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   50246篇
  免费   2045篇
  国内免费   43篇
化学   32578篇
晶体学   250篇
力学   1612篇
综合类   3篇
数学   7713篇
物理学   10178篇
  2023年   387篇
  2022年   318篇
  2021年   528篇
  2020年   710篇
  2019年   683篇
  2018年   1036篇
  2017年   846篇
  2016年   1585篇
  2015年   1427篇
  2014年   1446篇
  2013年   3012篇
  2012年   3456篇
  2011年   3535篇
  2010年   2136篇
  2009年   1760篇
  2008年   3028篇
  2007年   3042篇
  2006年   2668篇
  2005年   2596篇
  2004年   2248篇
  2003年   1823篇
  2002年   1602篇
  2001年   945篇
  2000年   794篇
  1999年   574篇
  1998年   443篇
  1997年   398篇
  1996年   492篇
  1995年   317篇
  1994年   373篇
  1993年   375篇
  1992年   395篇
  1991年   352篇
  1990年   326篇
  1989年   323篇
  1988年   263篇
  1987年   261篇
  1986年   230篇
  1985年   390篇
  1984年   348篇
  1983年   241篇
  1982年   334篇
  1981年   320篇
  1980年   286篇
  1979年   273篇
  1978年   254篇
  1976年   277篇
  1975年   250篇
  1974年   261篇
  1973年   239篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C 1 transformation.  相似文献   
85.
This Note introduces a new integral form of the charge and current deposition scheme given in 1992 by Villasenor and Buneman, which permits the conservation of charge in PIC codes. This integral form extends directly to higher order spline shape factors, whose use produces less numerical noise. We thus get a discrete charge conserving method for high order shape factors. This method extends easily to nonuniform Cartesian grids for first order shape factors. To cite this article: R. Barthelmé, C. R. Acad. Sci. Paris, Ser. I 341 (2005).  相似文献   
86.
 A simple and direct spectrofluorimetric method has been developed for the determination of aluminum using alizarin red PS (1,2,4-trihydroxy 9,10-anthraquinone-3-sulfonic acid). The method is based on the strong fluorescence (480/564 nm) of Al3+ and alizarin red. Experimental parameters such as pH, concentration of the ligand, ionic strength of the solution, reaction time and temperature were optimized in order to maximize the analytical signal. Interferences of several ions (anions and cations) were studied and evaluated. The linear range of the method extends from 3 to 100 μg L−1. Limit of detection (3sb) was 0.9 μg L−1. The method was tested with a silicate certified reference material. Interferences were eliminated by a liquid extraction with cupferron. Author for correspondence. E-mail: aucelior@rdc.puc-rio.br Received September 10, 2002; accepted January 15, 2003 Published online May 5, 2003  相似文献   
87.
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented.  相似文献   
88.
 This paper generalizes results of F. K?rner from [4] where she established the existence of maximal automorphisms (i.e. automorphisms moving all non-algebraic elements). An ω-maximal automorphism is an automorphism whose powers are maximal automorphisms. We prove that any structure has an elementary extension with an ω-maximal automorphism. We also show the existence of ω-maximal automorphisms in all countable arithmetically saturated structures. Further we describe the pairs of tuples (ˉab) for which there is an ω-maximal automorphism mapping ˉa to ˉb. Received: 12 December 2001 / Published online: 10 October 2002 Supported by the ``Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture' Mathematics Subject Classification (2000): Primary: 03C50; Secondary: 03C57 Key words or phrases: Automorphism – Recursively saturated structure  相似文献   
89.
Various physical systems of dispersive waves admit solutions in the form of generalized solitary waves. Such waves result from the resonance between a long localized wave and short periodic oscillations. Many estimates (rigorous and numerical) have been given for the amplitude of the ripples in the tail of the generalized solitary wave when its central part has a sech2 shape. This Note provides estimates (not yet rigorous) for the ripple amplitude when the central part is flat and wide. To cite this article: C. Fochesato, F. Dias, C. R. Acad. Sci. Paris, Ser. I 337 (2003).  相似文献   
90.
Recent mass measurements of proton-rich nuclei close to the N=Z line were used for the calculation of the interaction strength δV pn between valence protons and neutrons. When compared with δV pn values calculated from mass values of the AME’95 mass tables, the breaking down of the SU(4) symmetry is verified at Z=32,33,34.  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