全文获取类型
收费全文 | 86篇 |
免费 | 5篇 |
专业分类
化学 | 73篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 16篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 1篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有91条查询结果,搜索用时 15 毫秒
31.
Fluorene‐based rib waveguides with optimized geometry for long‐term amplified spontaneous emission stability
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gonzalo Del Pozo Noureddine Bennis Xabier Quintana Jose Manuel Otón Jinyi Lin Linghai H. Xie Qi Wei Ruidong Xia Ramon Bernardo‐Gavito Daniel Granados Juan Cabanillas‐Gonzalez 《Journal of Polymer Science.Polymer Physics》2015,53(15):1040-1045
Amongst the different optoelectronic applications of conjugated polymers, waveguide amplifiers and optically pumped lasers are those requiring larger photochemical stability, owing to the large irradiation conditions under operation. In this context, suitable waveguide optimization enabling the reduction of amplified spontaneous emission (ASE) threshold values appears as important as synthetic chemistry protocols to promote polymer robustness against photo‐oxidation. In this work, we develop rib waveguides with different geometries based on four different fluorene‐based compounds and assess the influence of rib confinement on ASE properties. We observe ASE threshold values as low as 8.9 × 10?4 mJ cm?2, being among the lowest threshold values reported so far on blue emitting polymer/oligomer waveguides. We demonstrate that the enhanced ASE efficiency on some of these rib waveguides leads to a fivefold increase in operation lifetime respect to spin‐coated slab waveguides, thus confirming the impact of waveguide geometry on ASE operation stability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1040–1045 相似文献
32.
A. Guiberteau Cabanillas M.I. Rodríguez Cáceres M.A. Martínez Cañas J.M. Ortiz Burguillos T. Galeano Díaz 《Talanta》2007,72(3):932-940
Nalidixic acid (NA) and its main metabolite, 7-hydroximethylnalidixic acid (OHNA), are quinolones antibacterial used as agents used for the treatment of urinary tract infection. For both compounds an adsorption process on a hanging mercury electrode (HMDE). On this basis, a square wave adsorptive stripping voltammetry (SWadSV) method has been developed for the individual and simultaneous determination of NA and OHNA. The variables that affect to accumulation process, such as concentration of perchloric acid, accumulation potential and accumulation time have been optimised by using an experimental design (concretely a Box-Behnken design with three levels) together with the response surface methodology (RSM). Calibration curves were linear in the range (0-1.38) × 10−7 mol L−1 for NA and (0-3.23) × 10−8 mol L−1 for OHNA, in the optimized conditions, with detection limits of 9.48 × 10−9 mol L−1 and 8.06 × 10−10 mol L−1 for NA and OHNA, respectively. The method was applied to urine samples containing only one of the analytes with satisfactory recoveries. As the voltammetric signals of these compounds show a high overlapping, different chemometric methods, such as classical least squares (CLS), partial least squares (PLS), principal component regression (PCR) and artificial neural network (ANN) have been used for the resolution of the mixture. The analysis of these compounds in urine samples were carried out using the different chemometric tools and the best recoveries were obtained by using ANN. No pre-treatment of the sample was necessary. 相似文献
33.
Ramón Encinas García Agustina Guiberteau Cabanillas Lorenzo Calvo Blázquez Rosa María García-Moncó Carra Antonio Sánchez Misiego 《Mikrochimica acta》1994,116(1-3):73-81
The polarographic behaviour of 2-benzilideniminobenzohydroxamic acid (2-BIBH) solutions and of 2-BIBH solutions in the presence of Mo(VI) have been studied by using differential pulse polarography and cyclic voltammetry. The polarographic characteristics of the resulting waves have been studied and possible mechanisms of the processes involved have been proposed. A linear relationship has been observed betweenI
p and Mo(VI) concentration in the range 2×10–6 to 1.6×10–5
M when using 3×10–4
M 2-BIBH. Standard deviations of 5.6×10–8 and 1.2×10–8
M were found for 3×10–6 and 8 × 10–6
M Mo(VI), respectively. 相似文献
34.
The kinetics of the reaction between double stranded DNA (dsDNA) and formamide is monitored at the single DNA molecule level. We find that stretching of the DNA leads to an accelerated reaction rate and to a shift in the final equilibrium concentrations. The larger the stretching force, the faster the reaction and the larger the denatured fraction of the product DNA. The single molecule kinetics is obtained from the change in the contour length of the DNA which, in turn, is measured using optical tweezers on a microbead-single DNA molecule-cover slip construct. 相似文献
35.
Berzas Nevado JJ Guiberteau Cabanillas C Villaseñor Llerena MJ Rodríguez Robledo V 《Journal of chromatography. A》2005,1072(2):249-257
A chiral capillary electrophoresis (CE) method has been developed allowing the enantiomeric separation of racemic citalopram (R-(-) and S-(+) citalopram) using as chiral selector carboxymethyl-gamma-cyclodrextrin (CM-gamma-CD). The influence of chemical and instrumental parameters on the separation such as cyclodextrin (CD) and buffer concentrations, buffer pH, voltage, injection pressure, ..., was investigated. Good chiral separation of the racemic mixture was achieved in less than 4 min using a fused-silica capillary and as background electrolyte (BGE) a phosphate buffer solution (20 mM, pH 7) containing 0.15% (w/v) of CM-gamma-CD as chiral selector. The separation was driven in normal polarity mode at 15 degrees C, 30 kV and hydrodynamic injection. In order to validate the method, the stability of the solutions, precision (repeatability, reproducibility and F-Snedecor test), linearity (Lack of Fit and ANOVA tests) accuracy (98-101%), detection and quantitation limits (0.06 and 0.2 mg L(-1), respectively), on a selected analytical placebo, were examined. Besides, a robustness test was performed using the Plackett-Burman fractional factorial experimental design using a matrix of 15 experiments for seven factors (internal parameters) with a statistical treatment suggested by Youden and Steinner. The proposed method is fast, sensitive, inexpensive and, besides, it has been evaluated by means of an extensive validation study and an exhaustive robustness test. The scope of this validated and robust method has been proved in the analysis of four pharmaceutical formulations; two of them (recently available in Spain), which just contained S-(+)-citalopram (escitalopram) as active principle. Recoveries between 101 and 103%, with regard to their nominal contents were obtained. In the other two pharmaceutical ones, the method provided the separation and quantification of both chiral isomers in the existing racemic mixture. 相似文献
36.
Berzas Nevado JJ Rodríguez Flores J Guiberteau Cabanillas C Villaseñor Llerena MJ Contento Salcedo A 《Talanta》1998,46(5):933-942
A very simple spectrophotometric method is described for resolving ternary mixtures of the food colorants Tartrazine, Sunset Yellow and Ponceau 4R by using the first derivative of the ratio spectra with measurements at zero-crossing wavelengths. Calibration graphs are linear up to 20 mg l(-1) of Tartrazine (E-102), 40 mg l(-1) of Sunset Yellow (E-110) and 32 mg l(-1) of Ponceau 4R (E-124). Standard deviations of 0.9, 0.8 and 2.4% were obtained for nine standards of 8 mg l(-1) of Tartrazine, 8 mg l(-1) of Sunset Yellow and 8 mg l(-1) of Ponceau 4R, respectively. This method was satisfactorily used for determining synthetic mixtures of these colorants in different ratios (from 1:1:1 to 1:5:5 or even higher) with recoveries in 94-105% range and it was successfully applied over three commercial products containing the three dyes and it did not require any separation step. The results were compared with those obtained by HPLC and very similar values were found by both methods. 相似文献
37.
Avalos M Babiano R Cabanillas A Cintas P Jiménez JL Palacios JC Aguilar MA Corchado JC Espinosa-García J 《The Journal of organic chemistry》1996,61(21):7291-7297
The dipolar cycloaddition reactions of 3-methyl-2-(4-nitrophenyl)-4-phenyl-1,3-oxazolium-5-olate (1) and chiral nitroalkenes derived from D-galacto- and D-manno-hept-1-enitols 2 and 3 were found to proceed in a regiospecific manner to afford acyclic pyrrole C-nucleosides (5 and 6) in satisfactory yields. This protocol constitutes a novel and efficient route to such substances. Remarkably, the regiochemistry of this mesoionic-based cycloadditive process is exactly opposite that anticipated from the FMO view of 1,3-dipolar cycloadditions. A preliminary semiempirical PM3 study also reveals the inconsistencies of semiempirical studies with experimental data by applying the FMO approach to münchnone cycloadditions. The structural characteristics of the reagents, products, and transition states have been determined, and this calculation also evaluates the influence of steric and electronic factors involved. Ab initio MO calculations using a model system consisting of 1,3-oxazolium-5-olate with 2-(hydroxymethyl)nitroethylene were also performed. The ab initio study justifies, for the first time, the experimental results of 1,3-dipolar cycloadditions with münchnones. The process occurs through a concerted, slightly asynchronous transition state. 相似文献
38.
39.
Marina Sierra-Rodero Juan Manuel Fernández-Romero Agustina Gómez-Hens 《Mikrochimica acta》2012,179(3-4):185-192
We describe an on-chip microflow injection (μFI) approach for the determination of aminoglycoside antibiotics using chemiluminescence (CL) detection. The method is based on the inhibition of the Cu(II)-catalyzed CL reaction of luminol and hydrogen peroxide by the aminoglycosides due to the formation of a complex between the antibiotic and Cu(II). The main features of the method include small sample volumes and a fast response. Syringe pumps were used to insert the sample and the reagents into the microfluidic device. CL was collected using a fiber optic bundle connected to a luminescence detector. All instrumental, hydrodynamic and chemical variables involved in the system were optimized using neomycin as the aminoglycoside model. Inhibition is proportional to the concentration of the antibiotics. The dynamic ranges of the calibration graphs obtained for neomycin, streptomycin and amikacin are 0.3–3.3, 0.9–13.7, and 0.8–8.5?μmol?L?1, and the detection limits are 0.09, 0.28 and 0.24?μmol?L?1, respectively. The precision of the methods, expressed as relative standard deviation, is in the range from 0.8 to 5.0?%. The method was successfully applied to the determination of neomycin in water samples, with recoveries ranging from 80 to 120?%. Figure
Chemical and instrumental systems of the method 相似文献
40.
L. A. Cano M. V. Cagnoli S. J. Stewart E. D. Cabanillas E. L. Romero S. G. Marchetti 《Hyperfine Interactions》2010,195(1-3):275-280
Monodisperse iron oxide nanoparticles (NPs) of 4 nm were obtained through high-temperature solution phase reaction of iron (III) acetylacetonate with 1, 2-hexadecanediol in the presence of oleic acid and oleylamine. The as-synthesized iron oxide nanoparticles have been characterized by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and magnetic measurements. The species obtained were Fe3O4 and/or $\upgamma$ -Fe2O3. These NPs are superparamagnetic at room temperature and even though the reduced particle size they show a high saturation magnetization (MS ≈ 90 emu/g). 相似文献