全文获取类型
收费全文 | 717篇 |
免费 | 133篇 |
国内免费 | 46篇 |
专业分类
化学 | 180篇 |
晶体学 | 8篇 |
力学 | 48篇 |
综合类 | 1篇 |
数学 | 23篇 |
物理学 | 636篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 25篇 |
2018年 | 17篇 |
2017年 | 24篇 |
2016年 | 19篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 44篇 |
2012年 | 29篇 |
2011年 | 59篇 |
2010年 | 40篇 |
2009年 | 53篇 |
2008年 | 41篇 |
2007年 | 48篇 |
2006年 | 42篇 |
2005年 | 38篇 |
2004年 | 30篇 |
2003年 | 43篇 |
2002年 | 23篇 |
2001年 | 29篇 |
2000年 | 32篇 |
1999年 | 15篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 1篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有896条查询结果,搜索用时 15 毫秒
131.
基于包含辐射阻尼效应的电子运动方程,通过坐标变换,分析了圆极化和线极化超强激光在等离子体中传播时,辐射阻尼效应对电子运动的影响。结果表明:两种极化情况下,辐射阻尼效应都随等离子体密度的增大而增强;在圆极化激光中,激光强度在1023~1026 W/cm2范围(对应于不同的等离子体密度)时,辐射阻尼效应将对电子的运动产生显著的反作用,而对于线极化激光,只有当激光强度远大于极限光强时,辐射阻尼效应才对电子的运动有明显的作用。 相似文献
132.
对液体冷媒融霜系统的回液时间进行实验研究。在保温体温度-15℃工况下分别对回液时间7s、27s、25s、30s、40s、50s进行实验,记录并分析被融霜蒸发器融霜前和回液时间内压缩机吸气口的温度和压力变化,相机拍摄制冷压缩机吸气口和机身的结霜状况。实验表明:回液时间7s时,压缩机吸气过潮,回液时间在27s左右可以避免压缩机吸气过潮,确保系统安全正常的运行,大于27s被融霜蒸发器恢复制冷时间过长将影响库房温度的稳定并降低制冷系统的效率。 相似文献
133.
The plasma region under investigation is separated from the discharge region by a mesh grid. Plasma potential and electron number densities and electron temperatures under bi‐Maxwellian approximation for electron distribution function of the multi‐dipole argon plasma are measured. The cold electrons in the diffusion region are produced by local ionization. The hot electrons are the ionizing electrons behaving as Maxwellian. The electron trapping process in the discharge region is produced by potential well due to positive plasma potential with respect to the anode and by a repulsive grid. The dependence of ratios of the density of the hot to the cold electrons NE (=Neh/Nec) and hot to cold electron temperature T(=Teh/Tec) in the diffusion region on the depth of the potential well has been investigated. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
134.
E. Floriani R. Lima R. Vilela Mendes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):295-302
In this paper, we examine the effects of the
gravitational field on the dynamical evolution of the cavity-field
entropy and the creation of the Schr?dinger-cat state in the
Jaynes-Cummings model. We consider a moving two-level atom
interacting with a single mode quantized cavity-field in the
presence of a classical homogeneous gravitational field. Based on
an
su(2) algebra, as the dynamical symmetry group of the model, we derive the reduced density operator of the cavity-field
which includes the effects of the atomic motion and the gravitational field. Also, we obtain the exact solution and the approximate
solution for the system-state vector, and examine the atomic dynamics. By considering the temporal evolution of the
cavity-field entropy as well as the dynamics of the Q-function of the cavity-field we study the effects of the gravitational
field on the generation of the Schr?dinger-cat states of the cavity-field by using the Q-function,
field entropy and approximate solution for the system-state vector. The results show that the
gravitational field destroys the generation of the Schr?dinger-cat state of the cavity-field. 相似文献
135.
B. Sen B. Das P. Chatterjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):211-216
Nonlinear dust acoustic solitary waves in a dusty plasma are studied for nonzero kinematic viscosity. Sagdeev’s potential
can be obtain upto any order in ϕ. The existence of soliton solution is determined by pseudopotential approach. It is seen
that the electron inertia has a significant effect on the existence of solitary waves in presence of kinematic viscosity. 相似文献
136.
S. Mahmood N. Akhtar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):217-222
Linear and nonlinear ion acoustic waves in the presence of adiabatically heated ions in magnetized electron-positron-ion plasmas
are studied. The Sagdeev potential approach is employed to obtain the energy integral equation in such a mulitcomponent plasma
using fluid theory. It is found that electron density humps are formed in the subsonic region in magnetized electron-positron-ion
plasmas. The amplitude of electron density hump is decreased with the increase of hot ion temperature in electron-positron-ion
plasmas. However, the increase in positron concentration and obliqueness of the wave increases the amplitude of nonlinear
structure. The increase in positron concentration also reduces the width of the nonlinear structure in a magnetized multicomponent
plasma. The numerical solutions in the form of solitary pulses are also presented for different plasma cases. The results
may be applicable to astrophysical plasma situations, where magnetized electron-positron-ion plasma with hot ions can exist. 相似文献
137.
S. Kar Y. K. Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):157-165
We have investigated the bound states and resonance states of
plasma-embedded tdμ and ddμ molecular ions using accurate
correlated basis functions. The plasma effect has been taken care of by
considering the Debye shielding approach of plasma modeling which admits a
variety of plasma conditions. The density of resonance states are calculated
using the stabilization method. The ground and excited states energies, and
the S-wave resonance energies of tdμ and ddμ molecular ions
immersed in plasmas are reported for various shielding parameters, along
with the 1S and 2S threshold energies of the tμ and dμ atoms. 相似文献
138.
Sabyasachi Kar Y.K. Ho 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(3):445-452
The effect of weakly coupled hot plasma environment on the oscillator strengths of the ultraviolet and visible series and the polarizabilities of helium has been investigated using variational highly correlated wave functions within the non-relativistic framework. The Debye shielding approach that admits a variety of plasma conditions is used to simulate the plasma effects. For each shielding parameter, dipole oscillator strengths are calculated for the 1 1S-n1P (n=2, 3), 2 1S-2 1P, 2 3S-n3P (n=2, 3) and 2 1,3P-n1,3D (n=3, 4) transitions. The dipole and quadrupole polarizabilities for the ground He (1s21S) state are also reported for each screening parameter. Results obtained are useful in plasma diagnostic purposes besides several other applications. 相似文献
139.
The nonmetal-to-metal transition in dense fluid helium is discussed, which has been, in analogy to metallization of hydrogen, predicted as first-order plasma phase transition using chemical models for the equation of state and plasma composition. However, recent ab initio simulations performed for dense fluid helium indicate that this transition is continuous in the considered regime, without a density jump and latent heat as characteristic of a first-order phase transition. Implications for some astrophysical plasmas are discussed. 相似文献
140.
Luigi Creatini Teresa Cusati Giovanni Granucci Maurizio Persico 《Chemical physics》2008,347(1-3):492-502
We have run trajectory surface hopping simulations of the trans → cis photoisomerization of azobenzene, subject to a pulling force. The model mimics two situations: a trans-azobenzene derivative with bulky substituents that may not be easily displaced, and a recent experiment by Gaub’s group [T. Hugel, N.B. Holland, A. Cattani, L. Moroder, M. Seitz, H.E. Gaub, Science 296 (2002) 1103; N.B. Holland, T. Hugel, G. Neuert, A. Cattani-Scholz, C. Renner, D. Oesterhelt, L. Moroder, M. Seitz, H.E. Gaub, Macromolecules 36 (2003) 2015; G. Neuert, T. Hugel, R.R. Netz, H.E. Gaub, Macromolecules 39 (2005) 789], in which a polymer with azobenzene units was stretched in an atomic force microscope. In both cases, the shortening of the azobenzene moiety in going from the trans to the cis form is opposed by a pulling force. Our simulations show that the trans → cis photoconversion is only partially suppressed by considerably large forces (≈500 pN or more). However, the cis isomer reverts to trans in the ground state, with the help of the pulling force and using the vibrational energy that is available in the first 1–2 ps. The lowering of the quantum yields is therefore the combined result of hindering of the excited state process and of the hot ground state back reaction. 相似文献