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31.
Fikret Kirkbir Hideaki Murata Douglas Meyers S. Ray Chaudhuri 《Journal of Sol-Gel Science and Technology》1998,13(1-3):311-316
The objectives of this investigation are to show the feasibility of producing large monoliths with minimal shrinkage at subcritical conditions, and to understand the drying behavior. Crack-free SiO2 monoliths (5.6 cm in diameter and 25 cm in length) were repeatedly dried with little shrinkage (<2%). Some gels showed increasing shrinkage with decreasing pressure. However, this shrinkage was reduced to negligible levels at conditions considerably less than supercritical pressure by increasing both the pore size and the gel strength. This moderate pressure drying (MPD) process may make aerogel fabrication economically more feasible due to reduced pressure chamber costs. 相似文献
32.
Using certain well-known properties of chebyshev polynomials, a simple and highly efficient approach to evaluate eigenvalue in radiation transport is presented. The spectrum of eigenvalues has been studied for slabs with isotropic scattering of different magnitudes of the cross section parameter c (i.e., the mean number of neutrons emitted per collision). It is shown that in the presence of the chebyshev polynomial approximation (TN) there are both discrete and continuum of eigenvalues. It is found that the TN method gives very good agreement with conventional spherical harmonics approximation (PN). 相似文献
33.
Fikret Koç 《Tetrahedron》2004,60(38):8465-8476
Rh-catalyzed tandem hydroformylation/reductive amination sequences (hydroaminomethylation) starting from olefins are applied to the synthesis of new polyamine dendrimer units using both convergent and divergent strategies in solution as well as on solid support. 相似文献
34.
Horticultural waste collected from a landscape company in Singapore was utilized as the substrate for the production of laccase
under solid-state fermentation by Trametes versicolor. The effects of substrate particle size, types of inducers, incubation temperature and time, initial medium pH value, and
moisture content on laccase production were investigated. The optimum productivity of laccase (8.6 U/g substrate) was achieved
by employing horticultural waste of particle size greater than 500 μm and using veratryl alcohol as the inducer. The culture
was at 30 °C for 7 days at moisture content of solid substrate of 85% and initial pH 7.0. The decolorization was also investigated
in order to assess the degrading capability of the ligninolytic laccase obtained in the above-mentioned cultures. The decolorization
degree of a model dye, phenol red, was around 41.79% in 72 h of incubation. By far, this is the first report on the optimization
of laccase production by T. versicolor under solid-state fermentation using horticultural waste as the substrate. 相似文献
35.
The exchange of heat between two fluids is established by radial rotating pipe or a channel. The hotter fluid flows through
the pipe, while the cold fluid is ambient air. Total length of pipe is made up of multiple sections of different shape and
position in relation to the common axis of rotation. In such heat exchanger the hydraulic and thermal irreversibility of the
hotter and colder fluid occur. Therefore, the total entropy generated within the radial rotating pipe consists of the total
entropy of hotter and colder fluid, taking into account all the hydraulic and thermal irreversibility of both fluids. Finding
a mathematical model of the total generated entropy is based on coupled mathematical expressions that combine hydraulic and
thermal effects of both fluids with the complex geometry of the radial rotating pipe. Mathematical model follows the each
section of the pipe and establishes the function between the sections, so the total generated entropy is different from section
to section of the pipe. In one section of the pipe thermal irreversibility may dominate over the hydraulic irreversibility,
while in another section of the pipe the situation may be reverse. In this paper, continuous analytic functions that connect
sections of pipe in geometric meaning are associated with functions that describe the thermo-hydraulic effects of hotter and
colder fluid. In this way, the total generated entropy of the radial rotating pipe is a continuous analytic function of any
complex geometry of the rotating pipe. The above method of establishing a relationship between the continuous function of
entropy with the complex geometry of the rotating pipe enables indirect monitoring of unnecessary hydraulic and thermal losses
of both fluids. Therefore, continuous analytic functions of generated entropy enable analysis of hydraulic and thermal irreversibility
of individual sections of pipe, as well as the possibility of improving the thermal–hydraulic performance of the rotating
pipe consisting of n sections. Analytical modeling enabled establishing of a mathematical model of the total generated entropy
in a radial rotating pipe, while the generated entropy of models with radial rotating pipe were determined by experimental
testing, with comparisons of the achieved results. 相似文献
36.
Summary An extracellular lipase was produced by Bacillus coagulans by solid-state fermentation. Solid waste from melon was used as the basic nutrient source and was supplemented with olive
oil. The highest lipase production (78,069 U/g) was achieved after 24h of cultivation with 1% olive oil enrichment. Enzyme
had an optimal activity at 37°C and pH 7.0, and sodium dodecyl sulfate increased lipase activity. NH 4NO3 increased enzyme production, whereas organic nitrogen had no effect. The effect of the type of carbon sources on lipolytic
enzyme production was also studied. The best results were obtained with starch and maltose (148,932 and 141,629 U/g, respectively),
whereas a rather low enzyme activity was found in cultures grown on glucose and galactose (approx 118,769 and 123,622 U/g,
respectively). Enzyme was inhibited with Mn+2 and Ni+2 by 68 and 74%, respectively. By contrast, Ca+2 enhanced enzyme production by 5%. 相似文献
37.
The aim of this study is to analyze the effects of project‐based learning on students' academic achievement, attitude, and retention of knowledge in relation to the subject of “Electricity in Our Lives” in a fourth‐grade science course. The study was conducted in a quasi‐experimental design as a “pre‐test, post‐test with control group.” In the experimental group, the unit was taught through the project‐based learning method. The measuring tools were administered to both groups before and after the applications. To perfectly analyze the “process” of the method, seven different learning assessment “forms” were administered to the students. The findings of the forms indicated that the students learn to construct their own learning and to evaluate changes in their own behavior through the application of the method. The application of different methods between both groups had a statistically significant effect in terms of academic achievement, (F(1,112) = 46.78, p = .000) and of retention of knowledge (F(1,112) = 35.24, p = .000). However, there were no statistically significant effects from being in different groups for the attitudes of students (F(1,112) = .99, p = .321). For the students, being in the project‐based learning groups resulted in better academic achievement and retention of knowledge than being in the traditional teaching group. 相似文献
38.
Turan Nevin Buldurun Kenan Türkan Fikret Aras Abdulmelik Çolak Naki Murahari Manikanta Bursal Ercan Mantarcı Asim 《Molecular diversity》2022,26(5):2459-2472
Molecular Diversity - Schiff bases are well-known compounds for having significant biological properties. In this study, a new Schiff base ligand and its metal complexes were synthesized, and their... 相似文献
39.
Oxygen Reduction Reaction in a Droplet on Graphite: Direct Evidence that the Edge Is More Active than the Basal Plane
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Anli Shen Yuqin Zou Prof. Qiang Wang Prof. Robert A. W. Dryfe Prof. Xiaobing Huang Shuo Dou Prof. Liming Dai Prof. Shuangyin Wang 《Angewandte Chemie (International ed. in English)》2014,53(40):10804-10808
Carbon‐based metal‐free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium have been extensively investigated with the aim of replacing the commercially available, but precious platinum‐based catalysts. For the proper design of carbon‐based metal‐free electrocatalysts for the ORR, it would be interesting to identify the active sites of the electrocatalyst. The ORR was now studied with an air‐saturated electrolyte solution droplet (diameter ca. 15 μm), which was deposited at a specified position either on the edge or on the basal plane of highly oriented pyrolytic graphite. Electrochemical measurements suggest that the edge carbon atoms are more active than the basal‐plane ones for the ORR. This provides a direct way to identify the active sites of carbon materials for the ORR. Ball‐milled graphite and carbon nanotubes with more exposed edges were also prepared and showed significantly enhanced ORR activity. DFT calculations elucidated the mechanism by which the charged edge carbon atoms result in the higher ORR activity. 相似文献
40.
Fikret Anli Faruk Ya?a Hakan Öztürk 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,101(1):129-134
The critical slab problem has been studied in one-speed neutron transport equation with isotropic scattering by using the TN method. TN moment criticality solutions are obtained for the uniform finite slab using Mark and Marshak type vacuum boundary conditions. Results obtained by TN method, using the two type boundary conditions mentioned above, were presented in the Tables and also the Tables included the results obtained by PN method for the comparisons. 相似文献