全文获取类型
收费全文 | 7926篇 |
免费 | 273篇 |
国内免费 | 54篇 |
专业分类
化学 | 5492篇 |
晶体学 | 45篇 |
力学 | 209篇 |
数学 | 1337篇 |
物理学 | 1170篇 |
出版年
2023年 | 58篇 |
2022年 | 73篇 |
2021年 | 121篇 |
2020年 | 156篇 |
2019年 | 142篇 |
2018年 | 95篇 |
2017年 | 76篇 |
2016年 | 201篇 |
2015年 | 187篇 |
2014年 | 223篇 |
2013年 | 414篇 |
2012年 | 448篇 |
2011年 | 503篇 |
2010年 | 334篇 |
2009年 | 265篇 |
2008年 | 474篇 |
2007年 | 454篇 |
2006年 | 464篇 |
2005年 | 434篇 |
2004年 | 343篇 |
2003年 | 298篇 |
2002年 | 314篇 |
2001年 | 120篇 |
2000年 | 100篇 |
1999年 | 107篇 |
1998年 | 101篇 |
1997年 | 97篇 |
1996年 | 96篇 |
1995年 | 72篇 |
1994年 | 68篇 |
1993年 | 58篇 |
1992年 | 48篇 |
1991年 | 64篇 |
1990年 | 48篇 |
1989年 | 68篇 |
1988年 | 47篇 |
1986年 | 40篇 |
1985年 | 69篇 |
1984年 | 77篇 |
1983年 | 63篇 |
1982年 | 81篇 |
1981年 | 75篇 |
1980年 | 56篇 |
1979年 | 44篇 |
1978年 | 71篇 |
1977年 | 50篇 |
1976年 | 63篇 |
1975年 | 46篇 |
1974年 | 52篇 |
1973年 | 41篇 |
排序方式: 共有8253条查询结果,搜索用时 15 毫秒
1.
Clifford Henry Taubes 《Communications in Mathematical Physics》1989,122(3):455-526
A proof is given of Witten's conjectures for the rigidity of the index of the Dirac-Ramond operator on the loop space of a spin manifold which admits anS
1 symmetry.Research supported in part by the National Science Foundation 相似文献
2.
Henry P. McKean 《纯数学与应用数学通讯》2003,56(5):638-680
3.
The values of the Higgs mass are obtained for two possibilities of extending the standard model in a way compatible with the existence of a noncommutative structure at high energies. We assume the existence of a big desert between the low energy electroweak scale and the high energy scale Λ=1.1×1017 GeV, where noncommutative features become relevant. We conclude that it is extremely difficult to depart from the Higgs mass value obtained from noncommutative geometry for the standard model with three generations only. 相似文献
4.
5.
A Variable Neighborhood Search for the Multi Depot Vehicle Routing Problem with Time Windows 总被引:6,自引:0,他引:6
Michael Polacek Richard F. Hartl Karl Doerner Marc Reimann 《Journal of Heuristics》2004,10(6):613-627
The aim of this paper is to propose an algorithm based on the philosophy of the Variable Neighborhood Search (VNS) to solve Multi Depot Vehicle Routing Problems with Time Windows. The paper has two main contributions. First, from a technical point of view, it presents the first application of a VNS for this problem and several design issues of VNS algorithms are discussed. Second, from a problem oriented point of view the computational results show that the approach is competitive with an existing Tabu Search algorithm with respect to both solution quality and computation times. 相似文献
6.
On the exact distribution of linear combinations of order statistics from dependent random variables 总被引:2,自引:0,他引:2
We study the exact distribution of linear combinations of order statistics of arbitrary (absolutely continuous) dependent random variables. In particular, we examine the case where the random variables have a joint elliptically contoured distribution and the case where the random variables are exchangeable. We investigate also the particular L-statistics that simply yield a set of order statistics, and study their joint distribution. We present the application of our results to genetic selection problems, design of cellular phone receivers, and visual acuity. We give illustrative examples based on the multivariate normal and multivariate Student t distributions. 相似文献
7.
We study the chiral behavior of the nucleon and Δ-isobar masses within a manifestly covariant chiral effective-field theory, consistent with the analyticity principle. We compute the πN and πΔ one-loop contributions to the mass and field-normalization constant, and find that they can be described in terms of universal relativistic loop functions, multiplied by appropriate spin, isospin and coupling constants. We show that these manifestly relativistic one-loop corrections, when properly renormalized, obey the chiral power-counting and vanish in the chiral limit. The results including only the πN-loop corrections compare favorably with the lattice QCD data for the pion-mass dependence of the nucleon and Δ masses, while inclusion of the πΔ loops tends to spoil this agreement. 相似文献
8.
Justina Grabowska Karuna Kar Nanda R.T. Rajendra Kumar J.P. Mosnier M.O. Henry Simon B. Newcomb Patrick McNally Lisa OReilly Xu Lu Enda McGlynn 《Superlattices and Microstructures》2007,42(1-6):327
Self-organized ZnAl2O4 nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl2O4, formed by the reaction of Zn and O with the sapphire substrate. 相似文献
9.
In this paper the performance of a fiber-optic LAN with spread spectrum multiplexing is discussed from the viewpoint of transmission parameters. Two architectures are considered. The first concerns a structure with cascade-connected Y-type fiber-optic couplers. The second concerns an architecture with cascade-connected active optoelectronic repeater-coupler (ORCA) devices. 相似文献
10.
Summary A hypermedia environment was designed to set up a collection of reference data, reference spectra and computational tools. The system may serve as an aid for the combined interpretation of molecular spectra. This paper describes the context dependent presentation of the pieces of information. 相似文献