全文获取类型
收费全文 | 96190篇 |
免费 | 13840篇 |
国内免费 | 4459篇 |
专业分类
化学 | 63057篇 |
晶体学 | 881篇 |
力学 | 5155篇 |
综合类 | 483篇 |
数学 | 30376篇 |
物理学 | 14537篇 |
出版年
2024年 | 81篇 |
2023年 | 344篇 |
2022年 | 488篇 |
2021年 | 781篇 |
2020年 | 1551篇 |
2019年 | 3241篇 |
2018年 | 3136篇 |
2017年 | 3544篇 |
2016年 | 3970篇 |
2015年 | 6084篇 |
2014年 | 6529篇 |
2013年 | 9840篇 |
2012年 | 7166篇 |
2011年 | 7065篇 |
2010年 | 6106篇 |
2009年 | 6107篇 |
2008年 | 6568篇 |
2007年 | 5897篇 |
2006年 | 5329篇 |
2005年 | 5149篇 |
2004年 | 4251篇 |
2003年 | 3948篇 |
2002年 | 4472篇 |
2001年 | 2677篇 |
2000年 | 2453篇 |
1999年 | 1628篇 |
1998年 | 982篇 |
1997年 | 817篇 |
1996年 | 649篇 |
1995年 | 531篇 |
1994年 | 443篇 |
1993年 | 307篇 |
1992年 | 289篇 |
1991年 | 293篇 |
1990年 | 243篇 |
1989年 | 154篇 |
1988年 | 144篇 |
1987年 | 146篇 |
1986年 | 138篇 |
1985年 | 146篇 |
1984年 | 142篇 |
1983年 | 65篇 |
1982年 | 122篇 |
1981年 | 95篇 |
1980年 | 72篇 |
1979年 | 80篇 |
1978年 | 48篇 |
1977年 | 45篇 |
1976年 | 34篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Qian-shun Chang Bo-ling GuoInstitute of Applied Mathematics Academy of Mathematics System Sciences Chinese Academy of Sciences Beijing ChinaInstitute of Applied Physics Computational Mathematics Beijing China 《应用数学学报(英文版)》2002,18(2):201-214
Abstract In this paper, a dissipative Zakharov equations are discretized by difference method.We make priorestimates for the algebric system of equations. It is proved that for each mesh size,there exist attractors forthe discretized system.The bounds of the Hausdorff dimensions of the discrete attractors are obtained,and thevarious bounds are dependent of the mesh sizes. 相似文献
62.
Olaf Hansen 《Mathematical Methods in the Applied Sciences》2002,25(12):1075-1090
In this article we study the radiosity operator along an edge between two adjacent half‐planes. First we show that the radiosity operator is invertible in a whole scale of anisotropic Sobolev spaces. In the absence of any shadows we are able to derive regularity properties of the solution, which depend only on the angle between the half‐planes, the reflectivity coefficients and the right‐hand side. This work can be considered as a supplement to the article of Rathsfeld (Mathematical Methods in the Applied Sciences 1999; 22 : 217–241). Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
63.
Claudio Simeone 《General Relativity and Gravitation》2002,34(11):1887-1893
A consistent quantization with a clear notion of time and evolution is given for the anisotropic Kantowski–Sachs cosmological model. It is shown that a suitable coordinate choice allows to obtain a solution of the Wheeler–DeWitt equation in the form of definite energy states, and that the results can be associated to two disjoint equivalent theories, one for each sheet of the constraint surface. 相似文献
64.
Let G=(V(G),E(G)) be a graph. A (n,G, λ)‐GD is a partition of the edges of λKn into subgraphs (G‐blocks), each of which is isomorphic to G. The (n,G,λ)‐GD is named as graph design for G or G‐decomposition. The large set of (n,G,λ)‐GD is denoted by (n,G,λ)‐LGD. In this work, we obtain the existence spectrum of (n,P3,λ)‐LGD. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 151–159, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10008 相似文献
65.
Milan Medved? 《Journal of Mathematical Analysis and Applications》2002,267(2):643-650
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality. 相似文献
66.
In this work we study nonnegativity and positivity of a discrete quadratic functional with separately varying endpoints. We introduce a notion of an interval coupled with 0, and hence, extend the notion of conjugate interval to 0 from the case of fixed to variable endpoint(s). We show that the nonnegativity of the discrete quadratic functional is equivalent to each of the following conditions: The nonexistence of intervals coupled with 0, the existence of a solution to Riccati matrix equation and its boundary conditions. Natural strengthening of each of these conditions yields a characterization of the positivity of the discrete quadratic functional. Since the quadratic functional under consideration could be a second variation of a discrete calculus of variations problem with varying endpoints, we apply our results to obtain necessary and sufficient optimality conditions for such problems. This paper generalizes our recent work in [R. Hilscher, V. Zeidan, Comput. Math. Appl., to appear], where the right endpoint is fixed. 相似文献
67.
It is long known that the Fokker-Planck equation with prescribed constant coefficients of diffusion and linear friction describes
the ensemble average of the stochastic evolutions in velocity space of a Brownian test particle immersed in a heat bath of
fixed temperature. Apparently, it is not so well known that the same partial differential equation, but now with constant
coefficients which are functionals of the solution itself rather than being prescribed, describes the kinetic evolution (in
the N→∞ limit) of an
isolated
N-particle system with certain stochastic interactions. Here we discuss in detail this recently discovered interpretation.
An erratum to this article can be found at 相似文献
68.
本文对具有有限时滞的泛函微分方程建立了关于依照两种测度的实际稳定性的Razumikhin型判定定理,其中未采用通常的辅助函数,且可运用多个含有状态变量x的部分变元的Lyapunov函数,得出部分变远实际稳定性的判定定理,从而改进了已有的结果。 相似文献
69.
In this paper necessary and sufficient conditions of null-controllability and approximate null-controllability are obtained for the wave equation on a half-axis. Controls solving these problems are found explicitly. Moreover, bang-bang controls solving the approximate null-controllability problem are constructed with the aid of solutions of a frequency extinguishing problem in the restricted band (−a,a) for this equation and the Markov power moment problem. 相似文献
70.
Several new families of c‐Bhaskar Rao designs with block size 4 are constructed. The necessary conditions for the existence of a c‐BRD (υ,4,λ) are that: (1)λmin=?λ/3 ≤ c ≤ λ and (2a) c≡λ (mod 2), if υ > 4 or (2b) c≡ λ (mod 4), if υ = 4 or (2c) c≠ λ ? 2, if υ = 5. It is proved that these conditions are necessary, and are sufficient for most pairs of c and λ; in particular, they are sufficient whenever λ?c ≠ 2 for c > 0 and whenever c ? λmin≠ 2 for c < 0. For c < 0, the necessary conditions are sufficient for υ> 101; for the classic Bhaskar Rao designs, i.e., c = 0, we show the necessary conditions are sufficient with the possible exception of 0‐BRD (υ,4,2)'s for υ≡ 4 (mod 6). © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 361–386, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10009 相似文献