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   228548篇
  免费   1663篇
  国内免费   760篇
化学   105128篇
晶体学   2781篇
力学   13273篇
综合类   7篇
数学   46683篇
物理学   63099篇
  2020年   1114篇
  2019年   1174篇
  2018年   11717篇
  2017年   11491篇
  2016年   8415篇
  2015年   2363篇
  2014年   2693篇
  2013年   6598篇
  2012年   8581篇
  2011年   16429篇
  2010年   9746篇
  2009年   10178篇
  2008年   12097篇
  2007年   14281篇
  2006年   5588篇
  2005年   6242篇
  2004年   5878篇
  2003年   5774篇
  2002年   4858篇
  2001年   4559篇
  2000年   3587篇
  1999年   2712篇
  1998年   2417篇
  1997年   2318篇
  1996年   2168篇
  1995年   2011篇
  1994年   1960篇
  1993年   1819篇
  1992年   2045篇
  1991年   2181篇
  1990年   1965篇
  1989年   1973篇
  1988年   1917篇
  1987年   1813篇
  1986年   1747篇
  1985年   2242篇
  1984年   2366篇
  1983年   1934篇
  1982年   2122篇
  1981年   2003篇
  1980年   1934篇
  1979年   2075篇
  1978年   2230篇
  1977年   2085篇
  1976年   2128篇
  1975年   2036篇
  1974年   2083篇
  1973年   2084篇
  1972年   1372篇
  1971年   1218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.
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   
4.
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   
5.
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   
6.
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   
7.
8.
9.
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993.  相似文献   
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