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   17279篇
  免费   811篇
  国内免费   312篇
林业   1429篇
农学   1270篇
基础科学   381篇
  3577篇
综合类   2457篇
农作物   924篇
水产渔业   940篇
畜牧兽医   5673篇
园艺   590篇
植物保护   1161篇
  2023年   119篇
  2022年   228篇
  2021年   365篇
  2020年   442篇
  2019年   452篇
  2018年   420篇
  2017年   503篇
  2016年   487篇
  2015年   394篇
  2014年   501篇
  2013年   934篇
  2012年   926篇
  2011年   1070篇
  2010年   719篇
  2009年   623篇
  2008年   917篇
  2007年   937篇
  2006年   960篇
  2005年   906篇
  2004年   738篇
  2003年   721篇
  2002年   670篇
  2001年   285篇
  2000年   261篇
  1999年   281篇
  1998年   233篇
  1997年   219篇
  1996年   192篇
  1995年   166篇
  1994年   164篇
  1993年   162篇
  1992年   154篇
  1991年   161篇
  1990年   146篇
  1989年   163篇
  1988年   151篇
  1987年   99篇
  1986年   88篇
  1985年   110篇
  1984年   95篇
  1983年   104篇
  1982年   74篇
  1981年   69篇
  1980年   83篇
  1979年   76篇
  1978年   72篇
  1977年   71篇
  1975年   55篇
  1974年   57篇
  1970年   63篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
41.
42.
A field strain of Cooperia oncophora resistant to oxfendazole was isolated from a commercial cattle rearing property in Waikato, New Zealand. Resistance to oxfendazole was assessed by means of a faecal egg count depression test and an in vitro egg hatch test. This is the first documented case of anthelmintic resistance in Cooperia spp. and the first report of anthelmintic resistance in cattle in New Zealand.  相似文献   
43.
Book reviews     
Recent Advances in Turkey Science. Edited by C. Nixey and T. C. Grey, Poultry Science Symposium Number 21. London, Butterworths, ISBN 0 408 00971 3

Egg and Eggshell Quality. Sally E. Solomon, 1991, 149 pp., illustrated. London, Wolfe Publishing Ltd., £35.00, ISBN 0 7234 1647 8.

Aleen Cust, Veterinary Surgeon, Britain's First Woman Vet. Connie M. Ford, 1990, 109 pp., £5.99, Bristol, Biopress Ltd., The Orchard, Clanage Road, ISBN 0 948737 11 5.

Avian Incubation. Edited by S. G. Tullett, 1991, xiv + 335 pp., illustrated. London, Butterworth‐Heinemann. £00.00, $00.00. ISBN 0–7506–1002–6.

A Colour Atlas of Diseases & Disorders of the Domestic Fowl & Turkey. Edited by C. J. Randall, second edition, 1991, 175 pages, 432 illustrations in colour. London, Wolfe Publishing Ltd, £35, ISBN 0723416281.  相似文献   

44.
A method for the control of ovine footrot is described which utilises the most appropriate measures to suit the circumstances for individual properties. This approach was used to eradicate the disease from three Central Otago fine-wool properties wintering in excess of 35,000 sheep on widely differing classes of land. This programme incorporates the use of proven.techniques and suitable planning together with input from the rural veterinarian, who plays an important role in demonstration and advising on control measures.  相似文献   
45.
Avian influenza virus (A/Chicken/Pennsylvania/83; H5N2) was recovered from the yolk, albumen, and shell surface of eggs obtained from naturally infected chicken flocks in Pennsylvania and Virginia. These findings represent the first reported isolation of avian influenza virus from the internal contents of eggs from naturally infected flocks. The need for adequate safeguards to prevent spread of the virus during commercial movement of table and hatching eggs, cracked and "checked" eggs, and egg flats and other materials is emphasized.  相似文献   
46.
47.
本文分析了福建省110个国营林场的类型、目前管理体制、管理办法及存在的问题。指出了目前国营林场管理办法中存在着种种弊端,跟深化林业改革很不适应,必须改革和完善国营林场管理机制,理顺“省办地管县监督”的管理体制,实行分类指导。本文就分类管理的依据,原则和实施办法进行了探讨,并提出了一些建议。  相似文献   
48.
A review of models of landscape change   总被引:23,自引:1,他引:22  
Models of landscape change may serve a variety of purposes, from exploring the interaction of natural processes to evaluating proposed management treatments. These models can be categorized as either whole landscape models, distributional landscape models, or spatial landscape models, depending on the amount of detail included in the models. Distributional models, while widely used, exclude spatial detail important for most landscape ecological research. Spatial models require substantial data, now more readily available, via remote sensing, and more easily manipulated, in geographical information systems. In spite of these technical advances, spatial modelling is poorly developed, largely because landscape change itself is poorly understood.To facilitate further development of landscape models I suggest (1) empirical multivariate studies of landscape change, (2) modelling of individual landscape processes, (3) explicit study of the effect of model scale on model behavior, and (4) scaling-up results of studies, on smaller land areas, that have landscape relevance.  相似文献   
49.
50.
The cause of a streak disease of pearl millet (Pennisetum glaucum), originating from Nigeria, has been attributed to a geminivirus belonging to the African streak virus cluster. A full-length, infectious clone of the virus was obtained which was transmissible by the vectorCicadulina mbila (Naudé). Analysis of the complete nucleotide sequence of the coat protein gene of this virus shows it to be most closely related to sugarcane streak virus. The possible evolutionary implications of this finding are discussed.  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