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排序方式: 共有113条查询结果,搜索用时 15 毫秒
61.
62.
Christine Lausser Michael U. Kumke Markus Antonietti Prof Dr. Helmut Cölfen 《无机化学与普通化学杂志》2010,636(11):1925-1930
Europium(III) fluoride mesocrystals were synthesised in an organic matrix. This matrix is a gel formed by Eu3+ ions and a polycarboxylate/sulfonate copolymer, ACUSOL 588G. In the gel phase, the local amount of europium ions is very high since Eu3+ acts as a crosslinker, and crystallisation occurs upon addition of F–. Nucleated seed crystals in the gel phase grow by further ion attachment and form mesocrystals by mutual orientation of the EuF3 particles in the gel. We propose a dipole field as reason for this alignment and that the dipolar character of the particles originates from adsorption of the polyelectrolyte on charged crystal faces. 相似文献
63.
The iodine-doped GeTe4 infrared chalcogenide glass was studied by means of differential scanning calorimetry DSC, X-ray diffraction XRD, Raman spectroscopy and infrared microscopy. Extensive non-isothermal thermo-kinetic characterisation of the glass transition, crystallisation and melting phenomena was performed in dependence on the particle size. The Tool–Narayanaswamy–Moynihan model was applied to describe the enthalpy relaxation processes: the compositional evolution of the relaxation parameters was then explained in terms of the structural changes and movements of the characteristic structural units. Mathematic deconvolution was applied to treat the complex crystallization kinetics – two crystal growth sub-processes were identified and described in terms of the autocatalytic ?esták-Berggren model. Based on the XRD and microscopic analyses the following crystallization mechanisms were revealed: initial precipitation of tellurium (surface-located) followed by a combined surface- and bulk-located formation of GeTe and GeI4 phases. Based on the DSC results obtained for fine powders, the presence of mechanically induced defects was found to accelerate the Te precipitation, the consequences of which are discussed with regard to the performance of nowadays glass stability criteria. 相似文献
64.
Supatra Wangsoub Fred J. Davis Geoffrey R. Mitchell Robert H. Olley 《Macromolecular rapid communications》2008,29(23):1861-1865
We show that small quantities of 1,3:2,4‐di(4‐chlorobenzylidene) sorbitol dispersed in poly(ε‐caprolactone) provide a very effective self‐assembling nanoscale framework which, with a flow field, yields extremely high levels of polymer crystal orientation. During modest shear flow of the polymer melt, the additive forms highly extended nano‐particles which adopt a preferred alignment with respect to the flow field. On cooling, polymer crystallisation is directed by these particles. This chloro substituted dibenzylidene sorbitol is considerably more effective at directing the crystal growth of poly(ε‐caprolactone) than the unsubstituted compound.
65.
66.
Crystallisation of aspirin via simulated pulmonary surfactant monolayers and lung‐specific additives 下载免费PDF全文
Michael J. Davies Zoe Taylor Andrew G. Leach James Ren Paul Gibbons 《Surface and interface analysis : SIA》2017,49(9):864-872
Pain is a prevalent condition that can have a serious impact upon the socioeconomic function of a population. Numerous methods exist to administer analgesic medication (e.g. aspirin) to the body however inherent drawbacks limit patient acceptability. The inhaled route offers promise to facilitate the administration of medication to the body. Here, we consider the crystallisation behaviour of aspirin, our model therapeutic agent, when in contact with material of relevance to the lung. Thus, our approach aims to better understand the interaction between drug substances and the respiratory tract. Langmuir monolayers composed of a mixed surfactant system were supported on an aqueous subphase containing aspirin (7.5 mg/ml). The surfactant film was compressed to either 5mN/m (i.e. inhalation end point) or 50 mN/m (i.e. exhalation end point), whilst located within a humid environment for 16 h. Standard cooling crystallisation procedures were employed to produce control samples. Antisolvent crystallisation in the presence or absence of lung‐specific additives was conducted. All samples were analysed via scanning electron microscopy and X‐ray diffraction. Drug‐surfactant interactions were confirmed via condensed Langmuir isotherms. Scanning electron microscopy analysis revealed plate‐like morphology. The crystallisation route dictated both the crystal habit and particle size distribution. Dominant reflections were the (100) and (200) aspects. The main modes of interaction were hydrogen bonding, hydrophobic associations, and van der Waals forces. Here, we have demonstrated the potential of antisolvent crystallisation with lung‐specific additives to achieve control over drug crystal morphology. The approach taken can be applied in respirable formulation engineering. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
67.
A. Majchrowski M.T. Borowiec E. Michalski J. Zmija V. Dyakonov H. Szymczak T. Zayarnyuk M. Baranski 《Crystal Research and Technology》2001,36(3):283-287
Potassium holmium tungstate KHo(WO4)2 crystal, as other tungstates, shows the high temperature irreversible structural phase transition. Owing to this, KHo(WO4)2 single crystals were grown due to spontaneous crystallisation with use of the High Temperature Solution Growth technique, which allows to lower the temperature of crystallisation below the temperature of the phase transition. K2W2O7 was used as a solvent. It provides a very wide temperature range of crystallisation and does not introduce additional impurities into the melt. The starting flux contained 20 mol% of KHo(WO4)2 dissolved in K2W2O7. It was found that potassium holmium double tungstate is pleochroic. The two different optical spectra: one spectrum for electrical vector of linearly polarised light parallel to optical Y axis (main spectrum) and second one for electrical vector perpendicular to Y axis were measured. 相似文献
68.
Sébastien Manneville 《Rheologica Acta》2008,47(3):301-318
Recent experimental techniques used to investigate shear banding are reviewed. After recalling the rheological signature of
shear-banded flows, we summarize the various tools for measuring locally the microstructure and the velocity field under shear.
Local velocity measurements using dynamic light scattering and ultrasound are emphasized. A few results are extracted from
current works to illustrate open questions and directions for future research.
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Sébastien MannevilleEmail: |
69.
PEI/PEEK blends have been prepared and analysed by DSC. The blends are compatible over the full composition range in that
amorphous samples are transparent and exhibit a single Tg varying with composition between the limits of the two components. The crystallisation kinetics of PEEK from the blend melt
has been measured by DSC but the technique is limited to blend compositions above 20% PEEK. The use of a polarised light microscope
to measure crystallization kinetics and melting behaviour of blends with compositions as low as 2 and 5% PEEK is discussed.
In general, since the extent rather than the rate of crystallization is measured directly, the polarised light microscopy
extends the measurement to slower rates and so to a wider temperature range.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
70.
A very interesting characteristic of FeSiB based amorphous alloys is its soft magnetic behavior. Most of these alloys remains soft along the crystallization process up to the nucleation of the iron borides. Examples of this are the widely studied Finemet and the FeSiBSn. In this work the crystallization of Fe76Si11B10Nb3 and Fe75Si11B10Nb3Sn1 is studied by means of X-ray diffraction, Mössbauer spectroscopy and coercive magnetic field measurements after one hour isothermal annealing at different temperatures. In the crystallization process of the latter alloy a hard magnetic phase appeared when the samples were annealed above 773 K. The soft magnetic behavior was recovered after annealing at 873 K. The hyperfine parameters as well as the X-ray diffraction patterns are reported. 相似文献