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   405154篇
  免费   46233篇
  国内免费   371篇
  451758篇
  2016年   3827篇
  2015年   5779篇
  2014年   6761篇
  2013年   9675篇
  2012年   10736篇
  2011年   10834篇
  2010年   7180篇
  2009年   6725篇
  2008年   9591篇
  2007年   10078篇
  2006年   9545篇
  2005年   9294篇
  2004年   9221篇
  2003年   8789篇
  2002年   8713篇
  2001年   18311篇
  2000年   18826篇
  1999年   15016篇
  1998年   5062篇
  1997年   5262篇
  1996年   4892篇
  1995年   4702篇
  1994年   4638篇
  1993年   4638篇
  1992年   12124篇
  1991年   11691篇
  1990年   11353篇
  1989年   11007篇
  1988年   10394篇
  1987年   9900篇
  1986年   9404篇
  1985年   9490篇
  1984年   7854篇
  1983年   6751篇
  1982年   5381篇
  1981年   5018篇
  1980年   4561篇
  1979年   7661篇
  1978年   6177篇
  1977年   5674篇
  1976年   5357篇
  1975年   6003篇
  1974年   6643篇
  1973年   6589篇
  1972年   6095篇
  1971年   5520篇
  1970年   4766篇
  1969年   4724篇
  1968年   4303篇
  1967年   3620篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
221.
222.
223.
224.
225.
The capillaries of the cardiac muscle were investigated in the goat by means of light microscopy, transmission electron microscopy and scanning electron microscopy, and the following results were obtained. The capillaries of the working cardiac muscles were numerous, arranged mainly parallel to the long axis of muscle cells and formed dense elongated networks. On the contrary, those of the terminal Purkinje fibers were relatively few in number, oriented in various directions and formed loose and circularly meshed networks surrounding the fibers. Such findings were discussed in correlation with the physiology and functional morphology of various types of the cardiac muscle cells.  相似文献   
226.
227.
At Birmingham University since 1966 the major medical examinations began to be replaced by a process of continuous assessment. This is based on fairly frequent tests, usually at the end of each course, including short essay questions, multiple-choice questions, and tests of ability in wards and laboratory. At the end of the first final-year course 96 students underwent assessment. Of these 77 passed; 19 were referred for re-examination, of whom a further 12 passed subsequently. The scheme was found suitable by both teachers and external examiners.  相似文献   
228.
Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar-bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2-n-octyl-4-isothiazole-3-one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC50 values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3-hydroxy-5-methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC50 of 214 μg a.i./ml. Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate-methyl, dichlozoline and Ohric gave 80–90% control of damping-off of mung bean seedlings. A single soil drench with thiophanate-methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate-methyl was used as a post-inoculation soil drench than when benomyl or chloroneb were used.  相似文献   
229.
230.
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