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   196482篇
  免费   10831篇
  国内免费   169篇
林业   7829篇
农学   5727篇
基础科学   1316篇
  22802篇
综合类   36655篇
农作物   7385篇
水产渔业   9506篇
畜牧兽医   100723篇
园艺   2403篇
植物保护   13136篇
  2018年   2463篇
  2017年   2754篇
  2016年   2514篇
  2015年   2216篇
  2014年   2745篇
  2013年   7136篇
  2012年   5094篇
  2011年   6357篇
  2010年   4033篇
  2009年   4091篇
  2008年   6300篇
  2007年   5956篇
  2006年   5723篇
  2005年   5347篇
  2004年   5221篇
  2003年   5304篇
  2002年   5045篇
  2001年   6039篇
  2000年   5913篇
  1999年   4711篇
  1998年   1916篇
  1997年   1939篇
  1995年   2236篇
  1994年   1991篇
  1993年   1973篇
  1992年   4053篇
  1991年   4311篇
  1990年   4295篇
  1989年   4265篇
  1988年   3922篇
  1987年   4047篇
  1986年   4165篇
  1985年   3993篇
  1984年   3334篇
  1983年   2975篇
  1982年   2059篇
  1981年   1932篇
  1980年   1860篇
  1979年   3064篇
  1978年   2504篇
  1977年   2127篇
  1976年   1917篇
  1975年   2066篇
  1974年   2731篇
  1973年   2744篇
  1972年   2734篇
  1971年   2507篇
  1970年   2399篇
  1969年   2189篇
  1967年   1885篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
Sporidesmin-dosed hoggets which developed photosensitisation were shown to have enlarged adrenal glands and premature involution of the thymus. These sheep also developed high concentrations of plasma cortisol after the onset of photosensitisation. Sporidesmin-dosed sheep which did not show photosensitisation showed less or no adrenal associated changes.  相似文献   
932.
DNA fingerprinting with the probes 33.15 and alpha-globin 3'HVR has been used to resolve three cases of disputed paternity in dogs. For each pedigree it was necessary to establish which bands in the DNA fingerprints of the offspring were of paternal origin, and then establish which putative sire carried all these bands. In the first case, a litter of Rhodesian Ridgebacks, twelve DNA bands were informative in establishing paternity. In the second case, a litter of Afghan hounds, five DNA bands established paternity, Lastly, in a litter of Border collies, five DNA bands established paternity. In each case a single dog only sired the entire litter.  相似文献   
933.
934.
A 90-day finishing trial involving 144 feedlot heifers was conducted to compare the performance parameters and carcass characteristics of open heifers, therapeutically aborted heifers, and pregnant heifers. In the first 28 days of the trial, the aborted heifers had reduced (p < 0.05) feed intake (FI), average daily gain (ADG), and feed efficiency (FE) compared to pregnant and open heifers. Over the entire trial, on a live weight basis, the aborted group had reduced (p < 0.05) final weight, ADG, and FE compared to pregnant and open heifers. However, when the data were adjusted for total uterine weight, the aborted and open heifers had improved (p < 0.05) final weight, ADG, and FE compared to pregnant heifers. The aborted and open group had a higher (p < 0.05) carcass weight, rib eye area, dressing percentage, and cutability estimate compared to the pregnant heifers. The aborted group had lower (p < 0.05) carcass weight than the open heifers. Over the entire 90-day feeding period, there were no statistically significant differences among the groups with respect to feed intake (FI), average fat, grade fat, and carcass grades. Also, there were no significant health problems or mortality in any of the groups.

In the economic analysis, aborted heifers returned $26.41 per head more than pregnant heifers. Open heifers returned $39.94 per head more than aborted heifers, and $66.35 more than pregnant heifers. Thus, aborting feedlot heifers during the second trimester was determined to be a safe and cost effective management decision.

  相似文献   
935.
936.
937.
938.
939.
An adrenal tumour was diagnosed in a 12-year-old female cross-bred terrier. The dog was presented to the veterinary clinic because she had been gaining weight and had started urinating in the owners' house. Clinical findings included obesity, abdominal enlargement, thinning of the hair coat, seborrhoea sicca, and polydipsia and polyuria. The diagnosis was made by clinical pathology, endocrine function tests and abdominal radiography. Surgical removal of the neoplastic right adrenal gland resulted in resolution of the clinical signs, including regrowth of the hair coat.  相似文献   
940.
Guidelines for euthanasia of domestic animals by firearms   总被引:2,自引:2,他引:0       下载免费PDF全文
All animals that are to be killed, whether for food, for humane reasons, or because they are homeless, must receive a quick and painless death. In some smaller communities, veterinary or humane society expertise may not be readily available to humanely kill stray and unwanted animals. An alternative that provides for a humane death for the animal is by shooting. The following guidelines are intended to assist persons who must perform this usually distasteful task; they contain recommended techniques that will help to ensure that any animals killed by shooting will die in a humane way.  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