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排序方式: 共有125条查询结果,搜索用时 203 毫秒
51.
Marco Zanetti Giovanni Camino Peter Reichert Rolf Mülhaupt 《Macromolecular rapid communications》2001,22(3):176-180
The thermal degradation behaviour of nanocomposites based upon poly(propylene)/organoclay, modified with protonated octadecyl amine (C18) in comparison to that of non‐exfoliated microcomposites based upon organoclay, modified with protonated butyl amine (C4), was studied by thermogravimetry. In the case of the nanocomposite, the temperature at which volatilisation occurs increases as compared of the microcomposite. Moreover, the thermal oxidation process of the polymer is strongly slowed down in the nanocomposite with high char yield both by a physical barrier effect, enhanced by ablative reassembling of the silicate, and by a chemical catalytic action due to the silicate and to the strongly acid sites created by thermal decomposition of the protonated amine silicate modifier. 相似文献
52.
A. Fina D. Tabuani F. Carniato A. Frache E. Boccaleri G. Camino 《Thermochimica Acta》2006,440(1):36-42
The mechanism of thermal degradation of several substituted polyhedral oligomeric silsesquioxanes (POSS) cages is studied in this work.Hydrogen POSS and methyl POSS shows incomplete sublimation on heating, both in inert atmosphere and in air. Isobutyl and octyl substituted POSS undergo an almost complete evaporation when heated in inert atmosphere. In air, oxidation competes with volatilization, producing a considerable amount of silica-like residue on heating up to 800 °C.Phenyl POSS shows a higher thermal stability than saturated aliphatic POSS and limited volatility, producing a ceramic residue at high yield on heating in nitrogen, composed of a silica containing a considerable amount of free-carbon. A lower amount of residue is shown after heating in air, corresponding to the POSS Si-O fraction.A vinyl POSS cage/network resin is also studied, in comparison to above materials, showing the highest ceramic yield. 相似文献
53.
C. Trobajo M. Suárez J. Rodriguez 《Journal of Radioanalytical and Nuclear Chemistry》1991,149(1):67-72
The intercalation compounds Ti(C3H7NH2)(HPO4)2·H2O (18.4 Å) (-TiP/n-Pr) and Ti(C4H9NH2)(HPO4)2·H2O (20.5 Å) (-TiP/n-Bu) have been prepared using -titanium phosphate, Ti(HPO4)2·2H2O (11.6 Å), as precursor. The retention of UO
2
2+
, in aqueous solutions by -TiP is very low being only a superficial adsorption phenomenon. When the intercalated materials are used, the retention is quantitative until 95% of the cation exchange capacity in the -TiP/n-Pr case (c.e.c.=6.30 mequiv./g), and over 80% for the -TiP/n-Bu compound (c.e.c.=6.04 mequiv./g). 相似文献
54.
When polypropylene is thermally degraded in mixtures with a highly chlorinated fire retardant chloroparaffin, a smaller amount of the lighter hydrocarbon fraction, which is also modified in composition, is evolved compared with that evolved from pure polypropylene. A corresponding increase in the amount of high boiling chain fragments is obtained from the mixtures. This effect can be explained in terms of the interactions which occur between degrading polymer and additive. 相似文献
55.
Metal functionalized POSS as fire retardants in polypropylene 总被引:1,自引:0,他引:1
Alberto Fina Hendrikus C.L. Abbenhuis Giovanni Camino 《Polymer Degradation and Stability》2006,91(10):2275-2281
This paper deals with the study of the combustion properties of dimeric and oligomeric Al-and Zn-isobutyl silsesquioxane (POSS)/polypropylene (PP) composites, in comparison with neat PP and PP/octaisobutyl POSS.The presence of Al-POSS leads to a decrease in combustion rate with respect to PP, resulting in a decrease of Heat Release Rate (−43% at 10 wt% POSS loading) as well as reduction in CO and CO2 production rates, whereas a negative effect on the above parameters is obtained with octaisobutyl POSS. Zn-POSS does not significantly affect the PP combustion behaviour.The effect of Al-POSS is most likely related to its chemical activity, which favours the formation of a moderate amount of char residue, by catalysing secondary reactions in the polymer during combustion. 相似文献
56.
The fundamental mechanisms by which fire retardant additives can interrupt the self-sustained combustion cycle of organic polymers are reviewed. Evaluation of fire retardant performance and methods used for mechanism assessment are discussed. Examples are given of recent mechanistic studies of halogen-based and intumescent systems indicating that some previous generalisations should be revised. It is shown that a deeper understanding of fire retardance mechanisms acquired through detailed thermal degradation studies is the only way to answer the ever increasing demand for polymeric materials characterised by minimised overall fire hazard. 相似文献
57.
On heating, ammonium polyphosphate eliminates ammonia and water in two successive steps. The first (T = 165–280°C) involves a limited weight loss (ca. 3%) and the formation of some branched structures. The transition from one crystalline form of ammonium polyphosphate to another, more stable, form, may prevent further elimination of NH3 and H2O which occurs in the second step (T > 280°C). The final product of degradation is characterised by a crosslinked POP structure formed by elimination of H2O between POH groups freed by the evolution of NH3. 相似文献
58.
The main characteristics of the evolution of HCl and SbCl3 during the thermal degradation of chloroparaffin-Sb2O3 mixtures, which are typical fire retardant additives for polymers, have been studied.Sb2O3 reacts with HCl evolved from the chloroparaffin without any apparent effect on the dehydrochlorination process itself. Evolution of SbCl3 occurs at a maximum rate between 300 and 350°C and is somewhat delayed in the earlier stage of reaction, depending on the composition of the mixture. 相似文献
59.
L. Costa G. Paganetto G. Bertelli G. Camino 《Journal of Thermal Analysis and Calorimetry》1990,36(3):1141-1153
The thermal decomposition of SbOCl, Sb4O5Cl2 and Sb8O11Cl2 has been studied by thermogravimetry with identification of the products resulting in the condensed phase by X-ray diffraction and infrared technique. It is shown that in nitrogen SbOCl undergoes progressive stepwise thermal disproportionation to Sb2O3 and SbCl3 with formation of Sb4O5Cl2 and Sb8O11Cl2 and as intermediates. It is thus confirmed that Sb3O4Cl, suggested to be formed instead of Sb8O11Cl2, is not an intermediate of this process. An identical mechanism is observed in air but with oxidation of Sb2O3 to Sb2O4.
This work was carried out with the financial support of the Progetto Finalizzato Chimica Fine II del Consiglio Nationale delle Ricerche. 相似文献
Zusammenfassung Mittels TG wurde die thermische Zersetzung von SbOCl, Sb4O5Cl2 und Sb8O11Cl2 untersucht und die entstehenden Produkte der kondensierten Phase mittels Röntgendiffraktionsuntersuchungen und IR-Spektroskopie identifiziert. Es wurde gezeigt, daß SbOCl in Stickstoff einer stufenweise thermische Disproportionierung unterliegt, bei der über die Zwischenprodukte Sb4O5Cl2 und Sb8O11Cl2 zuletzt Sb2O3 und SbCl3 entstehen. Es wurde weiterhin bewiesen, daß das anstelle von Sb8O11Cl2 vorgeschlagene Sb3O4Cl kein Zwischenprodukt dieses Zersetzungsvorganges ist. Ein ähnlicher Mechanismus gilt für die Zersetzung in Luft, jedoch mit der Oxidation von Sb2O3 zu Sb2O4.
This work was carried out with the financial support of the Progetto Finalizzato Chimica Fine II del Consiglio Nationale delle Ricerche. 相似文献
60.
Belén F. Alfonso Camino Trobajo Miguel A. Salvadó Pilar Pertierra Santiago García-Granda Jesús Rodríguez-Fernández Jesús A. Blanco José R. García 《无机化学与普通化学杂志》2005,631(11):2174-2180
Polycrystalline intercalated TiMxH2−nx(PO4)2· yC3H7NH2·wH2O compounds with transition metal (TM) ions (Mn+ = Co2+, Ni2+, Fe3+ or Cr3+) have been prepared by means of an indirect route and characterised using X-ray diffraction, scanning electron microscopy, chemical and thermal analysis, X-ray absorption and magnetic measurements. These novel pillared layered materials, which were obtained from the monoclinic (P21/c space group) α-Ti(HPO4)2·H2O phase, lose its crystallinity after intercalation. However all the TM ions are octahedrally surrounded by 6 oxygen atoms, although the X-ray absorption spectra evidence a clear dependence on the temperature. Surprisingly, all the materials behave as paramagnetic down to 1.5 K, but they exhibit different colours, what means that they are optically active (Co2+: violet; Ni2+: pale green; Fe3+: yellow; Cr3+: dark green). 相似文献