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41.
For air-cleaning, TiO2 photocatalysis represents one of the very efficient advanced oxidation processes (AOPs) that can decompose chemically and microbiologically stable volatile organic compounds (VOCs). However, the photocatalytic activity of nanocrystalline TiO2 powders can be significantly suppressed due to TiO2’s poor adsorption characteristics for organic compounds and its relatively low surface area. The present study sought to solve this problem by immobilising nanocrystalline TiO2 in the porous silicate substrate. Two titania sources were used in an aqueous solution form: a suspension from a TiO2 producer in Slovenia, Cinkarna Celje (CC-40) and a TiO2 sol, prepared by a low-temperature synthesis developed at the University of Nova Gorica (TiO2-UNG). Two different types of mesoporous silica were used: SBA-15 with an ordered hexagonal pore arrangement and KIL-2 with disordered inter-particle mesoporosity. The structural characteristics, adsorption properties and photocatalytic activity of catalysts deposited on aluminium plates as thin films were investigated. CC-40 exhibited higher adsorption and photocatalytic activity than TiO2-UNG due to the greater quantity of Ti-OH groups on its surface. The addition of mesoporous silica led to higher adsorption and catalytic activity for both TiO2 sources. SBA-15 was more efficient than KIL-2.  相似文献   
42.
The interaction between mucin and ions has been investigated by employing the quartz crystal microbalance technique with measurement of energy dissipation. The study was partially aimed at understanding the adsorption of mucin on surfaces with different chemistry, and for this purpose, surfaces exposing COOH, OH, and CH(3) groups were prepared. Mucin adsorbed to all three types of functionalized gold surfaces. Adsorption to the hydrophobic surface and to the charged hydrophilic surface (COOH) occured with high affinity despite the fact that in the latter case both mucin and the surface were negatively charged. On the uncharged hydrophilic surface exposing OH groups, the adsorption of mucin was very low. Another aim was to elucidate conformational changes induced by electrolytes on mucin layers adsorbed on hydrophobic surfaces from 30 mM NaNO(3). To this end, we investigated the effect of three electrolytes with increasing cation valance: NaCl, CaCl(2) and LaCl(3). At low NaCl concentrations, the preadsorbed layer expands, whereas at higher concentrations of NaCl the layer becomes more compact. This swelling/compacting of the mucin layer is fully reversible for NaCl. When the mucin layer instead is exposed to CaCl(2) or LaCl(3), compaction is observed at 1 mM. For CaCl(2), this process is only partially reversible, and for LaCl(3), the changes are irreversible within the time frame of the experiment. Finally, mucin interaction with the DTAB cationic surfactant in an aqueous solution of different electrolytes was evaluated with turbidimetry measurements. It is concluded that the electrolytes used in this work screen the association between mucin and DTAB and that the effect increases with increasing cation valency.  相似文献   
43.
The Coulomb gauge in nonabelian gauge theories is attractive in principle, but beset with technical difficulties in perturbation theory. In addition to ordinary Feynman integrals, there are, at 2-loop order, Christ–Lee (CL) terms, derived either by correctly ordering the operators in the Hamiltonian, or by resolving ambiguous Feynman integrals. Renormalization theory depends on the sub-graph structure of ordinary Feynman graphs. The CL terms do not have a sub-graph structure. We show how to carry out renormalization in the presence of CL terms, by re-expressing these as ‘pseudo-Feynman’ integrals. We also explain how energy divergences cancel.  相似文献   
44.
Chitosan (CS) and poly(acrylic acid) (PAA) were crosslinked by an ionic gelation method to form super absorbent polymers (SAPs). CS and PAA form amide bonds between the amino and carboxyl groups. The CS-PAA copolymers were synthetically engineered by varying the feed ratios of the prepolymer units. The copolymer materials possess tunable sorption and mucoadhesive properties with a backbone structure resembling proteinaceous materials. The sorption properties of the copolymers toward methylene blue (MB) in aqueous solution were studied using UV-Vis spectrophotometry at ambient pH and 295 K. The copolymers showed markedly varied interactions with MB, from physisorption- to chemisorption-like behavior, in accordance with their composition, surface area, and pore structure characteristics. The sorption isotherms were evaluated with the Sips model to provide estimates of the sorption properties. The sorbent surface area (271 and 943 m2/g) and the sorption capacity (Qm = 1.03 and 3.59 mmol/g) were estimated for the CS-PAA copolymer/MB systems in aqueous solution.  相似文献   
45.
The possibility of using a novel comb polymer consisting of a chitosan backbone with grafted 44 units long poly(ethylene oxide) side chains for reducing nonspecific protein adsorption to gold surfaces functionalized by COOH-terminated thiols has been explored. The comb polymer was attached to the surface in three different ways: by solution adsorption, covalent coupling, and microcontact printing. The protein repellent properties were tested by monitoring the adsorption of bovine serum albumin and fibrinogen employing surface plasmon resonance and imaging null ellipsometry. It was found that a significant reduction in protein adsorption is achieved as the comb polymer layer is sufficiently dense. For solution adsorption this was achieved by adsorption from high pH solutions. On the other hand, the best performance of the microcontact printed surfaces was obtained when the stamp was inked either at low or at high pH. For a given comb polymer layer thickness/poly(ethylene oxide) density, significant differences in protein repellent properties were observed between the different preparation methods, and it is suggested that a reduction in the mobility of the comb polymer layer generated by covalent attachment favors a reduced protein adsorption.  相似文献   
46.
A new industrially viable process for the preparation of 1β‐(Ntert‐butyl carbamoyl)‐4‐aza‐5α‐androst‐1‐ene‐3‐one, also known by the generic name finasteride ( 6 ) from the new azaandrostane derivatives such as 1β‐(Ntert‐butyl carbamoyl)‐4‐benzoyl‐4‐aza‐5α‐androstane‐3‐one ( 4 ), 1β‐(Ntert‐butyl carbamoyl)‐4‐benzoyl‐4‐aza‐5α‐androst‐1‐ene‐3‐one ( 5 ) is reported. In this process, benzoyl group is demonstrated as a novel protecting group for lactamic NH group. The structures of newly prepared compounds were established on the basis of spectral data (IR, 1H‐NMR, and MS).  相似文献   
47.
A simple one pot synthetic method for the isomerization of cephem double bond from the natural 3‐position to 2‐cephem positions is affected by silylation. Thus cephalosporin acids are treated with Ntrimethylsilylacetamide (MSA) or N,O‐bis(trimethylsilyl)acetamide (BSA) and the resulting silyl esters are treated with triethylamine at ambient temperature in the same pot to afford Δ2‐cephalosporins, which are potentially related compounds in cephalosporin antibacterial compounds.  相似文献   
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