全文获取类型
收费全文 | 526590篇 |
免费 | 4288篇 |
国内免费 | 1353篇 |
专业分类
化学 | 257420篇 |
晶体学 | 8353篇 |
力学 | 26698篇 |
综合类 | 9篇 |
数学 | 73339篇 |
物理学 | 166412篇 |
出版年
2020年 | 3509篇 |
2019年 | 3973篇 |
2018年 | 12076篇 |
2017年 | 12683篇 |
2016年 | 10811篇 |
2015年 | 5249篇 |
2014年 | 7573篇 |
2013年 | 19081篇 |
2012年 | 17583篇 |
2011年 | 27065篇 |
2010年 | 17975篇 |
2009年 | 17886篇 |
2008年 | 24333篇 |
2007年 | 27143篇 |
2006年 | 15532篇 |
2005年 | 18817篇 |
2004年 | 15375篇 |
2003年 | 14225篇 |
2002年 | 12528篇 |
2001年 | 12889篇 |
2000年 | 10092篇 |
1999年 | 7685篇 |
1998年 | 6720篇 |
1997年 | 6557篇 |
1996年 | 6381篇 |
1995年 | 5810篇 |
1994年 | 5881篇 |
1993年 | 5692篇 |
1992年 | 6171篇 |
1991年 | 6330篇 |
1990年 | 6061篇 |
1989年 | 5876篇 |
1988年 | 6011篇 |
1987年 | 5783篇 |
1986年 | 5460篇 |
1985年 | 7427篇 |
1984年 | 7765篇 |
1983年 | 6443篇 |
1982年 | 6708篇 |
1981年 | 6611篇 |
1980年 | 6493篇 |
1979年 | 6589篇 |
1978年 | 6971篇 |
1977年 | 6721篇 |
1976年 | 6903篇 |
1975年 | 6366篇 |
1974年 | 6390篇 |
1973年 | 6596篇 |
1972年 | 4617篇 |
1971年 | 3862篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Panasyugin A. S. Rat'ko A. I. Bondareva G. V. 《Russian Journal of Applied Chemistry》2002,75(11):1824-1827
The sorption properties of mixed adsorbent-catalyst based on high-silica zeolite and montmorillonite modified with mixed oxides of Cr(III) and Cu(II) with respect to organic compounds of various classes were studied, and the optimal dynamic conditions of its operation were determined. 相似文献
942.
943.
The exact solution is constructed to a torsion problem for a circular elastic shaft in a medium referred to a spherical coordinate system. One end of the shaft is rigidly fixed and the other is subjected to either tangential forces or a torque. New integral transforms are obtained to solve the problem. 相似文献
944.
945.
Gabriel N. Gatica Ernst P. Stephan 《Numerical Methods for Partial Differential Equations》2002,18(1):105-128
This article deals with an expanded mixed finite element formulation, based on the Hu‐Washizu principle, for a nonlinear incompressible material in the plane. We follow our related previous works and introduce both the stress and the strain tensors as further unknowns, which yields a two‐fold saddle point operator equation as the corresponding variational formulation. A slight generalization of the classical Babu?ka‐Brezzi's theory is applied to prove unique solvability of the continuous and discrete formulations, and to derive the corresponding a priori error analysis. An extension of the well‐known PEERS space is used to define an stable associated Galerkin scheme. Finally, we provide an a posteriori error analysis based on the classical Bank‐Weiser approach. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 105–128, 2002 相似文献
946.
In an earlier paper on a malignant cell invasion model (Marchantet al., SIAM J. Appl. Math, 60, 2000) we introduced a novelform of discontinuous travelling wave solution. These solutionscould be studied easily by combining behaviour within a phaseplane with the RankineHugoniot shock conditions, whichdescribe properties (such as the ratio of the jump discontinuitiesto the speed of propagation) that solutions may possess. Theseresults were new for several reasons. The shock conditions relateto hyperbolic equations (which the model is) but were appliedin a travelling wave ordinary differential equation phase planeusing techniques that usually apply to parabolic reactiondiffusionsystems. In addition the solutions possess singular behaviournear several points in the phase plane but in spite of thisthere exists a robust and stable family of physically interestingsolutions. In this paper we discuss two previously studied models, oneof detonation theory and one of angiogenesis. We show that eachof these models also possesses a family of discontinuous travellingwave solutions which was not previously discovered. Of particularinterest is the solution which has a blunt interface at thefront of the invading profile. In all three models it is thissolution that is seen to stably evolve from physically relevantinitial data, and for physically relevant parameter values. This work confirms the robustness of these novel travellingwave solutions and their applicability to a wider range of mathematicalmodelling situations. 相似文献
947.
Yu. G. Abov A. D. Gul'ko F. S. Dzheparov S. V. Stepanov S. S. Trostin 《Physics of Atomic Nuclei》2002,65(11):1999-2008
The nuclear magnetic resonance in beta-active nuclei 8Li at the doubled Larmor frequency in LiF polycrystals is studied before and after treating these polycrystals with an external pressure. A quantitative approach is proposed that makes it possible to calculate the parameters of the resonance line-shape function versus the dislocation structure of crystallites. Data suggesting that the samples under investigation that were subjected to a treatment with an external pressure develop dislocations whose Burgers vectors are parallel are obtained. 相似文献
948.
The Fokker–Planck-type kinetic equation is constructed with the help of the evolution equation for the transverse energy of channelized particles, which in its turn is derived beyond the framework of perturbation theory proceeding from the condition of nonconcervation of the adiabatic invariant. 相似文献
949.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
950.
D.A. Garanin E.M. Chudnovsky 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):3-7
We compute the width and shape of the EPR and tunneling resonances due to dislocations in Mn12 acetate crystals. Uncorrelated dislocations produce the Gaussian shape of resonances while dislocations bound in pairs produce
the Lorentzian shape. We stress that the uniaxial spin Hamiltonian together with crystal defects can explain the totality
of experimental data on Mn12.
Received 2 August 2001 / Received in final form 15 March 2002 Published online 17 September 2002 相似文献