全文获取类型
收费全文 | 28323篇 |
免费 | 3403篇 |
国内免费 | 1794篇 |
专业分类
化学 | 1798篇 |
晶体学 | 18篇 |
力学 | 3177篇 |
综合类 | 318篇 |
数学 | 19699篇 |
物理学 | 8510篇 |
出版年
2024年 | 64篇 |
2023年 | 298篇 |
2022年 | 336篇 |
2021年 | 459篇 |
2020年 | 874篇 |
2019年 | 867篇 |
2018年 | 794篇 |
2017年 | 734篇 |
2016年 | 829篇 |
2015年 | 698篇 |
2014年 | 1296篇 |
2013年 | 2518篇 |
2012年 | 1324篇 |
2011年 | 1675篇 |
2010年 | 1646篇 |
2009年 | 1796篇 |
2008年 | 1888篇 |
2007年 | 1854篇 |
2006年 | 1583篇 |
2005年 | 1568篇 |
2004年 | 1309篇 |
2003年 | 1263篇 |
2002年 | 1119篇 |
2001年 | 828篇 |
2000年 | 804篇 |
1999年 | 765篇 |
1998年 | 722篇 |
1997年 | 586篇 |
1996年 | 452篇 |
1995年 | 378篇 |
1994年 | 319篇 |
1993年 | 207篇 |
1992年 | 195篇 |
1991年 | 210篇 |
1990年 | 178篇 |
1989年 | 103篇 |
1988年 | 106篇 |
1987年 | 103篇 |
1986年 | 99篇 |
1985年 | 101篇 |
1984年 | 88篇 |
1983年 | 44篇 |
1982年 | 86篇 |
1981年 | 75篇 |
1980年 | 54篇 |
1979年 | 56篇 |
1978年 | 39篇 |
1977年 | 31篇 |
1976年 | 24篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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
12.
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
13.
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
14.
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
15.
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
16.
An implicit quasi-monotone second-order accurate method is proposed for analyzing the spiral Couette flow of a rarefied gas between coaxial cylinders. The basic advantages of the method over the conventional method of stationry iterations are that the former is conservative with respect to the collision integral, has a simple software implementation for any types of boundary conditions, and applies to a wide range of Knudsen numbers. 相似文献
17.
Soliton interaction under the influence of higher-order effects 总被引:6,自引:0,他引:6
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically. 相似文献
18.
19.
This paper undertakes a systematic treatment of the low regularity local wellposedness and ill-posedness theory in Hs andHs for semilinear wave equations with polynomial nonlinearity in u and (e)u. This ill-posed result concerns the focusing type equations with nonlinearity on u and (e)tu. 相似文献
20.