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51.
Subas M. Sakya Andrew C. Flick Jotham W. Coe David L. Gray Sidney Liang Fabiola Ferri Michel Van Den Berg Kees Pouwer 《Tetrahedron letters》2012,53(7):723-725
Two syntheses of versatile intermediate azepinones 2 and 3 are described. A 6-step intramolecular Dieckmann cyclization and decarboxylation led to the intermediate 3 while an alternate 4-step synthesis of 2 was developed and used for scale-up. The highlight of the second synthesis is the one-step per-bromination/elimination protocol from readily available azepinone 13a to provide a versatile scaffold in vinyl bromide 5, which enables SAR around the aryl moiety. An example of the elaboration of the intermediate 2 toward a heteroaryl azepinone is also described. 相似文献
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54.
Placido Mineo Fabiola Spitaleri Emilio Scamporrino 《Journal of polymer science. Part A, Polymer chemistry》2013,51(6):1428-1435
Cyclic tetra{5,15‐di‐[p(ω‐methoxypolyethyleneoxy)phenyl]‐10,20‐[p‐oxyphenyl] methylen porphyrin}, cy‐[O‐(H2‐PTPEG2)‐O‐CH2‐]4 , a water soluble macromolecule consisting of four porphyrin units [each with two long ω‐methoxypolyethyleneoxy (PEG) branches bound on its peripheral positions] linked by means of four methylenoxy bridges, was prepared by an interfacial etherification reaction. Structural and spectroscopic characterization of cy‐[O‐(H2‐PTPEG2)‐O‐CH2‐]4 and of its cobalt‐derivative {cy‐[O‐(Co‐PTPEG2)‐O‐CH2‐]4} was performed by means of MALDI‐TOF mass spectrometry, NMR, UV–vis, and circular dichroism spectroscopy. The data obtained from the cy‐[O‐(Co‐PTPEG2)‐O‐CH2‐]4/Gramicidin‐S mixture showed that some evident spectral changes were compatible with the formation of a supramolecular structure between the porphyrinic nanobox and the Gramicidin S (a polypeptide having a relevant pharmacological importance). These preliminary data highlight how cy‐[O‐(H2‐PTPEG2)‐O‐CH2‐]4 and/or its metalled derivatives, for their both chemical composition and structural arrangement, have promising properties for applications as a drug carrier in aqueous media. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
55.
Ursula Fabiola Rodríguez-Zúñiga Victor Bertucci Neto Sonia Couri Silvio Crestana Cristiane Sanchez Farinas 《Applied biochemistry and biotechnology》2014,172(5):2348-2362
The enzymatic cocktail of cellulases is one of the most costly inputs affecting the economic viability of the biochemical route for biomass conversion into biofuels and other chemicals. Here, the influence of liquid hot water, dilute acid, alkali, and combined acid/alkali pretreatments on sugarcane bagasse (SCB) used for cellulase production was investigated by means of spectroscopic and imaging techniques. Chemical composition and structural characteristics, such as crystallinity (determined by X-ray diffraction), functional groups (Fourier transform infrared spectroscopy), and microstructure (scanning electron microscopy), were used to correlate SCB pretreatments with enzymatic biosynthesis by a strain of the filamentous fungus Aspergillus niger under solid-state fermentation. The combined acid/alkali pretreatment resulted in a SCB with higher cellulose content (86.7 %). However, the high crystallinity (74 %) of the resulting biomass was detrimental to microbial uptake and enzyme production. SCB pretreated with liquid hot water yielded the highest filter paper cellulase (FPase), carboxymethyl cellulase (CMCase), and xylanase activities (0.4, 14.9, and 26.1 U g?1, respectively). The results showed that a suitable pretreatment for SCB to be used as a substrate for cellulase production should avoid severe conditions in order to preserve amorphous cellulose and to enhance the physical properties that assist microbial access. 相似文献
56.
Botta B Fraschetti C D'Acquarica I Sacco F Mattay J Letzel MC Speranza M 《Organic & biomolecular chemistry》2011,9(6):1717-1719
The gas-phase encounters between 2-aminobutane and proton-bound chiral resorcin[4]arene/nucleoside complexes behave in the gas phase as supramolecular "chiroselective logic gates" by releasing the nucleoside depending on the resorcin[4]arene and the 2-aminobutane configurations. 相似文献
57.
Jacobo-Salcedo Mdel R Alonso-Castro AJ Salazar-Olivo LA Carranza-Alvarez C González-Espíndola LA Domínguez F Maciel-Torres SP García-Lujan C González-Martínez Mdel R Gómez-Sánchez M Estrada-Castillón E Zapata-Bustos R Medellin-Milán P García-Carrancá A 《Natural product communications》2011,6(12):1925-1928
The antimicrobial effects of the Mexican medicinal plants Guazuma ulmifolia, Justicia spicigera, Opuntia joconostle, O. leucotricha, Parkinsonia aculeata, Phoradendron longifolium, P. serotinum, Psittacanthus calyculatus, Tecoma stans and Teucrium cubense were tested against several human multi-drug resistant pathogens, including three Gram (+) and five Gram (-) bacterial species and three fungal species using the disk-diffusion assay. The cytotoxicity of plant extracts on human cancer cell lines and human normal non-cancerous cells was also evaluated using the MTT assay. Phoradendron longifolium, Teucrium cubense, Opuntia joconostle, Tecoma stans and Guazuma ulmifolia showed potent antimicrobial effects against at least one multidrug-resistant microorganism (inhibition zone > 15 mm). Only Justicia spicigera and Phoradendron serotinum extracts exerted active cytotoxic effects on human breast cancer cells (IC50 < or = 30 microg/mL). The results showed that Guazuma ulmifolia produced potent antimicrobial effects against Candida albicans and Acinetobacter lwoffii, whereas Justicia spicigera and Phoradendron serotinum exerted the highest toxic effects on MCF-7 and HeLa, respectively, which are human cancer cell lines. These three plant species may be important sources of antimicrobial and cytotoxic agents. 相似文献
58.
Julia Jeanett Segura-Uribe Eunice Dalet Farfán-García Christian Guerra-Araiza Fabiola Jimena Ciprés-Flores Paola García-dela Torre 《光谱学快报》2013,46(7):356-366
The analysis of different central nervous system regions is interesting and necessary as each one is involved in specific physiological processes and pathologies. On that matter, differences in the chemical composition between the same brain regions in different mice strains have been reported. In this sense, the development of a simple method for the identification of these regions depending on their chemical composition becomes relevant. Raman microspectroscopy, a non-destructive analytical chemical approach for biological samples, is a widely used method for qualitative, quantitative, and structural analysis in biochemical research. Ten brain structures in three different mice strains (Triple transgenic for Alzheimer Disease, 3xTgAD; Cluster 57 black 6, C57BL/6; and the Swiss strain, CD1) were analyzed, and variations among samples from several brain regions were found. Particularly, the pattern of signals from the hippocampus, the prefrontal and temporal cortices, the basal forebrain, the striatum, the cerebellum, and the hypothalamus was discernable. Interestingly, notable signals regarding non-peptide small neurotransmitters were observed, including those related to acetylcholine. These bands were present in the Raman spectra of the basal forebrain and prefrontal cortex in the three mice strains, consistent with the relative abundance of this neurotransmitter in those regions. However, signals with lower intensities appeared in the basal forebrain of C57BL/6 in comparison with the same tissue of the other two strains. In addition, the Raman intensity of bands assigned to catecholamines in the striatum was lower in the 3xTgAD than those from both CD1 and C57BL/6 mice strains. This approach, as well as the reported differences, has potential application for designing analysis on specific murine models of brain diseases. 相似文献
59.
Fabiola S. Ottoboni Gaël Poirier Fábia C. Cassanjes Younes Messaddeq Sidney J.L. Ribeiro 《Journal of Non》2009,355(45-47):2279-2284
Vitreous samples were prepared in the binary system NaPO3–MoO3 and their characteristic temperatures were determined by Differential Scanning Calorimetry. Glasses with high amounts of MoO3 (>45 mol%) exhibit an intense crystallization peak and the composition 50 NaPO3–50 MoO3 was chosen for the crystallization study. Two different methods based on thermal analyzes were used to determine the mechanism of crystallization in these molybdenum–phosphate glasses. In the first procedure, thermal analyses by DTA were performed on samples with different grain sizes and the crystallization tendency deduced in function of superficial area. The second method used the classical non-isothermal crystallization study: DSC measurements were performed under several heating rates to access activation energy for crystallization and Avrami parameter n. Critical cooling rate was calculated and compared with experimental data obtained from DTA analysis upon cooling. 相似文献
60.
It is well known that many nonlinear phenomena such as bifurcations and chaotic behavior occur in DC–DC converters mainly due to the switching action among all the different topologies of the circuit. Such behavior has been described with detail numerically, and also mathematical reasoning has been provided. In this paper we focuss on the experimental side of a DC–DC Buck converter controlled with two different strategies: classical Pulse Width Modulation (PWM) with a ramp and a more recently described Zero Average Dynamics (ZAD). We show some nonsmooth events and we explain with detail the experimental set-ups. In one of them, we use a FPGA card to obtain on-line results. In the other we use Virtual Instrumentation to generate an experimental two-dimensional bifurcation diagram, which will be compared to the numerical data. After the data acquisition of the system state variables some elaborated post-processing must be made. This is done through LabView. Although the main application of these results is centered in avoiding non-periodic or high-amplitude periodic behavior, they can also be applied to reducing the generated electro-magnetic interference and to the information transmission.Partially funded by SICONOS. 相似文献