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排序方式: 共有48条查询结果,搜索用时 234 毫秒
1.
Stephane Salmieri Farhana Islam Ruhul A. Khan Farah M. Hossain Haytham M. M. Ibrahim Chuanwei Miao Wadood Y. Hamad Monique Lacroix 《Cellulose (London, England)》2014,21(3):1837-1850
New bioactive nanocomposite films were prepared by compression molding method for food applications. Film matrix was composed of poly(lactic acid) containing cellulose nanocrystals (PLA-CNC). Nanocomposite films were converted to bioactive films using nisin as an antimicrobial agent by an adsorption coating method. Resulting antimicrobial films were then introduced in packages containing sliced cooked ham as a food model and stored for 14 days at 4 °C to determine their inhibiting capacity against Listeria monocytogenes and their physicochemical and structural properties. The study also focused on the nisin release from the films by using an agar diffusion bioassay. It was observed that mechanical properties such as tensile strength, tensile modulus, elongation at break and water vapor permeability values of the bioactive films were stable after 14 days of storage. Fourier transform infrared spectroscopy analysis allowed characterizing the adsorption of nisin onto PLA-CNC surface. Microbiological analysis of sliced cooked ham inoculated with L. monocytogenes (3 log CFU/g) allowed determining the potentiality of nisin as a strong antimicrobial agent in PLA-CNC-based films. Bioactive PLA-CNC-nisin films showed a significant reduction of L. monocytogenes in ham from day 1 and a total inhibition from day 3. The percentage of nisin release increased continuously from day 0 to day 14, up to 21 % at day 14. These results demonstrated the potential application of PLA-CNC-nisin films on controlling the growth of food pathogens in meat products. 相似文献
2.
MacFarlane WA Bobroff J Alloul H Mendels P Blanchard N Collin G Marucco J 《Physical review letters》2000,85(5):1108-1111
We present a study of the spin dynamics of magnetic defects induced by Li substitution of the plane Cu in the normal state of YBa2Cu3O6+x. The fluctuations of the coupled Cu magnetic moments in the vicinity of Li are probed by near-neighbor 89Y and 7Li NMR spin lattice relaxation. The data indicate that the magnetic perturbation fluctuates as a single entity with a correlation time tau which scales with the local static susceptibility. This behavior is reminiscent of the low T Kondo state of magnetic impurities in conventional metals. Surprisingly it extends well above the "Kondo" temperature for the underdoped pseudogapped case. 相似文献
3.
Full reports concerning the nuclear relaxation of 11B, 23Na, 29Si and 77Se in the following glasses: B2O3, Na2B4O7, (Na2O)0.3(SiO2)0.7, Se are presented. Extended measurements confirm the existence of an efficient quadrupolar mechanism typical of glasses and show that the two-phonon process, responsible for the quadropolar relaxation in insulating crystals, is always negligible in our whole range of investigation. The relaxation rate T1?1, field independent in almost all cases, varies like T(1+γ) with 0 < γ < 1 between 1.2 K and 100 K but exhibits different behaviour at higher T depending upon the analysed material. Whereas T1 goes through a minimum at 300 K in B2O3, its T-dependence for 23Na in Na2B4O7 and (Na2O)0.3(SiO2)0.7 becomes faster than in the low-T regime. Several attempts made to interpret the data within the framework of the tunneling model, commonly invoked to explain the anomalous thermal properties of glasses, are reviewed in detail. It is concluded that the T1 results are best accounted for by a process consisting of the modulation of the electric field gradient (EFG) at the nuclear site by its nearest neighbour tunneling defect. This EFG fluctuation is shown to be dominated by interactions between defects and an average correlation time of about 10?9 sec is assigned to it. A complete T1 calculation requires the previous knowledge of the physical nature of the defects, so far not available. Each defect is then tentatively identified with a bridging oxygen atom tunneling between two potential wells, which gives the correct energy dependence for the EEG matrix element. A defect number of 1027 m?3 is shown to be consistent with the results. 相似文献
4.
V. Brouet H. Alloul E. Lafontaine L. Malier L. Forro 《Applied Physics A: Materials Science & Processing》1997,64(3):289-293
\chem{Cs_{1}C_{60}} . The NMR spectrum allows, when the Magic Angle Spinning (MAS) technique is used, to get information about the electronic structure
of this phase, which points out that the spin density is not uniformly distributed on the ball. An estimation of the strength of the quadrupolar effects on is then given, which shows that it is possible to analyse the spin-lattice relaxation time in terms of magnetic effects. A comparison with the of is then justified and allows us to point out the importance of low dimensional antiferromagnetic fluctuations in this compound.
We also investigate the nature of the magnetic ground state in : the broadening of the spectra states unambiguously its magnetic nature and a detailed analysis of their shape gives further
indications on the antiferromagnetic nature of the magnetic order, which seems characterized by a large amount of disorder.
Received: 19 November 1996/Accepted: 19 December 1996 相似文献
5.
P. Matus H. Alloul P. M. Singer V. Brouet G. Kriza S. Garaj L. Forró 《Applied magnetic resonance》2004,27(1-2):133-138
We have investigated the alkali metal fulleride Na2CsC60 by23Na nuclear magnetic resonance (NMR), The NMR line of the tetrahedral site is split below 170 K (T and T′ lines) similarly to the A3C60 compounds with A=Rb or K. The intensity fraction of the T′ line follows the same temperature dependence as the13C NMR line width. We have also found that the spectrum is independent of the cooling rate. Spin-echo double resonance measurements show that T and T′ sites are mingled on a microscopic scale. We propose that the different23Na NMR lines correspond to different fullerene orientational environments of the tetrahedral alkaline site. 相似文献
6.
Co and Na NMR are used to probe the local susceptibility and charge state of the two Co sites of the Na-ordered orthorhombic Na(0.5)CoO(2). Above T(N) = 86 K, both sites display a similar T dependence of the spin shift, suggesting that there is no charge segregation into Co(3+) and Co(4+) sites. Below T(N), the magnetic long range commensurate order found is only slightly affected by the metal-insulator transition at T(MIT) = 51 K. Furthermore, the electric field gradient at the Co site does not change at these transitions, indicating the absence of charge ordering. All these observations can be explained by successive spin-density wave induced by two nestings of the Fermi surface specific to the x = 0.5 Na ordering. 相似文献
7.
We have investigated a set of sodium cobaltates (Na
x
CoO2) samples with various sodium content (0.67 ≤ x ≤ 0.75) using Nuclear Quadrupole Resonance (NQR). The four different stable phases and an intermediate one have been recognized.
The NQR spectra of 59Co allowed us to clearly differentiate the pure phase samples which could be easily distinguished from multi-phase samples.
Moreover, we have found that keeping samples at room temperature in contact with humid air leads to destruction of the phase
purity and loss of sodium content. The high sodium content sample evolves progressively into a mixture of the detected stable
phases until it reaches the x = 2/3 composition which appears to be the most stable phase in this part of phase diagram. 相似文献
8.
9.
Mousa Al-Noaimi Mohammad El-khateeb Salim F. Haddad Haytham Saadeh 《Transition Metal Chemistry》2010,35(7):877-883
Abstract
Five ruthenium complexes bearing phenylazo-(2-(phenylthio))phenylmethine ligands of the general type trans-[RuII(bpy)(L)(Cl)2] (C1–C5) {L = YC6H4N=NC(COCH3)=NC6H4(2-SC6H5), H (L1), Cl (L2), OCH3 (L3), Br (L4), or NO2 (L5)} have been synthesized. The crystal structure of trans-[Ru(bpy)(L1)(Cl)2] (C1) is reported and shows no direct metal–S interaction. The complexes have been characterized through spectroscopic (IR, UV/vis and NMR) and electrochemical (CV) techniques. The electrochemical parameters (E L(L)) of the azoimine ligands are reported. 相似文献10.
Rullier-Albenque F Tourbot R Alloul H Lejay P Colson D Forget A 《Physical review letters》2006,96(6):067002
We have studied the influence of disorder induced by electron irradiation on the Nernst effect in optimally and underdoped YBa2Cu3O(7-delta) single crystals. The fluctuation regime above T(c) expands significantly with disorder, indicating that the T(c) decrease is partly due to the induced loss of phase coherence. In pure crystals the temperature extension of the Nernst signal is found to be narrow whatever the hole doping, contrary to data reported in the low-T(c) cuprate families. Our results show that the presence of intrinsic disorder can explain the enhanced range of the Nernst signal found in the pseudogap phase of the latter compounds. 相似文献