全文获取类型
收费全文 | 499篇 |
免费 | 117篇 |
国内免费 | 84篇 |
专业分类
化学 | 446篇 |
晶体学 | 21篇 |
力学 | 3篇 |
综合类 | 2篇 |
数学 | 1篇 |
物理学 | 227篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 29篇 |
2021年 | 25篇 |
2020年 | 30篇 |
2019年 | 19篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 28篇 |
2015年 | 30篇 |
2014年 | 20篇 |
2013年 | 62篇 |
2012年 | 32篇 |
2011年 | 28篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 35篇 |
2006年 | 28篇 |
2005年 | 18篇 |
2004年 | 27篇 |
2003年 | 22篇 |
2002年 | 25篇 |
2001年 | 17篇 |
2000年 | 21篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
排序方式: 共有700条查询结果,搜索用时 0 毫秒
81.
对在掺杂稀土离子晶体中实现电磁感应光透明进行了实验研究。首先,以Er3+∶YAG晶体为样品,用旋转波近似下的密度矩阵方程理论计算了探测场的吸收特性随Er3+离子浓度的变化规律,结果表明:在探测场失谐Δp=0时,形成了一个对于探测光透明的窗口,从而在理论上论证了在掺杂稀土离子晶体中实现电磁感应光透明效应的可行性。设计了一个以Pr3+∶Y2SiO5晶体为样品的实验激发方案,吸收光谱显示,当温度为6 K时其在共振吸收峰处可形成一个完全透明的窗口,实现了在掺杂离子晶体中的电磁感应光透明。实验还分析了工作温度、耦合场失谐对探测光透过率的影响,结果显示:当样品温度上升到15 K时,透明窗口消失;耦合场的失谐量越大,透射率越小。 相似文献
82.
《Physics letters. A》2020,384(17):126373
Based on first-principles calculations, the structural stability and temperature effect in ScX (X=S, Se and Te) compounds are studied with three typical structures of B1 (NaCl-type), hcp (NiAs-type) and β-hcp (inverse Li2O2-type). Their dynamic stability has been verified using phonon mode analysis and molecular dynamics simulations. From the total energy calculations, we find that the most stable ground state structures are B1 for ScS, and hcp for ScSe and ScTe, respectively. Moreover, structural stabilities at finite temperature are studied with the combination of phonon dependent dynamics analysis and first-principles calculations, which reveals a phase transition from hcp to B1 in ScSe around 230 K and a phase transition from hcp to β-hcp in ScTe around 460 K, in accordance with experimental findings. The energy barrier and pathway along the phase transformation from hcp to β-hcp ScTe are also calculated and analyzed by the solid-state nudged elastic band method. 相似文献
83.
84.
The sums over states of the atoms and singly and doubly charged ions of rare-earth elements that are required for a theoretical study of thermochemical processes in high-temperature plasma spectral sources are calculated in the temperature range 2500–12,000 K. 相似文献
85.
Rare-earth doped fibers suffer from relatively high attenuation in comparison to conventional communication fibers. In order to improve the properties of such fibers, understanding of the mechanisms involved in scattering effects is of great importance. The effect of Nd-doping, Al-codoping and of the drawing temperature on the scattering effect was investigated for several different optical fibers. To this end a measuring setup was realized which allows absolute measurements of the scattering coefficient at different positions along a fiber. Also separation of total attenuation and scattering effects is possible. The presented results indicate scattering effects as primary source for increased attenuation compared with undoped fibers. 相似文献
86.
Alexander A. Kaminskii Ludmila Li Andre V. Butashin Vladimir S. Mironov Alexsei A. Pavlyuk Sergey N. Bagayev Ken-ichi Ueda 《Optical Review》1997,4(2):309-315
Monoclinic KY(WO4)2:Pr3+, Tm3+:KY(WO4)2:Er3+, Yb3+ single crystals are grown by low-gradient Czochralski technique. Stimulated emission at 1.0223μm wavelength in the new lasing 1D2→3F3 channel of Pr3+ ions in KY(WO4)2 at room temperature under Xe-flashlamp pumping is excited. Full sets of Stark-level energies for Pr3+ ions in KY(WO4)2 and KGd(WO4)2 crystals at 77 K are determined. 4f2-4f2 intensity-transitions for the KY(WO4)2:Pr3+ are analyzed preliminarily. All observed at present and earlier one-micron Pr3+-ion, induced transitions in the 1D2→3F3 and 1D2→3F4 channels are identified. In yttrium and gadolinium sensitized-tungstates a two-micron (3H4→3H6) low-threshold generation of Tm3+ ions at cryogenic temperatures is achieved.All authors cooperate with the Joint Open Laboratory for Laser Crystals and Precise Laser Systems at the Institute of Crystallography and Institute of Laser Physics, Russian Academy of Sciences. 相似文献
87.
Solution‐Based Synthesis of Layered Intergrowth Compounds of the Homologous PbmBi2nTe3n+m Series as Nanosheets 下载免费PDF全文
Arindom Chatterjee Dr. Kanishka Biswas 《Angewandte Chemie (International ed. in English)》2015,54(19):5623-5627
Layered intergrowth compounds in the homologous PbmBi2nTe3n+m family are interesting because they are examples of natural heterostructures. We present a simple solution‐based synthesis of two‐dimensional nanosheets of PbBi2Te4, Pb2Bi2Te5, and PbBi6Te10 layered intergrowth compounds, which are members of the PbmBi2nTe3n+m [that is, (PbTe)m(Bi2Te3)n] homologous series. Few‐layer nanosheets exhibit narrow optical band gaps (0.25–0.7 eV) with semiconducting electronic‐transport properties. 相似文献
88.
Recent advances in the applications of transition metal chalcogenides/graphene (TMC/graphene) nanocomposites in future energy storage and conversion are reviewed. The synthesis processes and structures of TMC/graphene, workingpriciple of evergy energy device, and the electrochemical performances are summarized. 相似文献
89.
《Angewandte Chemie (International ed. in English)》2017,56(42):12946-12951
Despite impressive recent advances in the synthesis of lead chalcogenide solid nanoparticles, there are no examples of lead chalcogenide hollow nanoparticles (HNPs) with controlled diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with their complexity, inability to precisely control the dimensions, and limited possibilities with regard to applicable materials. Herein, we report on an unconventional strategy for crafting uniform lead chalcogenide (PbS and PbTe) HNPs with tailorable size, surface chemistry, and near‐IR absorption. Amphiphilic star‐like triblock copolymers [polystyrene‐block‐poly(acrylic acid)‐block‐polystyrene and polystyrene‐block‐poly(acrylic acid)‐block‐poly(3,4‐ethylenedioxythiophene)] were rationally synthesized and exploited as nanoreactors for the formation of uniform PbS and PbTe HNPs. Compared to their solid counterparts, the near‐IR absorption of the HNPs is blue‐shifted owing to the hollow interior. This strategy can be readily extended to other types of intriguing low‐band‐gap HNPs for diverse applications. 相似文献
90.