全文获取类型
收费全文 | 568279篇 |
免费 | 5878篇 |
国内免费 | 1613篇 |
专业分类
化学 | 274172篇 |
晶体学 | 7990篇 |
力学 | 29146篇 |
综合类 | 13篇 |
数学 | 95898篇 |
物理学 | 168551篇 |
出版年
2021年 | 3762篇 |
2020年 | 4198篇 |
2019年 | 4539篇 |
2018年 | 20258篇 |
2017年 | 20529篇 |
2016年 | 16468篇 |
2015年 | 6870篇 |
2014年 | 8913篇 |
2013年 | 20558篇 |
2012年 | 21532篇 |
2011年 | 35940篇 |
2010年 | 23102篇 |
2009年 | 23366篇 |
2008年 | 30456篇 |
2007年 | 34440篇 |
2006年 | 16607篇 |
2005年 | 20757篇 |
2004年 | 17357篇 |
2003年 | 16120篇 |
2002年 | 13691篇 |
2001年 | 13766篇 |
2000年 | 10579篇 |
1999年 | 8080篇 |
1998年 | 6764篇 |
1997年 | 6465篇 |
1996年 | 6372篇 |
1995年 | 5665篇 |
1994年 | 5563篇 |
1993年 | 5358篇 |
1992年 | 5947篇 |
1991年 | 6053篇 |
1990年 | 5776篇 |
1989年 | 5593篇 |
1988年 | 5624篇 |
1987年 | 5516篇 |
1986年 | 5222篇 |
1985年 | 6703篇 |
1984年 | 6826篇 |
1983年 | 5426篇 |
1982年 | 5519篇 |
1981年 | 5496篇 |
1980年 | 5089篇 |
1979年 | 5487篇 |
1978年 | 5632篇 |
1977年 | 5445篇 |
1976年 | 5413篇 |
1975年 | 4984篇 |
1974年 | 4958篇 |
1973年 | 4989篇 |
1972年 | 3520篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
931.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
932.
933.
Jacob Schach Møller 《Annales Henri Poincare》2005,6(6):1091-1135
In this paper we analyze the bottom of the energy-momentum spectrum of the translation invariant Nelson model, describing
one electron linearly coupled to a second quantized massive scalar field. Our results are valid for all values of the coupling
constant and include an HVZ theorem, non-degeneracy of ground states, existence of isolated groundstates in dimensions 1 and
2, non-existence of ground states embedded in the bottom of the essential spectrum in dimensions 3 and 4, (i.e., at total
momenta where no isolated groundstate eigenvalue exists), and we study regularity and monotonicity properties of the bottom
of the essential spectrum, as a function of total momentum.
Communicated by Joel Feldman
submitted 04/11/04, accepted 17/02/05 相似文献
934.
935.
B. Ya. Balagurov 《Technical Physics》2003,48(8):945-951
A sequential scheme for calculating the polarizability of a pair of parallel cylinders with an arbitrary (but fairly symmetric) form is suggested. An infinite set of algebraic equations is derived for coefficients involved in an expression for the potential. The numerical solution of this set makes it possible to find the polarizability with any degree of accuracy. This method is unrelated to the cylinder shape. The electrostatic properties of the cylinders are described in terms of the multipolar polarizability matrix. 相似文献
936.
K. K. Turgunov B. Tashkhodzhaev L. V. Molchanov Kh. M. Shakhidoyatov 《Journal of Structural Chemistry》2004,45(5):912-916
The structure of bis-(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) tetrachlorocuprate (II) sesquihydrate, (C13H15N2O)2[CuCl4]·1.5H2O, was determined by single crystal X-ray diffraction. In contrast to the previously studied analogs, the compound contains crystallization water molecules.Original Russian Text Copyright © 2004 by K. K. Turgunov, B. Tashkhodzhaev, L. V. Molchanov, and Kh. M. Shakhidoyatov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 955–959, September–October, 2004. 相似文献
937.
Lígia M. Rodrigues 《Tetrahedron》2004,60(40):8929-8936
Tetrapeptides containing one of a set of four different α,α-dialkyl glycines at the C-terminus were synthesized by conventional methods in solution and their conformational behavior investigated by 1H NMR spectroscopy in connection with molecular mechanics calculations. The results were consistent with conformations stabilized by a γ-turn in the case of compounds with alkyl groups larger than methyl, while the corresponding Aib derivative did not exhibit intramolecular hydrogen bonding. 相似文献
938.
Using radical chemistry novel highly condensed heterocycles have been synthesized. The mechanism for their formation is discussed. 相似文献
939.
Mechatronic subsystems have been extensively developed in automotive applications as they increase performance compared to passive components. The Hydractive CRONE suspension based on fractional differentiation is presented as a hybrid system undergoing an infinite sequence of autonomous switchings. The modelling and operation of Hydractive CRONE suspension as a hybrid system are presented. The stability of Hydractive CRONE suspension is demonstrated using the maximum principle extended to hybrid systems. Finally, comfort mode synthesis is proposed using the third generation CRONE control system design. 相似文献
940.
In basin modelling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from an equation of state and the Gibbs equality constraints. In this article we present a novel implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods, with and without cross derivative terms between components, are based on a preconditioned Newton‐GMRES scheme for each time‐step with analytical computation of the derivatives. These new algorithms reduce significantly the numerical effort for the computation of the molar masses, and we illustrate the behavior of these methods with numerical computations. Copyright © 2004 John Wiley & Sons Ltd. 相似文献