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   58738篇
  免费   3298篇
  国内免费   37篇
林业   3051篇
农学   2213篇
基础科学   351篇
  7430篇
综合类   6825篇
农作物   2100篇
水产渔业   3186篇
畜牧兽医   32897篇
园艺   725篇
植物保护   3295篇
  2019年   496篇
  2018年   955篇
  2017年   1036篇
  2016年   1007篇
  2015年   866篇
  2014年   1011篇
  2013年   2320篇
  2012年   1806篇
  2011年   2197篇
  2010年   1436篇
  2009年   1369篇
  2008年   2031篇
  2007年   2043篇
  2006年   1932篇
  2005年   1789篇
  2004年   1684篇
  2003年   1667篇
  2002年   1537篇
  2001年   2332篇
  2000年   2186篇
  1999年   1722篇
  1998年   684篇
  1997年   623篇
  1996年   601篇
  1995年   671篇
  1994年   572篇
  1993年   558篇
  1992年   1262篇
  1991年   1397篇
  1990年   1450篇
  1989年   1331篇
  1988年   1244篇
  1987年   1231篇
  1986年   1167篇
  1985年   1104篇
  1984年   917篇
  1983年   723篇
  1982年   524篇
  1979年   792篇
  1978年   616篇
  1977年   469篇
  1976年   524篇
  1975年   502篇
  1974年   625篇
  1973年   605篇
  1972年   633篇
  1971年   603篇
  1970年   588篇
  1969年   537篇
  1967年   497篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
74.
Annelids     
  相似文献   
75.
76.
Quantitative and qualitative bacterial assays were performed on the skin of 15 normal and 32 seborrheic dogs. Nonionic detergent scrubs were made on areas demarcated by glass sidearm cylinders. Quantitative analysis was accomplished by the serial dilution technique, and the bacteria were identified by individual and colonial morphology and by enzyme production. Areas measured on control dogs had a markedly lower total bacterial count than similar areas measured on seborrheic animals. Control dogs had a flora consisting primarily of coagulase-negative cocci, whereas seborrheic dogs usually had a cutaneous flora composed primarily of Stahylococcus aureus, coagulase-positive.  相似文献   
77.
Pseudomonas fluorescens strain Pf1, inhibitory to the growth of the rice blast pathogen Pyricularia oryzae in vitro , was developed as a talc-based powder formulation. When rice seeds were treated with this formulation, the bacteria spread to roots, stems and leaves of the plants and protected against leaf infection by P. oryzae . When applied as a foliar spray, the bacteria survived on the leaves. The powder formulation controlled leaf blast under greenhouse conditions. In tests as a seed treatment and foliar spray in four field trials it effectively controlled the disease and increased grain yield.  相似文献   
78.
The activity of the ovary-inhibiting hormone in the eyestalks of female prawns, Parapenaeopsis hardwickii, was determined during its ovarian developmental cycle. In the inactive (stage I) and post-spawned phases of ovarian development, the ovary-inhibiting hormone activity was found to be very high. During the phase of full vitellogenesis (stage IV), the inhibiting activity is almost negligible. After spawning (stage V) it is present, but at a lower level than during inactive and post-spawned phases. Hence it is inferred that ovary-inhibiting hormone appears to be responsible for the phase of ovarian quiescence and to control the rate of vitellogenesis.  相似文献   
79.
Evolution of C2H4 from soils under anaerobic conditions was stimulated by amendment with cereal straw, but hay had little effect. Temporary restoration of aerobic conditions resulted in large increases in C3 and C4 hydrocarbons, with both straw and hay amendments. Several known products of the fermentative degradation of carbohydrate increased the evolution of hydrocarbons under anaerobic, and to a greater extent, under aerobic conditions. In particular, ethanol and butyric acid promoted the formation of C2H4 and propylene, respectively. The association between degradation products and C2H4 suggests that both may be implicated when root growth is adversely affected by the anaerobic decomposition of plant residues.  相似文献   
80.
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