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   276847篇
  免费   15697篇
  国内免费   673篇
林业   24121篇
农学   14153篇
基础科学   2984篇
  44699篇
综合类   28528篇
农作物   17541篇
水产渔业   17566篇
畜牧兽医   112724篇
园艺   6376篇
植物保护   24525篇
  2021年   2524篇
  2020年   2920篇
  2019年   3707篇
  2018年   4287篇
  2017年   4700篇
  2016年   4995篇
  2015年   4454篇
  2014年   5801篇
  2013年   16368篇
  2012年   7062篇
  2011年   9255篇
  2010年   7793篇
  2009年   8277篇
  2008年   8586篇
  2007年   7681篇
  2006年   8018篇
  2005年   7167篇
  2004年   7053篇
  2003年   6840篇
  2002年   6105篇
  2001年   7475篇
  2000年   7178篇
  1999年   6405篇
  1998年   4277篇
  1997年   4340篇
  1996年   4050篇
  1995年   4625篇
  1994年   4017篇
  1993年   3697篇
  1992年   4981篇
  1991年   5161篇
  1990年   4872篇
  1989年   4814篇
  1988年   4247篇
  1987年   4331篇
  1986年   4201篇
  1985年   4456篇
  1984年   4021篇
  1983年   3723篇
  1982年   3011篇
  1981年   2904篇
  1980年   2847篇
  1979年   3416篇
  1978年   3082篇
  1977年   2777篇
  1976年   2653篇
  1975年   2585篇
  1974年   2767篇
  1973年   2706篇
  1972年   2411篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In a feeding trial lasting for months Halothane-positive fattening pigs were put on a diet containing different concentrations of vitamin E and selenium. After a Myostress application vitamin E and selenium were additionally injected in order to examine stress resistance (CK-test) and regenerative capacity (histological examination of Musculus longissimus dorsi) of skeletal muscle. The study revealed that neither high dietary levels of vitamin E/selenium nor a vitamin E/selenium treatment applied after stress are capable of preventing stress related myopathy nor can they influence its healing up favourably.  相似文献   
2.
3.
4.
Differences in gas exchange parameters i.e. carbon exchange rate (CER), transpiration (Tr), water vapor conductance (g) were investigated, under a controlled environment, in a semi-dwarf (SD) Triticum aestivum line, its tall (TL) near isoline and the Payne (PA) variety characterized by small leaves. The plants were maintained in: (a) optimal substrate moisture condition (CTR); (b) salinized by watering with a 0.12 m NaCl solution (SLT); (c) water stressed by withholding waterings during a period of six days (STR); (d) stressed and salinized during the same period and with the same saline solution (S + S). CER and Tr were negatively affected by the stresses; SLT and S + S treatments had a higher WUE compared to their respective controls CTR and STR.
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO2 concentration curves contributed to explaining the SD performance.  相似文献   
5.
The proximal straight tubules of the female mouse kidney exhibit heavy periodic acid Schiff (PAS) staining in their brush borders and numerous cytoplasmic granules. In the present study, the female DBA/2Cr mouse kidney was examined, using various fixatives (formalin, PFA, PLP, Zamboni's, Bouin, or Carnoy solution) and various staining methods (HE, PAS, alcian blue, periodic acid methenamine-silver (PAM), toluidine blue, azan, or Congo red). Under azan and PAM, the staining pattern of the brush border was similar to that of PAS, and few effects of the fixative were observed. Cytoplasmic granules were clearly detected with PAM as well as PAS. However, these granules were not detected with Carnoy solution. Furthermore, distribution of granules differed between PAS and PAM.  相似文献   
6.
7.
Abstract. A humoral antibody response was demonstrated by ELISA in rainbow trout immunized intraperitoneally with extracts from the branchiuran ectoparasite Argulus foliaceus. A similar immunization protocol produced a higher titre response in a rabbit. Both trout and rabbit identified several antigenic components on immunoblots. ELISA and immunoblotting indicated that rainbow trout and rabbit anti-A. foliaceus sera identified components from the parasitic copepods Lepeophtheirus salmonis and Caligus elongatus.  相似文献   
8.
9.
对5个无核葡萄品种的试验表明,不同培养方式对离体胚发育的影响是很明显的,其中4个品种胚发育率液体培养高于固体培养,‘京早晶’在液体培养中胚发育率高达73.7%,是目前国内外胚发育率最高的报道;液体培养比固体培养胚的发育程度高,发育整齐,无畸形胚,易成苗.  相似文献   
10.
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