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   37700篇
  免费   1101篇
  国内免费   847篇
林业   5455篇
农学   2605篇
基础科学   852篇
  7056篇
综合类   3215篇
农作物   3302篇
水产渔业   3395篇
畜牧兽医   8719篇
园艺   1590篇
植物保护   3459篇
  2023年   189篇
  2022年   334篇
  2021年   489篇
  2020年   441篇
  2019年   380篇
  2018年   3338篇
  2017年   3431篇
  2016年   1995篇
  2015年   961篇
  2014年   855篇
  2013年   1119篇
  2012年   2243篇
  2011年   3299篇
  2010年   2818篇
  2009年   1854篇
  2008年   2140篇
  2007年   2413篇
  2006年   807篇
  2005年   1507篇
  2004年   1214篇
  2003年   1079篇
  2002年   697篇
  2001年   569篇
  2000年   419篇
  1999年   448篇
  1998年   128篇
  1997年   119篇
  1996年   106篇
  1992年   218篇
  1991年   217篇
  1990年   223篇
  1989年   220篇
  1988年   229篇
  1987年   162篇
  1986年   195篇
  1985年   161篇
  1984年   129篇
  1983年   111篇
  1979年   164篇
  1978年   127篇
  1977年   122篇
  1975年   144篇
  1974年   153篇
  1973年   156篇
  1972年   167篇
  1971年   142篇
  1969年   112篇
  1968年   122篇
  1967年   129篇
  1966年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
In a feeding trial lasting for months Halothane-positive fattening pigs were put on a diet containing different concentrations of vitamin E and selenium. After a Myostress application vitamin E and selenium were additionally injected in order to examine stress resistance (CK-test) and regenerative capacity (histological examination of Musculus longissimus dorsi) of skeletal muscle. The study revealed that neither high dietary levels of vitamin E/selenium nor a vitamin E/selenium treatment applied after stress are capable of preventing stress related myopathy nor can they influence its healing up favourably.  相似文献   
4.
5.
Eradication of lice in cattle.   总被引:8,自引:0,他引:8  
The purpose of this field study was to develop and evaluate eradication as a strategy to control lice in cattle. Thirty-three herds of cattle were selected and observed during a period of two and a half years. Before eradication, biting lice (Damalinia bovis) were present in 94% of the herds and 27% of the animals. Sucking lice (Linognathus vituli) were present in 42% of the herds and 5% of the animals. These levels were very similar to those reported from other countries in Northern Europe. The eradication strategy was successful in 28 of 33 herds, but lice were still present in 5 herds 3 to 6 months after treatment. Biting lice were present in all these 5 herds, sucking lice were present in 3 herds. During the next 12 months, nine of the 28 herds were reinfected with lice. Six herds were reinfected with just biting lice, 2 herds with just sucking lice and one herd was reinfected with both. There was no significant difference between the 2 louse species regarding the risk of unsuccessful eradication or reinfection. The only significant risk factor for reinfection was either purchase of livestock or use of common pasture, combined with failure in pre-treatment of newly introduced animals.  相似文献   
6.
The article considers the attractions and dangers of homeopathic therapy from the view of a pharmacologist. Homeopathic drugs may exert pharmacodynamic (but also toxic) effects at low dilutions (D0-D6), but there is no scientific proof for specific effects of higher dilutions except for substances with a high toxic potential. Most homeopathic drugs have no reasonable basis for clinical use but, in case of toxic compounds, especially those with carcinogenic or allergic potential, homeopathy may bear risks for the animal and, because of residues in food animals, also for humans. Thus, homeopathic treatment should not be used when effective conventional treatments are available, and the use of homeopathic drugs with toxic potential should be avoided.  相似文献   
7.
8.
Antibodies to bovine serum albumin were detected in swine sera by use of an immunoblotting technique. Such sera had false-positive reactions, as determined by results of African swine fever virus serodiagnostic techniques when bovine serum albumin was a contaminant in the soluble cytoplasmic antigen obtained from infected cells cultured in the presence of bovine serum. The soluble cytoplasmic antigen obtained from cell cultures infected with African swine fever virus in the presence of porcine serum did not react with the false-positive sera and, therefore, was used for African swine fever virus serodiagnostic methods, with 0% false-positive results.  相似文献   
9.
10.
姜瘟病是中国生姜生产上发生较为普遍的病害,是由青枯劳尔氏菌(Ralstoniasolanacearum)引起的。此病原菌寄主范围广,可侵染44个科300多种植物。菌体短杆状,在TZC选择性培养基上培养出现白边较宽和白边较窄的两种菌落。菌系划分为5个生理小种和5个生化型,中国的姜瘟菌主要属生理小种1号,生物型属II、III、IV。此病害是一种较难防治的土传病害,在高温、高湿、雨水多、氮肥过量的情况下发生较为严重。中国植病工作者对此病害作了大量的研究工作,对中国姜瘟病的病原菌、发病规律、及防治等研究进展作一综述。  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