全文获取类型
收费全文 | 142篇 |
免费 | 6篇 |
专业分类
化学 | 53篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 15篇 |
物理学 | 76篇 |
出版年
2024年 | 1篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 31 毫秒
41.
The strengthening of the hydrogen bonding (H-bond) network as well as transition from the tetrahedral-like water network to
the zigzag chain structure of alcohol upon increasing the alcohol concentration in ethanol-water and tertiary butanol (TBA)
— water mixtures have been studied by using both steady state and time resolved spectroscopy. Absorption and emission characteristics
of coumarin 153 (C153), a widely used non-reactive solvation probe, have been monitored to investigate the structural transition
in these binary mixtures. The effects of the hydrogen bond (H-bond) network with alcohol concentration are revealed by a minimum
in the peak frequency of the absorption spectrum of C153 which occur at alcohol mole fraction ∼0·10 for water-ethanol and
at ∼0·04 for water-TBA mixtures. These are the mole fractions around which several thermodynamic properties of these mixtures
show anomalous change due to the enhancement of H-bonding network. While the strengthening of H-bond network is revealed by
the absorption spectra, the emission characteristics show the typical non-ideal alcohol mole fraction dependence at all concentrations.
The time resolved anisotropy decay of C153 has been found to be bi-exponential at all alcohol mole fractions. The sharp change
in slopes of average rotational correlation time with alcohol mole fraction indicates the structural transition in the environment
around the rotating solute. The changes in slopes occur at mole fraction ∼0·10 for TBA-water and at ∼0·2 for ethanol-water
mixtures, which are believed to reflect alcohol mole fraction induced structural changes in these alcohol-water binary mixtures. 相似文献
42.
This paper presents a theoretical model for computing the velocity and sediment concentration profiles in a uniform sediment-laden flow carrying all fine, medium and coarse sediments. The proposed model essentially includes the effect of sediment concentration in total turbulent shear stress and eddy diffusivity in addition to the modified mixing length derived by Umeyama and Gerritsen [J. Hydr. Engng., ASCE, 118 (2) (1992) 229–245] applied to Hunt’s diffusion equation. Numerical solution of coupled differential equations for velocity and sediment concentration is carried out. The theoretical results show quite good agreement with the experimental data. 相似文献
43.
A. Ghoshal P. Mandal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):251-258
An exponential correlated basis set is tested within the framework
of multi-channel Schwinger variational principle in the momentum space.
It is found that inclusion of only the
positron-electron correlation in the basis set is
enough to obtain accurate results for all significant partial
waves for ground state positronium
formation in positron-hydrogen collisions at low and intermediate energies (6.856–75 eV).
Results are in conformity with other accurate
variational and non-variational calculations as well as observed data available in the
literature. 相似文献
44.
Cd(OH)2 and CdO nano/micro crystals were synthesized in ethanol-water medium using cadmium foil as a source under solvothermal condition. The experimental parameters such as ratio of ethanol to water, concentration of NaOH and synthesis temperature all play important role in determining the size, shape and crystalline phase of the products. The products were characterized by X-ray diffraction and scanning electron microscopy. Nano/micro crystals of CdO were also achieved by thermal treatment of Cd(OH)2 crystals in air at different temperatures. 相似文献
45.
B. Karrer G. Ghoshal 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):239-245
There has been a considerable amount of interest in recent years on the robustness of networks to failures. Many previous
studies have concentrated on the effects of node and edge removals on the connectivity structure of a static network; the networks are considered to be static in the sense that no compensatory measures are allowed for recovery of
the original structure. Real world networks such as the world wide web, however, are not static and experience a considerable
amount of turnover, where nodes and edges are both added and deleted. Considering degree-based node removals, we examine the
possibility of preserving networks from these types of disruptions. We recover the original degree distribution by allowing
the network to react to the attack by introducing new nodes and attaching their edges via specially tailored schemes. We focus
particularly on the case of non-uniform failures, a subject that has received little attention in the context of evolving
networks. Using a combination of analytical techniques and numerical simulations, we demonstrate how to preserve the exact degree distribution of the studied networks from various forms of attack. 相似文献
46.
47.
Summary An attempt is made to study effective electron mass in quantum well wires of ternary chalcopyrite semiconductors by formulating
a new 1D dispersion relation, within the framework of thek·p formalism considering the anisotropies in the band parameters. It is found, taking quantum well wires ofn-CdGeAs2 as an example, that the effective Fermi level mass depends on the subband index due to the combined influence of crystal-field
splitting parameter and the anisotropic spinorbit splitting parameters, respectively. The masses increase with increasing
carrier degeneracy and decreasing film thickness, respectively. In addition, the well-known results for the corresponding
parabolic energy bands have been derived as special cases of the generalized formulations. 相似文献
48.
Swadesh Kumar Ghoshal Sankar Sengupta 《Journal of Quantitative Spectroscopy & Radiative Transfer》1980,23(5):499-502
The modified Morse potential function known as the Hulburt-Hirschfelder function has been used for the Ar2 molecule using experimental values for the spectroscopic constants. The consistency of this potential is checked by recalculating the vibrational levels using Cashion's method. The results are satisfactory. The potential may be useful for calculating the anharmonic properties of crystalline argon. 相似文献
49.
The behaviour ofS-matrix for potentials generating bound states in continuum in the neighbourhood of the positive bound state energies is studied.
It is shown that unlike the case of usual negative energy bound states, theS-matrix does not have a pole at the positive bound state energy but becomes unity at the energy corresponding to bound states
in continuum. Calculations ofS-waveS-matrix for a local potential constructed by Stillinger and Herrick and a separable nonlocal potential constructed by the
present authors verify these results. Our results indicate that the bound states embedded in continuum constructedvia the von Neumann and Wigner procedure cannot be interpreted as resonances with zero width. 相似文献
50.