全文获取类型
收费全文 | 18366篇 |
免费 | 1822篇 |
国内免费 | 1407篇 |
专业分类
化学 | 3440篇 |
晶体学 | 88篇 |
力学 | 6334篇 |
综合类 | 236篇 |
数学 | 7880篇 |
物理学 | 3617篇 |
出版年
2024年 | 35篇 |
2023年 | 177篇 |
2022年 | 271篇 |
2021年 | 326篇 |
2020年 | 478篇 |
2019年 | 382篇 |
2018年 | 410篇 |
2017年 | 558篇 |
2016年 | 590篇 |
2015年 | 484篇 |
2014年 | 874篇 |
2013年 | 1337篇 |
2012年 | 831篇 |
2011年 | 995篇 |
2010年 | 836篇 |
2009年 | 1003篇 |
2008年 | 988篇 |
2007年 | 1056篇 |
2006年 | 985篇 |
2005年 | 953篇 |
2004年 | 864篇 |
2003年 | 865篇 |
2002年 | 770篇 |
2001年 | 697篇 |
2000年 | 650篇 |
1999年 | 668篇 |
1998年 | 590篇 |
1997年 | 511篇 |
1996年 | 395篇 |
1995年 | 376篇 |
1994年 | 284篇 |
1993年 | 201篇 |
1992年 | 239篇 |
1991年 | 194篇 |
1990年 | 163篇 |
1989年 | 95篇 |
1988年 | 67篇 |
1987年 | 66篇 |
1986年 | 51篇 |
1985年 | 57篇 |
1984年 | 50篇 |
1983年 | 32篇 |
1982年 | 34篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 440 毫秒
61.
62.
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
63.
We have used x-ray fluorescence analysis to study the elemental composition of gunshot residues from smooth-bore and rifled-bore
guns. We have established that it is possible to differentiate between types of projectiles (jacketed/lead), types of primers
(corrosive/noncorrosive), and types of propellant powders (black/smokeless) by analysis of the elemental composition of the
gunshot residues. We have shown that the mercury content in gunshot residues on the surface of the object carrying the residues
steadily decreases as storage time increases. Despite this fact, mercury can be preserved as a component of gunshot residues
on the object (cotton cloth) under room conditions for more than 45 days.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 320–325, May–June, 2006. 相似文献
64.
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
65.
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
66.
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
67.
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
68.
利用有效液滴模型计算了偶偶超重核的α衰变半衰期,计算过程中采用了保持碎片体积守恒的不对称形状描述以及有效惯性系数计算Gamow势垒穿透因子.首先在质子数Z为88—98的区域检验了有效液滴模型,发现计算结果与实验符合得比较好.随后将此模型推广到Z≥100的情况,虽然只用了两个模型参数,计算结果与实验数据符合,说明有效液滴模型是计算偶偶超重核素α衰变半衰期的一个成功模型. 相似文献
69.
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
70.
Boniface Nkemzi 《Mathematical Methods in the Applied Sciences》2006,29(9):1053-1080
This paper is concerned with the structure of the singular and regular parts of the solution of time‐harmonic Maxwell's equations in polygonal plane domains and their effective numerical treatment. The asymptotic behaviour of the solution near corner points of the domain is studied by means of discrete Fourier transformation and it is proved that the solution of the boundary value problem does not belong locally to H2 when the boundary of the domain has non‐acute angles. A splitting of the solution into a regular part belonging to the space H2, and an explicitly described singular part is presented. For the numerical treatment of the boundary value problem, we propose a finite element discretization which combines local mesh grading and the singular field methods and derive a priori error estimates that show optimal convergence as known for the classical finite element method for problems with regular solutions. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献