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   71001篇
  免费   3971篇
  国内免费   34篇
林业   3226篇
农学   2532篇
基础科学   478篇
  8709篇
综合类   11456篇
农作物   2612篇
水产渔业   3645篇
畜牧兽医   36669篇
园艺   909篇
植物保护   4770篇
  2018年   1054篇
  2017年   1131篇
  2016年   1057篇
  2015年   907篇
  2014年   1136篇
  2013年   2635篇
  2012年   2061篇
  2011年   2467篇
  2010年   1687篇
  2009年   1755篇
  2008年   2596篇
  2007年   2367篇
  2006年   2330篇
  2005年   2126篇
  2004年   2202篇
  2003年   2169篇
  2002年   2041篇
  2001年   2372篇
  2000年   2382篇
  1999年   1929篇
  1998年   912篇
  1997年   821篇
  1996年   786篇
  1995年   862篇
  1994年   843篇
  1993年   767篇
  1992年   1525篇
  1991年   1543篇
  1990年   1664篇
  1989年   1509篇
  1988年   1451篇
  1987年   1341篇
  1986年   1386篇
  1985年   1338篇
  1984年   1129篇
  1983年   1025篇
  1982年   628篇
  1979年   1005篇
  1978年   796篇
  1977年   721篇
  1976年   679篇
  1975年   721篇
  1974年   768篇
  1973年   833篇
  1972年   803篇
  1971年   749篇
  1970年   731篇
  1969年   745篇
  1967年   659篇
  1966年   631篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Cucumber Mosaic Virus, or Infectious Chlorosis, was found in alarming proportions in all the districts of Tamil Nadu on the ‘Robusta’ (Dwarf Cavendish) and ‘Poovan’ (Mysore) cultivais. The disease was transmitted only through suckers from the diseased gardens. Among the genotypes screened, the clones with ABB genomes showed complete field resistance.  相似文献   
103.
The interaction in water of neutral hydrocarbon and fluorocarbon surfaces, prepared by Langmuir-Blodgett deposition of surfactant monolayers, has been investigated. The attraction between these hydrophobic surfaces can be measured at separations of 70 to 90 nanometers and thus is of considerably greater range than previously found. Spontaneous cavitation occurred as soon as the fluorocarbon surfaces were brought into contact but occurred between the hydrocarbon surfaces only after separation from contact. The very long range forces measured are a consequence of the metastability of water films between macroscopic hydrophobic surfaces. Thus the hydrophobic interaction between macroscopic surfaces may not be related to water structure in the same way that the hydrophobic effect between nonpolar molecules is related to water structure.  相似文献   
104.
Fifty different mineral samples were tested as potential heterogeneous or epitaxial nucleants for four commonly crystallized proteins. It was found, by conventional protein crystallization techniques, that for each protein there was a set of mineral substrates that promoted nucleation of crystals at lower critical levels of supersaturation than required for spontaneous growth. Numerous examples, involving all four proteins, were observed of modification of crystal habit and, in some cases, unit cell properties promoted by the presence of the mineral nucleants. In at least one case, the growth of lysozyme on the mineral apophyllite, it was shown by lattice analysis and x-ray diffraction that the nucleation and growth of the protein crystal on the mineral was likely to involve a direct lattice match.  相似文献   
105.
106.
107.
108.
109.
A retrospective morbidity and mortality study was carried out on 125 case records of cattle involving xylazine/halothane anesthesia at the Ontario Veterinary College, Guelph between May 1979 and February 1983.  相似文献   
110.
William osler and comparative medicine   总被引:2,自引:2,他引:0       下载免费PDF全文
During the last thirty years of the nineteenth century, comparative medicine deeply influenced veterinary education in Montreal, New York and Philadelphia. Of the many physicians and veterinarians involved in this movement, Sir William Osler has attracted the most biographical and historical attention. However, his contributions to comparative medicine have been characterized inexactly, partly because of his later prominence as a clinician and partly because little has been written about the history of veterinary education in Quebec.

Osler's teaching and research in comparative medicine as well as his efforts to promote a veterinary profession are described and set alongside the work of other physicians and veterinarians who were his contemporaries. As a result, Osler's contributions to comparative medicine are seen to be many and important but by no means unique. Other Quebec veterinarians, including Duncan McEachran, Orphyr Bruneau, Victor T. Daubigny and J.A. Couture, and such physicians as T. Wesley Mills and J. George Adami made as many, and in some cases greater, contributions to veterinary education in Quebec than did Osler. That they have not received the degree of recognition that Osler has received reveals Osler's ability to represent values and ideals and draws attention to some essential features of late nineteenth-century comparative medicine.

  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