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   34119篇
  免费   1359篇
  国内免费   10篇
林业   2327篇
农学   1517篇
基础科学   269篇
  5837篇
综合类   4386篇
农作物   1635篇
水产渔业   1897篇
畜牧兽医   14127篇
园艺   959篇
植物保护   2534篇
  2019年   273篇
  2018年   1620篇
  2017年   1723篇
  2016年   974篇
  2015年   390篇
  2014年   480篇
  2013年   999篇
  2012年   1204篇
  2011年   2083篇
  2010年   1899篇
  2009年   1674篇
  2008年   1775篇
  2007年   1968篇
  2006年   833篇
  2005年   830篇
  2004年   700篇
  2003年   792篇
  2002年   666篇
  2001年   825篇
  2000年   831篇
  1999年   639篇
  1998年   278篇
  1997年   287篇
  1996年   230篇
  1995年   262篇
  1993年   254篇
  1992年   465篇
  1991年   517篇
  1990年   437篇
  1989年   434篇
  1988年   424篇
  1987年   412篇
  1986年   363篇
  1985年   391篇
  1984年   339篇
  1983年   290篇
  1982年   244篇
  1979年   384篇
  1978年   290篇
  1977年   308篇
  1976年   299篇
  1975年   318篇
  1974年   332篇
  1973年   304篇
  1972年   291篇
  1971年   247篇
  1969年   292篇
  1968年   287篇
  1967年   333篇
  1966年   304篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
A serological study of intermediate hosts (cattle, sheep, goats and swine) of Echinococcus granulosus was carried out by means of the indirect haemaglutination (IHA) and flocculation with latex (LA) tests, relating them with the organs invaded, and the fertility and viability of the cysts.In cattle a sensitivity of 75% and 21.05% of non-specific reactions was given by IHA, while the LA gave 66.7 and 17.54%, respectively. In the sheep, the IHA gave 79.16 and 20%, and the LA, 75 and 15%. In the goat, the IHA gave 76 and 22%, and the LA 71.43 and 16%. Finally, in the pig, the IHA gave 75 and 22%, and the LA, 66.6 and 14.16%.The IHA was more sensitive in detecting hepatic cysts in the cow, and pulmonary cysts in the goat, while in the sheep and the pig there were no significant differences. The LA was more sensitive in detecting hepatic cysts in the cow, goat and pig, while there were no significant differences in sheep.The differences in serum titers by the IHA and the LA tests with respect to the viability and the fertility of the cysts in the hosts, were not significant.  相似文献   
992.
Reported in this paper are the preparation, testing and application of two live vaccines against anthrax in the USSR. They were STI live vaccine in liquid and lyophilised forms and GHKI live vaccine in lyophilised form. Official tests for purity were conducted, using growth factors of cultures, whereas harmlessness was tested on rabbit and effectiveness on guinea-pig and later on sheep, after some five years had elapsed. Quantitative methods by which to test the effectiveness of VGNKI are now being prepared. Immunisation for prophylaxis or emergency are undertaken, depending on epizootiological situations. Major importance is ascribed to keeping, feeding, general nutrition and performance, latent infections, and meteorological factors which can all be of impact on immunogenicity and postvaccinal complications. Anthrax has been eliminated in the USSR, with only few sporadic outbreaks left, owing to immunisation and complementary action in veterinary hygiene.  相似文献   
993.
This study determined that streptococci were the etiological agents responsible for a high percentage of breeding sows experiencing infertility and abortions.No isolations of virus were obtained from fetuses, or placentae. There was no positive serology obtained from sows that aborted when tested for evidence of virus, leptospira, brucella, and eperythrozoon antibodies. Streptococci were the predominant isolates obtained from the genito-urinary tract of sows and boars. Cultures were taken from 75 sows and 46 (61%) yielded hemolytic streptococci; 27 of these streptococci belonged to a specific serogroup. Of the 75 sows studied, 46 were infected, and of these, nine aborted, 14 were infertile, and 23 farrowed normally. There was a significantly (P < 0.02) higher number of sows that had abortions or were infertile in the infected group. A random sample of 18 sows given penicilin therapy indicated a significant benefit from treatment (P < 0.02) in the reproductive performance of infected animals.Twelve out of 16 boars yielded hemolytic streptococci with seven isolated being of a specific serogroup.The percentage distribution of all streptococci isolates belonging to a specific serogroup was 63.4% group C, 22% group D, and 7.3% each fooup A and G.  相似文献   
994.
995.
Six canine long bone fractures with delayed or non-union were investigated using osteomedullography. The contrast medium crossed the fracture (positive osteomedullography) in four cases. All contrast medium remained in the distal fragment (negative osteomedullography) in two cases. The fractures with the negative finding were operated upon using bone grafts. Conservative fracture treatment using transfixation or plaster cast was continued in the positive cases. All the fractures united from 9 to 15 weeks after the examination and treatment. Osteomedullography proved to be a reliable method for identifying which non-union fractures require further operative treatment for healing.  相似文献   
996.
997.
998.
999.
1000.
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