全文获取类型
收费全文 | 10626篇 |
免费 | 964篇 |
国内免费 | 627篇 |
专业分类
化学 | 4956篇 |
晶体学 | 272篇 |
力学 | 287篇 |
综合类 | 51篇 |
数学 | 331篇 |
物理学 | 6320篇 |
出版年
2025年 | 26篇 |
2024年 | 113篇 |
2023年 | 136篇 |
2022年 | 268篇 |
2021年 | 338篇 |
2020年 | 442篇 |
2019年 | 373篇 |
2018年 | 342篇 |
2017年 | 316篇 |
2016年 | 382篇 |
2015年 | 394篇 |
2014年 | 503篇 |
2013年 | 856篇 |
2012年 | 616篇 |
2011年 | 693篇 |
2010年 | 453篇 |
2009年 | 647篇 |
2008年 | 578篇 |
2007年 | 551篇 |
2006年 | 530篇 |
2005年 | 402篇 |
2004年 | 396篇 |
2003年 | 348篇 |
2002年 | 406篇 |
2001年 | 272篇 |
2000年 | 312篇 |
1999年 | 209篇 |
1998年 | 266篇 |
1997年 | 134篇 |
1996年 | 144篇 |
1995年 | 102篇 |
1994年 | 104篇 |
1993年 | 86篇 |
1992年 | 69篇 |
1991年 | 50篇 |
1990年 | 44篇 |
1989年 | 34篇 |
1988年 | 47篇 |
1987年 | 24篇 |
1986年 | 35篇 |
1985年 | 24篇 |
1984年 | 28篇 |
1983年 | 10篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
P. F. Yu J. G. Cai J. M. Liu G. T. Shen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):151-158
We investigate the phase decoherence effects on
the entanglement of a two-qubit anisotropic Heisenberg
model
with a nonuniform magnetic field in the x–z-plane. As a
measure of the entanglement, the concurrence of the system is
calculated. It is shown that when the magnetic field is along the
z-axis, the nonuniform and uniform components of the field have
no influence on the entanglement for the cases of
and
, respectively. But when
the magnetic field is not along the z-axis, both the uniform and
the nonuniform components of the field will introduce the
decoherence effects. It is found that the effects of the
Heisenberg chain's anisotropy in the Z-direction on the
entanglement are dependent on the direction of the field.
Moreover, the larger the initial concurrence is, the higher value
it will exhibit during the time evolution of the system for a
proper set of the parameters ν, Δ, θ, γ
, B and b. 相似文献
104.
105.
106.
J. Beula 《Physica D: Nonlinear Phenomena》2010,239(8):397-406
The nonlinear spin excitations in an anisotropic helimagnet in the presence of a constant magnetic field are investigated in the classical continuum limit. The helical character is introduced into the model, in analogy with the twist in a cholesteric liquid crystal. After deriving a class of spin wave solutions for the stereographic representation of the Landau-Lifshitz equation, in-plane stationary spin configurations are obtained and their stability is analysed. When the external magnetic field is along the anisotropic axis, modulational instability is observed in the spin lattice, and when the external magnetic field is normal to the anisotropic axis, the spin configurations are unstable. The perturbed spin components show fluctuations in the tail region, while the velocity and amplitude of the soliton remain unaltered. 相似文献
107.
Bindiya Chana 《Journal of Macromolecular Science: Physics》2017,56(11-12):863-872
The optical, electrical and acoustical properties of polymer solutions based on polyvinyl pyrrolidone (PVP) doped with cupric sulphate (CuSO4) were studied. The polymer solutions were prepared by varying the concentration of Cu in the PVP using a simple chemical route. The UV-visible spectroscopy results showed that the optical absorbance decreased with an increase in wavelength from 300 to 700 nm. The optical band gaps were found to decrease with addition of the Cu salt in the polymer. The refractive index also showed significant variation with the doping of the CuSO4. The electrical conductivity of the polymer solutions was found to increase with temperature as well as concentration of Cu while the activation energy of electrical conduction decreased with concentration of Cu. The ultrasonic velocities of the polymer solutions were measured at a frequency of 1 MHz using an ultrasonic interferometer. The ultrasonic velocity and surface tension were increased while the adiabatic compressibility, acoustic impedance and intermolecular free length, the average distance between the surfaces of the coils of adjacent molecules, were decreased with increase in the concentration of CuSO4 in the PVP. 相似文献
108.
理论上对二级相变中热容、体膨胀系数、等温压缩系数三个热力学物理量的变化进行了分析,进而使用自旋链模型的基态能量和von Neumann熵随模型参数变化的突变行为对二级相变中这三个物理量的变化所引起的系统序变进行模拟,得到二级相变中热容、体膨胀系数、等温压缩系数的变化是由于系统内部微观上发生关联序变的结果。 相似文献
109.
Hiroyuki Yoshida Hiroshi Deguchi Kazuhiro Miura Masaki Horiuchi Toru Inagaki 《Solid State Ionics》2001,140(3-4):191-199
The oxide ionic conductivity measurements of singly and doubly doped ceria compounds were carried out. Singly and doubly doped ceria used in this study were Ce0.8Ln0.2O1.9 (Ln=Y, Sm, Nd, or La) and Ce0.8La0.1Y0.1O1.9, respectively. Lattice constants of these compounds were in proportion to the ionic radius of the dopant(s). The doubly doped ceria compound showed oxide ionic conductivity comparative to the average of that of each corresponding singly doped sample. This finding indicates that the conductivity is influenced by both dopants in the doubly doped compounds. The extended X-ray absorption fine structure (EXAFS) study showed that the coordination number of oxide ions at the nearest neighbor of cation was related to the ionic conductivity. It was found that the conductivity gave the highest value when oxygen vacancies were randomly distributed in the lattice. This indicates that the local structure seriously affects oxide ionic conduction in singly and doubly doped ceria compounds. 相似文献
110.
Auf der Basis von 85Kr wurde ein Prüfstand für die routinemäßge Dichtigkeitsprüfung von Halbleiterbauelementen entwickelt und gebaut. Die Anlage arbeitet mit einer Aktivkohlepumpe und ist für einen Maximaldruck ion 13 kp/cm2 und eine Maximalaktivität von 40Ci85Kr ausgelegt. Es werden einige theoretische Angaben zur Methode gemacht und der Auf ban sowie die Funktionsweise des Prüfstandes beschrieben. Die erhaltenen Ergebnisse werden mit denen anderer Methoden verglichen. 相似文献