全文获取类型
收费全文 | 854篇 |
免费 | 3篇 |
专业分类
化学 | 302篇 |
晶体学 | 7篇 |
力学 | 52篇 |
数学 | 103篇 |
物理学 | 393篇 |
出版年
2022年 | 13篇 |
2021年 | 28篇 |
2020年 | 16篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 37篇 |
2016年 | 50篇 |
2015年 | 16篇 |
2014年 | 30篇 |
2013年 | 32篇 |
2012年 | 27篇 |
2011年 | 26篇 |
2010年 | 32篇 |
2009年 | 31篇 |
2008年 | 29篇 |
2007年 | 24篇 |
2006年 | 27篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 22篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 17篇 |
1994年 | 7篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 18篇 |
1975年 | 16篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1972年 | 9篇 |
1971年 | 10篇 |
1970年 | 14篇 |
1969年 | 5篇 |
1968年 | 6篇 |
1967年 | 12篇 |
排序方式: 共有857条查询结果,搜索用时 15 毫秒
831.
V. L. Gurtovoi S. V. Dubonos A. V. Nikulov N. N. Osipov V. A. Tulin 《Journal of Experimental and Theoretical Physics》2007,105(6):1157-1173
The obtained periodic magnetic-field dependences I c+(Φ/Φ0) and I c?(Φ/Φ0) of the critical current measured in opposite directions on asymmetric superconducting aluminum rings has made it possible to explain previously observed quantum oscillations of dc voltage as a result of alternating current rectification. It was found that a higher rectification efficiency of both single rings and ring systems is caused by hysteresis of the current-voltage characteristics. The asymmetry of current-voltage characteristics providing the rectification effect is due to the relative shifts of the magnetic dependences I c?(Φ/Φ0) = I c+(Φ/Φ0 + Δ?) of the critical current measured in opposite directions. This shift means that the position of I c+(Φ/Φ0) and I c?(Φ/Φ0) minima does not correspond to n + 0.5 magnetic flux Φ quanta, which is in direct contradiction to measured Little-Parks resistance oscillations. Despite this contradiction, the amplitude I c, an(Φ/Φ0) = I c+(Φ/Φ0) ? I c?(Φ/Φ0) of critical current anisotropy oscillations and its variations with temperature correspond to the expected amplitude of persistent current oscillations and its variations with temperature. 相似文献
832.
We report on the mechanism of burst generation by populations of intrinsically spiking neurons, when a certain threshold in coupling strength is exceeded. These ensembles synchronize at relatively low coupling strength and lose synchronization at stronger coupling via spatiotemporal intermittency. The latter transition triggers fast repetitive spiking, which results in synchronized bursting. We present evidence that this mechanism is generic for various network topologies from regular to small-world and scale-free ones, different types of coupling and neuronal model. 相似文献
833.
Electromagnetic emission induced by the injection of spin-polarized electrons from a ferromagnetic material into an n-InSb semiconductor has been obtained. Analysis of the conditions of the excitation of emission and its characteristics indicates that electromagnetic emission is of laser origin. 相似文献
834.
I. A. Artyukov A. V. Vinogradov E. V. Zharikov K. S. Zaramenskikh M. V. Osipov V. N. Puzyrev A. N. Starodub A. A. Fronya M. L. Chernodub O. F. Yakushev 《Bulletin of the Lebedev Physics Institute》2011,38(6):172-176
Experimental results on the spatial distribution of X-ray radiation of the plasma generated by nanosecond laser radiation
incident on a target made of carbon nanotubes are presented and compared with the results obtained for solid-state magnesium
targets. 相似文献
835.
J. Moreira A. A. Osipov B. Hiller A. H. Blin J. Providencia 《Indian Journal of Physics》2011,85(6):813-818
A NJL Lagrangian extended to six [1–3] and eight quark interactions [4] is applied to study temperature effects [5] (SU(3)
flavor limit, massless case), and [6] (realistic massive case). The transition temperature can be considerably reduced as
compared to the standard approach, in accordance with recent lattice calculations [7]. The mesonic spectra built on the spontaneously
broken vacuum induced by the’ t Hooft interaction strength, as opposed to the commonly considered case driven by the four-quark
coupling, undergoes a rapid crossover to the unbroken phase, with a slope and at a temperature which is regulated by the strength
of the OZI violating eight-quark interactions. This strength can be adjusted in consonance with the four-quark coupling and
leaves the spectra unchanged, except for the sigma meson mass, which decreases. A first order transition behavior is also
a possible solution within the present approach. 相似文献
836.
The problem of conservation of magnitudes is considered for a vortex in a relaxing compressible medium. Heat release due to
the relaxation of a nonequilibrium medium leads to the propagation of compression waves, which remove material. Traditional
integrals of motion are inapplicable in this case. We pro-pose the concept of integral quantity, which is conserved with an
arbitrary degree of accuracy despite the fact that waves cross the boundary of the integration domain. Based on this concept,
a broad class of conservation laws is derived for axisymmetric disturbances of columnar vortices, including conservation of
the circulation and total angular momentum of the vortex. For nonaxisymmetric disturbances, it is shown that the total angular
momentum and properly defined energy integral are conserved. Numerical verification of the derived conservation laws is performed
and the perspectives for using these conservation laws in numerical simulations are discussed. 相似文献
837.
Palladium-containing carboxylated carbon nanofibers were studied as catalysts for hydrogenation of double bond >C=C< in olefins, unsaturated alcohols, and acids, as well as for hydrogenation of nitroarenes. The developed catalyst is 7 times more efficient than the industrial analog (Pd/C). 相似文献
838.
D. V. Osipov V. A. Osyanin Yu. N. Klimochkin 《Russian Journal of Organic Chemistry》2013,49(3):398-402
3-Amino-1H-benzo[f]chromene-2-carbonitriles were synthesized by non-catalytic reaction from Mannich bases of the naphthalene series and malononitrile. Reactive 1-benzylidene(or methylidene)naphthalen-2(1H)-ones were presumed as intermediate products. 相似文献
839.
V. V. Osipov V. I. Solomonov A. V. Spirina E. G. Vovkotrub V. N. Strekalovskii 《Optics and Spectroscopy》2014,116(6):946-955
We have studied Raman scattering in yttria nanopowders and ceramics that was excited by radiation at wavelengths of 514.5 and 632.8 nm. We show that, in undoped nanopowders and cubic phase of doped yttria ceramics, only the Raman scattering by phonons is observed, with no other Raman scattering centers having been revealed. In nanopowders of the monoclinic phase, we have observed an additional Raman line with a Raman shift of 1093 ± 4 cm?1. If all the objects under investigation are excited by the radiation at a wavelength of 514.5 nm, their spectra exhibit four series of photoluminescence lines, two of which (at λ = 521–523 and 538–564 nm) are emitted by Er3+ ions, “impurity” dopants, while the other two lines (at λ = 607–635 and 644–684 nm) are emitted by intrinsic centers. Under excitation by the radiation at a wavelength of 632.8 nm, only a series of bands at λ = 644–684 nm is emitted. In addition to these photoluminescence bands, neodymium-doped ceramics show photoluminescence bands of Nd3+ ions. We have shown that intrinsic luminescence centers, which occur in all the examined specimens, are capable of acting as acceptors with respect to neodymium ions excited to the upper laser level. 相似文献
840.