全文获取类型
收费全文 | 487篇 |
免费 | 148篇 |
国内免费 | 103篇 |
专业分类
化学 | 208篇 |
晶体学 | 6篇 |
力学 | 31篇 |
综合类 | 2篇 |
数学 | 186篇 |
物理学 | 305篇 |
出版年
2024年 | 1篇 |
2023年 | 34篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 30篇 |
2019年 | 31篇 |
2018年 | 19篇 |
2017年 | 29篇 |
2016年 | 26篇 |
2015年 | 30篇 |
2014年 | 37篇 |
2013年 | 41篇 |
2012年 | 52篇 |
2011年 | 47篇 |
2010年 | 29篇 |
2009年 | 54篇 |
2008年 | 50篇 |
2007年 | 44篇 |
2006年 | 33篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
排序方式: 共有738条查询结果,搜索用时 15 毫秒
101.
与二项式光场相互作用的运动原子熵压缩 总被引:2,自引:2,他引:0
运用量子信息熵理论,研究了二项式光场与运动二能级原子相互作用过程中运动原子的信息熵压缩。讨论了不同的原子初态和场的有关参数对原子信息熵压缩的影响。结果表明:选择原子初态、场模结构、场调节参数及原子运动速度可以调控原子信息熵的压缩方向、偶极矩分量值和压缩周期;适当的选择参数可得到持续性的原子信息熵压缩。 相似文献
102.
利用全量子理论,研究了运动纠缠双原子与薛定谔猫态光场相互作用系统的场熵演化特性,讨论了光场强弱、相干态间的相位角、原子的运动和场模结构参数对系统场熵的影响.结果表明:原子运动导致场熵演化具有周期性;当场强较弱时,奇相干态光场与运动原子的纠缠度最大,而偶相干态光场与运动原子的纠缠度最小, Yurke-Stoler相干态光场与运动原子的纠缠度值介于中间;当场强足够大时,分别处于Yurke-Stoler相干态,奇相干态和偶相干态的光场与运动原子的纠缠度相等,场熵演化特性相同;随着原子运动速度的增大或场模结构参数的增大,场熵的演化周期缩短,并且场与原子的纠缠度逐渐减弱. 相似文献
103.
In this paper, we introduce the class of Hamilton type operators and study various properties of this class. We show that every Hamilton type operator with property (β) or (δ) is decomposable. In addition, we prove that a Hamilton type operator T satisfies property (β), Dunford’s property (C) and Weyl’s theorem if and only if its adjoint does. 相似文献
104.
<正>A new coupled integrable dispersionless equation is presented by considering a spectral problem.A Darboux transformation for the resulting coupled integrable dispersionless equation is constructed with the help of spectral problems.As an application,the N-soliton solution of the coupled integrable dispersionless equation is explicitly given. 相似文献
105.
Screening influence on the Stark effect of impurity states in strained wurtzite GaN/AlxGa1-xN heterojunctions under pressure 下载免费PDF全文
The screening effect of the random-phase-approximation on the states of shallow donor impurities in free strained wurtzite GaN/Al x Ga 1 x N heterojunctions under hydrostatic pressure and an external electric field is investigated by using a variational method and a simplified coherent potential approximation.The variations of Stark energy shift with electric field,impurity position,Al component and areal electron density are discussed.Our results show that the screening dramatically reduces both the blue and red shifts as well as the binding energies of impurity states.For a given impurity position,the change in binding energy is more sensitive to the increase in hydrostatic pressure in the presence of the screening effect than that in the absence of the screening effect.The weakening of the blue and red shifts,induced by the screening effect,strengthens gradually with the increase of electric field.Furthermore,the screening effect weakens the mixture crystal effect,thereby influencing the Stark effect.The screening effect strengthens the influence of energy band bending on binding energy due to the areal electron density. 相似文献
106.
Jie-Hui Yu Ling-Yun Pan Tie-Gang Wang Xiao-Bing Cui Yi-Zhi Li Tian-Hui Ma 《Journal of solid state chemistry》2003,175(2):152-158
The title compound [NiII(phen)3]2[Cu10H2I16] 1 (phen=1,10-phenanthroline, C12H8N2) was hydrothermally synthesized from a simple reaction of CuI-NiCl2·6H2O-phen·H2O-H2O. X-ray analysis revealed that it consists of NiN62+ core cation and decanuclear iodocuprate(I) anion together with two dissociative H+ ions. In anionic unit, the discrete decanuclear iodocuprate(I) is formed by crystallographically independent five monovalent copper atoms and eight iodine atoms via an inversion center. There exist two types of Cu(I) coordination sites; only one copper(I) atom is in a highly distorted triangular planar site, and the other four copper(I) atoms display the tetrahedral geometries. It deserves to be noted that four types of bridging modes of I− ions in which two are ordinary μ2- and μ3-bonding modes can be found. But the other two are the rectangle planar geometry and the novel μ4-bridge like an “umbrella”, and both of them are rather rare in the halocuprates(I). Compound 1 was crystallized in triclinic space group with a=11.6861(17), b=14.590(2), c=14.649(2) Å, α=76.370(2), β=70.830(2), γ=81.320(3)o, R=0.075, and was characterized by elemental analysis, IR spectrum and UV-VIS spectrum. The third-order non-linear optical property of 1 was also investigated and the compound exhibits the reverse saturable absorption and self-defocusing performance. 相似文献
107.
108.
The damage spreading of the Ising model on three kinds of networks is studied with Glauber dynamics. One of the networks is
generated by evolving the hexagonal lattice with the star-triangle transformation. Another kind of network is constructed
by connecting the midpoints of the edges of the topological hexagonal lattice. With the evolution of these structures, damage
spreading transition temperature increases and a general explanation for this phenomenon is presented from the view of the
network. The relationship between the transition temperature and the network measure-clustering coefficient is set up and
it is shown that the increase of damage spreading transition temperature is the result of more and more clustering of the
network. We construct the third kind of network-random graphs with Poisson degree distributions by changing the average degree
of the network. We show that the increase in the average degree is equivalent to the clustering of nodes and this leads to
the increase in damage spreading transition temperature.
相似文献
109.
The effects of electron-phonon interaction on energy levels of a polaron in a wurtzite nitride finite parabolic quantum well (PQW) are studied by using a modified Lee-Low-Pines variational method. The ground state, first excited state, and transition energy of the polaron in the GaN/Al0.3Ga0.7N wurtzite PQW are calculated by taking account of the influence of confined LO(TO)-like phonon modes and the half-spaee LO(TO)-like phonon modes and considering the anisotropy of all kinds of phonon modes. The numerical results are given and discussed. The results show that the electron-phonon interaction strongly affects the energy levels of the polaron, and the contributions from phonons to the energy of a polaron in a wurtzite nitride PQW are greater than that in an A1GaAs PQW. This indicates that ehe electron-phonon interaction in a wurtzite nitride PQW is not negligible. 相似文献
110.
Min Zeng Ang Ren Wubin Wu Yongsheng Zhao Chuanlang Zhan Jiannian Yao 《Chemical science》2020,11(34):9154
We present herein an innovative host–guest method to achieve induced molecular chirality from an achiral stilbazolium dye (DSM). The host–guest system is exquisitely designed by encapsulating the dye molecule in the molecule-sized chiral channel of homochiral lanthanide metal–organic frameworks (P-(+)/M-(−)-TbBTC), in which the P- or M-configuration of the dye is unidirectionally generated via a spatial confinement effect of the MOF and solidified by the dangling water molecules in the channel. Induced chirality of DSM is characterized by solid-state circularly polarized luminescence (CPL) and micro-area polarized emission of DSM@TbTBC, both excited with 514 nm light. A luminescence dissymmetry factor of 10−3 is obtained and the photoluminescence quantum yield (PLQY) of the encapsulated DSM in DSM@TbTBC is ∼10%, which is close to the PLQY value of DSM in dilute dichloromethane. Color-tuning from green to red is achieved, owing to efficient energy transfer (up to 56%) from Ln3+ to the dye. Therefore, this study for the first time exhibits an elegant host–guest system that shows induced strong CPL emission and enables efficient energy transfer from the host chiral Ln-MOF to the achiral guest DSM with the emission color tuned from green to red.Homochiral Ln-MOFs are synthesized to encapsulate achiral dyes to induce strong circularly polarized luminescence with a luminescence dissymmetry factor of 10−3. 相似文献