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1.
This paper deals with synthesis and assessment of the hydraulicity of C4A3Cr, analog phase C4A3S to , relevant to the phase chemistry and properties of sulfoaluminate cements. C4A3Cr, synthesized at 1250 °C is well crystallized phase, latently hydraulic, with hydration accelerated in the presence of C4A3S, or CS. Calorimetric curves show reciprocal influence of sulfate and chromate phase in hydration of C4A3S-C4A3Cr system. The total heat expressed at hydration is nearly the same for all specimens, but the rate of heat evolution depends
on the ratio of C4A3S/C4A3Cr phases. X-ray diffraction pattern and DTA curves showed that, increasing content of C4A3Cr in hydrating mixture results in a coexistence of two types of ettringite (chromate and sulfate ettringite) hydrogarnet,
gibbsite and monosulfate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Mojumdar S. C. Kozánková J. Chocholoušek J. Majling J. Fábryová D. 《Journal of Thermal Analysis and Calorimetry》2004,78(1):73-82
Fluoroapatite containing glass-ceramics were prepared from Li2O-CaO-CaF2-P2O5-SiO2 system. The glass was melted at 1480°C for 1 h. The object of observation was the preparing crystal phase of fluoroapatite
in amorphous glass matrix. The morphology of lithium disilicate glass-ceramics was studied by SEM. The crystal growth and
thermal properties of fluoroapatite were studied by X-ray diffraction and DTA. The more the content of P2O5, the more the presence of fluoroapatite particles. SEM investigation clearly indicated the phase separation and formation
of a primary crystalline phase of fluoroapatite in the studied glass-ceramics. DTA curves of the fluoroapatite samples exhibit
exothermic effects in the temperature range 337-694°C depending on the composition of the materials. The position of exothermic peak for lithium disilicate on DTA curves moves with increasing specific surfacetowards lower temperatures which points on its preferential surface crystallization. As far as physical qualities are concerned,
mainly color and gloss, the best qualities of all observed materials belong to glass-ceramics with 10% P2O5.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Mojumdar S. C. Kozánková J. Chocholoušek J. Majling J. Nemecek V. 《Journal of Thermal Analysis and Calorimetry》2004,78(1):145-152
The conditions to fabricate the bulk porous specimens have been studied on account of sodium borosilicate (NBS) glasses. Glass
composition, heat treatment at phase separation and TiO2 addition have been considered in this study. Original glass samples of composition in mol%: sample A: 9.19 Na2O - 23.58 B2O3 - 67.23 SiO2, sample B: 9.29 Na2O - 3.17 TiO2 - 23.82 B2O3 - 63.72 SiO2 were prepared by melting reagent grade chemicals (Na2CO3, HBO3, SiO2 and AgNO3) in platinum crucibles at 1480°C for 1 h in air. The melts were poured onto stainless steel plates and were annealed at 500°C
for 0.5 h after cooling. Thus, obtained samples were phase separated at 700°C for 2, 15, 25 and 50 h to study their microstructure
by scanning electron microscope (SEM). Besides the direct study of the microstructure by SEM, information on glass structural
changes of samples are provided by measuring in situ changes by the optical transmittance thermal analysis. The isothermal
measurements were carried out at 700, 720 and 740°C. The temperature of phase separation, the leaching and nucleator addition
(TiO2), significantly influence the microstructure of the resulting leached product. TiO2 additive seems to suppress crystallization of cristobalite: especially at the extended above heat treatment phase separation
runs. The phase-separated domains of glasses containing above 80 moles of SiO2 are so small that it is very hard to observe them by SEM. The glass composition in our case was selected in a way to have
relatively large phase separated areas easily observed by SEM at magnification 20 000·. The influence of TiO2 is not too pronounced. It seems to suppress the cristobalite crystallization, especially of longer heating runs. The image
analysis of leached glasses shows the prevailing content of the skeletal phase in a comparison to pores. The TiO2 content diminishes the content of the skeletal phase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
5.
In our work single crystals of Mg4.5Na7(P2O7)4 were prepared, pulverized, pressed into pellets and sintered in order to measure the electrical conductivity of polycrystalline specimens. The conductivity was also measured on glassy specimens obtained by the melting of previously prepared crystals. The electrical conductivities at 25°C with values of the order of 10−16 Ω−1 cm−1 for polycrystalline samples and a value of the order of 10−14 Ω−1 cm−1 for glass, show that the glassy phase of Mg4.5Na7(P2 because of its greater molar volume and loosely packed structure, is a better matrix for ionic motion. 相似文献
6.
The virtual microstructures relevant to lithiumdisilicate glass crystallization have been created as an environment to compute the light scattering. The input data in computations include the number density of crystals, refractive indices of involved glassy and crystalline phases, the wavelength of the incident beam radiation, and the virtual sample slab thickness. The computations are performed under a number of simplifying conditions. They treat cases with proposed constant number densities of crystals, assuming their random volume distribution. The shape of the crystals is approximated by spheres. The results are expressed graphically in the form of theoretical optical transmission (OT) patterns, as they evolve on the crystal size axis. They reveal an influence of input data on computed OT. As evident from computations, some sets of input data will favor the real OT method's detection limits. The opposed sets of data will aid following the crystallization to the higher sample crystallinity degree α. 相似文献
7.
LiMgPO4 is orthorhombic, space groupPnma,a=10.147(2),b=5.909(2),c=4.692(2)×10–10 m,D
m
=3000(8),D
x
=2980 kg m–3,Z=4,R=4.8% for 1262 observed reflections. The structure contains tetrahedral PO4 and octahedral LiO6 and MgO6 groups. It belongs to the ordered olivine-type structures, since the inversion site is occupied by Li+ ions and the mirror site is taken by Mg2+ ions. The distortion of polyhedra is caused mainly by the adjustment stresses between the different polyhedral dimensions and by the sharing of edges. Octahedral LiO6 share six and MgO6 share three common edges. The sharing of the O-O edges contributes to the stability of the bridging arrangements. The corresponding average distances of the O-O bridges are 2.432, 2.479, 2.883, and 3.028×10–10 m, while the average O-O distances in the PO4, MgO6, and LiO4 polyhedra are 2.512,2.921, and 3.015 × 10–10 m, close to the ideal values 2.531, 2.970, and 3.026×10–10 m respectively. The structure field of the olivine-type compounds plotted as a function of ionic radii in radius space is specified in relation to the-K2SO4, spinel, and K4NiF4 type structures. From the overlap of the structure fields, the high-pressure transformations of the olivine compounds are considered. 相似文献
8.
L. Majling J. Žofka R. A. Eramzhyan V. N. Fetisov 《Czechoslovak Journal of Physics》1991,41(11):1083-1089
Signatures and behaviour of s–1s configurations are qualitatively discussed. Suppression of baryon-decay channels and an enhancement of cluster-decay channels are the relevant signals. The hypernuclear-quanta from
constitute a novel example of the decay of s–1 s–1s configuration.Dedicated to the memory of M. Gmitro.We dedicate this article to our colleague and friend Dr. Marian Gmitro, whose premature death brought a profound grief upon our community. During years, his activities and knowledge in meson-nuclear physics have been very helpful in further development of hypernuclear physics. Also, his role in an efficient topical collaboration between Soviet and Czechoslovak physicists is to be greatly acknowledged. 相似文献
9.
V. N. Fetisov L. Majling J. Žofka R. A. Eramzhyan 《Zeitschrift für Physik A Hadrons and Nuclei》1983,314(2):239-249
The available experimental data on the excitation functions (EF) of the 1p-shellΛ-hy-pernuclei in (K ?, π?) reactions atθ π = 0° has been analysed in terms of shell model and weak coupling scheme. It is substantiated by the experimental data on the neutron spectroscopic factors and on the fragmentation of nuclear hole excitations. The pronounced nuclear spectroscopic characteristics in the hypernuclear spectra are indicative of a weak coupling ofΛ-hyperon with nuclear subsystem. The analysis has made it possible to determine the difference is single-particle energies ofΛ-hyperon in the 1p- and 1s-states and to obtain additional evidence for the smallness of theΛ-nucleus spin-orbit interaction. The resonance structure of EF of hypernuclei, which were not studied in (K ?,π 0 ? ) reactions, is predicted. The interrelated aspects of the studies of the (K ?,π 0 ? ), (K ?,π 0 ? β′), and (K ?, π+) reactions which are of interest to spectroscopy ofΛ-andΣ-hypernuclei are discussed. 相似文献
10.
R. A. Eramzhyan V. N. Fetisov L. Majling M. Sotona J. Žofka 《Czechoslovak Journal of Physics》1982,32(3):326-329
In the translationally invariant shell model the supermultiplet structure of the 1 states ofp-shell hypernuclei is studied. Fragmentation of the strangeness analogue state is discussed and the spectroscopic amplitudes for all decay channels are estimated.Presented at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981. 相似文献