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   154945篇
  免费   1406篇
  国内免费   400篇
化学   83477篇
晶体学   2041篇
力学   6700篇
综合类   7篇
数学   15735篇
物理学   48791篇
  2020年   1134篇
  2019年   1205篇
  2018年   1498篇
  2017年   1476篇
  2016年   2503篇
  2015年   1571篇
  2014年   2462篇
  2013年   6417篇
  2012年   5004篇
  2011年   6380篇
  2010年   4354篇
  2009年   4348篇
  2008年   5797篇
  2007年   5850篇
  2006年   5508篇
  2005年   5091篇
  2004年   4517篇
  2003年   3947篇
  2002年   3967篇
  2001年   4353篇
  2000年   3348篇
  1999年   2593篇
  1998年   2255篇
  1997年   2202篇
  1996年   2031篇
  1995年   1910篇
  1994年   1913篇
  1993年   1747篇
  1992年   2015篇
  1991年   2140篇
  1990年   1945篇
  1989年   1936篇
  1988年   1873篇
  1987年   1769篇
  1986年   1711篇
  1985年   2230篇
  1984年   2355篇
  1983年   1920篇
  1982年   2105篇
  1981年   1993篇
  1980年   1919篇
  1979年   2055篇
  1978年   2226篇
  1977年   2098篇
  1976年   2133篇
  1975年   2047篇
  1974年   2104篇
  1973年   2087篇
  1972年   1369篇
  1971年   1221篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
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   
3.
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   
4.
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   
5.
We present the results of an experimental investigation of a RF splitting of57Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field.  相似文献   
6.
7.
Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989.  相似文献   
8.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed.  相似文献   
9.
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined.  相似文献   
10.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 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