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   83823篇
  免费   4701篇
  国内免费   56篇
林业   2913篇
农学   2278篇
基础科学   565篇
  9200篇
综合类   14907篇
农作物   3089篇
水产渔业   3899篇
畜牧兽医   45780篇
园艺   883篇
植物保护   5066篇
  2018年   1037篇
  2017年   1173篇
  2016年   1085篇
  2015年   940篇
  2014年   1176篇
  2013年   3057篇
  2012年   2122篇
  2011年   2700篇
  2010年   1652篇
  2009年   1758篇
  2008年   2596篇
  2007年   2410篇
  2006年   2408篇
  2005年   2128篇
  2004年   2096篇
  2003年   2080篇
  2002年   1976篇
  2001年   2705篇
  2000年   2809篇
  1999年   2138篇
  1998年   815篇
  1997年   825篇
  1996年   809篇
  1995年   1019篇
  1994年   893篇
  1993年   844篇
  1992年   1933篇
  1991年   2084篇
  1990年   1927篇
  1989年   1940篇
  1988年   1825篇
  1987年   1930篇
  1986年   1976篇
  1985年   1874篇
  1984年   1485篇
  1983年   1300篇
  1982年   881篇
  1979年   1369篇
  1978年   1128篇
  1977年   979篇
  1976年   940篇
  1975年   983篇
  1974年   1272篇
  1973年   1299篇
  1972年   1234篇
  1971年   1147篇
  1970年   1088篇
  1969年   965篇
  1968年   835篇
  1967年   871篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
Fifty six dogs of mixed age and sex were acquired from farms in the Otago/Southland region, and maintained at the Hydatid Research Unit, Taieri, where 43 were each fed two Tueniu ovis cysts. All were bled fortnightly for six or 12 weeks. Coded sera were sent to Wallaceville Animal Research Centre for testing using ELISA, with antigen from T. ovis scoleces. Dog treatments were identified after all tests were complete. A discriminant level was derived from the mean absorbance value plus three standard deviations of 56 sera taken at time zero and 78 sera from serially bled uninfected dogs. None of these 134 sera registered as a false positive using this discriminant level. The data showed no significant deviation from normality, and the expected frequency of the occurrence of false positives is therefore less than 0.14%. Four weeks after infection 63% of dogs proved to be infected were serologically positive, rising to 78% after 6 weeks. When worms were removed by anthelmintic treatment, ELISA absorbance levels decreased. Four weeks after removal 70% of previously infected dogs remained positive, decreasing to 30% after 6 weeks. Six weeks after infection the sensitivity of the test was 78%, and the specificity 63%. However, if dogs with positive ELISA absorbance levels, but which did not purge worms, were regarded as having had worms, the respective figures would be 82% and 100%. The latter figures are similar to our previously published laboratory results. The test is of comparable efficiency to arecoline purgation for surveillance, and has the additional advantage of detecting infection in the majority of those dogs that have been infected for three weeks or more but fail to pass worms on purgation, and a substantial proportion of those infected dogs that were treated by their owners prior to presenting them for purgation in order to avoid detection of infection.  相似文献   
54.
55.
56.
57.
58.
The paper describes pathomorphological findings in two dogs and one cat with the intention to clarify whether these animals died by drowning. The investigations are supplemented by experimental results of water instillation into the lung to induce signs of emphysema aquosum post mortem. Additionally, histopathology of the skin lesions due to water exposition after death are demonstrated by systematic investigations of four different localizations for 10 days. Critical evaluation of the results and literature references in human forensic pathology indicate that post mortem findings as described in this paper, especially those of the so called "drowning lung" can be attributed to death by drowning.  相似文献   
59.
60.
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