全文获取类型
收费全文 | 286203篇 |
免费 | 2690篇 |
国内免费 | 845篇 |
专业分类
化学 | 136315篇 |
晶体学 | 3771篇 |
力学 | 14819篇 |
综合类 | 7篇 |
数学 | 44840篇 |
物理学 | 89986篇 |
出版年
2021年 | 1103篇 |
2020年 | 1259篇 |
2019年 | 1285篇 |
2018年 | 10531篇 |
2017年 | 11498篇 |
2016年 | 6774篇 |
2015年 | 3119篇 |
2014年 | 2884篇 |
2013年 | 8465篇 |
2012年 | 11359篇 |
2011年 | 21604篇 |
2010年 | 12832篇 |
2009年 | 12940篇 |
2008年 | 18982篇 |
2007年 | 22626篇 |
2006年 | 7975篇 |
2005年 | 14715篇 |
2004年 | 10300篇 |
2003年 | 9174篇 |
2002年 | 6921篇 |
2001年 | 6372篇 |
2000年 | 5043篇 |
1999年 | 3676篇 |
1998年 | 2824篇 |
1997年 | 2822篇 |
1996年 | 2688篇 |
1995年 | 2447篇 |
1994年 | 2351篇 |
1993年 | 2177篇 |
1992年 | 2492篇 |
1991年 | 2457篇 |
1990年 | 2174篇 |
1989年 | 2133篇 |
1988年 | 2193篇 |
1987年 | 2126篇 |
1986年 | 2006篇 |
1985年 | 3067篇 |
1984年 | 3028篇 |
1983年 | 2428篇 |
1982年 | 2671篇 |
1981年 | 2514篇 |
1980年 | 2526篇 |
1979年 | 2462篇 |
1978年 | 2539篇 |
1977年 | 2427篇 |
1976年 | 2362篇 |
1975年 | 2305篇 |
1974年 | 2202篇 |
1973年 | 2318篇 |
1972年 | 1285篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
981.
In the present paper, the notion of norm series with respect to the norm residue symbol is generalized to high-dimensional local fields. Necessary and sufficient conditions for the existence of norm series are obtained. Bibliography: 12 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 60–83. 相似文献
982.
983.
E. García-Matres N. Stüßer M. Hofmann M. Reehuis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):35-42
The magnetic structures of Mn1-xFexWO4 with x
= 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase
diagram could be completed in the coexistence range of different magnetic structures up to x
= 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector
= (±1/4, 1/2, 1/2) was found for x
⩽ 0.22 while the magnetic spins order with
= (1/2, 0, 0) for x
≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with
= (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x
= 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽
x
⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed
to a spin arrangement with
= (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed
Mn2+- and Fe2+-ions in the coexistence range 0.12 ⩽
x
⩽ 0.29 of different magnetic structures related to those of pure MnWO4 and FeWO4.
Received 9 October 2002 Published online 14 March 2003 相似文献
984.
Matter implies the existence of a large-scale connected cluster of a uniform nature. The appearance of such clusters as a function of hadron density is specified by percolation theory. We can therefore formulate the freeze-out of interacting hadronic matter in terms of the percolation of hadronic clusters. The resulting freeze-out condition as a function of temperature and baryo-chemical potential interpolates between resonance gas behavior at low baryon density and repulsive nucleonic matter at low temperature, and it agrees well with the data.Received: 10 September 2003, Published online: 7 November 2003 相似文献
985.
The periodic precipitation pattern formation in gelatinous media is interpreted as a moving boundary problem. The time law,
spacing law and width law are revisited on the basis of the new scenario. The explicit dependence of the geometric structure
on the initial concentrations of the reactants is derived. Matalon—Packter law, which relates the spacing coefficient with
the initial concentrations is reformulated removing many ambiguities and impractical parameters. Experimental results are
discussed to establish the significance of moving boundary concept in the diffusion controlled pattern forming systems 相似文献
986.
I. A. Stefanova 《Acoustical Physics》2003,49(2):203-206
Empirical approximating formulas describing the most important psychophysiological properties of the human auditory analyzer are derived. 相似文献
987.
In this paper a predictive control strategy is applied to a periodic-review dynamic inventory system with deteriorating items.
Given the current inventory level, we determine the optimal production rates to be implemented at the beginning of each of
the following periods over the control horizon. The effectiveness of this approach is the use of future information of the
inventory target level and the desired production rate, which are available, along the fixed horizon. The deterioration coefficient
may be known or unknown and both cases are considered. In the case where it is unknown, the self-tuning predictive control
is applied. The proposed control algorithms are illustrated by simulations. 相似文献
988.
A Variable Neighborhood Search for the Multi Depot Vehicle Routing Problem with Time Windows 总被引:6,自引:0,他引:6
Michael Polacek Richard F. Hartl Karl Doerner Marc Reimann 《Journal of Heuristics》2004,10(6):613-627
The aim of this paper is to propose an algorithm based on the philosophy of the Variable Neighborhood Search (VNS) to solve Multi Depot Vehicle Routing Problems with Time Windows. The paper has two main contributions. First, from a technical point of view, it presents the first application of a VNS for this problem and several design issues of VNS algorithms are discussed. Second, from a problem oriented point of view the computational results show that the approach is competitive with an existing Tabu Search algorithm with respect to both solution quality and computation times. 相似文献
989.
The vibronic spectra of charge transfer excitons (CTE) in a molecular one-component or alternatingly ordered two-component chain are treated in the framework of a dynamic approach (neglecting thermal excitations of the intramolecular vibrations). The model introduces two mechanisms of coupling between CTEs and vibrational quanta: (1) shift of the equilibrium positions of the nuclei in the ionized donor or acceptor; (2) change of the vibrational frequency in the ionized molecule. This model allows to generalize the simple CTE Hamiltonian and the vibronic Hamiltonian of Frenkel excitons. The linear optical susceptibility is calculated in the vibronic region (one CTE and one vibrational quantum). The double splitting of vibronics of CTEs was analyzed: (1) the splitting connected with the location of the intramolecular vibration on the donors or on the acceptors; (2) the splitting connected with the symmetry of the vibronic spectra (in the degenerate case). The general structure of the vibronic spectra of CTEs is established. It contains structureless absorption lines, which correspond to two-particle bands (the phonon is excited on a neutral molecule neighboring the donor or the acceptor) and Lorentz-type lines of one-particle states, which correspond to the bound propagation of the CTE and the phonon. 相似文献
990.
A.D. Bykov V.N. Saveliev C. Camy-Peyret A. Valentin 《Journal of Molecular Spectroscopy》2004,224(2):164-175
Forty-seven N2 broadened water vapor line-widths have been measured in the 1845-2140 cm−1 spectral range with a Fourier Transform spectrometer in the 258-330 K temperature range at a spectral resolution of 0.005 cm−1 for the lines with upper state rotational quantum number up to 16. The measured exponents of the temperature dependence of the width exhibit a large range of values from 1.60 to −0.86. Theoretical calculations were made using a semi-empirical technique based on the Anderson theory. The calculated broadening coefficients as well as the temperature exponents for the half-width agree satisfactory with measured values. 相似文献