全文获取类型
收费全文 | 274370篇 |
免费 | 3955篇 |
国内免费 | 839篇 |
专业分类
化学 | 144138篇 |
晶体学 | 4194篇 |
力学 | 12152篇 |
综合类 | 2篇 |
数学 | 32352篇 |
物理学 | 86326篇 |
出版年
2021年 | 2057篇 |
2020年 | 2392篇 |
2019年 | 2656篇 |
2018年 | 3599篇 |
2017年 | 3369篇 |
2016年 | 5236篇 |
2015年 | 3606篇 |
2014年 | 5175篇 |
2013年 | 12576篇 |
2012年 | 10512篇 |
2011年 | 12473篇 |
2010年 | 8505篇 |
2009年 | 8144篇 |
2008年 | 11281篇 |
2007年 | 11345篇 |
2006年 | 10546篇 |
2005年 | 9669篇 |
2004年 | 8781篇 |
2003年 | 7613篇 |
2002年 | 7361篇 |
2001年 | 7728篇 |
2000年 | 5925篇 |
1999年 | 4637篇 |
1998年 | 3877篇 |
1997年 | 3757篇 |
1996年 | 3700篇 |
1995年 | 3259篇 |
1994年 | 3243篇 |
1993年 | 3345篇 |
1992年 | 3469篇 |
1991年 | 3592篇 |
1990年 | 3332篇 |
1989年 | 3278篇 |
1988年 | 3273篇 |
1987年 | 3154篇 |
1986年 | 2964篇 |
1985年 | 4098篇 |
1984年 | 4273篇 |
1983年 | 3377篇 |
1982年 | 3668篇 |
1981年 | 3573篇 |
1980年 | 3440篇 |
1979年 | 3538篇 |
1978年 | 3627篇 |
1977年 | 3519篇 |
1976年 | 3663篇 |
1975年 | 3312篇 |
1974年 | 3344篇 |
1973年 | 3379篇 |
1972年 | 2319篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Raiko P. Zaikov 《Letters in Mathematical Physics》1994,32(4):283-297
Higher spin extensions of the non-Abelian gauge symmetries for the classical WZNW model are considered. Both linear and nonlinear realizations of the extended affine Kac-Moody algebra are obtained. It is a characteristic property of the WZNW model that it admits a higher spin linear realization of the extended affine Kac-Moody algebra which is equivalent to the corresponding higher spin nonlinear realization of the same algebra. However, in both cases, the higher spin Noether currents do not span an invariant space with respect to their generating transformations. Here, the current space is extended to an invariant space which allows us to gauge the symmetry.Supported by Bulgarian Foundation on Fundamental Research under contract Ph-318/93-95. 相似文献
992.
993.
L. Pillier C. Moreau X. Mercier J.F. Pauwels P. Desgroux 《Applied physics. B, Lasers and optics》2002,74(4-5):427-434
Cavity ring-down spectroscopy (CRDS) is used to measure the NO mole fraction formed in the burnt gases of low-pressure premixed
flames. It is shown that the line-of-sight absorption is greatly increased by the contribution of the NO molecules surrounding
the burner. This contribution has been quantified by developing a mathematical procedure taking into account the spatial and
spectral features of the CRDS measurement. Calculations have been undertaken in the general case of a stable species not consumed
in the flame. The most sensitive parameter is the temperature both in the flame and outside the flame. Simulations allow the
selection of the best spectroscopic transitions for a given flame (i.e. a given temperature profile), ensuring the weakest
influence of the inaccuracy affecting the temperature determination. High quantum states belonging to the A–X (0–1) band of
NO have been found to be the most valuable and have led to a NO mole fraction determination with an accuracy of ±13%. NO absorption
in the flame was completely masked using the A–X (0–0) band. Finally, the prompt-NO mole fraction formed in a methane/air
flame stabilized at 33 Torr is obtained by combining CRDS and laser induced fluorescence techniques.
Received: 12 October / Revised version: 1 February 2002 / Published online: 14 March 2002 相似文献
994.
We construct polynomial orthonormal bases in various function spaces. Our bases have linear order of growth of degrees of
polynomials. We show that this order is optimal. 相似文献
995.
It was studied the tin phase composition of the electrodeposited alloys produced at different temperatures and current densities from an acid chloride/fluoride electrolyte and an acid chloride bath. Mössbauer spectra were consistent with a Ni3Sn4 intermetallic compound, dissolved tin, and a Cu?Sn intermetallic compound formed at the interface of the copper substrate. 相似文献
996.
The elastic constants of dilute alloys based on bcc metals have been calculated using the Green’s function method obtaining
explicit expressions for change in elastic constants in terms oft-matrix. The crystal impurity problem is discussed within an impurity model containing central and non-central force constant
changes extended up to second neighbours of the impurity. The effect of volume change on elastic constants and a contribution
from electron pressure term are considered. Numerical results for changes in three elastic moduli have been presented for
a number of dilute alloys based on Mo, Nb, W, Ta and V. 相似文献
997.
Exact cylindrically symmetric solutions are obtained for a class of interacting scalar and vector fields in a rotating Godel Universe. We select those with the properties of solitons with smooth decrease of the fields to asymptotics and those with sharp boundaries (droplets). It is shown that only some of the droplets are stable with respect to perturbations that preserve cylindrical symmetry.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 24–27, May, 1991. 相似文献
998.
We report on calculations of the electric field gradient at the site of the Al nucleus in the Si-H-Al complex in silicon. As a model for the surroundings of the complex we used a cluster consisting of 43 silicon and one aluminum atoms. The geometry of this cluster was fully optimized at the Hartree-Fock level. To discuss the dependence of our results on the level of theory, we studied a subcluster of four silicon and one aluminum atoms at the Hartree-Fock and CASSCF level. 相似文献
999.
1000.
D. D. Bainov S. I. Kostadinov P. P. Zabreiko 《International Journal of Theoretical Physics》1992,31(8):1521-1526
Necessary and sufficient conditions for the existence of an exponential dichotomy of impulsive differential equations in a Hilbert space are found. 相似文献