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101.
Konstantina Tsaousi Athanasios A. Koutinas Argyro Bekatorou Paul Loukatos 《Applied biochemistry and biotechnology》2010,162(2):594-606
Low-cost dried yeasts immobilized on delignified brewers' spent grains for use in wine making and brewing were produced by
simple thermal drying techniques. To optimize the thermal drying process, vacuum and air stream conditions were examined.
Drying of thin layers of the biocatalysts was performed at low (30–38 °C) and high temperatures (40–70 °C). The fermentation
efficiency of the thermally dried biocatalysts was acceptable, with immobilized cells showing a significantly higher thermotolerance
compared with free cells. Immobilized cells dried at high temperatures presented slightly improved glucose fermentation efficiency
compared with the low-temperature dried biocatalysts. Gas chromatography–mass spectrometry analysis of aroma volatiles of
the fermented products revealed an increase of esters, lower higher alcohol formation, and significantly lower concentration
of carbonylic compounds. 相似文献
102.
Anastasia Paulidou Konstantina Yannakopoulou Irene M. Mavridis 《Journal of inclusion phenomena and macrocyclic chemistry》2010,68(3-4):297-303
Crystallization of glutaric anhydride in the presence of β-cyclodextrin (βCD) from aqueous solution resulted in crystals of the glutaric acid/βCD inclusion complex. The result was verified by NMR spectroscopic experiments, which moreover showed that βCD does not protect glutaric anhydride from hydrolysis. The structure determination by X-ray crystallography revealed a host:guest ratio of 1:1 and crystal packing identical to that of natural βCD, i.e., herring bone packing, as is common for guest molecules of small size. Glutaric acid has partial occupancy in the complex and it is disordered in three positions and conformations inside the cavity. All three conformations are stabilised by: (a) Interactions among its carboxyl groups and the host’s primary side hydroxyls pointing towards the cavity, thus justifying the conformations of the latter and (b) by two water molecules located on either side of the cavity, as well as hydroxyl groups of neighbouring hosts. In all conformations the guest is not extended, oxygen atoms between the two carboxyl groups being within H-bond distance. 相似文献
103.
Maffeo D Leondiadis L Mavridis IM Yannakopoulou K 《Organic & biomolecular chemistry》2006,4(7):1297-1304
The complexation of penicillin (1a-c) and cephalosporin (2a,b) antibiotics with cyclodextrins (CDs), both natural [beta-CD (3b) and gamma-CD (3c)] and carboxylated [heptakis(6-oxycarbonylethylthio-6-deoxy)-beta-CD sodium salt (4b) and octakis(6-oxycarbonylethylthio-6-deoxy)-gamma-CD (4c) sodium salt], has been studied at neutral pH. Penicillins [ampicillin (1a), amoxicillin (1b) and dicloxacillin (1c) form inclusion complexes with the above CDs, as was shown by extensive NMR spectroscopic studies, whereas cephalosporins (cephalexin, cefadroxil) do not. Inclusion of the penicillins into either 3b or 4b was not accompanied by significant chemical shift changes in the 1H NMR spectra. On the contrary, with the wider 3c and its derivative 4c inclusion was evidenced by both chemical shift displacements of the cavity protons and intermolecular interactions, indicating the formation of primarily 1:1 guest-host inclusion complexes. The binding constants for 1a/3c, 1a/4c and 1c/3c were calculated as 19 +/- 4, 17 +/- 0.9 and 622 +/- 200 M(-1), respectively. With 4c, a 1:2 stoichiometry was also found. In addition, simultaneous formation of aggregates by external association takes place in solution, as shown by the ESI-mass spectrometric data. Studies on the hydrolysis of ampicillin under pseudo-first order conditions using an excess of 3c, 4c and of linear maltoheptaose at pH 7 showed that the drug hydrolysed at a similar rate in all cases. In the presence, however, of beta-lactamase enzyme and the carboxylated host 4c, ampicillin degraded twice as slowly (0.008 h(-1)) as in the presence of beta-lactamase alone (0.017 h(-1)). This was explained by the effective protection provided by both inclusion and external association of the host. The interaction, therefore, of penicillins with carboxylated CDs may present a means to lessen the chemical instability of these drugs in the presence of beta-lactamase enzymes. 相似文献
104.
Synthesis of oxadiazoloquinoxaline,oxathiadiazoloquinoxaline and oxadiazolobenzothiazine derivatives
Konstantina C. Fylaktakidou Konstantinos E. Litinas Athanasios Saragliadis Spyros G. Adamopoulos Demetrios N. Nicolaides 《Journal of heterocyclic chemistry》2006,43(3):579-583
Bis‐amidoxime 1 reacts with phosgene, thiophosgene and thionylchloride to give the corresponding bisfused oxadiazolo‐ and oxathiadiazoloquinoxalines 2, 4, 5 along with the unexpected furazano‐derivative 3 , while monoamidoximes 9, 13 by treatment with ethyl chloroformate affords the oxadiazoloquinoxaline and the oxadiazolobenzothiazine derivatives 14, 15 along with the dicarboxylated product 16 . 相似文献
105.
106.
Demetrios N. Nicolaides Konstantinos E. Litinas Ioannis Vrasidas Konstantina C. Fylaktakidou 《Journal of heterocyclic chemistry》2004,41(4):499-503
The unexpected formation of 3‐aryl‐5‐arylamino‐1,2,4‐oxadiazoles took place, when arylamidoximes reacted thermally with ethoxycarbonylmethylene(triphenyl)phosphorane. Furoxans, nitriles, ureas were also isolated suggesting aryl cyanide oxides as intermediates. 3‐Aryl‐5‐arylamino‐1,2,4‐oxadiazoles were formed via an aryl migration from the carbon atom to the nitrogen atom of the amidoxime, and the structure was further proved from the X‐ray crystal structure of the N‐(4‐bromobenzoyl) derivative. 相似文献
107.
108.
Panayiotis C. Varras Panagiotis S. Gritzapis Konstantina C. Fylaktakidou 《Molecular physics》2018,116(2):154-170
In this work, we applied the multiconfigurational complete active space self-consistent field method and the multiconfigurational second-order perturbation theory CASMP2 to study the fundamental excited states of pyridine and its possible photophysical and photochemical transformations. Our calculations, which are in agreement with the experimental results corresponding to excitations around the 0–0 transition, showed that the very low experimentally observed fluorescence of pyridine is due to the presence of two almost isoenergetic crossings, one of triple character, S1/T1/S0 and the other of S1/S0 character. Both crossings are below the minimum of S1(nπ*) and have a common transition state (S1(TS)) with a very low energy barrier (1.85 kcal/mol or 0.08 eV at the CASMP2 level of theory) separating them. A third triple crossing of the type S1/T1/S0 lying lower with respect to the other two elucidates the observed T1→S0 radiationless transition. This explains not only pyridine's very low fluorescence and phosphorescence but also its almost negligible photochemistry, showing that photophysics is the prevalent process in this molecule. 相似文献
109.
The authors study the photodissociation reactions of pyrrole and N-methylpyrrole using first-principles molecular dynamics. The first excited state is described with restricted open-shell Kohn-Sham theory. They find a small barrier in the excited state potential energy surface. The possibility of energy redistribution near the Franck-Condon region leads to two different reaction channels in on-the-fly simulations on a single diabatic potential energy surface. The results are discussed in comparison with previous ab initio calculations and with experiments. 相似文献
110.
Historically,decay rates have been used to provide quantitative and qualitative information on the solutions to hyperbolic conservation laws.Quantitative results include the establishment of convergenc... 相似文献