全文获取类型
收费全文 | 532篇 |
免费 | 157篇 |
国内免费 | 23篇 |
专业分类
化学 | 43篇 |
晶体学 | 50篇 |
力学 | 1篇 |
综合类 | 2篇 |
数学 | 3篇 |
物理学 | 613篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 21篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 41篇 |
2012年 | 28篇 |
2011年 | 37篇 |
2010年 | 35篇 |
2009年 | 35篇 |
2008年 | 29篇 |
2007年 | 34篇 |
2006年 | 50篇 |
2005年 | 30篇 |
2004年 | 39篇 |
2003年 | 22篇 |
2002年 | 45篇 |
2001年 | 12篇 |
2000年 | 45篇 |
1999年 | 15篇 |
1998年 | 16篇 |
1997年 | 20篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有712条查询结果,搜索用时 288 毫秒
71.
测量了不同阱宽In0.2Ga0.8As/GaAs单量子阱的PL谱的峰值波长和荧光谱线半峰全宽随温度的变化。利用Varshni公式对实验峰值波长进行拟合,得到了新的参数。结果表明,无位错应变量子阱带隙仍具有其体材料的特性:荧光谱线半峰全宽随温度升高迅速展宽,这主要归因于声子关联作用增强和激子热离化为自由载流子所致;阱宽越窄荧光峰值能量越高,将其与量子尺寸效应的理论计算结果进行了比较。文中还考察了谱线半峰全宽和阱宽的关系,利用合金无序对这一现象进行了解释。 相似文献
72.
73.
74.
M. Karl D. RülkeT. Beck D.Z. HuD.M. Schaadt H. KaltM. Hetterich 《Superlattices and Microstructures》2010
Pyramidal micro-cavities represent a novel promising class of semiconductor optical cavities. In contrast to our previous approach based on pyramids sitting on distributed Bragg reflectors, we investigate reversed freestanding GaAs pyramids. The latter are achievable by a wet-chemical etching process where an AlAs sacrificial layer in the epitaxially grown layer structure is used. In freestanding GaAs pyramids, light is simply confined by total internal reflection at the interface of the high refractive index material GaAs to the surrounding. Due to strong optical confinement within the pyramidal shape, small mode volumes are expected. Quality factors up to 3000 were measured in first structures. However, simulations suggest the possibility of much higher values. Therefore, these freestanding pyramids are promising for an optimized ratio between quality factor and mode volume, which is crucial for quantum-optical applications. 相似文献
75.
Á. Nemcsics L. Tóth L. Dobos Ch. Heyn A. Stemmann A. Schramm H. Welsch W. Hansen 《Superlattices and Microstructures》2010
Self-assembled strain-free quantum dot (QD) structures were grown on AlGaAs surface by the droplet epitaxal method. The QDs were developed from pure Ga droplets under As pressure. The QDs were investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Both techniques show that the QDs are very uniform in size and their distribution on the surface is also homogeneous. The high resolution cross-sectional TEM investigation shows perfect lattice matching between the QD and the substrate, and also the faceting of the side walls of QD can be identified exactly by lattice planes. Analytical TEM (elemental mapping by EELS) unambiguously identifies the presence of Al in the QD. 相似文献
76.
Properties of as prepared or nanoengineered III-V semiconductor surfaces provide attractive means for photonic detection of different adsorbants from surrounding gaseous or liquid environments. To be practical, this approach requires that the surface is made selectively sensitive (functionalized) to targeted species. In addition, such surface has also to stay stable over extended period of time to make it available for rapid testing. Numerous reports demonstrate attractive properties of GaAs for sensing applications. One of the most fundamental issues relevant to these applications concerns the ability to functionalize chemically, or biologically, the surface of GaAs. The most studied method of GaAs surface functionalization is based on formation of self-assembled monolayers (SAMs) of various n-alkanethiols, HS-(CH2)n-T (T = CH3, COOH, NH2, etc.). In spite of multi-year research concerning this issue, it has only been recently that a comprehensive picture of SAMs formation on GaAs and an understanding of the natural limitation of the SAM-GaAs interface in some bio-chemical sensing architectures has begun to emerge. 相似文献
77.
Photoluminescence (PL) analysis is used to study porous layers elaborated by electrochemical etching of n+ Si-doped GaAs substrate with different etching times. Temperature and power dependence photoluminescence (PL) studies were achieved to characterize the effect of the etching time on the deep levels of the n+ Si-doped GaAs. The energy emission at about 1.46 eV is attributed to the band-to-band (B-B) (e-h) recombination of a hole gas with electrons in the conduction band. The emission band is composed of four deep levels due to the complex of (VAsSiGaVGa), a complex of a (Ga vacancy - donor - As vacancy), a (SiGa-VGa3−) defect or Si clustering, and a (gallium antisite double acceptor-effective mass donor pair complex) and which peaked, respectively, at about (0.94, 1, 1.14, and 1.32 eV). The PL intensity behavior as function of the temperature is investigated, and the experimental results are fitted with a rate equation model with double thermal activation energies. 相似文献
78.
79.
氩、氢混合等离子体处理对GaAs表面性质及发光特性的影响 总被引:1,自引:0,他引:1
介绍了一种氩、氢混合等离子体清洗GaAs基片的实验工艺,深入研究了氩、氢等离子体清洗GaAs表面污染物和氧化层,并活化表面性能的基本原理,同时讨论了气体流量、溅射功率和清洗时间等不同溅射参数对等离子体清洗效果的影响。结果表明,在氩气和氢气流量分别为10 cm3/min和30 cm3/min,溅射功率为20 W,清洗时间为15 min的条件下,GaAs样品的光致发光强度提高达139.12%,样品表面的As-O键和Ga-O键基本消失。 相似文献
80.
在有效质量近似下利用打靶法求出Ga1-xInxNyAs1-y/GaAs量子阱中的本征能级En, 并通过费米黄金规则计算电子-LO声子由第一激发态到基态的散射率和平均散射率随温度、阱宽以及氮(N)和铟(In)组分变化的规律. 计算结果表明: 在In 组分恒定的情况下, 随着N组分的增加, 散射率和平均散射率增加; 在N组分恒定的情况下, 随着In组分的增加, 散射率和平均散射率减小; 随着温度的增加, 在温度较低时散射率和平均散射率随温度的增加变化不大, 在温度较高时随温度的增加而增加; 随着阱宽的增加, 散射率和平均散射率都是先增加到一个最大值, 然后再减小, 最大值出现在阱宽200 Å附近. 计算结果对Ga1-xInxNyAs1-y/GaAs量子阱在光电子器件应用方面有一定的指导意义.
关键词:
费米黄金规则
1-xInxNyAs1-y/GaAs量子阱')" href="#">Ga1-xInxNyAs1-y/GaAs量子阱
LO声子
散射率 相似文献