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1.
Dwayne R. Senn 《Journal of polymer science. Part A, Polymer chemistry》1994,32(6):1175-1183
Random copoly(p-phenylene sulfide sulfone/ketone)s (PPSS/K) are prepared in high yield by the polycondensation of sodium hydrosulfide (NaSH) with bis(4-chlorophenyl) sulfone (BCPS) and 4,4′-dichlorobenzophenone (DCBP). The polymerization is conducted between 200–220°C, depending on the composition of the copolymer, and in the presence of water without any detrimental effects to the molecular weight. The copolymers with sulfone/ketone mole ratios (S : K) > 25 : 75 are amorphous, while the copolymers with S : K ratios ≤ 25 : 75 are crystalline. These materials form tough, creaseable films and exhibit a linear increase in the glass transition temperature with increasing sulfone content. Sulfuric acid solutions of the copolymers are dark orange to red and display an increasing λmax in the uv-visible spectra as the S:K ratio of the copolymers decreases. © 1994 John Wiley & Sons, Inc. 相似文献
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Walter Senn 《manuscripta mathematica》1991,71(1):45-65
We consider a variational problem with an integrandF:R
n
×R×R
n
→R that isZ-periodic in the firstn+1 variables and satisfies certain growth-conditions. By a recent result of Moser, there exist for every α∈R
n
minimal solutionsu:R
n
→R minimising ƒF(x, u(x), u
x
(x)) dx with respect to compactly supported variations ofu and such that sup |u(x)-αx|<∞. Given such a minimal solutionu we define the average action
(whereB
r
is ther-ball around 0∈R
n
) and show thatM(α) is indeed independent of the minimal solutionu satisfying sup |u(x)-αx|<∞. We prove that this average actionM(α) is strictly convex in α.
相似文献
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Susann Paul W. Bernd Schweizer Graham Rugg Hans Martin Senn Ryan Gilmour 《Tetrahedron》2013,69(27-28):5647-5659
Herein, we report the synthesis and X-ray structural analysis of a collection of fluorinated metal N-heterocyclic carbenes (Ag, Au, Pd, Rh, Ir) and their precursor salts. The common structural feature of these species is a flanking fluoroethyl group, which is either freely rotating or embedded within a bicyclic framework. Solid state analysis confirmed a gauche conformational preference in all cases with the fluorine adopting a syn clinal arrangement (?[NCCF]~60°) with respect to the triazolium nitrogen at the vicinal position of the NHC. A density functional theory analysis was employed to quantify these effects and evaluate the influence of electronic modulation of the carbenic carbon [(CN+); neutral carbene (C:); metal-bound carbene (CM)], on the relative gauche/anti preference, thus highlighting the potential of this conformational phenomenon as a useful molecular design strategy for controlling the topology of organometallic complexes. 相似文献
8.
Christoph M. Hendrich Sebastian Senn Lea Haas Marvin T. Hoffmann Dr. Ute Zschieschang Luca C. Greiner Dr. Frank Rominger Dr. Matthias Rudolph Dr. Hagen Klauk Prof. Dr. Andreas Dreuw Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(59):14778-14784
Herein, we describe a gold-catalyzed cascade cyclization of Boc-protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6-endo-dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc-protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π-extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields. Two bidirectional approaches under the optimized conditions were successful, and the resulting π-extended molecules were tested as organic semiconductors in organic thin-film transistors. 相似文献
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The Feynman path integral Monte Carlo approach has been coupled to the gauge including atomic orbital formalism in order to analyse the absolute magnetic shieldings of the benzene nuclei under the conditions of thermal equilibrium. The Hamiltonian employed in the derivation of ensemble averaged NMR quantities is of the Hartree-Fock type. The basis set used is of 6–31G quality. The spatial delocalization of the atoms leads to a deshielding of both types of benzene nuclei relative to the shieldings experienced at the minimum of the potential energy surface. This deshielding has to be traced back to bond length elongations in thermal equilibrium. The influence of the nuclear fluctuations on the NMR parameters of benzene is quantum driven up to temperatures of 400 K; classical fluctuations are of minor importance in this low-temperature window. 相似文献