全文获取类型
收费全文 | 12299篇 |
免费 | 1394篇 |
国内免费 | 1201篇 |
专业分类
化学 | 4496篇 |
晶体学 | 120篇 |
力学 | 1474篇 |
综合类 | 191篇 |
数学 | 5856篇 |
物理学 | 2757篇 |
出版年
2024年 | 14篇 |
2023年 | 106篇 |
2022年 | 193篇 |
2021年 | 256篇 |
2020年 | 355篇 |
2019年 | 380篇 |
2018年 | 378篇 |
2017年 | 434篇 |
2016年 | 456篇 |
2015年 | 408篇 |
2014年 | 598篇 |
2013年 | 1184篇 |
2012年 | 623篇 |
2011年 | 731篇 |
2010年 | 604篇 |
2009年 | 671篇 |
2008年 | 718篇 |
2007年 | 719篇 |
2006年 | 655篇 |
2005年 | 611篇 |
2004年 | 514篇 |
2003年 | 526篇 |
2002年 | 507篇 |
2001年 | 441篇 |
2000年 | 424篇 |
1999年 | 363篇 |
1998年 | 359篇 |
1997年 | 292篇 |
1996年 | 219篇 |
1995年 | 162篇 |
1994年 | 136篇 |
1993年 | 113篇 |
1992年 | 92篇 |
1991年 | 97篇 |
1990年 | 75篇 |
1989年 | 56篇 |
1988年 | 48篇 |
1987年 | 46篇 |
1986年 | 33篇 |
1985年 | 54篇 |
1984年 | 40篇 |
1983年 | 21篇 |
1982年 | 39篇 |
1981年 | 25篇 |
1980年 | 23篇 |
1979年 | 23篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
报道了KDP晶体中的三倍频产生的实验研究,计算了比较了直接三倍频过程和级联过程对KDP晶体三阶有效非线性系数的贡献,并探讨了KDP作为非线性晶体材料三阶非线性系数测量基准的可行性。 相似文献
62.
Two Convergence Problems for Monotone Sequences 总被引:1,自引:0,他引:1
Eight measures of rate of convergence of monotone sequences of real numbers have been proposed and discussed in a paper by Beyer, Ebanks, and Qualls (Acta Appl. Math. 20 (1990), 267–284). These rates arose in discussions of dynamical systems. In the comparisons of these rates, two problems remained. A complete answer is given to one of the problems and a partial answer is given to the other problem. 相似文献
63.
具有奇异值分解性质的代数 总被引:4,自引:0,他引:4
设F为一个域,R为一个带有对合的F-代数,如果R上每一个矩阵都有奇异值分解(简称SVD),则称R为一个有SVD性质的F-代数.本文指出:R为一个有SVD性质的F-代数的充要条件是:R同构于R~+,或R~+上二次扩域,或R~+上四元数体((-1,-1)/R~+),其中R~+为R的对称元集合,并且R~+为一个Galois序闭域. 相似文献
64.
Recently, Fishbum and Lavalle (1995) and Lefèvre and Utev (1996) have considered some stochastic order relations specific for arithmetic random variables. The present work is concerned with these orderings, together with two other classes of stochastic order relations closely related. First, attention is paid to characterizations and various properties of all these orderings. Then, sufficient conditions of crossing-type for the two new classes of orderings are derived and extrema among discrete random variables are deduced. This is applied in actuarial sciences to obtain new bounds for the classical single life premiums as well as for the probability of ruin in the compound binomial risk model. 相似文献
65.
The application of some recently proposed algebraic multilevel methods for the solution of two-dimensional finite element problems on nonuniform meshes is studied. The locally refined meshes are created by the newest vertex mesh refinement method. After the introduction of this refinement technique it is shown that, by combining levels of refinement, a preconditioner of optimal order can be constructed for the case of local refinement along a line. Its relative condition number is accurately estimated. Numerical tests demonstrating the performance of the proposed preconditioners will be reported in a forthcoming paper. 相似文献
66.
James V. Crivello 《Journal of polymer science. Part A, Polymer chemistry》2007,45(18):4331-4340
The irradiation of hybrid photopolymer systems consisting of a free radically polymerizable multifunctional acrylate monomer and a cationically polymerizable epoxide or oxetane monomer was conducted under conditions where only the free radical polymerization takes place. This results in the formation of a free‐standing polyacrylate network film containing quiescent oxonium ions along with the unreacted cyclic ether monomer. The subsequent application of a point source of heat to the film ignites a cationic ring‐opening frontal polymerization that emanates from that site and propagates to all portions of the irradiated sample. This article examines the impact of various molecular structural and experimental parameters on these novel hybrid frontal polymerizations that produce interpenetrating network polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4331–4340, 2007 相似文献
67.
The aim of this paper is to present construction of finite element multiscaling function with three coefficients. In order to illuminate the result, two examples are given finally. 相似文献
68.
Hong-Nian Li Xiao-Xiong WangWang-Feng Ding 《Journal of Electron Spectroscopy and Related Phenomena》2006
Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C60 film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K3C60, K6C60, Ba4C60, Sm2.75C60 and Sm6C60 are calculated to help the quantitative analyses of the photoemission spectra for these compounds. 相似文献
69.
Roderich Tumulka 《Foundations of Physics》2007,37(2):186-197
In a recent paper Conway and Kochen, Found. Phys. 36, 2006, claim to have established that theories of the Ghirardi-Rimini-Weber
(RW) type, i.e., of spontaneous wave function collapse, cannot be made relativistic. On the other hand, relativistic GRW-type
theories have already been presented, in my recent paper, J. Stat. Phys. 125, 2006, and by Dowker and Henson, J. Stat. Phys.
115, 2004. Here, I elucidate why these are not excluded by the arguments of Conway and Kochen.
相似文献
70.
等腰三角形Mindlin板的自由振动分析 总被引:2,自引:0,他引:2
提出了一种新方法来对基于 Mindlin剪切变形理论的等腰三角形板进行自由振动分析 .此方法采用了一种新的基函数并利用 pb-2 Rayleigh-Ritz边界函数得到了一种新型的 Ritz方法 .这种方法的有效性通过收敛性和对比性分析得到了证实 .数值结果表明此方法相当精确有效 . 相似文献