全文获取类型
收费全文 | 5279篇 |
免费 | 211篇 |
国内免费 | 33篇 |
专业分类
化学 | 3737篇 |
晶体学 | 19篇 |
力学 | 124篇 |
数学 | 887篇 |
物理学 | 756篇 |
出版年
2023年 | 41篇 |
2022年 | 52篇 |
2021年 | 93篇 |
2020年 | 116篇 |
2019年 | 112篇 |
2018年 | 68篇 |
2017年 | 56篇 |
2016年 | 156篇 |
2015年 | 140篇 |
2014年 | 181篇 |
2013年 | 282篇 |
2012年 | 320篇 |
2011年 | 365篇 |
2010年 | 256篇 |
2009年 | 208篇 |
2008年 | 322篇 |
2007年 | 324篇 |
2006年 | 314篇 |
2005年 | 312篇 |
2004年 | 250篇 |
2003年 | 214篇 |
2002年 | 226篇 |
2001年 | 87篇 |
2000年 | 79篇 |
1999年 | 76篇 |
1998年 | 61篇 |
1997年 | 67篇 |
1996年 | 73篇 |
1995年 | 47篇 |
1994年 | 40篇 |
1993年 | 28篇 |
1992年 | 23篇 |
1991年 | 31篇 |
1990年 | 21篇 |
1989年 | 34篇 |
1988年 | 20篇 |
1986年 | 25篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 28篇 |
1982年 | 35篇 |
1981年 | 25篇 |
1980年 | 26篇 |
1979年 | 20篇 |
1978年 | 38篇 |
1977年 | 26篇 |
1976年 | 17篇 |
1975年 | 13篇 |
1974年 | 21篇 |
1973年 | 16篇 |
排序方式: 共有5523条查询结果,搜索用时 0 毫秒
1.
R. Salomon 《Zeitschrift für Physik B Condensed Matter》1989,73(4):519-527
The diffusion constant and the diagonal conductivity for non-interacting electrons in a two-dimensional, disordered system are studied. A homogeneous magnetic field perpendicular to the electron system is assumed. For weak short-range random potentials and high fields the Landau quantum numbern can be used as expansion parameter. In the limit of high Landau levels the system shows metallic behaviour. Corrections for finiten decrease the conductivity and indicate localized states in the whole energy band. A breakdown of the expansion and stronger localization are observed only for the lowest Landau levels if the typical experimental length scale of the quantized Hall effect is used. 相似文献
2.
A PULSED LASER AND PULSE RADIOLYSIS STUDY OF AMPHIPHILIC CHLOROPHYLL DERIVATIVES WITH PDT ACTIVITY TOWARD MALIGNANT MELANOMA 总被引:1,自引:0,他引:1
L. Fiedor A. A. Gorman I. Hamblett V. Rosenbach-Belkin Y. Salomon A. Scherz I. Tregub 《Photochemistry and photobiology》1993,58(4):506-511
Two amphiphilic derivatives of chlorophyll, which have high potential as photodynamic therapy sensitizers for malignant melanoma have been investigated by a combination of laser flash photolysis and pulse radiolysis. It is shown that direct excitation of monomeric forms of these molecules in both hydrophilic and hydrophobic environments produces significant yields of the corresponding triplet states, which have been characterized in terms of spectral and kinetic parameters. In both environments, scavenging of the triplets by oxygen produces singlet oxygen, O2 (l Δ8 ), with essentially unit efficiency as evidenced by time-resolved IR luminescence measurements. 相似文献
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.
Ph. Laurent M. Abgrall Ch. Jentsch P. Lemonde G. Santarelli A. Clairon I. Maksimovic S. Bize Ch. Salomon D. Blonde J.F. Vega O. Grosjean F. Picard M. Saccoccio M. Chaubet N. Ladiette L. Guillet I. Zenone Ch. Delaroche Ch. Sirmain 《Applied physics. B, Lasers and optics》2006,84(4):683-690
In this paper we describe the cold atom clock PHARAO, designed for microgravity operation. All elements of the PHARAO engineering model have been manufactured and delivered to CNES, the French space agency. We present the clock design, its main characteristics, and initial science operation. PHARAO is one of the main components of the Atomic Clock Ensemble in Space payload that is scheduled to fly on board the International Space Station in 2010. PACS 07.87.+v; 06.30.Ft; 95.55.Sh; 32.80.Pj 相似文献
8.
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
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