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91.
G. Camino L. Costa L. Trossarelli F. Costanzi A. Pagliari 《Polymer Degradation and Stability》1985,12(3):213-228
It is shown that, on heating ammonium polyphosphate-pentaerythritol mixtures, phosphoric ester bonds are formed first by alcoholysis of the polyphosphate chain. Further intramolecular alcoholysis and/or esterification leads to cyclic pentaerythritol phosphate structures inserted in the polyphosphate chains. Evidence is also given of intermolecular dehydration of pentaerythritol in mixtures with a large excess of alcoholic hydroxy groups over phosphorus atoms. The intumescent behaviour of the mixtures is discussed in relation to the final structure of the product of reaction which depends on the composition of the original mixture. 相似文献
92.
Fabienne Samyn Charafeddine Jama Shonali Nazare Alberto Fina Giovanni Camino 《European Polymer Journal》2008,44(6):1631-1641
Flame retardant nanocomposites have attracted many research efforts because they combine the advantages of a conventional flame retardant polymer with that of polymer nanocomposite. However the properties obtained depend on the dispersion of the nanoparticles. In this study, three types of polymer flame retarded nanocomposites based on different matrices (polypropylene (PP), polybutadiene terephtalate (PBT) and polyamide 6 (PA6)) have been prepared by extrusion. In order to investigate the dispersion of nanoparticles in the polymer containing flame retardant, conventional methods used to characterise the morphology of composites have been applied to FR composites containing nanoclays. XRD, TEM and melt rheology give useful information to describe the dispersion of the nanofiller in the flame retarded nanocomposite. In the PA6-OP1311 (phosphorus based flame retardant) materials, the clay is well dispersed unlike in PBT and PP materials where microcomposites are obtained with some intercalation. The poor dispersion is also highlighted by NMR measurements but the presence of flame retardant particles interferes in the quantitative evaluation of nanoclay dispersion and underestimations are made. 相似文献
93.
Microcrystals of Th(HPO 4) 2.H 2O were hydrothermally obtained from a Th(NO 3) 4-CO(NH 2) 2-H 3PO 3-H 2O system ( T = 180 masculineC). The structure [orthorhombic, Pbca, a = 9.1968(2) A, b = 18.6382(2) A, c = 8.7871(2) A], unlike alpha-Zr(HPO 4) 2.H 2O-type layered compounds, consists of a three-dimensional framework with PO 4 tetrahedra coordinated to Th atoms. The water molecule is also coordinated to the Th atom and projected toward small channels running along the directions of the a and c axes. The ThO 6O(w) environment could be described as a highly distorted pentagonal bipyramid. 相似文献
94.
Microcrystals of the first ammonium-thorium phosphates, (NH 4) 2Th(PO 4) 2.H 2O (tetragonal, I4 1/ amd, a = 7.0192(4) A, c = 17.9403(8) A) and NH 4Th 2(PO 4) 3 (monoclinic, C2/ c, a = 17.880(6) A, b = 6.906(1) A, c = 8.152(2) A, beta = 104.39(2) degrees ) were hydrothermally obtained from a Th(NO 3) 4-CO(NH 2) 2-H 3PO 3-H 2O system ( T = 180 degrees C). In both cases, the structure consists of a three-dimensional framework with PO 4 tetrahedra coordinated to Th atoms (ThO n polyhedra, where n = 8 or 9, for the tetragonal or monoclinic phase, respectively). The ammonium ions (and water molecules) are located in the tunnels. 相似文献
95.
Th(2)(PO(4))(2)(HPO(4)).H(2)O was synthesized under wet hydrothermal conditions starting from a mixture of H(3)PO(3) and Th(NO(3))(4).5H(2)O. The crystal structure was solved by powder X-ray diffraction data. The unit cell parameters are a = 6.7023(8) Angstroms, b = 7.0150(8) Angstroms, c = 11.184(1) Angstroms, beta = 107.242(4) degrees, space group P2(1), and Z = 2. The structure consists of layers of both thorium atoms and PO(4) groups, alternating with a layer formed by HPO(4) entities and water molecules. By thermal treatment, this compound turns into Th(4)(PO(4))(4)P(2)O(7), a ceramic already described in the field of the immobilization of tetravalent actinides. 相似文献
96.
97.
N. Tzankova Dintcheva F.P. La Mantia F. Trotta M. P. Luda G. Camino M. Paci L. Di Maio D. Acierno 《先进技术聚合物》2001,12(9):552-560
Plastic waste or scraps are generated from two main sources: industrial wastes and post‐consumer wastes. By using the flotation method, generally two fractions are obtained from municipal post‐consumer wastes: a light fraction, floating on water, and a heavy fraction. The former is essentially made of low and high density polyethylene—LDPE, HDPE—and polypropylene—PP; the heavy fraction is formed by poly(vinyl chloride)—PVC—and poly(ethylene terephthalate)—PET. In this work, the recycling of a light fraction from municipal post‐consumer plastics has been studied, considering also the effect of filler type—glass fibres, calcium carbonate and wood fibres—and processing apparatus—discountinous mixer, single and twin screw extruder—on the properties. Although the similar chemical nature of the two main components, polyethylene and polypropylene of the light fraction, the mechanical properties of the recycled mixture are quite scarce, mainly because of the incompatibility and the possible presence of some heterogeneous particles. The recycling of the light fraction can significantly change the properties of the polymer system because of the thermomechanical stress and of the residence time during processing. The adding of the three fillers type leads to an increase of the thermomechanical and of some of the mechanical properties. The elastic modulus increases with the three fillers; in particular, glass fibres show the best results. The effect of the three fillers is quite similar for tensile strength, elongation at break and impact strength. The adding of inert filler strongly improves the rigidity of light fraction from municipal post‐consumer plastics. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
98.
Y Wang S Nakamura M Ue P B Balbuena 《Journal of the American Chemical Society》2001,123(47):11708-11718
Reductive decomposition mechanisms for ethylene carbonate (EC) molecule in electrolyte solutions for lithium-ion batteries are comprehensively investigated using density functional theory. In gas phase the reduction of EC is thermodynamically forbidden, whereas in bulk solvent it is likely to undergo one- as well as two-electron reduction processes. The presence of Li cation considerably stabilizes the EC reduction intermediates. The adiabatic electron affinities of the supermolecule Li(+)(EC)n (n = 1-4) successively decrease with the number of EC molecules, independently of EC or Li(+) being reduced. Regarding the reductive decomposition mechanism, Li(+)(EC)n is initially reduced to an ion-pair intermediate that will undergo homolytic C-O bond cleavage via an approximately 11.0 kcal/mol barrier, bringing up a radical anion coordinated with Li(+). Among the possible termination pathways of the radical anion, thermodynamically the most favorable is the formation of lithium butylene dicarbonate, (CH2CH2OCO2Li)2, followed by the formation of one O-Li bond compound containing an ester group, LiO(CH2)2CO2(CH2)2OCO2Li, then two very competitive reactions of the further reduction of the radical anion and the formation of lithium ethylene dicarbonate, (CH2OCO2Li)2, and the least favorable is the formation of a C-Li bond compound (Li carbides), Li(CH2)2OCO2Li. The products show a weak EC concentration dependence as has also been revealed for the reactions of LiCO3(-) with Li(+)(EC)n; that is, the formation of Li2CO3 is slightly more favorable at low EC concentrations, whereas (CH2OCO2Li)2 is favored at high EC concentrations. On the basis of the results presented here, in line with some experimental findings, we find that a two-electron reduction process indeed takes place by a stepwise path. Regarding the composition of the surface films resulting from solvent reduction, for which experiments usually indicate that (CH2OCO2Li)2 is a dominant component, we conclude that they comprise two leading lithium alkyl bicarbonates, (CH2CH2OCO2Li)2 and (CH2OCO2Li)2, together with LiO(CH2)2CO2(CH2)2OCO2Li, Li(CH2)2OCO2Li and Li2CO3. 相似文献
99.
Mariano Pracella Donatella Chionna Alberto Fina Daniela Tabuani Alberto Frache Giovanni Camino 《Macromolecular Symposia》2006,234(1):59-67
Nanocomposites of isotactic polypropylene (PP) with polyhedral oligomeric silsesquioxanes (POSS) [RSiO1,5]8 having different alkyl substituents (R = methyl, isobutyl, isooctyl) were obtained by melt blending and analysed with electron microscopy, optical microscopy and DSC calorimetry. The influence of POSS structure on the morphological characteristics, the crystallization and melting behaviour of PP/POSS composites was investigated with varying the filler amount. The crystallization kinetics of the composites from the melt, examined both in isothermal and non-isothermal conditions, demonstrated that the nucleation activity of the examined POSS can be related to the length of alkyl substituents which, depending on the loading amount, affect the filler dispersion in the PP matrix and the growth of polymer crystals. 相似文献
100.