全文获取类型
收费全文 | 650089篇 |
免费 | 5755篇 |
国内免费 | 1912篇 |
专业分类
化学 | 335198篇 |
晶体学 | 9366篇 |
力学 | 32016篇 |
综合类 | 24篇 |
数学 | 82765篇 |
物理学 | 198387篇 |
出版年
2021年 | 5769篇 |
2020年 | 6272篇 |
2019年 | 7073篇 |
2018年 | 9225篇 |
2017年 | 9386篇 |
2016年 | 13283篇 |
2015年 | 7605篇 |
2014年 | 12301篇 |
2013年 | 29143篇 |
2012年 | 22826篇 |
2011年 | 27480篇 |
2010年 | 19973篇 |
2009年 | 19905篇 |
2008年 | 25713篇 |
2007年 | 25481篇 |
2006年 | 23477篇 |
2005年 | 21095篇 |
2004年 | 19511篇 |
2003年 | 17524篇 |
2002年 | 17244篇 |
2001年 | 18538篇 |
2000年 | 14330篇 |
1999年 | 11092篇 |
1998年 | 9436篇 |
1997年 | 9242篇 |
1996年 | 8740篇 |
1995年 | 7852篇 |
1994年 | 7764篇 |
1993年 | 7475篇 |
1992年 | 8040篇 |
1991年 | 8520篇 |
1990年 | 8006篇 |
1989年 | 7918篇 |
1988年 | 7734篇 |
1987年 | 7543篇 |
1986年 | 7208篇 |
1985年 | 9437篇 |
1984年 | 9746篇 |
1983年 | 8136篇 |
1982年 | 8565篇 |
1981年 | 7988篇 |
1980年 | 7684篇 |
1979年 | 8111篇 |
1978年 | 8405篇 |
1977年 | 8259篇 |
1976年 | 8235篇 |
1975年 | 7907篇 |
1974年 | 7687篇 |
1973年 | 8023篇 |
1972年 | 5654篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991. 相似文献
42.
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
43.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
44.
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
45.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
46.
P.A. Ramachandran 《Numerical Methods for Partial Differential Equations》2006,22(4):831-846
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献
47.
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
48.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
49.
In the following we find all of the three-dimensional flat spacetimes which are static and rotationally symmetric. 相似文献
50.