全文获取类型
收费全文 | 127522篇 |
免费 | 7166篇 |
国内免费 | 13496篇 |
专业分类
化学 | 90564篇 |
晶体学 | 1351篇 |
力学 | 6108篇 |
综合类 | 1339篇 |
数学 | 21581篇 |
物理学 | 27241篇 |
出版年
2024年 | 141篇 |
2023年 | 967篇 |
2022年 | 2400篇 |
2021年 | 2769篇 |
2020年 | 3112篇 |
2019年 | 3039篇 |
2018年 | 2649篇 |
2017年 | 3702篇 |
2016年 | 4212篇 |
2015年 | 3389篇 |
2014年 | 4807篇 |
2013年 | 9335篇 |
2012年 | 8308篇 |
2011年 | 6860篇 |
2010年 | 5860篇 |
2009年 | 7960篇 |
2008年 | 8079篇 |
2007年 | 8531篇 |
2006年 | 7567篇 |
2005年 | 6483篇 |
2004年 | 6120篇 |
2003年 | 5071篇 |
2002年 | 5976篇 |
2001年 | 3704篇 |
2000年 | 3476篇 |
1999年 | 3248篇 |
1998年 | 2872篇 |
1997年 | 2361篇 |
1996年 | 2054篇 |
1995年 | 1950篇 |
1994年 | 1727篇 |
1993年 | 1430篇 |
1992年 | 1354篇 |
1991年 | 978篇 |
1990年 | 853篇 |
1989年 | 723篇 |
1988年 | 595篇 |
1987年 | 433篇 |
1986年 | 392篇 |
1985年 | 364篇 |
1984年 | 348篇 |
1983年 | 197篇 |
1982年 | 311篇 |
1981年 | 231篇 |
1980年 | 239篇 |
1979年 | 258篇 |
1978年 | 200篇 |
1977年 | 136篇 |
1976年 | 129篇 |
1973年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Masaaki Sugihara 《Numerische Mathematik》1997,75(3):379-395
Summary. In the light of the functional analysis theory we establish the optimality of the double exponential formula. The argument
consists of the following three ingredients: (1) introduction of a number of spaces of functions analytic in a strip region
about the real axis, each space being characterized by the decay rate of their elements (functions) in the neighborhood of
the infinity; (2) proof of the (near-) optimality of the trapezoidal formula in each space introduced in (1) by showing the
(near-) equality between an upper estimate for the error norm of the trapezoidal formula and a lower estimate for the minimum
error norm of quadratures; (3) nonexistence theorem for the spaces, the characterizing decay rate of which is more rapid than
the double exponential.
Received September 15, 1995 / Accepted December 14, 1995 相似文献
72.
We investigate congruence classes and direct congruence classes of m-tuples in the complex projective space ℂP
n
. For direct congruence one allows only isometries which are induced by linear (instead of semilinear) mappings. We establish
a canonical bijection between the set of direct congruence classes of m-tuples of points in ℂP
n
and the set of equivalence classes of positive semidefinite Hermitean m×m-matrices of rank at most n+1 with 1's on the diagonal. As a corollary we get that the direct congruence class of an m-tuple is uniquely determined by the direct congruence classes of all of its triangles, provided that no pair of points of
the m-tuple has distance π/2. Examples show that the situation changes drastically if one replaces direct congruence classes by
congruence classes or if distances π/2 are allowed. Finally we do the same
kind of investigation also for the complex hyperbolic space ℂH
n
. Most of the results are completely analogous, however, there are also some interesting differences.
Received: 15 January 1996 相似文献
73.
74.
Summary. We generalise and apply a refinement indicator of the type originally designed by Mackenzie, Süli and Warnecke in [15] and
[16] for linear Friedrichs systems to the Euler equations of inviscid, compressible fluid flow. The Euler equations are symmetrized
by means of entropy variables and locally linearized about a constant state to obtain a symmetric hyperbolic system to which
an a posteriori error analysis of the type introduced in [15] can be applied. We discuss the details of the implementation of the refinement
indicator into the DLR--Code which is based on a finite volume method of box type on an unstructured grid and present numerical results.
Received May 15, 1995 / Revised version received April 17, 1996 相似文献
75.
76.
77.
本文给出了C^n中子空间之间最大和最小主角在矩阵逼近,投影算子的扰动分析,群逆以及Oraxin逆的扰动估计,条件数理论,Bott-Duffin系统扰动分析中一些应用。 相似文献
78.
有势场逆问题的边界元法 总被引:5,自引:0,他引:5
本文给出了位势方程逆问题的一种最小二乘边界元解法。控制方程为Laplace方程,但一部分边界上未给出任何边值,而只在某些内点上给出了势函值。这一问题在数学上属不适定问题,但在一定条件下存在唯一解。本文同时给出了一种估计解的可靠性的方法。数值试验表明,这类逆问题采用边界元法是非常有效的。 相似文献
79.
80.
Summary. Let be a square matrix dependent on parameters and , of which we choose as the eigenvalue parameter. Many computational problems are equivalent to finding a point such that has a multiple eigenvalue at . An incomplete decomposition of a matrix dependent on several parameters is proposed. Based on the developed theory two new algorithms are
presented for computing multiple eigenvalues of with geometric multiplicity . A third algorithm is designed for the computation of multiple eigenvalues with geometric multiplicity but which also appears to have local quadratic convergence to semi-simple eigenvalues. Convergence analyses of these methods
are given. Several numerical examples are presented which illustrate the behaviour and applications of our methods.
Received December 19, 1994 / Revised version received January 18, 1996 相似文献