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21.
Marlene M. Hurley 《School science and mathematics》2001,101(5):259-268
Based upon current research needs indicated from recent literature reviews, this integrative review concentrates on two of the perceived major impediments to integrating science and mathematics: The lack of evidence to support integration and the lack of a definition for integration. Using mixed methodology, this review found quantitative evidence favoring integration from a meta-analysis of 31 studies of student achievement, qualitative evidence revealing the existence of multiple forms of integration, and historical evidence of publishing patterns from across the 20th century. The forms of integration were identified and defined; differential effects were identified both between forms and between science and mathematics when the forms were analyzed by effect size. Additional research implications and suggestions for future research were also identified. 相似文献
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Celina Lopes Duarte Marlene Sotto-Mayor Flues Szeles 《Journal of Radioanalytical and Nuclear Chemistry》1994,177(1):73-79
A comparative study of source preparation techniques to determine uranium isotopic composition by alpha spectrometry, namely electrodeposition and chemical stripping with polymeric membranae containing trioctylphosphine oxide (TOPO), is presented. The mean yield obtained for electrodeposition and TOPO deposition were 85% and 74%, respectively. The mean activity ratio235U/238U were 0.044 and 0.042 and the ratio234U/238U were 0.994 and 1.009, using electrodeposition and TOPO deposition techniques, respectively. The method of uranium separation from urine using an ion-exchange resin Dowex 1×8, chloride form and citrate form, was also studied. The obtained global yields of these methods were 50% and 41%, respectively. 相似文献
25.
Abu-Bakar Ariza S. Cran Marlene J. Moinuddin Khalid A. M. 《Journal of Thermal Analysis and Calorimetry》2019,136(2):447-459
Journal of Thermal Analysis and Calorimetry - Differential scanning calorimetry (DSC) technique is used to study the solid reactions in the 2024 Al–Cu–Mg and 2014... 相似文献
26.
T. Marek Cs. Szeles G. Molnár J. Borossay A. Vértes K. G. Lynn 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(2):329-335
We studied the long-term (190 hours) behaviour of [Zn(propyltetrazole)6](BF4)2 single crystal under high-vacuum (HV) conditions (10–8 torr) with a depth-sensitive technique of positron annihilation spectroscopy (PAS). The obtained data indicate the slow formation of a new near-surface structure which is formed by the decomposition of the [Zn(propyltetrazole)6]2+ ions. The assumption of such a decomposition process was confirmed by additional mass spectroscopic measurements. 相似文献
27.
Marlene Costa Sonia Losada-Barreiro Ftima Paiva-Martins Carlos Bravo-Díaz 《Molecules (Basel, Switzerland)》2021,26(19)
Surfactants have been used for decades in the food industry for the preparation of lipid-based emulsified food stuffs. They play two main roles in the emulsification processes: first they decrease the interfacial tension between the oil and water, facilitating droplet deformation and rupture; second, they reduce droplet coalescence by forming steric barriers. However, addition of surfactants to binary oil-water mixtures also brings up the formation of three-dimensional interfacial layers, surrounding each emulsion droplet, that significantly alter chemical reactivity. This is the case, for instance, in the inhibition reaction between antioxidants and the lipid radicals formed in the course of the spontaneous oxidation reaction of unsaturated lipids, which are commonly employed in the preparation of food-grade emulsions. The rate of the inhibition reaction depends on the effective concentrations of antioxidants, which are mostly controlled by the amount of surfactant employed in the preparation of the emulsion. In this work, we analyze the effects of the surfactant Tween 20 on the oxidative stability and on the effective concentrations of two model antioxidants derived from cinnamic acid, determining their interfacial concentrations in the intact emulsions to avoid disrupting the existing equilibria and biasing results. For this purpose, a recently developed methodology was employed, and experimental results were interpreted on the grounds of a pseudophase kinetic model. 相似文献
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Dipl.‐Chem. Vikas Aggarwal Dipl.‐Chem. Linus F. Reichenbach Dipl.‐Chem. Mirja Enders Dr. Thierry Muller Dipl.‐Ing. Simone Wolff Marlene Crone Prof. Dr.‐Ing. Michael Türk Prof. Dr. Stefan Bräse 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12794-12799
The optimized synthesis of a range of cyclooctadiene‐stabilized Pt complexes that contained different perfluoro‐alkane chains, [Pt(cod)Me(CnF2n+1)], is presented. These metal–organic compounds were employed in the so‐called supercritical fluid reactive deposition (SFRD) in CO2 under reductive conditions to generate metallic nanoparticles on aluminum oxide as a porous support. Thus, Al2O3‐supported Pt nanoparticles with a narrow particle‐size distribution were obtained. At a reduction pressure of 15.5 MPa and a temperature of 353 K, particle diameters of d50=2.3–2.8 nm were generated. Decreasing the pressure during the reduction reaction led to slightly larger particles whilst decreasing the amount of organometallic precursor in CO2 yielded a decrease in the particle size from x50=3.2 nm to 2.6 nm and a particle‐size distribution of 2.2 nm. Furthermore, substitution of the CH3 end group by the CnF2n+1 end groups led to a significant drop in Pt loading of about 50 %. Within the series of perfluorinated end groups that were considered, the Pt complex that contained a branched perfluoro‐isopropyl group showed the most‐interesting results when compared to the control precursor, [Pt(cod)Me2] ( 1 ). 相似文献
30.
Fisher Douglas B. Espidel Joussef Huerta Marlene Randall Leslie Goldman Jon 《Transport in Porous Media》1999,35(2):189-204
The purpose of this work is to present the results of the phase behavior study for a live heavy oil during a pressure depletion process using magnetic resonance imaging (MRI) as a tool to characterize foamy oil phenomena. The experiments were carried out in the pressure range of 13.1 to 1.4MPa. Signal intensity images were obtained at each pressure and with respect to time, that is, approximately for a total time of 3h after each pressure change. It is possible to see a variation in intensity across the sample. These changes can be associated with changes in mobility as well as segregation of the oil. It was also possible to observe that what we trust is the formation of gas channels at the last two pressure values, as it comes out of solution. A correlation between the transverse relaxation time T2 and temperature was established with the aim of producing one between T2 and viscosity. In this way viscosity maps for the live oil were obtained as a function of pressure and time. It was observed that above the bubble point, the viscosity maps varied from low to high to low with respect to time for the same pressure. Below the bubble point the situation is reverse. The viscosity map changes from high to low to high with respect to time for the same pressure. The study shows the potential use of MRI to follow viscosity changes during pressure depletion test in a PVT MRI cell. 相似文献