全文获取类型
收费全文 | 452篇 |
免费 | 3篇 |
专业分类
化学 | 204篇 |
晶体学 | 2篇 |
力学 | 37篇 |
数学 | 73篇 |
物理学 | 139篇 |
出版年
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 40篇 |
2012年 | 16篇 |
2011年 | 8篇 |
2010年 | 17篇 |
2009年 | 27篇 |
2008年 | 16篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1984年 | 3篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有455条查询结果,搜索用时 0 毫秒
1.
In a two-dimensional array of magnetic moments with planar magnetization and relatively weak anisotropy in the basal plane, a stepwise phase transition is induced by an external magnetic field parallel to the easy axis of the system. This transition is similar to the spin flop phase transition in weakly anisotropic Heisenberg antiferromagnets with the significant difference that it is accompanied by the rearrangement of the sublattice structure of the magnet; i.e., it can be interpreted as a topological transition. The transition should manifest itself for arrays of submicron magnetic particles (magnetic dots) on nonmagnetic substrates, which have recently become the object of intensive research. 相似文献
2.
A special model of a rarefied hard-sphere gas is considered. The hard-sphere particles undergo absolutely elastic collisions. It is assumed that particles can collide only if their nonzero velocities are orthogonal to each other. The model makes it possible to proceed from the Boltzmann equation to the Smoluchowski coagulation equation, where coagulation means that the kinetic energies of the colliding particles are added. A Monte Carlo scheme for simulation of the phenomenon is described, and the convergence of the simulation algorithm is proved. The convergence of numerical results to exact solutions of the Smoluchowski equation and to finite-difference solutions is tested. 相似文献
3.
O. P. Galkin V. S. Gostev O. E. Popov L. V. Shvachko R. F. Shvachko 《Acoustical Physics》2006,52(3):252-258
The experimental data on the sound field structure, which were obtained by emitting a continuous pseudonoise signal (a midfrequency of 3.2 kHz) in a two-channel oceanic waveguide, are compared with the calculations performed by the wave program with allowance for the fine structure of the sound speed inhomogeneities. A considerable increase in the intensity of the sound field with a definite angular spectrum is observed in the upper channel in the first shadow zone, and, in the experiment, the increase begins nearer to the sound source than predicted by the wave and ray calculations for a smooth sound speed profile. These features of the field structure are explained by the illumination of the shadow zone by the regular scattering of signals from highly anisotropic fine-structure inhomogeneities of the sound speed profile, which are clearly pronounced in the region of the given oceanic experiment. 相似文献
4.
The results of measuring the vertical variability of sound fields are presented for a coastal wedge off the Pacific shelf of the Kamchatka peninsula. It is shown that the vertical radius of sound field correlation can reach ~30 m for frequencies within 600–800 Hz. The scatter of the specific parameters of the variability is in rather wide limits depending on the location of a vertical chain of receiving hydrophones, the hydrological conditions, the azimuth angle of the sound source, and the relief and bottom structure of the coastal wedge. 相似文献
5.
We study different moment characteristics of (mostly discrete) distributions: general, central, binomial, and factorial moments,
and also ordinary and factorial semi-invariants. We establish the relations that connect various kinds of “moments” of arbitrary
order, and we derive recursion formulas.
Translated fromMetody Matematicheskogo Modelirovaniya, pp. 34–41, 1998. 相似文献
6.
A. A. Sobanov A. V. Zolotukhin I. V. Galkina V. I. Galkin R. A. Cherkasov 《Russian Journal of General Chemistry》2006,76(3):421-429
A complex spectral (UV, IR, and 31P NMR), preparative, and kinetic investigation of the mechanism of the noncatalytic variant of the Pudovik reaction in the series of imines was carried out. The reaction proceeds through a four-center cyclic transition state. The transition state is highly labile, which determines its high sensitivity to the structure of the reagents, the nature of the solvent and catalyst, and some other factors. The necessary condition for the hydrophosphorylation of imines to occur is the participation of proton-donor reagents and acidic admixtures, specifically hydrolysis products of dialkyl hydrogen phosphites, such as monoalkyl dihydrogen phosphates and phosphorous acid, which act as acid catalysts. When the starting reagents are thoroughly purified and no such catalysts are present, the Pudovik reaction fails to occur in the imine series. 相似文献
7.
8.
A. G. Korepin P. V. Galkin G. V. Lagodzinskaya L. T. Eremenko 《Russian Chemical Bulletin》1991,40(7):1502-1503
The direct fluorination of Mannich bases containing nitro groups in one or two alkyl substituants in the position relative to the amine nitrogen gives previously unreported vicinal N,C-difluorides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1692–1693, July, 1991. 相似文献
9.
R. A. Cherkasov V. I. Galkin N. G. Khusainova O. A. Mostovaya A. R. Garifzyanov G. Kh. Nuriazdanova N. S. Krasnova E. A. Berdnikov 《Russian Journal of Organic Chemistry》2005,41(10):1481-1484
New and previously known β-aminoethylphosphonates were synthesized by addition of primary and secondary amines to vinylphosphonates, and their IR and NMR spectra were examined. Diethyl 2-diethylaminoethylphosphonate and diethyl 2-morpholinoethylphosphonate were found to be stronger bases than the corresponding aminomethylphosphonates, but all these are weaker bases than their precursors, nonphosphorylated amines. Distribution constants of β-aminophosphonates between water and some organic solvents were determined and compared with those of their α-amino homologs. 相似文献
10.
N. I. Golovina R. F. Trofimova L. O. Atovmyan A. G. Korepin P. V. Galkin G. V. Lagodzinskaya M. V. Loginova L. T. Eremenko 《Russian Chemical Bulletin》1994,43(3):398-401
The reaction of -fluorosubstituted polynitroalkylaldimines with HCl results in replacement of the fluorine atom by a chlorine atom. The hitherto unknown -chlorosubstituted polynitroalkylaldimines have been obtained, and their X-ray structural investigation has been performed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 440–443, March, 1994. 相似文献