全文获取类型
收费全文 | 1409篇 |
免费 | 28篇 |
国内免费 | 4篇 |
专业分类
化学 | 809篇 |
晶体学 | 10篇 |
力学 | 26篇 |
综合类 | 5篇 |
数学 | 41篇 |
物理学 | 145篇 |
无线电 | 405篇 |
出版年
2023年 | 4篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 33篇 |
2013年 | 21篇 |
2012年 | 34篇 |
2011年 | 27篇 |
2010年 | 26篇 |
2009年 | 29篇 |
2008年 | 31篇 |
2007年 | 42篇 |
2006年 | 34篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 32篇 |
2002年 | 12篇 |
2001年 | 13篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1985年 | 75篇 |
1984年 | 47篇 |
1983年 | 44篇 |
1982年 | 47篇 |
1981年 | 161篇 |
1980年 | 149篇 |
1979年 | 35篇 |
1978年 | 76篇 |
1977年 | 71篇 |
1976年 | 51篇 |
1975年 | 57篇 |
1974年 | 52篇 |
1973年 | 35篇 |
1968年 | 19篇 |
1962年 | 4篇 |
1958年 | 4篇 |
1957年 | 3篇 |
1955年 | 4篇 |
1952年 | 1篇 |
1949年 | 4篇 |
1948年 | 1篇 |
排序方式: 共有1441条查询结果,搜索用时 15 毫秒
971.
972.
The Fokker-Planck approximation for n-dimensional nonmarkovian Langevin equations is discussed through an expansion in powers of the correlation time of the noise. Exact cases are considered and an application to brownian motion is presented. 相似文献
973.
974.
Robert W. Irving 《Discrete Mathematics》1974,9(3):251-264
The generalised Ramsey number R(G1, G2,..., Gk) is defined as the smallest integer n such that, if the edges of Kn, the complete graph on n vertices, are coloured using k colours C1, C2,..., Ck, then for some i(1≤i≤k) there is a subgraph Gi of Kn with all of its edges colour Ci. When G1=G2=...,Gk=G, we use the more compact notation Rk(G).The generalised Ramsey numbers Rk(G) are investigated for all graphs G having at most four vertices (and no isolates). This extends the work of Chvátal and Harary, who made this investigation in the case k=2. 相似文献
975.
we give some general remarks on the quantization of systems where the energy operator is not conserved in time. Explicitly, we consider a damped harmonic oscillator and transform the corresponding Schrödinger-Langevin equation to the dual picture where the observables are time dependent but not the states. In this picture the time evolution will be described by a completely positive dynamical semigroup. At finite temperatures the situation is more complicated. 相似文献
976.
It is shown that the properties of semiconductors can be modified by solid electrochemical cells. These cells can be used as dopant sources for introduction of impurities into the semiconductor lattice. The solid electrolyte is so chosen that the ionic conducting species are the desired dopants. The controllability of the doping operation is very sensitive and either a constant concentration or a specified concentration profile can be achieved. These cells can also be used to modify the semiconductor surfaces such that only limited penetration of impurities is achieved. 相似文献
977.
Michael O. Albertson 《Discrete Mathematics》1973,4(3):197-199
Sufficient conditions are established for Hadwiger's Conjecture to be valid in thecase r = 5. 相似文献
978.
Helicon waves can be exploited in EPR studies of localized magnetic moments in high-conductivity semiconductors when the free carriers have small effective mass and high mobility. In an electron plasma helicons have precisely the polarization required to elicit EPR, and the plasma background actually enhances the resonance intensity. Microwave transmission experiments on Hg1-xMnxTe, a narrow-gap semiconductor with localized Mn++ magnetic moments, are described to illustrate this effect. 相似文献
979.
A recently published paper in which the inner- and outer-sphere contributions in redox reactions are compared is incorrect. If one uses the experimental values for the force constants, rather than those calculated from the Urey—Bradley method, one finds Rinner = 1.6 Rout, where R represents the reorganization energy. 相似文献
980.
The threshold behavior of Raman amplitudes for photon energies near dissociation of the intermediate potential surface of a diatomic molecule is determined. Structure in the Raman amplitudes is calculated and found to be due to resonance of the intermediate potential surface. 相似文献