全文获取类型
收费全文 | 20030篇 |
免费 | 3402篇 |
国内免费 | 1761篇 |
专业分类
化学 | 8256篇 |
晶体学 | 269篇 |
力学 | 2185篇 |
综合类 | 266篇 |
数学 | 6694篇 |
物理学 | 7523篇 |
出版年
2024年 | 43篇 |
2023年 | 186篇 |
2022年 | 456篇 |
2021年 | 502篇 |
2020年 | 741篇 |
2019年 | 729篇 |
2018年 | 705篇 |
2017年 | 810篇 |
2016年 | 931篇 |
2015年 | 815篇 |
2014年 | 1118篇 |
2013年 | 1902篇 |
2012年 | 1203篇 |
2011年 | 1279篇 |
2010年 | 1079篇 |
2009年 | 1142篇 |
2008年 | 1091篇 |
2007年 | 1136篇 |
2006年 | 1047篇 |
2005年 | 966篇 |
2004年 | 857篇 |
2003年 | 772篇 |
2002年 | 782篇 |
2001年 | 687篇 |
2000年 | 654篇 |
1999年 | 572篇 |
1998年 | 503篇 |
1997年 | 445篇 |
1996年 | 368篇 |
1995年 | 259篇 |
1994年 | 266篇 |
1993年 | 169篇 |
1992年 | 163篇 |
1991年 | 132篇 |
1990年 | 84篇 |
1989年 | 96篇 |
1988年 | 86篇 |
1987年 | 60篇 |
1986年 | 49篇 |
1985年 | 51篇 |
1984年 | 55篇 |
1983年 | 24篇 |
1982年 | 35篇 |
1981年 | 32篇 |
1980年 | 18篇 |
1979年 | 26篇 |
1978年 | 18篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
A method using third order moments for estimating the regression coefficients as well as the latent state scores of the reduced-rank regression model when the latent variable(s) are non-normally distributed is presented in this paper. It is shown that the factor analysis type indeterminacy of the regression coefficient matrices is eliminated. A real life example of the proposed method is presented. Differences of this solution with the reduced-rank regression eigen solution are discussed. 相似文献
3.
Taekyun Kim 《Journal of Mathematical Analysis and Applications》2002,273(1):236-242
The purpose of this paper is to give a proof of Kummer type congruence for the q-Bernoulli numbers of higher order, which is an answer to a part of the problem in a previous publication (see Indian J. Pure Appl. Math. 32 (2001) 1565-1570). 相似文献
4.
P. E. Cladis 《Journal of statistical physics》1991,62(5-6):899-925
We first discuss nonlinear aspects of phase transition theory applied to a particular liquid crystal phase transition. A simple derivation is given to show how two coupled Goldstone modes (one appearing as gauge fluctuations of the ordered phase) can force a phase transition, against all expectations, to take place discontinuously (theory of Halperin, Lubensky, and Ma)-but the discontinuity may be immeasurably small. Then, we describe a new dynamical test of phase transition order, developed by Cladiset al., that turns out to be more sensitive than x-ray diffraction and adiabatic calorimetry. Quantitative data found by this new method are in excellent agreement with the measurements of adiabatic calorimetry and x-ray diffraction as well as expectations implicit in the predictions of HLM.This is the text of an after-banquet talk given at the CNLS Workshop on the Dynamics of Concentrated Systems. 相似文献
5.
Josep Maria Izquierdo 《TOP》2006,14(2):375-398
The paper introduces a refinement of the notion of population monotonic allocation scheme, called regular population monotonic
allocation scheme (regularpmas). This refinement is based on economic situations in which players may have to select new partners from a set of potential
players and in which there exist certain capacity constraints. A sufficient condition for the existence of a regularpmas is given. For the class of games with regularpmas, we prove that the core coincides with the Davis and Maschler and the Mas-Colell bargaining sets. 相似文献
6.
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
7.
D. Yafaev 《Proceedings Mathematical Sciences》2002,112(1):245-255
We find an explicit function approximating at high energies the kernel of the scattering matrix with arbitrary accuracy. Moreover,
the same function gives all diagonal singularities of the kernel of the scattering matrix in the angular variables.
This paper is dedicated to Jean-Michel Combes on the occasion of his sixtieth birthday. 相似文献
8.
We establish a relation between stable distributions in probability theory and the fractional integral. Moreover, it turns out that the parameter of the stable distribution coincides with the exponent of the fractional integral. It follows from an analysis of the obtained results that equations with the fractional time derivative describe the evolution of some physical system whose time degree of freedom becomes stochastic, i.e., presents a sum of random time intervals subject to a stable probability distribution. We discuss relations between the fractal Cantor set (Cantor strips) and the fractional integral. We show that the possibility to use this relation as an approximation of the fractional integral is rather limited. 相似文献
9.
李永祥 《数学物理学报(A辑)》2003,23(2):245-252
该文讨论四阶常微分方程边值问题u^(4)(t)=f(t,u,u″), t∈[0,1],u(0)=u(1)=u″(0)=u″(1)=0解的存在性, 其中f(t,u,v):[0,1]×R×R→R为Carathéodory函数. 在不限制f关于u,v的增长阶, 不假定f关于u,v的单调性的一般情形下, 用上下解方法获得了解的存在性结果,并讨论了单调迭代求解的有效性. 相似文献
10.
建立了相变热力学理论和场论的关系. 强调在量子场论中必须引进序参量场, 则相变的讨论就类似于Goldstone bosons 的产生. 如果只讨论一级相变, Goldstone bosons场就足够了; 如果要讨论二级相变, 则必须讨论一系列的场, 这些场构成一个对称群的表示. 另外, 也将这一思想用到色超导中. In this paper we built a relation between the thermodynamical theory of the phase transition and field theory. We emphasized that in the quantum field theory we have to introduce the order parameter fields. Then the discussion of the phase transition is closed to the creation of the Goldstone bosons. If we only discuss the first order transition, the Goldstone bosons fields are sufficient. If we want to discuss the second order transition, we have to discuss a set of fields that constructs a representation of a symmetry group. We also apply this concept to color superconductivity. 相似文献