全文获取类型
收费全文 | 2972篇 |
免费 | 58篇 |
国内免费 | 21篇 |
专业分类
化学 | 1606篇 |
晶体学 | 27篇 |
力学 | 102篇 |
数学 | 401篇 |
物理学 | 915篇 |
出版年
2023年 | 13篇 |
2022年 | 48篇 |
2021年 | 41篇 |
2020年 | 58篇 |
2019年 | 67篇 |
2018年 | 69篇 |
2017年 | 55篇 |
2016年 | 99篇 |
2015年 | 63篇 |
2014年 | 79篇 |
2013年 | 176篇 |
2012年 | 159篇 |
2011年 | 162篇 |
2010年 | 128篇 |
2009年 | 97篇 |
2008年 | 168篇 |
2007年 | 167篇 |
2006年 | 169篇 |
2005年 | 149篇 |
2004年 | 117篇 |
2003年 | 89篇 |
2002年 | 110篇 |
2001年 | 63篇 |
2000年 | 39篇 |
1999年 | 36篇 |
1998年 | 38篇 |
1997年 | 43篇 |
1996年 | 43篇 |
1995年 | 40篇 |
1994年 | 28篇 |
1993年 | 17篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1986年 | 12篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1975年 | 19篇 |
1973年 | 15篇 |
1972年 | 17篇 |
1971年 | 17篇 |
1969年 | 19篇 |
排序方式: 共有3051条查询结果,搜索用时 15 毫秒
1.
Crystallography Reports - Some questions related to the establishment, development, and prospects of physical studies using inelastic thermal-neutron scattering are briefly reviewed. The directions... 相似文献
2.
V. A. Alekseev 《Optics and Spectroscopy》2004,96(4):492-496
The absorption spectra of Xe + CF4 and Kr + CF4 mixtures in the vacuum ultraviolet region are presented. A considerable broadening of the short-wavelength wings of the atomic absorption lines is explained by a repulsive character of the Rg*-CF4 interaction potential. This repulsive character is also considered to be the most probable reason for the anomalously small cross sections of the quenching of electronically excited atoms of rare gases by CF4 molecules. The influence of CF4 on the emission rate of the trapped resonance radiation of Xe from the cell is discussed. 相似文献
3.
Anatoliy Samoilenko Manuel Pinto Sergei Trofimchuk 《Proceedings of the American Mathematical Society》2005,133(1):145-154
We apply the Krylov and Bogolyubov asymptotic integration procedure to asymptotically autonomous systems. First, we consider linear systems with quasi-periodic coefficient matrix multiplied by a scalar factor vanishing at infinity. Next, we study the asymptotically autonomous Van-der-Pol oscillator.
4.
5.
Jaedong Cho John Blackwell Sergei N. Chvalun Morton Litt Yuan Wang 《Journal of Polymer Science.Polymer Physics》2004,42(13):2576-2585
As‐cast films of poly(2,5‐benzimidazole) exhibit uniplanar orientation in which the planes of the aromatic rings lie parallel to the film surface. Upon doping with phosphoric acid, the original crystalline order is lost, but the doped film can be stretched to produce films with uniaxial orientation. After thermal annealing at 540 °C, nine Bragg reflections are resolved in the fiber diagram, and these are indexed by an orthorhombic unit cell with the dimensions a = 18.1 Å, b = 3.5 Å, and c = 11.4 Å, containing four monomer units of two chains. The absence of odd‐order 00l reflections points to a 21 chain conformation, which is probably planar so that the aromatic units can be stacked along the b axis. The water and phosphoric acid contents of the crystalline structure cannot be determined exactly because of the presence of extensive amorphous regions that probably have different solvation. The best agreement between the observed and calculated intensities is for an idealized structure containing two phosphoric acids and two water molecules per unit cell. However, the phosphoric acid is probably present mainly in the form of pyrophosphoric acid and its higher oligomers. In addition, the X‐ray data are consistent with a more disordered structure containing chains with random (up and down) polarity and a lack of c‐axis registry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2576–2585, 2004 相似文献
6.
N. I. Alekseev V. B. Kaplan A. M. Martsinovskii I. I. Stolyarov 《Technical Physics》1997,42(6):599-605
Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation
are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over
a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is
noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold
of ∼2×10−2 Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional
nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles,
and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged
by the quenching pulse and and the current is blocked.
Zh. Tekh. Fiz. 67, 15–21 (June 1997) 相似文献
7.
8.
F. Klappenberger K. N. Alekseev K. F. Renk R. Scheuerer E. Schomburg S. J. Allen G. R. Ramian J. S. S. Scott A. Kovsh V. Ustinov A. Zhukov 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,39(4):483-489
We report an experimental study indicating ultrafast creation and annihilation of space-charge domains in a semiconductor superlattice under the action of a THz field. Our experiment was performed for an InGaAs/InAlAs superlattice with the conduction electrons undergoing miniband transport. We applied to a superlattice a dc bias that was slightly smaller than a critical bias necessary for the formation of space-charge domains caused by a static negative differential conductivity. Additionally subjecting the superlattice to a strong THz field, resulted in a dc transport governed by the formation of domains if the frequency of the field was smaller than an upper frequency limit (~3 THz). From this frequency limit for the creation and annihilation of domains we determined the characteristic time of the domain buildup. Our analysis shows that the buildup time of domains in a wide miniband and heavily doped superlattice is limited by the relaxation time due to scattering of the miniband electrons at polar optic phonons. Our results are of importance for both an understanding of ultrafast dynamics of pattern formation in nanostructures and the development of THz electronic devices.Received: 25 March 2004, Published online: 23 July 2004PACS:
72.20.Ht High-field and nonlinear effects - 72.30. + q High-frequency effects; plasma effects - 73.21.Cd SuperlatticesK.N. Alekseev: Permanent address: Department of Physical Sciences, P.O. Box 3000, University of Oulu FIN-90014, Finland. 相似文献
9.
A. I. Alekseev 《Few-Body Systems》2006,40(1-2):57-70
Based on a study of the analytic running coupling obtained from the standard perturbation-theory results up to four-loop order,
the QCD “synthetic” running coupling αsyn is built. In so doing the perturbative time-like discontinuity is preserved and nonperturbative contributions not only remove
the nonphysical singularities of the perturbation theory in the infrared region but also decrease rapidly in the ultraviolet
region. In the framework of the approach, on the one hand, the running coupling is enhanced at zero and, on the other hand,
the dynamical gluon mass m
g
arises. Fixing the parameters which characterize the infrared enhancement corresponding to the string tension σ and normalization,
say, at M
τ completely define the synthetic running coupling. In this case the dynamical gluon mass appears to be fixed and the higher-loop
stabilization property of m
g
is observed. For σ = (0.42 GeV)2 and αsyn(M
τ
2) = 0.33 ± 0.01 it is obtained that m
g
= 530 ± 80 MeV.
Deceased 相似文献
10.