全文获取类型
收费全文 | 21352篇 |
免费 | 2495篇 |
国内免费 | 1535篇 |
专业分类
化学 | 4214篇 |
晶体学 | 71篇 |
力学 | 2292篇 |
综合类 | 399篇 |
数学 | 13044篇 |
物理学 | 5362篇 |
出版年
2024年 | 39篇 |
2023年 | 171篇 |
2022年 | 291篇 |
2021年 | 394篇 |
2020年 | 492篇 |
2019年 | 510篇 |
2018年 | 523篇 |
2017年 | 659篇 |
2016年 | 704篇 |
2015年 | 537篇 |
2014年 | 922篇 |
2013年 | 1550篇 |
2012年 | 984篇 |
2011年 | 1011篇 |
2010年 | 977篇 |
2009年 | 1166篇 |
2008年 | 1306篇 |
2007年 | 1357篇 |
2006年 | 1254篇 |
2005年 | 1198篇 |
2004年 | 981篇 |
2003年 | 888篇 |
2002年 | 1026篇 |
2001年 | 825篇 |
2000年 | 725篇 |
1999年 | 676篇 |
1998年 | 613篇 |
1997年 | 492篇 |
1996年 | 470篇 |
1995年 | 395篇 |
1994年 | 315篇 |
1993年 | 262篇 |
1992年 | 229篇 |
1991年 | 206篇 |
1990年 | 139篇 |
1989年 | 120篇 |
1988年 | 108篇 |
1987年 | 102篇 |
1986年 | 103篇 |
1985年 | 112篇 |
1984年 | 104篇 |
1983年 | 42篇 |
1982年 | 86篇 |
1981年 | 66篇 |
1980年 | 52篇 |
1979年 | 58篇 |
1978年 | 38篇 |
1977年 | 22篇 |
1976年 | 23篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
与传统时域有限差分算法相比,采用以伪谱方法离散Maxwell微分方程为基础的时域伪谱(PSTD)算法计算大的电尺度电磁场时域问题,将大大提高计算效率,降低内存需求。为了拓宽PSTD算法的应用,近年来,基于网格插值方法的非均匀时域伪谱算法得到了发展。研究的重点是算法中非均匀网格技术的实现及其在时域瞬态脉冲电磁场模拟和高功率超宽带脉冲技术方面的应用。以高斯脉冲为激励源,用该算法计算了多层介质的反射和透射,并通过超宽带脉冲穿墙实验对这一方法的应用进行了验证。模拟和实验结果具有较好的一致性。 相似文献
82.
Lahcne Mezrag 《Mathematische Nachrichten》2004,266(1):60-67
In [5], it is proved that a bounded linear operator u, from a Banach space Y into an Lp(S, ν) factors through Lp1 (S, ν) for some p1 > 1, if Y* is of finite cotype; (S, ν) is a probability space for p = 0, and any measure space for 0 < p < 1. In this paper, we generalize this result to uv, where u : Y → Lp(S, ν) and v : X → Y are linear operators such that v* is of finite Ka?in cotype. This result gives also a new proof of Grothendieck's theorem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
83.
The exponential functional of simple, symmetric random walks with negative
drift is an infinite polynomial Y = 1 + ξ1 + ξ1ξ2 + ξ1ξ2ξ3 + ⋯ of independent
and identically distributed non-negative random variables. It has moments that are
rational functions of the variables μ
k
= E(ξ
k
) < 1 with universal coefficients. It
turns out that such a coefficient is equal to the number of permutations with descent
set defined by the multiindex of the coefficient. A recursion enumerates all numbers
of permutations with given descent sets in the form of a Pascal-type triangle.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
84.
Siaw-Lynn Ng 《Order》2004,21(1):1-5
We present a characterisation of posets of size n with linear discrepancy n − 2. These are the posets that are “furthest” from a linear order without being an antichain.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
85.
We present a characterization of confluence for term rewriting systems, which is then refined for special classes of rewriting systems. The refined characterization is used to obtain a polynomial time algorithm for deciding the confluence of ground term rewrite systems. The same approach also shows the decidability of confluence for shallow and linear term rewriting systems. The decision procedure has a polynomial time complexity under the assumption that the maximum arity of a function symbol in the signature is a constant. 相似文献
86.
Toshihiro Kobayashi 《Mathematical Methods in the Applied Sciences》2004,27(1):79-89
This paper is concerned with global stabilization of an undamped non‐linear string in the case where any velocity feedback is not available. The linearized system has an infinite number of poles and zeros on the imaginary axis. In the case where any velocity feedback is not available, a parallel compensator is effective. The stabilizer is constructed for the augmented system which consists of the controlled system and a parallel compensator. It is proved that the string can be stabilized by linear boundary control. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
87.
88.
Larbi Berrahmoune 《Mathematical Methods in the Applied Sciences》2004,27(12):1385-1398
We consider an initial and boundary value problem for a homogenous string subject to an internal pointwise control. The solution resulting from a non‐linear feedback is studied. We give various explicit decay estimates depending on the control position and the feedback non‐linearity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
89.
In this article we prove the existence of the solution to the mixed problem for Euler–Bernoulli beam equation with memory term. The existence is proved by means of the Faedo–Galerkin method and the exponential decay is obtained by making use of the multiplier technique combined with integral inequalities due to Komornik. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
90.
A model is developed for the flow of a slightly compressible fluid through a saturated inelastic porous medium. The initial‐boundary‐value problem is a system that consists of the diffusion equation for the fluid coupled to the momentum equation for the porous solid together with a constitutive law which includes a possibly hysteretic relation of elasto‐visco‐plastic type. The variational form of this problem in Hilbert space is a non‐linear evolution equation for which the existence and uniqueness of a global strong solution is proved by means of monotonicity methods. Various degenerate situations are permitted, such as incompressible fluid, negligible porosity, or a quasi‐static momentum equation. The essential sufficient conditions for the well‐posedness of the system consist of an ellipticity condition on the term for diffusion of fluid and either a viscous or a hardening assumption in the constitutive relation for the porous solid. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献