全文获取类型
收费全文 | 512948篇 |
免费 | 4094篇 |
国内免费 | 1422篇 |
专业分类
化学 | 251561篇 |
晶体学 | 7993篇 |
力学 | 25031篇 |
综合类 | 3篇 |
数学 | 71287篇 |
物理学 | 162589篇 |
出版年
2020年 | 3257篇 |
2019年 | 3823篇 |
2018年 | 12002篇 |
2017年 | 12620篇 |
2016年 | 10475篇 |
2015年 | 5286篇 |
2014年 | 7339篇 |
2013年 | 19581篇 |
2012年 | 17732篇 |
2011年 | 27837篇 |
2010年 | 18001篇 |
2009年 | 17877篇 |
2008年 | 24708篇 |
2007年 | 27699篇 |
2006年 | 15204篇 |
2005年 | 19363篇 |
2004年 | 15349篇 |
2003年 | 13982篇 |
2002年 | 12169篇 |
2001年 | 12714篇 |
2000年 | 9863篇 |
1999年 | 7587篇 |
1998年 | 6470篇 |
1997年 | 6412篇 |
1996年 | 6157篇 |
1995年 | 5631篇 |
1994年 | 5406篇 |
1993年 | 5504篇 |
1992年 | 5882篇 |
1991年 | 6063篇 |
1990年 | 5682篇 |
1989年 | 5619篇 |
1988年 | 5713篇 |
1987年 | 5488篇 |
1986年 | 5226篇 |
1985年 | 7100篇 |
1984年 | 7452篇 |
1983年 | 6065篇 |
1982年 | 6548篇 |
1981年 | 6344篇 |
1980年 | 6197篇 |
1979年 | 6358篇 |
1978年 | 6670篇 |
1977年 | 6335篇 |
1976年 | 6609篇 |
1975年 | 5998篇 |
1974年 | 6108篇 |
1973年 | 6461篇 |
1972年 | 4257篇 |
1971年 | 3439篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
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
64.
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
65.
66.
R. J. Vanderbei 《Mathematical Programming》1989,43(1-3):31-44
The affine-scaling modification of Karmarkar's algorithm is extended to solve problems with free variables. This extended primal algorithm is used to prove two important results. First the geometrically elegant feasibility algorithm proposed by Chandru and Kochar is the same algorithm as the one obtained by appending a single column of residuals to the constraint matrix. Second the dual algorithm as first described by Adler et al., is the same as the extended primal algorithm applied to the dual. 相似文献
67.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot. 相似文献
68.
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
69.
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
70.
R. J. Hinde 《Few-Body Systems》2006,38(2-4):187-191
We compute the vibrational coupling between two H2 molecules from ab initio quantum chemical calculations of the H2-H2 potential carried out at the full configuration interaction level of theory using the atom-centered aug-cc-pVTZ basis set
for hydrogen. We compare the full configuration interaction results with those obtained using two variants of coupled cluster
theory and find that a fully iterative treatment of connected triples may be required to estimate the H2-H2 vibrational coupling accurately using coupled cluster theory. 相似文献