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   793695篇
  免费   8540篇
  国内免费   2235篇
化学   411698篇
晶体学   11300篇
力学   38373篇
综合类   26篇
数学   105232篇
物理学   237841篇
  2021年   7046篇
  2020年   7670篇
  2019年   8578篇
  2018年   11198篇
  2017年   11162篇
  2016年   16326篇
  2015年   9586篇
  2014年   15300篇
  2013年   35815篇
  2012年   27625篇
  2011年   33346篇
  2010年   24299篇
  2009年   24070篇
  2008年   31265篇
  2007年   30999篇
  2006年   28639篇
  2005年   25611篇
  2004年   23742篇
  2003年   21153篇
  2002年   20938篇
  2001年   22660篇
  2000年   17508篇
  1999年   13675篇
  1998年   11574篇
  1997年   11280篇
  1996年   10802篇
  1995年   9775篇
  1994年   9695篇
  1993年   9361篇
  1992年   10127篇
  1991年   10485篇
  1990年   10151篇
  1989年   9815篇
  1988年   9679篇
  1987年   9518篇
  1986年   9042篇
  1985年   11691篇
  1984年   12087篇
  1983年   9924篇
  1982年   10302篇
  1981年   9897篇
  1980年   9298篇
  1979年   9996篇
  1978年   10302篇
  1977年   10179篇
  1976年   10066篇
  1975年   9547篇
  1974年   9418篇
  1973年   9590篇
  1972年   6914篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE.  相似文献   
82.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  相似文献   
83.

The problem of the minimax testing of the Poisson process intensity \({\mathbf{s}}\) is considered. For a given intensity \({\mathbf{p}}\) and a set \(\mathcal{Q}\), the minimax testing of the simple hypothesis \(H_{0}: {\mathbf{s}} = {\mathbf{p}}\) against the composite alternative \(H_{1}: {\mathbf{s}} = {\mathbf{q}},\,{\mathbf{q}} \in \mathcal{Q}\) is investigated. The case, when the 1-st kind error probability \(\alpha \) is fixed and we are interested in the minimal possible 2-nd kind error probability \(\beta ({\mathbf{p}},\mathcal{Q})\), is considered. What is the maximal set \(\mathcal{Q}\), which can be replaced by an intensity \({\mathbf{q}} \in \mathcal{Q}\) without any loss of testing performance? In the asymptotic case (\(T\rightarrow \infty \)) that maximal set \(\mathcal{Q}\) is described.

  相似文献   
84.
Journal of Sol-Gel Science and Technology - High temperature stable brookite rich titanium dioxide of average crystallite size 20&;nbsp;nm has been prepared by a novel aqueous sol–gel...  相似文献   
85.
Saleh  Z. M.  Nasser  H.  Özkol  E.  Günöven  M.  Abak  K.  Canli  S.  Bek  A.  Turan  R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting...  相似文献   
86.
87.
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.  相似文献   
88.
89.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
90.
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