全文获取类型
收费全文 | 11455篇 |
免费 | 2756篇 |
国内免费 | 1795篇 |
专业分类
化学 | 5109篇 |
晶体学 | 121篇 |
力学 | 763篇 |
综合类 | 125篇 |
数学 | 1321篇 |
物理学 | 8567篇 |
出版年
2024年 | 17篇 |
2023年 | 109篇 |
2022年 | 187篇 |
2021年 | 261篇 |
2020年 | 322篇 |
2019年 | 242篇 |
2018年 | 263篇 |
2017年 | 317篇 |
2016年 | 412篇 |
2015年 | 470篇 |
2014年 | 636篇 |
2013年 | 945篇 |
2012年 | 725篇 |
2011年 | 871篇 |
2010年 | 767篇 |
2009年 | 860篇 |
2008年 | 940篇 |
2007年 | 937篇 |
2006年 | 798篇 |
2005年 | 747篇 |
2004年 | 571篇 |
2003年 | 623篇 |
2002年 | 575篇 |
2001年 | 478篇 |
2000年 | 442篇 |
1999年 | 423篇 |
1998年 | 325篇 |
1997年 | 268篇 |
1996年 | 243篇 |
1995年 | 180篇 |
1994年 | 166篇 |
1993年 | 141篇 |
1992年 | 125篇 |
1991年 | 106篇 |
1990年 | 64篇 |
1989年 | 81篇 |
1988年 | 53篇 |
1987年 | 45篇 |
1986年 | 21篇 |
1985年 | 53篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 44篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 839 毫秒
71.
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
72.
Yanghyun Byun 《Foundations of Physics》2004,34(6):987-1003
We consider a representation of the state reduction which depends neither on its reality nor on the details of when and how it emerges. Then by means of the representation we find necessary conditions, even if not the sufficient ones, for a decomposition of the state vector space to be a solution to the basis problem. The conditions are that the decomposition should be Lorentz invariant and orthogonal and that the associated projections should be continuous. They are shown to be able to determine a decomposition in each of a few examples considered if the other circumstances are taken into account together. 相似文献
73.
74.
利用相干渡越辐射(CTR)测量短和超短电子束团长度是国际上束测领域新发展的频域测量技术.文中理论分析和数值计算了北京自由电子激光装置的皮秒级的射频电子束团序列产生的CTR,当辐射波长在长于束长(4ps)时,渡越辐射发生相干增强效应;与非相干渡越辐射相比,当λ≥2πσz时,增强的倍数约等于束团中粒子的数目(108);CTR从亚毫米波到毫米波段呈宽带连续谱特性;渡越辐射能量主要集中在轴线附近,宏脉冲辐射能量高达几毫焦.设计采用偏振型束团长度测量系统,利用CTR自相关技术,实验测量该束团序列的纵向长度,并藉助傅里叶变换光谱法,推求束团电子分布. 相似文献
75.
利用拉曼型的Jaynes-Cummings模型传送两比特的未知原子态 总被引:6,自引:3,他引:3
实现量子态的隐形传送、尤其是多比特量子态的隐形传送在量子信息领域中有非常重要的作用,提出了一种隐形传送两比特未知原子态的方案,在此方案中,用两个两粒子纠缠态代替一个三粒子纠缠态作为量子信道,而且此方案可推广到隐形传送N比特的未知原子态。 相似文献
76.
77.
将介观无损耗传输线中的驻波场看成作相对运动的两列同频率的行波的叠加,此电路量子化后成为两个频率相同、不同模的光子场。计算和分析了激发相干态下电压和电流梯度的量子涨落,指出了双模传输线与一般的LC电路、双模传输线与单模传输线量子涨落的异同之处。 相似文献
78.
A scheme for teleporting a three-particle state is proposed when three pairs of entangled particles are used as quantum channels. Quantum teleportation can be successfully realized with a certain probability if the receiver adopts an appropriate unitary-reduction strategy. The probability of successful teleportation is determined by the smaller coetficients of the three entangled pairs. 相似文献
79.
Under dielectric continuum approximation, interface optical (IO) phonon modes and the Frohlich electron-IO phonon interaction Hamiltonian in a multi-shell spherical nanoheterosystem were derived and studied. Numericalcalculations on three-layer and four-layer CdS/HgS spherical nanoheterosystems have been performed. Results revealthat there are four IO phonon modes for the three-layer system and six IO phonon modes for the four-layer system.On each interface, there are two IO phonon modes, the frequency of one is between WTO,CdS and WLO,CdS, and that ofthe other is between WTO,HgS and WLO,HgS. With the increasing of quantum number l, the frequency of each IO modeapproaches one of the two frequency values of the single CdS/HgS heterostructure, and the potential for each IO modeis more and more localized at a certain interface, furthermore, the coupling between the electron-lO phonons becomes weaker. 相似文献
80.
A pseudopotential depending on an effective core radius is proposed to study the binding energy, equation of state, ion-ion
interaction, phonon dispersion curves (q-space and r-space analysis), mode Grüneisen parameters and dynamical elastic constants
of some fcc f-shell metals La, Yb, Ce and Th. The contribution of the s-like electrons is calculated in the second-order perturbation
theory for the potential while d and f-like electron is taken into account by introducing repulsive short-range Born-Mayer
term. The parameter of the potential is evaluated by zero pressure condition. An excellent agreement between theoretical investigations
and experimental findings is achieved which confirms the present formalism 相似文献