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   750篇
  免费   37篇
  2023年   3篇
  2022年   6篇
  2021年   12篇
  2020年   7篇
  2019年   5篇
  2018年   11篇
  2017年   9篇
  2016年   22篇
  2015年   25篇
  2014年   29篇
  2013年   45篇
  2012年   57篇
  2011年   46篇
  2010年   27篇
  2009年   32篇
  2008年   32篇
  2007年   54篇
  2006年   41篇
  2005年   25篇
  2004年   26篇
  2003年   33篇
  2002年   24篇
  2001年   16篇
  2000年   25篇
  1999年   20篇
  1998年   5篇
  1997年   6篇
  1996年   4篇
  1995年   3篇
  1994年   5篇
  1993年   10篇
  1992年   19篇
  1991年   14篇
  1990年   12篇
  1989年   10篇
  1988年   4篇
  1987年   13篇
  1986年   8篇
  1985年   3篇
  1984年   4篇
  1982年   4篇
  1981年   2篇
  1978年   3篇
  1977年   2篇
  1975年   2篇
  1974年   5篇
  1970年   4篇
  1969年   3篇
  1968年   2篇
  1961年   1篇
排序方式: 共有787条查询结果,搜索用时 0 毫秒
781.
Primates - Examining interactions among sympatric primate species can provide interesting information about competition, cooperation, and avoidance between those species. Those interactions can be...  相似文献   
782.
Performance and phenology of alpine herbs along a snow-melting gradient   总被引:1,自引:0,他引:1  
Responses of plants to the length of the growing season were studied in an alpine snow-bed by setting five plots along a snow-melting gradient. Performance and phenology were compared between the plots for five herbaceous species (Peucedanum multivittatum, Primula cuneifolia, Veronica stelleri var.longistyla, Solidago virga-aurea var.leiocarpa andPotentilla matsumurae). Performance characteristics measured were flower height, leaf height, leaf number, flower number and fruit number. In the late exposed plots with short snow-free periods, fruit-set was reduced in many species due to the decrease in flower number and/or the short growing season for fruit development.Veronica stelleri var.longistyla andSolidago virga-aurea var.leiocarpa, which decreased in flower and leaf numbers due to the short snow-free period, were sensitive to the short growing season.Peucedanum multivittatum was vigorous in the late exposed plots, but its slow flowering and fruiting prevented the fruit-set from developing in the last exposed plot.Primula cumeifolia andPotentilla matsumurae, quick flowering species that maintained their flower number throught the snow-melting gradient, were considered the most successful species in late exposed habitats.  相似文献   
783.
When carrying out experiments on the production of the edible mushroom Pleurotus sajor-caju in the Laboratory of Edible Mushrooms, Universidade Federal de Lavras, Lavras, Brazil, in the second half of 2007, the presence of beetles later identified as belonging to the species Mycotretus apicalis was verified. This is the first recorded instance of this insect in cultures of P. sajor-caju in Brazil. The larvae and adults of this insect feed on the fruiting bodies of commercial harvests, resulting in reduction in mushroom quality. To provide evaluation of the injuries caused by these insects, substrates colonized by P. sajor-caju were infested with 4, 8, 16, 32 and 64 insects per block of substrate being the qualitative and quantitative losses then noted. Despite the lack of an observed decrease in biological efficiency, the injuries caused by these insects affected the commercial quality of the mushrooms, which may result in economic losses. The results showed that infestations of 32 insects per 0.8 kg of substrate led to a depreciation in the prices of mushrooms meant to be sold.  相似文献   
784.
785.
786.
787.
Antibodies against the cuticle surface of Trichinella spiralis muscle larvae were purified by means of immunoaffinity chromatography and incubated with ultrathin sections of muscle larvae. Major constituents of the parasite reactive with the purified antibodies included the cuticle surface, stichocyte alpha-granules, and the esophagus occupying substance of the muscle larvae. Thus the present data suggest that the cuticle surface is an antigenically different entity from the cuticle inner layers and its origin is likely stichocyte alpha-granules.  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