全文获取类型
收费全文 | 16710篇 |
免费 | 1964篇 |
国内免费 | 1454篇 |
专业分类
化学 | 551篇 |
晶体学 | 1篇 |
力学 | 1862篇 |
综合类 | 327篇 |
数学 | 14310篇 |
物理学 | 3077篇 |
出版年
2024年 | 23篇 |
2023年 | 205篇 |
2022年 | 171篇 |
2021年 | 279篇 |
2020年 | 519篇 |
2019年 | 494篇 |
2018年 | 511篇 |
2017年 | 603篇 |
2016年 | 582篇 |
2015年 | 409篇 |
2014年 | 816篇 |
2013年 | 1363篇 |
2012年 | 712篇 |
2011年 | 1033篇 |
2010年 | 791篇 |
2009年 | 984篇 |
2008年 | 1148篇 |
2007年 | 1038篇 |
2006年 | 992篇 |
2005年 | 913篇 |
2004年 | 788篇 |
2003年 | 756篇 |
2002年 | 726篇 |
2001年 | 534篇 |
2000年 | 542篇 |
1999年 | 489篇 |
1998年 | 449篇 |
1997年 | 419篇 |
1996年 | 280篇 |
1995年 | 251篇 |
1994年 | 195篇 |
1993年 | 159篇 |
1992年 | 118篇 |
1991年 | 85篇 |
1990年 | 95篇 |
1989年 | 58篇 |
1988年 | 51篇 |
1987年 | 51篇 |
1986年 | 53篇 |
1985年 | 45篇 |
1984年 | 58篇 |
1983年 | 24篇 |
1982年 | 59篇 |
1981年 | 43篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 39篇 |
1977年 | 30篇 |
1976年 | 15篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
有限长通电螺线管空间的磁场分布 总被引:2,自引:0,他引:2
本文计算了有限长通电螺线管空间的磁感应强度分布,给出了解析表达式,并绘出了它们的空间分布图。 相似文献
82.
Cyclic Hypomonotonicity,Cyclic Submonotonicity,and Integration 总被引:9,自引:1,他引:8
Rockafellar has shown that the subdifferentials of convex functions are always cyclically monotone operators. Moreover, maximal cyclically monotone operators are necessarily operators of this type, since one can construct explicitly a convex function, which turns out to be unique up to a constant, whose subdifferential gives back the operator. This result is a cornerstone in convex analysis and relates tightly convexity and monotonicity. In this paper, we establish analogous robust results that relate weak convexity notions to corresponding notions of weak monotonicity, provided one deals with locally Lipschitz functions and locally bounded operators. In particular, the subdifferentials of locally Lipschitz functions that are directionally hypomonotone [respectively, directionally submonotone] enjoy also an additional cyclic strengthening of this notion and in fact are maximal under this new property. Moreover, every maximal cyclically hypomonotone [respectively, maximal cyclically submonotone] operator is always the Clarke subdifferential of some directionally weakly convex [respectively, directionally approximately convex] locally Lipschitz function, unique up to a constant, which in finite dimentions is a lower C2 function [respectively, a lower C1 function]. 相似文献
83.
For vector quasivariational inequalities involving multifunctions in topological vector spaces, an existence result is obtained without a monotonicity assumption and with a convergence assumption weaker than semicontinuity. A new type of quasivariational inequality is proposed. Applications to quasicomplementarity problems and traffic network equilibria are considered. In particular, definitions of weak and strong Wardrop equilibria are introduced for the case of multivalued cost functions. 相似文献
84.
Claudia Garetto 《Acta Appl Math》2004,80(2):123-174
The aim of this work is to develop a global calculus for pseudo-differential operators acting on suitable algebras of generalized functions. In particular, a condition of global hypoellipticity of the symbols gives a result of regularity for the corresponding pseudo-differential equations. This calculus and this frame are proposed as tools for the study in Colombeau algebras of partial differential equations globally defined on R
n
. 相似文献
85.
Marko Nedeljkov 《Mathematical Methods in the Applied Sciences》2004,27(8):931-955
This work gives a condition for existence of singular and delta shock wave solutions to Riemann problem for 2×2 systems of conservation laws. For a fixed left‐hand side value of Riemann data, the condition obtained in the paper describes a set of possible right‐hand side values. The procedure is similar to the standard one of finding the Hugoniot locus. Fluxes of the considered systems are globally Lipschitz with respect to one of the dependent variables. The association in a Colombeau‐type algebra is used as a solution concept. Copyright © 2004 John Wiley &Sons, Ltd. 相似文献
86.
A model is developed for the flow of a slightly compressible fluid through a saturated inelastic porous medium. The initial‐boundary‐value problem is a system that consists of the diffusion equation for the fluid coupled to the momentum equation for the porous solid together with a constitutive law which includes a possibly hysteretic relation of elasto‐visco‐plastic type. The variational form of this problem in Hilbert space is a non‐linear evolution equation for which the existence and uniqueness of a global strong solution is proved by means of monotonicity methods. Various degenerate situations are permitted, such as incompressible fluid, negligible porosity, or a quasi‐static momentum equation. The essential sufficient conditions for the well‐posedness of the system consist of an ellipticity condition on the term for diffusion of fluid and either a viscous or a hardening assumption in the constitutive relation for the porous solid. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
87.
We present an O(min(Kn,n2)) algorithm to solve the maximum integral multiflow and minimum multicut problems in rooted trees, where K is the number of commodities and n is the number of vertices. These problems are NP-hard in undirected trees but polynomial in directed trees. In the algorithm we propose, we first use a greedy procedure to build the multiflow then we use duality properties to obtain the multicut and prove the optimality. 相似文献
88.
K. Kubilius 《Acta Appl Math》2003,78(1-3):233-242
We consider the integral equation driven by a standard Brownian motion and by a fractional Brownian motion. Sufficient conditions under which the equation has a weak solution are obtained. 相似文献
89.
两相同部件温贮备可修的人机系统解的性质分析 总被引:5,自引:1,他引:4
郭卫华 《数学的实践与认识》2003,33(7):88-95
本文首先用强连续算子半群理论证明了两相同部件温贮备可修的人机系统动态非负解的存在唯一性 ,然后证明了 0是系统主算子的本征值 ,并得到 0本征值对应的本征向量是正的 ,从而系统存在稳态正解 . 相似文献
90.
Zhao Fang BAI Jin Chuan HOU 《数学学报(英文版)》2005,21(5):1167-1182
Let X be a (real or complex) Banach space with dimension greater than 2 and let B0(X) be the subspace of B(X) spanned by all nilpotent operators on X. We get a complete classification of surjective additive maps Ф on B0(X) which preserve nilpotent operators in both directions. In particular, if X is infinite-dimensional, we prove that Ф has the form either Ф(T) = cATA^-1 or Ф(T) = cAT'A^-1, where A is an invertible bounded linear or conjugate linear operator, c is a scalar, T' denotes the adjoint of T. As an application of these results, we show that every additive surjective map on B(X) preserving spectral radius has a similar form to the above with |c| = 1. 相似文献