全文获取类型
收费全文 | 396509篇 |
免费 | 3141篇 |
国内免费 | 1196篇 |
专业分类
化学 | 201361篇 |
晶体学 | 6579篇 |
力学 | 19520篇 |
综合类 | 11篇 |
数学 | 45171篇 |
物理学 | 128204篇 |
出版年
2020年 | 3454篇 |
2019年 | 4111篇 |
2018年 | 5650篇 |
2017年 | 5593篇 |
2016年 | 7799篇 |
2015年 | 4329篇 |
2014年 | 7446篇 |
2013年 | 17163篇 |
2012年 | 13066篇 |
2011年 | 15837篇 |
2010年 | 11850篇 |
2009年 | 11956篇 |
2008年 | 14822篇 |
2007年 | 14742篇 |
2006年 | 13516篇 |
2005年 | 12054篇 |
2004年 | 11437篇 |
2003年 | 10233篇 |
2002年 | 10131篇 |
2001年 | 11507篇 |
2000年 | 8718篇 |
1999年 | 6742篇 |
1998年 | 5685篇 |
1997年 | 5698篇 |
1996年 | 5346篇 |
1995年 | 4821篇 |
1994年 | 4854篇 |
1993年 | 4809篇 |
1992年 | 5221篇 |
1991年 | 5421篇 |
1990年 | 5140篇 |
1989年 | 5158篇 |
1988年 | 5108篇 |
1987年 | 4987篇 |
1986年 | 4776篇 |
1985年 | 6286篇 |
1984年 | 6551篇 |
1983年 | 5305篇 |
1982年 | 5524篇 |
1981年 | 5403篇 |
1980年 | 5163篇 |
1979年 | 5549篇 |
1978年 | 5586篇 |
1977年 | 5660篇 |
1976年 | 5758篇 |
1975年 | 5286篇 |
1974年 | 5255篇 |
1973年 | 5386篇 |
1972年 | 3934篇 |
1971年 | 3425篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
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
132.
The surface of hydrogen-sensitive GaAs Schottky diodes is modified by nonpolishing etching and by producing quantum wells and quantum dots in the space-charge region of the semiconductor. The sensitivity to hydrogen is found to increase by a factor of 8–37 after the etching and by two or three orders of magnitude after the introduction of quantum wells and dots. It is shown that the increased sensitivity is associated with the lowering of the barrier at the Pd/GaAs interface, the retardation of hydrogen diffusion into GaAs due to the presence of strained quantum-size layers, and an increase in the recombination current. The presence of the recombination component is supported by luminescence from the quantum wells and quantum dots, as well as from the GaAs substrate. The etch composition is shown to be a decisive factor in raising the sensitivity. 相似文献
133.
For ϕ a δ-subharmonic function, sharp results are obtained that connectA(r, ϕ), B(r, ϕ) andT(r, ϕ), whereA(r, ϕ)=inf|z|=r
ϕ(z),B(r, ϕ)=sup|z|=r
ϕ(z), andT(r, ϕ) is the Nevanlinna characteristics. 相似文献
134.
135.
136.
I. P. Kayumov 《Mathematical Notes》2005,78(3-4):498-502
In this paper, we prove Brennan's conjecture for conformal mappings f of the disk {z : | z| < 1} assuming that the Taylor coefficients of the function log(zf′(z)/f(z)) at zero are nonnegative. We also obtain inequalities for the integral means over the circle |z| = r of the squared modulus of the function zf′(z)/f(z). 相似文献
137.
The occurrence of two noninteracting forms of Pd-porphin in the ground electronic state in a wide number of Shpolskii matrices maintained at liquid helium temperature was observed with the help of the finestructure phosphorescence spectra of these systems. The ratio between these forms can be varied in wide limits by choosing a particular matrix, which indicates that the matrix plays a significant role in the conformation formation of the tetrapyrrole macrocycle. Based on comparison both with the resonance Raman spectra and with the results of investigations of metal complexes of porphin by the selective spectroscopy methods, the shortwavelength spectral form has been shown to correspond to the planar molecular structure, whereas the longwavelength form has been attributed to a nonplanar molecular structure with the distortion of the porphin macrocycle of the saddle type. The results obtained indicate that the methods of fine structure spectroscopy make it possible to efficiently study distorted molecular structures stabilized in solid matrices at low temperatures. 相似文献
138.
C. Czeranowsky V. M. Baev G. Huber P. A. Khandokhin Ya. I. Khanin I. V. Koryukin E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):723-728
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser. 相似文献
139.
A brief account of applications of polarized inelastic neutron scattering in condensed matter research is given. We show that
full polarization analysis is the only tool allowing to discriminate unambiguously between different magnetic modes in various
magnetic materials. We show by means of recent results in the Heisenberg ferromagnet EuS that the effects of dipolar interactions
can be studied on a microscopic scale. Moreover, we have found for the first time indications for the divergence of the longitudinal
fluctuations belowT
c. In the itinerant antiferromagnet chromium we demonstrate that the dynamics of the longitudinal and transverse excitations
are very different, resolving a long standing puzzle concerning the slope of their dispersion. Finally, we show that a measurement
of the polarization-dependent part of the cross section of non-centrosymmetric MnSi proves directly that the chirality of
the magnetic fluctuations is left-handed. 相似文献
140.
R. Hefelmann P. Mann A. Aignan F. Filsinger und H. Amsel 《Fresenius' Journal of Analytical Chemistry》1902,41(1):66-68
Ohne Zusammenfassung 相似文献