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81.
Eigenvectors of vibrating polyethylene chains with (200) and (110) folds have been calculated by solving the phonon-scattering problem exactly with the method of Green's function. The results are applied to analyze the resonance modes of the (200) fold (ggtgg: 1353, 1356, 1374 cm–1) and the (110) fold (approximately ggggtg: 820, 1288, 1342, 1348, 1372, 1374 cm–1) in terms of the characteristic vibrations of smaller subunits of the (200) fold (gg, gtg) and the (110) fold (ggggtg, gggg, gtg) which can be identified spectroscopcally.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday 相似文献
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83.
The fabrication of the Screen-Printed Electrode (SPE) was performed using the graphite ink to print the working (WE) and counter electrodes (CE), and silver/silver chloride path as reference electrode (RE). All the electrodes are printed in a paper substrate using screen-printing technique. The resulting SPE is characterized using scanning electron microscopy, showing all the ink layer, and subsequently optimized. The paper sample presented the cellulose fibers entanglement, extremely rough, with highly porous network. Then the graphite ink was deposited and the surface became flat, thinner and very smooth. When the silver ink was painted on top of the graphite ink, the spherical silver particles, ranged from 2–3.5 μm in size, were observed. And finally, the silver ink was covered with a AgCl layer and the particle size becomes larger with an irregular sphere-like phase. The images showed that the layers appear to be homogeneously distributed with good coverage. Then fabrication process was optimized concerning type of paper, the sanding process, the hydrophobic barrier, the electrode design and size. In summary, the optimized values included using the previously sanded matte paper with a mineral spirit layer. The design and size of the electrode were also tested to achieve the best electrochemical performance (design 3 with 3.5 cm). The final SPE was a miniaturized and flexible paper-based electrochemical electrode. In order to evaluate the electrical properties, the ohmic resistance of each ink was tested using a multimeter and the obtained values were 2.18 kΩ for the graphite ink, 2.27 Ω for the silver ink and 38.33 kΩ for the silver/silver chloride ink. That can indicate the good conductivity of each ink used in the fabrication of the electrode and the correct deposition of Ag/AgCl. Finally, the electrode was used to measure the electrochemical response of K4[Fe(CN)6] in different concentrations. Then a calibration curve was obtained from the voltammograms and a linearity was observed between the current and concentration in the range of 0.50–2.00 mM. That indicates that the SPE has potential to be used as a voltammetric electrode. 相似文献
84.
Ute Henniges Rebecca Reibke Gerhard Banik Enke Huhsmann Ulrike Hähner Thomas Prohaska Antje Potthast 《Cellulose (London, England)》2008,15(6):861-870
Degradation of cellulose in historic paper by iron gall ink is a synergistic process of both, acid hydrolysis caused by acidic
ink ingredients and oxidation catalyzed by free iron and/or copper ions. The interplay of both reactions was studied according
to the CCOA method on historic paper samples. Only minute amounts (few mg) of the samples were required to obtain profiles
of naturally present and oxidatively introduced carbonyl groups, which was done by group-selective fluorescence labeling in
combination with determination of the molecular weight distribution by GPC-MALLS. In the present study naturally occurring
degradation pathways in historic sample papers have been investigated. Different extents of oxidatitive degradation were shown
for paper with and without ink. A typical pattern of the molecular weight distribution in naturally aged papers was identified,
the peculiar feature being a distinctive shoulder in the region of low molecular weight, roughly between 25,000 and 5,000 g/mol
corresponding to a DP between 150 and 30. This pattern was a typical attribute of degraded natural samples: any artificial
aging procedures aimed at modeling natural aging processes must thus attempt to reproduce this feature. Although the historic
samples had been more severely oxidized than model papers, the inhibition of further oxidation and hydrolysis by the calcium
phytate/hydrogen carbonate treatment was evident and could be proven for the first time on the molecular level. Also on plain
paper without ink application the oxidation was suppressed and the molecular weight was stabilized on a high level. 相似文献
85.
Cellulose in historic paper documents is often damaged by the writing media used, especially iron gall ink or copper pigments.
Degradation induced by iron gall ink is suggested to be a synergistic process comprising both hydrolytic and oxidative reactions.
These processes were studied on very low sample amounts according to the CCOA and FDAM method, i.e. by fluorescence labeling
of carbonyl and carboxyl groups in combination with GPC-MALLS, respectively. This study focused on preventive means to stop
the deterioration induced by iron gall ink of cellulose and to prevent further damage, keeping in mind that a suitable conservation
treatment has to hinder both, hydrolytic and oxidative processes, at the same time. A combination of the complexing agent
calcium phytate and calcium hydrogencarbonate in aqueous solution was proved to give optimum results. To gain insight into
long term stability, an aging step was performed after treatment and different ink modifications were tested. Recording the
molecular weight distributions and the carbonyl group content over time GPC analysis verified for the first time the preventive
effect of this treatment. This effect was not only seen for the ink-covered areas, but extended also to areas remote from
the ink lines. Ink containing copper ions responded equally positively to the calcium phytate/hydrogencarbonate treatment
as the iron gall ink papers did. Gelatine, sometimes used in a similar way due to an alleged cellulose-stabilizing effect
did not have a beneficial influence on cellulose integrity when metal ions were present. 相似文献
86.
高效液相色谱法鉴定蓝色圆珠笔油墨字迹的书写时间 总被引:6,自引:2,他引:4
由圆珠笔油墨形成的契约、合同、收据和借条等可疑文件的真伪及形成时间的鉴定是目前法庭科学实验室经常遇到的问题, 因此建立一种简便、灵敏和准确的检验圆珠笔油墨字迹色痕的异同及形成时间的方法是十分必要的。文章介绍了一种可以检验圆珠笔油墨的种类及形成时间的方法。这种方法是依据高效液相色谱法分析圆珠笔油墨中染料的种类及染料随时间的变化关系来确定圆珠笔油墨字迹的异同及书写时间,染料随时间的变化可以通过相应的色谱峰的峰面积比计算而得。 相似文献
87.
建立了利用毛细管电泳光二极管阵列检测器连续波长扫描分析滚珠水性笔墨水的方法。首先考查了缓冲溶液的类型、浓度、pH值,以及电泳分离电压对分析结果的影响,同时研究了管径分别为50,75和100 nm的熔融石英毛细管对光二极管阵列检测器检测结果的影响,实验表明毛细管内径的大小与检测器的吸光强度成正比,在保证分离效果的前提下,采用管径为100 nm的毛细管可以提高吸光信号检测强度,因此在紫外和可见光的波长范围内都可以检测到吸收峰。实验确定浓度为20 mmol·L-1 、pH值为8.5的四硼酸钠作为缓冲溶液,熔融石英毛细管从进样口至检测窗口的有效长度为40 cm,内径为100 μm,电泳分离电压为15 kV。利用光二极管阵列检测器在190~600 nm波长范围内进行连续扫描检测,根据三维电泳图中紫外区和可见区电泳吸收峰的特征分析不同种类滚珠水性笔墨水。 相似文献
88.
Angela L. Dearden Patrick J. Smith Dong‐Youn Shin Nuno Reis Brian Derby Paul O'Brien 《Macromolecular rapid communications》2005,26(4):315-318
Summary: A drop‐on‐demand ink‐jet printer has been used to print a silver‐organic solution onto glass substrates. Conductive silver tracks were obtained by heat treatment of the ink‐jet printed deposits at temperatures ranging from 125 °C–200 °C in air. Resistivity values were found to have dropped to two to three times the theoretical resisitivity of bulk silver after temperatures of 150 °C and above were used.
89.
90.
The formation of insulating layers of poly(o‐phenylenediamine) via electropolymerization was performed on single carbon screen‐printed electrodes. The effects of experimental parameters on the properties of the film were investigated, allowing for technique optimization. These conditions were then used to deposit films upon surfaces of 100 interconnected electrodes, with cyclic voltammetry used to study the electroactivity of the resulting electrodes. The insulating property of the film, for use in the formation of microelectrode array amperometric sensors, was evaluated. Finally, the insulated sensors were exposed to ultrasonic ablation to form microelectrode arrays, and these were subsequently assessed using optical and electrochemical techniques. 相似文献