全文获取类型
收费全文 | 122415篇 |
免费 | 10976篇 |
国内免费 | 15356篇 |
专业分类
化学 | 93376篇 |
晶体学 | 1911篇 |
力学 | 4343篇 |
综合类 | 1164篇 |
数学 | 13702篇 |
物理学 | 34251篇 |
出版年
2024年 | 61篇 |
2023年 | 941篇 |
2022年 | 1737篇 |
2021年 | 2636篇 |
2020年 | 3298篇 |
2019年 | 3154篇 |
2018年 | 2826篇 |
2017年 | 3967篇 |
2016年 | 4463篇 |
2015年 | 3887篇 |
2014年 | 4935篇 |
2013年 | 9943篇 |
2012年 | 8551篇 |
2011年 | 7280篇 |
2010年 | 6158篇 |
2009年 | 7900篇 |
2008年 | 7965篇 |
2007年 | 8321篇 |
2006年 | 7594篇 |
2005年 | 6570篇 |
2004年 | 6167篇 |
2003年 | 5137篇 |
2002年 | 6310篇 |
2001年 | 3898篇 |
2000年 | 3651篇 |
1999年 | 3308篇 |
1998年 | 2428篇 |
1997年 | 2001篇 |
1996年 | 1690篇 |
1995年 | 1857篇 |
1994年 | 1615篇 |
1993年 | 1309篇 |
1992年 | 1259篇 |
1991年 | 863篇 |
1990年 | 755篇 |
1989年 | 670篇 |
1988年 | 526篇 |
1987年 | 426篇 |
1986年 | 393篇 |
1985年 | 322篇 |
1984年 | 344篇 |
1983年 | 174篇 |
1982年 | 270篇 |
1981年 | 197篇 |
1980年 | 214篇 |
1979年 | 206篇 |
1978年 | 166篇 |
1977年 | 97篇 |
1976年 | 86篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Summary. We generalise and apply a refinement indicator of the type originally designed by Mackenzie, Süli and Warnecke in [15] and
[16] for linear Friedrichs systems to the Euler equations of inviscid, compressible fluid flow. The Euler equations are symmetrized
by means of entropy variables and locally linearized about a constant state to obtain a symmetric hyperbolic system to which
an a posteriori error analysis of the type introduced in [15] can be applied. We discuss the details of the implementation of the refinement
indicator into the DLR--Code which is based on a finite volume method of box type on an unstructured grid and present numerical results.
Received May 15, 1995 / Revised version received April 17, 1996 相似文献
103.
104.
Summary. Let be a square matrix dependent on parameters and , of which we choose as the eigenvalue parameter. Many computational problems are equivalent to finding a point such that has a multiple eigenvalue at . An incomplete decomposition of a matrix dependent on several parameters is proposed. Based on the developed theory two new algorithms are
presented for computing multiple eigenvalues of with geometric multiplicity . A third algorithm is designed for the computation of multiple eigenvalues with geometric multiplicity but which also appears to have local quadratic convergence to semi-simple eigenvalues. Convergence analyses of these methods
are given. Several numerical examples are presented which illustrate the behaviour and applications of our methods.
Received December 19, 1994 / Revised version received January 18, 1996 相似文献
105.
Addition of functionalized zinc-copper reagents to the title complexes proceeds in a highly diastereoselective fashion to afford dienol complexes. The relative configurations of adducts 3d were determined by single X-ray diffraction analysis. 相似文献
106.
M. Hanson 《Chromatographia》1994,39(7-8):431-437
Summary Pressure/temperature variation in SFC was shown to influence selectivity towards steroids. Major changes were observed for polar column packings compared to non-polar packings and variation of the amount of modifier showed that this is valid over the whole investigated range. The effect is underlined by a fall in resolution in the low density range (low pressure/high temperature) for polar stationary phases and appears to be significantly larger than for non-polar phases. Major selectivity shifts induced by variation of the physical properties of the mobile phase are considered to be due to the greater effect of polar modifiers on the nature of polar stationary phases than on non-polar phases. 相似文献
107.
108.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2]
n
·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993. 相似文献
109.
固体力学有限元体系的结构拓扑变化理论 总被引:2,自引:1,他引:1
本文是文[1]的继续.文[1]提出了杆件系统的结构拓扑变化理论和拓扑变化法本文将这一理论和方法推进到连续体有限元体系;且在此基础上揭示出有限元体系的一个新性质,称为基本位移之梯度的正交性定理,从而给出一套设计敏度的显式表达式,可直接用于计算. 相似文献
110.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献