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   26005篇
  免费   4019篇
  国内免费   2781篇
化学   18507篇
晶体学   307篇
力学   1564篇
综合类   247篇
数学   2711篇
物理学   9469篇
  2025年   10篇
  2024年   258篇
  2023年   586篇
  2022年   849篇
  2021年   1026篇
  2020年   1144篇
  2019年   1116篇
  2018年   794篇
  2017年   744篇
  2016年   1211篇
  2015年   1164篇
  2014年   1368篇
  2013年   1778篇
  2012年   2217篇
  2011年   2209篇
  2010年   1542篇
  2009年   1357篇
  2008年   1551篇
  2007年   1514篇
  2006年   1368篇
  2005年   1198篇
  2004年   898篇
  2003年   814篇
  2002年   854篇
  2001年   677篇
  2000年   541篇
  1999年   583篇
  1998年   439篇
  1997年   415篇
  1996年   354篇
  1995年   334篇
  1994年   346篇
  1993年   256篇
  1992年   213篇
  1991年   227篇
  1990年   201篇
  1989年   130篇
  1988年   103篇
  1987年   110篇
  1986年   74篇
  1985年   56篇
  1984年   53篇
  1983年   26篇
  1982年   34篇
  1981年   24篇
  1980年   21篇
  1979年   3篇
  1977年   3篇
  1975年   3篇
  1957年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Let ∑, Г be two n-by-n diagonal matrices with σi,γi as their diagonals. For the inverse eigenvalue problem: look for y∈Rn such that Г + yyT is similar to ∑, we prove thatu also the sufficient condition for the solvability of this inverse problem. Its solution (set) is given explicitly. In some case, the problem is unstable. But we prove that the sums of the square of some contigious components keep stable, i.e., small sum keeps small, large sum has a small relative perturbation, see Theorem 3.  相似文献   
962.
Summary We characterize the ordinary generating functions of the Genocchi and median Genocchi numbers as unique solutions of some functional equations and give a direct algebraic proof of several continued fraction expansions for these functions. New relations between these numbers are also obtained.  相似文献   
963.
Integrable systems of NLS type in 2+1 dimensions are studied in three ways: their special solutions by Lie point symmetries, breaking-solutions by the ISM, as well as the non-isospectral problems.Department of Mathematics, Statistics and Computing Science, University of New England, Armidale N.S.W. 2351, Australia. E-mail: zhuhan@neumann.une.edu.au, xhe@metz.une.edu.au Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 99, No. 3, pp. 382–389, June, 1994.  相似文献   
964.
On the Global Stability of Cooperative Systems   总被引:7,自引:0,他引:7  
Suppose that F is a C1 cooperative vector field on X, whereX = Rn or Int , or [[p, q]].We prove that the unique equilibrium of F is globally asymptoticallystable if and only if every forward semi-orbit has compact closurein X.  相似文献   
965.
ln this paper, a new transformation is found out to straighten the interface Γ_2 x = f(y), f ∈ C^{2+a}([0, a]), f_y|_y =0, δ < f < l-δ,δ > 0,δ,l=constants and a perturbation of the interface is considered for a two dimensional diffraction problem. And the existence, uniqueness and regularity of an appeoximating Muskat model are proved.  相似文献   
966.
The present paper improves a result of Gutev [V. Gutev, Approaching points by continuous selections, J. Math. Soc. Japan (4) (2006) 1203–1210] by characterizing the countably-approachable points in sense of [V. Gutev, Approaching points by continuous selections, J. Math. Soc. Japan (4) (2006) 1203–1210] by a natural extreme-like condition in the spirit of [V. Gutev, T. Nogura, Vietoris continuous selections and disconnectedness-like properties, Proc. Amer. Math. Soc. 129 (2001) 2809–2815; V. Gutev, T. Nogura, Selection pointwise-maximal spaces, Topology Appl. 146–147 (2005) 397–408]. This demonstrates the natural relationship between different extreme-like points with respect to continuous selections for the Vietoris hyperspace of nonempty closed subsets.  相似文献   
967.
方舒 《数学研究》2010,43(1):55-66
给出二重非齐次马氏链的强遍历性,绝对平均强遍历性,Cesaro平均收敛的概念.利用二维马氏链的遍历性和C-K方程,建立了二维马氏链与二重非齐次马氏链遍历性的关系.并讨论了齐次二重马氏链绝对平均强遍历与强遍历的等价性.最后给出Cesaro平均收敛在马氏决策过程和信息论中应用.  相似文献   
968.
This paper deals with the existence and multiplicity of positive solutions to second order period boundary value problems with impulse effects. The proof of our main results relies on a well-known fixed point theorem in cones. The paper extends some previous results and reports some new results about impulsive differential equations.  相似文献   
969.
In this paper, the boundedness of mulitilinear commutator [b,T] on Herz-type space is considered, where T is a standard Calderón-Zygmund singular operator and b ∈ (BMO(Rn))m.  相似文献   
970.
Jiang and Tanner (2008) consider a method of classification using the Gibbs posterior which is directly constructed from the empirical classification errors. They propose an algorithm to sample from the Gibbs posterior which utilizes a smoothed approximation of the empirical classification error, via a Gibbs sampler with augmented latent variables. In this paper, we note some drawbacks of this algorithm and propose an alternative method for sampling from the Gibbs posterior, based on the Metropolis algorithm. The numerical performance of the algorithms is examined and compared via simulated data. We find that the Metropolis algorithm produces good classification results at an improved speed of computation.  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