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   153182篇
  免费   8714篇
  国内免费   91篇
林业   6159篇
农学   4672篇
基础科学   1054篇
  18611篇
综合类   25680篇
农作物   5737篇
水产渔业   8031篇
畜牧兽医   78987篇
园艺   1910篇
植物保护   11146篇
  2018年   2150篇
  2017年   2361篇
  2016年   2244篇
  2015年   1902篇
  2014年   2309篇
  2013年   5869篇
  2012年   4394篇
  2011年   5298篇
  2010年   3232篇
  2009年   3250篇
  2008年   5121篇
  2007年   4851篇
  2006年   4644篇
  2005年   4357篇
  2004年   4219篇
  2003年   4194篇
  2002年   4083篇
  2001年   4817篇
  2000年   4655篇
  1999年   3800篇
  1998年   1489篇
  1997年   1512篇
  1996年   1427篇
  1995年   1757篇
  1994年   1592篇
  1993年   1519篇
  1992年   3219篇
  1991年   3335篇
  1990年   3373篇
  1989年   3384篇
  1988年   3099篇
  1987年   3193篇
  1986年   3281篇
  1985年   3132篇
  1984年   2647篇
  1983年   2343篇
  1982年   1594篇
  1981年   1499篇
  1980年   1449篇
  1979年   2359篇
  1978年   1956篇
  1977年   1664篇
  1976年   1471篇
  1975年   1564篇
  1974年   2116篇
  1973年   2117篇
  1972年   2108篇
  1971年   1868篇
  1970年   1733篇
  1969年   1594篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
36.
Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.  相似文献   
37.
38.
39.
Xylazine and tiletamine-zolazepam anesthesia in horses   总被引:4,自引:0,他引:4  
The cardiopulmonary and anesthetic effects of xylazine in combination with a 1:1 mixture of tiletamine and zolazepam were determined in 6 horses. Each horse was given xylazine IV or IM, as well as tiletamine-zolazepam IV on 4 randomized occasions. Anesthetics were administered at the rate of 1.1 mg of xylazine/kg of body weight, IV, 1.1 mg of tiletamine-zolazepam/kg, IV (treatment 1); 1.1 mg of xylazine/kg, IV, 1.65 mg of tiletamine-zolazepam/kg, IV (treatment 2); 1.1 mg of xylazine/kg, IV, 2.2 mg of tiletamine-zolazepam/kg, IV (treatment 3); and 2.2 mg of xylazine/kg, IM, 1.65 mg of tiletamine-zolazepam/kg, IV (treatment 4). Tiletamine-zolazepam doses were the sum of tiletamine plus zolazepam. Xylazine, when given IV, was given 5 minutes before tiletamine-zolazepam. Xylazine, when given IM, was given 10 minutes before tiletamine-zolazepam. Tiletamine-zolazepam induced recumbency in all horses. Duration of recumbency in group 1 was 31.9 +/- 7.2 (mean +/- 1 SD) minutes. Increasing the dosage of tiletamine-zolazepam (treatments 2 and 3) significantly (P less than 0.05) increased the duration of recumbency. Xylazine caused significant (P less than 0.05) decreases in heart rate and cardiac output and significant (P less than 0.05) increases in central venous pressure and mean pulmonary artery pressure 5 minutes after administration. Respiratory rate was decreased. Arterial blood pressures increased significantly (P less than 0.05) after xylazine was administered IV in treatments 1 and 3, but the increases were not significant in treatment 2. Xylazine administered IM caused significant (P less than 0.05) increases in central venous pressure and significant (P less than 0.05) decreases in cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
40.
Chinese catfish ( Clarias fuscus ) were successfully spawned in Hawaii using human chorionic gonadotropin (HCG) at dosage rates of two and four international units (IU) per gram body weight. Fish not injected with HCG did not produce viable eggs. Successful spawns with HCG occurred between May and October. Hatch rates of up to 80% were obtained during June, July, and August for those fish given either a 2 or 4 IU per gram body weight injection of HCG. Fish spawned in either May or October yielded significantly higher hatch rates when injected with 4 rather than 2 IU per gram body weight. Fish held at elevated temperatures (28 to 30 C) prior to the normal spawning season developed significantly larger oocyte diameters, 60 days earlier than fish held under ambient temperature conditions (21.5 to 24 C). Photoperiod manipulation at ambient temperature conditions was associated with earlier oocyte maturation, but photoperiod effects were much less important than temperature.  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