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1.
Raymond K. Sheline Harald Mahnke 《Angewandte Chemie (International ed. in English)》1975,14(5):314-321
It has been proven qualitatively by a number of authors using variable temperature NMR experiments that most metal carbonyl complexes are nonrigid. A quantitative determination of the ligand exchange frequency ve is often achieved by a line shape analysis or by measurement of the transverse relaxation time T2 using the Carr-Purcell method. In the case of a “very fast” exchange, however, both methods prove unsuccessful. It is shown in this study that a simultaneous fit of IR or Raman spectra on the one hand and NMR spectra on the other can make possible the determination of ve for the “very fast” exchange and can also facilitate the determination of ve in “slow” and “medium” exchange cases considerably. The ligand exchange frequency thus found for Fe(CO)5, 1.1 × 1010s?1, is unexpectedly high; comparison with variable temperature measurements on solid Fe(CO)5, yields similar energy barriers. A mechanism of exchange closely related to the “Berry mechanism” is proposed. Finally the consequences of this surprisingly large ligand exchange rate are discussed with respect to IR band assignments for molecular “fragments” M(CO)x (where x=coordination number, and M is a transition metal, typically lanthanoid or actinoid). 相似文献
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3.
H. -E. Mahnke 《Hyperfine Interactions》1987,34(1-4):47-59
Nuclear moments contribute valuable information to nuclear structure studies of nuclei under extreme conditions, such as nuclei at high angular momentum or far from stability. While the magnetic moment is sensitive to the nature of the participating nucleons (neutron or proton) the quadrupole moment is a direct measure for nuclear deformation. 相似文献
4.
Laser-induced autofluorescences show a strong intensity distortion for endogenous NADH in the UV and synthesized markers in the NIR range because of tissue optics. Rescaling taking into account bio-optical methods results in the chromophore profile in the observed tissue region. For the in vivo tests an experimental NIR imager was used. NIR fluorescence of the entire body of small animals can be imaged. For first experiments an undifferentiated superficial tumor of mouse thigh was used. Corrections that are due to tissue optics must take care of a more strongly scattering of the light in the NIR range in comparison to the UV fluorescence such as in optical biopsy. For example, the diameter of the fluorescent volume is apparently larger for the same reason. Therefore, the established rescaling from the UV adapted to the NIR range is important for the interpretation fluorescence pictures in biomedicine. 相似文献
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M. Sc. Lisa K. Mahnke Dr. Aleksandar Kondinski M. Sc. Ulrike Warzok Prof. Dr. Christian Näther Dr. Jan van Leusen Prof. Dr. Christoph A. Schalley Dr. Kirill Yu. Monakhov Prof. Dr. Paul Kögerler Prof. Dr. Wolfgang Bensch 《Angewandte Chemie (International ed. in English)》2018,57(11):2972-2975
A water‐soluble derivative of the polyoxovanadate {V15E6O42} (E=semimetal) archetype enables the study of cluster shell rearrangements driven by supramolecular interactions. A reaction unique to E=Sb, induced exclusively by ligand metathesis in peripheral [Ni(ethylenediamine)3]2+ counterions, results in the formation of the metastable α1* configurational isomer of the {V14Sb8O42} cluster type. Contrary to all other polyoxovanadate shell architectures, this isomer comprises an inward‐oriented vanadyl group and is ca. 50 and 12 kJ mol?1 higher in energy than the previously isolated α and β isomers, respectively. We discuss this unexpected reaction in light of supramolecular Sb?O???V and Sb?O???Sb contacts manifested in {V14Sb8O42}2 dimers detected in the solid state. ESI MS experiments confirm the stability of these dimers also in solution and in the gas phase. DFT calculations indicate that other, as of yet elusive isomers of {V14Sb8}, might be accessible as well. 相似文献
8.
Jens Mahnke Andreas Zanin Wolf-Walther du
Mont Frank Ruthe Peter G. Jones 《无机化学与普通化学杂志》1998,624(9):1447-1454
The New P -Phosphanylphosphaalkene 1-Bis(trimethylsilyl)methylidene-2,2-diisopropyldiphosphane: First Reactions at its P=C and P–P Bonds (Me3Si)2C=PCl ( 1 ) reacts with the trichlorosilylphosphanes RR′PSiCl3 (R and R′ = t-Bu or i-Pr) providing the new P-dialkylphosphanylphosphaalkenes (Me3Si)2C=P–P-i-Pr2 ( 2 ) and (Me3Si)2C=P–P(t-Bu)(i-Pr) ( 3 ) as well as the known (Me3Si)2C=P–P-t-Bu2 ( 4 ). The P=C double bond of 2 can be protected reversibly by a [2 + 4]-cycloaddition with cyclopentadiene resulting in the formation of a P-phosphanyl-phosphanorbornene derivative 5 . The [2 + 4]-cycloaddition of 2 with 2,3-dimethylbutadiene provides the cyclic diphosphane 6 . Reactions of 2 with sulfur and selenium were followed by 31P and 77Se nmr: Chalcogen insertion into the P–P bond leads to the products (Me3Si)2C=P–X–P-i-Pr2 9 a (X = S) and 9 b (X = Se). Subsequent σ3λ3 → σ4λ5 oxidation steps of 9 a with S and of 9 b with Se lead to compounds (Me3Si)2C=P–X–P(=X)-i-Pr2 10 a (X = S) and 10 b (X = Se), which contain phosphinic acid functions with the phosphaalkene moieties attached to S or Se. 10 a and 10 b were not isolated in a pure state. However, trapping 10 b from an enriched solution by [2 + 4]-cycloaddition with cyclopentadiene allowed the isolation of the P-diseleno-phosphinato-phosphanorbornene 12 . The constitution of new compounds 2 , 3 , 5 , 6 and 12 was confirmed by elemental analyses, nmr and mass spectra. The structures of cycloadducts 5 and 6 were determined by X-ray diffraction analysis. 相似文献
9.
We report on a 3.3 μm laser/optical parametric oscillator system with 4.7 mJ pulse energy for laser ultrasound measurements of carbon-fiber-reinforced materials. The OPO was pumped by a compact diode-pumped Nd:YAG master-oscillator power-amplifier system with two amplifier stages. First results of laser ultrasound measurements are presented. 相似文献
10.
O. Häusser D. Ward T. K. Alexander H. R. Andrews W. J. L. Buyers H.-E. Mahnke J. F. Sharpey-Schafer P. Skensved M. L. Swanson P. Taras 《Hyperfine Interactions》1980,8(1-3):271-281
We have examined the temperture dependence of the efg for GdGd above the Curie point. Using anI
=10+ isomer in144Gd as a probe nucleus, we find a weakT
3/2 dependence withB=(1.5±0.4) 10–5 K–3/2. The absolute value of the efg at 332 K was measured by Coulomb excitation of 2+ states in156, 158, 160Gd, yielding |eq(332 K)|=(3.43±0.14) 1017 V/cm2. A possible small deviation from theT
3/2 temperature dependence of the efg for ferromagnetic Gd is discussed. 相似文献