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21.
M. Audit P. Demerseman N. Goasdoue N. Platzer 《Magnetic resonance in chemistry : MRC》1983,21(11):698-705
The relative abilities of weak Lewis bases to complex binuclear lanthanide(III)—silver(I) reagents were checked by inter- or intra- molecular competitions. Preferential complexation at one particular site was shown to be determined mainly by the occurrence of well localized π electrons, by the relief of strain effects or by the lack of steric hindrance. In benzofuran and methoxybenzene derivatives oxygen never interacts directly with the silver reagent and plays a role mainly through electronic effects. Unlike oxygen, sulphur in benzo[b]thiophene is the preferred site of complexation with the silver reagent. On complexation with binuclear shift reagents (lanthanide = Eu, Pr, Yb) the 1H NMR shifts were shown to result from several mechanisms. Better insight into the precise location of the reagent is obtained in 13C NMR by the use of the binuclear relaxation reagent Ag(tfa)-Gd(fod)3. 相似文献
22.
F. Gobert S. Combrisson N. Platzer M. Ricard 《Magnetic resonance in chemistry : MRC》1976,8(6):293-298
The peri effect induced by the phenyl group has been studied in the anthracene series by means of 1H and 13C n.m.r. The chemical shifts of overcrowded protons can be explained by a combination of magnetic anisotropy and steric effects. Steric contributions amount to c. 25% of the phenyl induced shift at the peri position. Amongst published ring-current theories, only the model of Johnson and Bovey is capable of describing correctly the shielding region of the phenyl group. The unexpected shieldings and deshieldings, observed by 13C n.m.r. in the case of very hindered derivatives, is probably due to distortions of the anthracene skeleton. 相似文献
23.
24.
Hybrid systems with both discrete and continuous dynamics are an important model for real-world cyber-physical systems. The key challenge is to ensure their correct functioning w.r.t. safety requirements. Promising techniques to ensure safety seem to be model-driven engineering to develop hybrid systems in a well-defined and traceable manner, and formal verification to prove their correctness. Their combination forms the vision of verification-driven engineering. Often, hybrid systems are rather complex in that they require expertise from many domains (e. g., robotics, control systems, computer science, software engineering, and mechanical engineering). Moreover, despite the remarkable progress in automating formal verification of hybrid systems, the construction of proofs of complex systems often requires nontrivial human guidance, since hybrid systems verification tools solve undecidable problems. It is, thus, not uncommon for development and verification teams to consist of many players with diverse expertise. This paper introduces a verification-driven engineering toolset that extends our previous work on hybrid and arithmetic verification with tools for (1) graphical (UML) and textual modeling of hybrid systems, (2) exchanging and comparing models and proofs, and (3) managing verification tasks. This toolset makes it easier to tackle large-scale verification tasks. 相似文献
25.
The current status of surface hyperfine fields measured with NMR, Mössbauer spectroscopy and PAC is reviewed. Emphasis is put on experiments with well-characterized, free surfaces and on results on surface electric field gradients. Applications to detection of probe sites and diffusion phenomena are discussed.This article is dedicated to the memory of our late colleague Dr. Wolfgang Keppner 相似文献
26.
The structural analysis of carbamates derived from 2-(α-furyl)benzaldoximes and 2-(α-furyl)benzyl alcohols was carried out by 1H and 13C NMR spectroscopy. The conjugative and steric effects of alkyl substituents introduced on the benzene rings were found to modify the relative orientation of the aromatic and furan rings. The existence of a close relationship between the stereochemistry of the studied compounds and their anticholinesterase activity has been proposed. 相似文献
27.
R. Wesche W. Keppner T. Klas R. Platzer J. Voigt G. Schatz 《Hyperfine Interactions》1987,34(1-4):573-576
The PAC method was applied to study interface compound formation in thin In/Sb film couples. Above annealing temperatures of 220 K, kept for 10 min, the compound InSb is growing out of the interface. The average thickness of InSb increases with the square root of time at the beginning, indicating a diffusion controlled start of interface compound growth. 相似文献
28.
The 13C NMR spectra of iridium complexes of 1,5-cyclooctadiene are reported and discussed. For compounds containing β-diketonato ligands, a correlation is found between the ethylenic carbon chemical shifts and the Swain and Lupton and values of the substituents of the β-diketonato ligand. The relationship is satisfactorily explained by considering the Dewar, Chatt and Duncanson model of bonding. Tentative interpretation of the observed chemical shifts of the other carbons is presented. 相似文献
29.
Dr. Víctor Mariñas Benedikt Platzer Jorge Labella Dr. Fabrizio Caroleo Prof. Sara Nardis Prof. Roberto Paolesse Prof. Dirk M. Guldi Prof. Tomás Torres 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201552
Porphyrinoids are considered perfect candidates for their incorporation into electron donor–acceptor (D–A) arrays due to their remarkable optoelectronic properties and low reorganization energies. For the first time, a series of subphthalocyanine (SubPc) and corrole (Cor) were covalently connected through a short-range linkage. SubPc axial substitution strategies were employed, which allowed the synthesis of the target molecules in decent yields. In this context, a qualitative synthetic approach was performed to reverse the expected direction of the different electronic events. Consequently, in-depth absorption, fluorescence, and electrochemical assays enabled the study of electronic and photophysical properties. Charge separation was observed in cases of electron-donating Cors, whereas a quantitative energy transfer from the Cor to the SubPc was detected in the case of electron accepting Cors. 相似文献
30.
G. Schatz X. L. Ding R. Fink G. Krausch B. Luckscheiter R. Platzer J. Voigt U. Wöhrmann R. Wesche 《Hyperfine Interactions》1990,60(1-4):975-989
Applications of hyperfine-interaction techniques, like NMR, PAC and Mößbauer spectroscopy, to well-characterized surfaces are discussed and the present knowledge of surface hyperfine fields is reviewed. Measurements of nuclear spin relaxation permit to extract the local density of electron states at the Fermi level of adsorbed alkali atoms. From the observed electric-field-gradient properties surface probe sites and diffusion processes can be inferred; the experimentally determined magnetic hyperfine fields give access to the electron-spin behaviour at magnetic surfaces. 相似文献