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1.
The perovskite-related phase Ca3Nb2O8, when grown as single crystals from a calcium vanadate flux, incorporates a small amount of vanadium from the flux to form the composition Ca3Nb2−xVxO8 with x=0.025. The crystals have pseudo-cubic symmetry with a=6×ac(perovskite). The actual symmetry is rhombohedral, space group R3, with ah=16.910(1) Å, ch=41.500(2) Å. The structure was solved using a combination of single-crystal methods together with constrained refinements of powder X-ray and neutron powder data. The unit-cell composition is [Ca138□24]A [Ca42Nb117V3]B[O480□6], with vacancies in both the anion sites and A-cation sites. The Ca and Nb atoms are fully ordered in the B-sites such that (001) layers containing only Nb-centered octahedra alternate with layers containing both Nb-centered and Ca-centered octahedra. At the origin B-site, ordered oxygen vacancies result in the octahedron being transformed to a tetrahedron, which, in the single crystals, is occupied by vanadium. The structure displays a new type of octahedral tilt system in which 3×3×3 blocks of (a+a+a+) tilts are periodically twinned on the pseudo-cubic {1 0 0}c planes. 相似文献
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Tania Dr. Sevan D. Houston Lachlan Sharp-Bucknall Tiffany B. Poynder Dr. Mohammad Albayer Prof. Jason L. Dutton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15863-15866
PhI(OTf)2 has been used for the past 30 years as a strong I(III) oxidant for organic and inorganic transformations. It has been reported to be generated in situ from the reactions of either PhI(OAc)2 or PhI=O with two equivalents of trimethylsilyl trifluoromethanesulfonate (TMS-OTf). In this report it is shown that neither of these reactions generate a solution with spectroscopic data consistent with PhI(OTf)2, with supporting theoretical calculations, and thus this compound should not be invoked as the species acting as the oxidant for transformations that have been associated with its use. 相似文献
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Dr. Christina I. Schroeder Dr. Lachlan D. Rash Xavier Vila‐Farrés Dr. K. Johan Rosengren Dr. Mehdi Mobli Prof. Glenn F. King Prof. Paul F. Alewood Prof. David J. Craik Dr. Thomas Durek 《Angewandte Chemie (International ed. in English)》2014,53(4):1017-1020
Mambalgins are a novel class of snake venom components that exert potent analgesic effects mediated through the inhibition of acid‐sensing ion channels (ASICs). The 57‐residue polypeptide mambalgin‐2 (Ma‐2) was synthesized by using a combination of solid‐phase peptide synthesis and native chemical ligation. The structure of the synthetic toxin, determined using homonuclear NMR, revealed an unusual three‐finger toxin fold reminiscent of functionally unrelated snake toxins. Electrophysiological analysis of Ma‐2 on wild‐type and mutant ASIC1a receptors allowed us to identify α‐helix 5, which borders on the functionally critical acidic pocket of the channel, as a major part of the Ma‐2 binding site. This region is also crucial for the interaction of ASIC1a with the spider toxin PcTx1, thus suggesting that the binding sites for these toxins substantially overlap. This work lays the foundation for structure–activity relationship (SAR) studies and further development of this promising analgesic peptide. 相似文献
4.
Emily Kerr David J. Hayne Lachlan C. Soulsby Joseph C. Bawden Steven J. Blom Egan H. Doeven Luke C. Henderson Conor F. Hogan Paul S. Francis 《Chemical science》2022,13(2):469
The classic and most widely used co-reactant electrochemiluminescence (ECL) reaction of tris(2,2′-bipyridine)ruthenium(ii) ([Ru(bpy)3]2+) and tri-n-propylamine is enhanced by an order of magnitude by fac-[Ir(sppy)3]3− (where sppy = 5′-sulfo-2-phenylpyridinato-C2,N), through a novel ‘redox mediator’ pathway. Moreover, the concomitant green emission of [Ir(sppy)3]3−* enables internal standardisation of the co-reactant ECL of [Ru(bpy)3]2+. This can be applied using a digital camera as the photodetector by exploiting the ratio of R and B values of the RGB colour data, providing superior sensitivity and precision for the development of low-cost, portable ECL-based analytical devices.A water-soluble Ir(iii) complex is shown to enhance the ‘remote’ mechanism of the most widely used co-reactant ECL reaction of tris(2,2′-bipyridine)ruthenium(ii) with tripropylamine. 相似文献
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Castillo-Martínez E Bieringer M Shafi SP Cranswick LM Alario-Franco MÁ 《Journal of the American Chemical Society》2011,133(22):8552-8563
A novel ScVO(3) perovskite phase has been synthesized at 8 GPa and 1073 K from the cation-disordered bixbyite-type ScVO(3). The new perovskite has orthorhombic symmetry at room temperature, space group Pnma, and lattice parameters a = 5.4006(2) ?, b = 7.5011(2) ?, and c = 5.0706(1) ? with Sc(3+) and V(3+) ions fully ordered on the A and B sites of the perovskite cell. The vanadium oxygen octahedra [V-O(6)] display cooperative Jahn-Teller (JT) type distortions, with predominance of the tetragonal Q(3) over the orthorhombic Q(2) JT modes. The orthorhombic perovskite shows Arrhenius-type electrical conductivity and undergoes a transition to triclinic symmetry space group P-1 close to 90 K. Below 60 K, the magnetic moments of the 4 nonequivalent vanadium ions undergo magnetic long-range ordering, resulting in a magnetic superstructure of the perovskite cell with propagation vector (0.5, 0, 0.5). The magnetic moments are confined to the xz plane and establish a close to zigzag antiferromagnetic mode. 相似文献
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We give a new construction of the holonomy groupoid of a regular foliation in terms of a partial connection on a diffeological principal bundle of germs of transverse parametrisations, which may be viewed as a systematisation of Winkelnkemper’s original construction using ideas from gauge theory. We extend these ideas to construct a novel holonomy groupoid for any foliated bundle, which we prove sits at the top of a hierarchy of diffeological jet holonomy groupoids associated with the foliated bundle. This shows that while the Winkelnkemper holonomy groupoid is the smallest Lie groupoid that integrates a foliation, it is far from the smallest diffeological groupoid that does so.
相似文献10.