全文获取类型
收费全文 | 440079篇 |
免费 | 3798篇 |
国内免费 | 1183篇 |
专业分类
化学 | 221222篇 |
晶体学 | 6981篇 |
力学 | 20982篇 |
综合类 | 18篇 |
数学 | 58503篇 |
物理学 | 137354篇 |
出版年
2020年 | 2689篇 |
2019年 | 2946篇 |
2018年 | 11451篇 |
2017年 | 12320篇 |
2016年 | 9283篇 |
2015年 | 4702篇 |
2014年 | 5842篇 |
2013年 | 15921篇 |
2012年 | 15949篇 |
2011年 | 26329篇 |
2010年 | 16539篇 |
2009年 | 16738篇 |
2008年 | 23122篇 |
2007年 | 26295篇 |
2006年 | 12874篇 |
2005年 | 18117篇 |
2004年 | 13818篇 |
2003年 | 12485篇 |
2002年 | 10346篇 |
2001年 | 11182篇 |
2000年 | 8689篇 |
1999年 | 6456篇 |
1998年 | 5019篇 |
1997年 | 4961篇 |
1996年 | 4947篇 |
1995年 | 4462篇 |
1994年 | 4261篇 |
1993年 | 3988篇 |
1992年 | 4861篇 |
1991年 | 4760篇 |
1990年 | 4462篇 |
1989年 | 4465篇 |
1988年 | 4501篇 |
1987年 | 4456篇 |
1986年 | 4236篇 |
1985年 | 5782篇 |
1984年 | 5793篇 |
1983年 | 4613篇 |
1982年 | 4840篇 |
1981年 | 4803篇 |
1980年 | 4560篇 |
1979年 | 4823篇 |
1978年 | 4934篇 |
1977年 | 4908篇 |
1976年 | 4746篇 |
1975年 | 4460篇 |
1974年 | 4348篇 |
1973年 | 4395篇 |
1972年 | 2807篇 |
1968年 | 2397篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
K. A. Bronnikov 《Annalen der Physik》1991,503(8):527-534
A multidimensional generalization of the Reissner-Nordström solution of general relativity is obtained for the case of n Ricci-flat internal spaces. A two-parameter family of black-hole solutions for an arbitrary dimensionality D is selected. Nontrivial black holes with D > 4 are shown to exist only with a nonzero electric charge. Observational consequences are discussed, in particular, a violation of Coulomb's law. 相似文献
52.
53.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献
54.
55.
56.
The quantitative rainbow schlieren deflectometry (RSD) technique was applied to measure temperature and oxygen concentration in an axisymmetric hydrogen gas-jet diffusion flame burning in quiescent air at fuel jet exit Reynolds number of 70. Schlieren measurements were compared with conventional measurements using a thermocouple and a gas-sampling probe. Good agreement between the two measurement techniques was achieved on the fuel-lean side of the flame. 相似文献
57.
58.
David K Bisset 《国际流体数值方法杂志》2002,39(10):961-977
Turbulent flow simulation methods based on finite differences are attractive for their simplicity, flexibility and efficiency, but not always for accuracy or stability. This paper demonstrates that a good compromise is possible with the advected grid explicit (AGE) method. Starting from the same initial field as a previous spectral DNS, AGE method simulations of a planar turbulent wake were carried out as DNS, and then at three levels of reduced resolution. The latter cases were in a sense large‐eddy simulations (LES), although no specific sub‐grid‐scale model was used. Results for the two DNS methods, including variances and power spectra, were very similar, but the AGE simulation required much less computational effort. Small‐scale information was lost in the reduced resolution runs, but large‐scale mean and instantaneous properties were reproduced quite well, with further large reductions in computational effort. Quality of results becomes more sensitive to the value chosen for one of the AGE method parameters as resolution is reduced, from which it is inferred that the numerical stability procedure controlled by the parameter is acting in part as a sub‐grid‐scale model. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
59.
C. Kimberling 《Aequationes Mathematicae》2002,63(1-2):158-167
60.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献