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991.
《Journal of Nonlinear Mathematical Physics》2013,20(2):151-160
The flow of a superfluid film adsorbed on a porous medium can be modeled by a meromorphic differential on a Riemann surface of high genus. In this paper, we define the mixed Hodge metric of meromorphic differentials on a Riemann surface and justify using this metric to approximate the kinetic energy of a superfluid film flowing on a porous surface. 相似文献
992.
We use an estimator of quantum criticality based on the entanglement entropy to discuss the ground state properties of the 1D anisotropic Kondo necklace model. We found that the T=0 phase diagram of the model is described by a critical line separating an antiferromagnetic phase from a Kondo singlet state. Moreover we calculate the conformal anomaly on the critical line and obtain that c tends to 0.5 as the thermodynamic limit is reached. Hence we conclude that these transitions belong to Ising universality class being, therefore, second order transitions instead of infinite order as claimed before. 相似文献
993.
The differential thermal analysis (DTA) is utilized to determine the phase boundary and phase equilibria of Co–Cu alloy having a miscibility gap. Regions for various phase i.e., spinodal and coherent binodal, peritectic, magnetic and the transformation from the two phases to α phase transformations are distinctly determined for the Co–13 at%Cu alloy. The obtained results might indicate the continuity of the decomposition kinetics at the boundary between instable and the metastable regions but an activation barrier is needed. The activation energy for the magnetic transformation is determined to be 182.2 ± 2.1 kJ mol?1. 相似文献
994.
The local equilibrium hypothesis is a very successful basis for non-equilibrium thermodynamics over a wide range of phenomena and physical situations. However, the increasing interest in small systems in nanotechnology, in rarefied gases in high-altitude aeronautics, in high-frequency behaviour in information processing, or the search for new materials with sophisticated internal microstructures and tailored thermal properties have led one to ask about the limits of validity of this hypothesis, and to go beyond it. Here we do so in a constructive way, i.e. not only pointing out at these limits, but also embedding the local-equilibrium theory in a more general framework which explicitly exhibits these limits and suggests how to go beyond them, in search for a wider range of applications and a deeper understanding of the foundations. 相似文献
995.
L. Krlín R. Paprok V. Svoboda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(1):95-109
We model and discuss the possible types of motion that charged particles may
undergo in a stationary and spatially periodic electrostatic potential and a
homogeneous magnetic field. The model is considered to be the simplest
approximation of more complex phenomena of plasma edge turbulence in
tokamaks. Therein, low frequency turbulence appears in the plasma edge,
resulting in a fluctuation of the electron density, and also in the
generation of a turbulent electrostatic field. Typical parameters of this
turbulent electrostatic field are an electrical potential amplitude of
10–100 V and wave numbers k≈103 m-1. In our model, we consider these regimes, together
with a homogeneous magnetic field with a magnitude of 1 T. We investigate the
dynamics of singly-ionized carbon ions – a typical plasma impurity – with
kinetic energies on the order of 10 eV. Besides the obvious
Larmor and drift motions, a motion of random-walk and of Lévy walk
character appear therein.
All of these types of motion can play an important role in the modelling of
the anomalous diffusion of particles from the plasma edge turbulence region.
The dynamics mentioned will cause an inevitable escape of energetic
particles and thus of power loss from the thermonuclear reactor.
Moreover, Lévy walk kinetics represents a very interesting kind of
kinetics, currently of great interest, which was previously not so often
discussed. 相似文献
996.
We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains
in good and θ -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion
thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain
expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that,
we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion
and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing
when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size
ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a θ -solvent.
For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for
charged colloids plus polymers in a θ -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion.
Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we
demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing
polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction. 相似文献
997.
We consider a crosslinked polymer blend that may undergo a microphase separation. When the temperature is changed from an
initial value towards a final one very close to the spinodal point, the mixture is out equilibrium. The aim is the study of
dynamics at a given time t, before the system reaches its final equilibrium state. The dynamics is investigated through the structure factor, S(q, t), which is a function of the wave vector q, temperature T, time t, and reticulation dose D. To determine the phase behavior of this dynamic structure factor, we start from a generalized Langevin equation (model C) solved by the time composition fluctuation. Beside the standard de Gennes Hamiltonian, this equation incorporates a Gaussian
local noise, ζ. First, by averaging over ζ, we get an effective Hamiltonian. Second, we renormalize this dynamic field theory and write a Renormalization-Group equation
for the dynamic structure factor. Third, solving this equation yields the behavior of S(q, t), in space of relevant parameters. As result, S(q, t) depends on three kinds of lengths, which are the wavelength q
−1, a time length scale R(t) ∼ t
1/z
, and the mesh size ξ
*. The scale R(t) is interpreted as the size of growing microdomains at time t. When R(t) becomes of the order of ξ
*, the dynamics is stopped. The final time, t
*, then scales as t
* ∼ ξ
*
z, with the dynamic exponent z = 6−η. Here, η is the usual Ising critical exponent. Since the final size of microdomains ξ
* is very small (few nanometers), the dynamics is of short time. Finally, all these results we obtained from renormalization
theory are compared to those we stated in some recent work using a scaling argument. 相似文献
998.
P. Barahona O. Pea A.B. Antunes C. Campos G. Pecchi Y. Moreno C. Moure V. Gil 《Journal of magnetism and magnetic materials》2008,320(14):e61-e64
Partial substitution of manganese by cobalt in rare-earth perovskites REMnO3 leads to unusual magnetic phenomena because of the simultaneous presence of Mn3+, Mn4+, Co2+ and Co3+ species. The magnetic nature of the RE cation plays a fundamental role in the magnetic properties. We present herein two specific families: for RE=La the magnetic behavior of the |Co+Mn| network is observed, while for Gd its strong magnetic moment interacts with the transition metals, leading to a spin reversal state. Magnetic interactions are maximized at x=0.50, as if two regimes exist: for x<0.5 Co substitutes Mn in the REMnO3 manganite, and for x>0.5 Mn substitutes Co in the RECoO3 cobaltite. 相似文献
999.
碳富勒烯在水中的运动阻力特性 总被引:3,自引:1,他引:2
沈海军 《原子与分子物理学报》2008,25(3):523-527
采用分子动力学(MD)方法,模拟了Cn(n=60,180,240,540)以及C60@C240富勒烯在水中的速度衰减过程,得到了它们的阻力一速度与阻力,雷诺(Re)数关系曲线;进而将MD模拟的阻力结果和低Re数宏观流体力学中球的Stokes阻力解进行了对比,研究表明,低Re数下,富勒烯在水中的阻力要比传统流体力学中球的Stoke解高两个数量级;富勒烯在水中的阻力可通过Stokes解乘以(110.38-1.48/Re)近似估算. 相似文献
1000.
将弹性细杆的"Kirchhoff动力学比拟"方法推广到弹性薄壳,使弹性薄壳的变形在物理概念上和刚体的运动对应,在数学表述上等同,从而可以用刚体动力学的理论和方法研究弹性薄壳的变形,为连续的弹性薄壳提供新的离散化方法.在直法线假设下,在弹性中面上构筑空间正交轴系,此轴系沿坐标线"运动"的角速度构成两自变量的弯扭度.沿两个... 相似文献