全文获取类型
收费全文 | 2703篇 |
免费 | 78篇 |
国内免费 | 15篇 |
专业分类
化学 | 1650篇 |
晶体学 | 11篇 |
力学 | 71篇 |
数学 | 481篇 |
物理学 | 583篇 |
出版年
2023年 | 18篇 |
2021年 | 29篇 |
2020年 | 30篇 |
2019年 | 41篇 |
2018年 | 25篇 |
2017年 | 33篇 |
2016年 | 59篇 |
2015年 | 60篇 |
2014年 | 48篇 |
2013年 | 143篇 |
2012年 | 116篇 |
2011年 | 122篇 |
2010年 | 95篇 |
2009年 | 78篇 |
2008年 | 145篇 |
2007年 | 138篇 |
2006年 | 122篇 |
2005年 | 128篇 |
2004年 | 127篇 |
2003年 | 100篇 |
2002年 | 89篇 |
2001年 | 68篇 |
2000年 | 60篇 |
1999年 | 45篇 |
1998年 | 43篇 |
1997年 | 25篇 |
1996年 | 51篇 |
1995年 | 36篇 |
1994年 | 27篇 |
1993年 | 31篇 |
1992年 | 42篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 37篇 |
1987年 | 23篇 |
1986年 | 23篇 |
1985年 | 29篇 |
1984年 | 21篇 |
1983年 | 30篇 |
1982年 | 35篇 |
1981年 | 30篇 |
1980年 | 27篇 |
1979年 | 28篇 |
1978年 | 20篇 |
1977年 | 21篇 |
1976年 | 28篇 |
1975年 | 26篇 |
1974年 | 22篇 |
1973年 | 19篇 |
排序方式: 共有2796条查询结果,搜索用时 15 毫秒
1.
Mike R. Jeffrey 《Nonlinear dynamics》2015,81(4):1699-1716
2.
3.
Mathematical Notes - 相似文献
4.
Given a tree
with leaf set X, there are certain ways of arranging the elements of X in a circular order so that
can be embedded in the plane and ‘preserve’ this ordering. We investigate some new combinatorial properties of these ‘circular orderings.’ We then use these properties to establish two results concerning dissimilarity maps on X that are induced by edge-weighted trees with leaf set X. 相似文献
5.
D. I. Naiduss W. W. Kiesewetter S. L. Dikanskaja J. Schapiro R. Meurice J. Cartiaux E. F. Posorski G. N. Murthy S. Mihaéloff A. D. Rich J. J. Vollertsen Gh. Ghimicescu G. Kotsis C. T. Townsend J. A. Esty F. C. Baselt R. Dubrisay J. Gascon E. R. Scheggia K. M. Renner E. S. Miller C. A. Mitchell A. G. Sossin und S. E. Spektor 《Fresenius' Journal of Analytical Chemistry》1939,118(1-2):48-51
Ohne Zusammenfassung 相似文献
6.
M. Missous C. Mitchell J. Sly K. T. Lai R. Gupta S. K. Haywood 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):496
Highly strained quantum cascade laser (QCL) and quantum well infrared photodetector (QWIPs) structures based on InxGa(1−x)As−InyAl(1−y)As (x>0.8,y<0.3) layers have been grown by molecular beam epitaxy. Conditions of exact stoichiometric growth were used at a temperature of 420°C to produce structures that are suitable for both emission and detection in the 2–5 μm mid-infrared regime. High structural integrity, as assessed by double crystal X-ray diffraction, room temperature photoluminescence and electrical characteristics were observed. Strong room temperature intersubband absorption in highly tensile strained and strain-compensated In0.84Ga0.16As/AlAs/In0.52Al0.48As double barrier quantum wells grown on InP substrates is demonstrated. Γ–Γ intersubband transitions have been observed across a wide range of the mid-infrared spectrum (2–7 μm) in three structures of differing In0.84Ga0.16As well width (30, 45, and 80 Å). We demonstrate short-wavelength IR, intersubband operation in both detection and emission for application in QC and QWIP structures. By pushing the InGaAs–InAlAs system to its ultimate limit, we have obtained the highest band offsets that are theoretically possible in this system both for the Γ–Γ bands and the Γ–X bands, thereby opening up the way for both high power and high efficiency coupled with short-wavelength operation at room temperature. The versatility of this material system and technique in covering a wide range of the infrared spectrum is thus demonstrated. 相似文献
7.
Chaotic dynamics in open systems produces fractals. This can be seen, for example, in the ionization of an electron from a
hydrogen atom in applied parallel electric and magnetic fields. We summarize some of our recent work on the order that can
be found in these fractals. 相似文献
8.
We investigate the combinatorics of a topological space that is generated by the set of edge-weighted finite trees. This space arises by multiplying the weights of edges on paths in trees and is closely connected to tree reconstruction problems involving finite state Markov processes. We show that this space is a contractible finite CW-complex whose face poset can be described via a partial order on semilabelled forests. We then describe some combinatorial properties of this poset, showing that, for example, it is pure, thin and contractible. 相似文献
9.
Jean-Pierre Dedieu Gregorio Malajovich Mike Shub 《Foundations of Computational Mathematics》2005,5(2):145-171
We prove a linear bound on the average total curvature of the
central path of linear programming theory in terms of the number
of independent variables of the primal problem, and independent of
the number of constraints. 相似文献
10.
We obtain Dirac’s classic monopole charge quantization from the point of view of geometric quantization and demonstrate how this leads to the conclusion that the electromagnetic field is a U(1)-gauge field. 相似文献