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Jesús Ibarz M Ferreira V Hernández-Orte P Loscos N Cacho J 《Journal of chromatography. A》2006,1116(1-2):217-229
A procedure has been developed for the GC-MS analysis of the aromas released in fast acid hydrolysis of precursor fractions from grape musts and skins. Different sorbents for the extraction of the precursors were compared. The best results were obtained with LiChrolut EN polymeric resins which displayed two and six-fold more extraction capacity than Amberlite XAD-2 resins and C18 sorbents, respectively. C18 sorbents are more suitable for selective extraction of less polar precursors. The initial version of the method was imprecise and so the imprecision of the different steps was assessed. The maceration of the solid parts and the liquid-liquid extraction of the aromas released in the acid hydrolysis proved to be the critical steps. Greater crushing of the solid parts and solid-phase extraction (SPE) instead of liquid-liquid extraction (LLE) improved reproducibility. In the method finally proposed about 100 aromatic components belonging to four large groups (lipid derivatives, shikimic acid derivatives, norisoprenoids and terpenes) were determined with good reproducibility. Important aroma compounds, such as cis-rose oxide or wine lactone were detected in non-Muscat grapes. 相似文献
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Marijke WA de Backer Carlos P Fitzsimons Maike AD Brans Mieneke CM Luijendijk Keith M Garner Erno Vreugdenhil Roger AH Adan 《BMC neuroscience》2010,11(1):81
Background
This study compared the transduction efficiencies of an adeno-associated viral (AAV) vector, which was pseudotyped with an AAV1 capsid and encoded the green fluorescent protein (GFP), with a lentiviral (LV) vector, which was pseudotyped with a VSV-G envelop and encoded the discosoma red fluorescent protein (dsRed), to investigate which viral vector transduced the lateral hypothalamus or the amygdala more efficiently. The LV-dsRed and AAV1-GFP vector were mixed and injected into the lateral hypothalamus or into the amygdala of adult rats. The titers that were injected were 1 × 108 or 1 × 109 genomic copies of AAV1-GFP and 1 × 105 transducing units of LV-dsRed. 相似文献56.
Natalia Campillo Juan Ignacio Cacho Javier Marín Pilar Viñas Manuel Hernández-Córdoba 《Mikrochimica acta》2014,181(1-2):97-104
We describe a simple method for the simultaneous determination of organolead and organomanganese compounds in seawater samples. It is based on ultrasound-assisted emulsification microextraction. Trimethyllead, triethyllead, tetraethyllead, cyclopentadienylmanganese tricarbonyl and its methyl derivative were separated and determined using gas chromatography and mass spectrometry. Trimethyllead and triethyllead were derivatized with sodium tetraphenylborate before being submitted to the preconcentration step. Detection limits ranged from 7.0 to 41 ng L?1 depending on the compound. Recoveries ranged from 84 to 118 %, depending on the compound and the sample analyzed. Seawater samples were collected at different sites of the Cartagena Bay and none of the target analytes were found at levels above the corresponding detection limits. Figure
The most relevant organomanganese and organolead compounds can be monitorized in seawaters by using a relatively simple instrumentation (Gas chromatography–mass spectrometry). Advantage is taken of ultrasound-assisted emulsification microextraction that involves minimal amounts of organic solvents 相似文献
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Martin J. Duffy Orla Kelly Christopher R. Calvert Raymond B. King Louise Belshaw Thomas J. Kelly John T. Costello David J. Timson William A. Bryan Thomas Kierspel I. C. Edmond Turcu Cephise M. Cacho Emma Springate Ian D. Williams Jason B. Greenwood 《Journal of the American Society for Mass Spectrometry》2013,24(9):1366-1375
High power femtosecond laser pulses have unique properties that could lead to their application as ionization or activation sources in mass spectrometry. By concentrating many photons into pulse lengths approaching the timescales associated with atomic motion, very strong electric field strengths are generated, which can efficiently ionize and fragment molecules without the need for resonant absorption. However, the complex interaction between these pulses and biomolecular species is not well understood. To address this issue, we have studied the interaction of intense, femtosecond pulses with a number of amino acids and small peptides. Unlike previous studies, we have used neutral forms of these molecular targets, which allowed us to investigate dissociation of radical cations without the spectra being complicated by the action of mobile protons. We found fragmentation was dominated by fast, radical-initiated dissociation close to the charge site generated by the initial ionization or from subsequent ultrafast migration of this charge. Fragments with lower yields, which are useful for structural determinations, were also observed and attributed to radical migration caused by hydrogen atom transfer within the molecule. Figure
? 相似文献
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A new method for analysing 3-isopropyl-2-methoxypyrazine, 3-sec-butyl-2-methoxypyrazine and 3-isobutyl-2-methoxypyrazine in wine has been developed and applied to wine. The analytes are extracted from 25 mL of wine in a solid-phase extraction cartridge filled with 60 mg of cation-exchange mixed-mode sorbent. Analytes are recovered with triethylamine in dichloromethane and the organic extract is analysed by GC-SIM-MS using 3-isopropyl-2-ethoxypyrazine as internal standard. The detection limits of the method are in all cases under 1 ng/L, below the olfactory thresholds of the compounds in wine. The repeatability of the method is around 15% for levels in wine of 2 ng/L. Linearity is satisfactory and recoveries are in all cases close to 100% with RSD between 13% and 20%. The method has been applied to the analysis of 12 Chilean white and 8 Spanish red wines. The levels found suggest that 3-alkyl-2-methoxypyrazines can exert a significant sensory contribution to the aroma of Chilean Sauvignon Blanc wines, while most likely they play a nearly negligible role on traditional Ribera and Rioja Spanish red wines. 相似文献
59.
The screening of five common metallochromic indicators used in the complexometric determination of Ca was studied using tristimulus chromaticity theory. Calcon-tartrazine-Orange II (6.8 + 1 + 4.6, w/w), thymolphthalein complexone-Orange II-tartrazine (14.22 + 1.22 + 1), Arsenazo III-Remazol Brilliant Blue-tartrazine (25.2 + 8.9 + 1), phthalein complexone-tartrazine-Remazol Brilliant Blue (2.47 + 1 + 1.1), and methylthymol Blue-Orange II-tartrazine (13 + 2.9 + 1) are proposed for the titration of calcium against Na2 EDTA. The clarity and accuracy of titration are improved. 相似文献
60.
The color transitions produced by certain metallochromic indicators used in the complexometric determination of Ba (with EDTA) were studied using tristimulus chromaticity theory. Metalphthalein, thymolphthalein complexone, methylthymol blue, antipyryl-o-arsenazo I, and antipyryl-p-arsenazo I were the indicators studied. The results obtained indicate that, of the indicators considered here, the most suitable for visual titration of Ba with EDTA are metalphthalein and thymolphthalein complexone. 相似文献