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   122982篇
  免费   374篇
  国内免费   816篇
  2023年   14篇
  2022年   60篇
  2021年   103篇
  2020年   59篇
  2019年   86篇
  2018年   14415篇
  2017年   13521篇
  2016年   9189篇
  2015年   822篇
  2014年   418篇
  2013年   486篇
  2012年   5537篇
  2011年   16201篇
  2010年   15108篇
  2009年   11189篇
  2008年   12719篇
  2007年   15072篇
  2006年   364篇
  2005年   1675篇
  2004年   1421篇
  2003年   1669篇
  2002年   1354篇
  2001年   349篇
  2000年   313篇
  1999年   44篇
  1998年   12篇
  1997年   28篇
  1996年   34篇
  1995年   11篇
  1994年   16篇
  1993年   48篇
  1992年   34篇
  1991年   76篇
  1990年   18篇
  1989年   32篇
  1988年   23篇
  1987年   25篇
  1984年   20篇
  1983年   28篇
  1982年   19篇
  1981年   8篇
  1975年   14篇
  1972年   717篇
  1971年   669篇
  1970年   8篇
  1965年   18篇
  1962年   28篇
  1956年   13篇
  1944年   19篇
  1940年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
Starfish waste has been shown to be an effective compost material not only in the promotion of plant growth but also in terms of having insecticidal activity. In the present study, plant growth regulation by chemicals from starfish was examined. The aqueous fraction from a hot water extract of the starfish Asterias amurensis Lütken showed plant-growth activity, while the aqueous fraction from a methanol extract inhibited growth of Brassica campestris. The lipophilic fraction from the methanol extract also exhibited a plant growth-promoting effect. The active components from each extract were identified. Asterubine from the hot water extract promoted plant growth. A ceramide from the lipophilic fraction showed root growth promoting effect, and three glucocerebrosides had promotive effects on the entire plant. Asterosaponins were identified as the main growth inhibitors in the aqueous fraction of the methanol extract. These active compounds from starfish waste could be analyzed as potential plant growth regulators in agricultural applications in the future.  相似文献   
232.
233.
This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord. Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement by non-notochordal cells.  相似文献   
234.
235.
236.
237.
As applied to a tokomak, a magnetic trap for confinement of a plasma with an inverted field or a magnetic field reversed configuration (FRC) is one of the most promising alternatives of the systems with high β. A brief review of the latest data on FRC and potential directions of using such configurations in addition to energy generation in thermonuclear reactors (TNRs) is proposed.  相似文献   
238.
239.
240.
We screened a total of 460 stool samples from humans with and without underlying disease for the black yeast and neurotrope, Exophiala dermatitidis using conventional and molecular identification procedures. Sixteen (3.5%) samples were positive. Twelve out of the sixteen positive samples where the fungus was recovered were from individuals who had diarrhoea at the moment of isolation. Two asymptomatic positive cases were within the age bracket of 21–30. Susceptibility testing of the strains using the CLSI M38 protocol suggests that almost all the strains were susceptible to amphotericin B, 5 fluorocytosine, itraconazole, fluconazole and voriconazole. Considering the health risk currently posed by this organism in Asia, especially among healthy younger subjects of the population and the scarcity of data on this fungus in Africa in general and Nigeria in particular, some recommendations were suggested.  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