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   30273篇
  免费   130篇
  国内免费   279篇
化学   11438篇
晶体学   268篇
力学   1409篇
综合类   12篇
数学   9148篇
物理学   8407篇
  2021年   47篇
  2020年   61篇
  2019年   37篇
  2018年   1215篇
  2017年   1463篇
  2016年   764篇
  2015年   594篇
  2014年   511篇
  2013年   731篇
  2012年   3222篇
  2011年   2391篇
  2010年   1879篇
  2009年   1597篇
  2008年   646篇
  2007年   682篇
  2006年   688篇
  2005年   4502篇
  2004年   3971篇
  2003年   2349篇
  2002年   536篇
  2001年   326篇
  2000年   125篇
  1999年   189篇
  1998年   123篇
  1997年   91篇
  1996年   69篇
  1995年   56篇
  1994年   59篇
  1993年   43篇
  1992年   188篇
  1991年   157篇
  1990年   146篇
  1989年   120篇
  1988年   106篇
  1987年   65篇
  1986年   54篇
  1985年   47篇
  1984年   36篇
  1983年   37篇
  1979年   36篇
  1976年   80篇
  1975年   39篇
  1974年   42篇
  1973年   51篇
  1972年   40篇
  1970年   34篇
  1969年   37篇
  1968年   35篇
  1967年   30篇
  1966年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
S. D. Campos 《中国物理C(英文版)》2020,44(10):103103-103103-10
This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, in contrast, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross-section. From these results, some simple parameterization is introduced to fit the experimental data for the proton-proton and antiproton-proton total cross-section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the \begin{document}$ \rho(s)$\end{document} -parameter as well as to the elastic slope \begin{document}$ B(s)$\end{document} at high energies.  相似文献   
3.
4.
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards.  相似文献   
5.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported.  相似文献   
6.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling sequence. The work has been partially supported by the Swiss National Science Foundation.  相似文献   
7.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K.  相似文献   
8.
9.
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality.  相似文献   
10.
We consider the one-dimensional steady-state semiconductor deviceequations modelling a pnpn device. There are two relevant scalingsof the equations corresponding to small and large applied voltages.In both scalings, the semiconductor equations can be consideredas singularly perturbed. It turns out that the small-voltagescaling breaks down for current values between two saturationcurrents. In that interval, the large-voltage scaling has tobe employed. For both scalings, we derive the first-order termsof an asymptotic expansion and show that the reduced problemhas a solution. An example verifies that the current-voltagecurves obtained have the expected qualitative structure.  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