全文获取类型
收费全文 | 363424篇 |
免费 | 2545篇 |
国内免费 | 754篇 |
专业分类
化学 | 168233篇 |
晶体学 | 5691篇 |
力学 | 18860篇 |
综合类 | 16篇 |
数学 | 53561篇 |
物理学 | 120362篇 |
出版年
2021年 | 2566篇 |
2020年 | 2756篇 |
2019年 | 3181篇 |
2018年 | 11550篇 |
2017年 | 12237篇 |
2016年 | 9593篇 |
2015年 | 4134篇 |
2014年 | 5784篇 |
2013年 | 12924篇 |
2012年 | 14053篇 |
2011年 | 22510篇 |
2010年 | 15006篇 |
2009年 | 14972篇 |
2008年 | 20083篇 |
2007年 | 23027篇 |
2006年 | 11045篇 |
2005年 | 14809篇 |
2004年 | 11295篇 |
2003年 | 10467篇 |
2002年 | 8722篇 |
2001年 | 8618篇 |
2000年 | 7007篇 |
1999年 | 5075篇 |
1998年 | 4344篇 |
1997年 | 4252篇 |
1996年 | 3810篇 |
1995年 | 3451篇 |
1994年 | 3287篇 |
1993年 | 3130篇 |
1992年 | 3508篇 |
1991年 | 3544篇 |
1990年 | 3439篇 |
1989年 | 3252篇 |
1988年 | 3252篇 |
1987年 | 3192篇 |
1986年 | 2987篇 |
1985年 | 3813篇 |
1984年 | 4134篇 |
1983年 | 3417篇 |
1982年 | 3611篇 |
1981年 | 3494篇 |
1980年 | 3331篇 |
1979年 | 3477篇 |
1978年 | 3695篇 |
1977年 | 3638篇 |
1976年 | 3631篇 |
1975年 | 3382篇 |
1974年 | 3362篇 |
1973年 | 3489篇 |
1972年 | 2301篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The procedure for calculating the dispersion of the refractive and absorption indices and thickness of an optical film, based on measurements of spectral dependence of the transmittance, is described. The film parameters are calculated using a solution of the approximation problem. The effect of the film model on the calculated values of the refractive and absorption indices is analyzed. 相似文献
122.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot. 相似文献
123.
O. Babelon 《Communications in Mathematical Physics》2006,266(3):819-862
The classical Volterra model, equipped with the Faddeev-Takhtajan Poisson bracket provides a lattice version of the Virasoro algebra. The Volterra model being integrable, we can express the dynamical variables in terms of the so-called separated variables. Taking the continuum limit of these formulae, we obtain the Virasoro generators written as determinants of infinite matrices, the elements of which are constructed with a set of points lying on an infinite genus Riemann surface. The coordinates of these points are separated variables for an infinite set of Poisson commuting quantities including L
0. The scaling limit of the eigenvector can also be calculated explicitly, so that the associated Schroedinger equation is in fact exactly solvable. 相似文献
124.
M. Brokate D. Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2006,13(4):385-411
The paper is concerned with the study of plasticity models described by differential equations with stop and play operators.
We suggest sufficient conditions for the global stability of a unique periodic solution for the scalar models and for the
vector models with biaxial inputs of a particular form, namely the sum of a uniaxial function and a constant term. For another
class of simple biaxial inputs, we present an example of the existence of unstable periodic solutions.
The paper was written during the research stay of D. Rachinskii at the Technical University Munich supported by the research
fellowship from the Alexander von Humboldt Foundation. His work was partially supported by the Russian Science Support Foundation, Russian Foundation for Basic Research (Grant No. 01-01-00146, 03-01-00258), and the Grants of the President of Russia (Grant No. MD-87.2003.01, NS-1532.2003.1). The support is gratefully acknowledged. 相似文献
125.
We consider the radiation from nonoscillating dipoles traveling with constant velocity directed parallel or antiparallel to
the velocity of a homogeneous transparent moving medium. It is assumed that the medium in its rest frame is isotropic and
has no spatial dispersion. We obtain expressions for the radiative energy losses and estimate the polarization energy losses
of electric and magnetic dipoles of different orientations. In particular, it is shown that the energy loss of a source is
negative if it moves in the direction of the medium motion and the source velocity is less than the medium velocity. Estimates
for the energy losses of dipoles in the cases of an electron beam and a flow of a weakly dispersive medium are given.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 6, pp. 502–512, June 2006. 相似文献
126.
The quantitative rainbow schlieren deflectometry (RSD) technique was applied to measure temperature and oxygen concentration in an axisymmetric hydrogen gas-jet diffusion flame burning in quiescent air at fuel jet exit Reynolds number of 70. Schlieren measurements were compared with conventional measurements using a thermocouple and a gas-sampling probe. Good agreement between the two measurement techniques was achieved on the fuel-lean side of the flame. 相似文献
127.
The problem of the stability of a heavy rigid body, bounded by the surface of an ellipsoid and with a cavity in the form of a coaxial ellipsoid, rolling along a straight line on a horizontal rough plane is investigated. It is shown that in the case of a body that is close to being dynamically symmetrical, parametric resonance always occurs leading to instability of the rolling. Each ellipsoid has its own “individual” resonance angular velocity. In the general case, regions in which the necessary stability conditions are satisfied can be distinguished in parameter space. The problem of calculating the resonance coefficient corresponding to instability for parametric resonance in a reversible third-order system is solved. 相似文献
128.
129.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
130.