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1.
Tetramethyldisilane-1,2-diyl bridged Dicyclopentadienyl and Diindenyl Metal Dichlorides of the Group 4 Metals – Crystal Structure of Dicyclopentadienyl and diindenyl metal dichlorides of the type Cp′? SiMe2SiMe2? Cp′MCl2 (Cp′ = C5H4, M = Ti ( 1 ), Zr ( 2 ), Hf ( 3 ); Cp′ = C9H7, M = Zr ( 4 ), Hf ( 5 )) were synthesized and characterized by means of their 1H, 13C, 29Si-n.m.r., MS, and IR spectra. The crystal structure of 2 was determined. 相似文献
2.
Karl Hassler 《Monatshefte für Chemie / Chemical Monthly》1982,113(4):421-425
A simple preparation of the title compounds is achieved by reacting Na3P/K3P with stoichiometric mixtures of chlorotriphenylsilane and chlorotrimethylsilane.31P- and29Si-NMR-Data as well as Ir and Raman spectra of the compounds are reported. 相似文献
3.
Infrared andRaman vibrational spectra ofn-Si4Cl10,n-Si5Cl12,neo-Si5Cl12 and [(SiCl3)3Si]2 have been measured and assigned. A local symmetry force field has been developed to simulate vibrational spectra of all (noncyclic) perchlorosilanes Si
n
Cl2n+2 known today (n=2, 3, 4, 5, 8). The observed spectra are reproduced satisfactorily
Die Vibrationsspektren linearer und verzweigter PerchlorsilaneSi n Cl 2n+2 und deren Simulierung mittels eines lokalen Symmetrie-Kraftfeldes
Zusammenfassung Infrarot- undRaman-Spektren vonn-Si4Cl10,n-Si5Cl12,neo-Si5Cl12 und [(SiCl3)3Si]2 wurden aufgenommen und zugeordnet. Ein lokales Symmetrie-Kraftfeld zur Simulation der Spektren aller bisher bekannten (nicht cyclischen) Perchlorsilane Si n Cl2n+2 (n=2, 3, 4, 5, 8) wird angegeben. Die beobachteten Spektren werden zufriedenstellend reproduziert相似文献
4.
Two digestion-free methods for trace analysis of boron nitride based on graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma spectrometry optical emission (ETV-ICP-OES) using direct solid sampling have been developed and applied to the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Si, Ti and Zr in four boron nitride materials in concentration intervals of 1–23, 54–735, 0.05–21, 0.005–1.3, 1.6–112, 4.5–20, 0.03–1.8, 6–46, 38–170 and 0.4–2.3 μg g− 1, respectively. At optimized experimental conditions, with both methods, effective in-situ analyte/matrix separation was achieved and calibration could be performed using calibration curves measured with aqueous standard solutions. In solid sampling GFAAS, before sampling, the platform was covered with graphite powder and, for determination of Si, also the Pd/Mg(NO3)2 modifier was used. In the determination of all analyte elements by solid sampling ETV-ICP-OES, Freon R12 was added to argon carrier gas. For solid sampling GFAAS and ETV-ICP-OES, the achievable limits of detection were within 5 (Cu)–130 (Si) ng g− 1 and 8 (Cu)–200 (Si) ng g− 1, respectively. The results obtained by these two methods for four boron nitride materials of different purity grades are compared each with the other and with those obtained in analysis of digests by ICP-OES. The performance of the two solid sampling methods is compared and discussed. 相似文献
5.
Techniques for the direct analysis of powdered advanced ceramics provide an advantageous alternative to methods using wet digestion in sample preparation. The direct spectrochemical methods based on electrothermal vaporization (ETV-ICP-OES, solid-ETV-AAS, etc.) show a great similarity to the classical method of d. c. arc excitation. The calibration procedure is the major difficulty of all techniques applied for direct solid sample analysis, as there is a lack of suitable reference materials of ceramics. Consequently, it was necessary to verify various possibilities of preparation and application of model calibration samples. The results of such a calibration are compared with those using within-laboratory standards. 相似文献
6.
Hanne Thomassen Kolbj rn Hagen Reidar St levik
Karl Hassler
《Journal of Molecular Structure》1986,147(3-4):331-339The molecular structure of 1,1,2,2-tetrabromodisilane has been investigated using gas-phase electron diffraction data obtained at 110°C. At this temperature the molecules exist as a mixture of about equal parts (X = 0.5 ±0.2) of the two conformers with the H---Si---Si---H torsion angle equal to 180° (anti) or 60° (gauche). Assuming that the two conformers differ in their geometries only in the torsion angle φ, some of the important distance (ra) and angle () parameters are: r(Si---Si) = 2.349(19) Å, r(Si---Br) = 2.205(5) Å, r(Si---H) = 1.485 Å (assumed), Br---Si---Br = 110.1(1.6)°, Si---Si---Br = 107.1(1.2)° Si---Si---H = 108.6° (assumed). The error limits are 2σ. The observed conformational composition (Xanti = 0.5(0.2)) corresponds to an energy difference between the conformers of ΔE = E(gauche) — E(anti) = 0.5 ± 0.6 kcal mol−1, assuming ΔS = Rln2. 相似文献
7.
The conformers of the monohalocyclohexasilanes, Si6H11X (X=F, Cl, Br or I) and the haloundecamethylcyclohexasilanes, Si6Me11X (X=F, Cl, Br or I) are investigated by DFT calculations employing the B3LYP density functional and 6‐31+G* basis sets for elements up to the third row, and SDD basis sets for heavier elements. Five minima are found for Si6H11X—the axial and equatorial chair conformers, with the substituent X either in an axial or equatorial position—and another three twisted structures. The equatorial chair conformer is the global minimum for the X=Cl, Br and I, the axial chair for X=F. The barrier for the ring inversion is ~13 kJ mol?1 for all four compounds. Five minima closely related to those of Si6H11X are found for Si6Me11X. Again, the equatorial chair is the global minimum for X=Cl, Br and I, and the axial chair for X=F. Additionally, two symmetrical boat conformers are found as local minima on the potential energy surfaces for X=F, Cl and Br, but not for X=I. The barrier for the ring inversion is ~14–16 kJ mol?1 for all compounds. The conformational equilibria for Si6Me11X in toluene solution are investigated using temperature dependent Raman spectroscopy. The wavenumber range of the stretching vibrations of the heavy atoms X and Si from 270–370 cm?1 is analyzed. Using the van′t Hoff relationship, the enthalpy differences between axial and equatorial chair conformers (Hax?Heq.) are 1.1 kJ mol?1 for X=F, and 1.8 to 2.8 kJ mol?1 for X=Cl, Br and I. Due to rapid interconversion, only a single Raman band originating from the “averaged” twist and boat conformers could be observed. Generally, reasonable agreement between the calculated relative energies and the experimentally determined values is found. 相似文献
8.
Graphite arc emission spectrometry has become possible as a result of the invention of novel types of optical spectrometers
with Echelle-optics and semiconductor array detectors, and by the application of electronically controlled, high current arc
generators. An optimization of the excitation parameters to boron carbide analysis is reported here, measuring background
corrected line intensities that were integrated for the time of total evaporation of 5 mg boron carbide sample with or without
added chemical modifiers. The following set of experimental conditions were compared with respect of analytical sensitivity
and precision: (A) no modifier, Ar + O2 (20%), 16 A; (B) sample + graphite powder (1 + 1), Ar + O2 (20%), 16 A; (C) sample + CaF2 (1 + 1), Ar, 25 A; (D) sample + CaF2 + graphite powder (1 + 1 + 1), Ar, 25 A. The graphite powder modifier resulted in improved precision in general, and the
CaF2 was effective as a plasma ionization buffer and fluorinating agent. The best compromise was found under conditions B, when
oxygen was present in the discharge atmosphere. This is likely due to the stepwise conversion of the boron carbide matrix
to the more volatile boron oxide. Under conditions B, detection limits in the ranges of 0.3–9 μg g−1 for Al, Ca, Cr, Cu, Fe, Mg, Mn and Si and that of 18–38 μg g−1 for Ti, W, and Zr were attained. Average RSDs of 10.2 and 9.7% were found, respectively, without and with internal referencing
to boron. 相似文献
9.
Sandra J. Atkinson Heather E. Robertson Margit Hölbling Wolf-Walther du Mont Cristina Mitrofan Karl Hassler Sarah L. Masters 《Structural chemistry》2013,24(3):851-857
The gas-phase molecular structures of a series of halogen-substituted disilanes [X3SiSiMe3 (X = H, F, Cl and Br)], 1,1,1-trimethyldisilane (H3SiSiMe3), 1,1,1-trifluoro-2,2,2-trimethyldisilane (F3SiSiMe3), 1,1,1-trichloro-2,2,2-trimethyldisilane (Cl3SiSiMe3) and 1,1,1-tribromo-2,2,2-trimethyldisilane (Br3SiSiMe3), have been determined in the gas phase by electron diffraction. Ab initio calculations at the HF and MP2 level were used to support the experimental investigation using the SARACEN method. All of the investigated structures were determined to adopt a staggered structure with C 3v symmetry. The effect of substitution on the Si–Si bond and the Si–Si–X bond angle was investigated and these results were compared to results obtained from a recent study of halogen-substituted disilanes [X3SiSiXMe2 (X = F, Cl, Br and I)] to consider the effect of the methyl groups on the substituted disilanes. 相似文献
10.
1,1-Difluorodecamethyl- and 1,1,4,4-tetrafluorooctamethylcyclohexasilane were synthesized by the reaction of LiF with the corresponding trifluoromethanesulfonic derivatives and were characterized by spectroscopic methods, mainly by modern NMR techniques. The stability of the fluorinated cyclosilanes decreases with an increase of fluorine substituents. This seems to be the reason for the instability of perfluorinated cyclosilanes. 相似文献