全文获取类型
收费全文 | 3709篇 |
免费 | 198篇 |
国内免费 | 25篇 |
专业分类
化学 | 2533篇 |
晶体学 | 7篇 |
力学 | 108篇 |
数学 | 661篇 |
物理学 | 623篇 |
出版年
2024年 | 2篇 |
2023年 | 46篇 |
2022年 | 113篇 |
2021年 | 154篇 |
2020年 | 105篇 |
2019年 | 103篇 |
2018年 | 73篇 |
2017年 | 71篇 |
2016年 | 193篇 |
2015年 | 147篇 |
2014年 | 152篇 |
2013年 | 209篇 |
2012年 | 274篇 |
2011年 | 327篇 |
2010年 | 152篇 |
2009年 | 154篇 |
2008年 | 227篇 |
2007年 | 211篇 |
2006年 | 237篇 |
2005年 | 207篇 |
2004年 | 161篇 |
2003年 | 127篇 |
2002年 | 115篇 |
2001年 | 50篇 |
2000年 | 34篇 |
1999年 | 31篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 31篇 |
1995年 | 12篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 19篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1908年 | 2篇 |
排序方式: 共有3932条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
Juan Pablo Vielma 《Operations Research Letters》2007,35(1):29-35
Two independent proofs of the polyhedrality of the split closure of mixed integer linear program have been previously presented. Unfortunately neither of these proofs is constructive. In this paper, we present a constructive version of this proof. We also show that split cuts dominate a family of inequalities introduced by Köppe and Weismantel. 相似文献
6.
René Meziat Diego Patiño Pablo Pedregal 《Computational Optimization and Applications》2007,38(1):147-171
We propose an alternative method for computing effectively the solution of non-linear, fixed-terminal-time, optimal control
problems when they are given in Lagrange, Bolza or Mayer forms. This method works well when the nonlinearities in the control
variable can be expressed as polynomials. The essential of this proposal is the transformation of a non-linear, non-convex
optimal control problem into an equivalent optimal control problem with linear and convex structure. The method is based on
global optimization of polynomials by the method of moments. With this method we can determine either the existence or lacking
of minimizers. In addition, we can calculate generalized solutions when the original problem lacks of minimizers. We also
present the numerical schemes to solve several examples arising in science and technology. 相似文献
7.
Giovanni Tartarini Alessandra Lena Davide Passaro Lorenzo Rosa Stefano Selleri Pier Faccin Enrico Maria Fabbri 《Optical and Quantum Electronics》2006,38(9-11):869-876
A comprehensive numerical tool has been developed for the evaluation of the performances of Radio over Fiber (RoF) links intended for wireless signal distribution.At the transmitter end an appropriate set of rate equations allows to model the optical source as a solitary laser or as an appropriately injection locked laser. The optical channel is modeled putting into account the combined effect of fiber dispersion, laser source non ideal performances (e.g. non-linear effects, frequency chirp), and quadratic detection of the receiving photodiode. The simulation model developed can be a useful tool at the design stage allowing a preliminary evaluation of the characteristics of real RoF links. 相似文献
8.
J.E. Lorenzo H. Requardt 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):185-186
Eur. Phys. J. B 24, 315 (2001) Here we comment on a recently published paper on the presence of a phason contribution in the low temperature heat capacity data of the charge-density-wave compounds K0.3MoO3 and (TaSe4)2I. We have shown that the anomaly in the C
P
/
T
3
data reported by Odin et al. is straightforwardly interpreted in terms of low energy phonon modes resulting from the peculiar topology of these compounds.
Received 21 February 2002 Published online 19 July 2002 相似文献
9.
Abstract In [16] a visco-elastic relaxation system, called the relaxed Burnett system, was proposed by Jinand Slemrod as a moment approximation to the Boltzmann equation. The relaxed Burnett system is weaklyparabolic, has a linearly hyperbolic convection part, and is endowed with a generalized eotropy inequality. Itagrees with the solution of the Boltzmann equation up to the Burnett order via the Chapman-Enskog expansion. We develop a one-dimensional non-oscillatory numerical scheme based on the relaxed Burnett system forthe Boltzmann equation. We compare numerical results for stationary shocks based on this relaxation scheme,and those obtained by the DSMC (Direct Simulation Monte Carlo), by the Navier-Stokes equations and bythe extended thermodynamics with thirteen moments (the Grad equations). Our numerical experiments showthat the relaxed Burnett gives more accurate approximations to the shock profiles of the Boltzmann equationobtained by the DSMC, for a range of Mach numbers for hypersonic flows, th 相似文献
10.
Ignacio Moreno Pablo Velásquez Daniel Puerto Asticio Vargas 《Optics Communications》2006,260(1):12-18
In this work, we show a very simple birefringent filter useful to modulate a broadband light spectrum. We first show the generation of various oscillating spectra using two identical multiple-order waveplates. In particular a sinusoidal broadband spectrum with a rapid oscillation is obtained. This spectrum is amplitude modulated by adding another waveplate to the system. This waveplate has a small phase shift, and with the proper orientation generates amplitude beats on the broadband spectrum. Finally, we show how this system can be voltage controlled by means of a ferroelectric liquid crystal modulator. We experimentally demonstrate this behavior with the aid of a portable spectrophotometer, and we provide a theoretical explanation on the basis of the Jones matrix formalism. 相似文献