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   689172篇
  免费   6555篇
  国内免费   1759篇
化学   353607篇
晶体学   10127篇
力学   34030篇
综合类   26篇
数学   90376篇
物理学   209320篇
  2021年   5827篇
  2020年   6518篇
  2019年   7318篇
  2018年   9775篇
  2017年   9899篇
  2016年   13934篇
  2015年   7743篇
  2014年   12755篇
  2013年   30198篇
  2012年   23137篇
  2011年   27526篇
  2010年   20327篇
  2009年   20065篇
  2008年   25991篇
  2007年   25978篇
  2006年   23903篇
  2005年   21310篇
  2004年   19735篇
  2003年   17841篇
  2002年   17729篇
  2001年   18807篇
  2000年   14674篇
  1999年   11421篇
  1998年   9894篇
  1997年   9838篇
  1996年   9219篇
  1995年   8340篇
  1994年   8475篇
  1993年   8042篇
  1992年   8633篇
  1991年   9063篇
  1990年   8722篇
  1989年   8479篇
  1988年   8402篇
  1987年   8260篇
  1986年   7850篇
  1985年   10183篇
  1984年   10719篇
  1983年   9029篇
  1982年   9372篇
  1981年   8909篇
  1980年   8594篇
  1979年   8985篇
  1978年   9473篇
  1977年   9336篇
  1976年   9340篇
  1975年   8833篇
  1974年   8734篇
  1973年   9044篇
  1972年   6568篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A model describing the roles of bound and unbound vacancies is proposed in order to predict defect decay and short-range-order kinetics of quenched binary alloys during linear heating experiments. This is an alternative treatment of a previous approach. The model has been applied to the differential scanning calorimetry (DSC) curves of Cu-5 at.% Zn quenched from different temperatures. An expression to calculate the activation energy for migration of solute-vacancy complexes was also developed which make use of DSC trace data. A value of 89.12±0.32 kJ mol-1 was obtained for the above alloy. The relative contribution of bound and unbound vacancies to partition of effective activation energy corresponding to the ordering process as influenced by quenching temperature was also assessed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
992.
Various antimonate compounds are well known as important inorganic ion exchangers, since they resist radiation and chemical degradation and also exhibit selectivities towards different cations. Ceric, silicon, titanium and ferric antimonates were prepared as inorganic ion exchangers. Characterization of these materials has been described using different techniques, including thermal analysis, surface area measurements, X-ray diffraction and IR-spectroscopy. In batch distribution experiments the influence of HNO3 molarity and Mo concentration for Mo sorption on different matrices is described in terms of their retention capacities and distribution coefficients.The selectivities of these exchangers towards molybdenum are in the order: CeSb > SiSb > FeSb > TiSb.  相似文献   
993.
Results of two urgent and practically important directions of research on the indirect oxidation of organic compounds by highly reactive intermediates generated electrochemically from oxygen (HO2 , HO2 ·, HO·) are considered and orderly arranged. The studies in question are the indirect synthesis and mineralization of organic toxicants in waste water.  相似文献   
994.
The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg3Si2O5(OH)4 filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes.  相似文献   
995.
Times of longitudinal T 1b and transverse T 2b magnetic relaxation of hexane and decane molecules in micropores of ZSM-5 silicalite were measured as functions of the content of these liquid n-alkanes in zeolite and of temperature. The stepwise changes in the T 1b and T 2b times were revealed in the region of 8% content of hydrocarbons. The observed changes in the concentration and temperature dependences of T 1b and T 2b times are explained by the rearrangement of silicalite crystal lattice under the action of adsorbed molecules.  相似文献   
996.
997.
998.
999.
1000.
 The Belavkin equation, describing the continuous measurement of the position of a quantum particle, is studied. A rigorous representation of its solution by means of an infinite dimensional oscillatory integral (Feynman path integral) defined on the complex Cameron-Martin space is given. Received: 7 January 2002 / Revised version: 20 June 2002 / Published online: 19 December 2002 Mathematics Subject Classification (2000): 81, 81S40, 60H15 Key words or phrases: Belavkin equation – Continuous measurement – Quantum theory – Oscillatory integrals – Feynman path integrals  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