全文获取类型
收费全文 | 35606篇 |
免费 | 4707篇 |
国内免费 | 2216篇 |
专业分类
化学 | 2864篇 |
晶体学 | 160篇 |
力学 | 5175篇 |
综合类 | 433篇 |
数学 | 22677篇 |
物理学 | 11220篇 |
出版年
2024年 | 75篇 |
2023年 | 325篇 |
2022年 | 452篇 |
2021年 | 558篇 |
2020年 | 1031篇 |
2019年 | 976篇 |
2018年 | 917篇 |
2017年 | 944篇 |
2016年 | 1065篇 |
2015年 | 837篇 |
2014年 | 1536篇 |
2013年 | 2972篇 |
2012年 | 1715篇 |
2011年 | 2024篇 |
2010年 | 1953篇 |
2009年 | 2157篇 |
2008年 | 2280篇 |
2007年 | 2306篇 |
2006年 | 2016篇 |
2005年 | 2043篇 |
2004年 | 1709篇 |
2003年 | 1698篇 |
2002年 | 1457篇 |
2001年 | 1201篇 |
2000年 | 1137篇 |
1999年 | 1076篇 |
1998年 | 949篇 |
1997年 | 832篇 |
1996年 | 615篇 |
1995年 | 521篇 |
1994年 | 433篇 |
1993年 | 340篇 |
1992年 | 288篇 |
1991年 | 291篇 |
1990年 | 245篇 |
1989年 | 138篇 |
1988年 | 155篇 |
1987年 | 141篇 |
1986年 | 136篇 |
1985年 | 145篇 |
1984年 | 128篇 |
1983年 | 64篇 |
1982年 | 112篇 |
1981年 | 106篇 |
1980年 | 74篇 |
1979年 | 85篇 |
1978年 | 71篇 |
1977年 | 56篇 |
1976年 | 42篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
271.
272.
Durand William A.Pham Ngoc Dinh 《Journal of Mathematical Analysis and Applications》2003,282(1):95-106
An electromagnetic diffraction problem in a wedge shaped region is reduced to a system of coupled functional difference equations by means of Sommerfeld integrals and Malyuzhinets theorem. By introducing an integral operator it is shown that the solutions of this system of functional equations can be defined in terms of integral representations whose kernels are solutions of a singular integral equation of Cauchy-Carleman type for which an explicit solution is given. 相似文献
273.
In this paper, authors investigate the order of growth and the hyper order of solutions of a class of the higher order linear differential equation, and improve results of M. Ozawa^[6], G. Gundersen^[7] and J.K. Langley^[8], Li Chun-hong^[11]. 相似文献
274.
Zhiyue Zhang Dingwen Deng 《Numerical Methods for Partial Differential Equations》2007,23(6):1530-1559
A modified backward difference time discretization is presented for Galerkin approximations for nonlinear hyperbolic equation in two space variables. This procedure uses a local approximation of the coefficients based on patches of finite elements with these procedures, a multidimensional problem can be solved as a series of one‐dimensional problems. Optimal order H01 and L2 error estimates are derived. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
275.
文章建立一个随机内生增长模型来阐明主要政策参数对经济增长与社会福利的影响.若对生产函数、效用函数、偏好及随机干扰作一些特殊的假设,我们证明了主要政策参数的均衡值能被模型参数唯一决定.进一步我们还得到了期望增长率与储蓄的清晰解.文章的最后,我们证明了政府支出直接影响个体决策者的决策:即提高经济增长率将减少福利;反之,增加福利将减少增长率. 相似文献
276.
Alexander G. Ramm Alexandra B. Smirnova Angelo Favini 《Annali di Matematica Pura ed Applicata》2003,182(1):37-52
A nonlinear operator equation F(x)=0, F:H→H, in a Hilbert space is considered. Continuous Newton’s-type procedures based on a construction of a dynamical system with
the trajectory starting at some initial point x
0 and becoming asymptotically close to a solution of F(x)=0 as t→+∞ are discussed. Well-posed and ill-posed problems are investigated.
Received: June 29, 2001; in final form: February 26, 2002?Published online: February 20, 2003
This paper was finished when AGR was visiting Institute for Theoretical Physics, University of Giessen. The author thanks
DAAD for support 相似文献
277.
Jonatan Lenells 《Journal of Mathematical Analysis and Applications》2007,325(2):1468-1478
We use the inverse scattering transform to show that a solution of the Camassa-Holm equation is identically zero whenever it vanishes on two horizontal half-lines in the x-t space. In particular, a solution that has compact support at two different times vanishes everywhere, proving that the Camassa-Holm equation has infinite propagation speed. 相似文献
278.
New solitons and kink solutions for the Gardner equation 总被引:3,自引:1,他引:2
The Gardner equation, also called combined KdV–mKdV equation, is studied. New hyperbolic ansatze are proposed to derive solitons solutions. The tanh method is used as well to obtain kink solutions. 相似文献
279.
章志飞 《浙江大学学报(理学版)》2003,30(6):609-611
利用Besov空间的热核刻画及压缩映射原理,研究半线性热方程ut-△u=u|u|a的初值问题,得到了当初值u0∈Lp0(Rn)且||u0||(B·)p-n (1/p0-1/p),∞(Rn)(p0=na/2,p>p0)充分小时,整体解的存在性及在一定条件下解的惟一性. 相似文献
280.
A general framework is developed to treat inverse problems with parameters that are random fields. It involves a sampling
method that exploits the sensitivity derivatives of the control variable with respect to the random parameters. As the sensitivity
derivatives are computed only at the mean values of the relevant parameters, the related extra cost of the present method
is a fraction of the total cost of the Monte Carlo method. The effectiveness of the method is demonstrated on an example problem
governed by the Burgers equation with random viscosity. It is specifically shown that this method is two orders of magnitude
more efficient compared to the conventional Monte Carlo method. In other words, for a given number of samples, the present
method yields two orders of magnitude higher accuracy than its conventional counterpart. 相似文献