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1.
Adriana Reyes‐Mayer Bonifacio Alvarado‐Tenorio Angel Romo‐Uribe Michael Jaffe 《先进技术聚合物》2013,24(12):1029-1039
The influence of heat treatment on the texture, microstructure and tensile mechanical properties of extruded thin films of a series of high‐performance thermotropic liquid crystal polymers (LCPs) was investigated. LCPs based on random units of hydroxybenzoic acid (B), hydroxynaphthoic acid (N), terephthalic acid (TA) and biphenol (BP) were kindly supplied by the former Hoechst Celanese Corp as 50 µm thick extruded tapes. The LCPs, denoted B‐N, COTBP and RD1000, have B and N as common comonomers and vary the other comonomers. Thus, this study also enables the investigation of the influence of monomer composition on microstructure and mechanical properties. Heat treatments were carried out at temperatures close to the solid‐to‐nematic transition (Ts→n) for periods up to 5 h, under dry air conditions. The thermal treatment produced either two endotherms or a small increase of Ts→n (B‐N and RD1000), or increased significantly Ts→n (COTBP). Moreover, when heat treatment was carried out approximately 40°C below the respective Ts→n, the mechanical Young's modulus, E, along the extrusion axis, increased for all LCPs. Strikingly, for COTBP, E increased over 100% relative to the as‐extruded film. The results also showed that the optimum treatment time for improving the Young modulus, under dry air atmosphere, was between 3 and 4 h. Wide‐angle X‐ray scattering showed a significant sharpening of crystalline reflections and concentration of the 002 meridional reflection as a result of thermal treatment, suggesting the elimination of defects and a better alignment of the molecular chains along the extrusion axis. This would explain the increase in tensile modulus. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
2.
S. De la Vega A. Castañeda-Gómez del Campo M. Jiménez-Reyes A. Tellez-Nieto D. Tenorio 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1835-1844
The results of a study about Majolica ceramics recovered from three sites located in Mexico City are here presented. The set of 83 samples includes several local ceramic-types dating from the Colonial Period, the nineteenth century and the present day, plus some foreign specimens and clay samples from the Puebla area. Fourteen chemical elements present in the samples were analyzed and measured by means of neutron activation, and statistically the following groups were established: two groups that were presumably manufactured in Mexico City, two from Puebla, one from outside the Mexican boundaries, most probably Sevilla-Triana pottery, plus three more groups from unidentified origins. It was also found out that botijas were both imported and produced domestically. These results are discussed against the relevant literature on known provenance, chronology and manufacture standards of this kind of pottery. 相似文献
3.
Calum Williams Yunuen Montelongo Jaime Oscar Tenorio‐Pearl Andrea Cabrero‐Vilatela Stephan Hofmann William I. Milne Timothy D. Wilkinson 《固体物理学:研究快报》2015,9(2):125-129
Digital holography requires arrays of small reconfigurable elements to achieve complex reconstruction of the hologram with common systems based on pixels utilizing liquid crystal on silicon (LCoS) technology. The backplane of a typical pixel element is potentially underutilized and thus relatively large physical areas exist in which information can be stored and exploited to give additional functionality to pixel elements. Polarisation and wavelength dependent optical properties can be achieved in small areas using the plasmonic effects of optical antennae. The integration of LCs with optical antennae‐based plasmonic holograms allows active modulation of the far field pattern. The work here demonstrates the concept that conventional LCoS pixel elements can be greatly enhanced with the integration of plasmonic holograms, composed of optical antennae patterned on the surface, giving rise to new levels of modulation capability for holographic pixel elements. Using LCs, polarisation dependent effects in plasmonic holograms can be switched. ‘Engineered pixels', with sub‐wavelength multiplexing over both polarisation and wavelength, can increase the channel capacity of a typical LC display device. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
4.
5.
Evolved Gas Analysis‐Mass Spectrometry to Identify the Earliest Organic Binder in Aegean Style Wall Paintings 下载免费PDF全文
Dr. Ravit Linn Dr. Ilaria Bonaduce Dr. Georgia Ntasi Prof. Leila Birolo Prof. Assaf Yasur‐Landau Prof. Eric H. Cline Dr. Austin Nevin Dr. Anna Lluveras‐Tenorio 《Angewandte Chemie (International ed. in English)》2018,57(40):13257-13260
An organic binder was identified in the painted fragments from the Canaanite palace of Tel Kabri, Israel. Recently dated to the late 18th century B.C.E. by 14C, Tel Kabri is the most ancient of the Eastern Mediterranean sites in which Aegean style paintings have been found. The application of pigments was suspected to be using an organic binding medium, particularly for the Egyptian Blue pigment. Samples of blue paint were examined using evolved gas analysis‐mass spectrometry (EGA‐MS) in order to overcome the analytical challenges imposed by highly degraded aged proteinaceous materials. Egg was identified as the binder based on the presence of hexadecanonitrile and octadecanonitrile, confirming the use of a secco painting technique. Lysozyme C from Gallus gallus was detected by proteomics analysis, confirming the presence of egg. To our knowledge, this is the earliest use of egg as a binder in Aegean style wall paintings. 相似文献
6.
We compute the largest dimension of the Abelian Lie subalgebras contained in the Lie algebra
of n×n strictly upper triangular matrices, where n ∈ ℕ \ {1}. We do this by proving a conjecture, which we previously advanced,
about this dimension. We introduce an algorithm and use it first to study the two simplest particular cases and then to study
the general case.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 3, pp. 419–429, September, 2007. 相似文献
7.
Vandenabeele P Ortega-Avilès M Castilleros DT Moens L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(4):1085-1088
This work represents the Raman spectra of 15 natural artists' materials that were obtained from local market in Mexico. Some of these products are not endemic to the region, but are often used in local conservation practice. Other materials are of local origin and have been used for centuries by local craftsmen. The Raman spectra that are reported here are: Chia oil, linseed oil, Campeche wax, beeswax, white copal, dammar, colophony, mastic, pixoy, chapopote, chucum, aje gum, gutta gum, peach gum and gum Arabic. The sample of pixoy was mixed with TiO(2), although it was not clear whether this was done intentionally or not. The Raman spectrum of chapopote, the local name for bitumen, contained features of carbonaceous and terpenoid matter. The Raman spectra of chapopote and chucum suffered severely from fluorescence, resulting in noisy Raman spectra. Aje gum and gutta gum are not gums, since they are resinous (terpenoid) in nature. Aje is a rare animal resin originating from Coccus axin. 相似文献
8.
José. A. Tenorio López Juan. J. Benvenuta Tapia María del Carmen Cuevas Díaz 《大分子反应工程》2009,3(8):473-485
The copolymerization reaction of butadiene and styrene copolymers prepared by anionic living polymerization using an initiator composed of alkyl aluminum, n‐butyl lithium, and barium alkoxide is studied using a kinetic model that considers the reactivity of active sites to be different; this assumption is justified by the varying geometric configurations. With the first‐order Markov model, the expressions for the fraction of active sites and dyad distribution are obtained. The rate constants are determined by fitting to the conversion and Bernoulli dyad data using the nonlinear least squares method. The conversion and dyad sequence distribution are correctly predicted, and the experimental results indicate that the microstructure and sequence distribution do not change with the conversion and temperature.
9.
T. Villa-Córdoba J. A. López-Palacios M. Jiménez-Reyes D. Tenorio 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1249-1258
Several ornaments named tezcacuitlapilli (coccyx-mirrors) are described and chemical analyses of raw materials (slate and
pigments) were carried out by neutron activation, X-ray diffraction, scanning electron microscopy and radiography. Elemental
and statistical analyses revealed that three different kinds of slate were used in their manufacture. The white pigment contains
gypsum while ochre, yellow and red pigments contain iron oxide. These ornaments were identified as coming from the Cave of
the Sun Pyramid of Teotihuacan. An attempt was undertaken to reconstruct the contexts of their manufacture and symbolic interpretation. 相似文献
10.
Emilio Bustelo Isaac de los Ríos Manuel J. Tenorio M. Carmen Puerta Pedro Valerga 《Monatshefte für Chemie / Chemical Monthly》2000,131(12):1311-1320
Summary. The solid-state tautomerization of the hydrido-alkynyl derivatives [Cp
*RuH(C&*CR)-(dippe)][BPh4] (Cp* = C5Me5; R = SiMe3, Ph, H; dippe = 1,2-bis-(diisopropylphosphino)-ethane) to their vinylidene isomers [Cp
*Ru*C*CHR(dippe)][BPh4] was studied by IR spectroscopy. Characteristic isothermic αvs. t curves for each individual rearrangement process were recorded. Their shape, and hence the isomerization mechanism, depends
strongly on the nature of the substituent R. The kinetic analysis of the above curves using the Avrami-Erofeev provided some mechanistic information about the isomerization process in the solid.
Received July 7, 2000. Accepted August 29, 2000 相似文献