全文获取类型
收费全文 | 69篇 |
免费 | 6篇 |
专业分类
化学 | 36篇 |
晶体学 | 5篇 |
力学 | 5篇 |
数学 | 10篇 |
物理学 | 19篇 |
出版年
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 1篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 3篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有75条查询结果,搜索用时 15 毫秒
21.
Ravindra P. Singh Sanjoy Roychowdhury Virendra K. Jaiswal 《Optics Communications》2007,274(2):281-285
Before we use an optical vortex for any application, it is important to know if the vortex is axial or non-axial, since properties of one type of the vortex are quite different from another. We show that the Wigner distribution can provide a solution, being different for axial and non-axial vortex. We use transport properties of the Wigner function to study the propagation of an axial as well as non-axial vortex and find them different. 相似文献
22.
Tailoring of Electronic Structure and Thermoelectric Properties of a Topological Crystalline Insulator by Chemical Doping 下载免费PDF全文
Subhajit Roychowdhury Dr. U. Sandhya Shenoy Prof. Dr. Umesh V. Waghmare Dr. Kanishka Biswas 《Angewandte Chemie (International ed. in English)》2015,54(50):15241-15245
Topological crystalline insulators (TCIs) are a new quantum state of matter in which linearly dispersed metallic surface states are protected by crystal mirror symmetry. Owing to its vanishingly small bulk band gap, a TCI like Pb0.6Sn0.4Te has poor thermoelectric properties. Breaking of crystal symmetry can widen the band gap of TCI. While breaking of mirror symmetry in a TCI has been mostly explored by various physical perturbation techniques, chemical doping, which may also alter the electronic structure of TCI by perturbing the local mirror symmetry, has not yet been explored. Herein, we demonstrate that Na doping in Pb0.6Sn0.4Te locally breaks the crystal symmetry and opens up a bulk electronic band gap, which is confirmed by direct electronic absorption spectroscopy and electronic structure calculations. Na doping in Pb0.6Sn0.4Te increases p‐type carrier concentration and suppresses the bipolar conduction (by widening the band gap), which collectively gives rise to a promising zT of 1 at 856 K for Pb0.58Sn0.40Na0.02Te. Breaking of crystal symmetry by chemical doping widens the bulk band gap in TCI, which uncovers a route to improve TCI for thermoelectric applications. 相似文献
23.
Vijayan T. Roychowdhury P. Iyyengar S.K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(2):199-204
An intense beam is not propagated in vacuum because of its space charge. In this work, an intense electron beam of 250 keV, 6 kA, 80 ns is propagated after initial collimation inside a short length of dielectric tube and further confinement provided by ions attributed to beam irradiation. Such beams have important potential in particle beam and controlled fusion research. It is seen that electrons are slowed down to the ion velocity, while ions are collectively accelerated by the beam space-charge. Collimator geometry is varied for space-charge control. Elongation of the beam pulse width to 100-300 ns is observed depending on propagation distance. Explanations are presented through physical model and scaling laws 相似文献
24.
A study is conducted to investigate forced convective flow and heat transfer over a bank of staggered cylinders. Using a novel numerical formulation based on a non‐orthogonal collocated grid in a physical plane, the effects of Reynolds number and cylinder spacing on the flow and heat transfer behaviour are systematically studied. It is observed that both the Reynolds number and cylinder spacing influence the recirculatory vortex formation and growth in the region between the cylinders; in turn, the rates of heat transfer between the fluid and the staggered cylinders are affected. As the cylinder spacing decreases, the size and length of eddies reduce. For sufficiently small spacings, eddy formation is completely suppressed even at high Reynolds number. Pressure drop and Nusselt number predictions based on numerical study are in excellent agreement with available correlations. The study provides useful insight on the detailed flow and heat transfer phenomena for the case of a bank of staggered cylinders. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
25.
26.
A phase/amplitude mask on the aperture of an imaging system results in a pupil function that is multiplicative with the lens function, resulting in a morphological transformation of the imaging wavefront. It was shown that such amplitude and phase functions can be implemented using polarization masks, with the advantage that the phase and amplitude can be controlled in real time and in some cases, independently of each other. The phase and amplitude variation over the mask can be controlled either by changing the polarization of the mask or by changing the input beam parameters. Wavefront tailoring using polarization-masked apertures is therefore feasible and may be utilized for focal shift and partial aberration compensation. For complete compensation of aberration, the phase distribution over the mask should be conjugate to that of the phase error of the aberrant wavefront, which necessitates the use of a continuously variable polarization mask. Since such a mask is difficult to implement, we have considered polarizing masks consisting of discrete polarized zones on the lens aperture, leading to polarization phase steps on the exit pupil of the imaging system. The simulation results presented in this paper show that effects of focal shift, partial compensation of primary spherical aberration and astigmatism can indeed be achieved by the proper use of polarization masked apertures. 相似文献
27.
Mrinal Kanti Roychowdhury 《Israel Journal of Mathematics》2012,192(1):473-488
The quantization dimension function for a probability measure supported on the limit set generated by a set of contractive bi-Lipschitz mappings is determined. The relationship between the quantization dimension function and the temperature function of the thermodynamic formalism arising in multifractal analysis is established. 相似文献
28.
Benzo[a]pyrene is a carcinogen often present in diesel. For pervaporative removal of benzo[a]pyrene from n-tetradecane, representing a model diesel composition, both conventional as well as statistically designed experimental methods have been carried out. The effect of membrane composition, thickness, the effect of membrane pretreatment time and operating temperature on pervaporative separation have been investigated by response surface methodology, RSM for efficient permeation of target compound. The suitable membrane has been further used to study the effect of different physico-chemical parameters on permeation conventionally. RSM has also been applied to optimize the operational conditions of pervaporation process to maximize the response, i.e., the pervaporation separation index. With the design of experiments, the quadratic response surface models have been developed to link the response with input variables via mathematical relationships. The maximum value of Pervaporation Separation Index obtained is 1.9654 kg m?2 h?1. The optimized process condition’s run time is 10.79 h, the feed PAH concentration is 166.34 ppm with a permeate side pressure of 0.73 mmHg and an operating temperature of 451.25 K. 相似文献
29.
Blends prepared by melt mixing of thermoplastic elastomer have gained considerable attention in recent years from a heat shrinkability point of view. Our present study deals with the measurement of heat shrinkability of the maleic anhydride grafted low‐density polyethylene and ethylene acrylic elastomer. Two samples have been prepared to study the effect of coupling agent's reactivity on the shrinkability of the blends. The coupling agents used are 4,4′‐diamino diphenyl sulphone, and 4,4′‐diamino diphenyl methane. Shrinkability was measured at room temperature, 120 °C, 150 °C, and 180 °C. Shrinkability is found to be greater in high temperature stretched sample rather than that of room temperature stretched sample. It is observed that reactivity as well as heat shrinkability is more when 4,4′‐diamino diphenyl methane is used as a coupling agent. The mechanism of interchain crosslinking reaction has been confirmed by IR spectroscopy. Differential scanning calorimetry was performed to study the thermal stability of the sample. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
30.
Pradip K. Gadekar Maryann Hoermann Faith Corbo Rajiv Sharma S. Sarveswari Abhijit Roychowdhury 《Tetrahedron letters》2014
Herein, we have developed a mild and selective reductive deprotection method for the MAc protected alcohols using sodium borohydride. The new deprotection conditions provide a complete orthogonality between O-MAc and other protecting groups such as tert-butyl ester, N-Boc, Fmoc, Cbz, O-TBDMS, N-benzyl, O-benzyl, O-acetyl, N-acetyl, N-MAc, etc. In addition to O-MAc deprotection, this method is also applicable for S-MAc deprotection. 相似文献