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排序方式: 共有51条查询结果,搜索用时 15 毫秒
1.
Noriyuki Asakura Toshiaki Kamachi Ichiro Okura 《Research on Chemical Intermediates》2006,32(3-4):341-355
The behavior of redox molecules in solution that was not detected by electrochemical techniques was measured by a highly-sensitive electrochemical quartz crystal microbalance (EQCM) technique that has been improved in this study to obtain a high sensitivity of EQCM measurement in solution. The improved EQCM technique allowed to monitor the motion of a redox molecule, that is an access of the molecule to an electrode surface and repulsion from the surface during redox. An EQCM technique currently in use has measured adsorption of redox molecules on an electrode surface or polymerization on the surface caused by a chemical reaction following redox, which exhibits an enough large mass change response to detect with an EQCM measurement. However, access and repulsion of redox molecule, which is a slight motion of the molecule near on electrode surface, has not been detected and investigated by an EQCM technique, because the mass change response seems to be very small. In this study, the redox behavior of methyl viologen on a bare gold surface, pyridinethiol surface and methylpyridinethiol surface was investigated. Although the three electrodes give the same cyclic voltammogram of methyl viologen, the three are different in QCM response recorded at the same time as the voltammetry. Access/repulsion of methyl viologen within an electrical double layer was monitored by the highly-sensitive EQCM technique. 相似文献
2.
Because Nitrosomonas europaea contains ammonia-oxidizing enzyme, nitrite reductase, and nitrous oxide reductase, the conversion of ammonia to dinitrogen
was tried with different reaction conditions. In aerobic reaction conditions, ammonium was converted to nitrite (NO
2
−
), while under oxygen-limiting or oxygen-free conditions, NO
2
−
-N formed from ammonia oxidation by N. europaea was reduced to N2O and dinitrogen with 22% conversion. During denitrification, optimal pH for the production of N2O and dinitrogen was found to be 7.0–8.0. Dinitrogen was not produced in acidic pH<7.0. A low partial oxygen pressure as well
as oxygen-free conditions are favorable for high production of dinitrogen. 相似文献
3.
Fumihiko Hasumi Yasumitsu Miyamoto Ichiro Okura 《Applied biochemistry and biotechnology》1995,55(1):1-4
Glutamate synthesis by reductive amination of 2-oxoglutarate was performed by the combination of NADH regeneration system
and glutamate dehydrogenase (GluDH). The conversion of 2-oxoglutamate to glutamate was 98% after 3 h, and the turnover number
of NAD+was 17. 相似文献
4.
Fumihiko Hasuni Katsunori Fukuoka Shuichi Adachi Yasumitsu Miyamoto Ichiro Okura 《Applied biochemistry and biotechnology》1996,56(3):341-344
Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine
dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by
the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to
leucine was 60% after 1.5 h. 相似文献
5.
An optical oxygen-sensing material based on the fluorescence intensity changes of pyrene-1-butyric acid (PBA) chemisorption film has been developed and characterised. The fluorescence intensity of PBA film decreased with increase of oxygen concentration. The I0/I100 value of PBA film is estimated to be 6.14±0.15 and large Stern-Volmer constant (KSV=0.028±0.13 Torr−1) is obtained. After irradiation for 24 h with 150 W tungsten lamp, little changes of oxygen-sensing properties were observed. These results indicate that PBA film is highly oxygen-sensitive and photostability device. The response times of the PBA chemisorption film were 10.0 s for switching from argon to oxygen, and 53.0 s for switching from oxygen to argon. Moreover, the optical sensor based on the PBA chemisorption film was applied to the measurement of oxygen concentration in aqueous solution. 相似文献
6.
Abstract— Photodynamic efficiency of protoporphyrin IX (PP) accumulated in HeLa cells by the incubation of PP with HeLa cells was compared with that of accumulated PP formed from 5-aminolevulinic acid (ALA) as a precursor. The ALA-induced PP was photodynamically more efficient than exogenous PP. The difference is caused by monomelic PP concentration and PP localization site in HeLa cells. Exogenous PP was accumulated mainly in plasma membrane, and the membrane was strongly damaged by irradiation. The ALA-induced PP was selectively accumulated in mitochondria and inactivated the mitochondrial function by irradiation. 相似文献
7.
Dieter Wohrle Jörg Gitzel Gerhard Krawczyk Eishun Tsuchida Hiroyoki Ohno Ichiro Okura 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10-11):1227-1254
Metal complexes of covalently bound porphyrins are used as sensitive probes for several investigations. Substituted derivatives of tetraphenyl-porphin, phthalocyanine, and naphthalocyanine are synthesized at positively and negatively charged as well as uncharged polymers. The photo-redox activities were studied under irradiation with visible light in the presence of a donor and an acceptor. The triplet life times of covalently bound porphyrin moieties are strongly enhanced compared with the analogous monomeric porphyrins. In addition, the polymer binding results in higher photocatalytic activity. The electron-transfer reactions of Mn(III)-containing porphyrins using the reducing agent dithionite are strongly influenced by the polymer environment. In contrast to monomeric Mn(III)-porphyrins, the porphyrins containing polymers exhibit a two-step reduction which may be due to the change of the conformation of the polymer coil. The catalytic epoxidation of 2,5-dihydrofuran with hypochlorite with formation of 3,4-epoxytetrahydrofuran occurs with water-soluble porphyrins in water. No influence of the polymer environment exists. The different reactions require reaction times from milliseconds up to hours. 相似文献
8.
9.
Manuel van Gemmeren Marino Börjesson Andreu Tortajada Shang-Zheng Sun Keisho Okura Prof. Ruben Martin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6658-6662
A switchable site-selective catalytic carboxylation of allylic alcohols has been developed in which CO2 is used with dual roles, both facilitating C−OH cleavage and as a C1 source. This protocol is characterized by its mild reaction conditions, absence of stoichiometric amounts of organometallic reagents, broad scope, and exquisite regiodivergency which can be modulated by the type of ligand employed. 相似文献
10.