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91.
The solution of the incompressible Navier-Stokes equations in general two- and three-dimensional domains using a multigrid method is considered. Because a great variety of boundary-fitted grids may occur, robustness is at a premium. Therefore a new ILU smoother called CILU (collective ILU) is described, based on r-transformations. In CILU the matrix that is factorized is block-structured, with blocks corresponding to the set of physical variables. A multigrid algorithm using CILU as smoother is investigated. The performance of the algorithm in two and three dimensions is assessed by numerical experments. The results show that CILU is a good smoother for the incompressible Navier-Stokes equations discretized on general non-orthogonal curvilinear grids. 相似文献
92.
A. Bershadskii E. Dremencov D. Fukayama G. Yadid 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):581-585
Nonlinear statistical properties of Ventral Tegmental Area (VTA) of limbic brain are studied in vivo. VTA plays key role in generation of pleasure and in development of psychological drug addiction. It is shown that spiking
time-series of the VTA dopaminergic neurons exhibit long-range correlations with self-averaging behavior. This specific VTA
phenomenon has no relation to VTA rewarding function. Last result reveals complex role of VTA in limbic brain.
Received 17 April 2002 / Received in final form 30 September 2002 Published online 31 December 2002 相似文献
93.
本文利用广义投影矩阵,对求解无约束规划的超记忆梯度算法中的参数给出一种新的取值范围以保证得到目标函数的超记忆梯度广义投影下降方向,并与处理任意初始点的方法技巧结合建立求解非线性不等式约束优化问题的一个初始点任意的超记忆梯度广义投影算法,在较弱条件下证明了算法的收敛性.同时给出结合FR,PR,HS共轭梯度参数的超记忆梯度广义投影算法,从而将经典的共轭梯度法推广用于求解约束规划问题.数值例子表明算法是有效的. 相似文献
94.
95.
E. V. Pankratova V. N. Belykh E. Mosekilde 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):529-536
The present paper examines the influence of the forcing frequency on the
response of a randomly perturbed Hodgkin-Huxley system in the realm
of suprathreshold amplitudes. Our results show that, in the presence
of noise, the choice of driving frequency can seriously affect the
precision of the external information transmission. At the same
level of noise the precision can either decrease or increase
depending on the driving frequency. We demonstrate that the
destructive influence of noise on the interspike interval can be
effectively reduced. That is, with driving signals in certain
frequency ranges, the system can show stable periodic spiking even
for relatively large noise intensities. Here, the most accurate
transmission of an external signal occurs. Outside these frequency
ranges, noise of the same intensity destroys the regularity of the
spike trains by suppressing the generation of some spikes. On the
other hand, we show that noise can have a reconstructive role for
certain driving frequencies. Here, increasing noise intensity
enhances the coherence of the neuronal response. 相似文献
96.
C. Illert 《Il Nuovo Cimento D》1990,12(12):1611-1632
Summary Despite centuries of intense effort amongst mathematicians, and a huge literature in this field, there has previously never
been a generally valid mathematical model of ultrathin elastic ?shells? (actually surfaces) of revolution. This survey paper
presents the first theoretical framework capable of unifying, into a single coherent body of knowledge, a diversity of shapes
associated with elastic bows, car bumper-bars, molluscan shells, even flower-buds and pine-cones. It becomes apparent why
conventional analysis enjoys limited success when approximating elastic cones to perturbedcylinders anddiscs. Also the paper provides a theoretical basis for analysing the wrinkling of compressed engineering structures. These successes,
the new unification and the simplicity of relevant theory which maynever in principle be capable of working in this context. 相似文献
97.
The interaction between particle-like sources of the
nematic director distortions (e.g., colloids, point
defects, macromolecules in nematic emulsions) allows for a useful
analogy with the electrostatic multipole interaction between
charged bodies. In this paper we develop this analogy to the level
corresponding to the charge density and consider the general
status of the pairwise approach to the nematic emulsions with
finite-size colloids. It is shown that the elastic analog of the
surface electric charge density is represented by the two
transverse director components on the surface imposing the
director distortions. The elastic multipoles of a particle are
expressed as integrals over the charge density distribution on
this surface. Because of the difference between the scalar
electrostatics and vector nematostatics, the number of elastic
multipoles of each order is doubled compared to that in the
electrostatics: there are two elastic charges, two vectors of
dipole moments, two quadrupolar tensors, and so on. The
two-component elastic charge is expressed via the vector of
external mechanical torque applied on the particle. As a result,
the elastic Coulomb-like coupling between two particles is found
to be proportional to the scalar product of the two external
torques and does not directly depend on the particles' form and
anchoring. The real-space Green function method is used to develop
the pairwise approach to nematic emulsions and determine its form
and restrictions. The pairwise potentials are obtained in the
familiar form, but, in contrast to the electrostatics, they
describe the interaction between pairs (dyads) of the elastic
multipole moments. The multipole moments are shown to be uniquely
determined by the single-particle director field, unperturbed by
other particles. The pairwise approximation is applicable only in
the leading order in the small ratio particle
size-to-interparticle distance as the next order contains
irreducible three-body terms. 相似文献
98.
In this paper, we present a unified finite volume method preserving discrete maximum principle (DMP) for the conjugate heat transfer problems with general interface conditions. We prove the existence of the numerical solution and the DMP-preserving property. Numerical experiments show that the nonlinear iteration numbers of the scheme in [24] increase rapidly when the interfacial coefficients decrease to zero. In contrast, the nonlinear iteration numbers of the unified scheme do not increase when the interfacial coefficients decrease to zero, which reveals that the unified scheme is more robust than the scheme in [24]. The accuracy and DMP-preserving property of the scheme are also veried in the numerical experiments. 相似文献
99.
Numerical investigation of hydroplaning characteristics of three-dimensional patterned tire 总被引:6,自引:0,他引:6
J.R. Cho H.W. Lee J.S. Sohn G.J. Kim J.S. Woo 《European Journal of Mechanics - A/Solids》2006,25(6):914-926
Hydroplaning characteristics of patterned tire on wet road are investigated by making use of finite volume and finite element methods. A detailed 3-D patterned tire model is constructed by our in-house modeling program and the rainwater flow is considered as incompressible and inviscid. Meanwhile, the fluid–structure interaction between the highly complicated tire tread and the rainwater flow is effectively treated by the general coupling method. Through the numerical experiments, the rainwater flow drained through tire grooves, hydrodynamic pressure and contact force are investigated and compared with those of the three-grooved tire model. 相似文献
100.