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1.
Summary Both preferential adsorption coefficient λ and intrinsic viscosity [η] for poly (di-o-alkylphenyl methacrylates) /Tetrahydrofuran
(THF)/water have been determined. The results are discussed in relation to the steric effect of the ortho-substituent groups
on the aromatic ring. 相似文献
2.
Jiang R. Saperstein R. Alic N. Nezhad M. McKinstrie C. Ford J. Fainman Y. Radic S. 《Photonics Technology Letters, IEEE》2006,18(23):2445-2447
The feasibility of distant wavelength conversion in photonic crystal fiber was explored. The one-pump parametric architecture was used to demonstrate translation from the conventional (1550 nm) to visible (500 nm) band. Experimental results are reported, which demonstrate the conventional-to-visible conversion of single- and multiple-channel signals encoded in the nonreturn-to-zero format 相似文献
3.
Witold Brostow Ligia Gargallo Andrea Hormazabal Magdalena Jaklewicz Kevin P Menard Alejandra Opazo Deodato Radic 《Polymer International》2004,53(4):460-464
We have studied blends of a polymer liquid crystal (PLC) with poly(cyclohexylethyl methacrylate) (PCHEMA) or poly(cyclohexylpropyl methacrylate) (PCHPMA). The PLC is PET/0.6PHB where PET = poly(ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of the latter in the copolymer. The microstructure was studied by scanning electron microscopy (SEM). PCHEMA + PLC (20 wt% of the latter, blend E) has a fine texture with LC islands evenly distributed in the matrix and good adhesion between the phases resulting from their partial miscibility. The PCHPMA + PLC (20 wt% of the latter, blend P) shows only limited compatibility. The SEM results are confirmed by values of the glass transition temperatures Tg determined via thermal mechanical analysis. The Tg value of the blend E is shifted towards the Tg of PLC; Tg of blend P is practically equal to that of PCHPMA. The linear isobaric expansivity αL values for both blends are lower than the respective values for pure PCHPMA and PCHEMA. Thermal stabilities of the blends determined by thermogravimetry are also better than those of pure polymethacrylates. The temperature of 50% weight degradation for blend E is higher than that for pure PCHEMA by more than 60 K Copyright © 2004 Society of Chemical Industry 相似文献
4.
5.
Summary
Copolymers containing vinyltrimethylsilane and vinyltrimethoxysilane with N-vinyl-2-pyrrolidone at different compositions
were synthesized and characterized. The reactivity ratios was estimated by using the classical Fineman-Ross and Kelen Tüdos
linear fitting procedures. These parameters were also estimated through a computer program based on nonlinear minimization
algorithm, starting from the r1 and r2 values obtained by the former procedures. The analysis of the results allow us to interpret the reactivity behaviour of these
polymers in terms of the relative reactivity of the substiuents. The effect of the chemical structure of the polymer side
group is discussed in terms of the different contributions to the stabilization of the radical intermediates.
Received: 18 February 1998/Revised version: 11 March 1998/Accepted: 16 March 1998 相似文献
6.
Boggio J. M. C. Moro S. Kuo B. P.-P. Alic N. Stossel B. Radic S. 《Lightwave Technology, Journal of》2010,28(4):443-447
7.
A study of the dielectric relaxation spectrum of poly(monocyclohexyl itaconate) (PMCHI) is performed by means of two experimental techniques: first, at variable frequency in the audio zone and, second, by thermally stimulated depolarization currents. Because of the high conductivity of the samples, there is a hidden dielectric relaxation that can be detected by using the macroscopic dynamic polarizability ε* defined in terms of the dielectric complex permittivity α* by means of the equation (ε* = 1)/(ε* + 2). The transformation performed through this equation is discussed in order to obtain the dielectric relaxations in the zone of high temperatures and low frequencies of the spectrum. 相似文献
8.
9.
Ricardo Díaz‐Calleja Abel García‐Bernab Enrique Snchez‐Martínez Andrea Hormazbal Ligia Gargallo Deodato Radi 《Polymer International》2002,51(12):1448-1458
Dielectric behaviour of two poly(methacrylate)s with cyclobutyl groups in the side‐chains has been studied. This investigation was performed by determining the dielectric permittivity and loss in terms of frequency and temperature for poly(cyclobutyl methacrylate) (PCBuM) and poly(cyclobutylmethyl methacrylate) (PCBuMM). Dynamic dielectric measurements show sub‐glass relaxations, probably due to motions in the lateral chain, including the cyclobutyl ring. The effect of the insertion of a flexible spacer group into the side‐chain is also analyzed. The α relaxations were analyzed in terms of the Havriliak–Negami equation and the free volume theory tested according to the Vogel–Fulcher–Tamman–Hesse equation. The conductive and interfacial phenomena were studied by hopping and MacDonald–Coelho models. © 2002 Society of Chemical Industry 相似文献
10.
Ricardo Díaz‐Calleja Abel García‐Bernab Enrique Snchez‐Martínez Andrea Hormazbal Ligia Gargallo Deodato Radi 《Polymer International》2002,51(9):808-814
Dynamic mechanical and dielectric behaviour of poly(cycloheptyl methacrylate), poly(cycloheptylmethyl methacrylate) and poly(cyclooctyl methacrylate) have been investigated. The study was performed by determining the components of the complex relaxation modulus E* and the complex dielectric permittivity ?*. Results are discussed in terms of the effect of the size and structure of the side ring. The saturated ring group shows mechanical and dielectric activity at low temperature that is analyzed in terms of the Fuoss–Kirkwood equation. The free volume for the three polymers was determined. The conductive and interfacial phenomena were studied by MacDonald and Coelho models, where the dipolar contribution was introduced. © 2002 Society of Chemical Industry 相似文献