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   92732篇
  免费   7164篇
  国内免费   5617篇
化学   24344篇
晶体学   1809篇
力学   4866篇
综合类   476篇
数学   29743篇
物理学   44275篇
  2023年   288篇
  2022年   483篇
  2021年   513篇
  2020年   898篇
  2019年   1232篇
  2018年   1233篇
  2017年   942篇
  2016年   774篇
  2015年   652篇
  2014年   1605篇
  2013年   2671篇
  2012年   1733篇
  2011年   2395篇
  2010年   2901篇
  2009年   7653篇
  2008年   8757篇
  2007年   7249篇
  2006年   6595篇
  2005年   4514篇
  2004年   4271篇
  2003年   4523篇
  2002年   5670篇
  2001年   4093篇
  2000年   3870篇
  1999年   3672篇
  1998年   3042篇
  1997年   2207篇
  1996年   1942篇
  1995年   2362篇
  1994年   2243篇
  1993年   1704篇
  1992年   1211篇
  1991年   926篇
  1990年   749篇
  1989年   638篇
  1988年   596篇
  1987年   437篇
  1985年   995篇
  1984年   668篇
  1983年   515篇
  1982年   665篇
  1981年   817篇
  1980年   737篇
  1979年   579篇
  1978年   594篇
  1977年   553篇
  1976年   549篇
  1975年   321篇
  1974年   358篇
  1973年   464篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
81.
The purpose of this paper is to investigate the problem of approximating fixed points of non-Lipschitizian asymptotically pseudocontractive mappings in an arbitrary real Banach space by the modified Ishikawa iterative sequences with errors.  相似文献   
82.
New radiative lifetime measurements based on time-resolved laser-induced fluorescence techniques are reported for 18 even-parity levels belonging to the 4f5d26p and 4f 25d 2 configurations of Ce I and 6 even-parity levels belonging to the 5d26s, 4f5d6p, and 4f6s6p configurations of Ce II. Free neutral and singly ionized cerium atoms were produced by laser ablation. The Ce I and Ce II levels range in energy from 26 545 to 29 102 cm-1, and 42 573 to 48 152 cm-1, respectively. Received 25 September 2002 Published online 4 March 2003  相似文献   
83.
The fusion evaporation reaction 122Sn(14N, 4n)132La was used to populate the high-spin states of 132La at the beam energy of 60 MeV. A new band consisting of mostly E2 transitions has been discovered. This band has the interesting links to the ground state 2- and the isomeric state 6-. A new transition of energy 351 keV connecting the low-spin states of the positive-parity band based on the πh 11/2 ⊗ νh 11/2 particle configuration, has been found. This has played a very important role in resolving the existing ambiguities and inconsistencies in the spin assignment of the band head. Received: 12 August 2002 / Accepted: 18 March 2003 / Published online: 7 May 2003  相似文献   
84.
辐射传递蒙特卡洛法精度分析及数值试验   总被引:3,自引:1,他引:2  
本文建立了蒙特卡洛法模拟散射参与性介质内辐射传递计算模型。对蒙特卡洛法的计算精度及运行时间进行了较为详细的分析,提出了几种判断计算精度的方法。同时,借助蒙特卡洛法模拟辐射传递过程,进行数值“辐射实验”。利用该“实验结果”进行了物性反问题研究。在已知光学厚度的前提下,得到散射反照率与后半球辐射热流之间的单值函数关系。  相似文献   
85.
Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis.  相似文献   
86.
An exact formalism for the relativistic version of Landau theory of Fermi liquid in presence of strong quantizing magnetic field is developed. Both direct and exchange type interactions with scalar and vector coupling cases are considered.  相似文献   
87.
An effective stability result for generalized Hamiltonian systems is obtained by applying the simultaneous approximation technique due to Lochak. Among these systems, dimensions of action variables and angle variables might be distinct.  相似文献   
88.
We use qualitative analysis and numerical simulation to study peaked traveling wave solutions of CH-γ and CH equations. General expressions of peakon and periodic cusp wave solutions are obtained. Some previous results become our special cases.  相似文献   
89.
一类含有P-Laplacian算子的奇异边值问题解的确切个数   总被引:2,自引:0,他引:2  
讨论了一类p-L ap lac ian算子型的奇异边值问题正解的确切个数以及解的性质.  相似文献   
90.
The anisotropic g-values of defects in hydrogenated microcrystalline silicon prepared by hot-wire chemical vapour deposition have been measured as a function of crystalline volume fraction at room temperature. The defect has been identified as a silicon-dangling bond existing on the surface of crystalline grain. Their anisotropic g-values are discussed in the light of theoretical calculations by Ishii et al. and Ishii and Shimizu. The defect density is also discussed as a function of crystalline volume fraction.  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