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Lachezar Radev Vladimir Hristov Irena Michailova Bisserka Samuneva 《Central European Journal of Chemistry》2009,7(3):322-327
Ceramics, with basic composition based on the CaO-SiO2-P2O5-MgO system with different Ca+ Mg/P+Si molar ratio (R), were prepared via polystep sol-gel technique. The structure of the
obtained ceramic materials has been studied by XRD, FTIR spectroscopy, and SEM. X-ray diffraction showed the presence of akermanite
and HA for the sample with R = 1.68 and Mg substituted β-TCP and silicocarnotite for the sample with R = 2.16, after thermal
treatment at 1200°C/2 h. The obtained results are in good agreement with FTIR. In vitro test for bioactivity in static condition
proved that the carbonate containing hydroxyapatite (CO3HA) can be formed on the surface of the synthesized samples. CO3HA consisted of both A- and B-type CO32− ions. SEM micrographs depicted different forms of HA particles, precipitated on the surface after soaking in 1.5 simulated
body fluid (SBF).
相似文献
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J. Ma. Rincon J. Cáceres C. J. González-Oliver D. O. Russo A. Petkova H. Hristov 《Journal of Thermal Analysis and Calorimetry》1999,56(2):931-938
A study of three Spanish and one Bulgarian basaltic rock demonstrated that, after thermal treatment at temperatures higher
than 800°C, crystallization of pyroxenes, anorthite and magnetic occurred. Following sintering of the original basalts and
powdered original glasses, the same crystalline phases were nucleated and grown in the resulting glass-ceramics. Chemical
and DTA/TG analyses suggested similar behaviour for the synthesized Canarian basalt glasses, which are located in the tephrite-basanite
field, and different behaviour for the trachy-andesite Canarian and the basaltic-andesite Bulgarian basalt glass. In consequence
of the high sensitivity of the specific heat to phase transformations, Cp(T) and TMA experiments allowed a distinction between the tephrite-basanite and trachy-andesite Canarian glasses on the basis
of their different thermal behaviour.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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L. Xie D. W. Gidley H. A. Hristov A. F. Yee 《Journal of Polymer Science.Polymer Physics》1995,33(1):77-84
Positron Annihilation Lifetime Spectroscopy (PALS) measurements were conducted on polycarbonate subjected to either thermal expansion or to tensile and compressive strains. It was found that thermal expansion affected both the nanometer hole size and the hole number density, whereas mechanical stress affected mainly the size of existing holes, and did not generate or eliminate holes in the quasielastic deformation region. The effect of stress on yield and postyield behavior of this glassy material was also investigated. The deduced hole volume fraction of this polymer at 25°C was 6.8 ± 0.5% from the thermal expansion experiment and 7.2 ± 1.2% from the mechanical loading experiment. When the specimen was under compression, the hole volume fraction was found to continuously decrease. This can be considered as evidence of the inability of the free volume concept in explaining the yield behavior of glassy polymers. ©1995 John Wiley & Sons, Inc. 相似文献
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Hristov IH Dekock RL Anderson GD Göttker-Schnetmann I Mecking S Ziegler T 《Inorganic chemistry》2005,44(22):7806-7818
The transition metal catalyzed ethylene polymerization in aqueous emulsion has been increasingly successful in the last couple of years. Water however adversely affects the polymerization process by (a) competing with ethylene for the binding site at the metal and (b) hydrolyzing the growing chain. Neutral salicylaldiminato and cationic diimine complexes of Ni and Pd with different substituent patterns are studied here by density functional theory to determine their propensity toward water complexation and hydrolysis of the growing chain. Experimental NMR studies have also been carried out on the protonolysis of the Ni(II)-based Grubbs catalyst. It is found that in general that (a) ethylene coordination is preferred over water coordination for both Ni and Pd catalysts and (b) hydrolysis of the metal alkyl bond is competitive to ethylene insertion. 相似文献
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