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   57625篇
  免费   3062篇
  国内免费   100篇
林业   3532篇
农学   1726篇
基础科学   275篇
  6900篇
综合类   10779篇
农作物   2165篇
水产渔业   2668篇
畜牧兽医   28434篇
园艺   763篇
植物保护   3545篇
  2019年   511篇
  2018年   922篇
  2017年   942篇
  2016年   885篇
  2015年   801篇
  2014年   911篇
  2013年   2131篇
  2012年   1834篇
  2011年   1967篇
  2010年   1281篇
  2009年   1300篇
  2008年   1906篇
  2007年   1966篇
  2006年   1809篇
  2005年   1683篇
  2004年   1585篇
  2003年   1545篇
  2002年   1474篇
  2001年   1648篇
  2000年   1607篇
  1999年   1311篇
  1998年   485篇
  1997年   492篇
  1996年   502篇
  1995年   559篇
  1994年   492篇
  1993年   510篇
  1992年   999篇
  1991年   1004篇
  1990年   1006篇
  1989年   1033篇
  1988年   963篇
  1987年   985篇
  1986年   977篇
  1985年   974篇
  1984年   799篇
  1983年   709篇
  1979年   737篇
  1978年   602篇
  1977年   509篇
  1976年   503篇
  1975年   566篇
  1974年   764篇
  1973年   694篇
  1972年   739篇
  1971年   743篇
  1970年   667篇
  1969年   661篇
  1968年   512篇
  1967年   565篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Meat regulations also involve game inspection. This publication deals with the regulations concerning furred game intended for slaughter and furred game hunted for food.  相似文献   
42.
Duration of maternal immunity to peste des petits ruminants   总被引:1,自引:0,他引:1  
  相似文献   
43.
Chicken anemia agent (CAA) was isolated from broiler chickens in Texas with a blue wing or anemia dermatitis-like syndrome. Specific-pathogen-free chicks inoculated with field material developed anemia, and CAA was isolated in MDCC-MSB1 cells from bone marrow and lymphoid tissue from inoculated chicks. One isolate, designated EF88/78/276, was further characterized. Infectivity of EF88/78/276 was resistant to treatment with chloroform and with heat at 70 C for 5 minutes. EF88/78/276 was indistinguishable from the Cux-1 and Gifu-1 isolates of CAA by cross-neutralization tests. Almost all 1-day-old susceptible chicks inoculated intramuscularly with EF88/78/276 developed anemia, but contact-infected chicks did not. Antibody to CAA was detected in broiler breeder flocks from Texas, the Delmarva peninsula, and Alabama.  相似文献   
44.
We studied the ability of lambs to select safe foods in the presence of harmful foods. In a series of feeding experiments, 3- to 6-mo-old lambs were offered a choice between 1) a familiar, safe and a novel, harmful food, 2) a novel, safe and a novel, harmful food and 3) a familiar, harmful and a novel, safe food. All harmful foods were palatable feeds that had been treated with lithium chloride (LiCl), a non-lethal gastrointestinal poison. When lambs ingested a meal composed of a novel food containing LiCl and a familiar, safe food, lambs subsequently avoided the novel food. Lambs avoided the novel food even when the familiar food contained LiCl. The response of lambs varied when lambs were given a choice between a novel, safe food and a novel food containing LiCl. Lambs either avoided the novel food containing LiCl and ingested the safe food or they limited their intake of both novel foods. Their response was dependent on the novelty of the food containing LiCl. When a novel, palatable food contained 2% LiCl, lambs always ate some of the food, even after experiencing illness from ingesting it. Lambs experienced with foods containing LiCl displayed greater food neophobia than lambs naive to LiCl-treated foods. Thus, novelty was the major criterion that lambs used to associate foods with gastrointestinal illness.  相似文献   
45.
The anatomical-pathological findings of 15 woolly monkeys were comparable with those described in man with essential benign or malignant hypertension. Kidneys revealed arterio- and arteriolosclerosis or an onion peel-like proliferation, in some cases necrotizing endarteritis. Obesity due to restricted physical activity, unnatural feeding, and psychical and physical stress could have contributed to the development of this condition. Further, high vulnerability of the genus woolly monkey is postulated. Thus, essential hypertension of woolly monkeys appears to be a multifactorial disease.  相似文献   
46.
4 female and 2 male untrained fattening pigs, weighing 43.9 +/- 1.6 kg at the beginning of the experiment underwent continuous measurement of VO2, VCO2, and rectal temperature, prior to, during, and after running on a horizontal exercise belt set to speeds of 0.7, 1.3, and 2.5 m.s-1. The highest values of VO2 and VCO2 (ml-min-1/kg-1) and rectal temperature (degrees C) were usually measured few minutes after running. They were 18.84 +/- 3.65 and 20.4 +/- 4.53 as well as 41.2 +/- 0.4, 28.41 +/- 4.07 and 33.26 +/- 5.92 or 41.3 +/- 0.5, 26.21 +/- 7.7 and 32.32 +/- 7.14 as well as 40.5 +/- 0.7, depending on the above belt speeds. Exercise belt speeds of 1.3 to 1.8 m.s-1 were found to be suitable for testing aerobic metabolic capacity of untrained young pigs.  相似文献   
47.
48.
49.
50.
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