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1.
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
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Summary The preferential adsorption parameter of poly(phenyl methacrylate), poly[4-(1,1,3,3- tetramethylbutyl) phenyl methacrylate] and poly(4-tert-butyl styrene) in the mixture THF/water has been determined by exclusion chromatography (GPC) and differential refractometry and dialysis equilibrium (DR). The general behaviour of the polymers studied in this mixture is very similar, water is preferentially adsorbed by the polymer at low water content. The results are discussed in relation to the rigidity of the macromolecular chains and the hydrophobic degree of the substituent group in the aromatic ring. 相似文献
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Wiberg A.O.J. Bres C.-S. Kuo B.P.-P. Boggio J.M.C. Alic N. Radic S. 《Photonics Technology Letters, IEEE》2009,21(21):1612-1614
Technology for simultaneous demultiplexing of subrate tributaries is described and applied to 320-Gb/s return-to-zero input. The parametric architecture is scalable with respect to processed input rate and relies on cascaded all-optical multicasting and subrate sampling. Processing of 320-Gb/s input was achieved by creating eight channel copies, followed by a 20-THz-wide parametric gate. Multicasting was based on a self-seeded two-pump broadband fiber-optic parametric amplifier. The architecture was used to demonstrate error-free parallel demultiplexing of eight 320-Gb/s tributary channels at 40 Gb/s. 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.
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
8.
The viscometric behaviour of poly(4-tert-butylphenyl methacrylate) in the solvent mixture tetrahydrofuran/chloroform has been investigated. There is qualitative agreement between variations in [η] and predictions from the Dondos and Patterson theory. The role of the preferential adsorption of one of the solvents on the polymer was considered. The experimental adsorption coefficients λ1 are discussed in this particular mixture where GE < 0. In this binary solvent rthe kθ values of the polymer are similar in the three different mixed solvent compositions studied. 相似文献
9.
Ricardo Diaz Calleja Catherine Jaime's M. J. Sanchis-Sanchez Francisco Martinez-Pia Ligia Gargallo Deodato Radic 《Polymer Engineering and Science》1997,37(5):882-887
This paper composes the dynamic mechanical and dielectric relaxation properties for Poly (5-indanyl methacrylate) (P51M), a polymer with a bulky side chain. Measurements were carried out from about ?100°C to near 250°C. A secondary loss peak was observed in dielectric measurements at room temperature (20°C at 0.1 Hz.), whereas nothing was resolved in the mechanical spectrum. A prominent α relaxation associated with the glass transition was also observed near 107°C at 0.1 Hz. in the dielectric and the mechanical spectra. Dipolar dielectric loss overlapped with conductivity at high temperatures and low frequencies. A new method to split the conductive, interfacial, and dipolar contributions to the spectrum is proposed. 相似文献
10.
Inclusion complexes (ICs) between poly(?-caprolactone)diol (PEC) with α-cyclodextrin (α-CD) (α-CD-PEC) and γ-cyclodextrin (γ-CD) (γ-CD-PEC) were prepared and characterized by FT-IR, 1H NMR, thermogravimetry, surface activity and wettability measurements. The thermal stabilities of the inclusion complexes are very similar. The thermal stability of PEC is better than ICs and CDs. Stable monolayers of PEC and α-CD-PEC and γ-CD-PEC complexes have been obtained at the air-water interface using the Langmuir Technique. The surface pressure-area isotherms (π-A) were found to be of different types, depending on the CD utilized. From the surface free energy values of PEC and ICs it was possible to conclude that ICs are more hydrophobic than cyclodextrins. PEC is the most hydrophobic. The surface parameters the minimum area A0, the critical surface pressure πc, and static elasticity ?0 were also estimated for ICs and PEC. In order to describe the experimental results, molecular dynamic simulation (MDS) was performed. In addition, the physical properties that stabilize CD-CD, CD-polymer and CD-solvent interactions were elucidated by MDS. Theoretical results have demonstrated that complexes are stabilized by hydrophobic interactions between the cavity of CDs and the -(CH2)5-units of PEC, and also by hydrogen-bond formation between the hydroxyl groups situated along the rim of CD molecules threaded onto the PEC chain. CD-CD hydrogen-bond formation is maximized in 1:2 γ-CD-PEC complex and 1:1 α-CD-PEC complexes. 相似文献