全文获取类型
收费全文 | 1031篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 407篇 |
晶体学 | 15篇 |
力学 | 83篇 |
数学 | 170篇 |
物理学 | 360篇 |
出版年
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 31篇 |
2017年 | 28篇 |
2016年 | 35篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 44篇 |
2011年 | 42篇 |
2010年 | 33篇 |
2009年 | 40篇 |
2008年 | 29篇 |
2007年 | 52篇 |
2006年 | 34篇 |
2005年 | 27篇 |
2004年 | 19篇 |
2003年 | 29篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 19篇 |
1997年 | 18篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1992年 | 22篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1972年 | 8篇 |
1971年 | 13篇 |
1970年 | 9篇 |
1969年 | 9篇 |
排序方式: 共有1035条查询结果,搜索用时 15 毫秒
101.
102.
G. A. Smirnov P. B. Gordeev S. V. Nikitin G. V. Pokhvisneva T. V. Ternikova O. A. Luk’yanov 《Russian Chemical Bulletin》2016,65(11):2644-2649
Synthetic procedure to access the first representatives of a new series of 3-monosubstitued functional derivatives of 1-alkoxy-1-triazene 2-oxides, i.e., 1-alkoxy-3-(2-hydroxyethyl)- and 1-alkoxy-3-(2-acetoxyethyl)-1-triazene 2-oxides, were elaborated. 1-Alkoxy-3,3-bis(2-hydroxyethyl)-1-triazene 2-oxides were used to derive 3-(2-acetoxyethyl)-, 3-(2-bromoethyl)- and 3-(2-cyanoethyl)substituted 1-alkoxy-3-(2-acetoxyethyl)-1-triazene 2-oxides. 相似文献
103.
N. V. Nikitin 《Fluid Dynamics》2003,38(6):854-861
Turbulent flow of an incompressible fluid in a plane channel with parallel walls is considered. The three-dimensional time-dependent Navier-Stokes equations are solved numerically using the spectral finite-difference method. An artificial force which completely suppresses lateral oscillations of the velocity is introduced in the near-wall zone (10 % of the channel half-width in the neighborhood of each wall). Thus, the three-dimensional flow zone, in which turbulent oscillations can develop, is separated from the wall by a fluid layer. It is found that the elimination of three-dimensionality in the neighborhood of the walls leads to a significant reduction in the drag. However, complete laminarization does not occur. The flow in the stream core remains turbulent and can be interpreted as a turbulent flow in a channel with walls located on the boundary of the two-dimensional layer and traveling at the local mean-flow velocity. The oscillations developing inside the two-dimensional layer, which have significant amplitude, distort the flow only in the adjacent zone. Beyond this zone the distributions of the mean characteristics and the structure of instantaneous fields completely correspond to ordinary turbulent flow in a channel with rigid walls. The results obtained confirm the hypothesis of the unimportance of the no-slip boundary conditions for the fluctuating velocity component in the mechanism of onset and self-maintenance of turbulence in wall flows. 相似文献
104.
Summary The bending of a finite-length beam that lies on a rigid, rough, flat foundation and interacts with it in accordance to the
dry friction law is considered. Loading by bending moments applied at the ends of the beam is studied in detail. The problem
is found to be a self-similar one. For small moments, the central part of the beam remains undeflected, and the problem reduces
to the solution of an infinite system of algebraic equations. Large moments deflect the entire length of the beam, and the
problem partly loses its self-similarity. In this case, the problem reduces to the solution of a successively decreasing number
of ordinary differential equations along with some algebraical equations. The solution for the latter case provides initial
conditions for the former one. This permits to obtain a solution for any value of the moment.
Received 5 November 1996; accepted for publication 27 January 1997 相似文献
105.
V. M. Buznik L. N. Ignat’eva V. G. Kuryavyi E. B. Merkulov N. N. Savchenko A. Yu. Ustinov A. B. Slobodyuk L. N. Nikitin 《Polymer Science Series A》2010,52(12):1334-1343
Microsized spherical core-shell particles consisting of hydrocarbon cores encapsulated into fluoropolymer shells are obtained
in supercritical carbon dioxide. Paraffins serve as a core material, while the polymer shell is formed from ultradispersed
polytetrafluoroethylene. The morphology and molecular structure in the bulk and on the surface of the particles and the influence
of conditions of particle formation on the shell thickness and the thermal properties of the materials are studied. The materials
are composites comprised of paraffin cores coated with shells of loosened globular fluoropolymer particles with sizes of 0.2–1.7
μm. The shells is built of low- and high-molecular-mass fractions consisting of CF3(CF2)nCF3 molecular chains with different lengths. The shell thickness is governed by preparation conditions, exposure time, and the
percentage of the polymer in the initial dispersion. 相似文献
106.
107.
A. G. Nikitin 《Ukrainian Mathematical Journal》1991,43(10):1287-1296
A complete set of symmetry operators of arbitrary finite order admitted by the Dirac equation is found. The algebraic structure of this set is investigated and subsets of symmetry operators that form bases of Lie algebras and superalgebras are isolated.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 10, pp. 1388–1398, October, 1991. 相似文献
108.
A. A. Dutov D. A. Nikitin Z. Ts. Rinchinov P. P. Tereshkov P. P. Tsydendambaev A. A. Fedotova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(3):421-423
A HPLC method is proposed for determining neopterin in biological liquids. The method was realized using a standard chromatographic instrumentation. Neopterin was isolated from blood serum and urine by solid-phase extraction on cartridges containing 30 mg of supercrosslinked polystyrene. The separation was carried out on an Irica chromatograph (Japan) equipped with means of UV (350 nm) and fluorimetric (es350-em430 nm) detection. The degree of extraction was 96–113%, and the sensitivity of UV and fluorimetric detection was 0.1 and ~0.03 ng, respectively (at signal-to-noise ratio 3). It is shown that the method is suitable for use in routine clinical analysis of neopterin in biological liquids. 相似文献
109.
A.G. Nikitin 《Journal of Mathematical Analysis and Applications》2007,332(1):666-690
Group classification of systems of two coupled non-linear reaction-diffusion equation with a diagonal diffusion matrix is carried out. Symmetries of diffusion systems with singular diffusion matrix and additional first order derivative terms are described. 相似文献
110.
Corrections accounting for the effect of the differences in p-electron energies on the electric field gradient are suggested and justified in the framework of Townes-Dailey theory. MNDO calculations of 31 chloro-containing molecules with full geometry optimization were used to evaluate the35Cl NQR frequencies. The correlational relationships between experimental and calculated NQR frequencies are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 38–42, January, 1995.This work was supported by the Russian Foundation for Basic Research (Project No. 93-03-5201). 相似文献