全文获取类型
收费全文 | 3274篇 |
免费 | 645篇 |
国内免费 | 220篇 |
专业分类
化学 | 1141篇 |
晶体学 | 26篇 |
力学 | 473篇 |
综合类 | 21篇 |
数学 | 398篇 |
物理学 | 2080篇 |
出版年
2024年 | 10篇 |
2023年 | 52篇 |
2022年 | 114篇 |
2021年 | 112篇 |
2020年 | 142篇 |
2019年 | 98篇 |
2018年 | 81篇 |
2017年 | 103篇 |
2016年 | 106篇 |
2015年 | 103篇 |
2014年 | 124篇 |
2013年 | 200篇 |
2012年 | 163篇 |
2011年 | 211篇 |
2010年 | 161篇 |
2009年 | 306篇 |
2008年 | 269篇 |
2007年 | 226篇 |
2006年 | 236篇 |
2005年 | 182篇 |
2004年 | 191篇 |
2003年 | 160篇 |
2002年 | 137篇 |
2001年 | 90篇 |
2000年 | 91篇 |
1999年 | 69篇 |
1998年 | 58篇 |
1997年 | 49篇 |
1996年 | 41篇 |
1995年 | 34篇 |
1994年 | 35篇 |
1993年 | 27篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4139条查询结果,搜索用时 15 毫秒
1.
In 1976 S. Hawking claimed that “Because part of the information about the state of the system is lost down the hole, the final situation is represented by a density matrix rather than a pure quantum state”. 1 This was the starting point of the popular “black hole (BH) information paradox”. 相似文献
2.
3.
沈有根 《中国科学A辑(英文版)》2002,45(3):400-408
Using the membrane model which is based on brick wall model, we calculated the free energy and entropy of Garfinkle-Horne dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy of Fermionic field have similar formulas. There is only a coefficient between them. 相似文献
4.
S. J. Cheng W. Sheng P. Hawrylak S. Raymond S. Studenikin A. Sachrajda Z. Wasilewski A. Babinski M. Potemski G. Ortner M. Bayer 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):211
We present results of calculations and experiments on electron–hole complexes in InGaAs/GaAs self-assembled quantum dots in high magnetic field (B). Due to hidden symmetries, the chemical potential of an N-exciton system at special B fields becomes insensitive to the exciton number as well as the magnetic field. This results in plateau regions of high intensity in measured magneto-PL spectrum. Theoretical calculations using exact diagonalization techniques successfully explain the measured magneto-photoluminescence spectrum with B fields up to 28 T. 相似文献
5.
We investigate the dynamics of the Λ system driven by two resonant laser fields in presence of dissipation for coupling strengths where the rotating‐wave approximation starts to break down. This regime is characterised by Rabi frequencies being approximately equal or smaller than the field frequencies. A systematic procedure to obtain an expansion for the solution of the Bloch evolution equations of the system is presented. The lowest contribution results to be the well‐known rotating‐wave approximation. The method is based on a semi‐classical treatment of the problem, and its predictions are interpreted fully quantum mechanically. The theory is illustrated by a detailed study of the disappearance of coherent population trapping as the intensities of the fields increase. 相似文献
6.
FJZ-250型高速分幅相机时间测量不确定度分析 总被引:2,自引:1,他引:1
FJZ-250型高速转镜分幅相机因转镜速度的不可重复性,光机结构的构造原理和控制系统各路高压触发时间的漂移,导致了时间测量的不确定度。为此,须对相机测量数据进行校正。阐述了校正方法、提供了逐幅校正位置误差的修正系数。若以预置转速对应的名义周期值去处理测量结果,则相机的时间测量合成小确定度将达1%,对名义周期值和名义幅间间隔时间值进行修正后,则可降至0.3%。 相似文献
7.
Kayll Lake 《General Relativity and Gravitation》2004,36(5):1159-1169
The norms associated with the gradients of the two non-differential invariants of the Kerr vacuum are examined. Whereas both locally single out the horizons, their global behavior is more interesting. Both reflect the background angular momentum as the volume of space allowing a timelike gradient decreases with increasing angular momentum becoming zero in the degenerate and naked cases. These results extend directly to the Kerr-Newman geometry. 相似文献
8.
Understanding the end state of black hole evaporation, the microscopic origin of black hole entropy, the information loss paradox, and the nature of the singularity arising in gravitational collapse - these are outstanding challenges for any candidate quantum theory of gravity. Recently, a midisuperspace model of quantum gravitational collapse has been solved using a lattice regularization scheme. It is shown that the mass of an eternal black hole follows the Bekenstein spectrum, and a related argument provides a fairly accurate estimate of the entropy. The solution also describes a quantized mass-energy distribution around a central black hole, which in the WKB approximation, is precisely Hawking radiation. The leading quantum gravitational correction makes the spectrum non-thermal, thus providing a plausible resolution of the information loss problem. 相似文献
9.
10.
Dong‐Guk Yu Jeong Ho An 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5608-5616
Ultrafine black particles, ranging in diameter from 1 to 3 μm, were prepared by dispersion polymerization in a methanol/water mixture with vinyl monomers, nonpolymerizable Sudan black B dyes, and fluorescein isothiocyanate labeled charge control additives. Both the ratio of the methanol to the water dispersion medium and the polymeric stabilizer concentration had significant effects on the particle size. The important role of the stabilizer concentration lay in the particle formation step, during which it determined the particle stability and final particle size. These could affect the extent of the aggregation of nuclei by changing the adsorption rate of the stabilizer and the viscosity of the dispersion medium, resulting in smaller particles. The fluorescent‐labeled charge control additives strongly affected the electrophoretic mobility. A small concentration of fluorescent‐labeled charge control additives increased the electrophoretic mobility. However, a further addition reduced the electrophoretic mobility of the polymer particles. The concentration dependence of the fluorescent‐labeled charge control additives on the deposition behavior in the polymer particles was successfully imaged and thereafter quantified by image analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5608–5616, 2004 相似文献