全文获取类型
收费全文 | 310篇 |
免费 | 22篇 |
国内免费 | 29篇 |
专业分类
化学 | 32篇 |
晶体学 | 2篇 |
力学 | 52篇 |
综合类 | 3篇 |
数学 | 201篇 |
物理学 | 71篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 18篇 |
2012年 | 16篇 |
2011年 | 15篇 |
2010年 | 10篇 |
2009年 | 25篇 |
2008年 | 20篇 |
2007年 | 21篇 |
2006年 | 23篇 |
2005年 | 23篇 |
2004年 | 11篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 15 毫秒
71.
The paper describes a new method for the calculation of the Sommerfeld screening parameter σ1. It requires neither the knowledge of the energy separations of spin doublet levels nor is it based on the application of
the Hertz law. The only data required for the calculation are the experimental energy values of the level concerned for the
series of elements belonging to the same subshell in which the element in the question is situated. As an illustration the
values of σ1 are calculated for the L
1, L
2 and L
3 levels for elements belonging to the 4f subshell and these are found to be in excellent agreement with those published earlier by Gokhale and Misra. The method brings
out the constancy of σ1 (L
2
L
3)−σ1(L
1) in a natural way and may thus be regarded as providing theoretical explanation of the Hertz law. 相似文献
72.
73.
Denote by W(A) the numerical range of a bounded linear operator A. For two operators A and B (which may act on different Hilbert spaces), we study the relation between the inclusion relation W(A)⊆W(B) and the condition that A can be dilated to an operator of the form B⊗I. We also investigate the possibilities of dilating an operator A to operators with simple structure under the assumption that W(A) is included in a special region. 相似文献
74.
基于变分原理的二维热传导方程差分格式 总被引:5,自引:3,他引:2
研究二维热传导方程的差分数值模拟.用变分原理在不规则结构网格上建立热流通量形式的差分格式.将热流通量作为未知函数求泛函极值,并与温度函数联立求解.克服通常九点格式用插值方法计算网格边界上的热传导系数和网格结点上的温度所引入的误差. 相似文献
75.
哪一个钟慢了?--关于相对论中钟慢效应的进一步讨论 总被引:6,自引:0,他引:6
通过例子阐明狭义相对论中钟慢效应是相互的道理。 相似文献
76.
热传导方程的一类无网格方法 总被引:1,自引:0,他引:1
构造求解热传导方程的一类无网格方法,只要选择好每个节点的适当的邻点集合,便可利用节点信息顺利进行计算.作为特殊情形,也可在各种结构或非结构网格上进行计算.在矩形或均匀平行四边形网格上进行计算时具有二阶精度,当在任意的不规则四边形或三角形网格上计算时仍然是守恒的和相容的,且至少具有一阶精度.作为数值试验,将该方法用于在不规则四边形网格上及四边形与三角形混合网格上求解二维非线性抛物型方程,并在不规则四边形网格上求解二维三温辐射热传导方程,均获得了较为理想的数值结果. 相似文献
77.
Sebastian Noelle. 《Mathematics of Computation》1996,65(215):1155-1163
Recently, Cockburn, Coquel and LeFloch proved convergence and error estimates for higher-order finite volume schemes. Their result is based on entropy inequalities which are derived under restrictive assumptions on either the flux function or the numerical fluxes. Moreover, they assume that the spatial grid satisfies a standard regularity assumption. Using instead entropy inequalities derived in previous work by Kröner, Noelle and Rokyta and a weaker condition on the grid, we can generalize and simplify the error estimates.
78.
Alfonso Bueno‐Orovio Víctor M. Prez‐García 《Numerical Methods for Partial Differential Equations》2006,22(2):435-448
The spectral smoothed boundary method (SSBM) is a recently proposed numerical method to approximate the solution of partial differential equations in irregular domains with no‐flux boundary conditions by means of Fourier spectral methods. In this article we explore the robustness and accuracy of the scheme under variations of the artificial boundary conditions that must be imposed on the boundary of the enlarged domain in which the problem is solved. As a test model, we present quantitative numerical results based on a problem of propagation of waves of electrical activity in cardiac tissue for which the method is relevant. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
79.
The collinear atom-diatom collision system provides one of the simplest instances of chaotic or irregular scattering. Classically,
irregular scattering is manifest in the sensitive dependence of post-collision variables on initial conditions, and quantally,
in the appearance of a dense spectrum of dynamical resonances. We examine the influence of kinematic factors on such dynamical
resonances in collinear (He, H
2
+
) collisions by computing the transition state spectra for collinear (He, HD+) and (He, DH+) collisions using the time-dependent quantum mechanical approach. The nearest neighbor spacing distributionP(s) and the spectral rigidity Δ3(L) for these resonances suggest that the dynamics is predominantlyirregular for collinear (He, HD+) and predominantlyregular for collinear (He, DH+). These findings are reinforced by a significantly larger “correlation hole” in ensemble averaged survival probability ≪P(t)≫ values for collinear (He, HD+) than for collinear (He,DH+). In addition we have also examined measures of classical chaos through the dependence of the final vibrational action,n
f, on the initial vibrational phaseφ
i of the diatom, and Poincaré surfaces-of-section. They show that (He, HD+) collisions are partly chaotic over the entire energy range (0–2.78 eV) while (He, DH+) collisions, in contrast, are highly regular at collision energies below the classical threshold for reaction. Above the
threshold, the scattering remains regular for initial vibrational statesv=0 and 1 of DH+. 相似文献
80.
Fluctuation properties of the regular and irregular energy levels for the Hénon-Heiles Hamiltonian are examined. The spacing
distributions and the calculated values of the Δ3-statistic show that there is no difference in the short range correlation properties of these spectra. Remarkably, the Δ3 values agree with the results of random matrix theory.
on leave of absence from P.R.L., Ahmedabad 相似文献