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   1617篇
  免费   73篇
  国内免费   4篇
林业   152篇
农学   44篇
基础科学   3篇
  265篇
综合类   59篇
农作物   88篇
水产渔业   169篇
畜牧兽医   785篇
园艺   18篇
植物保护   111篇
  2022年   17篇
  2021年   47篇
  2020年   15篇
  2019年   24篇
  2018年   24篇
  2017年   45篇
  2016年   57篇
  2015年   71篇
  2014年   81篇
  2013年   122篇
  2012年   92篇
  2011年   123篇
  2010年   52篇
  2009年   59篇
  2008年   111篇
  2007年   109篇
  2006年   114篇
  2005年   105篇
  2004年   109篇
  2003年   94篇
  2002年   70篇
  2001年   47篇
  2000年   29篇
  1999年   11篇
  1998年   9篇
  1997年   7篇
  1996年   2篇
  1995年   5篇
  1994年   4篇
  1993年   1篇
  1992年   2篇
  1991年   6篇
  1990年   6篇
  1989年   5篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1974年   2篇
  1973年   1篇
排序方式: 共有1694条查询结果,搜索用时 15 毫秒
101.
The duality of teleost gonadotropins   总被引:5,自引:0,他引:5  
The duality of salmon gonadotropins has been proved by biochemical, biological, and immunological characterization of two chemically distinc gonadotropins. GTH I and GTH II were equipotent in stimulating estradiol production, whereas GTH II appears to be more potent in stimulating maturational steroid synthesis. The ratio of plasma levels and pituitary contents of GTHs and the secretory control by a GnRH suggest that GTH I is the predominant GTH during vitellogenesis and early stages of spermatogenesis in salmonids, whereas GTH II is predominant at the time of spermiation and ovulation. GTH I and GTH II are found in distinctly separate cells. In trout, GTH I is expressed first in ontogeny, whereas GTH II cells appear coincident with the onset of spermatogenesis and vitellogenesis, and increase dramatically at the time of final reproductive maturation. Comparison of the amino acid sequences of polypeptides and the base sequences of cDNA revealed that salmon GTH I β is more similar to bovine FSHβ than bovine LHβ and salmon GTH II β shows higher homology to bovine LHβ than to bovine FSHβ. The existence of two pituitary gonadotropins in teleosts as well as tetrapods suggests that the divergence of the GTH gene took place earlier than the time of divergence of teleosts from the main line of evolution leading to tetrapods.  相似文献   
102.
103.
104.
105.
106.
107.
108.
109.
110.
Blood total antioxidant capacity (TAC) has become a key bio‐marker for animal health. Forest‐grazing cattle are known to forage various native plants that have high TAC. This study evaluated differences of plasma TAC between forest‐grazing (FG) and pasture‐grazing cattle (PG). Experiment 1 monitored the plasma TAC levels of 32 Japanese Black cattle. The level in PG did not change throughout the grazing period. However, that in FG, which increased from summer, was significantly higher than that in PG through fall (P < 0.05). In experiment 2, we used nine Japanese Black heifers and investigated their blood antioxidant parameters and the TAC in plants that the cattle consumed in late June and September. The plasma TAC levels in FG were significantly higher than those in PG in both periods (P < 0.05). Plasma levels of lipid peroxidation in FG tended to be lower than that in PG (P = 0.098). Furthermore, the TAC levels in various species of shrubs and trees consumed by FG were higher than those in pasture grasses. Results of this study show that plasma TAC of grazing Japanese Black cattle in forestland increase from summer through fall.  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