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   98635篇
  免费   5477篇
  国内免费   94篇
林业   3742篇
农学   2868篇
基础科学   700篇
  11593篇
综合类   17296篇
农作物   3924篇
水产渔业   4750篇
畜牧兽医   52332篇
园艺   1110篇
植物保护   5891篇
  2018年   1332篇
  2017年   1522篇
  2016年   1349篇
  2015年   1170篇
  2014年   1480篇
  2013年   3689篇
  2012年   2579篇
  2011年   3239篇
  2010年   2040篇
  2009年   2148篇
  2008年   3144篇
  2007年   2910篇
  2006年   2832篇
  2005年   2486篇
  2004年   2432篇
  2003年   2433篇
  2002年   2257篇
  2001年   3069篇
  2000年   3150篇
  1999年   2428篇
  1998年   966篇
  1997年   993篇
  1996年   931篇
  1995年   1180篇
  1994年   1014篇
  1993年   982篇
  1992年   2146篇
  1991年   2333篇
  1990年   2182篇
  1989年   2187篇
  1988年   2059篇
  1987年   2122篇
  1986年   2206篇
  1985年   2066篇
  1984年   1654篇
  1983年   1465篇
  1982年   987篇
  1979年   1547篇
  1978年   1247篇
  1977年   1094篇
  1976年   1054篇
  1975年   1129篇
  1974年   1461篇
  1973年   1472篇
  1972年   1436篇
  1971年   1333篇
  1970年   1247篇
  1969年   1128篇
  1968年   964篇
  1967年   1000篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
Within 2 years, following the introduction of 2 Shorthorn bulls from the same stud into an Australian Illawarra Shorthorn (AIS) herd, 16 calves were born with cerebellar hypoplasia. All affected calves were the progeny of one bull mated to the daughters of the other. All other progeny of these bulls, most of which were from AIS dams, were normal. Affected calves exhibited severe ataxia, consistent head movement and abduction of the forelimbs. Microscopic changes in the cerebellum included sparsity of cells of the granular layer, loss of Purkinje cells and narrowing of the molecular layer. Observations on the frequencies of normal and abnormal calves are consistent with the hypothesis that the condition is caused by an autosomal recessive gene for which affected calves were homozygous and which was introduced into the herd in heterozygous condition by both of the Shorthorn bulls. Evidence is given for an unusually high frequency of the gene in the stud of origin of the Shorthorn bulls and a procedure for reducing its frequency is outlined. The possibility of a viral or toxic aetiology is discussed but is considered to be an unlikely explanation for the condition in this herd.  相似文献   
943.
Young broiler chicks inoculated with Eimeria tenella and given a diet containing 2.5 mug aflatoxin/g had significantly higher mortality than birds with aflatoxicosis or coccidiosis alone or uninoculated controls. This effect was seen even when a light coccidial infection alone did not increase mortality or cause weight depression. In addition this higher mortality with the combination began earleir and occurred at a higher rate than did mortality from aflatoxin or cecal coccidiosis alone. Dietary monensin sodium (99 umg/g) did not completely prevent mortality and weight depression when aflatoxin and E. tenella were in combination. Aflatoxin and E. tenella singly significantly depressed three-week body weights; however, the depression was most severe when the two were in combination. Both dietary aflatoxin and E. tenella significantly reduced hemoglobin, packed cell volume, and plasma pigmentation, and in combination resulted in more severely reduced hemoglobin, packed cell volume, and plasma pigmentation. Coccidial lesion scores were significantly less for the combination of E. tenella and aflatoxicosis than for coccidiosis alone. This atypical response of the ceca to E. tenella in the presence of dietary aflatoxin was characterized by less distended ceca, very little coagulated blood in the ceca, and apparently more profuse cecal hemorrhage.  相似文献   
944.
945.
946.
947.
Because of the type of patient treated, and the nature of the injury, the veterinarian is often called upon to treat surgical infections. These infections may be primary, or can be sequelae or trauma or elective surgery. Each clinician has his own protocol and priorities in evaluation of the patient with a surgical infection. A careful history and physical examination, together with clinical and microbiological laboratory testing procedures will help identify the pathogenic organism and indicate the severity of the infection in the animal patient. With this preliminary evaluation, the clinician and surgeon may attack the problem appropriately, and with a greater assurance of success.  相似文献   
948.
949.
The use of a palatine prosthesis in the treatment of a traumatic cleft palate in a dog is described. Attempts at surgical repair of the cleft failed and the prosthesis successfully obturated the defect for 10 months. The value of this technique used alone or in combination with palatoplasty is discussed.  相似文献   
950.
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