全文获取类型
收费全文 | 3811篇 |
免费 | 115篇 |
国内免费 | 20篇 |
专业分类
化学 | 2483篇 |
晶体学 | 14篇 |
力学 | 80篇 |
数学 | 637篇 |
物理学 | 732篇 |
出版年
2024年 | 4篇 |
2023年 | 34篇 |
2022年 | 119篇 |
2021年 | 119篇 |
2020年 | 103篇 |
2019年 | 85篇 |
2018年 | 92篇 |
2017年 | 90篇 |
2016年 | 149篇 |
2015年 | 120篇 |
2014年 | 143篇 |
2013年 | 285篇 |
2012年 | 284篇 |
2011年 | 295篇 |
2010年 | 198篇 |
2009年 | 167篇 |
2008年 | 233篇 |
2007年 | 234篇 |
2006年 | 213篇 |
2005年 | 145篇 |
2004年 | 141篇 |
2003年 | 101篇 |
2002年 | 98篇 |
2001年 | 51篇 |
2000年 | 29篇 |
1999年 | 55篇 |
1998年 | 30篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 34篇 |
1994年 | 22篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 3篇 |
排序方式: 共有3946条查询结果,搜索用时 0 毫秒
1.
W. A. Rodrigues Jr. Q. A. G. de Souza J. Vaz Jr. P. Lounesto 《International Journal of Theoretical Physics》1996,35(9):1849-1900
In this paper we study Dirac-Hestenes spinor fields (DHSF) on a four-dimensional Riemann-Cartan spacetime (RCST). We prove that these fields must be defined as certain equivalence classes of even sections of the Clifford bundle (over the RCST), thereby being certain particular sections of a new bundle named the spin-Clifford bundle (SCB). The conditions for the existence of the SCB are studied and are shown to be equivalent to Geroch's theorem concerning the existence of spinor structures in a Lorentzian spacetime. We introduce also the covariant and algebraic Dirac spinor fields and compare these with DHSF, showing that all three kinds of spinor fields contain the same mathematical and physical information. We clarify also the notion of (Crumeyrolle's) amorphous spinors (Dirac-Kähler spinor fields are of this type), showing that they cannot be used to describe fermionic fields. We develop a rigorous theory for the covariant derivatives of Clifford fields (sections of the Clifford bundle, CB) and of Dirac-Hestenes spinor fields. We show how to generalize the original Dirac-Hestenes equation in Minkowski spacetime for the case of RCST. Our results are obtained from a variational principle formulated through the multiform derivative approach to Lagrangian field theory in the Clifford bundle. 相似文献
2.
María G. Armentano Ricardo G. Durn 《Numerical Methods for Partial Differential Equations》2003,19(5):653-664
In this article we analyze the effect of mass‐lumping in the linear triangular finite element approximation of second‐order elliptic eigenvalue problems. We prove that the eigenvalue obtained by using mass‐lumping is always below the one obtained with exact integration. For singular eigenfunctions, as those arising in non convex polygons, we prove that the eigenvalue obtained with mass‐lumping is above the exact eigenvalue when the mesh size is small enough. So, we conclude that the use of mass‐lumping is convenient in the singular case. When the eigenfunction is smooth several numerical experiments suggest that the eigenvalue computed with mass‐lumping is below the exact one if the mesh is not too coarse. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 653–664, 2003 相似文献
3.
How Focusing Phenomena in the Instructional Environment Support Individual Students' Generalizations
This article sets forth a way of connecting the classroom instructional environment with individual students' generalizations. To do so, we advance the notion of focusing phenomena, that is, regularities in the ways in which teachers, students, artifacts, and curricular materials act together to direct attention toward certain mathematical properties over others. The construct of focusing phenomena emerged from an empirical study conducted during a 5-week unit on slope and linear functions in a high school classroom using a reform curriculum. Qualitative evidence from interviews with 7 students revealed that students interpreted the m value in y = b + mx as a difference rather than a ratio as a result of counterproductive generalization afforded by focusing phenomena. Classroom analysis revealed 4 focusing phenomena, which regularly directed students' attention to various sets of differences rather than to the coordination of quantities. 相似文献
4.
5.
The open mapping and closed range theorems 总被引:1,自引:0,他引:1
6.
7.
8.
9.
José-francisco Rodrigues 《manuscripta mathematica》1984,46(1-3):65-82
The homogenization of the dam problem is discussed in the general weak formulation by means of the technique of correctors. In the two special cases of horizontal layers and of the isotropic coefficients with separated variables the problem is solved. However, in general, the unsaturated region is not stable for the homogenization, as a counterexample by Alt shows. 相似文献
10.
Ricardo Mañé 《Inventiones Mathematicae》1978,46(2):147-152