首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   26篇
  免费   0篇
  国内免费   3篇
化学   5篇
晶体学   1篇
物理学   23篇
  2015年   4篇
  2014年   1篇
  2013年   1篇
  2011年   3篇
  2010年   2篇
  2009年   1篇
  2008年   5篇
  2007年   1篇
  2006年   3篇
  2005年   1篇
  2004年   1篇
  2002年   1篇
  2001年   1篇
  1997年   1篇
  1996年   1篇
  1991年   1篇
  1987年   1篇
排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
2.
Raman spectra of xTeO2-(1−x)GeO2 (x=0, 0.2, 0.4, 0.6, 0.8 and 1) germanium tellurite glasses were measured and analyzed in an effort to follow the structural changes caused by mixing two typical glass formers. Systematic Raman intensity measurements have been performed in an effort to elucidate the composition induced structural changes and a possible mechanism accounting for these changes was proposed. The network structure of the glass is characterized by TeO4 trigonal bipyramid mixed with TeO3 trigonal pyramid units, while GeO4 tetrahedral units are also present. Changing the GeO2 content results in the conversion of the TeO4 units to TeO3 units with a neutral doubly bridged oxygen atom, while the existence of charged terminal oxygen atoms is questionable. The measured relative Raman intensities are semi-quantitatively correlated to the transformation of the TeO4 trigonal bipyramid to TeO3 trigonal pyramids.  相似文献   
3.
The interaction of iron (III) with pipemidic acid, Hpipem, afforded the complex [Fe (pipem) (HO)2 (H2O)]2. The new complex has been characterised by elemental analyses, infra-red, EPR and XPS spectroscopies. The monoanion, pipem, exhibits O, O ligation through the carbonyl and carboxylato oxygen atoms. Six coordinate dimer distorted octahedral configuration has been proposed for [Fe (pipem) (HO)2 (H2O)]2.  相似文献   
4.
本文报道用真空热蒸发法淀积的非晶态硒化镉薄膜作光敏介质制备超快光电导探测器。用对撞脉冲锁模Nd:YAG激光器产生的超短光脉冲序列对探测器的响应时间进行检测,结果表明a-CdSe薄膜对皮秒(10-12秒)级的超短光脉冲作用具有良好的瞬态响应光电特性,探讨a-CdSe薄膜快速弛豫过程的内在机理。  相似文献   
5.
In this study, experimental results are concerning “the optical bistability due to thermal lensing effect”, in colloidal solution of gold nanoparticles (Au Nps) which has been studied under CW laser illuminations. Two different CW laser beams (He–Ne and Nd-Yag) were used to interact with a vertical Fabry–Perot interferometer, containing colloid of the Au Nps. Hysteretic loops have been observed with regard to optical bistability and the results were fitted with theoretical curves. The radiated power to the resonator was elevated up to 50 mW for both the laser beams with the same spot size. Also, new method was defined to precise evaluation of the theoretical hysteretic loop which is describing the relation between nonlinear refractive index and the beam intensity inside the resonator. This dependency is due to thermal lensing effect and numerical simulations of this effect were also performed, in order to better understanding of it.  相似文献   
6.
NixZry(x:y=1∶2或2∶1)团簇的量子化学研究   总被引:3,自引:0,他引:3  
根据化学键理论和拓扑学原理,设计了非晶态团簇NixZry(x:y=1:2或2:1,x+y≤9)的几十种可能的构型,并应用量子化学从头算方法对它们的几何构型进行了优化,分析比较了这些构型的能量和稳定性。结果表明对于NixZry(x:y=1:2)低对称性的平面构型最稳定,而NixZry(x:y=2:1)三棱柱构型最稳定。这可能是由于两者外层价电子的数量差异所致:Zr仅有4价电子,较适宜配位数低的平面构型,而Ni(4s^23d^8),更适宜立体构型。  相似文献   
7.
The present paper reports sign inversion in dielectric anisotropy of a nematic liquid crystal, i.e. 5CB, as an effect of doping dye (solvent green 3) in small amount. It is the result of strong variation of the parallel component of dielectric permittivity with temperature for a dye doped sample. This behavior is attributed to the interaction taking place between the nematic liquid crystal molecule and the dye molecule. This behavior of dielectric anisotropy has been explained on the basis of interaction between the dye (guest) and the liquid crystal molecules (host).  相似文献   
8.
Synthesis and characterization of the structural and magnetic properties of a 2-line (2L) ferrihydrite (FHYD) sample based on the composition Fe:Al:Cu=100:25:5 are reported. Typical of 2L-FHYDs, this sample also yields the two broad lines in X-ray diffraction and triplet in the 1400-1700 cm−1 range in IR spectroscopy. However, in transmission electron microscopy, nanoflakes of about 5-20 nm size but without any hint of diffraction fringes characteristic of crystalline order were observed. Temperature dependence (2-380 K) of the magnetization M vs. applied field H (up to ±65 kOe) of this non-crystalline ferrihydrite is used to establish a blocking temperature TB?20 K, Néel temperature TN?365 K and a spin-glass ordering of the surface Fe3+ spins at TS?6 K. These magnitudes of TB and TS are considerably smaller than those of a 5 nm undoped 2L crystalline ferrihydrite with TB=70 K and TS=30 K. The fit of the M vs. H data for several T>TB to a modified Langevin function is shown to collapse onto a universal curve yielding a temperature-independent average magnetic moment μP=70(5)μB per nanoflake. Analysis of these parameters obtained from the fits of M vs. H data above TB is used to show that the effective average volume of the nanoflakes is about 1/3 that of spherical 5 nm crystalline 2L-FHYD. It is argued that these lower magnitudes of μP, TB, and TS for the nanoflakes result from their smaller effective volume determined here.  相似文献   
9.
The infrared (IR) photoluminescence (PL) emission of spark-processed silicon (sp-Si) was investigated. A broad and strong room temperature PL peak in the 945 nm (1.31 eV) spectral range was observed when sp-Si was excited with an argon laser. This peak is different from the PL commonly reported for anodically etched porous silicon and other silicon-based materials. The PL intensity increases substantially after annealing sp-Si between 350 and 500 °C in air after which it decreases again. The PL wavelength is observed to peak at 1010 nm by annealing sp-Si near 450 °C. It was further found that the most efficient PL occurs for a Si/O ratio of 0.3, for a small spark gap of about 1 mm, and for spark-processing times in the 15-60 min range.A model for the IR PL is proposed which mirrors that for visible PL. Specifically, it is proposed that the electrons which have been pumped by the laser from the ground state into a broad quasi-absorption band (or closely spaced absorption lines between 1.7 and 2.3 eV) revert back to lower IR levels at 1.31 eV by a non-radiative transition from where they revert radiatively to the ground state by emitting the observed 945 nm light.  相似文献   
10.
A microfabrication of ceramic materials with a low shrinkage has created inevitable demands in the fields of micro total analysis systems (μ-TAS) and microfluidic devices with thermal, chemical, and mechanical stability. In this study, nano-sized patterns were prepared using a soft lithographic technique, followed by the UV and thermal curation of a non-oxide SiCN preceramic polymer. The characterization of the thermal and mechanical properties of the cured preceramic polymer revealed that it becomes ceramic-like after the heat treatment at higher temperature than 600 °C. The heat-treated nano-sized patterns showed a low linear shrinkage as well as good chemical stability and optical properties. The results showed the feasibility of enormous potentials of the cured preceramic polymer because of the low shrinkage, the high optical transparency, and the thermal and chemical stability.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号