全文获取类型
收费全文 | 338463篇 |
免费 | 2739篇 |
国内免费 | 1002篇 |
专业分类
化学 | 184818篇 |
晶体学 | 5291篇 |
力学 | 13904篇 |
综合类 | 9篇 |
数学 | 35767篇 |
物理学 | 102415篇 |
出版年
2021年 | 2603篇 |
2020年 | 2926篇 |
2019年 | 3299篇 |
2018年 | 4433篇 |
2017年 | 4400篇 |
2016年 | 6302篇 |
2015年 | 3696篇 |
2014年 | 5764篇 |
2013年 | 14415篇 |
2012年 | 10944篇 |
2011年 | 13344篇 |
2010年 | 9527篇 |
2009年 | 9455篇 |
2008年 | 12816篇 |
2007年 | 12766篇 |
2006年 | 12098篇 |
2005年 | 10997篇 |
2004年 | 9821篇 |
2003年 | 9034篇 |
2002年 | 8754篇 |
2001年 | 10583篇 |
2000年 | 8017篇 |
1999年 | 6105篇 |
1998年 | 4817篇 |
1997年 | 4920篇 |
1996年 | 4585篇 |
1995年 | 3965篇 |
1994年 | 4060篇 |
1993年 | 3884篇 |
1992年 | 4504篇 |
1991年 | 4608篇 |
1990年 | 4415篇 |
1989年 | 4315篇 |
1988年 | 4233篇 |
1987年 | 4245篇 |
1986年 | 3975篇 |
1985年 | 5099篇 |
1984年 | 5261篇 |
1983年 | 4217篇 |
1982年 | 4445篇 |
1981年 | 4179篇 |
1980年 | 3964篇 |
1979年 | 4415篇 |
1978年 | 4627篇 |
1977年 | 4577篇 |
1976年 | 4542篇 |
1975年 | 4283篇 |
1974年 | 4253篇 |
1973年 | 4388篇 |
1972年 | 2947篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The long-range sound propagation from a deep ocean to a receiving system located on the shelf is modeled. The waveguide model is constructed on the basis of the data of an acoustic-oceanographic experiment carried out in the northwestern Pacific. The sensitivity and the frequency dependence of the difference in the sound field levels at the crossing of the frontal zone on the geoacoustic characteristics of the bottom of the shelf and the continental slope are investigated. It is shown that the level difference decreases by 8.2 dB as the velocity of longitudinal waves increases by 100 m/s in the range within 1490–1820 m/s. 相似文献
72.
73.
T. V. Maslova 《Russian Journal of Mathematical Physics》2006,13(4):425-430
The results obtained in V. P. Maslov’s article [1] can automatically be carried over to arbitrary semiotic systems if the
string of signs is sufficiently long. We shall show in this article, by using arguments based on the ideas of Kolmogorov complexity
and by applying the theorem of V. P. Maslov from [2], that one can obtain similar formulas for the distribution of various
semiotic objects. In order to do this, we must introduce notions generalizing the occurrence frequency of words in corpora
of texts. We also interpret a formula due to Maslov (appearing in [3]) from the point of view of the general semiotic notions
introduced here. 相似文献
74.
Off-the-shell anomalous factors of the two-body Coulomb transition matrices appear in the integral form of the Faddeev second-order
nuclear-electronic amplitude, for proton-hydrogen charge transfer scattering in a typical nlm → n′l′m′ transition. A symmetric-impulse approximation (SIA) is applied to eliminate these factors and an induction method is proposed
to analytically calculate the remaining integrals. The nuclear-electronic amplitude is derived for the general case, and for
totally symmetric collisions, in terms of generalized hypergeometric functions of two variables, F
4, and of one variable, 3
F
2, respectively. The angular distribution of the second-order nuclear-electronic charge transfer amplitude shows the Thomas
mechanism as a peak or a hump for symmetric and asymmetric collisions. There also exists a peak in the forward angular distribution
of the second-order nuclear-electronic amplitude, which partly cancels the kinematic peak in the angular distribution of the
charge transfer differential cross sections. 相似文献
75.
John T. Herron 《国际化学动力学杂志》1987,19(2):129-142
The gas phase chemical kinetics of SF4, SF5, and S2F10 are reviewed with particular emphasis on relevance to the general problem of the dielectric breakdown of SF6. Specific reaction systems treated are SF4 + F2, SF5 + SF5, and the pyrolysis of S2F10. Computer modeling calculations were carried out to arrive at the best estimates of rate parameters. Based on the results of these calculations, sets of recommended rate parameters are provided. The major discrepancies and problems in establishing the kinetic data base are described. Thermochemical consequences of different model calculations are given. 相似文献
76.
Phase synchronization in a system of three virtual-cathode microwave oscillators (vircators) simulated by coupled van der Pol oscillators is studied. The phasing dynamics of the vircators is visualized with the phase portraits of the system in the triangular coordinates. Different phasing conditions are found. 相似文献
77.
V. A. Zayats A. N. Nikolaevskii T. A. Filippenko O. P. Kniga G. A. Tikhonova 《Russian Journal of Applied Chemistry》2006,79(10):1651-1654
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied. 相似文献
78.
E. Kyriakopoulos 《General Relativity and Gravitation》1989,21(2):125-136
The class of previously found stationary axisymmetric perfect fluid solutions of Einstein's equations is written inh-orthogonal coordinates,h being a space-like coordinate. Matching of a big number of solutions of the class with each other seems to be possible for a proper choice of some parameters. The exterior solutions of the class are matched explicitly with interior solutions. Also, interior solutions are matched explicitly with each other. 相似文献
79.
T. Yu. Gumerov A. F. Dobrynina R. A. Yusupov V. P. Barabanov 《Russian Journal of Applied Chemistry》2006,79(12):1935-1939
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants. 相似文献
80.