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51.
El Sayed H. El Ashry Adel A.-H. Abdel-Rahman Mohamed Kattab Aida H. Shobier Richard R. Schmidt 《Journal of carbohydrate chemistry》2013,32(3):345-357
ABSTRACT Methyl 2,3,4-tri-O-acetyl-6-O-(p-tolylsulfonyl)-α-D-glucopyranoside (6), or its iodo analogue 7, were subjected to nucleophilic displacement with morpholine to give 8, deacetylation of which gave methyl 6-deoxy-6-(morpholin-4-yl)-α-D-glucopyranoside (3). Similarly, 11, 12 and 21 were prepared. The 6-deoxy-6-iodo derivative 16 was subjected to nucleophilic displacement with morpholine and subsequent acetylation to give 15. Deacetylation of 15 gave 17. The kinetic studies for the inhibition of β-D-glucosidase from sweet almond and using o-nitrophenyl β-D-glucopyranoside as substrate exhibited a K i value for 21 on the same order as 1-deoxynojirimycin whereas for 3, a K i value of lesser order was observed. 相似文献
52.
E. M. Keshk A. A. Abu-Hashem M. M. Girges A. H. Abdel-Rahman F. A. Badria 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1577-1593
Benzo[1,2-b:5,4-b′]difuran-2-carbohydrazides 5a, b were reacted with aryl or alkyl isothiocyanates to give the corresponding thiosemicarbazides 6a–h. Cyclization of the substituted thiosemicarbazides with sodium hydroxide led to the formation of benzo[1,2-b:5,4-b′]difuranyl-1,3,4-triazoles 7a–f. Desulfurization of thiosemicarbazides by mercuric oxide gave benzo[1,2-b:5,4-b′]difuranyl-1,3,4-oxadiazoles 8a–f. Treatment of thiosemicarbazides with ethyl bromoacetate or α-bromopropionic acid yielded benzo[1,2-b:5,4-b′]difuranyl-carbonyl-hydrazono-4-thiazolidinones 9a–f and 10a–f, respectively. Furthermore, the reaction of the thiosemicarbazides with phosphorus oxychloride gave benzo[1,2-b:5,4-b′]difuranyl-1,3,4-thiadiazoles 11a–f. Some compounds in this study were biologically evaluated for their ability to bind to DNA. 相似文献
53.
Mohammed F. Hamza Eric Guibal Adel A.-H. Abdel-Rahman Marwa Salem Mahmoud S. Khalafalla Yuezhou Wei Xiangbiao Yin 《Molecules (Basel, Switzerland)》2022,27(21)
The recovery of strategic metals such as rare earth elements (REEs) requires the development of new sorbents with high sorption capacities and selectivity. The bi-functionality of sorbents showed a remarkable capacity for the enhancement of binding properties. This work compares the sorption properties of magnetic chitosan (MC, prepared by dispersion of hydrothermally precipitated magnetite microparticles (synthesized through Fe(II)/Fe(III) precursors) into chitosan solution and crosslinking with glutaraldehyde) with those of the urea derivative (MC-UR) and its sulfonated derivative (MC-UR/S) for cerium (as an example of REEs). The sorbents were characterized by FTIR, TGA, elemental analysis, SEM-EDX, TEM, VSM, and titration. In a second step, the effect of pH (optimum at pH 5), the uptake kinetics (fitted by the pseudo-first-order rate equation), the sorption isotherms (modeled by the Langmuir equation) are investigated. The successive modifications of magnetic chitosan increases the maximum sorption capacity from 0.28 to 0.845 and 1.25 mmol Ce g−1 (MC, MC-UR, and MC-UR/S, respectively). The bi-functionalization strongly increases the selectivity of the sorbent for Ce(III) through multi-component equimolar solutions (especially at pH 4). The functionalization notably increases the stability at recycling (for at least 5 cycles), using 0.2 M HCl for the complete desorption of cerium from the loaded sorbent. The bi-functionalized sorbent was successfully tested for the recovery of cerium from pre-treated acidic leachates, recovered from low-grade cerium-bearing Egyptian ore. 相似文献
54.
Atomic force microscopes (AFM) are used to estimate material and surface properties. When using contact-mode AFM, the sample or the probe is excited near a natural frequency of the system to estimate the linear coefficient of the contact stiffness. Because higher modes offer lower thermal noise, higher quality factors, and higher sensitivity to stiff samples, their use in this procedure is more desirable. However, these modes are candidates for internal resonances, where the energy being fed into one mode may be channeled to another mode. Ignoring such interactions could distort or affect the accuracy of measurements. The method of multiple scales is used to derive an approximate analytical expression to the probe response in the presence of two-to-one autoparametric resonance between the second and third modes. We examine characteristics of this solution in relation to a single-mode response and consider its implications in AFM measurements. We find that the influence of this interaction extends over a considerable range of the tip-sample contact stiffness. 相似文献
55.
A. -M. M. Abdel-Rahman 《International Journal of Theoretical Physics》1994,33(3):735-744
We derive a complete set of new exactk = 0, ±1 radiation solutions of Barker's homogeneous isotropic cosmologies. In the very early universe they reduce to the asymptotic solutions of Yepes and Dominguez-Tenreiro. Consistency with the standard cosmological model constrains the solution's free parameters. 相似文献
56.
Ahmed Hameurlaine Wael A. El-Sayed Adel A.-H. Abdel-Rahman 《Monatshefte für Chemie / Chemical Monthly》2008,18(4):1507-1511
A series of peptide and dipeptide derivatives conjugated with a tryptophane residue were synthesized. The prepared compounds
were tested for antimicrobial activity against four different bacterial species displaying different degrees of antibacterial
activities or inhibitory actions. 相似文献
57.
Summary.
d-Mannose was treated with dry acetone in the presence of conc. H2SO4 to afford 2,3:5,6-di-O-isopropylidene-α-d-mannofuranoside. Treating the latter with ethyl chloroacetate gave carboethoxymethyl 2,3:5,6-di-O-isopropylidene-α-d-mannofuranoside, which was hydrolyzed with N2H4 · H2O to afford the acid hydrazide derivative. Treating of the acid hydrazide with acylated amino acides, via the azide-coupling method afforded the corresponding O-glycopeptides. Reaction of the glycopeptide methyl esters with N2H4 · H2O afforded the corresponding hydrazides, which were coupled with the amino acid methyl esters to afford the dipeptides. Deprotection
was carried out by using 70% AcOH. The prepared O-glycopeptides were tested for antiviral activity against hepatitis B virus and showed moderate activities. 相似文献
58.
El-Kady Dina S. Abd Rabou Ahmed A. Tantawy Mohamed A. Abdel-Rahman Adel A.-H. Abdel-Megeed Amira A.-S. AbdElhalim Mervat M. Elmegeed Gamal A. 《Applied biochemistry and biotechnology》2019,188(3):635-662
Applied Biochemistry and Biotechnology - Modification of steroid molecules by introducing heterocyclic ring into the core structure of steroids has been utilized as an attractive approach for... 相似文献
59.
Ayman M. Atta Adel A.-H. Abdel-Rahman Nora A. Hamad 《Journal of Dispersion Science and Technology》2013,34(9):1222-1232
Water soluble nonionic surfactants based on Schiff base monomers were prepared by their etherification with β,` β- dichlorodiethylether and PEG 400 in presence of NaOH. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The prepared nonionic surfactants were evaluated as demulsifiers for synthetic water in crude-oil emulsions that were pronounced at different ratios of crude oil: water at 45°C and 60°C. The experimental results showed that the dehydration rate of the prepared demulsifiers reached 90% and 100% at some concentrations. 相似文献
60.
Abdel-Rahman?Farghaly Hussein?El-KashefEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(2):217-227
Summary. The synthesis of the title compounds was achieved using 1-phenyl-5-(pyrrol-1-yl)-1H-pyrazole-3-carboxylic acid azide as starting material. The latter compound was allowed to react with alcohols and amines to afford the corresponding carbamates and urea derivatives. Alkaline hydrolysis of the carbamates gave the corresponding amine, which was acylated and/or aroylated to give amide derivatives. These and the urea derivatives were subjected to cyclodehydration to give the title compounds. Antibacterial and antifungal activities were observed for several derivatives. 相似文献