全文获取类型
收费全文 | 2662篇 |
免费 | 1169篇 |
国内免费 | 162篇 |
专业分类
化学 | 50篇 |
晶体学 | 28篇 |
力学 | 124篇 |
综合类 | 31篇 |
数学 | 103篇 |
物理学 | 3657篇 |
出版年
2024年 | 24篇 |
2023年 | 93篇 |
2022年 | 106篇 |
2021年 | 113篇 |
2020年 | 74篇 |
2019年 | 100篇 |
2018年 | 44篇 |
2017年 | 92篇 |
2016年 | 82篇 |
2015年 | 115篇 |
2014年 | 280篇 |
2013年 | 148篇 |
2012年 | 193篇 |
2011年 | 212篇 |
2010年 | 158篇 |
2009年 | 239篇 |
2008年 | 307篇 |
2007年 | 253篇 |
2006年 | 175篇 |
2005年 | 160篇 |
2004年 | 173篇 |
2003年 | 125篇 |
2002年 | 113篇 |
2001年 | 107篇 |
2000年 | 84篇 |
1999年 | 72篇 |
1998年 | 49篇 |
1997年 | 53篇 |
1996年 | 41篇 |
1995年 | 41篇 |
1994年 | 25篇 |
1993年 | 19篇 |
1992年 | 32篇 |
1991年 | 24篇 |
1990年 | 27篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
排序方式: 共有3993条查询结果,搜索用时 31 毫秒
31.
In-situ energy dispersive x-ray diffraction on ZnS nanocrystalline was carried out under high pressure by using a diamond anvil cell. Phase transition of wurtzite of 10nm ZnS to rocksalt occurred at 16.0GPa, which was higher than that of the bulk materials. The structures of ZnS nanocrystalline at different pressures were built by using materials studio and the bulk modulus, and the pressure derivative of ZnS nanocrystalline were derived by fitting the equation of Birch-Murnaghan. The resulting modulus was higher than that of the corresponding bulk material, which indicates that the nanomaterial has higher hardness than its bulk materials. 相似文献
32.
两步相移实现投影栅相位测量轮廓术 总被引:9,自引:2,他引:7
提出一种新的投影栅相位测量方法--两步相移法。该方法只需两幅相移条纹图,因此计算量小,速度快。给出了实验及计算结果,并同四步相移法进行了比较,证明了该方法具有较高的精度。 相似文献
33.
34.
35.
36.
The transition from the phase-unlocking state to the phase-locking state is found at the desynchronization of synchronous chaos of coupled oscillators.In the phase-locking case,the motions of all oscillators are chaotic and desynchronized,however spatial ordering is identified in their phase distribution. 相似文献
37.
P. Xu Shining Zhu 《量子光学学报》2006,12(B08):85-85
An intense comb-shaped Raman spectra were obtained from a two-dimensional nonlinear x(2) photonic crystal - a hexagonally poled LiTaO3 crystal with lattice parameter 9 micros. The lowest Raman shift was down to 2 cm^-1 and the order of anti-stokes and stokes signals both achieved 11. The novel Raman spectra were mediated first by intense phonon-polariton fields, which were driven through the quasi-phase-matched coupling between the incident dual-beam both from an optical parametric oscillation laser, and further amplified greatly also by such quasi-phasematched nonlinear optical process. The dependence of the Raman spectra character on the wavelength and intensity of incident beams were studied in detail, which accordingly revealed information of the inelastic scattering and the elementary excitation in the nonlinear medium. These results on the other hand suggest technological importance for developing a novel Raman laser with the multi-wavelength output and a tunable frequency interval and for possible applications in quantum optics. 相似文献
38.
39.
教学研究:介绍量子力学几个基本概念——兼答《关于量子几何相位的评注》中的几个主要问题 总被引:4,自引:4,他引:0
介绍了量子绝热定理的物理含义及成立的条件,认为有关主要献(Aharonov-Anandan,Bohm,孙昌璞等)的表述是正确的,而《关于量子几何相位的评注》^[1](以下简称《评注》)相应的表述不完全正确。在此基础上,认为这些献和教材(R.Shankar)得出的涉及Berry绝热相位的一些论述(不含Berry绝热相因子的瞬时能量本征态不满足含时Schroedinger方程等)也是正确的,而《评注》的论述与此相反。《评注》认为只有γn(C)才是Berry相位。本作则倾向于把γn(t)叫做Berry绝热相位,而把γn(C)=γn(T)-γn(0)叫做几何相位(geometric phase)^[2]。 相似文献
40.
Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3 下载免费PDF全文
We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485-1553nm signal wave and 3383-3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal. 相似文献