全文获取类型
收费全文 | 99065篇 |
免费 | 6837篇 |
国内免费 | 7752篇 |
专业分类
化学 | 32911篇 |
晶体学 | 593篇 |
力学 | 7842篇 |
综合类 | 1435篇 |
数学 | 39762篇 |
物理学 | 31111篇 |
出版年
2023年 | 751篇 |
2022年 | 1493篇 |
2021年 | 1611篇 |
2020年 | 1754篇 |
2019年 | 2204篇 |
2018年 | 1769篇 |
2017年 | 2049篇 |
2016年 | 2221篇 |
2015年 | 1975篇 |
2014年 | 2928篇 |
2013年 | 5999篇 |
2012年 | 3527篇 |
2011年 | 4568篇 |
2010年 | 3599篇 |
2009年 | 5022篇 |
2008年 | 5591篇 |
2007年 | 5813篇 |
2006年 | 5463篇 |
2005年 | 4515篇 |
2004年 | 4578篇 |
2003年 | 4713篇 |
2002年 | 5012篇 |
2001年 | 4503篇 |
2000年 | 4311篇 |
1999年 | 4153篇 |
1998年 | 3732篇 |
1997年 | 2780篇 |
1996年 | 2089篇 |
1995年 | 1708篇 |
1994年 | 1560篇 |
1993年 | 1236篇 |
1992年 | 1222篇 |
1991年 | 949篇 |
1990年 | 882篇 |
1989年 | 771篇 |
1988年 | 676篇 |
1987年 | 537篇 |
1986年 | 519篇 |
1985年 | 589篇 |
1984年 | 607篇 |
1983年 | 266篇 |
1982年 | 474篇 |
1981年 | 557篇 |
1980年 | 460篇 |
1979年 | 382篇 |
1978年 | 354篇 |
1977年 | 273篇 |
1976年 | 201篇 |
1975年 | 146篇 |
1974年 | 154篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Summary. We generalise and apply a refinement indicator of the type originally designed by Mackenzie, Süli and Warnecke in [15] and
[16] for linear Friedrichs systems to the Euler equations of inviscid, compressible fluid flow. The Euler equations are symmetrized
by means of entropy variables and locally linearized about a constant state to obtain a symmetric hyperbolic system to which
an a posteriori error analysis of the type introduced in [15] can be applied. We discuss the details of the implementation of the refinement
indicator into the DLR--Code which is based on a finite volume method of box type on an unstructured grid and present numerical results.
Received May 15, 1995 / Revised version received April 17, 1996 相似文献
63.
M. M. Moustafa 《Journal of Thermal Analysis and Calorimetry》1997,50(3):463-471
The oxime and Schiff's base of N-furoylphenylhydroxylamine form complexes with Co2+, Cu2+, Zn2+ and Fe3+. These complexes were studied by means of the UV — Vis. spectra of nujol mulls, electron spin resonance (ESR) spectra and magnetic susceptibility to determine their stereochemistry. The complexes were characterized via elemental analyses, molar conductivities and thermogravimetric analyses. Organic reagents were used for the gravimetric determination of Co2+, Cu2+ and Fe3+ through the precipitation of their complexes. The compounds were also used for separation of a binary mixture of Cu2+ and Cu2+. Interferences were studied. 相似文献
64.
R.C. Viscovini E.M. Telles A. Scalabrin D. Pereira 《Applied physics. B, Lasers and optics》1997,65(1):33-35
2 laser of wide tunability to pump 13CD3OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared
absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength,
polarisation, optimum pressure of operation and precise offset measurements.
Received: 17 September 1996/Revised version: 18 November 1996 相似文献
65.
66.
Summary. Let be a square matrix dependent on parameters and , of which we choose as the eigenvalue parameter. Many computational problems are equivalent to finding a point such that has a multiple eigenvalue at . An incomplete decomposition of a matrix dependent on several parameters is proposed. Based on the developed theory two new algorithms are
presented for computing multiple eigenvalues of with geometric multiplicity . A third algorithm is designed for the computation of multiple eigenvalues with geometric multiplicity but which also appears to have local quadratic convergence to semi-simple eigenvalues. Convergence analyses of these methods
are given. Several numerical examples are presented which illustrate the behaviour and applications of our methods.
Received December 19, 1994 / Revised version received January 18, 1996 相似文献
67.
68.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
69.
Summary In the analysis of discretization methods for stiff intial value problems, stability questions have received most part of the attention in the past.B-stability and the equivalent criterion algebraic stability are well known concepts for Runge-Kutta methods applied to dissipative problems. However, for the derivation ofB-convergence results — error bounds which are not affected by stiffness — it is not sufficient in many cases to requireB-stability alone. In this paper, necessary and sufficient conditions forB-convergence are determined.This paper was written while J. Schneid was visiting the Centre for Mathematics and Computer Science with an Erwin-Schrödinger stipend from the Fonds zur Förderung der wissenschaftlichen Forschung 相似文献
70.
Summary We present an approximation method of a space-homogeneous transport equation which we prove is convergent. The method is very promising for numerical computation. Comparison of a numerical computation with an exact solution is given for the Master equation. 相似文献