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   324202篇
  免费   2124篇
  国内免费   1096篇
化学   141064篇
晶体学   3993篇
力学   19011篇
综合类   36篇
数学   67797篇
物理学   95521篇
  2020年   1345篇
  2019年   1381篇
  2018年   18484篇
  2017年   19017篇
  2016年   11529篇
  2015年   3443篇
  2014年   3196篇
  2013年   7541篇
  2012年   12612篇
  2011年   26880篇
  2010年   16106篇
  2009年   16548篇
  2008年   21758篇
  2007年   26862篇
  2006年   6436篇
  2005年   13520篇
  2004年   9676篇
  2003年   9451篇
  2002年   6750篇
  2001年   5104篇
  2000年   4237篇
  1999年   3033篇
  1998年   2667篇
  1997年   2528篇
  1996年   2505篇
  1995年   2300篇
  1994年   2234篇
  1993年   2063篇
  1992年   2258篇
  1991年   2404篇
  1990年   2214篇
  1989年   2182篇
  1988年   2135篇
  1987年   2023篇
  1986年   1934篇
  1985年   2538篇
  1984年   2679篇
  1983年   2176篇
  1982年   2355篇
  1981年   2223篇
  1980年   2151篇
  1979年   2293篇
  1978年   2450篇
  1977年   2269篇
  1976年   2334篇
  1975年   2189篇
  1974年   2232篇
  1973年   2263篇
  1972年   1458篇
  1971年   1275篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
3.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
4.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
5.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron...  相似文献   
6.
Investigated is the dependency of the crack tip opening displacement (CTOD) on the local microstructure of the heat affected zone in high-strength low-alloy (HSLA) microalloyed steel. Since the initiation of the crack tip location could not be controlled in fatigue, any possible correlation between heat iput in welding and fracture toughness could be smeared. Modified CTOD data are defined; they show that the fracture resistance of the weld joint decreased as the heat input increased.  相似文献   
7.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields.  相似文献   
8.
The first results regarding the formation of a two-dimensional periodic structure of local melting regions on a silicon surface upon pulsed light irradiation are presented. The conditions are established, and the mechanism of the formation of such structures is discussed. Zh. Tekh. Fiz. 67, 97–99 (December 1997)  相似文献   
9.
10.
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