全文获取类型
收费全文 | 409258篇 |
免费 | 3092篇 |
国内免费 | 956篇 |
专业分类
化学 | 190623篇 |
晶体学 | 6464篇 |
力学 | 21431篇 |
综合类 | 7篇 |
数学 | 59930篇 |
物理学 | 134851篇 |
出版年
2021年 | 3150篇 |
2020年 | 3369篇 |
2019年 | 3803篇 |
2018年 | 11939篇 |
2017年 | 12645篇 |
2016年 | 10530篇 |
2015年 | 4852篇 |
2014年 | 7165篇 |
2013年 | 16090篇 |
2012年 | 15851篇 |
2011年 | 24858篇 |
2010年 | 16855篇 |
2009年 | 16834篇 |
2008年 | 21901篇 |
2007年 | 24651篇 |
2006年 | 12375篇 |
2005年 | 15942篇 |
2004年 | 12544篇 |
2003年 | 11476篇 |
2002年 | 9884篇 |
2001年 | 10530篇 |
2000年 | 7941篇 |
1999年 | 6007篇 |
1998年 | 5010篇 |
1997年 | 4829篇 |
1996年 | 4654篇 |
1995年 | 3966篇 |
1994年 | 3912篇 |
1993年 | 3784篇 |
1992年 | 4169篇 |
1991年 | 4380篇 |
1990年 | 4169篇 |
1989年 | 4086篇 |
1988年 | 3867篇 |
1987年 | 4002篇 |
1986年 | 3763篇 |
1985年 | 4721篇 |
1984年 | 4785篇 |
1983年 | 3985篇 |
1982年 | 4065篇 |
1981年 | 3787篇 |
1980年 | 3743篇 |
1979年 | 4027篇 |
1978年 | 4024篇 |
1977年 | 3945篇 |
1976年 | 3944篇 |
1975年 | 3727篇 |
1974年 | 3666篇 |
1973年 | 3725篇 |
1972年 | 2639篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Nikulin S. S. Akatova I. N. Kondrat'eva N. A. 《Russian Journal of Applied Chemistry》2003,76(4):652-655
The influence of the charge of a metal cation and the nature of a coagulant on the recovery of butadiene-styrene rubber and properties of rubber stocks and vulcanizates was examined. 相似文献
942.
Infrared difference spectroscopy has been used to study the association of p-nitrophenol (NP) with butyl acetate (BA) in CCl4 and in undiluted BA. It has been shown that in CCl4, an associate is formed, [NP·BA] ·BA (Ia), in which one molecule of BA is linked to the NP by a hydrogen bond, and the second BA molecule is linked to the H-complex NP·BA by outer-sphere (dipole-dipole) interaction. In undiluted BA with low concentrations of NP, (Ia) is formed; with high concentrations of NP, an associate [(NP)2BA] ·mBA is formed, in which two molecules of NP are bonded successively to each other and with a BA molecule; and the number of outer-sphere BA molecules may depend on the concentration of free BA molecules in the solutions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 593–599, March, 1991. 相似文献
943.
A formulation of an implicit characteristic-flux-averaging method for the unsteady Euler equations with real gas effects is presented. Incorporation of a real gas into a general equation of state is achieved by considering the pressure as a function of density and specific internal energy. The Ricmann solver as well as the flux-split algorithm are modified by introducing the pressure derivatives with respect to density and internal energy. Expressions for calculating the values of the flow variables for a real gas at the cell faces are derived. The Jacobian matrices and the eigenvectors are defined for a general equation of state. The solution of the system of equations is obtained by using a mesh-sequencing method for acceleration of the convergence. Finally, a test case for a simple form of equation of state displays the differences from the corresponding solution for an ideal gas. 相似文献
944.
E. S. Moskalenko M. Larsson K. F. Karlsson P. O. Holtz B. Monemar W. V. Schoenfeld P. M. Petroff 《Physics of the Solid State》2007,49(10):1995-1998
We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral
external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external
and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially
faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed
effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity
measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications.
The text was submitted by the authors in English. 相似文献
945.
A. Speranza 《Russian Journal of Mathematical Physics》2007,14(2):238-242
A mathematical theory for estimating the mobility of localized unstable atmospheric disturbances evolving into vortices is
discussed. 相似文献
946.
N. B. Voznesensky E. V. Gavrilov A. P. Zhevlakov V. K. Kirillovskiĭ P. V. Orlov 《Technical Physics》2007,52(2):271-275
Methods and schemes to inspect the EUV mirror shape are developed on the basis of a point diffraction interferometer with computer processing of interferograms. A measurement accuracy to within 0.001 of a wavelength in the visual range is achieved. 相似文献
947.
A. D. Krisch 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):417-423
There will be a review of the history of polarized proton beams, and a discussion of the unexpected and still unexplained
large transverse spin effects found in several high-energy proton-proton spin experiments at the ZGS, AGS and Fermilab. Next,
there will be a discussion of present and possible future experiments on the violent elastic collisions of polarized protons
at IHEP-Protvino's 70GeV U-70 accelerator in Russia and the new high-intensity 50GeV J-PARC facility being built at Tokai
in Japan. 相似文献
948.
P. Danchev 《Lithuanian Mathematical Journal》2007,47(2):129-134
We prove the following theorem: Any abelian p-group is an n-Σ-group which is a strong ω-elongation of a totally projective group by a p
ω+n
-projective group precisely when it is totally projective. In particular, each p-torsion p
ω+n
-projective n-Σ-group is a direct sum of countable p-groups of length not exceeding ω + n and vice versa. These two claims generalize our recent results in [6] and [7].
Published in Lietuvos Matematikos Rinkinys, Vol. 47, No. 2, pp. 155–162, April–June, 2007. 相似文献
949.
We investigate two families of Lorenz-like three-dimensional nonlinear dynamical systems (i) the generalized Lorenz system and (ii) the Burke–Shaw system. Analytical investigation of the former system is possible under the assumption (I) which in fact concerns four different systems corresponding to = ±1, m = 0, 1. The fixed points and stability characteristics of the Lorenz system under the assumption (I) are also classified. Parametric and temporal (t → ∞) asymptotes are also studied in connection to the memory of both the systems. We calculate the Lyapunov exponents and Lyapunov dimension for the chaotic attractors in order to study the influence of the parameters of the Lorenz system on the attractors obtained not only when the assumption (I) is satisfied but also for other values of the parameters σ, r, b, ω and m. 相似文献
950.
V. S. Zuev 《Optics and Spectroscopy》2007,102(5):742-753
The results of experiments, in which the probability of spontaneous Raman scattering from a molecule adsorbed at the surface of a silver nanoparticle was found to grow by 14 and more orders of magnitude, are interpreted. The molecule occurs in the field of a surface plasmon, which accounts for an increase in the local field strength and the density of states by 12–13 orders of magnitude. An additional increase by 1–2 orders of magnitude is explained by the antenna effect of a pair of nanoparticles, one being ultimately small and the other, sufficiently large to serve a receiving-transmitting antenna. 相似文献