全文获取类型
收费全文 | 277013篇 |
免费 | 2040篇 |
国内免费 | 727篇 |
专业分类
化学 | 150104篇 |
晶体学 | 4161篇 |
力学 | 11289篇 |
综合类 | 7篇 |
数学 | 30541篇 |
物理学 | 83678篇 |
出版年
2021年 | 2409篇 |
2020年 | 2678篇 |
2019年 | 3078篇 |
2018年 | 4340篇 |
2017年 | 4315篇 |
2016年 | 5850篇 |
2015年 | 3150篇 |
2014年 | 5161篇 |
2013年 | 11881篇 |
2012年 | 9148篇 |
2011年 | 10912篇 |
2010年 | 8103篇 |
2009年 | 7940篇 |
2008年 | 10484篇 |
2007年 | 10431篇 |
2006年 | 9764篇 |
2005年 | 8795篇 |
2004年 | 7922篇 |
2003年 | 7266篇 |
2002年 | 7194篇 |
2001年 | 7728篇 |
2000年 | 6002篇 |
1999年 | 4500篇 |
1998年 | 3933篇 |
1997年 | 3875篇 |
1996年 | 3560篇 |
1995年 | 3027篇 |
1994年 | 3110篇 |
1993年 | 3134篇 |
1992年 | 3330篇 |
1991年 | 3430篇 |
1990年 | 3264篇 |
1989年 | 3281篇 |
1988年 | 3141篇 |
1987年 | 3064篇 |
1986年 | 2935篇 |
1985年 | 3771篇 |
1984年 | 3996篇 |
1983年 | 3240篇 |
1982年 | 3545篇 |
1981年 | 3325篇 |
1980年 | 3091篇 |
1979年 | 3356篇 |
1978年 | 3593篇 |
1977年 | 3626篇 |
1976年 | 3522篇 |
1975年 | 3354篇 |
1974年 | 3342篇 |
1973年 | 3447篇 |
1972年 | 2360篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Lerner E.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(2):259-263
A cosmological model is presented that produces He, C, O, D, Li, Be, and B in their observed abundances without a Big Bang. The elements are produced during the 1.5-Gy formation period of a galaxy, with C, O, and other heavy elements produced by stars of M >12 M3 , He by stars of 6 Ms<M <12 Ms, and D, Li, Be, and B by cosmic-ray reactions in a nearly pure H plasma halo. Thus, the model shows that the major elements used in astrophysical studies can be produced during galactic formation by exactly the same processes known to function today at much lower rates 相似文献
62.
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
63.
64.
O. A. Pshenitsyna 《Journal of Mathematical Sciences》2006,135(5):3384-3399
We consider the arithmetic properties of the factor-rank and term-rank functions for matrices over semirings. In particular,
we investigate the sets of matrices that satisfy the extremes of inequalities for these rank functions of matrix union. The
classification of the linear transformations that keep these sets invariant is obtained.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 9, No. 3, pp. 175–197, 2003. 相似文献
65.
N. O. Maksimova 《Journal of Mathematical Sciences》2006,135(1):2675-2679
In the article, it is proved that any nonnegative solution of an elliptic quasilinear inequality that vanishes on a subset
of positive measure is trivial.
__________
Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 112–118, 2005. 相似文献
66.
S. V. Ivanov V. V. Trachevskii O. S. Titova L. A. Zozulya 《Russian Journal of Applied Chemistry》2006,79(10):1712-1714
Experimental data demonstrate that a study of accelerated aging can enable prognostication of the working capacity and storage life of polymeric formulations used in aircraft components on the basis of changes in thermogravimetric constants of these polymeric formulations. 相似文献
67.
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
68.
69.
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
70.
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