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991.
992.
Evandro A. de Morais Luis V.A. Scalvi Alberto A. Cavalheiro Américo Tabata José Brás B. Oliveira 《Journal of Non》2008,354(42-44):4840-4845
Some very relevant optical, electrical, and structural properties of SnO2 doped with rare-earth ions Er3+ and Eu3+ are presented. Films are produced by the sol–gel-dip coating process, and may be described as a combination of nanoscopic dimension crystallites (about 3–10 nm) with their respective intergrain potential barriers. The Er3+ and Eu3+ ions are expected to act as acceptors in SnO2, which is a natural n-type conductor, inducing a high degree of charge compensation. Electron trapping and emission spectra data are presented and are rather distinct, depending on the location of the rare-earth impurity. This behavior allows the identification of two distinct centers: located either in the SnO2 lattice or segregated at the particles surface. Based on a model for thermally activated cross-section defects, the difference between the capture energy of the photo-excited electron and the intergrain potential barrier is evaluated, leading to distinct values for high and low symmetry sites. A higher distortion in the lattice of undoped SnO2 and SnO2:Eu (1 at.%) was evaluated from Rietveld refinements of X-ray diffraction data. This was confirmed by Raman spectra, which are associated with the particles size and disorder. By comparing the samples with the same doping concentration, it was found that this disorder is higher in Eu-doped SnO2 than in Er-doped SnO2, which is in agreement with a higher energy for the lattice relaxation in the trapping process by Eu3+ centers. 相似文献
993.
Lili He Christy L. Haynes Francisco Diez‐Gonzalez Theodore P. Labuza 《Journal of Raman spectroscopy : JRS》2011,42(6):1428-1434
A method for rapid detection of foreign protein contamination in complex food matrices is critically needed. Here we present a novel method that combines immunomagnetic separation (IMS) and surface‐enhanced Raman scattering (SERS) to detect ovalbumin (OVA), an egg white protein, added into whole milk. IMS was used to specifically capture the OVA out of the milk. Then SERS was applied to analyze the IMS eluate using silver dendrites as the substrate. Two SERS sample preparation methods, namely solution based and substrate based, were used to prepare the IMS eluate for SERS analysis. Results show both methods were able to detect 1 µg OVA in 1 ml milk (1 part per million). Based on the results of principal component analysis and partial least‐squares analysis, solution SERS was more capable of quantitative analysis, while substrate SERS was more sensitive for qualitative analysis. The total analytical time for IMS–SERS was less than 20 min, which satisfied the requirement of rapid detection in a milk processing facility. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
994.
Juan Luis García Guirao Jaume Llibre Wei Gao 《Journal of Difference Equations and Applications》2020,26(2):203-208
The objective of this work is to present sufficient conditions for having positive topological entropy for continuous self-maps defined on a closed surface by using the action of this map on the homological groups of the closed surface. 相似文献
995.
996.
J. Luis Lopez-Miranda M. A. Vázquez González F. Mares-Briones J. A. Cervantes-Chávez R. Esparza G. Rosas R. Pérez 《Research on Chemical Intermediates》2018,44(12):7479-7490
In this work, silver nanoparticles were synthesized using Salvia microphylla Kunth leaves extract as reducing agent and stabilizing agent. The effect of reaction time and plant extract amount on the biosynthesized nanoparticles were studied. The UV–Vis spectrum indicated that silver nanoparticles show a characteristic surface plasmon resonance at 427 nm. X-ray diffraction experiments show that the silver nanoparticles have a face-centered cubic crystal structure. The density of nanoparticles increases with increasing extract concentration and reaction time. TEM and SEM observations showed well-dispersed quasi-spherical nanoparticles sized in the range of 15–45 nm. The FT-IR analysis suggested the involvement of phenolic compounds in the reduction and stabilization of silver nanoparticles. Synthesized silver nanoparticles showed good antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Finally, the catalytic properties of silver nanoparticles were demonstrated through the degradation of congo red and methyl orange. 相似文献
997.
Cristiane dos Santos Luis Fernando Wentz Brum Robelsa de Fátima Vasconcelos Sérgio Knorr Velho João Henrique Zimnoch dos Santos 《Journal of Sol-Gel Science and Technology》2018,86(2):351-364
Natural dyes, namely, indigo carmine, cochineal carmine, curcumin and annatto, were encapsulated in silica by a sol-gel method and applied in the dyeing of different textile fibers by exhaustion. For comparative reasons, dyeing using the free (non-encapsulated) bare dyes was also carried out. The hybrid materials were analyzed by a set of techniques to investigate their elemental, structural, textural and morphological properties, and the results showed that it was possible to obtain stable natural dyes for applications in textile dyeing. The silica-structured dyes showed better affinities with the fibers (WO, PA, PAC and PET) in dyeing with cochineal carmine, while cotton (CO) showed better affinities with the encapsulated curcumin and annatto dyes. The performances of the encapsulated dyes were evaluated by color and washing fastness measurements and resulted in improved dye absorption and wash fastness properties. The color change and color transfer measurements of the encapsulated dyes were better (rated at 4–5 on a scale of 1–5) compared to the bare dyes. 相似文献
998.
Ma. Carmen García-González Eduardo Hernández-Vázquez Fabio A. Vengochea-Gómez Luis D. Miranda 《Tetrahedron letters》2018,59(9):848-852
1,4- or 1,5-migration of a double bond of dehydroalanines under palladium catalysis is reported. The process occurred with several highly-substituted dehydroalanines under mild typical Heck reaction conditions. Although this was one of the first reports of a palladium-catalyzed 1,5-olefin migration, the outcome of the reaction was susceptible to the starting material. Mechanistically, the process involved a five- (1,4-migration) or six-membered ring (1,5-migration) organopalladium intermediate, which cleaved a C–N bond in an β-amino elimination process. 相似文献
999.
1000.
Evgeny Nikolaev Mikhail Sudakov Gleb Vladimirov Luis Fernando Velásquez-García Petr Borisovets Anastasia Fursova 《Journal of the American Society for Mass Spectrometry》2018,29(11):2173-2181
Based on the analysis of the results of the study of various designs of multi-electrode harmonized Kingdon traps, we propose a new type of trap with two merged internal electrodes that has the ability to capture and accumulate ions formed inside. We also investigated the influence of inaccuracies in the manufacture of the electrodes on the field inside such trap. The four-electrode trap, which actually degenerates into a two-electrode device with traces of two other electrodes present at the ends of the internal electrodes (their splitting) has been found as the less sensitive to inaccuracies caused by manufacturing and cutting the ends of trap electrodes. We show that a mass spectrometer with a relatively high resolving power can be created on the basis of such a trap. The creation of the traps requires the manufacture of complex electrodes with demanded accuracy of their surfaces. This becomes possible with the advent of 3D printers. 相似文献