全文获取类型
收费全文 | 1982篇 |
免费 | 140篇 |
国内免费 | 1篇 |
专业分类
化学 | 1452篇 |
晶体学 | 6篇 |
力学 | 34篇 |
数学 | 219篇 |
物理学 | 412篇 |
出版年
2024年 | 8篇 |
2023年 | 23篇 |
2022年 | 67篇 |
2021年 | 85篇 |
2020年 | 74篇 |
2019年 | 107篇 |
2018年 | 103篇 |
2017年 | 78篇 |
2016年 | 131篇 |
2015年 | 94篇 |
2014年 | 97篇 |
2013年 | 137篇 |
2012年 | 134篇 |
2011年 | 165篇 |
2010年 | 99篇 |
2009年 | 72篇 |
2008年 | 110篇 |
2007年 | 107篇 |
2006年 | 106篇 |
2005年 | 84篇 |
2004年 | 60篇 |
2003年 | 48篇 |
2002年 | 45篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
For the first time a comparative study of holographic recording in planarly oriented films of nematic and cholesteric azobenzene-containing polymers was performed. The influence of temperature and light intensity on the values of diffraction efficiencies of holographic gratings was investigated. The kinetics of grating relaxation at different temperatures was studied. It was shown that the helical supramolecular structure of cholesteric copolymer causes a significant decrease of the diffraction efficiency in comparison with the one observed for the nematic state of the homopolymer. 相似文献
6.
Alexey Yurasov Alexander Granovsky Sergey Tarapov Jean-Pierre Clerc 《Journal of magnetism and magnetic materials》2006
The transmission of millimeter-range electromagnetic waves (30–50 GHz) through a magnetic nanocomposite thin film exhibiting tunnel magnetoresistance (TMR) is calculated. The relative change of transmission coefficient in an applied magnetic field due to the magnetorefractive effect is approximately linear with TMR and strongly depends on nanocomposite resistivity and film thickness. The obtained results are in a good agreement with experiment. 相似文献
7.
Vladimir B. Arion Alexey A. Nazarov Christian G. Hartinger Gerald Giester Bernhard K. Keppler 《应用有机金属化学》2003,17(9):723-724
For the unsymmetrical title compound, 1‐bromo‐1′‐[(2S)‐N‐(1‐hydroxy‐3‐methylbutane‐2‐yl)]‐ferroceneamide, two independent molecules were found in the asymmetric unit. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
8.
9.
Kaledin AL 《The Journal of chemical physics》2005,122(18):184106
A formulation of a direct, iterative method for obtaining the lowest eigenvalues and eigenvectors of a Hessian matrix is presented. Similar to the iterative schemes in electronic structure configuration interaction calculations (methods due to Lanczos, Davidson, and others), the mass-weighted Hessian matrix K is not constructed explicitly; instead, its operation on a basis vector (a direction in the 3N Cartesian configuration space of the atoms) is computed based on the principles of dynamical equations of motion. By noting that the time derivative of the gradient vector in the harmonic force field is related to the particles' momenta via dg/dt = Kp, a Hessian-vector product can be computed on the fly by finite differentiation of the gradient along the direction specified by the p vector. Thus, only two evaluations of the gradient are required per Davidson-like iteration per root, which leads to a linear scaling behavior of the computational effort with the number of atoms (provided that the evaluation of the gradient scales linearly). Preliminary results are presented for a 27,000-atom 4He nanodroplet. 相似文献
10.
Dr. Alexey S. Kiryutin Mikhail S. Panov Dr. Alexandra V. Yurkovskaya Prof. Dr. Konstantin L. Ivanov Prof. Dr. Geoffrey Bodenhausen 《Chemphyschem》2019,20(5):766-772
A study of long-lived spin order in chlorothiophene carboxylates at both high and low magnetic fields is presented. Careful sample preparation (removal of dissolved oxygen in solution, chelating of paramagnetic impurities, reduction of convection) allows one to obtain very long-lived singlet order of the two coupled protons in chlorothiophene derivatives, having lifetimes of about 130 s in D2O and 240 s in deuterated methanol, which are much longer than the T1-relaxation times (18 and 30 s, respectively, at a field =9.4 T). In protonated solvents the relaxation times become shorter, but the lifetime is still substantially longer than . In addition, long-lived coherences are shown to have lifetimes as long as 30 s. Thiophene derivatives can be used as molecular tags to study slow transport, slow dynamics and slow chemical processes, as has been shown in recent years. 相似文献