全文获取类型
收费全文 | 738篇 |
免费 | 178篇 |
国内免费 | 64篇 |
专业分类
化学 | 298篇 |
晶体学 | 13篇 |
综合类 | 4篇 |
数学 | 4篇 |
物理学 | 661篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 39篇 |
2019年 | 28篇 |
2018年 | 34篇 |
2017年 | 36篇 |
2016年 | 43篇 |
2015年 | 42篇 |
2014年 | 47篇 |
2013年 | 47篇 |
2012年 | 40篇 |
2011年 | 45篇 |
2010年 | 36篇 |
2009年 | 45篇 |
2008年 | 47篇 |
2007年 | 64篇 |
2006年 | 50篇 |
2005年 | 35篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 29篇 |
2001年 | 41篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 23篇 |
1997年 | 30篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有980条查询结果,搜索用时 31 毫秒
71.
72.
Er3+掺杂ZBLAN非晶的激发态频率上转换 总被引:3,自引:1,他引:2
非晶ZBLAN光纤玻璃中掺杂稀土离子Er3+的上转换发光的研究表明,在室温、大功率半导体激光器的激发下,Er3+的荧光主要是通过单离子步进双光子过程发生的,而其多光子过程虽然非常微弱,但在强的半导体激光的照射下也可产生.通过对这两种不同过程的实验测量,可以为进一步深入地研究上转换机制提供新的依据. 相似文献
73.
This paper presents an overview of the recent results on upconversion and photoluminescence of rare-earth ions in nanoenvironments.
The role of the rare-earth ion concentration, crystal size and crystal phase on the up and downconversion emission of rare-earth
ions in oxide nanocrystals and their underlying mechanisms are discussed. It is also found that the luminescence lifetime
of the excited state rare-earth ions is sensitive to the particle crystalline phase and size. The analysis suggests that the
modifications of radiative and nonradiative relaxation mechanisms are due to local symmetry structure of the host lattice
and crystal size respectively 相似文献
74.
本文报道了AgGaS_2晶体Ⅱ类非共线相位匹配Q开关Nd:YAG激光泵浦CO_2激光参量上转换研究结果,用迭代法计算了相位失配因子△K=0时的最佳非共线夹角.当泵浦功率密度为6MW/cm~2和晶体长度为4.7mm时,功率转换效率达16.1%,并且首次采用硅雪崩光电二极管接收和频信号. 相似文献
75.
应用基于Zernike多项式的波前探测和重构方法2,利用蒙特卡罗法,可求出探测器在不同的光子数下,其探测精度的变化。文章还给出了由不同的探测器组成的传感器,探测星等的变化情况。 相似文献
76.
Coherent spectroscopy of semiconductor quantum dots, such as photon echo, accumulated photon echo, interferometric coherency measurement, quantum beat and coherent phonon measurement, are reviewed in relation to the historical progress in the coherent spectroscopy of semiconductors. 相似文献
77.
The hard photon production from bremsstrahlung and annihilation with scattering that arise at two-loop level are estimated for a chemically non-equilibrated quark–gluon plasma in the framework of Hard Thermal Loop (HTL) resummed effective field theory. The rate of photon production is found to be suppressed due to unsaturated phase space compared to equilibrated plasma. For an unsaturated plasma, unlike the effective one-loop case, the reduction in the effective two-loop processes is found to be independent of gluon fugacity, due to an additional collinear enhancement arising from the decrease in thermal quark mass but strongly depends on quark and antiquark fugacities. It is also found that the photon production is dominated by bremsstrahlung mechanism, since the phase space suppression is higher for annihilation with scattering, in contrast to the equilibrated plasma where annihilation with scattering dominates the photon production. 相似文献
78.
79.
Summary An approach is presented to the study of laser-induced autoionization which usescomplex dressed states as a basis, instead of the commonly used Fano eigenstates. The complex dressed states are the eigenstates of an effective
Hamiltonian governing the equations of motion for the atomic probability amplitudes in the broad background assumption and
in the rotating frame at the laser frequency. The electron and photon spectra are described in terms of the eigenvalues associated
with the complex dressed states.
Riassunto Viene presentato un approccio allo studio dell'autoionizzazione indotta da laser che, al posto degli autostati di Fano, utilizza quale base una coppia distati vestiti complessi. Tali stati sono gli autostati di una hamiltoniana effettiva che governa le equazioni di moto per le ampiezze di probabilità atomiche in un sistema di riferimento ruotante alla frequenza del laser e nell'ipotesi di continuo largo. Gli spettri di elettroni e fotoni sono descritti in termini degli autovalori associati agli stati vestiti complessi.
Резюме Предлагается подход к исследованию автоионизации, индуцированной лазерным сильным полем, в котором используются, как, базис, комплексные “одетые” состояния, вместо обычных собственных состояний Фано. Комплексные “одетые” состояния представляют собственные состояния эффективного гамильтониана, определяющего уравнения движения для амплитуды вероятности атома во вращвющейся системе отсчета с лазерной частотой и в предположении широкого континуума. Электронные и фотонные спектры описываются в терминах собственных значений, связанных с комплексными “одетыми” состояниями.相似文献
80.
Aleksander Filip Żarnecki 《Pramana》2007,69(5):937-941
The CAIN simulation program was used to study the outgoing beam profile for the photon collider at ILC. The main aim of the
analysis was to verify the feasibility of the photon linear collider running with 20 mrad electron beam crossing angle. The
main problem is the distorted electron beam, which has to be removed from the interaction region. It is shown that with a
new design of the final dipole, it should be possible to avoid large energy losses at the face of the magnet.
相似文献