全文获取类型
收费全文 | 10291篇 |
免费 | 1120篇 |
国内免费 | 653篇 |
专业分类
化学 | 235篇 |
晶体学 | 41篇 |
力学 | 4651篇 |
综合类 | 119篇 |
数学 | 5027篇 |
物理学 | 1991篇 |
出版年
2024年 | 12篇 |
2023年 | 113篇 |
2022年 | 146篇 |
2021年 | 175篇 |
2020年 | 289篇 |
2019年 | 244篇 |
2018年 | 269篇 |
2017年 | 308篇 |
2016年 | 369篇 |
2015年 | 275篇 |
2014年 | 421篇 |
2013年 | 775篇 |
2012年 | 466篇 |
2011年 | 563篇 |
2010年 | 484篇 |
2009年 | 569篇 |
2008年 | 543篇 |
2007年 | 591篇 |
2006年 | 557篇 |
2005年 | 571篇 |
2004年 | 497篇 |
2003年 | 480篇 |
2002年 | 442篇 |
2001年 | 405篇 |
2000年 | 365篇 |
1999年 | 358篇 |
1998年 | 333篇 |
1997年 | 265篇 |
1996年 | 217篇 |
1995年 | 169篇 |
1994年 | 132篇 |
1993年 | 98篇 |
1992年 | 112篇 |
1991年 | 103篇 |
1990年 | 74篇 |
1989年 | 45篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 34篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1973年 | 2篇 |
1959年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
42.
43.
B. M. Azizur Rahman A. K. M. Saiful Kabir Muttukrishnan Rajarajan Kenneth T. V. Grattan 《Optical and Quantum Electronics》2005,37(1-3):171-183
Modal solutions of planar photonic crystal waveguides with rectangular air-holes are presented by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, power confinements, modal hybridness, beat lengths and group velocity dispersions are shown for the fundamental and higher order modes of the quasi-TE and TM polarizations. 相似文献
44.
Chen Hao 《中国科学A辑(英文版)》2006,49(5):715-720
In this paper, for the the primes p such that 3 is a divisor of p − 1, we prove a result which reduces the computation of the linear complexity of a sequence over GF(p
m) (any positive integer m) with the period 3n (n and p
m − 1 are coprime) to the computation of the linear complexities of three sequences with the period n. Combined with some known algorithms such as generalized Games-Chan algorithm, Berlekamp-Massey algorithm and Xiao-Wei-Lam-Imamura
algorithm, we can determine the linear complexity of any sequence over GF(p
m) with the period 3n (n and p
m
− 1 are coprime) more efficiently. 相似文献
45.
Gabriel N. Gatica Ernst P. Stephan 《Numerical Methods for Partial Differential Equations》2002,18(1):105-128
This article deals with an expanded mixed finite element formulation, based on the Hu‐Washizu principle, for a nonlinear incompressible material in the plane. We follow our related previous works and introduce both the stress and the strain tensors as further unknowns, which yields a two‐fold saddle point operator equation as the corresponding variational formulation. A slight generalization of the classical Babu?ka‐Brezzi's theory is applied to prove unique solvability of the continuous and discrete formulations, and to derive the corresponding a priori error analysis. An extension of the well‐known PEERS space is used to define an stable associated Galerkin scheme. Finally, we provide an a posteriori error analysis based on the classical Bank‐Weiser approach. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 105–128, 2002 相似文献
46.
Mixed and hybrid finite element methods for the resolution of a wide range of linear and nonlinear boundary value problems (linear elasticity, Stokes problem, Navier–Stokes equations, Boussinesq equations, etc.) have known a great development in the last few years. These methods allow simultaneous computation of the original variable and its gradient, both of them being equally accurate. Moreover, they have local conservation properties (conservation of the mass and the momentum) as in the finite volume methods.The purpose of this paper is to give a review on some mixed finite elements developed recently for the resolution of Stokes and Navier–Stokes equations, and the linear elasticity problem. Further developments for a quasi-Newtonian flow obeying the power law are presented. 相似文献
47.
本文针对一类非饱和土壤水流问题,提出了基于二次插值的特征差分格式,得到了严谨的L2模误差估计.并作了数值试验,指明方法的有效性. 相似文献
48.
Masanobu Haraguchi David F. P. Pile Toshihiro Okamoto Masuo Fukui Dmitri K. Gramotnev 《Optical Review》2006,13(4):228-230
We have numerically shown the existence of coupled wedge plasmons (CWPs) which propagates along a nano gap of a twin metal
wedge. The CWPs are formed by wedge plasmons which can interact with each other. The dispersion relations of the wavenumber,
propagation distance, and beam area of CWPs, are described and show that the characteristics of CWPs are similar to those
of wedge plasmons and of gap plasmons. We also propose a new plasmon waveguide composed of twin metal wedges with a nano gap. 相似文献
49.
High even order generalizations of the traditional upwind method are introduced to solve second order ODE-BVPs without recasting
the problem as a first order system. Both theoretical analysis and numerical comparison with central difference schemes of
the same order show that these new methods may avoid typical oscillations and achieve high accuracy. Singular perturbation
problems are taken into account to emphasize the main features of the proposed methods.
AMS subject classification (2000) 65L10, 65L12, 65L50 相似文献
50.
光照和氮素对外来植物凤眼莲生长和生理特性的影响 总被引:1,自引:0,他引:1
通过研究不同光照和氮素营养处理的外来植物凤眼莲的生长、生物量分配、硝酸还原酶活性、游离氨基酸以及可溶性蛋白质含量变化,探讨其对环境适应性的生理学机制。凤眼莲表现出极强的可塑性,随光照和氮素营养的增加,凤眼莲生长速率明显加快,氮素代谢关键酶硝酸还原酶活性上升。根部吸收的硝酸根离子大部分运输到叶片中还原,氮素同化效率高。氨基酸含量和可溶性蛋白质含量呈现明显的变化,叶片可溶性蛋白质含量与根冠生物量分配显著相关。本研究表明风眼莲对光照和氮素表现出很强的适应性,其快速生长和高可塑性依赖于对环境变化的牛理响廊。 相似文献