全文获取类型
收费全文 | 600153篇 |
免费 | 4472篇 |
国内免费 | 1650篇 |
专业分类
化学 | 290416篇 |
晶体学 | 8307篇 |
力学 | 32275篇 |
综合类 | 17篇 |
数学 | 98022篇 |
物理学 | 177238篇 |
出版年
2021年 | 5035篇 |
2020年 | 5478篇 |
2019年 | 6221篇 |
2018年 | 18177篇 |
2017年 | 18062篇 |
2016年 | 17265篇 |
2015年 | 6936篇 |
2014年 | 10686篇 |
2013年 | 23719篇 |
2012年 | 21753篇 |
2011年 | 31407篇 |
2010年 | 21594篇 |
2009年 | 21881篇 |
2008年 | 26672篇 |
2007年 | 28496篇 |
2006年 | 18774篇 |
2005年 | 17770篇 |
2004年 | 16837篇 |
2003年 | 15787篇 |
2002年 | 14768篇 |
2001年 | 14921篇 |
2000年 | 11581篇 |
1999年 | 8870篇 |
1998年 | 7749篇 |
1997年 | 7583篇 |
1996年 | 7107篇 |
1995年 | 6367篇 |
1994年 | 6334篇 |
1993年 | 6107篇 |
1992年 | 6425篇 |
1991年 | 6923篇 |
1990年 | 6625篇 |
1989年 | 6541篇 |
1988年 | 6377篇 |
1987年 | 6184篇 |
1986年 | 5926篇 |
1985年 | 7451篇 |
1984年 | 7810篇 |
1983年 | 6567篇 |
1982年 | 6857篇 |
1981年 | 6364篇 |
1980年 | 6047篇 |
1979年 | 6546篇 |
1978年 | 6774篇 |
1977年 | 6647篇 |
1976年 | 6604篇 |
1975年 | 6316篇 |
1974年 | 6141篇 |
1973年 | 6449篇 |
1972年 | 4723篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
A group representation of radiation propagation in an anisotropic medium is developed. The system of wave equations for electromagnetic potentials, obtained from the Maxwell equations with account for the constitutive equations, has been factorized. It is shown that the linear differential operator of the factorized system is orthogonal in transparent crystals and unitary in gyrotropic ones and is represented through the momentum operator. On the basis of the commutation relations for the components of this operator, the eigenvalue problem has been solved and the expression for the change in the radiant energy in the crystal in the form of spherical waves has been obtained. The dependences of the ray and phase velocities and the polarization vectors of waves on the birefringence anisotropy and gyrotropy as well as on the angular momentum, displacement current, and bound charge determining them have been analyzed. It has been established that in the general case of gyrotropic crystals where the nonreciprocity phenomenon takes place and in magnetoelectrics Maxwell equations are represented in a form similar to the Dirac equations and the electromagnetic radiation is correctly described by means of bispinors and is quantized as fermions. 相似文献
182.
The influence of the well width fluctuations on the dependence of the binding energy of excitonic complexes in quantum wells is studied by using the path-integral Monte-Carlo technique. The results are compared with available experimental data and a good agreement is found.Postdoctoral researcher of FWO-Vlaanderen 相似文献
183.
A switching of the S-type in the 20–200 μm thick polycrystalline n-CdTe:In layers with resistance of 103–106 Ω·cm is studied. The electric instability in the layers is found to be due to the electron-thermal breakdown mechanism. The
dependence of the switching threshold parameters on the intensity of exposure can be used for fabrication of infrared-radiation
controlled electric switches on the basis of n-CdTe:In layers.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 28–30, June, 2005. 相似文献
184.
185.
Results of studying electro-optic size effects and nonlinear electro-optic effects in ferroelectric PLZT ceramics are presented. It is established that the presence of electro-optic size effects makes microvolume samples of PLZT ceramics promising for designing efficient modulating devices. 相似文献
186.
M. Ya. Amusia N. A. Cherepkov L. V. Chernysheva 《Journal of Experimental and Theoretical Physics》2003,97(1):34-41
The results of calculations of the elastic scattering cross section of positrons on noble gas and alkali atoms are presented. The calculations are performed within the one-electron Hartree-Fock approximation with multielectron correlations in the so-called random phase approximation with exchange taken into account. Virtual positronium formation is taken into account and proved to be very important. Arguments are presented that the positron polarization potential is repulsive for alkali atoms. The results obtained are in a reasonable agreement with experiment and with some previously reported calculations. 相似文献
187.
H.L. Xu A. Persson S. Svanberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):233-236
New radiative lifetime measurements based on time-resolved laser-induced fluorescence techniques are reported for 18 even-parity
levels belonging to the 4f5d26p and 4f
25d
2 configurations of Ce I and 6 even-parity levels belonging to the 5d26s, 4f5d6p, and 4f6s6p configurations of Ce II. Free neutral and singly ionized cerium atoms were produced by laser ablation. The Ce I and Ce II
levels range in energy from 26 545 to 29 102 cm-1, and 42 573 to 48 152 cm-1, respectively.
Received 25 September 2002 Published online 4 March 2003 相似文献
188.
R. Pizzoferrato L. Lagonigro T. Ziller A. Di Carlo R. Paolesse F. Mandoj A. Ricci C. Lo Sterzo 《Chemical physics》2004,300(1-3):217-225
We study the infrared emission at 1.54 μm of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host π-conjugate polymers of type poly(arylene–ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 μm φIR=4×10−4 is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acac with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Förster model for polymeric donors. The experimental values of the critical radius R0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. 相似文献
189.
M. V. Zyubin I. A. Rudnev V. A. Kashurnikov 《Journal of Experimental and Theoretical Physics》2003,96(6):1065-1077
A system of Abrikosov vortices in a quasi-two-dimensional HTSC plate is considered for various periodic lattices of pinning centers. The magnetization and equilibrium configurations of the vortex density for various values of external magnetic field and temperature are calculated using the Monte Carlo method. It is found that the interaction of the vortex system with the periodic lattice of pinning centers leads to the formation of various ordered vortex states through which the vortex system passes upon an increase or a decrease in the magnetic field. It is shown that ordered vortex states, as well as magnetic field screening processes, are responsible for the emergence of clearly manifested peaks on the magnetization curves. Extended pinning centers and the effect of multiple trapping of vortices on the behavior of magnetization are considered. Melting and crystallization of the vortex system under the periodic pinning conditions are investigated. It is found that the vortex system can crystallize upon heating in the case of periodic pinning. 相似文献
190.