全文获取类型
收费全文 | 7370篇 |
免费 | 1746篇 |
国内免费 | 690篇 |
专业分类
化学 | 2118篇 |
晶体学 | 61篇 |
力学 | 786篇 |
综合类 | 123篇 |
数学 | 975篇 |
物理学 | 5743篇 |
出版年
2024年 | 30篇 |
2023年 | 69篇 |
2022年 | 175篇 |
2021年 | 192篇 |
2020年 | 198篇 |
2019年 | 231篇 |
2018年 | 206篇 |
2017年 | 261篇 |
2016年 | 297篇 |
2015年 | 291篇 |
2014年 | 550篇 |
2013年 | 535篇 |
2012年 | 448篇 |
2011年 | 508篇 |
2010年 | 446篇 |
2009年 | 500篇 |
2008年 | 510篇 |
2007年 | 518篇 |
2006年 | 495篇 |
2005年 | 430篇 |
2004年 | 360篇 |
2003年 | 327篇 |
2002年 | 291篇 |
2001年 | 257篇 |
2000年 | 252篇 |
1999年 | 196篇 |
1998年 | 196篇 |
1997年 | 157篇 |
1996年 | 146篇 |
1995年 | 113篇 |
1994年 | 94篇 |
1993年 | 64篇 |
1992年 | 72篇 |
1991年 | 81篇 |
1990年 | 41篇 |
1989年 | 42篇 |
1988年 | 42篇 |
1987年 | 28篇 |
1986年 | 22篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有9806条查询结果,搜索用时 0 毫秒
1.
Knowledge of the vibrational properties of nanoparticles is of fundamental interest since it is a signature of their morphology, and it can be utilized to characterize their physical properties. In addition, the vibration characteristics of the nanoparticles coupled with surrounding media and subjected to magnetic field are of recent interest. This paper develops an analytical approach to study the radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to magnetic field. Based on Maxwell's equations, the nonlocal differential equation of radial motion is derived in terms of radial displacement and Lorentz's force. Bessel functions are used to obtain a frequency equation. The model is justified by a good agreement between the results given by the present model and available experimental and atomic simulation data. Furthermore, the model is used to elucidate the effect of nanoparticle size, the magnetic field and the stiffness of the elastic medium on the radial breathing-mode frequencies of several nanoparticles. Our results reveal that the effects of the magnetic field and the elastic medium are significant for nanoparticle with small size. 相似文献
2.
Back Cover: Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling (Chem. Eur. J. 8/2015) 下载免费PDF全文
3.
《Tetrahedron letters》2019,60(24):1582-1586
Rh(II)-catalyzed decomposition of certain cyclic α-diazocarbonyl compounds in the presence of cyclic ethers has been shown to give bicyclic ring expansion products. These are thought to arise from a [1,4]-alkyl shift toward the carbonyl oxygen atom and are in contrast with the recently observed spirocyclic products of a Stevens-type [1,2]-alkyl shift within the postulated oxonium ylide intermediate. Quantum chemical calculations performed at the B3LYP/6-31G* level of theory showed that the former reaction pathway (toward fused bicycles) is kinetically preferred. 相似文献
4.
5.
6.
R. J. Saykally K. M. Evenson D. A. Jennings L. R. Zink A. Scalabrin 《International Journal of Infrared and Millimeter Waves》1987,8(6):653-662
Twenty new cw FIR laser lines in CD3OH, optically pumped by a CO2 laser, are reported. The frequencies of 39 of the stronger laser lines were measured relative to stabilized CO2 lasers with a fractional uncertainty, as determined by the reproducibility of the FIR frequency itself, of 2 parts in 107.Contribution of the U.S. Government, not subject to copyright. 相似文献
7.
Jeannette H. C. Woerner 《商业与工业应用随机模型》2005,21(1):27-44
In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
8.
9.
J. -Ph. Jay J. Ben Youssef H. Le Gall 《Journal of magnetism and magnetic materials》2002,240(1-3):287-290
The dynamic response of trilayer magnetoresistive permalloy/Cu/Co films was studied by high-frequency permeability spectra measurements. The resonance frequency is shown to depend on the interlayer copper thickness. This dependence is related to exchange coupling between permalloy and cobalt and the interaction field is estimated using the Landau–Lifschitz–Gilbert model. 相似文献
10.