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   214886篇
  免费   1784篇
  国内免费   627篇
化学   117798篇
晶体学   2934篇
力学   8371篇
综合类   6篇
数学   23353篇
物理学   64835篇
  2020年   1982篇
  2019年   2270篇
  2018年   3221篇
  2017年   3131篇
  2016年   4282篇
  2015年   2388篇
  2014年   3839篇
  2013年   9316篇
  2012年   6924篇
  2011年   8490篇
  2010年   6103篇
  2009年   5941篇
  2008年   8168篇
  2007年   8241篇
  2006年   7660篇
  2005年   6956篇
  2004年   6182篇
  2003年   5656篇
  2002年   5523篇
  2001年   5954篇
  2000年   4691篇
  1999年   3472篇
  1998年   3015篇
  1997年   3039篇
  1996年   2829篇
  1995年   2322篇
  1994年   2422篇
  1993年   2452篇
  1992年   2598篇
  1991年   2657篇
  1990年   2560篇
  1989年   2533篇
  1988年   2463篇
  1987年   2434篇
  1986年   2357篇
  1985年   2989篇
  1984年   3149篇
  1983年   2502篇
  1982年   2781篇
  1981年   2659篇
  1980年   2466篇
  1979年   2688篇
  1978年   2797篇
  1977年   2833篇
  1976年   2801篇
  1975年   2661篇
  1974年   2637篇
  1973年   2787篇
  1972年   1850篇
  1967年   1830篇
排序方式: 共有10000条查询结果,搜索用时 40 毫秒
51.
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...  相似文献   
52.
Bruzy  N.  Coret  M.  Huneau  B.  Kermouche  G.  Mondon  M.  Bertrand  E.  Stainier  L. 《Experimental Mechanics》2019,59(8):1145-1157

The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α ? γ and γ ? α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.

  相似文献   
53.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
54.
55.

A procedure was suggested for preparing brominated polyols of reduced viscosity for the synthesis of foamed polyurethanes of reduced flammability. The flame-retarding action of the synthesized polyol tetrabromophthalate in polyurethane was studied in comparison with that of other widely used flame retardants. Evaluation of the effect exerted on the flammability of the polurethane compound by the polyol tetrabromophthalate synthesized, melamine, and aluminum hydroxide shows that all the samples containing flame retardants are self-extinguishing. The shortest combustion time was observed for the sample containing 6% polyol tetrabromophthalate synthesized. The sample containing as a flame retardant additive solely the synthesized polyole tetrabromophthalate also exhibits the highest performance as a heat-insulating material from the viewpoint of thermal conductivity.

  相似文献   
56.
Russian Physics Journal - The article describes the collocation method for the numerical solution of mathematical physics boundary value problems. By arranging the collocation nodes in a special...  相似文献   
57.
Crystallography Reports - The specific features of the formation of concentration inhomogeneities in crystals grown by the Czochralski method (GaSb:Te, Ge:Ga) and by the Bridgman method...  相似文献   
58.
Crystallography Reports - The studies of wide-gap semiconductor materials using electron-beam induced current (EBIC) method are reviewed. The main methods for measuring the diffusion length of...  相似文献   
59.
Vorob’ev  N. T.  Lantsetova  E. D. 《Mathematical Notes》2021,110(5-6):655-665
Mathematical Notes - It is proved that the lattice of all Fitting classes of finite groups is not distributive, and conditions under which Fitting classes satisfy the distributive and modular laws...  相似文献   
60.
Journal of Applied Spectroscopy - Aqueous solutions of human hemoglobin have been studied by the multi-angle static light scattering method. The tendency of sickle-shaped erythrocytes to aggregate...  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