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21.
Liquid sulfur is a well-known liquid which exhibits a polymerization transition at Tp=159 °C. Recently, it was found from our experiments that such a transition can be induced below Tp through laser illumination and that an iridescent pattern appears under strong illumination with a pulsed laser of more than
60 mJ/cm2 pulse. It is proposed that the visible change in iridescence is due to a macroscopic reconstruction of laser-generated polymers
and that a laser-induced phase transition takes place from a freely expanded polymer phase to an ordered polymer phase when
increasing the laser illumination. To further examine this possibility, the time variation of the iridescent pattern has been
fully investigated using a macro lens, a polarized microscope and an optical microscope. In an analysis of the iridescent
pattern, a rapid decrease in the area was observed after an initial slow decrease, suggesting a type of phase transition.
Results from the observation of a quenched sulfur sample with a polarized microscope gave evidence that the iridescent region
consists of polymers. Through observation of the liquid with a microscope, a striped pattern with micrometer sized spacing
was noted in the iridescent pattern. A drastic color change was observed in the pattern from its generation to its disappearance.
Sample thickness dependence of the pattern was also observed. These results were well explained by assuming the self-arrangement
of laser-generated colloidal polymers. 相似文献
22.
《中国化学快报》2020,31(6):1410-1414
Since the discovery of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) in the process of municipal solid waste incineration(MSWI),a large number of researches have been conducted to reveal their formation mechanisms and emission characteristics.As one of national priority control pollutants,chlorinated organics are inclined to transfer into PCDD/Fs in the heterogeneously catalyzed process,which has been considered to be one of great challenges in environmental catalysis.However,so far direct evidences to support such a conversion process are insufficient,and the reaction mechanisms are lack of exploration.This study investigated the catalytic elimination of chlorobenzene(CBz) over a range of industrially applied active species including Pt,Ru,V,Ce and Mn oxides,and explored their reaction byproducts,chlorine adsorption/desorption behaviors and PCDD/F formations.We found that all of these species could generate the PCDD/Fs,amongst which,Mn species were the most active for PCDD/F formation.Approximately 140 ng I-TEQg-1 PCDD/Fs were detected on the Mn-CNT surface after ageing at250℃ for 30 h.Even using the dichloromethane(DCM) as a precursor,significant PCDD/Fs were still detected.The Ru and V species were shown to generate much less polychlorinated byproducts and PCDD/Fs,owning to their sufficiently high abilities in Cl desorption,which were through the semi-Deacon and Br(?)nsted H reactions,respectively. 相似文献
23.
在"卤代烃"的教学中,基于探查学生的迷思概念,采用在教师引导下进行实验探究的策略,发展高中生有机物化学性质核心概念的理解能力。主要介绍教学内容分析、核心概念分析、学生情况分析、教学目标、教学过程和教学效果评价等。 相似文献
24.
M.S. Iovu A.M. Andriesh S.A. Buzurniuc V.I. Verlan C.I. Turta V.E. Zubareva M.I. Caraman 《Journal of Non》2009,355(37-42):1890-1892
New nanocomposite (NC) material on the base of thenoyltrifluoroacetone (TTA) coordinated with trivalent europium ions and structured with phenantroline (Eu(TTA)3Phen) and copolymer from styrene and butylmethacrylate (1:1) (SBMA) was prepared. The visible photoluminescence spectra of composites excited with N2-laser (λ = 0.337 μm) at room and T = 78 K temperatures were studied. For the Eu(TTA)3Phen/SBMA nanocomposite material emission bands located at 578, 590, 612, 675 and 705 nm can be attributed to the spin forbidden f–f transitions 5D0 → 7Fi (i = 0,1,2,3 and 4), respectively. The more intensive luminescence band situated at 612 nm with the half width of 3 nm is connected to the Eu3+ ion electronic transition 5D0 → 7F2. It was shown that the maximum intensity of photoluminescence occurs at the concentration of 15% of the Eu(TTA)3Phen in the SBMA polymer matrix. 相似文献
25.
In this work, we probed the effects of a common surfactant, sodium dodecylbenzene sulfonate (NaDDBS), on the particle size of iron (III) oxides formed via a modified sol-gel synthesis. The goal was to create tunable nanosized particles via a method that combines the efficiency and advantages of the sol-gel process, but inhibits the formation of a gel. Two different metal salt precursors were used, ferric nitrate nonahydrate, Fe(NO3)3 · 9H2O, and ferric chlorate hexahydrate, FeCl3 · 6H2O. The particle size of the dried gel was 4.5 nm for Fe(NO3)3 · 9H2O and 3.6 nm for FeCl3 · 6H2O. In the presence of the surfactant FeCl3 · 6H2O formed a gel and Fe(NO3)3 · 9H2O was unable to gel, but the new particle sizes were 4.9 nm and 3.2 nm, respectively. The addition of the surfactant in the later stages of the process afforded the stabilization of independent nanoparticles of the same size as those obtained in the systems that gelled. 相似文献
26.
27.
R. W. Frei 《Chromatographia》1982,15(3):161-166
Summary Reaction detectors are considerably enhancing the application potential of HPLC particularly when dealing with trace analysis in complex matrices. In principle one distinguishes between segmented and non-segmented reactor system. The theory of band broadening of these designs and some criteria for the choice of the proper type are brieffly discussed. It seems that with a proper construction of the phase separators segmented systems have a wider range of applicability. Applications of reaction detectors in the areas of pharmaceutical and environmental analysis are discussed. 相似文献
28.
Summary A new technique has been developed for the concentration of organics in aqueous solutions. Volumes greater than 100 ml can be utilized in this system, which previously could not have been done without a distillation or solvent extraction procedure. The method is based on the passage of the solution through uncoated capillary columns of various materials such as polyethylene, copper, aluminum, nickel, and many other metal and/or polymer columns of different dimensions. It is possible to achieve trace level analysis at the ppb to ppt level without the interferences inherent in other existing methods. The purification of solvents has been successfully demonstrated in this preliminary study, and will be discussed along with our suggestions for future investigations.Paper presented at the 21st Symposium on Advances in Chromatography, Oslo, Norway, June 3–6, 1985. 相似文献
29.
Summary A novel technique has been developed for the analysis of trace organics in aqueous solutions. Concentration of organics is effected by passage of the solution being analysed through uncoated plastic or metal capillaries as reported. The concentrated organics are then desorbed from the capillary using an organic solvent, and the desorbed solution is subsequently analysed by gas chromatography. Organics trapped inside a variety of columns have been recovered by solvent desorption in this manner using a number of different solvents, mixed solvents, different solvent volumes, different solvent flow rates through the capillary column and at different desorption temperatures, and the effects of these variables on the efficiency of desorption are discussed. 相似文献
30.
超临界流体萃取分离离子液体与有机物及其相平衡的研究 总被引:6,自引:0,他引:6
离子液体具有一些优良的物理和化学性质,非常有希望成为传统有机溶剂的替代溶剂.但是如何从过程物流中分离和回收离子液体将是其工业化应用的一个很大挑战.蒸馏、液液萃取和超临界萃取是目前已知的三个可行的方法.其中超临界萃取可应用于离子液体与挥发的或相对不挥发的有机物的分离,而且不存在相间交叉污染.本文从二元体系相平衡、三元体系相平衡、模型化研究和萃取实验结果方面介绍了超临界萃取方法的最新研究进展,在此基础上提出了用超临界丙烷替代超临界二氧化碳作为萃取溶剂的新思路,并探讨了该领域今后的研究方向和工业化前景. 相似文献