全文获取类型
收费全文 | 15241篇 |
免费 | 1600篇 |
国内免费 | 1564篇 |
专业分类
化学 | 2105篇 |
晶体学 | 34篇 |
力学 | 847篇 |
综合类 | 255篇 |
数学 | 12209篇 |
物理学 | 2955篇 |
出版年
2024年 | 27篇 |
2023年 | 183篇 |
2022年 | 170篇 |
2021年 | 280篇 |
2020年 | 335篇 |
2019年 | 386篇 |
2018年 | 396篇 |
2017年 | 453篇 |
2016年 | 516篇 |
2015年 | 377篇 |
2014年 | 669篇 |
2013年 | 1203篇 |
2012年 | 710篇 |
2011年 | 768篇 |
2010年 | 712篇 |
2009年 | 908篇 |
2008年 | 987篇 |
2007年 | 1048篇 |
2006年 | 940篇 |
2005年 | 882篇 |
2004年 | 740篇 |
2003年 | 662篇 |
2002年 | 702篇 |
2001年 | 599篇 |
2000年 | 544篇 |
1999年 | 525篇 |
1998年 | 424篇 |
1997年 | 381篇 |
1996年 | 300篇 |
1995年 | 218篇 |
1994年 | 188篇 |
1993年 | 143篇 |
1992年 | 133篇 |
1991年 | 109篇 |
1990年 | 83篇 |
1989年 | 66篇 |
1988年 | 64篇 |
1987年 | 59篇 |
1986年 | 53篇 |
1985年 | 80篇 |
1984年 | 77篇 |
1983年 | 29篇 |
1982年 | 54篇 |
1981年 | 31篇 |
1980年 | 42篇 |
1979年 | 39篇 |
1978年 | 26篇 |
1977年 | 24篇 |
1976年 | 18篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
We propose to reduce the (spectral) condition number of a given linear system by adding a suitable diagonal matrix to the system matrix, in particular by shifting its spectrum. Iterative procedures are then adopted to recover the solution of the original system. The case of real symmetric positive definite matrices is considered in particular, and several numerical examples are given. This approach has some close relations with Riley's method and with Tikhonov regularization. Moreover, we identify approximately the aforementioned procedure with a true action of preconditioning. 相似文献
4.
5.
《Indagationes Mathematicae》2021,32(1):55-85
We show that the differential structure of the orbit space of a proper action of a Lie group on a smooth manifold is weakly reflexive. This implies that the orbit space is a differentiable space in the sense of Smith, which ensures that the orbit space has an exterior algebra of differential forms, that satisfies Smith’s version of de Rham’s theorem. Because the orbit space is a locally closed subcartesian space, it has vector fields and their flows. 相似文献
6.
In the paper mentioned in the title, it is proved the boundedness of the Riesz potential operator of variable order α(x) from variable exponent Morrey space to variable exponent Campanato space, under certain assumptions on the variable exponents p(x) and λ(x) of the Morrey space. Assumptions on the exponents were different depending on whether takes or not the critical values 0 or 1. In this note, we improve those results by unifying all the cases and covering the whole range . We also provide a correction to some minor technicality in the proof of Theorem 2 in the aforementioned paper. 相似文献
7.
Dengfeng LI 《Frontiers of Mathematics in China》2022,17(4):501
This paper introduces an open conjecture in time-frequency analysis on the linear independence of a finite set of time-frequency shifts of a given L2 function. Firstly, background and motivation for the conjecture are provided. Secondly, the main progress of this linear independence in the past twenty five years is reviewed. Finally, the partial results of the high dimensional case and other cases for the conjecture are briefly presented. 相似文献
8.
10.