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   1347887篇
  免费   29540篇
  国内免费   7691篇
化学   665155篇
晶体学   20906篇
力学   75878篇
综合类   104篇
数学   245436篇
物理学   377639篇
  2021年   13470篇
  2020年   15910篇
  2019年   16031篇
  2018年   15560篇
  2017年   14243篇
  2016年   29057篇
  2015年   21108篇
  2014年   30414篇
  2013年   74307篇
  2012年   38215篇
  2011年   36907篇
  2010年   39163篇
  2009年   41583篇
  2008年   36015篇
  2007年   32493篇
  2006年   34548篇
  2005年   30054篇
  2004年   30106篇
  2003年   28214篇
  2002年   28608篇
  2001年   26631篇
  2000年   23611篇
  1999年   21957篇
  1998年   20827篇
  1997年   20825篇
  1996年   21022篇
  1995年   19101篇
  1994年   18547篇
  1993年   18085篇
  1992年   17770篇
  1991年   18134篇
  1990年   17305篇
  1989年   17420篇
  1988年   16972篇
  1987年   17008篇
  1986年   15846篇
  1985年   22345篇
  1984年   23649篇
  1983年   19885篇
  1982年   21587篇
  1981年   20845篇
  1980年   20156篇
  1979年   20248篇
  1978年   21642篇
  1977年   21211篇
  1976年   20875篇
  1975年   19543篇
  1974年   19174篇
  1973年   19677篇
  1972年   14157篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Ionic conductivity of dry quaternary ammonium polymer, polydiallyldimethylammonium with Cl and H2PO4 counter ions was studied in a wide range of frequencies (10−2-107 Hz) and temperatures (300-470 K). The data were analysed within the formalism of permittivity. WAXS, and thermal properties of this polymer were investigated prior to conductivity measurements.  相似文献   
952.
The diffraction efficiency and the recording and relaxation times of dynamic reflection holograms, recorded in CdF2 crystals with bistable centers are studied experimentally in the temperature range 20–100°C. In the model experiments which measured the quality of the wave reflected from the hologram, the dynamic wavefront distortions are demonstrated to be efficiently compensated using a holographic corrector based on these crystals. CdF2 crystals with bistable centers are likely to be useful in solving problems of correction of laser light wavefront and image correction in observation telescopes with nonideal primary mirrors.  相似文献   
953.
Algebraic methods in quantum mechanics: from molecules to polymers   总被引:2,自引:0,他引:2  
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years. We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century. Received 21 November 2001  相似文献   
954.
955.
It is shown that any finite dimensionalC 0 manifold (connected and Hausdorff but otherwise unrestricted) has an atlas of cardinality not greater than that of the continuum; while if it has a Hölder continuous pseudo-Riemannian metric then there is a countable atlas.  相似文献   
956.
The adsorption of hydrogen on a clean Cu10%/Ni90% (110) alloy single crystal was studied using flash desorption spectroscopy (FDS), Auger electron spectroscopy (AES), and work function measurements. Surface compositions were varied from 100% Ni to 35% Ni. The hydrogen chemisorption on a-surface of 100% nickel revealed strong attractive interactions between the hydrogen atoms in accordance with previous work on Ni(100). Three desorption states (β1, β2 and α) appeared in the desorption spectra. The highest temperature (α) state was occupied only after the initial population of the β2-state. As the amount of copper was increased in the nickel substrate, desorption from the higher energy binding α-state was reduced, indicating a decrease in the attractive interactions among hydrogen atoms. The hydrogen coverage at saturation was not affected by the addition of copper to the nickel substrate until the copper concentration was greater than 25% at which a sharp reduction in saturation coverage occurred. This phenomenon was apparently due to the adsorption of hydrogen on Ni atoms followed by occupation of NiNi and CuNi bridged adsorption sites, while occupation of CuCu sites was restricted due to an energy barrier to migration.  相似文献   
957.
Squalene-2,3-epoxide: lanosterol cyclase was purified from rat liver in five steps as a soluble and homogeneous protein. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis with a molecular weight of 75 kD. In its native state it behaved as a homo-dimer. The isoelectric point of 5.5 and the apparent Km value for (3S)-squalene-epoxide of 55 microM were estimated for the cyclase.  相似文献   
958.
Translated fromProblemy Ustoichivosti Stokhasticheskikh Modelei. Trudy Seminara, 1988, pp. 115–120.  相似文献   
959.
We study properties of some linear and nonlinear operators which occur in the theory of stochastic differential and integral equations.Translated from Statisticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 148–154, 1988.  相似文献   
960.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 478–484, September, 1991.  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