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   168875篇
  免费   9357篇
  国内免费   100篇
林业   7592篇
农学   5604篇
基础科学   1001篇
  21230篇
综合类   26792篇
农作物   6399篇
水产渔业   8498篇
畜牧兽医   88093篇
园艺   2166篇
植物保护   10957篇
  2019年   1682篇
  2018年   2617篇
  2017年   2891篇
  2016年   2679篇
  2015年   2342篇
  2014年   2878篇
  2013年   6791篇
  2012年   5143篇
  2011年   6061篇
  2010年   4109篇
  2009年   4192篇
  2008年   6049篇
  2007年   5848篇
  2006年   5525篇
  2005年   5094篇
  2004年   4872篇
  2003年   4914篇
  2002年   4551篇
  2001年   5619篇
  2000年   5439篇
  1999年   4395篇
  1998年   1749篇
  1997年   1746篇
  1996年   1627篇
  1995年   1928篇
  1994年   1636篇
  1993年   1670篇
  1992年   3337篇
  1991年   3452篇
  1990年   3430篇
  1989年   3488篇
  1988年   3156篇
  1987年   3176篇
  1986年   3146篇
  1985年   2982篇
  1984年   2447篇
  1983年   2177篇
  1982年   1478篇
  1979年   2107篇
  1978年   1692篇
  1977年   1489篇
  1976年   1450篇
  1975年   1524篇
  1974年   1880篇
  1973年   1887篇
  1972年   1880篇
  1971年   1701篇
  1970年   1712篇
  1969年   1604篇
  1967年   1402篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
1. The effect of reducing food intake to 75% of the ad libitum intake was determined from hatching to 8 weeks in young Light Sussex chickens.

2. Restricted birds were lighter throughout the experiment.

3. Relative adrenal weight tended to be greater in restricted birds but the difference decreased with time.

4. There was no depletion of adrenal cholesterol: from week 5 there was a significantly greater amount in the adrenals of restricted birds.

5. After 1 week of restriction plasma corticosterone concentration was 73% greater than in controls. It decreased progressively, falling within the normal range at 5 weeks.

6. Restricted birds were hypoglycaemic from weeks 2 to 7 and hyper‐lipacidaemic throughout. A negative correlation between plasma glucose and free fatty acids was found.  相似文献   

952.
1. The fatty liver of newly‐hatched pigeons is caused by an accumulation of sterol esters (STE) amounting to 620 mg/g total lipids of which 80% was sterol oleate. Triglycerides (TG) accounted for only 20 mg/g of total lipids.

2. After hatching, the relative amount of STE in the liver tissue decreased considerably while that of TG increased. The proportion of phospholipids (PHL) remained essentially constant.

3. The fatty acid composition of the liver lipids changed significantly, but specifically for each individual class during postnatal growth. Striking differences were the higher values of long‐chain polyunsaturated acids (20 :4 ω6, 22 :4 ω6 and 22: 6 ω3) in PHL, TG and free fatty acids (FFA) and the higher proportion of oleic acid in the STE at hatching compared with those at older ages.

4. The predominant alterations in the relative composition of the liver lipids (lipid classes and fatty acids) occurred in the first week after hatching and may be accounted for by the decreasing yolk utilisation and adaptation to ingested food. The change within the diet itself from cropmilk to grain (starting around the 4th day) influenced the development of the lipid and fatty acid content only in a minor way.

5. The large weight decrease of the pigeon liver after the 19th day was accompanied by a decrease in absolute PHL content while TG stores were unaltered.  相似文献   

953.
1. Starter diets containing either maize or salseed meal to replace the maize were fed to chicks over a period of 2 weeks.

2. Growth rate, food intake, food utilisation and proportion of dietary nitrogen retained were much poorer in chicks receiving salseed meal.

3. The chicks receiving salseed meal developed pathological lesions in liver and kidney.

4. The red blood cell count, white blood cell count, haemoglobin concentration and packed cell volume of the chicks receiving salseed meal were lower than those of chicks receiving maize.

5. The apparent metabolisable energy value of salseed meal was determined as 6.83 MJ/kg.  相似文献   

954.
955.
956.
Radiocarbon dates associated with engraved stones from sealed archeological deposits at Wonderwerk Cave in the northern Cape Province indicate that rock engraving in South Africa is at least 10,000 years old.  相似文献   
957.
958.
959.
960.
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