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631.
Hitzfeld KL Gehre M Richnow HH 《Rapid communications in mass spectrometry : RCM》2011,25(20):3114-3122
A novel approach for the measurement of (37)Cl, (81)Br and (34)S in organic compounds containing chlorine, bromine, and sulphur is presented to overcome some of the major drawbacks of existing methods. Contemporary methods either require reference materials with the exact molecular compositions of the substances to be tested, or necessitate several laborious offline procedures prior to isotope analysis. In our online setup, organic compounds are separated by gas chromatography (GC) coupled to a high-temperature reactor. Using hydrogen as a makeup gas, the reactor achieves quantitative conversion of chlorinated, brominated and sulphurated organic compounds into gaseous hydrogen chloride (HCl), hydrogen bromide (HBr), and hydrogen sulphide (H(2)S), respectively. In this study, the GC interface was coupled to a quadrupole mass spectrometer operated in single-ion mode. The ion traces of either H(35)Cl (m/z 36) and H(37)Cl (m/z 38), H(79)Br (m/z 80) and H(81)Br (m/z 82), or H(2)(32)S (m/z 34) and H(2)(34)S (m/z 36), were recorded to determine the isotopic ratios of chlorine, bromine, and sulphur isotopes. The conversion interface presented here provides a basis for a novel method for compound-specific isotope analysis of halogenated and sulphur-containing compounds. Rapid online measurements of organic chlorine-, bromine- and sulphur-containing mixtures will facilitate the isotopic analysis of compounds containing these elements, and broaden their usage in fields of environmental forensics employing isotopic concepts. 相似文献
632.
Nikola Burić Ines Grozdanović Kristina Todorović Nebojša Vasović 《Journal of statistical physics》2011,145(1):175-186
Influence of small time-delays in coupling between noisy excitable systems on the coherence resonance and self-induced stochastic
resonance is studied. Parameters of delayed coupled deterministic excitable units are chosen such that the system has only
one attractor, namely the stationary state, for any value of the coupling and the time-lag. Addition of white noise induces
qualitatively different types of coherent oscillations, and we analyzed the influence of coupling time-delay on the properties
of these coherent oscillations. The main conclusion is that time-lag τ≥1, but still smaller than the refractory period, and sufficiently strong coupling drastically change signal to noise ratio
in the quantitative and qualitative way. An interval of noise values implies quite large signal to noise ratio and different
types of noise induced coherence are greatly enhanced. We also observed coincident spiking for small noise intensity and time-lag
proportional to the inter-spike interval of the coherent spike trains. On the other hand, time-lags τ<1 and/or weak coupling induce negligible changes in the properties of the stochastic coherence. 相似文献
633.
Deyan Lesigyarski Žiga Šmit Boika Zlateva-Rangelova Kristina Koseva Ivelin Kuleff 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1605-1619
Using PIXE (proton induced X-ray emission), PIGE (proton induced gamma emission) and ICP-AES (inductively coupled plasma-atomic emission spectroscopy) the concentrations of the 24 elements Al, As, Ba, Br, Ca, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Rb, S, Sb, Si, Sn, Sr, Ti, Zn and Zr in 53 archaeological glass samples from South-Eastern Bulgaria, were determined. The glasses are dated from the 1st to 6th century AD. The analytical data showed the samples to be typical soda-lime-silica glass, with natron as flux. A rather broad range of aluminium, titanium and iron impurities was found, with a tendency for more impure glass in the later periods. The decolouring agents were antimony and manganese oxides, with Sb prevailing in earlier, and Mn in later glass. 相似文献
634.
Denise Lowinsohn Patrick Gan Kristina Tschulik John S. Foord Richard G. Compton 《Electroanalysis》2013,25(11):2435-2444
The electrochemical behaviour of carbon paste electrodes prepared using nanocarbon and mineral oil was investigated and the results contrasted with different carbon and carbon pastes electrodes. The composition of carbon paste was studied by performing cyclic voltammetry performed in 0.1 M KCl solution in the presence of 4.0 mM Ru(NH3)6Cl3, a well‐characterized redox system commonly used to test the electrode behaviour. After optimisation of the paste composition, the sensors chosen were tested for the analysis and characterization of three different systems: Ru(NH3)63+/2+, FcCH2OH/FcCH2OH+ and acetaminophen. The ability to obtain high quality voltammetry from the nanocarbon electrode was demonstrated and simulation of the voltammetry allowed the extraction of electrode kinetic parameters with high precision. 相似文献
635.
636.
Adam Sobkowiak Tore Ericsson Kristina Edström Torbjörn Gustafsson Fredrik Björefors Lennart Häggström 《Hyperfine Interactions》2014,226(1-3):229-236
The tavorite polymorph of LiFeSO4F has attracted considerable attention as a cathode material for lithium ion batteries due to interesting structural and electrochemical characteristics. For the analysis of such iron-based electrode materials, Mössbauer spectroscopy has become an important and highly useful tool. In this work, we perform a detailed Mössbauer study of pristine tavorite LiFeSO4F prepared by an optimized synthesis in tetraethylene glycol as reaction media. In contrast to many reported results, we demonstrate the use of an asymmetric fitting model for the inner doublet of the spectrum, which is coupled to the structural properties of the compound. Moreover, we discuss a new approach of ascribing the Fe2?+?-doublets to the two distinct crystallographic iron sites of tavorite LiFeSO4F by comparing the Mössbauer signal intensities with the expected f-factors for the corresponding iron atom. 相似文献
637.
Deniss Klauson Olga Budarnaja Kristina Stepanova Marina Krichevskaya Tatjana Dedova Aleksandr Käkinen Sergei Preis 《Kinetics and Catalysis》2014,55(1):47-55
Photocatalysts synthesized by sol-gel method inevitably incorporate carbon together with dopants. The objective of the research consists in the synthesis and testing of photocatalytic activity of carbon-containing titanium dioxide photocatalysts calcinated at various temperatures. The optical and structural properties of the catalysts were also studied. The activity was tested in visible light in aqueous photocatalytic oxidation of three various-type pollutants, methyl-tert-butyl ether, p-toluidine and phenol, where the divergent character of the C-TiO2 catalysts was distinctively observed: methyl-tert-butyl ether and p-toluidine were oxidized with the efficiency close to or even surpassing that of UV-irradiated P25 (Evonik), whereas phenol was oxidized poorly. The observed photocatalytic activity, where quantum efficiency varied from 0.6 to 2.3 and from 0.1 to 1.2% for p-toluidine and phenol degradation respectively, may be explained by the different electrostatic properties of the catalysts’ surface and the tested substances, i.e. their interaction. This compromises the widespread usage of phenol as a reference substance for comparison of catalytic activities of catalysts. 相似文献
638.
Improving the Rate of Silver Nanoparticle Adhesion to ‘Sticky Electrodes’: Stick and Strip Experiments at a DMSA‐Modified Gold Electrode
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Emma J. E. Stuart Kristina Tschulik Joanna Ellison Richard G. Compton 《Electroanalysis》2014,26(2):285-291
The immobilisation of nanoparticles from solution at a solid surface followed by anodic stripping voltammetry is a simple technique allowing the analysis of nanoparticle concentrations and identity. We report that the modification of gold electrodes with meso‐2,3‐dimercaptosuccinic acid (DMSA) shows a useful increase in the adsorption rate of silver nanoparticles on a gold substrate showing that the chemical modification of the electrode is analytically advantageous. 相似文献
639.
Hamdi Joda Valerio Beni Noora Alakulppi Jukka Partanen Kristina Lind Linda Strömbom Daniel Latta Julian Höth Ioanis Katakis Ciara K. O’Sullivan 《Analytical and bioanalytical chemistry》2014,406(12):2757-2769
Coeliac disease is a small intestinal disorder, induced by ingestion of gluten in genetically predisposed individuals. Coeliac disease has been strongly linked to human leukocyte antigens (HLA) located on chromosome 6, with almost 100 % of coeliac disease sufferers carrying either a HLA-DQ2 or HLA-DQ8 heterodimer, with the majority carrying HLA-DQ2 encoded by the DQA1*05:01/05:05, DQB1*02:01/02:02 alleles, whereas the remaining carry the HLA-DQ8 encoded by the DQA1*03:01, DQB1*03:02 alleles. In this work, we present the development of a multiplex electrochemical genosensor array of 36 electrodes, housed within a dedicated microfluidic platform and using a total of 10 sequence-specific probes for rapid medium-high resolution HLA-DQ2/DQ8 genotyping. An evaluation of the selectivity of the designed probes was carried out with the target sequences and 44 potentially interfering alleles, including single base mismatch differentiations; good selectivity was demonstrated. The performance of the electrochemical genosensor array was validated, analyzing real human samples for the presence of HLA-DQ2/DQ8 alleles, and compared with those obtained using laboratory-based HLA typing, and an excellent correlation was obtained. Figure
Electrode array and schematic of the proposed detection approach for the medium to high resolution electrochemical genotyping of alleles associated to Coeliac disease 相似文献
640.
Her Shuang Toh Christopher Batchelor-McAuley Kristina Tschulik Richard G. Compton 《中国科学:化学(英文版)》2014,57(9):1199-1210
The interaction between citrate capped silver nanoparticles and two different thiols, mercaptohexanol(MH) and cysteine, was investigated. The thiols interacted with silver nanoparticles in a significantly contrasting manner. With MH, a sparingly soluble silver(I) thiolate complex AgSRm(Rm = –(CH2)6OH) was formed on the silver nanoparticle surface. Cyclic voltammograms and UV-vis spectra were used to infer that the AgSRm complex on the nanoparticle surface undergoes a phase transition to give a mixture of AgSRm and Ag2S-like complexes. In contrast, when silver nanoparticles were exposed to cysteine, the citrate capping agent on the silver nanoparticles was replaced by cysteine to give cysteine capped nanoparticles. As cysteine capped nanoparticles form, the electrochemical data displayed a decrease in oxidative peak charge but the UV-vis spectra showed a constant signal. Therefore, cysteine capped nanoparticles were suggested to have either inactivated the silver surface or else promoted detachment from the electrode surface. 相似文献