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   311096篇
  免费   17209篇
  国内免费   673篇
林业   24453篇
农学   14212篇
基础科学   2999篇
  45706篇
综合类   41817篇
农作物   17318篇
水产渔业   18174篇
畜牧兽医   132383篇
园艺   6520篇
植物保护   25396篇
  2020年   2974篇
  2019年   3783篇
  2018年   4541篇
  2017年   5021篇
  2016年   5139篇
  2015年   4500篇
  2014年   5877篇
  2013年   16483篇
  2012年   8211篇
  2011年   10680篇
  2010年   8244篇
  2009年   8699篇
  2008年   9980篇
  2007年   9162篇
  2006年   9381篇
  2005年   8684篇
  2004年   8453篇
  2003年   8050篇
  2002年   7226篇
  2001年   8190篇
  2000年   7843篇
  1999年   6783篇
  1998年   4089篇
  1997年   4122篇
  1996年   3966篇
  1995年   4801篇
  1994年   4158篇
  1993年   3880篇
  1992年   5630篇
  1991年   5817篇
  1990年   5484篇
  1989年   5560篇
  1988年   4961篇
  1987年   5046篇
  1986年   5130篇
  1985年   5214篇
  1984年   4612篇
  1983年   4249篇
  1982年   3325篇
  1981年   3172篇
  1980年   3123篇
  1979年   4104篇
  1978年   3527篇
  1977年   3198篇
  1976年   3073篇
  1975年   3067篇
  1974年   3383篇
  1973年   3377篇
  1972年   3062篇
  1971年   2981篇
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
71.
Eurasian Soil Science - The impact of three types of pesticides (herbicide metribuzin, insecticide imidacloprid, and fungicide benomyl) on the structure of microbial complexes and indicators of...  相似文献   
72.
Eurasian Soil Science - In this study, we developed a general mathematical relationship to determine hydraulic tortuosity. An optimization code was run in MATLAB R2014a software, using Monte Carlo...  相似文献   
73.
Eurasian Soil Science - This article presents the results of research on the impact of no-till technology on the natural bulk density and macro- and microaggregate composition of the topsoil...  相似文献   
74.
Eurasian Soil Science - The content and profile distribution of 137Cs in iron-illuvial dwarf and shallow-podzolic podzols (Albic Podzols) under bilberry-lichen and green-lichen-bilberry pine...  相似文献   
75.
76.
77.
78.
79.
To determine whether senescing leaves provoke an active nitrogen (N) remobilization that results in the reduction of nitrogenase activity, 60% of Medicago truncatula lower leaves were either darkened or individually excised for two weeks. Although a considerable amount of N was remobilized, N2 fixation activity was found to be increased to maintain the N source/sink balance, indicating an absence of the negative N‐feedback regulation of nitrogenase activity in the senescing M. truncatula.  相似文献   
80.
Background: Nitrogen losses is an economic problem for wheat production and a high risk to the environment. Therefore, improved N fertilizer management is a key to increasing the N efficiency and minimizing N losses. To increase N efficiency, enhanced fertilizers such as urea combined with urease inhibitor can be used. Aims: The aim of present study was to evaluate the effects of different N forms on grain storage protein subunits in winter wheat and to examine whether the observed changes correlate with parameters of baking quality. Methods: The investigation was performed over two consecutive years at two locations in Germany. Protein subunits were analyzed by SDS‐PAGE. Results: Protein concentrations were similarly increased after fertilization with ammonium nitrate and urea + urease inhibitor. Analysis of the individual storage protein fractions indicated that both fertilizers specifically enhanced ω‐gliadins and HMW glutenins, but the effect was more pronounced in the ammonium nitrate treatment. Application of urea + urease inhibitor had greater influence on the protein composition and resulted in higher specific baking volume as well as the best fresh keeping ability, in comparison with urea treatment. Conclusion: Considering that the urea + urease inhibitor treatment resulted in almost comparable improvements of NUE and baking quality, with the additional benefit of reduced N losses in combination with easy handling, urea + urease inhibitor can be recommended as a viable alternative to both urea alone and ammonium nitrate treatments. This opens up an opportunity for the reduction of N loss in wheat production when use of urea is preferred.  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