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   234974篇
  免费   14410篇
  国内免费   649篇
林业   23297篇
农学   13949篇
基础科学   2952篇
  41497篇
综合类   15972篇
农作物   17018篇
水产渔业   16487篇
畜牧兽医   89400篇
园艺   6230篇
植物保护   23231篇
  2021年   2420篇
  2020年   2826篇
  2019年   3622篇
  2018年   3871篇
  2017年   4194篇
  2016年   4686篇
  2015年   4281篇
  2014年   5617篇
  2013年   16224篇
  2012年   5792篇
  2011年   7601篇
  2010年   7179篇
  2009年   7760篇
  2008年   6932篇
  2007年   6014篇
  2006年   6694篇
  2005年   5912篇
  2004年   5772篇
  2003年   5511篇
  2002年   4877篇
  2001年   5666篇
  2000年   5269篇
  1999年   5009篇
  1998年   4089篇
  1997年   4131篇
  1996年   3876篇
  1995年   4395篇
  1994年   3786篇
  1993年   3511篇
  1992年   3963篇
  1991年   4224篇
  1990年   3914篇
  1989年   3845篇
  1988年   3404篇
  1987年   3450篇
  1986年   3254篇
  1985年   3616篇
  1984年   3432篇
  1983年   3199篇
  1982年   2722篇
  1981年   2644篇
  1980年   2605篇
  1979年   2927篇
  1978年   2630篇
  1977年   2448篇
  1976年   2320篇
  1975年   2130篇
  1974年   2235篇
  1973年   2179篇
  1971年   1926篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The cleistogamous species Collomia grandiflora produces dimorphic cross-incompatible flowers on a single plant. The open or chasmogamous flower has smaller, flask-shaped stigmatic papillae, larger pollen grains, longer styles, and faster pollen tube growth rates down the style than the closed or cleistogamous flower. In intermorph crosses, pollen tube growth rates are greatly decreased and fertilization does not occur.  相似文献   
992.
993.
994.
995.
996.
1. It has been shown that both the variety of wheat and the environment under which growth took place influenced the quantities of starch and cell wall carbohydrate contents of wheat.

2. The different varieties of wheat investigated contained different proportions of water‐soluble to water‐insoluble hemicelluloses.

3. By comparison of the arabinose to xylose ratios it was concluded that water‐soluble and insoluble arabinoxylans of wheat were branched to the same degree.

4. Starch from six wheat varieties grown in the U.K. was very well digested by adult cockerels and true metabolisable energy values of the wheats were high.

5. Small amounts of cell wall carbohydrates were digested by adult cockerels.  相似文献   

997.
1. Conditions affecting the keeping quality of traditional farm‐fresh turkeys were investigated.

2. Storage of uneviscerated Wrolstad turkeys at 4 °C for 10 days caused no statistically significant changes in meat flavour or texture.

3. During further storage at —2 °C, however, there was a slight but significant change in flavour, which became more marked with time in birds which had been eviscerated after the initial period at 4 °C.

4. Both eviscerated and uneviscerated birds became slightly tougher during storage.

5. Initial holding at 4 °C increased the numbers of psychrotrophic bacteria on the skin by about 103 but subsequent changes at — 2 °C were slight for uneviscerated birds.

6. Eviscerated carcases had higher counts than uneviscerated birds after storage at — 2 °C and, although ‘off’ odours were not detected, spoilage appeared to be imminent at the end of the 20‐d period.  相似文献   

998.
Book reviews     
Birds Their Structure and Function, By A. S. King and J. McLelland, 1984. 2nd ed. 334 pp. illustrated. London, Baillière Tindall. £9.50. ISBN 0 7020 0872 9.

Proceedings of the 2nd European Symposium on Poultry Welfare, 1985. 360 pp. illustrated. German Branch of the World's Poultry Science Association, Celle, Institut für Kleintierzucht.  相似文献   

999.
In the series of experiments with labelled urea three colostomized laying hybrids were butchered after a six-day application of 1% urea with 96.06 atom-% 15N excess (15N') in the ration and another 2 days with a supplement of 1% unlabelled urea. Out of the individual samples from crop, gizzard, small intestine, caecum and rectum, the content of the small intestine and the caecum showed the highest labelling with greater than 1 atom-% 15N'. The TCA soluble fraction of the content of the gizzard was more highly and that of the intestines less labelled than the total nitrogen. The tissue of the gizzard is distinctly less labelled than the "omasum system" and the small intestine. The atom-% 15N' of the oesophagus with crop and glandular stomach largely showed agreement in the individual hens with that of intestinal tissue and ranged between 0.71 and 0.89 atom-%. 2% of the 15N' supplemented with the urea could be recovered in the content and the tissue of the gastro-intestinal tract.  相似文献   
1000.
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