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   470689篇
  免费   49640篇
  国内免费   368篇
  520697篇
  2018年   4645篇
  2016年   6069篇
  2015年   8617篇
  2014年   9581篇
  2013年   13418篇
  2012年   15074篇
  2011年   14519篇
  2010年   9620篇
  2009年   8475篇
  2008年   12516篇
  2007年   12733篇
  2006年   12321篇
  2005年   11510篇
  2004年   11430篇
  2003年   10748篇
  2002年   10521篇
  2001年   20028篇
  2000年   20480篇
  1999年   16214篇
  1998年   5482篇
  1997年   5582篇
  1996年   5292篇
  1995年   5033篇
  1994年   4939篇
  1993年   4893篇
  1992年   12909篇
  1991年   12426篇
  1990年   12056篇
  1989年   11785篇
  1988年   11019篇
  1987年   10570篇
  1986年   10006篇
  1985年   10154篇
  1984年   8394篇
  1983年   7236篇
  1982年   5779篇
  1981年   5373篇
  1980年   4910篇
  1979年   8252篇
  1978年   6606篇
  1977年   6111篇
  1976年   5740篇
  1975年   6544篇
  1974年   7217篇
  1973年   7138篇
  1972年   6588篇
  1971年   5974篇
  1970年   5253篇
  1969年   5271篇
  1968年   4819篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
231.
232.
233.
234.
235.
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   
236.
237.
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   
238.
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   
239.
240.
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