全文获取类型
收费全文 | 11825篇 |
免费 | 823篇 |
国内免费 | 514篇 |
专业分类
化学 | 3836篇 |
晶体学 | 47篇 |
力学 | 969篇 |
综合类 | 75篇 |
数学 | 5753篇 |
物理学 | 2482篇 |
出版年
2024年 | 14篇 |
2023年 | 191篇 |
2022年 | 162篇 |
2021年 | 313篇 |
2020年 | 453篇 |
2019年 | 400篇 |
2018年 | 422篇 |
2017年 | 478篇 |
2016年 | 432篇 |
2015年 | 369篇 |
2014年 | 644篇 |
2013年 | 1606篇 |
2012年 | 866篇 |
2011年 | 685篇 |
2010年 | 515篇 |
2009年 | 790篇 |
2008年 | 790篇 |
2007年 | 633篇 |
2006年 | 517篇 |
2005年 | 499篇 |
2004年 | 379篇 |
2003年 | 274篇 |
2002年 | 234篇 |
2001年 | 139篇 |
2000年 | 155篇 |
1999年 | 143篇 |
1998年 | 121篇 |
1997年 | 114篇 |
1996年 | 112篇 |
1995年 | 89篇 |
1994年 | 82篇 |
1993年 | 61篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 27篇 |
1989年 | 31篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 47篇 |
1984年 | 60篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 27篇 |
1980年 | 18篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
《Physics letters. A》2020,384(9):126190
We propose a single-molecule electrical switches consisting of a photochromic dimethyldihydropyrene/cyclophanediene molecule sandwiched between two graphene electrodes and investigate the electronic transport by using density-functional theory and nonequilibrium Green's function methods. The “open” and “closed” isomers of the photochromic molecule are shown to have electrical switching behavior and negative differential resistance effect. Moreover, it is also found that the switching ratio between two different conductive states depends on the ambient temperature, and the device behaves as a stable electrical switch around room temperature, which is in agreement with a recent experimental study of another photochromic molecule diarylethene reported by Jia et al. (2016) [17]. 相似文献
52.
53.
A coordinate transformation technique between straight magnetic field line coordinate system (Ψ, θ) and Cartesian coordinate system (R, Z) is presented employing a Solov'ev solution of the Grad-Shafranov equation. Employing the equilibrium solution, the poloidal magnetic flux Ψ(R, Z) of a diverted tokamak, magnetic field line equation is solved computationally to find curves of constant poloidal angle θ, which provides us with explicit relations R = R(Ψ, θ) and Z = Z(Ψ, θ). Correspondingly, conversion from one coordinate to the other along particle trajectories in the vicinity of separatrix is demonstrated. Based on the magnetic structure, a finite element mesh is generated in a diverted tokamak geometry to solve Poisson's equation. 相似文献
54.
55.
《Physics letters. A》2020,384(28):126732
In this work, we investigate the electronic transport properties of M/SiC Schottky junctions (M=Ag, Au and Pd). The results show that the band structures of hydrogenated zigzag SiC nanoribbons (ZSiCNRs) and hydrogenated armchair SiC nanoribbons (ASiCNRs) are almost unaffected by their width changes. When the hydrogenated 7-ASiCNR is directly connected to the Ag, Au and Pd electrode, the transmission spectra of three metal-semiconductor junctions show that the Fermi level of metal is pinned to a fixed position in the semiconductor band gap of hydrogenated 7-ASiCNR. The nearly same rectifying current-voltage characteristics are found in three metal-semiconductor junctions. The average rectification ratios of three M/SiC Schottky junctions are all in the neighborhood of 106. In other word, the M/SiC Schottky junction has remarkable application prospect as the candidate for Schottky Diode. 相似文献
56.
57.
《Physics letters. A》2020,384(26):126642
A novel method to make Lagrangians Galilean invariant is developed. The method, based on null Lagrangians and their gauge functions, is used to demonstrate the Galilean invariance of the Lagrangian for Newton's law of inertia. It is suggested that this new solution of an old physics problem may have implications and potential applications to all gauge-based theories of physics. 相似文献
58.
Nonlinear effects such as friction and freeplay on the control surfaces can affect aeroelastic dynamics during flight. In particular, these nonlinearities can induce limit cycle oscillations (LCO), changing the system stability, and because of this it is essential to employ computational methods to predict this type of motion during the aircraft development cycle. In this context, the present article presents a matrix notation for describing the Hénon’s method used to reduce errors when considering piecewise linear nonlinearities in the numerical integration process. In addition, a new coordinate system is used to write the aeroelastic system of equations. The proposal defines a displacement vector with generalized and physical variables to simplify the computational implementation of the Hénon’s technique. Additionally, the article discusses the influence of asymmetric freeplay and friction on the LCO of an airfoil with control surface. The results show that the extended Hénon’s technique provides more accurate LCO predictions, that friction can change the frequency and amplitude of these motions, and the asymmetry of freeplay is important to determine the LCO behavior. 相似文献
59.
60.