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81.
Janos Borszéki Günter Knapp Kurt Müller Wolfhard Wegscheider 《Mikrochimica acta》1985,87(5-6):401-415
Summary
X-ray Diffraction Analysis of Corrosion Products on Electrochemically Polarized Copper Surface
An investigation was undertaken to examine the feasibility of X-ray diffractometry for the identification and characterization of corrosion products formed, electrochemically, on copper surface in various aqueous media. The removal of the products from the metal surface was useful in overcoming serious interferences from the intense diffraction lines of copper and was most satisfactory for the identification of common film components such as cuprous oxide, cuprous chloride and cupric oxide. In addition, the results obtained for the surface film components by slow scan linear (or potentiodynamic) polarization agreed favourably with the X-ray diffraction analysis. The influence of the solution pH and temperature on the nature of the corrosion products was evident on the results obtained by both techniques. The dominance of cuprous oxide as the major film component at the low solution pH and of cupric oxide as the predominant species at the higher solution pH and higher temperature were also confirmed by both results.Work undertaken while at the School of Applied Chemistry, Western Australian Institute of Technology, W. A. 6102 (Australia). 相似文献
82.
Xianbao Wang Alexander Volodin Chris Van Haesendonck Nicolas Moreau Antonio Fonseca Janos B. Nagy 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):597-604
We report on the controllable growth of individual, uniform carbon nanotubes using thermal chemical vapor deposition (CVD). We performed a detailed study of the various factors influencing the growth of single nanotubes. In particular, we investigated the role played by catalyst layer thickness, catalyst dot size, deposition temperature, and gas source pressure on the growth process of straight, single nanotubes. Straight, individual nanotubes with uniform diameter can be obtained by decomposition of 0.1 mbar of acetylene at a temperature of 800 °C over a 5 nm thick nickel film that is patterned into square dots with dimensions below 500 nm. We compare the performance of thermal CVD and of plasma enhanced CVD for growing individual nanotubes. 相似文献
83.
The presented work provides baseline data on the existing airborne conditions in the Miyagi Museum of Art in Sendai, Japan, during the summer of 2000. The chemical composition, size and indoor and outdoor origin of the suspended particulate matter were identified using a number of advanced X-ray techniques, such as Electron Probe X-Ray Microanalysis (EPXMA) and Energy Dispersive X-Ray Fluorescence Analysis (EDXRF). Our results, to the best of our knowledge, represent the first detailed study of the chemical nature of the indoor particulate matter in a Japanese museum and, as such, may contribute to future improvements of the air quality inside museums and to the lasting conservation of works of art. 相似文献
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87.
Zhou MD Zhao J Li J Yue S Bao CN Mink J Zang SL Kühn FE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(1):158-166
Several Schiff-base ligands readily form complexes with methyltrioxorhenium(VII) (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom. The resulting complexes are stable at room temperature and can be handled and stored in air without problems. Due to the steric demands of the ligands they display distorted trigonal-bipyramidal structures in the solid state, as shown by X-ray crystallography, with the O(-) moiety binding to the Lewis acidic Re atom and the Re-bound methyl group being located either in cis or trans position to the Schiff base. In solution, however, the steric differences seem not to be maintained, as can be deduced from (17)O NMR spectroscopy. Furthermore, the Schiff-base ligands exchange with donor ligands. Nevertheless, the catalytic behaviour is influenced significantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition. A large excess of ligand, in contrast to the observations with aromatic N-donor ligands, is detrimental to the catalytic performance as it leads to catalyst decomposition. 相似文献
88.
Konstantin Khivantsev Carlos Garcia Vargas Jinshu Tian Libor Kovarik Nicholas R. Jaegers Janos Szanyi Yong Wang 《Angewandte Chemie (International ed. in English)》2021,60(1):391-398
We show for the first time that atomically dispersed Rh cations on ceria, prepared by a high‐temperature atom‐trapping synthesis, are the active species for the (CO+NO) reaction. This provides a direct link with the organometallic homogeneous RhI complexes capable of catalyzing the dry (CO+NO) reaction. The thermally stable Rh cations in 0.1 wt % Rh1/CeO2 achieve full NO conversion with a turn‐over‐frequency (TOF) of around 330 h?1 per Rh atom at 120 °C. Under dry conditions, the main product above 100 °C is N2 with N2O being the minor product. The presence of water promotes low‐temperature activity of 0.1 wt % Rh1/CeO2. In the wet stream, ammonia and nitrogen are the main products above 120 °C. The uniformity of Rh ions on the support, allows us to detect the intermediates of (CO+NO) reaction via IR measurements on Rh cations on zeolite and ceria. We also show that NH3 formation correlates with the water gas shift (WGS) activity of the material and detect the formation of Rh hydride species spectroscopically. 相似文献
89.
Ring opening metathesis polymerization (ROMP) of five- to eight-membered cyclic olefins: Computational,thermodynamic, and experimental approach 下载免费PDF全文
Antsar R. Hlil Janos Balogh Salvador Moncho Haw-Lih Su Robert Tuba Edward N. Brothers Mohammed Al-Hashimi Hassan S. Bazzi 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):3137-3145
Ring opening metathesis polymerization (ROMP) of a series of low-strain cyclic olefins and their hydroxyl derivatives using second generation Hoveyda–Grubbs catalyst has been investigated. Additionally, density functional theory (DFT) calculations were performed to evaluate the ring strain energies of the cyclic olefins and their hydroxyl derivatives, coupled with kinetic studies for the ROMP reactions. It was found that among different ring size monomers, Cy8 having a relatively moderate ring strain energy in comparison with the other cyclic olefins, exhibited the highest monomer conversion. The effect of temperature (0, 10, 15, and 25 °C) and monomer concentration (1 M; 2.5 M and 5 M for Cy5 ; and 1 M and 5 M for Cy7 ) for the cyclic olefins Cy5 and Cy7 were investigated. In general, the experimental results for the kinetic ROMP studies obtained using complex HG2 correlate really well with the DFT calculations determined for the ring strain energies of the cyclic olefins. For comparison, DFT calculations predicted the following trend for the ring strain energies Cy8 > Cy5 > Cy7 > Cy6 , and the polymerizations carried out experimentally followed the same trend in terms of monomer conversion, with the exception of Cy5 and Cy7 at lower concentrations, which followed this trend Cy8 > Cy7 > Cy5 > Cy6 . © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3137–3145 相似文献
90.
Yuri Park Godwin A. Ayoko Janos Kristof Erzsébet Horváth Ray L. Frost 《Journal of Thermal Analysis and Calorimetry》2012,110(3):1087-1093
In this study, mono- and di-alkyl cationic surfactants were used to prepare organoclays through ion exchange and the prepared organoclays were characterised by X-ray diffraction (XRD) and thermogravimetric analysis (TG). Larger basal spacings were observed in the interlayer of the organoclays intercalated with DDDMA than organoclays intercalated with DDTMA. The DTG curves identify the thermal stability of organoclays intercalated with two different types of surfactants (DDTMA and DDDMA) and the different arrangements of the surfactant molecules intercalated in the montmorillonite. Both organoclays intercalated with organic surfactant molecules proved to be thermally stable at high temperature. This study provides an understanding of the structure and properties of organoclays, which will enhance the potential applications of organoclays in environmental remediation. 相似文献