全文获取类型
收费全文 | 155篇 |
免费 | 14篇 |
国内免费 | 3篇 |
专业分类
化学 | 41篇 |
晶体学 | 2篇 |
力学 | 2篇 |
物理学 | 127篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 7篇 |
2013年 | 25篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 9篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 359 毫秒
41.
The correlation effect in two-component systems of different viscosities was analyzed based on a concentration depolarization experiment. The inclusion of a correlation effect was found to be fully justified only in systems for which the localization time, l, is considerably shorter than that of the rotational relaxation, rot. On the grounds of an approximate analysis, taking into account the competition between the concentration and the rotational depolarization, it was possible to explain the concentration changes in the emission anisotropy in the systems investigated.Dedicated to Professor Czestaw Bojarski on the occasion of his 70th birthday. 相似文献
42.
K. Ohara 《Colloid and polymer science》1981,259(10):981-983
Summary Thermally stimulated depolarization currents were investigated for films obtained from supernatant layer of mixed solutions ofi- ands-PMMA ini/s weight ratio of 1/1 and 1/2. The results showed that the degree of stereocomplex formation is not uniform: the mixed solutions contain the insoluble and the soluble stereocomplex aggregates and in some case the residual (free)i-PMMA. The stereocomplex is formed ini/s weight ratio of 1/2. 相似文献
43.
In the present paper, we discuss the molecular information that can be derived from surface‐enhanced resonance Raman Scattering (SERRS) experiments performed with different excitation wavenumbers, which are close to resonance with an excited electronic state of the molecule [surface‐enhanced Raman dispersion spectroscopy (SERADIS)]. We specifically consider the situation, where a molecule is physisorbed to a site characterized by a local electric field with a direction independent of the direction of the external, exciting field. The molecular information available in this experimental situation is compared with the information available in a corresponding Raman dispersion spectroscopy (RADIS) experiment performed on a free molecule or a molecule physisorbed to a site, where the local field is isotropic. The consequences for resonance Raman scattering (RRS) and RADIS, when the molecule is adsorbed in the highly anisotropic hot spot (HS), are discussed; here it is shown that only the molecular information originating from the symmetric part of the scattering tensor can survive in SERRS and in SERADIS. Besides, it is shown that the depolarization ratio can no longer be used to discriminate between totally and non‐totally symmetric modes in the polarized surface‐enhanced Raman scattering (SERS) spectra. These results have implications for the resonance Raman spectra, but even more important for the application of the resonance Raman effect in the investigation of excited vibronic molecular states, in general, and in the investigation of electronic states in larger bio‐molecules, such as the various metallo‐porphyrins. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
44.
Sheng Yinghong Venkatraman Ramaiyer Kwiatkowski Józef S. Majewska Joanna Leszczynski Jerzy 《Structural chemistry》2003,14(5):511-525
The molecular geometrical parameters, rotational constants, dipole moments and vibrational infrared properties of a series of phosphoryl compounds (OPX
i
Y
j
Z
k
, X, Y, Z = F, Cl, Br; i+ j + k = 3) and their thio analogs are predicted by density functional and MP2 calculations using the 6-311G(2d,2p) basis set. Both methods yielded similar results. The predicted molecular parameters and the vibrational Raman and infrared spectra agree well with the available experimental data. The Raman Scattering Activities (RSA) and depolarization ratios (Dep) of the molecules are obtained by DFT calculations. Considering the different substitution modes of various halogen atoms, the resultant changes in the geometrical and vibrational properties are discussed. Such studies permit detailed information to be obtained concerning unknown molecules and can define the guidelines for synthesizing molecules of particular characteristics. 相似文献
45.
A polymer chain conformation change near the critical point of liquid-liquid phase separation was investigated. Poly(N-isopropylacrylamide) labeled with a small amount of carbazolyl group for a fluorophore (P(NIPA-Cz)) was prepared. A ternary system of P(NIPA-Cz)+cyclohexane+methanol was investigated by the fluorescence spectroscopic technique. A mixed solvent of cyclohexane+methanol (CH/MeOH) shows phase separation at the upper critical solution temperature. Light scattering intensity, fluorescence emission intensity and fluorescence anisotropy ratio, as a function of temperature, were measured with quasi statically approaching to the critical demixing point. The fluorescence intensity of the carbazolyl groups attached to the polymer chain decreases with approaching to the critical temperature. This result suggests that the radius of gyration of the polymer decreases upon approaching to the critical demixing point of the solvent. We discuss the collapse and aggregation processes of the polymer based on the fluorescence quenching method. The rotational diffusion coefficient of carbazolyl groups attached to the polymer chain was estimated by the fluorescence depolarization technique. The rotational motion of carbazolyl groups is slowed down upon approaching the critical point. 相似文献
46.
Transient currents, measured with pure and iodine doped polyvinyl formal (PVF) films as a function of poling field (15–100
kV/cm) and temperature (30–95°C), have been found to follow Curie-von Schweidler law characterized with two slopes in short
and long time regions. The isochronals (i.e. current/temperature plots at constant times) have been found to give rise to
a peak located at 75°C. The order of current has been found to increase with increase in poling field, temperature and iodine
mixing. The comparative studies of the isochronals with the thermally stimulated discharge current (TSDC) indicated the strong
resemblance between the two studies. It is suggested that both the dipolar orientation due to molecular mechanism of motions
with the side chains and space charge due to trapping of injected charge carriers in energetically distributed traps may be
responsible for the observed currents. The dependence of current and activation energy on iodine mixing is explained on the
basis of a charge transfer type of interaction. 相似文献
47.
48.
Andrzej W. Domanski Rafal Cieslak Miroslaw A. Karpierz Daniel Budaszewski Tomasz R. Wolinski 《Central European Journal of Physics》2008,6(3):628-633
This paper analyzes the second harmonic generation (SHG) efficiency of light with partial temporal coherence due to depolarization
effects in birefringent media. It discusses relations between SHG efficiency fading, light source spectrum, crystal birefringence,
and phase matching conditions. The efficiency of SHG pumped by the partially coherent light beam that may depolarize light
in nonlinear birefringent crystal is also analyzed. The basic theory of SHG with its modification for partially coherent light
with depolarization and some numerical calculations of the SHG process are described.
Presented at 9-th International Workshop on Nonlinear Optics Applications, NOA 207, May 17–20, 2007, Świnoujście, Poland 相似文献
49.
The defocussing and the depolarization of a high energy muon beam in a beryllium filter, often used to eliminate accompanying
pions, have been studied. The quantum mechanical transport equation of Waldmann, which can also be used to describe the multiple
scattering of Dirac particles, is solved with a distorted wave Born approximation. Calculations are done for both the Thomas-Fermi
and the Hartree-Fock potential of the beryllium atom. It is shown that the Hartree-Fock potential leads to a less divergent
beam. The depolarization of a longitudinally polarized muon beam in passage through a thin beryllium foil is also studied. 相似文献
50.
Roger C Walker II Hossein Hamedi William Hunter Woodward Michael Lanagan 《Journal of polymer science. Part A, Polymer chemistry》2020,58(22):3142-3152
Cross-linked polyethylene (XLPE) is notable for its use as power cable insulation. Its longevity is limited by space charge buildup linked to impurities such as the byproducts left behind by the cross-linking agent dicumyl peroxide (DCP). The goal of this work is to determine the impacts of these byproducts on charge trapping and detrapping in XLPE using the thermally stimulated depolarization current technique. XLPE with byproducts has one source of trapped charge, which originates from the byproducts. XLPE that was thermally treated via degassing exhibits two other sources of trapped charge, which are charge injection and dipolar relaxations. Oxidation from degassing was shown to control the trapping from these sources, which is useful knowledge for processing this material prior to its use. Reintroducing acetophenone, one of the major byproducts of DCP, suppresses those two peaks once more, showing that it controls the overall space charge buildup characteristics in XLPE. 相似文献