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   63727篇
  免费   3595篇
  国内免费   242篇
林业   3322篇
农学   2614篇
基础科学   414篇
  8297篇
综合类   7555篇
农作物   2448篇
水产渔业   3532篇
畜牧兽医   34761篇
园艺   853篇
植物保护   3768篇
  2020年   512篇
  2019年   593篇
  2018年   1073篇
  2017年   1169篇
  2016年   1156篇
  2015年   973篇
  2014年   1151篇
  2013年   2548篇
  2012年   2057篇
  2011年   2471篇
  2010年   1656篇
  2009年   1572篇
  2008年   2284篇
  2007年   2297篇
  2006年   2151篇
  2005年   1993篇
  2004年   1868篇
  2003年   1919篇
  2002年   1851篇
  2001年   2627篇
  2000年   2364篇
  1999年   1855篇
  1998年   720篇
  1997年   664篇
  1996年   635篇
  1995年   713篇
  1994年   613篇
  1993年   592篇
  1992年   1308篇
  1991年   1432篇
  1990年   1492篇
  1989年   1374篇
  1988年   1275篇
  1987年   1265篇
  1986年   1195篇
  1985年   1134篇
  1984年   959篇
  1983年   747篇
  1982年   549篇
  1979年   820篇
  1978年   644篇
  1976年   544篇
  1975年   525篇
  1974年   661篇
  1973年   625篇
  1972年   660篇
  1971年   637篇
  1970年   601篇
  1969年   552篇
  1967年   509篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
Blood samples from 433 periparturient recumbent cows submitted by veterinary practitioners to Ruakura Animal Health Laboratory during 1983 and 1984 were analysed and results related to whether cows recovered, died or were euthanased. Generally cows were sampled only once and the time varied from 15 minutes to 20 days after becoming recumbent. During 1983 serum calcium, magnesium, phosphorus, creatine phosphokinase (CK), aspartate amino transferase (AST), glutamate dehydrogenase (GDH), gamma glutamyl transferase (GGT) were analysed. In 1984 serum urea, creatinine, fibrinogen and haematological examination (haemoglobin, haematocrit, total and differential white cell counts) were added to the panel. Overall 39% of cows recovered, 30% died and 32% were destroyed. Precalving cows had 111% more deaths and 7% less survivors than postcalving recumbent cows (P<0.1). There was little difference (3%) in euthanasia prevalence. Tests that were most useful in predicting a lack of recovery were serum urea and muscle enzymes. Using these tests and duration of recumbency when sampled a model was produced to predict the probability of recovery from 254 cases.  相似文献   
104.
105.
106.
The impairment of fluid, electrolyte and acid-base status which is observed in calves and juvenile cattle as a result of ileus and subileus is not only dependent on form and site of the obstruction, but is also influenced considerably by the duration of the condition and any coexisting disease. This publication reviews the most important blood, urine and ruminal fluid parameters in such patients. The diagnostic significance of the laboratory values under discussion is not so great with obstructions to the caudal part of the digestive tract. However, markedly raised ruminal fluid chloride levels, combined with hypochloraemia and a metabolic acidosis, are indicative of an "abomasoruminal reflux syndrome" resulting from an obstruction in the region of the abomasum or cranial small intestine.  相似文献   
107.
108.
109.
Sheep affected by broken mouth periodontal disease (P.D.) were examined over a twelve month period for different clinical parameters. It is suggested that P.D. in sheep is an episodic phenomenon similar to human P.D., and that only a few animals with signs of P.D. may undergo clinically significant destruction over a yearly period. No single parameter could reliably predict future deterioration in other parameters.  相似文献   
110.
The detection of Mycobacterium paratuberculosis organisms in bovine faeces by isolation was compared with that by the microscopical examination of Ziehl-Neelsen stained faecal smears for the presence of clumps of acid-fast M. paratuberculosis organisms. Faeces were obtained from cattle naturally or experimentally infected with M. paratuberculosis as well as from uninfected cattle. Microscopical examination was an unreliable method for the detection of M. paratuberculosis organisms, since the organisms were only detected in 99 (=55.9%) of 177 culturally positive faecal samples. 1111 addition, clumps of acid-fast organisms indistinguishable from M. paratuberculosis were also observed iin three of 18 samples from cattle free from Johne's disease and in 18 of 37 culturally negative samples from paratuberculous cattle. When M. paratuberculosis organisms were added to faeces from an uninfected cow, results showed that isolation attempts should be positive when 15 or more M. paratuberculosis organisms per gram of faeces are present.  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