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   333571篇
  免费   2749篇
  国内免费   1115篇
化学   145959篇
晶体学   4405篇
力学   19563篇
综合类   7篇
数学   68326篇
物理学   99175篇
  2021年   1029篇
  2020年   1167篇
  2019年   1202篇
  2018年   18373篇
  2017年   19045篇
  2016年   11184篇
  2015年   3568篇
  2014年   2947篇
  2013年   8257篇
  2012年   13582篇
  2011年   28450篇
  2010年   16608篇
  2009年   17104篇
  2008年   23130篇
  2007年   28201篇
  2006年   7634篇
  2005年   15052篇
  2004年   10931篇
  2003年   10263篇
  2002年   7392篇
  2001年   6451篇
  2000年   5159篇
  1999年   3690篇
  1998年   2881篇
  1997年   2806篇
  1996年   2967篇
  1995年   2512篇
  1994年   2345篇
  1993年   2219篇
  1992年   2497篇
  1991年   2465篇
  1990年   2152篇
  1989年   2144篇
  1988年   2175篇
  1987年   2105篇
  1986年   2004篇
  1985年   2933篇
  1984年   2922篇
  1983年   2357篇
  1982年   2542篇
  1981年   2419篇
  1980年   2384篇
  1979年   2330篇
  1978年   2420篇
  1977年   2248篇
  1976年   2214篇
  1975年   2193篇
  1974年   2081篇
  1973年   2204篇
  1972年   1238篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse.  相似文献   
53.
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages.  相似文献   
54.
55.
56.
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   
57.
58.
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   
59.
Echabaane  M.  Hfaiedh  S.  Smiri  B.  Saidi  F.  Dridi  C. 《Journal of Solid State Electrochemistry》2021,25(6):1797-1806
Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor...  相似文献   
60.

A model with 16 moments is here presented in the framework of RET of polyatomic gases. It furnishes as principal subsystem the relativistic counterpart of a work by Arima T., Ruggeri T., Sugiyama M.; this is present in literature and treats the non relativistic case which incorporates relaxation processes of molecular rotation and vibration. Another principal subsystem is the natural extension of the 14 moments model by Pennisi S. and Ruggeri T.; this is also present in literature in the relativistic framework but where the trace of the third balance equation is neglected. Its extension is found here for the case when this trace isn’t neglected.

  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