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31.
32.
A. Amato C. Geibel F. N. Gygax R. H. Heffner E. Knetsch D. E. MacLaughlin C. Schank A. Schenck F. Steglich M. Weber 《Zeitschrift für Physik B Condensed Matter》1992,86(2):159-160
Positive-muon spin rotation (
+ SR) measurements have been carried out in the new heavy-fermion superconductors UM2Al3, M=Ni and Pd. In UNi2Al3 the observed
+ frequencies in zero applied field indicate commensurate antiferromagnetic (AF) ordering of U moments 0.1
B
/U atom. These moments coexist with superconductivity and have the highest values observed in an AF heavy-fermion superconductor. The absence of well-defined frequencies in zero-field
+ SR in the AF state of UPd2Al3 suggests symmetric
+ stopping sites. In this system
+ SR linewidths belowT
c
yield a preliminary value of 8000 Å for the London penetration depth. 相似文献
33.
F. N. Gygax A. Hintermann W. Rüegg A. Schenck W. Studer A. J. van der Wal L. Schlapbach 《Hyperfine Interactions》1983,15(1-4):533-536
The + Knight shift in Platinum has been measured between 20 K and 785 K. It shows a strong temperature dependence and scales with the magnetic bulk susceptibility. A temperature independent contribution of +53±15 ppm and a d-electron induced hyperfine field per unpaired d-electron per atom of B
hfd
a
=–5.03 kG(±8.5%) are obtained. The + Knight shift in PdH0.70, PdH0.75 and PdH0.86 shows no dependence on temperature between 20 K and RT and increases from K=–(8±3) ppm for x=0.70 to K =+(6.5±3) ppm K=+(6.5±3) ppm for x=0.86, in good agreement with proton Knight shift measurements. 相似文献
34.
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37.
A Note on Methods for the Transformation of 1,2-Dicarboxylic Acids into α, β-Unsaturated Monocarboxylic Acids. A model study using the Diels-Alder adduct of maleic anhydride and butadiene (see scheme 3) exemplifies the conversion of the succinic acid type of structure into α, β-unsaturated carboxylic acids via two complementary fragmentations of 3,6-dioxo-perhydro-1,2-oxazine derivatives. 相似文献
38.
Johann W. Faigle Hans Blattner Hansruedi Glatt Hans-Peter Kriemler Hans Mory Angelo Storni Tammo Winkler Franz Oesch 《Helvetica chimica acta》1987,70(5):1296-1301
Reaction of the tricyclic psychotropic drug opipramol ( 1 ) with an excess of HNO2 affords a product mixture mutagenic for Salmonella typhimurium. The main product is a tetracyclic furoxan 2 (yield ca. 80%), resulting from nitrosation at C(10) and C(11) of 1 . Compound 2 is not mutagenic. The essential mutagen is a nitroarene 3 formed via contraction of the central ring of 1 , and nitrosation at C(2). Its yield is extremely low (<0.1%). Nitroarenes have previously not been encountered as mutagenic products of the interaction of drugs with nitrite. 相似文献
39.
W. Studer F. N. Gygax A. Hintermann W. Rüegg A. Schenck A. J. van der Wal 《Hyperfine Interactions》1984,17(1-4):359-363
During the past much effort has been devoted to a systematic study of the muon Knight shiftK
in metallic environments and its implications on the local electronic structure of hydrogen in metals [1]. These measurements in simple metals were essentially all carried out in polycrystalline samples at room temperature. The present measurements in Cd in polycrystalline and single crystal samples cover a temperature range between 20 K and the melting point of this strongly anisotropic metal (hcp crystal structure,c/a ratio 1.89 — idealc/a ratio 1.63). These measurements add qualitatively new and interesting aspects and insights on the screening of a light hydrogen isotope in a metal as well as on certain properties of the host material itself. The outstanding features of the muon Knight shift in Cd are: (i) a strong intrinsic temperature dependence with an increase ofK
of more than 100% between 20 K and the melting point (T=593 K), (ii) an anomaly at 110 K in the form of a singularity in the isotropic part ofK
which is interpreted as a band structure effect, (iii) an anisotropic Knight shift contribution fitting the expressionK(T,)=K
iso(T)+K
ax(T) * (3 · cos2
–1)/2, where both, the isotropic and the axial contribution ofK
, are strongly temperature dependent. 相似文献
40.
Substituent Effects on NMR Spectra of Pentafulvenes. 13C, 13C-NMR Coupling Constants (1J(C, C)) 1H- and 13C-NMR spectra of 6-monosubstituted pentafulvenes 1 – 8 have been analysed, and 1J(C, C) coupling constants have been determined from ID-inadequate spectra of 13C satellites. It turns out that 13C,13C coupling constants of the ring C-atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron-donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ+ and 1J(C,C) values are obtained. 相似文献