全文获取类型
收费全文 | 8931篇 |
免费 | 1926篇 |
国内免费 | 958篇 |
专业分类
化学 | 7116篇 |
晶体学 | 36篇 |
力学 | 864篇 |
综合类 | 49篇 |
数学 | 343篇 |
物理学 | 3407篇 |
出版年
2023年 | 101篇 |
2022年 | 166篇 |
2021年 | 227篇 |
2020年 | 328篇 |
2019年 | 344篇 |
2018年 | 388篇 |
2017年 | 333篇 |
2016年 | 388篇 |
2015年 | 489篇 |
2014年 | 674篇 |
2013年 | 852篇 |
2012年 | 657篇 |
2011年 | 713篇 |
2010年 | 563篇 |
2009年 | 649篇 |
2008年 | 624篇 |
2007年 | 553篇 |
2006年 | 545篇 |
2005年 | 495篇 |
2004年 | 453篇 |
2003年 | 429篇 |
2002年 | 270篇 |
2001年 | 199篇 |
2000年 | 201篇 |
1999年 | 163篇 |
1998年 | 151篇 |
1997年 | 138篇 |
1996年 | 95篇 |
1995年 | 126篇 |
1994年 | 90篇 |
1993年 | 72篇 |
1992年 | 56篇 |
1991年 | 18篇 |
1990年 | 43篇 |
1989年 | 29篇 |
1988年 | 23篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 543 毫秒
71.
H. Barentzen 《Annalen der Physik》2006,15(9):684-698
The eigenvalues of the weakly coupled T ? t Jahn‐Teller problem are known for several decades, and the same holds also true for the eigenstates. These, however, are only given in the traditional position representation, which proves inconvenient if one attempts to extend the weak‐coupling treatment into the region of stronger coupling. Here the solution of the T ? t eigenvalue problem at weak coupling is derived in terms of creation and annihilation operators. This reformulation of the problem is nontrivial, since the algebraic form of the oscillator eigenvectors, being simultaneous angular‐momentum eigenstates, has been worked out only recently and is probably still widely unknown. The electronic and oscillator eigenstates are then coupled to form eigenvectors of the total angular momentum. Finally, in preparation for an extension of the weak‐coupling treatment, the action of the boson creation and annihilation operators on the oscillator eigenvectors is calculated, thus completing the algebraic approach to the weakly coupled T ? t system. 相似文献
72.
We investigate linear parabolic systems with coupled nonsmooth capacities and mixed boundary conditions. We prove generalized resolvent estimates in W?1, p spaces. The method is an appropriate modification of a technique introduced by Agmon to obtain Lp estimates for resolvents of elliptic differential operators in the case of smooth boundary conditions. Moreover, we establish an existence and uniqueness result. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
73.
74.
A. Waksberg 《International Journal of Infrared and Millimeter Waves》2002,23(9):1327-1335
Coupling losses have been calculated for laser resonators with unequal apertures and extended Fresnel Numbers. This was done using both, diffraction theory and a simple linear model.A close form expression was derived to calculate coupling losses with reasonable accuracies for a limited range of paramters. This should help in the preliminary design of hole coupling laser resonators. 相似文献
75.
Summary The role of chemical reactions in the selection of patterns in phase-separating mixtures is presented. Linearized theory and
computer simulation show that the initial long-wavelength instability characteristic of spinodal decomposition is suppressed
by chemical reactions, which restrict domain growth to intermediate length scales even in the late stages of phase separation.
Our findings suggest that chemical reactions may provide a novel way to stabilize and tune the steady-state morphology of
phase-separating materials.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
76.
采用基于相对论平均场的耦合常数解析延拓方法研究球形核的单粒子共振态.具体计算了Zr同位素链中巨晕核的核芯核122Zr阈值附近的中子共振态的能量、宽度和波函数,其结果同相应的散射相移法的结果一致. Using analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean field (RMF) theory, the energies, widths and wave functions for single-particle resonant states close to the continuum threshold are evaluated. Predictions are also compared with corresponding results obtained by the scattering phase shift method. 相似文献
77.
References: 《理论物理通讯》2007,48(9):428-430
By virtue of the technique of integration within an ordered product of operators, we derive the normal ordering expansion of a one- and two-mode combination squeezing operator for two harmonic oscillators with coordinatemomentum coupling. It turns out that this squeezing operator just diagonalizes the Hamiltonian H = p21/2m1 m1ω21x21/2 p22/2m2 m2ω22x22/2 - λx2p1, so its ground state is a one- and two-mode combination squeezed state.Quantum fluctuation in the ground state is calculated. 相似文献
78.
用Von Neumann熵研究了附加克尔介质的压缩真空场与二能级原子依赖强度耦合相互作用量子体系的量子纠缠特性.讨论了初始压缩真空场的压缩度以及克尔非线性作用的强度对该量子体系纠缠特性的影响.结果表明,克尔介质的非线性作用的强弱可以改变体系量子纠缠的周期性;在初始压缩度较大(r=5)时,克尔介质的非线性作用可导致原子与场持续地处于最大纠缠态,无消纠缠态或持续地处于消纠缠态.
关键词:
压缩真空态
克尔介质
依赖强度耦合J-C模型
Von Neumann熵
量子纠缠 相似文献
79.
Ti(IV) as TiCl3(O3SCF3) and TiO(O2CCF3)2 are used as efficient catalysts for oxidative coupling of aliphatic, aromatic and heteroaromatic thiols to their disulfides in the presence of NaI under air atmosphere. 相似文献
80.
Jérémie Fournier Dit Chabert 《Tetrahedron》2004,60(14):3221-3230
Straightforward and rapid access to 2-arylbenzo[b]thiophenes has been developed. It involved a catalytic coupling of 3-activated benzo[b]thiophenes with several aryl halides in the presence of a phosphine-free palladium system. In case of fragile functional groups such as aldehydes, a quaternary ammonium was used as an additive as with the other substrates, the coupling performed better and faster in the presence of a crown ether, the best one being DCH-18-C-6, with good yields and low reaction times. This method would provide a direct access to novel structures of biological interest. 相似文献