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51.
Pavlína Peikertová Lenka Kulhánková Lucie Neuwirthová Jonáš Tokarský 《Chemical Papers》2017,71(2):379-385
Conducting polymer polyaniline which is nowadays in forefront of the interest was in our study prepared in a form of thin films from anilinium sulfate by its chemical oxidation using ammonium peroxydisulfate. During the oxidation process, the polyaniline was deposited on glass slides and immersed into reaction mixture. Two sets of polyaniline thin films were prepared with different oxidation times (10, 20, 30, and 40 min). The first set was kept dry in desiccator and the second one was freely exposed to air moisture. Raman spectroscopy, nondestructive technique which is very sensitive to changes in structure of polymers, was used for the characterization of the protonation state of prepared polyaniline thin films. It was found that storage conditions affect the protonation state which in case of samples kept in desiccator is maintained without significant changes for longer time. Raman spectroscopy also revealed the dependence of protonation state on the oxidation time and 10 min proved as not sufficient for the creation of the protonation form of polyaniline. 相似文献
52.
Twenty nine phenolic compounds comprising nine phenolic acids, sixteen flavonoids (including eight tea catechins, glycosides and aglycones), four coumarins plus caffeine were analysed within 20 min using ultra high performance liquid chromatography (UHPLC) with PDA detection. UHPLC system was equipped with C18 analytical column (100 mm × 2.1 mm, 1.7 μm), utilising 0.1% formic acid and methanol mobile phase in the gradient elution mode. The developed method was tested for the system suitability: resolution, asymmetry factor, peak capacity, retention time repeatability and peak area repeatability. The method was fully validated in the terms of linearity (r2 > 0.9990 for all 30 compounds), range (typically 1-100 mg L−1), LOD, LOQ, inter/intra-day precision (<3% and <9% respectively) and inter/intra-day accuracy (typically 100 ± 10%). Subsequently the method was applied to the identification (spectral information and peak purity calculations were profited) and quantification of phenolic compounds and caffeine present in tea infusions and extracts. 相似文献
53.
Lucie Strnadlová Petra Šulcová Mario Llusar 《Journal of Thermal Analysis and Calorimetry》2010,100(2):661-665
The inorganic ceramic compounds based on the CeO2 belong into the group of high-temperature pigments. The pigments have been prepared by the classical dry process (i.e. solid-state
reaction) in the temperature range from 1,300 to 1,600 °C and by the coprecipitation at the three different temperatures:
400, 600 and 1,100 °C. The principal of these pigments makes the host lattice of the CeO2, which is doped by terbium ions. This incorporation of the doped ions leads to obtaining of the interesting dark orange colour
after application into ceramic glaze. The aim of our research was to improve and optimize the synthesis conditions of these
pigments. The samples were submitted to thermal analysis (TG–DTA) for determination of the temperature interval of the pigment
formation and the thermal stability of pigments. The compounds were also measured from the point of view of their colouring,
structure and particle size distribution. 相似文献
54.
Lucie Loukotková Eva Tesařová Zuzana Bosáková Pavel Repko Daniel W. Armstrong 《Journal of separation science》2010,33(9):1244-1254
Retention and enantioseparation behavior of ten 2,2′‐disubstituted or 2,3,2′‐trisubstituted 1,1′‐binaphthyls and 8,3′‐disubstituted 1,2′‐binaphthyls, which are used as catalysts in asymmetric synthesis, was investigated on eight chiral stationary phases (CSPs) based on β‐CD, polysaccharides (tris(3,5‐dimethylphenylcarbamate) cellulose or amylose CSPs) and new synthetic polymers (trans‐1,2‐diamino‐cyclohexane, trans‐1,2‐diphenylethylenediamine and trans‐9,10‐dihydro‐9,10‐ethanoanthracene‐(11S,12S)‐11,12‐dicarboxylic acid CSPs). Normal‐, reversed‐phase and polar‐organic separation modes were employed. The effect of the mobile phase composition was examined. The enantiomeric separation of binaphthyl derivatives, which possess quite similar structures, was possible in different enantioselective environments. The substituents and their positions on the binaphthyl skeleton affect their properties and, as a consequence, the separation system suitable for their enantioseparation. In general, the presence of ionizable groups on the binaphthyl skeleton, substitution with non‐identical groups and a chiral axis in the 1,2′ position had the greatest impact on the enantiomeric discrimination. The 8,3′‐disubstituted 1,2′‐binaphthyl derivatives were the most easily separated compounds in several separation systems. From all the chiral stationary phases tested, cellulose‐based columns were shown to be the most convenient for enantioseparation of the studied analytes. However, the polymeric CSPs with their complementary behavior provided good enantioselective environments for some derivatives that could be hardly separated in any other chromatographic system. 相似文献
55.
Pavel Řezanka Klára Navrátilová Pavel Žvátora David Sýkora Pavel Matějka Ivan Mikšík Václav Kašička Vladimír Král 《Journal of nanoparticle research》2011,13(11):5947-5957
In this study, spherical gold nanoparticles (GNPs) of 14.7 nm diameter, prepared by citrate reduction of a gold(III) salt
and characterized by UV–Vis absorption spectrometry and transmission electron microscopy, were modified by a covalent attachment
of 6I-O-(3-mercaptopropyl)β-cyclodextrin (β-CD-SH) or per-6-deoxy-per-6-mercapto-β-cyclodextrin (β-CD-SH7). Subsequently, via three
alternative approaches, β-CD-modified GNPs were immobilized onto the inner wall of the fused-silica (FS) capillaries and applied
as special stationary phases for open-tubular capillary electrochromatography (OT-CEC). The first immobilization procedure
was based on pre-derivatization of a FS capillary with (3-mercaptopropyl)trimethoxysilane (MPTMS) followed by subsequent reactions
with GNPs and β-CD-SH or β-CD-SH7. The other two preparation protocols took advantage of sol–gel approach gaining a significant
increase in the interaction surface for solutes. In both instances, the sol–gel created 3D structure was further covalently
modified with GNPs. Serving that purpose, either β-CD-SH7 modified GNPs were used for the immobilization into the sol–gel
matrix (“one-step sol–gel technique”) or native GNPs were immobilized first into the sol–gel matrix and subsequently modified
with β-CD-SH7 (“two-step sol–gel technique”). The separation performance of CD-GNPs modified FS capillaries was tested by
OT-CEC in reversed-phase mode applied to separation of a model mixture of five polyaromatic hydrocarbons. The highest separation
efficiencies were obtained with the capillaries prepared by two-step sol–gel technique. However, with respect to the relatively
low reproducibility of this method, the first of the above preparation procedures, i.e., a simple pre-derivatization of the
FS capillary with MPTMS ensued with β-CD-SH7-GNPs immobilization seems to be more feasible approach providing decent separation
efficiency. 相似文献
56.
57.
We report on recent microscopic calculations of reaction properties based upon the nuclear structure of the ab initio no-core shell model (NCSM). 相似文献
58.
Bis-1,2-dicarbollylcobaltate anion, labelled by 60Co, forms ionic associates with cations of some incapacitating agents. Their stability and partition between aqueous 0.1 mol.L−1 HCl and chloroform were investigated radiometrically. A method of competitive extraction was proposed for some anions of
dyes which were so far used for extraction-spectrophotometric determination of some agents. 相似文献
59.
Jaromíra Chýlková Markéta Tomášková Lenka Janíková Renáta Šelešovská Tomáš Navrátil Petra Chudobová 《Chemical Papers》2017,71(6):1047-1054
A sensitive voltammetric method for the determination of pyrogallol (PY) was developed employing a boron-doped diamond electrode (BDDE). The composition of the supporting electrolyte was investigated during the development of the methodology. Linear sweep voltammetry (LSV) under the optimized experimental conditions was applied for PY determination with a limit of detection and limit of quantification of 0.85 and 2.82 μmol L?1, respectively. These values are satisfactory for application to real samples. The usability of this method for the quantification of pyrogallol was in range from 2.82 to 296.00 μmol L?1. Finally, the developed method was successfully used for the analysis of real samples of biodiesel produced from rapeseed oil and its blend with diesel fuel. Samples of biodiesel and biodiesel blends were analyzed directly in an electrochemical cell, while samples with very low concentrations of PY in biodiesel were extracted with water using the proposed simple and fast process. 相似文献
60.
Pure anomers of either α or β 3-(2-deoxyribofuranosyl)propynoates reacted with the tetramethylcyclobutadiene–aluminum trichloride complex to yield the corresponding diastereoisomeric Dewar benzenes. Thermal- or ultraviolet light–initiated rearrangement gave rise to highly substituted C-aryldeoxyribosides as single anomers. The same compounds as well as other substituted deoxyribosides were obtained also by transition metal–mediated cycloaddition reactions. 相似文献