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   17503篇
  免费   942篇
  国内免费   18篇
林业   843篇
农学   608篇
基础科学   130篇
  2634篇
综合类   2701篇
农作物   929篇
水产渔业   987篇
畜牧兽医   8501篇
园艺   207篇
植物保护   923篇
  2020年   165篇
  2019年   185篇
  2018年   317篇
  2017年   371篇
  2016年   270篇
  2015年   210篇
  2014年   324篇
  2013年   686篇
  2012年   514篇
  2011年   637篇
  2010年   439篇
  2009年   420篇
  2008年   643篇
  2007年   581篇
  2006年   547篇
  2005年   479篇
  2004年   456篇
  2003年   455篇
  2002年   388篇
  2001年   502篇
  2000年   484篇
  1999年   387篇
  1998年   189篇
  1997年   209篇
  1995年   204篇
  1994年   159篇
  1993年   169篇
  1992年   290篇
  1991年   320篇
  1990年   315篇
  1989年   316篇
  1988年   292篇
  1987年   251篇
  1986年   297篇
  1985年   257篇
  1984年   211篇
  1983年   210篇
  1979年   252篇
  1978年   172篇
  1977年   161篇
  1975年   181篇
  1974年   237篇
  1973年   224篇
  1972年   252篇
  1971年   232篇
  1970年   206篇
  1969年   192篇
  1968年   160篇
  1967年   161篇
  1966年   163篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
51.
52.
Sectional notes     
American Journal of Potato Research -  相似文献   
53.
54.
55.
56.
1118 Friesian cows and 101 Friesian heifers were investigated in internal pelvic measurements and their relationships to external measurements. The mean of the pelvic vertical and the medium diagonally diameter of the pelvis are 19.8 cm and 18.3 cm. 363.9 square centimetres and 76.3 centimetres were found for the pelvic surface and pelvic circumference. The difference between the biggest and smallest pelvis was 295.0 square centimetres. Medium to high coefficiences of correlation were detected between the internal pelvic measurements but relationships between internal and external pelvic measurements were low. From determined external pelvic measurements only the hip breadth provides usefull informations of the pelvic shape.  相似文献   
57.
A haematological disorder in a dog characterised by a massive leucocytosis, mainly composed of eosinophils and their precursors is reported here. The normal composition of cells in the bone marrow was displaced in favour of the eosinophils and their precursors. No apparent cause for the pronounced eosinophilia could be determined by clinical, haematological, clinical-chemical, radiological or pathological examinations. A diagnosis of eosinophilic leukaemoid reaction was suggested as the criteria for the diagnosis of eosinophilic leukaemia in the dog but this was not firmly established.  相似文献   
58.
Heat production, which accounts for 0.6 of gross energy intake, is insufficiently represented in predictions of food intake. Especially when heat production is elevated (for example by lower temperature or poor feathering) the classical predictions based on body weight, body-weight change and egg mass are inadequate. Heat production was reliably estimated as [35.5-environmental temperature (degree C)] x [Defeathering (=%IBPW) + 21]. Including this term (PHP: predicted heat production) in equations predicting food intake significantly increased accuracy of prediction, especially under suboptimal conditions. Within the range of body weights tested (from 1.6 kg in brown layers to 2.8 kg in dwarf broiler breeders), body weight as an independent variable contributed little to the prediction of food intake; especially within strains its effect was better included in the intercept. Significantly reduced absolute values of residual food consumption were obtained over a wide range of conditions by using predictions of food intake based on body-weight change, egg mass, predicted heat production (PHP) and an intercept, instead of body weight, body-weight change, egg mass and an intercept.  相似文献   
59.
Anatomy of the digestive tract and external body development during the embryonic stages of the caprine (Copra, bircus) The purpose of this work has been to establish the pattern of prenatal growth and normal development of the digestive tract and annex glands during goat embryonic stages. 21 embryos with ages ranging from 14 to 34 days (1.69 to 5.90 cm CR) as determined by registering the mating time, were obtained by cesarea. This material was histologically processed to obtain complete serial sections of the stomatodaeum, foregut, midgut, hindgut and cloaca. In this work, it is chronologically described the morphogenesis and histogenesis of the mouth, hypophysis, pharynx and its derivatives, stomach, intestine, liver, pancreas and cloaca. The results obtained establish chronological comparisons with the development of the lamb and gives information on the unitary origin of the gastric compartments in ruminants.  相似文献   
60.
Book review     
Poultry Health and Management: Chickens, Ducks, Turkeys, Geese, Quail, 3rd edn. By David Sainsbury, 1992. 214 pp., illustrated. Oxford, Blackwell Scientific Publications. £17.99. ISBN 0–632–03325–8.  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