全文获取类型
收费全文 | 9651篇 |
免费 | 550篇 |
国内免费 | 73篇 |
专业分类
化学 | 7314篇 |
晶体学 | 85篇 |
力学 | 172篇 |
数学 | 886篇 |
物理学 | 1817篇 |
出版年
2023年 | 35篇 |
2022年 | 144篇 |
2021年 | 193篇 |
2020年 | 155篇 |
2019年 | 176篇 |
2018年 | 142篇 |
2017年 | 132篇 |
2016年 | 337篇 |
2015年 | 296篇 |
2014年 | 357篇 |
2013年 | 594篇 |
2012年 | 714篇 |
2011年 | 772篇 |
2010年 | 490篇 |
2009年 | 406篇 |
2008年 | 635篇 |
2007年 | 580篇 |
2006年 | 542篇 |
2005年 | 485篇 |
2004年 | 481篇 |
2003年 | 364篇 |
2002年 | 368篇 |
2001年 | 179篇 |
2000年 | 190篇 |
1999年 | 120篇 |
1998年 | 82篇 |
1997年 | 74篇 |
1996年 | 94篇 |
1995年 | 86篇 |
1994年 | 75篇 |
1993年 | 59篇 |
1992年 | 78篇 |
1991年 | 48篇 |
1990年 | 49篇 |
1989年 | 55篇 |
1988年 | 36篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 60篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 32篇 |
1981年 | 41篇 |
1980年 | 31篇 |
1979年 | 36篇 |
1978年 | 25篇 |
1977年 | 34篇 |
1976年 | 28篇 |
1975年 | 25篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Hyun Chul Choi Min Kyu Lee Hyun Joon Shin Seung Bin Kim 《Journal of Electron Spectroscopy and Related Phenomena》2003,130(1-3):85-96
To investigate the formation of a solid electrolyte interface (SEI) on the Li1+xV3O8 electrode surface in the thermodynamic stability range of the organic electrolyte, we applied scanning photoelectron microscopy (SPEM) to a pristine electrode and to an electrode after ten cycles. The F K-edge absorption spectrum of the cycled electrode showed that LiF forms on the electrode surface during the lithium insertion–extraction process in the Li1+xV3O8/Li cell. The photoelectron spectrum for the cycled electrode showed intense spectral features corresponding to Li 1s, F 2s, F 2p, and P 2p electron signals, whereas these spectral features were of negligible intensity for the pristine electrode. The above results give strong support for the formation of an SEI that consists of LiF and compounds containing phosphorus during operation of the battery. The SPEM images also revealed that the fluorine distribution on the surface of the cycled electrode was inhomogeneous. 相似文献
42.
43.
Shin Ichi Aihara 《Acta Appl Math》1994,35(1-2):131-151
The purpose of this paper is to study the identification problem of a spatially varying discontinuous parameter in stochastic hyperbolic equations. In previous works, the consistency property of the maximum likelihood estimate (MLE) was explored and the generating algorithm for MLE proposed under the condition that an unknown parameter is in a sufficiently regular space with respect to spatial variables.In order to show the consistency property of the MLE for a discontinuous coefficient, we use the method of sieves, i.e. the admissible class of unknown parameters is projected into a finite-dimensional space. For hyperbolic systems, we cannot obtain a regularity property of the solution with respect to a parameter. So in this paper, the parabolic regularization technique is used. The convergence of the derived finite-dimensional MLE to the infinite-dimensional MLE is justified under some conditions. 相似文献
44.
On the harmonic Bergman space of the half-space, we give characterizations for an arbitrary positive Toeplitz operator to
be a Schatten (or Schatten-Herz) class operator in terms of averaging functions and Berezin transforms. Examples are provided
to show that various results are sharp.
This research was supported by KOSEF(R01-2003-000-10243-0). 相似文献
45.
46.
In this paper we discuss farthest-point problems in which a set or sequence S of n points in the plane is given in advance and can be preprocessed to answer various queries efficiently. First, we give a data structure that can be used to compute the point farthest from a query line segment in O(log2n) time. Our data structure needs O(nlogn) space and preprocessing time. To the best of our knowledge no solution to this problem has been suggested yet. Second, we show how to use this data structure to obtain an output-sensitive query-based algorithm for polygonal path simplification. Both results are based on a series of data structures for fundamental farthest-point queries that can be reduced to each other. 相似文献
47.
Nusselt number correlations for heat transfer to small spheres in thermal plasma flows 总被引:1,自引:0,他引:1
Seven different equations predicting heat transfer rates to small spheres in plasma flows are examined considering argon and nitrogan as plasma gases from 300 to 21,000 K at 1 atm. For argon there is a general consensus up to 9000 K, beyond which wide deviations in behavior occur. For nitrogen, the seven correlations are in good agreement up to 4000 K, but show substantial deviations beyond this value. Comparisons with the sparsely available experimental data are made for argon from 300 to 17,000 K and for nitrogen up to 5500 K. Disagreement between the various correlations and experiment can exceed one order of magnitude. 相似文献
48.
Young Wook Kim Seong-Deog Yang 《Proceedings of the American Mathematical Society》2006,134(11):3379-3390
We prove the existence of an infinite family of complete spacelike maximal surfaces with singularities in Lorentz-Minkowski three-space and study their properties. These surfaces are distinguished by their number of handles and have two elliptic catenoidal ends.
49.
Mary Cheung Alex B. Young Alex G. Harrison 《Journal of the American Society for Mass Spectrometry》1994,5(6):553-557
O? and OH? react with fatty acid methyl esters (FAMES) under chemical ionization conditions both as Bronsted bases to form [M - H]? and as nucleophiles to form the carboxylate ion RCOO?. O? shows a much greater tendency to react as a nucleophile than does OH?. The [M - H]? ions fragment by elimination of CH3OH, with unsaturation in certain positions in the fatty acid hydrocarbon chain promoting this elimination for unknown reasons. The reaction of O? and OH? with triacylglycerols leads to [M - H]?, characteristic of the molecular mass, and to carboxylate ions characteristic of the fatty acid(s) present in the lipid. The presence of the three ester functions in the lipids greatly enhances the formation of carboxylate ions compared to the FAMES. 相似文献
50.