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31.
Colomba Di Blasi Carmen Branca Antonio Galgano 《Polymer Degradation and Stability》2008,93(2):335-346
The decomposition of fir wood, impregnated with diammonium sulfate and diammonium phosphate, has been investigated with a laboratory scale reactor together with gas-chromatographic analysis of gas and condensable organics. The dependence of products and other process variables on the salt concentration in the wood (from 0 to about 20% on a dry wood basis) and the heating temperature (650-900 K) is qualitatively similar for the two cases. Given heating temperatures of about 650-750 K and using as a reference water-extracted wood, diammonium sulfate and diammonium phosphate concentrations of about 1% are apt to cause a small increase (factors of 1.2-2) in the yields of levoglucosan, 5-methyl-2-furaldehyde and 2-acetylfuran, whereas values in the range 2-5% highly augment the yields of levoglucosenone and 2-furaldehyde (factors of 14-16 and 3-2, respectively). Salt concentrations above 10% confer excellent fire retardance properties of wood with total yields of water and char up to about 70 and 85% and ratio values of non-combustible to combustible volatile products up to 3.5 and 6.5, respectively. The displacement of the reaction process at lower temperatures, the higher exothermicity associated with the enhanced char formation, the reduced convective cooling and the endothermicity of salt decomposition also highly affect the conversion times and the overall rates of volatile species release. 相似文献
32.
将具有封闭空心结构的酚醛微球(HPMs)引入到聚丙烯/膨胀阻燃剂(PP/IFR)体系,燃烧时一方面依托PP/IFR形成膨胀多孔炭,另一方面通过HPMs形成空心炭微球,嵌入到前面多孔炭的骨架中,形成具有多层次孔的炭结构,从而调控膨胀炭层,进而调节材料的阻燃性能.通过极限氧指数(LOI)、垂直燃烧(UL-94)等研究了材料的阻燃性能;通过热失重分析(TGA)测试其热稳定性;采用红外热成像仪监测燃烧过程材料的表面温度,用扫描电镜(SEM)观察IFR、HPMs在基体中的分散行为及炭层结构.结果表明,少量HPMs在聚合物中分散得比较均匀.HPMs调控了膨胀炭层,使PP/IFR形成了表层炭致密,内层具有多层次孔的炭结构.这种优质的炭结构可以使样品表面温度迅速降低,从而有效提高PP/IFR体系的阻燃效率,使得PP在添加18 wt%IFR和1 wt%HPMs就可以通过UL-94 V0级别. 相似文献
33.
Lucia Sanchez-Prado Konstantina Kalafata Sanja Risticevic Janusz Pawliszyn Marta Lores Maria Llompart Nicolas Kalogerakis Elefteria Psillakis 《Analytica chimica acta》2012
Here, we report for the first time a laboratory investigation into the photochemical degradation of 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100) in ice solid samples using an artificial UV light source. Solid phase microextraction (SPME) was used as a sensitive extraction technique for monitoring trace amounts of the hydrophobic pollutant and its photoproducts. The results showed that ice photolysis kinetics for BDE-100 is similar to the one observed in the aqueous counterpart. The eight photoproducts identified consisted of brominated diphenyl ethers with lower bromine content and polybrominated dibenzofurans, suggesting two important photodegradation pathways for BDE-100 in ice solid samples: (i) stepwise reductive debromination and (ii) intramolecular elimination of HBr. Similarities in photochemical product arrays observed in the ice and water photolysis of BDE-100 were attributed to a similar mechanism for photochemical decomposition for both phases. Possible involvement of the water molecules in the reactions has been excluded by performing photolysis in D2O ice solid and water samples. Taking advantage of the high preconcentration factor obtained with SPME at low temperatures, a SPME fiber cooled with liquid carbon dioxide down to 0 °C was used as a photoreaction support for BDE-100 allowing the identification of a greater number of photoproducts. 相似文献
34.
Kasim Sakran Abass 《光谱学快报》2013,46(4):265-273
Organophosphate inhibits carboxylesterase thus regular treatment includes carboxylesterase oxime reactivator in combination with anti-muscarinic agents. In order to progress the understanding of species differences and to enable an additional reliable extrapolation of animal result to quail a study was initiated to inspect the effect of insecticide compounds, that is, mevinphos, ethoprop, and fenthion, with quail-serum carboxylesterase and common chicken-carboxylesterase. The rate constants for the inhibition of carboxylesterase by these organophosphate and for the aging and spontaneous reactivation of organophosphate-inhibited carboxylesterase enzyme as well as for the oxime-induced reactivation of organophosphate-inhibited carboxylesterase enzyme by the oximes trimedoxime, methoxime, N,N′-(ethano)bis(4-hydroxyiminomethyl)pyridinium methanosulphonate, HI-6, and HLö-7 were determined in this study. Compared to quail-serum carboxylesterase and chick-carboxylesterase displayed a lower sensitivity toward the inspected organophosphate. Furthermore, a slower aging and spontaneous reactivation of quail-serum carboxylesterase enzyme was recorded. The potency of the detected oxime reactivator was remarkably lower with organophosphate-inhibited quail-serum carboxylesterase. 相似文献
35.
《Arabian Journal of Chemistry》2022,15(11):104262
This review critically evaluates the plastic accumulation challenges and their environmental (primarily) and human (secondarily) impacts. It also emphasizes on their degradation and fragmentation phenomena under marine conditions. In addition, it takes into account the leachability of the various chemical substances (additives) embedded in plastic products to improve their polymeric properties and extend their life. Regardless of their effectiveness in enhancing the polymeric function of plastic products, these additives can potentially contaminate air, soil, food, and water. Several findings have shown that, regardless of their types and sizes, plastics can be degraded and/or fragmented under marine conditions. Therefore, the estimation of fragmentation and degradation rates via a reliable developed model is required to better understand the marine environmental status. The main parameter, which is responsible for initiating the fragmentation of plastics, is sunlight/UV radiation. Yet, UV- radiation alone is not enough to fragment some plastic polymer types under marine conditions, additional factors are needed such as mechanical abrasion. It should be also mentioned that most current studies on plastic degradation and fragmentation centered on the primary stages of degradation. Thus, further studies are needed to better understand these phenomena and to identify their fate and environmental effects. 相似文献
36.
Carro AM Lorenzo RA Fernández F Phan-Tan-Luu R Cela R 《Analytical and bioanalytical chemistry》2007,388(5-6):1021-1029
This paper describes the first validated method for the extraction, purification and determination of trace levels of a number
of pollutants of growing concern, including polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs), in
aquaculture feeds and products. The new procedure comprises microwave-assisted extraction (MAE; optimized, using a central
composite experimental design, to 15 min at 85 °C in 14 mL of 1:1 hexane/dichloromethane), and concentration by headspace
solid-phase microextraction (HSSPME), and separation/quantification by gas chromatography with mass spectrometry detection
(GC-MS/MS). The method was validated on the reference materials IAEA-406 and WMF-01. Limits of detection for fourteen of the
fifteen analytes considered range from 10 to 600 pg g−1, and limits of quantification from 50 pg g−1 to 1.9 ng g−1. Linear ranges, accuracies and precisions are reported. 相似文献
37.
In this work, the suitability of the microporous membrane liquid–liquid extraction (MMLLE) technique for the concentration of several organophosphate esters (OPs) in water samples is assessed. Analytes were first extracted into a few microlitres of an organic solvent, immobilized in the pores of a hollow polypropylene membrane, and then determined by gas chromatography with nitrogen–phosphorus detection (GC–NPD). Main parameters controlling the efficiency of the extraction step were identified and their effects on the performance of the technique discussed. Under final working conditions, 2 cm long polypropylene membranes, containing about 7 μL of octanol in the pores, were dipped in a glass vial filled with 115 mL of water with a 30% of sodium chloride. Extractions were carried out for 12 h, at room temperature, under magnetic stirring. After that, analytes were recovered from the membrane with 0.2 mL of ethyl acetate. This extract was mixed with the internal standard (50 μL of a tripentyl phosphate solution in the same solvent) and finally reduced to ca. 50 μL. Overall enrichment factors for the optimized method ranged from 35 to 1400 times, and the achieved limits of quantification from 0.008 to 0.12 ng mL−1, depending on the considered compound. Globally, the method showed an acceptable linearity and precision for all species, except for tris(2-ethylhexyl) phosphate (TEHP). Performance of the MMLLE approach is compared with that reported for other solid- and liquid-phase microextraction techniques and its suitability for the analysis of real water samples discussed. 相似文献
38.
Solà Vázquez A Martín A Costa-Fernandez JM Ruiz Encinar J Bordel N Pereiro R Sanz-Medel A 《Analytical and bioanalytical chemistry》2007,389(3):683-690
There is an increasing concern regarding the toxicity and environmental distribution and impact of brominated organic compounds
employed as flame retardants. Thus, present interest in searching for new analytical techniques and methods allowing a rapid,
simple and reliable detection of those compounds in materials and wastes potentially containing such flame retardants is not
surprising. The feasibility of using radiofrequency glow discharge plasma spectrometry coupled with optical emission spectrometry
(rf-GD-OES) as a rapid and simple tool to directly analyse bromine-containing flame-retardant polymeric layers is investigated
here. Polymeric layers for calibration were made by mixing appropriate amounts of tetrabromobisphenol A, bisphenol A, phloroglucinol
and diphenylmethane-4,4′-diisocyanate in tetrahydrofuran. The corresponding blanks (polymers without tetrabromobisphenol A)
were also prepared. Detection of bromine was investigated both in the visible (at 470.48 nm) and in the near-infrared (at
827.24 nm) regions, using a charge-coupled device for detection. Discharge parameters affecting the emission intensity of
bromine were first optimized (in argon and helium as possible plasma gases) and the analytical performance characteristics
were then evaluated. The best detection limit (0.044% Br) was achieved measuring Br I 827.24 nm in a He discharge, using a
forward power of 70 W and a pressure of 45 Torr. The linearity range extended up to 27% Br. Finally, the applicability of
the rf-GD-OES method proposed to the quantitative analysis of bromine in solid materials coated with flame-retardant commercial
paints was successfully demonstrated.
Figure Flame Retardants 相似文献
39.
Chromatography has been an important tool in marine laboratories. Since the 1960s, marine laboratories have been involved in the analysis of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and brominated flame retardants (BFRs). Column chromatography and liquid chromatography (LC) techniques have been used, mainly in the clean-up phase, while gas chromatography (GC) has been used extensively in the final determination of these contaminants. Developments have been observed from the use of packed GC columns, via capillary columns to the use of heart-cut multi-dimensional GC and comprehensive multi-dimensional GC. The progress made in interlaboratory studies and the availability of certified reference materials are discussed. 相似文献
40.
Barontini F. Marsanich K. Cozzani V. 《Journal of Thermal Analysis and Calorimetry》2004,78(2):599-619
The TG-FTIR technique was used in the present study to investigate the thermal degradation behaviour of materials containing
brominated flame retardants under fire conditions. Time-temperature profiles and oxygen concentrations typical of selected
fire scenarios were reproduced in the thermogravimetric analyzer, while the characterization of the gaseous products generated
was performed by the simultaneous FTIR analysis. FTIR analysis combined with the use of specific calibration procedures allowed
the quantitative estimation of the gaseous products evolved as a function of experimental conditions. The results obtained
allowed the straightforward assessment and the comparison of the quantities of hydrogen bromide formed in the oxidation and
thermal degradation of pure brominated flame retardants and of flame retarded materials of industrial interest. Hydrogen bromide
yields resulted dependent on the experimental conditions used, such as oxygen concentration and heating rate. Although TG-FTIR
experiments only provide a representation of the actual heterogeneous combustion products in real fire conditions, the coupled
TG-FTIR technique proved to be a straightforward experimental methodology allowing one to obtain reference data on the nature
and quantities of the macropollutants generated in a fire.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献