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   148444篇
  免费   6956篇
  国内免费   2759篇
林业   8442篇
农学   7056篇
基础科学   2631篇
  16883篇
综合类   33879篇
农作物   6253篇
水产渔业   6097篇
畜牧兽医   65848篇
园艺   2127篇
植物保护   8943篇
  2019年   1490篇
  2018年   1774篇
  2017年   2095篇
  2016年   1977篇
  2015年   2119篇
  2014年   2252篇
  2013年   5225篇
  2012年   3979篇
  2011年   4631篇
  2010年   3506篇
  2009年   3312篇
  2008年   4406篇
  2007年   4543篇
  2006年   4264篇
  2005年   4037篇
  2004年   3342篇
  2003年   3385篇
  2002年   3146篇
  2001年   3739篇
  2000年   3820篇
  1999年   3434篇
  1998年   1734篇
  1997年   1660篇
  1996年   1516篇
  1995年   1787篇
  1994年   1576篇
  1993年   1547篇
  1992年   2895篇
  1991年   2934篇
  1990年   3015篇
  1989年   2999篇
  1988年   2791篇
  1987年   2635篇
  1986年   2657篇
  1985年   2637篇
  1984年   2173篇
  1983年   1960篇
  1979年   2137篇
  1978年   1723篇
  1977年   1527篇
  1976年   1426篇
  1975年   1608篇
  1974年   2090篇
  1973年   2080篇
  1972年   2121篇
  1971年   2042篇
  1970年   1903篇
  1969年   1669篇
  1968年   1430篇
  1967年   1574篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
The complement fixation test (CFT), the enzyme labelled immunosorbent assay (ELISA) and the gel diffusion precipitin test (GD) were compared, for the diagnosis of Brucella ovis infection in rams. The sensitivities of the tests in 109 rams which were shedding B. ovis in their semen were: CFT 96.3%; ELISA 97.2%; GD 91.7%. The specificities of the tests in 141 rams from non-infected flocks were: CFI 99.3%; ELISA 98.6%; GD 100%. Predictive values of the three tests were measured in 285 rams from infected flocks. Thirty-eight percent of these rams were shedding B. ovis in their semen. Predictive values of positive tests were: CFT 75.5%; ELISA 66.7%; GD 72.5%. Predictive values of negative tests were: CFI 97.1%; ELISA 97.6%; GD 93.8%.  相似文献   
192.
The construction of a simple, portable restrainer for holding sheep in either the horizontal or vertical position for abdominal radiography is described. Examples of its use in locating slow-release pellets-and needles are given.  相似文献   
193.
Pleural effusions can cause dyspnea and cyanosis, and are caused by cardiomyopathy, pyothorax, FIP, FeLV-related disease and trauma. Thoracentesis is used to obtain fluid samples for cytologic examination and culture. Radiographs made after thoracentesis may reveal the cause. Lymphosarcoma causes a sterile exudate containing neoplastic cells. Congestive cardiomyopathy causes a transudate or modified transudate. The sterile exudate of FIP has a proteinaceous background on cytologic examination. The exudate of pyothorax is septic. Treatment depends on the cause but generally includes thoracentesis and supportive care. Cardiomyopathy causes dyspnea, cyanosis, murmurs, gallop rhythms and other arrhythmias. Radiography reveals a globoid heart in the congestive form and a "valentine-shaped" heart in the hypertrophic form. Treatment of congestive cardiomyopathy involves use of furosemide, but is usually unrewarding. Hypertrophic cardiomyopathy is treated with propranolol. Fever may be caused by infection, immune-mediated disease, neoplasia and unknown causes. Treatment is aimed at removal of the underlying cause.  相似文献   
194.
Cysts found in the liver of a horse which had never been out of New Zealand were used to infect two dogs which were slaughtered 35 days after infection. Large numbers of Echinococcus granulosus were recovered. These cestodes were compared with mature dog-sheep cestodes, using light and scanning electron microscopy and identified as the dog-horse strain of E.granulosus.  相似文献   
195.
196.
197.
198.
199.
On a property in the Nelson District, blood and urine samples were taken from red deer (Cervus elaphus) from which low (<1:100) antibody titres to serovar copenhageni and suspected leptospiral abortions had previously been reported. A total of 27 hinds were sampled. Microscopic agglutination test (MAT) titres in sera ranging from 1:32 to 1:128 were found in six animals. Thirteen leptospiral isolations were made from nine of the 27 urine samples. Four of these were typed as copenhageni and nine as hardjo. Two cultures were prepared from each urine sample and hardjo and copenhageni were both isolated from single urine samples from two animals. None of the 27 deer had serum MAT titres at 1:32 or above to copenhageni.  相似文献   
200.
Of 32 calves given an unknown amount of a pluronic bloat mixture with their milk, 28 died in convulsions over 24 hours. Supportive therapy was unsuccessful. Concentrations of pluronic present in abomasal and rumenal contents supported a diagnosis of pluronic poisoning.  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