全文获取类型
收费全文 | 30619篇 |
免费 | 1210篇 |
国内免费 | 462篇 |
专业分类
化学 | 20060篇 |
晶体学 | 203篇 |
力学 | 838篇 |
综合类 | 30篇 |
数学 | 4659篇 |
物理学 | 6501篇 |
出版年
2023年 | 203篇 |
2022年 | 212篇 |
2021年 | 513篇 |
2020年 | 577篇 |
2019年 | 563篇 |
2018年 | 425篇 |
2017年 | 362篇 |
2016年 | 945篇 |
2015年 | 786篇 |
2014年 | 938篇 |
2013年 | 1676篇 |
2012年 | 1773篇 |
2011年 | 2064篇 |
2010年 | 1211篇 |
2009年 | 1111篇 |
2008年 | 1686篇 |
2007年 | 1664篇 |
2006年 | 1523篇 |
2005年 | 1445篇 |
2004年 | 1318篇 |
2003年 | 1100篇 |
2002年 | 1157篇 |
2001年 | 623篇 |
2000年 | 549篇 |
1999年 | 461篇 |
1998年 | 344篇 |
1997年 | 333篇 |
1996年 | 399篇 |
1995年 | 341篇 |
1994年 | 340篇 |
1993年 | 299篇 |
1992年 | 254篇 |
1991年 | 274篇 |
1990年 | 266篇 |
1989年 | 227篇 |
1988年 | 223篇 |
1987年 | 204篇 |
1986年 | 183篇 |
1985年 | 313篇 |
1984年 | 334篇 |
1983年 | 218篇 |
1982年 | 290篇 |
1981年 | 271篇 |
1980年 | 247篇 |
1979年 | 220篇 |
1978年 | 226篇 |
1977年 | 255篇 |
1976年 | 215篇 |
1975年 | 188篇 |
1973年 | 183篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
James K. Freericks Elliott H. Lieb Daniel Ueltschi 《Communications in Mathematical Physics》2002,227(2):243-279
The Falicov–Kimball model is a simple quantum lattice model that describes light and heavy electrons interacting with an
on-site repulsion; alternatively, it is a model of itinerant electrons and fixed nuclei. It can be seen as a simplification
of the Hubbard model; by neglecting the kinetic (hopping) energy of the spin up particles, one gets the Falicov–Kimball model.
We show that away from half-filling, i.e. if the sum of the densities of both kinds of particles differs from 1, the particles
segregate at zero temperature and for large enough repulsion. In the language of the Hubbard model, this means creating two
regions with a positive and a negative magnetization.
Our key mathematical results are lower and upper bounds for the sum of the lowest eigenvalues of the discrete Laplace operator
in an arbitrary domain, with Dirichlet boundary conditions. The lower bound consists of a bulk term, independent of the shape
of the domain, and of a term proportional to the boundary. Therefore, one lowers the kinetic energy of the itinerant particles
by choosing a domain with a small boundary. For the Falicov- Kimball model, this corresponds to having a single “compact”
domain that has no heavy particles.
Received: 21 June 2001 / Accepted: 4 January 2002 相似文献
34.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
35.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
36.
Let Ψ(x,y) (resp. Ψm(x,y)) denote the number of integers not exceeding x that are y-friable, i.e. have no prime factor exceeding y (resp. and are coprime to m). Evaluating the ratio Ψm(x/d,y)/Ψ(x,y) for 1≤slantd≤slantx, m≥slant 1, x≥slant y≥slant 2, turns out to be a crucial step for estimating arithmetic sums over friable integers. Here, it is crucial to obtain formulae with a very wide range of validity. In this paper, several uniform estimates are provided for the aforementioned ratio, which supersede all previously known results. Applications are given to averages of various arithmetic functions over friable integers which in turn improve corresponding results from the literature. The technique employed rests mainly on the saddle-point method, which is an efficient and specific tool for the required design.2000 Mathematics Subject Classification: Primary—11N25; Secondary—11K65, 11N37 相似文献
37.
We study the relation between the cohomology of general linear and symmetric groups and their respective quantizations, using Schur algebras and standard homological techniques to build appropriate spectral sequences. As our methods fit inside a much more general context within the theory of finite-dimensional algebras, we develop our results first in that general setting, and then specialize to the above situations. From this we obtain new proofs of several known results in modular representation theory of symmetric groups. Moreover, we reduce certain questions about computing extensions for symmetric groups and Hecke algebras to questions about extensions for general linear groups and their quantizations. 相似文献
38.
Journal d'Analyse Mathématique - 相似文献
39.
Michael De Castro 《Tetrahedron letters》2004,45(34):6501-6504
2-Deoxy-2-iodo-glycosylamides have been prepared from a variety of protected d-glucals by their reaction with N-iodosuccinimide and amides. Benzyl protected 2-iodoamides, when treated with sodium hydride and 15-crown-5, gave stable C1 N-linked 2-glycooxazolines as the major products. Silyl protected 2-iodoamides afforded the C1 O-linked 2-glycooxazolines; presumably by the rearrangement of unstable N-acylaziridine intermediates. 相似文献
40.
Reaction of acetylene dicarboxaldehyde monoacetal with substituted Meldrum’s acid leads good yields in 2-pyranones-4-carboxaldehydes substituted in position 3. 相似文献