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991.
The effects of preparation conditions, component ratio, and pretreatment temperature (1000–1550‡C) of silica-alumina samples
on their phase composition, texture characteristics, and catalytic properties are studied in the reaction of the oxidative
dehydrogenation of propane by sulfur dioxide. It is shown that the samples contain individual silicon and aluminum oxides.
The product of their interaction (mullite) is formed only at 1550°C. Mesoporous and macroporous catalysts with monoand polydispersed
pore distributions over sizes are obtained. It is found that the porous structure of the catalyst plays a key role in the
process of the oxidative dehydrogenation of propane in the presence of sulfur dioxide at 600–700°C. The apparent rate of propylene
formation increases with an increase in the pore volume with radii between 10 and 100 nm. Propane is transformed into propylene
more selectively on the catalyst where the pores with radii of 10–100 nm dominate; narrower pores (< 10 nm) are favorable
for the formation of coke and complete oxidation products. 相似文献
992.
993.
Bojidarka B. Ivanova Michael Spiteller 《Journal of inclusion phenomena and macrocyclic chemistry》2013,75(1-2):211-221
Experimentally and theoretically were studied the physical properties of 19 new Schiff’s bases and their different protonated forms, depending on reaction conditions. It was elucidated the correlation between the type of molecular architecture, substituents and pH of the medium on first hyperpolarizability (β) with regard to the potential application of these compounds as organic nonlinear optical materials. The structure and optical properties were also studied, comparing quantum chemical data and experimental results from the mass spectrometry, electronic absorption, diffuse reflectance, and fluorescence spectroscopy, vibrational spectroscopy in condense phase, nuclear magnetic resonance, as well as thermal methods. 相似文献
994.
995.
Mark J. Tobin Ljiljana Puskar Jafar Hasan Hayden K. Webb Carol J. Hirschmugl Michael J. Nasse Gediminas Gervinskas Saulius Juodkazis Gregory S. Watson Jolanta A. Watson Russell J. Crawford Elena P. Ivanova 《Journal of synchrotron radiation》2013,20(3):482-489
The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada (Psaltoda claripennis) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS‐IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin‐Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self‐cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher‐spatial‐resolution distribution images in a shorter time than was achievable at the AS‐IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS‐IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for example, industry applications. 相似文献
996.
Eduard BuzetzkiKatarína Sidorová Zuzana CvengrošováJán Cvengroš 《Journal of Analytical and Applied Pyrolysis》2011,92(2):314-323
Cracking of vegetable oils and animal fats carried out with a view to preparing fuels or fuel components for diesel engines is one of the options of reducing high molecular weight and viscosity of natural triacylglycerols (TAG). We have found out that lignocellulose shows a surprisingly high catalytic activity in TAG cracking comparable and equivalent to that achieved with zeolite catalysts NaY and clinoptilolite. This paper presents results obtained from cracking of rapeseed, sunflower, soybean and jatropha oils, lard and used cooking oils in the presence of woody sawdust, cereal straw and waste paper used as catalysts. The yield of liquid products in the feedstock was 80-90% relative to the feedstock TAG at temperatures of 350-440 °C applied for a period of 20-30 min. The yield of treated condensates having properties similar to those of fossil diesel reached, after water separation and evaporation of the volatile fraction up to 190 °C, 70-80% of the feedstock TAG. The type of the TAG and the lignocellulosic catalyst used had no significant effect on the product yield and its parameters. Liquid condensates obtained via catalysis with lignocellulosic catalysts had similar composition and properties as condensates produced by zeolite-catalyzed cracking. Blends of treated condensates of 5-10 vol.% with fossil diesel are compliant with the EN 590 standard and can thus be used as fuels for diesel engines. 相似文献
997.
Ondřej Kaman Tereza Dědourková Jakub Koktan Jarmila Kuličková Miroslav Maryško Pavel Veverka Radim Havelek Karel Královec Karolína Turnovcová Pavla Jendelová Adam Schröfel Ladislav Svoboda 《Journal of nanoparticle research》2016,18(4):100
Magnetic oxide nanoparticles provide a fascinating tool for biological research and medicine, serving as contrast agents, magnetic carriers, and core materials of theranostic systems. Although the applications rely mostly on iron oxides, more complex oxides such as perovskite manganites may provide a much better magnetic performance. To assess the risk of their potential use, in vitro toxicity of manganite nanoparticles was thoroughly analysed and compared with another prospective system of Mn–Zn ferrite nanoparticles. Magnetic nanoparticles of La0.63Sr0.37MnO3 manganite were prepared by two distinct methods, namely the molten salt synthesis and the traditional sol–gel route, whereas nanoparticles of Mn0.61Zn0.42Fe1.97O4 ferrite, selected as a comparative material, were synthesized by a new procedure under hydrothermal conditions. Magnetic cores were coated with silica and, moreover, several samples of manganite nanoparticles with different thicknesses of silica shell were prepared. The size-fractionated and purified products were analysed using transmission electron microscopy, dynamic light scattering, measurement of the zeta-potential dependence on pH, IR spectroscopy, and SQUID magnetometry. The silica-coated products with accurately determined concentration by atomic absorption spectroscopy were subjected to a robust evaluation of their cytotoxicity by four different methods, including detailed analysis of the concentration dependence of toxicity, analysis of apoptosis, and experiments on three different cell lines. The results, comparing two manganese-containing systems, clearly indicated superior properties of the Mn–Zn ferrite, whose silica-coated nanoparticles show very limited toxic effects and thus constitute a promising material for bioapplications. 相似文献
998.
Simultaneous determination of praziquantel,pyrantel embonate,febantel and its active metabolites,oxfendazole and fenbendazole,in dog plasma by liquid chromatography/mass spectrometry 下载免费PDF全文
Gabriella Klausz Éva Keller Zoltán Sára Péter Székely‐Körmöczy Péter Laczay Kornélia Ary Péter Sótonyi Kálmán Róna 《Biomedical chromatography : BMC》2015,29(12):1859-1865
A liquid chromatography–electrospray–mass spectrometry method (LC/MS) has been developed and validated for determination of praziquantel (PZQ), pyrantel (PYR), febantel (FBT), and the active metabolites fenbendazole (FEN) and oxfendazole (OXF), in dog plasma, using mebendazole as internal standard (IS). The method consists of solid‐phase extractions on Strata‐X polymeric cartridges. Chromatographic separation was carried out on a Phenomenex Gemini C6‐Phenyl column using binary gradient elution containing methanol and 50 mm ammonium–formate (pH 3). The method was linear (r2 ≥ 0.990) over concentration ranges of 3–250 ng/mL for PYR andFEB, 5–250 ng/mL for OXF and FEN, and 24–1000 ng/mL for PZQ. The mean precisions were 1.3–10.6% (within‐run) and 2.5–9.1% (between‐run), and mean accuracies were 90.7–109.4% (within‐run) and 91.6–108.2% (between‐run). The relative standard deviations (RSD) were <9.1%. The mean recoveries of five targeted compounds from dog plasma ranged from 77 to 94%.The new LC/MS method described herein was fully validated and successfully applied to the bioequivalence studies of different anthelmintic formulations such as tablets containing PZQ, PYR embonate and FBT in dogs after oral administration. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
999.
1000.
Šárka Lipnická Dr. Martin Bělohradský Viliam Kolivoška Assoc. Prof. Dr. Lubomír Pospíšil Dr. Magdaléna Hromadová Dr. Radek Pohl Dr. Jana Vacek Chocholoušová Dr. Jaroslav Vacek Dr. Jan Fiedler Dr. Irena G. Stará Dr. Ivo Starý 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):6108-6121
Short monodisperse oligo‐ (para‐phenyleneethynylene) (pOPE) units bearing laterally attached tetrathio‐substituted tetrathiofulvalene (TTF) units have been synthesised from functionalised aromatic building blocks by using the Sonogashira cross‐coupling methodology. The unusual redox properties of these TTF–pOPE conjugates were observed by employing electrochemical methods, such as cyclic voltammetry and exhaustive electrolysis. We found that formally one half of the TTF units in the pOPE monomer 1 , dimer 2 , and trimer 3 (with 2, 4, and 6 TTF units, respectively) are electrochemically silent during the first‐step oxidation at 0.49 V. We propose the formation of persistent mixed‐valence complexes from the TTF and TTF+. units present in an equal ratio. Such mixed‐valence dyads (single or multiple in the partially oxidised 1 – 3 ) exhibit an unusual stability towards oxidation until the potential of the second oxidation at 0.84 V is achieved. This finding suggests that below this potential the oxidation of the respective mix‐valence complexes is extremely slow. 相似文献