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31.
Andrey S. Sigachev Angelina N. Kravchenko Galina A. Gazieva Pavel A. Belyakov Natal'Ya G. Kolotyrkina Oleg V. Lebedev Nina N. Makhova Konstantin A. Lyssenko 《Journal of heterocyclic chemistry》2006,43(5):1295-1302
32.
Yuriy N. Malyar Natalia Yu. Vasilyeva Aleksandr S. Kazachenko Valentina S. Borovkova Andrei M. Skripnikov Angelina V. Miroshnikova Dmitriy V. Zimonin Vladislav A. Ionin Anna S. Kazachenko Noureddine Issaoui 《Molecules (Basel, Switzerland)》2021,26(17)
The process of sulfation of arabinogalactan—a natural polysaccharide from Larix sibirica Ledeb.—with sulfamic acid in 1,4-dioxane using different activators has been studied for the first time. The dynamics of the molecular weight of sulfated arabinogalactan upon variation in the temperature and time of sulfation of arabinogalactan with sulfamic acid in 1,4-dioxane has been investigated. It has been found that, as the sulfation time increases from 10 to 90 min, the molecular weights of the reaction products grow due to the introduction of sulfate groups without significant destruction of the initial polymer and sulfation products. Sulfation at 95 °C for 20 min yields the products with a higher molecular weight than in the case of sulfation at 85 °C, which is related to an increase in the sulfation rate; however, during the further process occurring under these conditions, sulfation is accompanied by the destruction and the molecular weight of the sulfated polymer decreases. The numerical optimization of arabinogalactan sulfation process has been performed. It has been shown that the optimal parameters for obtaining a product with a high sulfur content are a sulfamic acid amount of 20 mmol per 1 g of arabinogalactan, a process temperature of 85 °C, and a process time of 2.5 h. 相似文献
33.
Dmitry B. Vinogradov Alexei N. Izmest'ev Angelina N. Kravchenko Natalya G. Kolotyrkina Galina A. Gazieva 《Journal of heterocyclic chemistry》2024,61(1):137-145
A method for the regioselective synthesis of imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazine derivatives has been developed by the reaction of imidazotriazinethiones with ethyl phenylpropiolate upon treatment with potassium carbonate or sodium methoxide in methanol. The synthesis was accomplished by Michael-type addition of the imidazotriazinethiones to the triple bond of ethyl phenylpropiolate followed by subsequent intramolecular cyclization. 相似文献
34.
Owing to the increasing number of erythropoietin biosimilars being approved, the comparison of different erythropoietin preparations
in the pharmaceutical area is gaining in importance. Erythropoietin has a distinct natural heterogeneity arising from its
glycosylation, which shows strong composition variations. This heterogeneity increases the complexity of the analysis of erythropoietin
considerably, but may also be used to distinguish different preparations. Here, a method is presented for the differentiation
of various erythropoietin preparations by capillary electrophoresis–mass spectrometry and the subsequent application of multivariate
statistics. Relative peak areas of selected intact erythropoietin isoforms were used as variables in principal component analysis
and hierarchical agglomerative clustering. Both of these strategies were suited for the clear differentiation of all erythropoietin
preparations, including marketed products and preproduction preparations, which differ in the manufacturer, the production
cell line, and the batch number. By this means, even closely related preparations were distinguished on the basis of the combined
information on the antennarity, the sialoform, and the acetylation of the observed isoforms. 相似文献
35.
Angelina Sarapulova Daria Mikhailova Ljubomira Ana Schmitt Steffen Oswald Natalia Bramnik Helmut Ehrenberg 《Journal of Sol-Gel Science and Technology》2012,62(1):98-110
LiCoPO4-coated disordered carbon nanofibers (CNFs/LiCoPO4) were obtained by a sol–gel method, using triethyl phosphite or triethyl phosphate as the phosphorous source. The crystal
structure of the products was analyzed by X-ray powder diffraction, while morphology was studied using scanning electron microscopy,
transmission electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. Optimal synthesis conditions
for the CNFs/LiCoPO4 in light of the best electrochemical performance are discussed. The best discharge capacity 105 mAh/g (or ca. 63% of the
theoretical capacity) shows the material with 40% CNFs/LiCoPO4 and addition coating by carbon black. This composition has a best purity of active materials and point coverage of CNFs.
The X-ray photoelectron C1s spectra of the CNFs surface without and with sputter erosion show enhancement of C–O bonds at
the fiber surface, which does not influence significantly electrochemical behavior of the composite materials. 相似文献
36.
Valentina S. Borovkova Yuriy N. Malyar Irina G. Sudakova Anna I. Chudina Andrey M. Skripnikov Olga Yu. Fetisova Alexander S. Kazachenko Angelina V. Miroshnikova Dmitriy V. Zimonin Vladislav A. Ionin Anastasia A. Seliverstova Ekaterina D. Samoylova Noureddine Issaoui 《Molecules (Basel, Switzerland)》2022,27(1)
Spruce (Picea abies) wood hemicelluloses have been obtained by the noncatalytic and catalytic oxidative delignification in the acetic acid-water-hydrogen peroxide medium in a processing time of 3–4 h and temperatures of 90–100 °C. In the catalytic process, the H2SO4, MnSO4, TiO2, and (NH4)6Mo7O24 catalysts have been used. A polysaccharide yield of up to 11.7 wt% has been found. The hemicellulose composition and structure have been studied by a complex of physicochemical methods, including gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The galactose:mannose:glucose:arabinose:xylose monomeric units in a ratio of 5:3:2:1:1 have been identified in the hemicelluloses by gas chromatography. Using gel permeation chromatography, the weight average molar mass Mw of hemicelluloses has been found to attain 47,654 g/mol in noncatalytic delignification and up to 42,793 g/mol in catalytic delignification. Based on the same technique, a method for determining the α and k parameters of the Mark–Kuhn–Houwink equation for hemicelluloses has been developed; it has been established that these parameters change between 0.33–1.01 and 1.57–472.17, respectively, depending on the catalyst concentration and process temperature and time. Moreover, the FTIR spectra of the hemicellulose samples contain all the bands characteristic of heteropolysaccharides, specifically, 1069 cm−1 (C–O–C and C–O–H), 1738 cm−1 (ester C=O), 1375 cm−1 (–C–CH3), 1243 cm−1 (–C–O–), etc. It has been determined by the thermogravimetric analysis that the hemicelluloses isolated from spruce wood are resistant to heating to temperatures of up to ~100 °C and, upon further heating, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses has been examined using the compounds simulating the 2,2-diphenyl-2-picrylhydrazyl free radicals. 相似文献
37.
Guillermo Durán-Solares Walter Fugarolas-Gómez Naytzé Ortíz-Pastrana Horacio López-Sandoval Tayde Osvaldo Villaseñor-Granados Angelina Flores-Parra 《Journal of Coordination Chemistry》2018,71(11-13):1935-1958
AbstractSpectroscopic and single crystal X-ray diffraction studies of coordination compounds of CoII, NiII, ZnII, and PdII with phenylsulfonyl imidazole and benzimidazole derivatives (2-mfsiz, 2-mfsbz) were performed. The relevance of non-covalent interactions on the stabilization of intra and intermolecular arrangements in the ligands and their coordination compounds was investigated. The imidazole 2-mfsiz ligand presents two enantiomeric conformers, where the ethylphenylsulfone moiety stabilizes intermolecular lone pair···π (S–O···π(phe)) and H···π contacts, while its tetrahedral coordination compounds, [M(2-mfsiz)2X2] (M2+?=?Co, Ni, Zn; X?=?Cl, Br) showed intramolecular lone pair···π interactions (S–O···π(iz)). On the other hand, compounds [Cu2(2-mfsiz)2(µ2-AcO)4] and trans-[Pd(2-mfsiz)2Cl2] do not present lone pair···π interactions due to the metal ion geometry (square base pyramidal or square planar), which leads to formation of π(iz)···π(phe) interactions. For the benzimidazole ligand 2-mfsbz, an intramolecular, H(phe)···π(bz) contact was observed, remaining in its tetrahedral and octahedral coordination compounds, [M(2-mfsbz)2X2] (M2+?=?Co, Zn; X?=?Cl, Br, NO3). This interaction limits the free rotation of the ethylphenylsulfone moiety for stabilization of an intermolecular lone pair···π interaction (S–O···π(iz)). The dimeric [Zn2(2-mfsiz)2(µ2-AcO)4] compound has a π(bz)···π(phe) contact. Theoretical calculations confirmed the non-covalent interactions in the ligands and their coordination compounds. 相似文献
38.
Angelina Kantola Hugo O. Villar Gilda H. Loew 《Journal of computational chemistry》1991,12(6):681-689
An atomic parametrization for the determination of a hydrophobicity index that depends on the molecular conformation is presented. The hydrophobicity parameter was calculated in four alternative ways based on charge densities and atomic contributions to the total molecular surface area and depending on the approach, the molecular dipole moment. The geometries required for the computations were calculated using quantum mechanical semiempirical methods as well as molecular mechanics. The charges were computed using semiempirical methods as well as the Gasteiger method. 相似文献
39.
Jairo Quiroga Angelina Hormaza Braulio Insuasty Manuel Mrquez 《Journal of heterocyclic chemistry》1998,35(2):409-412
A series of dihydropyrazolo[3,4-b]pyridin-6-ones 3 was prepared by cyclization of 5-amino-1-aryl-3-methylpyrazoles 1 and Meldrum's acid benzylidene derivatives 2 in nitrobenzene. The structure of 4,5-dihydropyrazolo[3,4-b]pyridin-6-ones and reaction orientation were determined by nmr measurements. 相似文献