全文获取类型
收费全文 | 7269篇 |
免费 | 483篇 |
国内免费 | 845篇 |
专业分类
化学 | 153篇 |
力学 | 246篇 |
综合类 | 105篇 |
数学 | 6683篇 |
物理学 | 1410篇 |
出版年
2024年 | 7篇 |
2023年 | 67篇 |
2022年 | 78篇 |
2021年 | 123篇 |
2020年 | 137篇 |
2019年 | 204篇 |
2018年 | 206篇 |
2017年 | 225篇 |
2016年 | 200篇 |
2015年 | 154篇 |
2014年 | 259篇 |
2013年 | 1196篇 |
2012年 | 228篇 |
2011年 | 314篇 |
2010年 | 296篇 |
2009年 | 414篇 |
2008年 | 508篇 |
2007年 | 474篇 |
2006年 | 437篇 |
2005年 | 382篇 |
2004年 | 370篇 |
2003年 | 373篇 |
2002年 | 355篇 |
2001年 | 248篇 |
2000年 | 260篇 |
1999年 | 192篇 |
1998年 | 204篇 |
1997年 | 205篇 |
1996年 | 108篇 |
1995年 | 74篇 |
1994年 | 53篇 |
1993年 | 47篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1936年 | 6篇 |
排序方式: 共有8597条查询结果,搜索用时 15 毫秒
51.
《Mathematische Nachrichten》2017,290(8-9):1381-1405
The aim of this article is to exhibit the variety of different Ricci soliton structures that a nilpotent Lie group can support when one allows for the metric tensor to be Lorentzian. In stark contrast to the Riemannian case, we show that a nilpotent Lie group can support a number of non‐isometric Lorentzian Ricci soliton structures with decidedly different qualitative behaviors and that Lorentzian Ricci solitons need not be algebraic Ricci solitons. The analysis is carried out by classifying all left invariant Lorentzian metrics on the connected, simply‐connected five‐dimensional Lie group having a Lie algebra with basis vectors and and non‐trivial bracket relations and , investigating the various curvature properties of the resulting families of metrics, and classifying all Lorentzian Ricci soliton structures. 相似文献
52.
《Mathematische Nachrichten》2017,290(14-15):2341-2355
In this paper, we use the powerful tool Milnor bases to determine all the locally symmetric left invariant Riemannian metrics up to automorphism, on 3‐dimensional connected and simply connected Lie groups, by solving system of polynomial equations of constants structure of each Lie algebra . Moreover, we show that E 0(2) is the only 3‐dimensional Lie group with locally symmetric left invariant Riemannian metrics which are not symmetric. 相似文献
53.
In this paper, the parakähler Hom-Lie algebras or phase space of Hom-Lie algebras in terms of Hom-left-symmetric algebras are studied. A structure theory of parakähler Hom-Lie algebras in terms of matched pairs of Hom-Lie algebras is also presented. Besides, the bimodules of Hom-left-symmetric algebras are investigated. Furthermore, Hom-left-symmetric bialgebra which is precisely equivalent to parakähler Hom-Lie algebra is introduced. Especially, the coboundary Hom-left-symmetric bialgebra is considered. 相似文献
54.
55.
Lisun Zheng 《代数通讯》2017,45(6):2417-2434
56.
David A. Towers 《代数通讯》2017,45(3):1284-1293
The purpose of this paper is to continue the study of chief factors of a Lie algebra and to prove a further strengthening of the Jordan–Hölder theorem for chief series. 相似文献
57.
We will characterize all finite dimensional Lie algebras with at most |F|2+|F|+2 centralizers, where F is the underlying field of Lie algebras under consideration. 相似文献
58.
We consider the canonical descending and ascending central series of ideals of an associative algebra. In particular, we prove that some ideal in the descending central series is finite-dimensional if and only if some ideal in the ascending central series is finite-codimensional. This result is the associative algebra analogue of results due to Reinhold Baer and Philip Hall in group theory and Ian Stewart in Lie algebra. We also prove various related results. 相似文献
59.
Rasoul Ahangari Maleki 《代数通讯》2017,45(2):514-520
60.