全文获取类型
收费全文 | 280篇 |
免费 | 292篇 |
国内免费 | 31篇 |
专业分类
化学 | 12篇 |
晶体学 | 2篇 |
数学 | 26篇 |
物理学 | 563篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 13篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 21篇 |
2007年 | 19篇 |
2006年 | 35篇 |
2005年 | 38篇 |
2004年 | 53篇 |
2003年 | 25篇 |
2002年 | 27篇 |
2001年 | 29篇 |
2000年 | 40篇 |
1999年 | 33篇 |
1998年 | 16篇 |
1997年 | 22篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有603条查询结果,搜索用时 0 毫秒
551.
This paper reports on the photoluminescence spectra of ZnSe single crystal with
trace chlorine excited by the femtosecond laser pulse. Three emission bands,
including second-harmonic-generation, two-photon-excited peak and a broad band at
500--700nm, were detected. The thermal strain induced by femtosecond pulse strongly
influences the photoluminescence of ZnSe crystal. The corresponding strain \va in
ZnSe crystal is estimated to be about 8.8 \ti10-3 at room temperature. The
zinc-vacancy, as the main point defect induced by femtosecond pulse, is successfully
used to interpret the broad emission at 500--700nm. The research shows that
self-activated luminescence possesses the recombination mechanism of donor--vacancy
pair, and it is also influenced by a few selenium defects and the temperature. The
rapid decrease in photoluminescence intensity of two-photon-excited fluorescence and
second-harmonic generation emission at lower temperature is attributed to the fact
that more point defects result in the thermal activation of the two-photo-absorption
energy converting to the stronger recombination emission of chlorine--zinc vacancy
in 500--700nm. The experimental results indicate that the femtosecond exciting
photoluminescence shows a completely different emission mechanism to that of He--Cd
exciting luminescence in ZnSe single crystal. The femtosecond laser exhibits a
higher sensitive to the impurity in crystal materials, which can be recommended as
an efficient way to estimate the trace impurity in high quality crystals. 相似文献
552.
通过用单电子近似求解含时薛定谔方程,用加窗傅里叶分析的方法,分析了单原子产生的高次谐波的时间特性。理论分析表明,基态粒子数消耗对不同级次谐波辐射的影响程度不一样;谐波辐射随着入射激光场强度的增加会出现饱和;随着谐波级次的增加,波辐射越来越趋向于集中在更短的时间间隔内,相应的线宽胡着谐波级次的增加而增加。 相似文献
553.
554.
555.
The high backing pressure argon gases adiabatically expand into vacuum through a pulsed gas jet to nucleate into large clusters. The clusters were heated by a 45fs, 2.3×1016 Wcm-2 Ti: sapphire laser. The high energy of the ions produced in the cluster explosion was measured using time-of-flight spectrometry. The maximum and average kinetic energy of the ions were 0.2MeV and ~12.5keV, respectively, indicating that the femtosecond laser interactions with argon clusters are more energetic than interactions with atoms and molecules. 相似文献
556.
An ultrafast electron diffraction technique with both high temporal and spatial resolution has been shown to be a powerful tool to observe the material transient structural change on an atomic scale.The space charge forces in a multi-electron bunch will greatly broaden the electron pulse width,and therefore limit the temporal resolution of the high brightness electron pulse.Here in this work,we design an ultrafast electron diffraction system,and utilize a radio frequency cavity to realize the ultrafast electron pulse compression.We experimentally demonstrate that the stretched electron pulse width of14.98 ps with an electron energy of 40 keV and the electron number of 1.0 ×10~5 can be maximally compressed to about0.61 ps for single-pulse measurement and 2.48 ps for multi-pulse measurement by using a 3.2-GHz radiofrequency cavity.We also theoretically and experimentally analyze the parameters influencing the electron pulse compression efficiency for single-and multi-pulse measurements by considering radiofrequency field time jitter,electron pulse time jitter and their relative time jitter.We suggest that increasing the electron energy or shortening the distance between the compression cavity and the streak cavity can further improve the electron pulse compression efficiency.These experimental and theoretical results are very helpful for designing the ultrafast electron diffraction experiment equipment and compressing the ultrafast electron pulse width in a future study. 相似文献
557.
558.
559.
类锂钙和钾离子X射线激光的实验研究 总被引:1,自引:0,他引:1
探索进入“水窗”波段以寻求X射线激光在近期的科学技术应用,是当前实验室X射光线激研究的一个重要目标.采用复合泵浦方案,我们曾用较低的驱动激光功率首次实现了类锂硅离子5f—3d(8.884nm),5d—3p(8.728nm)跃迁软X射线激光,并第一次发现了类锂硅离子的6f—3d(7.583nm)和6d—3p(7.464nm)新的X射线激光跃迁.最近,我们进一步完成了线聚焦激光辐照CaF_2和KCl平板靶的实验,探索了沿类锂离子等电子数序,将软X射线激光推进至更短波长的现实可能性,实现了类锂钙和类锂钾4f—3d跃迁的软X射线激光,波长分别为5.77nm和6.47nm,增益系数分别达到4.3cm~(-1)和1.6cm~(-1).同时也观察到了类氢氟Hα(8.09 nm)的增益,增益系数为1.4cm~(-1).实验结果进一步显示了复合泵浦类锂离子方案在实现更短波长X射线激光方面的潜力. 相似文献
560.
在线状聚焦激光辐照平面靶及柱形细丝靶的实验中,我们首次观察到线聚焦激光在等离子体中分裂成丝与等离子体的小尺度喷流结构,这些现象有可能构成当今以激光产生的等离子体为放大介质的X射线激光实验研究中的一类应设法克服的障碍. 相似文献