全文获取类型
收费全文 | 4113篇 |
免费 | 694篇 |
国内免费 | 369篇 |
专业分类
化学 | 501篇 |
晶体学 | 88篇 |
力学 | 332篇 |
综合类 | 40篇 |
数学 | 1402篇 |
物理学 | 2337篇 |
无线电 | 476篇 |
出版年
2024年 | 6篇 |
2023年 | 50篇 |
2022年 | 98篇 |
2021年 | 87篇 |
2020年 | 105篇 |
2019年 | 97篇 |
2018年 | 96篇 |
2017年 | 90篇 |
2016年 | 109篇 |
2015年 | 115篇 |
2014年 | 200篇 |
2013年 | 309篇 |
2012年 | 193篇 |
2011年 | 184篇 |
2010年 | 203篇 |
2009年 | 261篇 |
2008年 | 264篇 |
2007年 | 262篇 |
2006年 | 234篇 |
2005年 | 237篇 |
2004年 | 193篇 |
2003年 | 184篇 |
2002年 | 231篇 |
2001年 | 170篇 |
2000年 | 162篇 |
1999年 | 156篇 |
1998年 | 145篇 |
1997年 | 108篇 |
1996年 | 81篇 |
1995年 | 70篇 |
1994年 | 63篇 |
1993年 | 46篇 |
1992年 | 37篇 |
1991年 | 35篇 |
1990年 | 26篇 |
1989年 | 27篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 30篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 20篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1972年 | 4篇 |
排序方式: 共有5176条查询结果,搜索用时 125 毫秒
931.
A.K. Kushwaha 《理论物理通讯》2008,50(6):1422-1426
A rigid-ion model is used to calculate the force constants and effective
dynamical charges of sulphide and selenide spinels. The Raman and infrared
phonon modes of normal cubic sulphide spinels MCr2Se4
(M = Mn, Co, Fe, Hg, Zn, and Cd) and selenide spinels MCr2Se4
(M = Hg, Zn, and Cd) are calculated at the first Brillouin zone-centre using above model. The
significant outcome of the present work is (i) the interatomic interaction
between Cr-S (Se) dominates over the
Cr-S(Se) and S-S(Se-Se) type of
interatomic interactions, (ii) the effective dynamical charges of the
bivalent metal ions are nearly zero, and (iii) the selenide spinels are less
ionic than the sulphide spinels and the ionicity decreases as
MnCr2S4 >
FeCr2S4 >
CoCr2S4 > and
CdCr2C4 >
ZnCr2C4 >
HgCr2C4
(C = S and Se). The zone-center phonon frequencies, calculated using these parameters, are
found to be in very good agreement with the observed results. 相似文献
932.
933.
934.
A lattice Boltzmann model with an amending function forsimulating nonlinear partial differential equations
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper proposes a lattice Boltzmann model with an
amending function for one-dimensional nonlinear partial
differential equations (NPDEs) in the form $u_t+\alpha uu_{xx}+\beta u^n u_x+\gamma u_{xxx}+\xi u_{xxxx}=0$. This model is
different from existing models because it lets the time step
be equivalent to the square of the space step and derives higher
accuracy and nonlinear terms in NPDEs. With the Chapman--Enskog
expansion, the governing evolution equation is recovered correctly
from the continuous Boltzmann equation. The numerical results
agree well with the analytical solutions. 相似文献
935.
Under harmonic approximation, this paper discusses the
linear dispersion relation of the one-dimensional chain. The existence
and evolution of discrete breathers in a general one-dimensional
chain are analysed for two particular examples of soft (Morse) and
hard (quartic) on-site potentials. The existence of discrete
breathers in one-dimensional and two-dimensional Morse lattices is
proved by using rotating wave approximation, local anharmonic
approximation and a numerical method. The localization and amplitude
of discrete breathers in the two-dimensional Morse lattice with on-site
harmonic potentials correlate closely to the Morse parameter a and
the on-site parameter к. 相似文献
936.
In this paper,we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field.We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero,the external magnetic field and impurity parameters have a great effect on it.Also,there exists a relation between the quantum phase transition and the entanglement.By modulating the temperature,magnetic field and the impurity parameters,the entanglement between any two lattices can exhibit platform-like behaviour,which can be used to realize entanglement switch. 相似文献
937.
In this paper an Eulerian rate-dependent single crystal model that accounts for high-strain rates, large strains and rotations is developed. The viscoplastic law as well as the evolution equations for the lattice are written in terms of vectorial and tensorial quantities associated with the current configuration. The viscoplastic law is obtained from Schmid law using an overstress approach. Such an expression for the viscoplastic law is motivated by the microdynamics of crystal defects. A general analysis of the plane-strain response of the proposed rigid-viscoplastic single crystal model is presented. It is shown that only one differential equation, involving the orientation of one composite in-plane slip system, is necessary to describe the lattice evolution. Several two-dimensional boundary value problems, such as equal-channel die extrusion and channel die compression are selected to illustrate the predictive capabilities of the model. The results show that even at relatively low strain rates the viscosity plays an important role in the development of localized deformation modes. At high crosshead velocity, the plastic properties and crystal anisotropy are less important while inertia effects are dominant. Finally, the grains interaction is investigated by analyzing the compression of a grains multicrystal. 相似文献
938.
In this paper, we extend a (2+2)-dimensional continuous zero curvature equation to (2+2)-dimensional discrete zero curvature equation, then a new (2+2)-dimensional cubic Volterra lattice hierarchy is obtained. Fhrthermore, the integrable coupling systems of the (2+2)-dimensional cubic Volterra lattice hierarchy and the generalized Toda lattice soliton equations are presented by using a Lie algebraic system sl(4). 相似文献
939.
The numerical simulation using the multiple relaxation time lattice Boltzmann method (MRT-LBM) is carried out for the purpose of investigating the two-dimensional flow around three circular cylinders. Among these three circular cylinders, one of the three cylinders on which a forced in-line vibrating is used to do this research and attempt to find out the effects of the movingcylinder and the other two rigid cylinders on the wake characteristics and vortex formation. As a benchmark problem to discuss the problem of lift coefficient r.m.s for these cylinders with spacing ratios T/D between other rigid side-by-side cylinders, and the calculation is carried out with two compared cases at Reynolds number of 100, two of the cylinders are rigid and the other one is an in-line vibrated cylinder lying downstream, in addition, forced vibrating amplitude and frequency are A/D= 0.5 and fν=0.4 (where A is the forced amplitude, D is the cylinder diameter, and fν stands for the vibrating frequency, respectively). The calculated results not onlyindicate that the spacing ratios T/D (T is the center-to-center spacing between the two upstream cylinders) have influence on the wake patterns and the formation of vortex shedding, but also analyze the lift coefficient r.m.s for the three cylinders with the spacing ratios S/D (where S is the center-to-center spacing between the center of upstream two side-by-side cylinders and downstream cylinder). 相似文献
940.
Sascha Vongehr 《理论物理通讯》2010,54(3):477-483
Theories with ingredients like the Higgs mechanism, gravitons, and inflatonfields rejuvenate the idea that relativistic kinematics is dynamicallyemergent. Eternal inflation treats the Hubble constant H as depending onlocation. Microscopic dynamics implies that H is over much smaller lengthsthan pocket universes to be understood as a local space reproduction rate.We illustrate this via discussing that even exponential inflation inTeV-gravity is slow on the relevant time scale. In our on small scalesinhomogeneous cosmos, a reproduction rate H depends on position. We therefore discuss Einstein-Strauss vacuoles and a Lindquist-Wheeler like lattice to connect the local rate properly with the scaling of an expanding cosmos. Consistency allows H to locally depend on Weyl curvature similar to vacuum polarization. We derive a proportionality constant known from Kepler's third law and discuss the implications for the finiteness of the cosmological constant. 相似文献