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81.
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Daniel Bruck Abraham Minsky Arie Dagan Mordecai Rabinovitz 《Tetrahedron letters》1981,22(36):3545-3548
Acenaphthoquinone () undergoes ppotonation to afford the respective double protonation product . The proton and carbon NMR parameters of are discussed. 相似文献
83.
Eshdat L Berger H Hopf H Rabinovitz M 《Journal of the American Chemical Society》2002,124(15):3822-3823
Cross-conjugated enediynes cannot follow the Bergman cycloaromatization as it involves a methylenediyne moiety with only five pi e(-), insufficient for aromatization. Under reductive conditions the cyclization is made feasible by generating a product with a Hückel number of pi electrons. We illustrate this principle and demonstrate for the first time an anionic cyclization of a cross-conjugated enediyne that results in formation of a five-membered ring. 9-(3-Phenyl-1-phenylethynylprop-2-ynylidene)-9H-fluorene (3) was reduced by potassium to yield the dianion of 9-(3,4-diphenylcyclopenta-2,4-dienylidene)-9H-fluorene (4(2-)), which contains a cyclopentadienyl fragment, and oxidation with iodine yielded the unstable fulvalene 4. 相似文献
84.
Eshdat L Hoffman RE Fechtenkötter A Müllen K Rabinovitz M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(8):1844-1851
Hexa(4-n-dodecylbiphenylyl)benzene (HDBB) was reduced by a series of alkali metals in THF under high vacuum. Three reduction states were identified by NMR spectroscopy, namely the dianion, tetraanion and hexaanion. The NMR spectra of HDBB(6-) revealed a remarkable distortion of symmetry, which is interpreted by adoption of a twisted conformation of the central benzene ring and a slow rotation of the inner phenylene rings of the biphenyl units. Due to the surprising thermal stability of the hexaanion, a dynamic NMR investigation revealed the pseudorotation of the twisted conformation and the phenylene rotation mentioned above. 相似文献
85.
Aprahamian I Bodwell GJ Fleming JJ Manning GP Mannion MR Merner BL Sheradsky T Vermeij RJ Rabinovitz M 《Journal of the American Chemical Society》2004,126(21):6765-6775
The reduction of a series of [n](2,7)pyrenophanes (n = 7-10) with lithium or potassium metal shows that the strain in the system, controlled by the length of the tether, determines the nature of the reduction products. The reduction of [7](2,7)pyrenophane (2) and [2]metacyclo[2](2,7)pyrenophane (3) leads to reductive dimerization followed by novel intramolecular sigma-bond formation as a means of escaping strained anti-aromaticity. [8](2,7)Pyrenophane (4) affords only reductive dimerization, and no two-electron reduction is observed. The reduction of [9](2,7) pyrenophane (5) and [10](2,7)pyrenophane (6) leads to reductive dimerization, followed by the formation of a dianionic anti-aromatic species, which eventually cleaves the solvent, THF-d(8). The similarity between the reduction of the latter systems and the reduction of pyrene (1) is discussed. 相似文献
86.
Aprahamian I Bodwell GJ Fleming JJ Manning GP Mannion MR Sheradsky T Vermeij RJ Rabinovitz M 《Journal of the American Chemical Society》2003,125(7):1720-1721
The two-electron reduction of strained pyrenes ([7](2,7)pyrenophanes) with lithium metal leads to the formation of a new sigma-bond as a means to "escape" strained antiaromaticity. 相似文献
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