全文获取类型
收费全文 | 10106篇 |
免费 | 806篇 |
国内免费 | 961篇 |
专业分类
化学 | 638篇 |
晶体学 | 6篇 |
力学 | 468篇 |
综合类 | 142篇 |
数学 | 5373篇 |
物理学 | 1840篇 |
综合类 | 3406篇 |
出版年
2024年 | 5篇 |
2023年 | 74篇 |
2022年 | 98篇 |
2021年 | 107篇 |
2020年 | 159篇 |
2019年 | 182篇 |
2018年 | 161篇 |
2017年 | 203篇 |
2016年 | 236篇 |
2015年 | 204篇 |
2014年 | 362篇 |
2013年 | 656篇 |
2012年 | 476篇 |
2011年 | 553篇 |
2010年 | 488篇 |
2009年 | 606篇 |
2008年 | 626篇 |
2007年 | 712篇 |
2006年 | 687篇 |
2005年 | 572篇 |
2004年 | 498篇 |
2003年 | 450篇 |
2002年 | 452篇 |
2001年 | 391篇 |
2000年 | 364篇 |
1999年 | 347篇 |
1998年 | 293篇 |
1997年 | 269篇 |
1996年 | 232篇 |
1995年 | 180篇 |
1994年 | 174篇 |
1993年 | 168篇 |
1992年 | 140篇 |
1991年 | 117篇 |
1990年 | 100篇 |
1989年 | 83篇 |
1988年 | 93篇 |
1987年 | 55篇 |
1986年 | 37篇 |
1985年 | 43篇 |
1984年 | 40篇 |
1983年 | 18篇 |
1982年 | 34篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 25篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Let Top
0
be the category of topological T
0-spaces, QU
0
the category of quasi-uniform T
0-spaces, T : QU
0
→ Top
0
the usual forgetful functor and K : QU
0
→ QU
0
the bicompletion reflector with unit k : 1 → K. Any T-section F : Top
0
→ QU
0
is called K-true if KF = FTKF, and upper (lower)
K-true if KF is finer (coarser) than FTKF. The literature considers important T-sections F that enjoy all three, or just one, or none of these properties. It is known that T(K,k)F is well-pointed if and only if F is upper K-true. We prove the surprising fact that T(K,k)F is the reflection to Fix(TkF) whenever it is idempotent. We also prove a new characterization of upper K-trueness. We construct examples to set apart some natural cases. In particular we present an upper K-true F for which T(K,k)F is not idempotent, and a K-true F for which the coarsest associated T-preserving coreflector in QU
0
is not stable under K.
We dedicate this paper to the memory of Sérgio de Ornelas Salbany (1941–2005). 相似文献
92.
Markus Hegland Jochen Garcke Vivien Challis 《Linear algebra and its applications》2007,420(2-3):249-275
The combination technique has repeatedly been shown to be an effective tool for the approximation with sparse grid spaces. Little is known about the reasons of this effectiveness and in some cases the combination technique can even break down. It is known, however, that the combination technique produces an exact result in the case of a projection into a sparse grid space if the involved partial projections commute.
The performance of the combination technique is analysed using a projection framework and the C/S decomposition. Error bounds are given in terms of angles between the spanning subspaces or the projections onto these subspaces. Based on this analysis modified combination coefficients are derived which are optimal in a certain sense and which can substantially extend the applicability and performance of the combination technique. 相似文献
93.
Numerical analysis for stochastic age-dependent population equations with Poisson jumps 总被引:1,自引:0,他引:1
In this paper, stochastic age-dependent population equations with Poisson jumps are considered. In general, most of stochastic age-dependent population equations with jumps do not have explicit solutions, thus numerical approximation schemes are invaluable tools for exploring their properties. The main purpose of this paper is to develop a numerical Euler scheme and show the convergence of the numerical approximation solution to the true solution. 相似文献
94.
Lai-Jiu Lin 《Journal of Global Optimization》2007,38(1):21-39
In this paper, we study an existence theorem of systems of generalized quasivariational inclusions problem. By this result,
we establish the existence theorems of solutions of systems of generalized equations, systems of generalized vector quasiequilibrium
problem, collective variational fixed point, systems of generalized quasiloose saddle point, systems of minimax theorem, mathematical
program with systems of variational inclusions constraints, mathematical program with systems of equilibrium constraints and
systems of bilevel problem and semi-infinite problem with systems of equilibrium problem constraints.
This research was supported by the National Science Council of the Republic of China. 相似文献
95.
设Λ={λn}n∞=1为正的实数数列,且当n→∞时,有λn↘0.本文给出了当λn≤Mn-1/2,n=1,2,…,(其中M>0为一正常数)时Müntz系统{xλn}的有理函数在Lp[0,1]空间的逼近速度,主要结论为Rn(f,Λ) Lp≤CMω(f,n-1/2)Lp,1≤p≤∞. 相似文献
96.
Andreas Rößler 《BIT Numerical Mathematics》2006,46(1):97-110
A general class of stochastic Runge–Kutta methods for Itô stochastic differential equation systems w.r.t. a one-dimensional Wiener process is introduced. The colored rooted tree analysis is applied to derive conditions for the coefficients of the stochastic Runge–Kutta method assuring convergence in the weak sense with a prescribed order. Some coefficients for new stochastic Runge–Kutta schemes of order two are calculated explicitly and a simulation study reveals their good performance. 相似文献
97.
In the present paper, we study the rate of convergence in simultaneous approximation for the Bézier variant of the Baskakov-Beta operators by using the decomposition technique of functions of bounded variation. 相似文献
98.
Xin Tao YE Chong LI 《数学学报(英文版)》2007,23(1):65-76
The BCQ and the Abadie CQ for infinite systems of convex inequalities in Banach spaces are characterized in terms of the upper semi-continuity of the convex cones generated by the subdifferentials of active convex functions. Some relationships with other constraint qualifications such as the CPLV and the Slate condition are also studied. Applications in best approximation theory are provided. 相似文献
99.
Two different problems are proposed as approximations of the usual system modelling natural convection under the Oberbeck-Boussinesq assumptions. The error is evaluated by means of the norm of its gradient in the Hilbert space. The average Nusselt number is also estimated. 相似文献
100.
Andreas Rößler 《BIT Numerical Mathematics》2007,47(3):657-680
The weak approximation of the solution of a system of Stratonovich stochastic differential equations with a m–dimensional Wiener process is studied. Therefore, a new class of stochastic Runge–Kutta methods is introduced. As the main
novelty, the number of stages does not depend on the dimension m of the driving Wiener process which reduces the computational effort significantly. The colored rooted tree analysis due
to the author is applied to determine order conditions for the new stochastic Runge–Kutta methods assuring convergence with
order two in the weak sense. Further, some coefficients for second order stochastic Runge–Kutta schemes are calculated explicitly.
AMS subject classification (2000) 65C30, 65L06, 60H35, 60H10 相似文献