年   236篇
  1973年   190篇
  1972年   202篇
  1971年   219篇
  1970年   314篇
  1969年   245篇
  1968年   205篇
  1967年   251篇
  1966年   199篇
  1965年   135篇
  1964年   61篇
  1959年   74篇
  1958年   91篇
  1957年   88篇
  1954年   59篇
排序方式: 共有8117条查询结果,搜索用时 62 毫秒
961.
Summary Three alicyclic organic phosphonium salts with an oxo and a morpholino group were found to exhibit a substantial antiarrhythmic action. The different activity levels were tentatively related to the structural modifications that they could induce in the cardiac cell membrane.Acknowledgment. We thank M. Adamantidis for the pharmacological testing.  相似文献   
962.
Comparison of 5 antiinflammatory drugs and placebo in a double blind, short term, cross-over trial conducted in patients suffering from rheumatoid arthritis. 15 measurements were used and studied. With classical unidimensional statistical tests it was not possible to discriminate active drugs between them. Multidimensional analysis (correspondance analysis and discriminant analysis) are more sensitive and allow us to distinguish active drugs with only 11 criterion.  相似文献   
963.
Summary The content of blood in bone homogenates can be determined quantitatively by estimation of the haemin in the homogenate and in a sample of peripheral blood taken at the same time. Haem is completely split from the haemoglobin molecule by reaction with hydrochloric acid-acetone and converted to haemin, which can be analyzed spectrophotometrically. The blood content can be calculated from the amount of haemin in the homogenate in relation to that of the peripheral blood. This method is useful to determine the real amount of drugs in bone tissue.Acknowledgment. Thanks are due to Dr N. Walker and Dr H. Stuflesser, Balgrist, Orthopaedic University Hospital, Zürich, for kindly supplying the heads of femora removed at surgery.  相似文献   
964.
Summary An enhancement effect of mouse erythrocyte rosette forming (MERF) cells on the production of migration inhibitory factor, chemotactic factor for neutrophils and skin reactive factor in T-lymphocyte cultures stimulated with the purified protein derivative of tuberculin was observed. We consider it likely that the MERF cells, possessing the appropriate cell surface constituents to construct an immunogenic moiety, present antigen on their surfaces to elicit lymphokine production.This work was supported by the Scientific Research Council, Ministry of Health, Hungary, Code No. 421030401 1/s  相似文献   
965.
Summary Scavenging studies are supporting the notion that triplet radical cations are formed during the binding of the carcinogen N-acetoxy-2-acetylamino-fluorene to native DNA in vitro.This work was supported by Grant No.3305.78 of the Swiss National Science Foundation and by a grant from The Roche Research Foundation.  相似文献   
966.
Summary Myelin basic protein (MBP) isolated from bovine spinal cord caused a marked shape change reaction of human blood platelets which was not accompanied by the release reaction and not inhibited by methysergide and spiroperidol. Only those basic proteins, including MBP, which had previously shown to exert neuronal depolarisation also induced the shape change reaction. Therefore, these findings may extend the use of platelets as neuronal models.Acknowledgment. We thank Miss B. Gieux and Miss M. Handschin for skilful technical assistance.  相似文献   
967.
M J Pébusque  A Robaglia  R Se?te 《Experientia》1979,35(10):1370-1372
The superior cervical ganglia of the rat have been incubated in vitro for 1 h in basal medium Eagle (BME) with Hanks' salts, BME with Earle's salts, Kreb's solution and NCTC 109 medium. Comparison of the cell areas, established by a semi-automatic quantitative method, shows that the three former induce a 30--35% neuronal retraction, whereas NCTC 109 has no effect. Thus this latter medium seems the best one for studies using incubation of these cells.  相似文献   
968.
The distribution of fast, intermediate and slow renaturing fractions of Rhynchosciara americana DNA was examined in the polytene salivary gland chromosomes by in situ hybridization. Heterochromatic areas readily hybridized but hybrid formation in the euchromatin depended more on the repetitiveness of the RNA probe.  相似文献   
969.
Summary In rats undergoing unilateral extirpation of the pelvic ganglion, the adrenergic innervation disappeared on the ipsilateral side of the urinary bladder. It had reappeared after 6–9 weeks.This work was supported by grants from the Faculty of Medicine in Lund to M.E.  相似文献   
970.
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