全文获取类型
收费全文 | 181142篇 |
免费 | 2561篇 |
国内免费 | 849篇 |
专业分类
化学 | 87282篇 |
晶体学 | 2062篇 |
力学 | 6896篇 |
综合类 | 29篇 |
数学 | 16395篇 |
物理学 | 50327篇 |
无线电 | 21561篇 |
出版年
2021年 | 1297篇 |
2020年 | 1467篇 |
2019年 | 1511篇 |
2018年 | 1772篇 |
2017年 | 1734篇 |
2016年 | 3043篇 |
2015年 | 1946篇 |
2014年 | 3037篇 |
2013年 | 7219篇 |
2012年 | 5919篇 |
2011年 | 7400篇 |
2010年 | 5117篇 |
2009年 | 5319篇 |
2008年 | 7117篇 |
2007年 | 7250篇 |
2006年 | 6816篇 |
2005年 | 6356篇 |
2004年 | 5674篇 |
2003年 | 4965篇 |
2002年 | 4914篇 |
2001年 | 5309篇 |
2000年 | 4195篇 |
1999年 | 3411篇 |
1998年 | 3050篇 |
1997年 | 2997篇 |
1996年 | 2716篇 |
1995年 | 2597篇 |
1994年 | 2545篇 |
1993年 | 2318篇 |
1992年 | 2557篇 |
1991年 | 2632篇 |
1990年 | 2408篇 |
1989年 | 2383篇 |
1988年 | 2285篇 |
1987年 | 1964篇 |
1986年 | 1928篇 |
1985年 | 2417篇 |
1984年 | 2519篇 |
1983年 | 2107篇 |
1982年 | 2262篇 |
1981年 | 2138篇 |
1980年 | 2073篇 |
1979年 | 2180篇 |
1978年 | 2320篇 |
1977年 | 2194篇 |
1976年 | 2245篇 |
1975年 | 2125篇 |
1974年 | 2171篇 |
1973年 | 2188篇 |
1972年 | 1438篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
111.
112.
Possible Loss and Recovery of Gibbsianness¶During the Stochastic Evolution of Gibbs Measures 总被引:1,自引:1,他引:0
A.C.D. van Enter R. Fernández F. den Hollander F. Redig 《Communications in Mathematical Physics》2002,226(1):101-130
We consider Ising-spin systems starting from an initial Gibbs measure ν and evolving under a spin-flip dynamics towards a
reversible Gibbs measure μ≠ν. Both ν and μ are assumed to have a translation-invariant finite-range interaction. We study
the Gibbsian character of the measure νS(t) at time t and show the following:
(1) For all ν and μ, νS(t) is Gibbs for small t.
(2) If both ν and μ have a high or infinite temperature, then νS(t) is Gibbs for all t > 0.
(3) If ν has a low non-zero temperature and a zero magnetic field and μ has a high or infinite temperature, then νS(t) is Gibbs for small t and non-Gibbs for large t.
(4) If ν has a low non-zero temperature and a non-zero magnetic field and μ has a high or infinite temperature, then νS(t) is Gibbs for small t, non-Gibbs for intermediate t, and Gibbs for large t.
The regime where μ has a low or zero temperature and t is not small remains open. This regime presumably allows for many different scenarios.
Received: 26 April 2001 / Accepted: 10 October 2001 相似文献
113.
F. Iachello S. Oss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):307-314
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years.
We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century.
Received 21 November 2001 相似文献
114.
R. F. Bikbaev 《Journal of Mathematical Sciences》1991,57(3):3078-3083
Diffraction by a semitransparent screen is considered in the framework of the nonlinear Schrödinger equation. The case of a defocusing medium is investigated. The method used represents a synthesis of the method of Riemann's matrix problem and the technique of Whitham's deformations of spectral curves.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, Vol. 179, pp. 23–31, 1989. 相似文献
115.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
116.
117.
118.
Francois P.-L. Monerie M. Vassallo C. Durteste Y. Alard F.R. 《Lightwave Technology, Journal of》1989,7(3):500-513
Depending on the spectal width of the source illuminating an interferometer, measurement procedures can utilize either the whole interferogram, or only the fringe envelope, or only the fringe quick oscillations. With an ultraband spectrum source, a simplified adaptation of the methods of Fourier transform spectroscopy yields the variations of the test-fiber propagation constant over the whole wavelength-interval of the source. Chromatic dispersion can then be computed from a single interferogram. With narrower spectrum sources, only the fringe envelopes are utilized and yield measurements of mode delay, with application to chromatic and polarization mode dispersion. In this case, however, interferograms at several wavelengths are necessary. With even narrower spectrum sources, the fringe quick oscillations provide measurements of phase shifts, related to changes in the mode propagation constant, when outside perturbations are applied to the test fiber. A direct method for measuring the third-order nonlinear susceptibilities is discussed. In this case the outside perturbation is an intense pump laser field 相似文献
119.
William F. Bowlin 《The Journal of the Operational Research Society》1987,38(2):127-135
The objective of this research is to evaluate a new methodology, data envelopment analysis (DEA), as a tool for measuring and evaluating the operational efficiency of US Air Force organizations. This study involves the application of DEA to locate possible inefficiencies in the performance of US Air Force real-property maintenance activities. Dynamic behaviour, as exhibited via window analyses, is reviewed along with static counterparts. The testing was done in close coordination with Air Force officials, who reviewed the results for accuracy, validity and relevance. We conclude that this type of efficiency analysis does have value for the Air Force, where it can serve as a guide to auditors, budget programmers, managers and others in measuring, evaluating and enhancing operational efficiency. 相似文献
120.
F. G. Gerasimato 《Journal of Mathematical Sciences》1991,57(5):3381-3383
We propose a simplified method of determining the integral characteristics of the opening of a parachute which makes it possible to compute the maximal stress on a parachute and the trajectory parameters of the motion of the load in the region of the opening of the parachute, and to determine the size of the portion of the canopy at the time of maximal stress.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 38–41. 相似文献