全文获取类型
收费全文 | 812篇 |
免费 | 3篇 |
专业分类
化学 | 293篇 |
晶体学 | 11篇 |
力学 | 40篇 |
数学 | 138篇 |
物理学 | 333篇 |
出版年
2021年 | 10篇 |
2018年 | 19篇 |
2017年 | 16篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 34篇 |
2010年 | 28篇 |
2009年 | 20篇 |
2008年 | 31篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 22篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 20篇 |
2001年 | 29篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 12篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 17篇 |
1994年 | 9篇 |
1993年 | 15篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 15篇 |
1973年 | 13篇 |
1972年 | 7篇 |
1971年 | 8篇 |
1970年 | 11篇 |
1969年 | 11篇 |
1968年 | 7篇 |
1966年 | 7篇 |
排序方式: 共有815条查询结果,搜索用时 203 毫秒
51.
52.
Let G be a locally compact group, and let L1 (G) be the Banachalgebra which is the group algebra of G. We consider a varietyof Banach left L1 (G)-modules over L1 (G), and seek to determineconditions on G that determine when these modules are eitherprojective or injective or flat in the category. The answerstypically involve G being compact or discrete or amenable. Forexample, in the case where G is discrete and 1 < p < ,we find that the module p (G) is injective whenever G is amenable,and that, if it is amenable, then G is pseudo-amenable,a property very close to that of amenability. 2000 MathematicsSubject Classification 46H25, 43A20. 相似文献
53.
Theoretical predictions and experimental observations show that a weak harmonic seed beam can control the process of generating multiple quadratic solitons in periodically poled KTiOPO4 by inputting only a fundamental beam. This all-optical switching does not depend on the relative phase of the input beams, an unusual property for such coherent solitons. 相似文献
54.
The frequency-dependent conductivity sigma(xx)(omega) of 2D electrons subjected to a transverse magnetic field and smooth disorder is calculated. The interplay of Landau quantization and disorder scattering gives rise to an oscillatory structure that survives in the high-temperature limit. The relation to recent experiments on photoconductivity by Zudov et al. and Mani et al. is discussed. 相似文献
55.
A. A. Kotov L. A. Vaishnene V. G. Vovchenko Yu. A. Gavrikov V. V. Polyakov M. G. Tverskoi O. Ya. Fedorov T. Fukahori Yu. A. Chestnov A. V. Shvedchikov A. I. Shchetkovskii 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(6):809-811
The results of measuring total cross sections for proton-induced fission of natPb, 209Bi, 232Th, 233U, 235U, 238U, 237Np, and 239Pu nuclei at proton energies from 200 to 1000 MeV are reported. The measurements were carried out in steps of ≈100 MeV. Complementary fission fragments were detected in coincidence by two parallel-plate avalanche gas counters placed in the beam line on both sides of the thin target close to it. Energy and isotope dependences of the fission cross sections are analyzed. 相似文献
56.
57.
We present new data on midlatitude features of the resonance structure of the magnetic ultralow-frequency noise spectrum in
the frequency range 0.1–10 Hz, namely, the different frequency scale and frequency shift of the resonance-structure maxima
for the East-West and North-South components. Resonance spectra of the magnetic components and polarization parameter of magnetic
noise for the plane-stratified ionosphere model are numerically simulated with allowance for the inclination of the Earth's
magnetic field on the basis of the International Reference Ionosphere IRI-2001 standard. Dependence of the calculated parameters
of the resonance structure in the magnetic-component spectra on the source direction and inclination angle of the Earth's
magnetic field is explored. The calculations make it possible to explain the different behavior of resonant oscillations in
the linear-component spectra and the features of the resonance structure in the background-noise polarization parameter.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 7, pp. 575–584, July 2008. 相似文献
58.
P. S. Vergeles A. V. Govorkov A. Ya. Polyakov N. B. Smirnov E. B. Yakimov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(5):688-691
GaN films prepared by lateral overgrowth are investigated by scanning electron microscopy in the electron beam induced current (EBIC) mode. A comparison of experimental and simulated dependences of induced current on beam energy has allowed us to determine not only the diffusion length, but also the donor concentration in different areas of a film. It has been found that the donor distribution is inhomogeneous and this inhomogeneity increases under fast neutron irradiation. This is indicative of the significant influence of structural defects on the rate of radiation defect accumulation. An anomalously slow signal decay outside the Schottky barrier has been found, which can be determined by charged defects formed at the merger boundary. 相似文献
59.
A statistical approach was applied to describe the model of a homogeneous microporous adsorbent and obtain the dependences
of the thermodynamic functions on the number of molecules and the temperature for molecular aggregates in discrete micropores
over a wide region of fillings that lead to the Dubinin—Radushkevich equation. The energy nonuniformity of the adsorption
space is the fundamental property of carbon adsorbents. In the region of small fillings, the statistical approach leads to
Henry's law and the finite value of the initial differential energy of adsorption. The value of sorption corresponding to
the saturated vapor pressure decreases with increasing temperature, but the decrease is considerably less than for the density
of the corresponding liquid.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 261–265, February, 1999. 相似文献
60.
A. M. Blik A. M. Gorin S. V. Donskov V. N. Kolosov A. A. Lednev V. A. Lishin Yu. V. Mikhailov V. A. Polyakov V. D. Samoylenko A. E. Sobol V. P. Sugonyaev G. V. Khaustov 《Physics of Atomic Nuclei》2008,71(12):2124-2128
An experiment performed with the GAMS-4π spectrometer resulted in observing 235 ± 45 events of the decay η′ → 3π 0. The respective charge-exchange reaction at a momentum of 32.5 GeV/c was used as a source of η′ mesons. The decay branching ratio was found to be Br(η′ → 3π 0) = (1.8 ± 0.4) × 10?3. The slope parameter of the square of the respective matrix element in the linear approximation proved to be β = ?0.59 ± 0.18. 相似文献