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   237349篇
  免费   2846篇
  国内免费   461篇
化学   128449篇
晶体学   3669篇
力学   10954篇
综合类   10篇
数学   26654篇
物理学   70920篇
  2021年   2401篇
  2020年   2602篇
  2019年   3117篇
  2018年   4378篇
  2017年   4348篇
  2016年   6135篇
  2015年   3405篇
  2014年   5377篇
  2013年   10852篇
  2012年   9247篇
  2011年   10687篇
  2010年   7942篇
  2009年   7896篇
  2008年   9865篇
  2007年   9833篇
  2006年   8617篇
  2005年   7686篇
  2004年   7032篇
  2003年   6300篇
  2002年   6183篇
  2001年   6342篇
  2000年   4790篇
  1999年   3622篇
  1998年   3046篇
  1997年   3034篇
  1996年   2958篇
  1995年   2495篇
  1994年   2591篇
  1993年   2558篇
  1992年   2810篇
  1991年   2827篇
  1990年   2724篇
  1989年   2769篇
  1988年   2676篇
  1987年   2699篇
  1986年   2543篇
  1985年   3262篇
  1984年   3297篇
  1983年   2743篇
  1982年   2698篇
  1981年   2646篇
  1980年   2431篇
  1979年   2809篇
  1978年   2772篇
  1977年   2961篇
  1976年   2951篇
  1975年   2745篇
  1974年   2671篇
  1973年   2795篇
  1972年   2126篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
The metallacarborane [3,3′‐Co(1,2‐closo‐C2B9H11)2]? has been synthesized. This species allows the formation of redox couples in which both partners are negatively charged. The E1/2 potential can be tuned by adjusting the nature and number of substituents on B and C. The octaiodinated species [3,3′‐Co(1,2‐closo‐C2B9H7I4)2]? is the most favorable, as it is isolatable and stable in air. A DFT study on stability and redox potentials of complexes has been performed.  相似文献   
93.
Journal of Experimental and Theoretical Physics - The nature of the training effect in exchange-biased compounds is studied. This effect consists in a decrease in the exchange bias field (HEB)...  相似文献   
94.
95.
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   
96.
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   
97.
Russian Journal of Organic Chemistry - Methyl (Z)-3-[(2R,3R,4S,5S)-5-(2-methoxy-2-oxoethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran-2-yl]-prop-2-enoate was synthesized, and its intramolecular...  相似文献   
98.
99.
Syrovatka  R. A.  Lipaev  A. M.  Naumkin  V. N.  Klumov  B. A. 《JETP Letters》2022,116(12):869-874
JETP Letters - A quasi-two-dimensional plasma crystal in (3 + 1) dimensions has been experimentally observed for the first time; i.e., three spatial coordinates of each microparticles of the...  相似文献   
100.

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   
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