全文获取类型
收费全文 | 319篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 197篇 |
力学 | 16篇 |
数学 | 24篇 |
物理学 | 92篇 |
出版年
2023年 | 5篇 |
2022年 | 32篇 |
2021年 | 39篇 |
2020年 | 16篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 17篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 9篇 |
2006年 | 11篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有329条查询结果,搜索用时 15 毫秒
1.
Faisal A.A. El-Orany 《Optics Communications》2006,263(2):235-238
We prove that the revival-collapse phenomenon occurring in the atomic inversion of the two-photon Jaynes-Cummings model, when the mode is initially prepared in the coherent state and the atom is in the excited state, can be obtained from the evolution of the quadrature squeezing of the four-photon Jaynes-Cummings model. 相似文献
2.
Laser gas-assisted material processing finds wide application in industry. The modelling of heating, elastic response of the substrate material, and the wave analysis gives insight into the laser workpiece interaction. In the present study, laser gas-assisted heating of steel is considered. The normal component of the thermal stress is taken as the source of load for the flexural wave generation in the material. The flexural wave generated is simulated and the wave characteristics are analyzed at four locations at the workpiece surface. The numerical scheme employing a control volume approach is introduced when solving the governing equations of flow and heat transfer while finite element and spectran element methods are used when solving the stress and wave equations. It is found that the normal component of the stress is tensile. The dispersion effect of the workpiece material, interference of the reflected beam, and partial overlapping of second mode of the travelling wave enable to identify a unique pattern in the travelling wave in the substrate. 相似文献
3.
Muhammad Faisal Nobuaki Sato Armando T. Quitain Hiroyuki Daimon Koichi Fujie 《国际化学动力学杂志》2007,39(3):175-180
The kinetics and pathway of hydrothermal decomposition of aspartic acid were studied using a continuous‐flow tubular reactor. The reaction was carried out in the temperature range of 200–260°C and at a pressure of 20 MPa. Deamination was the primary reaction, indicated by the presence of significant amount of ammonia, fumaric acid, or maleic acid in the products. Other reaction products were pyruvic acid, malic acid, and traces of succinic and lactic acid. Traces of alanine were also detected, showing the possibility of decomposing high‐molecular weight amino acids to obtain simple amino acids such as glycine or alanine. Results on the effect of reaction parameters demonstrated that decomposition of aspartic acid is highly temperature dependent under hydrothermal conditions. For a slight temperature difference of 60°C (from 200 to 260°C), the first‐order reaction rate constants of 0.003 significantly increased to 0.231 s?1. The activation energy was 144 kJ/mol, as calculated by the Arrhenius equation. No significant effect was exhibited by other reaction parameters such as pH and pressure. The results are useful in controlling the hydrolysis of proteinaceous materials toward high yield of aspartic acid under hydrothermal conditions. © 2007 Wiley Periodicals, Inc. 39: 175–180, 2007 相似文献
4.
A multigrid method is presented for the numerical solution of the linearized Poisson–Boltzmann equation arising in molecular biophysics. The equation is discretized with the finite volume method, and the numerical solution of the discrete equations is accomplished with multiple grid techniques originally developed for twodimensional interface problems occurring in reactor physics. A detailed analysis of the resulting method is presented for several computer architectures, including comparisons to diagonally scaled CG, ICCG, vectorized ICCG and MICCG, and to SOR provided with an optimal relaxation parameter. Our results indicate that the multigrid method is superior to the preconditioned CG methods and SOR and that the advantage of multigrid grows with the problem size. © 1993 John Wiley & Sons, Inc. 相似文献
5.
F. H. M. Faisal C. Göhner 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,25(4):309-314
We have developed and applied a model of energy transfer to noble gas atoms due to a resonance mechanism within a continuum of plasmon oscillation induced by intense laser pulses. The model is based on a generalization to 3D of the 1D many-body RPA method of Tomonaga. Total cross sections for laser energy absorption, the saturation intensities for ionization, mean energy transfer and degree of ionization of several noble gases, Xe, Kr, Ar, Ne are obtained for λ = 193 nm and λ = 1064 nm for a short Gaussian laser pulse. Probability distribution of absorption of a given number of photons in Xe is also obtained for λ = 193 nm andI 0 = 1014 W/cm2. The results are consistent with the rapid energy transfer necessary for multiple ionization at these frequencies. 相似文献
6.
Nanocrystalline TiO2-HClO4,as newly reported catalyst,has been used as an efficient and reusable catalyst for the chemoselective N-Boc protection of amines.The clean,mild acidity condition, quantitative yields of products,short reaction time and low reaction temperature are attractive features of this reaction.In practice,this method is a combination of a satisfactory synthesis and more significantly easy product isolation and purification. 相似文献
7.
8.
Md Sabir Alam Md Noushad Javed Faheem Hyder Pottoo Aafrin Waziri Faisal A. Almalki Md Saquib Hasnain Arun Garg Md Khalid Saifullah 《应用有机金属化学》2019,33(9)
Microwave irradiation (MI) process characteristically enables extremely rapid “in‐core” heating of dipoles and ions, in comparison to conventional thermal (conductance) process of heat transfer. During the process of nanoparticles synthesis, MI both modulates functionality behaviors as well as dynamic of reaction in favorable direction. So, MI providing a facile, favorable and alternative approach during nanoparticles synthesis nanoparticles with enhanced catalytic performances. Although, conventionally used reducing and capping reagents of synthetic origin, are usually environmentally hazardous and toxic for living organism. But, in absence of suitable capping agent; stability, shelf life and catalytic activity of metallic nanoparticles adversely affected. However, polymeric templates which emerged as suitable choice of agent for both reducing and capping purposes; bearing additional advantages in terms of catalyst free one step green synthesis process with high degree of biosafety and efficiency. Another aspect of current works was to understand role of process variables in growth mechanism and catalytic performances of microwave processed metallic nanoparticles, as well as comparison of these parameters with conventional heating method. However, due to poor prediction ability with previously published architect OFAT (One factor at a time) design with these nanoparticles as well as random selection of process variables with their different levels, such comparison couldn't be possible. Hence, using gum Ghatti (Anogeissus latifolia) as a model bio‐template and under simulated reaction conditions; architect of QbD design systems were integrated in microwave processed nanoparticles to establish mechanistic role these variables. Furthermore, in comparison to conventional heating; we reported well validated mathematical modeling of process variables on characteristic of nanoparticles as well as synthesized gold nanoparticles of desired and identical dimensions, in both thermal and microwave‐based processes. Interestingly, despite of identical dimension, MI processed gold nanoparticles bearing higher efficiency (kinetic rate) against remediation of hazardous nitro dye (4‐nitrophenol), into safer amino (4‐aminophenol) analogues. 相似文献
9.
10.
Journal of Solid State Electrochemistry - Graphene nanosheets (G) and pure, as well as doped Mg-, Mn-, V-Li4Ti5O12, spinel structure have been synthesized. As-prepared materials were characterized... 相似文献