全文获取类型
收费全文 | 237128篇 |
免费 | 3062篇 |
国内免费 | 1289篇 |
专业分类
化学 | 120115篇 |
晶体学 | 4032篇 |
力学 | 10973篇 |
综合类 | 45篇 |
数学 | 25977篇 |
物理学 | 80337篇 |
出版年
2020年 | 1963篇 |
2019年 | 2237篇 |
2018年 | 2873篇 |
2017年 | 2782篇 |
2016年 | 4157篇 |
2015年 | 2596篇 |
2014年 | 4237篇 |
2013年 | 10377篇 |
2012年 | 7895篇 |
2011年 | 9753篇 |
2010年 | 6947篇 |
2009年 | 6917篇 |
2008年 | 9006篇 |
2007年 | 8990篇 |
2006年 | 8518篇 |
2005年 | 7703篇 |
2004年 | 7074篇 |
2003年 | 6251篇 |
2002年 | 6237篇 |
2001年 | 7235篇 |
2000年 | 5463篇 |
1999年 | 4336篇 |
1998年 | 3625篇 |
1997年 | 3532篇 |
1996年 | 3360篇 |
1995年 | 3051篇 |
1994年 | 3005篇 |
1993年 | 3073篇 |
1992年 | 3169篇 |
1991年 | 3373篇 |
1990年 | 3121篇 |
1989年 | 3053篇 |
1988年 | 3078篇 |
1987年 | 2967篇 |
1986年 | 2811篇 |
1985年 | 3827篇 |
1984年 | 4011篇 |
1983年 | 3204篇 |
1982年 | 3411篇 |
1981年 | 3341篇 |
1980年 | 3230篇 |
1979年 | 3335篇 |
1978年 | 3422篇 |
1977年 | 3350篇 |
1976年 | 3448篇 |
1975年 | 3141篇 |
1974年 | 3150篇 |
1973年 | 3194篇 |
1972年 | 2235篇 |
1971年 | 1849篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
161.
Well-Posedness by Perturbations of Variational Problems 总被引:3,自引:0,他引:3
Lemaire B. Ould Ahmed Salem C. Revalski J. P. 《Journal of Optimization Theory and Applications》2002,115(2):345-368
In this paper, we consider the extension of the notion of well-posedness by perturbations, introduced by Zolezzi for optimization problems, to other related variational problems like inclusion problems and fixed-point problems. Then, we study the conditions under which there is equivalence of the well-posedness in the above sense between different problems. Relations with the so-called diagonal well-posedness are also given. Finally, an application to staircase iteration methods is presented. 相似文献
162.
Zarubitskii O. G. Budnik V. G. Omel'chuk A. A. Melekhin V. T. Opanasyuk V. P. Zakharchenko N. F. 《Russian Journal of Applied Chemistry》2002,75(4):558-561
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry. 相似文献
163.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
164.
We show that if A is an abelian compact Lie group, all A-equivariant complex vector bundles are orientable over a complex orientable equivariant cohomology theory. In the process,
we calculate the complex orientable homology and cohomology of all complex Grassmannians.
Received: 14 February 2000; in final form: 4 August 2000 / Published online: 19 October 2001 相似文献
165.
The procedure for calculating the dispersion of the refractive and absorption indices and thickness of an optical film, based on measurements of spectral dependence of the transmittance, is described. The film parameters are calculated using a solution of the approximation problem. The effect of the film model on the calculated values of the refractive and absorption indices is analyzed. 相似文献
166.
In this paper, we consider linear combinations of modified Baskakov operators. By use of several lemmas, we obtain the inverse
theorem (Theorem 1.1) and the saturation (Theorem 1.2) for those linear combinations. 相似文献
167.
168.
B. P. Harlamov 《Journal of Mathematical Sciences》2006,133(3):1371-1377
An inverse process with independent positive increments is considered. For such a process, the first hitting time τx of level x as a function of x ≥ 0 is a proper process with independent positive increments. In terms of first hitting times
and their Levy measures, multidemensional distribution densities and Laplace transformations are derived. Stationary distributions
of increments of the process are investigated. Bibliography: 8 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 311, 2004, pp. 286–297. 相似文献
169.
The dynamics of multiphoton transitions in a two-level spin system excited by transverse microwave and longitudinal RF fields with the frequencies ωmw and ωrf, respectively, is analyzed. The effective time-independent Hamiltonian describing the “dressed” spin states of the “spin + bichromatic field” system is obtained by using the Krylov-Bogoliubov-Mitropolsky averaging method. The direct detection of the time behavior of the spin system by the method of nonstationary nutations makes it possible to identify the multiphoton transitions for resonances ω0 = ωmw + rωrf (ω0 is the central frequency of the EPR line, r = 1, 2), to measure the amplitudes of the effective fields of these transitions, and to determine the features generated by the inhomogeneous broadening of the EPR line. It is shown that the Bloch-Siegert shifts for multiphoton resonances at the inhomogeneous broadening of spectral lines reduce only the nutation amplitude but do not change their frequencies. 相似文献
170.
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