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81.
K. Jellinek und J. Czerwinski 《Fresenius' Journal of Analytical Chemistry》1924,64(5-6):230-231
Ohne Zusammenfassung 相似文献
82.
H. Czerwinski F. Smend D. Schaupp M. Schumacher A. H. Millhouse H. Schenk-Strauss 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(2):183-189
Using monochromatized synchrotron radiation with variable photon energyE i=33.94keV...34.54keV, Resonant Raman Scattering (RRS) by free Xenon atoms (B 1s=34.566keV) was investigated. The measured double-differential RRS cross sections are in excellent agreement with those calculated in the non-relativistic dipole approximation, modified by some relativistic corrections, and including the interference corrections predicted by Tulkki and Åberg. Within the experimental error of 5 % the RRS cross section is found to be independent of the scattering angle and of the polarization of the incident photons. 相似文献
83.
Investigations on free radical copolymerization of 1-vinyl naphthalene (1-VNph, monomerM
2) with styrene (St), methyl methacrylate (MMA) and acrylonitrile (AN) (monomersm
1) in bulk at 60°C with AIBN as initiator are presented. Relative reactivity ratios were calculated by the Kelen-Tüdös method yielding:r
st=0.70 ±0.23 andr
1–VNph=2.02 ±0.40 for system St/1-VNph;r
MMA=0.32 ±0.10 andr
1–VNph=0.57 ±0.07 for system MMA/1-VNph andr
AN=0.11 ±0.03 andr
1–VNph=0.45 ±0.09 for system AN/1-VNph.Q, e values for 1-VNph according to Alfrey, Price scheme were calculated toQ
1–VNph=1.02,e
1–VNph=–0.62. 相似文献
84.
Postawa Z Czerwinski B Winograd N Garrison BJ 《The journal of physical chemistry. B》2005,109(24):11973-11979
Molecular dynamics computer simulations have been employed to model the bombardment of Ag{111} covered with three layers of C6H6 by 15 keV Ga and C60 projectiles. The study is aimed toward examining the mechanism by which molecules are desorbed from surfaces by energetic cluster ion beams and toward elucidating the differences between cluster bombardment and atom bombardment. The results show that the impact of the cluster on the benzene-covered surface leads to molecular desorption during the formation of a mesoscopic scale impact crater via a catapulting mechanism. Because of the high yield of C6H6 with both Ga and C60, the yield enhancement is observed to be consistent with related experimental observations. Specific energy and angle distributions are shown to be associated with the catapult mechanism. 相似文献
85.
Trinuclear transition-metal complexes such as Re(3)X(9) (X = Cl, Br, I), with their uniquely featured structure among metal halides, have posed intriguing questions related to multicenter electron delocalization for several decades. Here we report a comprehensive study of the technetium halide clusters [Tc(3)(μ-X)(3)X(6)](0/1-/2-) (X = F, Cl, Br, I), isomorphous with their rhenium congeners, predicted from density functional theory calculations. The chemical bonding and aromaticity in these clusters are analyzed using the recently developed adaptive natural density partitioning method, which indicates that only [Tc(3)X(9)](2-) clusters exhibit aromatic character, stemming from a d-orbital-based π bond delocalized over the three metal centers. We also show that standard methods founded on the nucleus-independent chemical shift concept incorrectly predict the neutral Tc(3)X(9) clusters to be aromatic. 相似文献
86.
J. W. Plaue G. L. Klunder I. D. Hutcheon K. R. Czerwinski 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):551-555
Near-infrared (NIR) reflectance spectroscopy was examined as a potential tool for the determination of forensic signatures indicative of the chemical process history of uranium oxides. The ability to determine the process history of nuclear materials is a desired, but underdeveloped, area of technical nuclear forensics. Application of the NIR technique potentially offers a quick and non-destructive tool to serve this need; however, few data have been published on the compounds of interest. The viability of NIR was investigated through the analysis of a combination of laboratory-derived and real-world uranium precipitates and oxides. A set of reference uranium materials was synthesized in the laboratory using the commonly encountered aqueous precipitation reactions for uranium ore concentration and chemical separation processes (ammonia, hydrogen peroxide, sodium hydroxide, ammonium carbonate, and magnesia). NIR spectra were taken on a range of samples heat treated in air between 85 and 750 °C. X-ray diffraction patterns were also obtained to complement the NIR analysis with crystal phase information. Similar analyses were performed using a set of real-world samples, with process information obtained from the literature, to provide a comparison between materials synthesized in the laboratory and samples representative of industrial processes. 相似文献
87.
Edward Mausolf Erik Johnstone Frederic Poineau Suzanne Nguyen Steven Jones Thomas Hartmann Edgar Buck Kenneth Czerwinski 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1315-1321
Amorphous TcO2 and NH4TcO4 solubilized into 12 M HCl will spontaneously convert to hexachlorotechnetate (TcCl6 2?). This process is accelerated upon heating but species lower than Tc(IV) are not generated by this action. TcCl6 2? is kinetically unstable with regards to formation in solutions of low concentrations of HCl and will spontaneously convert back to soluble and insoluble forms of Tc(IV) in water. TcCl6 2? in 12 M HCl placed in contact with the reducing metal Zn at elevated temperatures (90 °C) forms a black precipitate that contains amorphous Tc metal, TcO2, and oxy-chlorides of Tc. Powder X-ray diffraction indicates the presence of Tc metal after thermal treatment where X-ray absorption fine structure spectroscopy indicates the presence of hexagonal Tc metal and amorphous TcO2 in the precipitate after rinsing with 12 HCl but before thermal treatment. The resulting solution contains a mixture of Tc chlorides and oxy-chlorides following reduction where TcCl6 2? is completely consumed resulting primarily in Tc2OCl10 4? dominating the UV–visible spectra. Reducing the solution volume and reconstituting the products into 12 M HCl while boiling the mixed solution (>24 h) will slowly convert all soluble Tc back to TcCl6 2?. Expanding on previous efforts made in this laboratory to recover Tc metal from aqueous solution, we investigate its synthesis when Tc(IV) and Tc(VII) in 12 M HCl is placed in contact with the reducing metal (i.e., Zn) at elevated temperatures. 相似文献
88.
Prof. Dr. Sjoerd Harder Dominik Naglav Dr. Christian Ruspic Prof. Dr. Claudia Wickleder Dr. Matthias Adlung Dr. Wilfried Hermes Dr. Matthias Eul Prof. Dr. Rainer Pöttgen Dr. Daniel B. Rego Prof. Dr. Frederic Poineau Prof. Dr. Kenneth R. Czerwinski Prof. Dr. Rolfe H. Herber Prof. Dr. Israel Nowik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(37):12272-12280
The superbulky deca‐aryleuropocene [Eu(CpBIG)2], CpBIG=(4‐nBu‐C6H4)5‐cyclopentadienyl, was prepared by reaction of [Eu(dmat)2(thf)2], DMAT=2‐Me2N‐α‐Me3Si‐benzyl, with two equivalents of CpBIGH. Recrystallizyation from cold hexane gave the product with a surprisingly bright and efficient orange emission (45 % quantum yield). The crystal structure is isomorphic to those of [M(CpBIG)2] (M=Sm, Yb, Ca, Ba) and shows the typical distortions that arise from CpBIG???CpBIG attraction as well as excessively large displacement parameter for the heavy Eu atom (Ueq=0.075). In order to gain information on the true oxidation state of the central metal in superbulky metallocenes [M(CpBIG)2] (M=Sm, Eu, Yb), several physical analyses have been applied. Temperature‐dependent magnetic susceptibility data of [Yb(CpBIG)2] show diamagnetism, indicating stable divalent ytterbium. Temperature‐dependent 151Eu Mössbauer effect spectroscopic examination of [Eu(CpBIG)2] was examined over the temperature range 93–215 K and the hyperfine and dynamical properties of the EuII species are discussed in detail. The mean square amplitude of vibration of the Eu atom as a function of temperature was determined and compared to the value extracted from the single‐crystal X‐ray data at 203 K. The large difference in these two values was ascribed to the presence of static disorder and/or the presence of low‐frequency torsional and librational modes in [Eu(CpBIG)2]. X‐ray absorbance near edge spectroscopy (XANES) showed that all three [Ln(CpBIG)2] (Ln=Sm, Eu, Yb) compounds are divalent. The XANES white‐line spectra are at 8.3, 7.3, and 7.8 eV, for Sm, Eu, and Yb, respectively, lower than the Ln2O3 standards. No XANES temperature dependence was found from room temperature to 100 K. XANES also showed that the [Ln(CpBIG)2] complexes had less trivalent impurity than a [EuI2(thf)x] standard. The complex [Eu(CpBIG)2] shows already at room temperature strong orange photoluminescence (quantum yield: 45 %): excitation at 412 nm (24270 cm?1) gives a symmetrical single band in the emission spectrum at 606 nm (νmax=16495 cm?1, FWHM: 2090 cm?1, Stokes‐shift: 2140 cm?1), which is assigned to a 4f65d1→4f7 transition of EuII. These remarkable values compare well to those for EuII‐doped ionic host lattices and are likely caused by the rigidity of the [Eu(CpBIG)2] complex. Sharp emission signals, typical for EuIII, are not visible. 相似文献
89.
Poineau F Forster PM Todorova TK Gagliardi L Sattelberger AP Czerwinski KR 《Dalton transactions (Cambridge, England : 2003)》2012,41(10):2869-2872
The [Cs((2 + x))][H(3)O((1 - x))]Tc(2)Br(8)·4.6H(2)O (x = 0.221) salt has been synthesized and characterized by single crystal XRD. Multi-configurational quantum chemical calculations on Tc(2)X(8)(n-) (X = Cl, Br; n = 2, 3) have been performed and indicate the π component in the Tc-Tc bond to be stronger for n = 3. 相似文献
90.
F Poineau EV Johnstone PM Forster L Ma AP Sattelberger KR Czerwinski 《Inorganic chemistry》2012,51(17):9563-9570
The cesium salts of [Tc(2)X(8)](3-) (X = Cl, Br), the reduction product of (n-Bu(4)N)[TcOCl(4)] with (n-Bu(4)N)BH(4) in THF, and the product obtained from reaction of Tc(2)(O(2)CCH(3))(4)Cl(2) with HCl(g) at 300 °C have been characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. For the [Tc(2)X(8)](3-) anions, the Tc-Tc separations found by EXAFS spectroscopy (2.12(2) ? for both X = Cl and Br) are in excellent agreement with those found by single-crystal X-ray diffraction (SCXRD) measurements (2.117[4] ? for X = Cl and 2.1265(1) ? for X = Br). The Tc-Tc separation found by EXAFS in these anions is slightly shorter than those found in the [Tc(2)X(8)](2-) anions (2.16(2) ? for X = Cl and Br). Spectroscopic and SCXRD characterization of the reduction product of (n-Bu(4)N)[TcOCl(4)] with (n-Bu(4)N)BH(4) are consistent with the presence of dinuclear species that are related to the [Tc(2)Cl(8)](n-) (n = 2, 3) anions. From these results, a new preparation of (n-Bu(4)N)(2)[Tc(2)Cl(8)] was developed. Finally, EXAFS characterization of the product obtained from reaction of Tc(2)(O(2)CCH(3))(4)Cl(2) with HCl(g) at 300 °C indicates the presence of amorphous α-TcCl(3). The Tc-Tc separation (i.e., 2.46(2) ?) measured in this compound is consistent with the presence of Tc═Tc double bonds in the [Tc(3)](9+) core. 相似文献