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71.
Mesleh MF Lee S Veglia G Thiriot DS Marassi FM Opella SJ 《Journal of the American Chemical Society》2003,125(29):8928-8935
Dipolar waves describe the structure and topology of helices in membrane proteins. The fit of sinusoids with the 3.6 residues per turn period of ideal alpha-helices to experimental measurements of dipolar couplings as a function of residue number makes it possible to simultaneously identify the residues in the helices, detect kinks or curvature in the helices, and determine the absolute rotations and orientations of helices in completely aligned bilayer samples and relative rotations and orientations of helices in a common molecular frame in weakly aligned micelle samples. Since as much as 80% of the structured residues in a membrane protein are in helices, the analysis of dipolar waves provides a significant step toward structure determination of helical membrane proteins by NMR spectroscopy. 相似文献
72.
N-Phenylnitrones react with α,β-acetylenic sulfones to give ultimately 3-acylindoles via unstable 4-sulfonylsubstituted 2,3-dihydroisoxazoles. In one case, a minor pathway is also operative leading to a different kind of indole derivative. Mechanistic possibilities are discussed. 相似文献
73.
Mascioni A Karim C Zamoon J Thomas DD Veglia G 《Journal of the American Chemical Society》2002,124(32):9392-9393
Solid-state NMR spectroscopy, in conjunction with rigid body molecular dynamics calculations, shows that monomeric phospholamban in lipid bilayers has two distinct helical domains, with an interhelical angle within 60-100 degrees, ruling out the possibility of a continuous alpha-helical structure for this protein. 相似文献
74.
Giovanni Vidari Gianluigi Lanfranchi Patrizia Sartori Stefano Serra 《Tetrahedron: Asymmetry》1995,6(12):2977-2990
The enantioselective synthesis of the right-hand lactone moiety 5 of saponaceolide B, 2, is described. The mean graph profiles of 5 do not match the characteristic patterns of differential cytotoxicity of saponaceolides A, 1, and B, 2, in the NCI human disease-oriented tumor screening panel, pointing out the need of the entire saponaceolide structure for maintaining the specificity and potency of the antitumor activity. En route to 5 several useful chiral building blocks, such as compounds 6, 10, 19, 27, and 28 were prepared. 相似文献
75.
Dr. Sheng Chu Dr. Shizhao Fan Dr. Yongjie Wang Dr. David Rossouw Yichen Wang Prof. Gianluigi A. Botton Prof. Zetian Mi 《Angewandte Chemie (International ed. in English)》2016,55(46):14262-14266
Syngas, the mixture of CO and H2, is a key feedstock to produce methanol and liquid fuels in industry, yet limited success has been made to develop clean syngas production using renewable solar energy. We demonstrated that syngas with a benchmark turnover number of 1330 and a desirable CO/H2 ratio of 1:2 could be attained from photoelectrochemical CO2 and H2O reduction in an aqueous medium by exploiting the synergistic co‐catalytic effect between Cu and ZnO. The CO/H2 ratio in the syngas products was tuned in a large range between 2:1 and 1:4 with a total unity Faradaic efficiency. Moreover, a high Faradaic efficiency of 70 % for CO was acheived at underpotential of 180 mV, which is the lowest potential ever reported in an aqueous photoelectrochemical cell. It was found that the combination of Cu and ZnO offered complementary chemical properties that lead to special reaction channels not seen in Cu, or ZnO alone. 相似文献
76.
Behling LA Hartsel SC Lewis DE DiSpirito AA Choi DW Masterson LR Veglia G Gallagher WH 《Journal of the American Chemical Society》2008,130(38):12604-12605
Methanobactin (mb) is a small copper-binding peptide produced by methanotrophic bacteria and is intimately involved in both their copper metabolism and their role in the global carbon cycle. The structure for methanobactin comprises seven amino acids plus two chromophoric residues that appear unique to methanobactin. In a previously published structure, both chromophoric residues contain a thiocarbonyl attached to a hydroxyimidazolate ring. In addition, one is attached to a pyrrolidine ring, while the other is attached to an isopropyl ester. A published X-ray determined structure for methanobactin shows these two chromophoric groups forming an N2S2 binding site for a single Cu(I) ion with a distorted tetrahedral geometry. In this report we show that NMR, mass spectrometry, and chemical data reveal a chemical structure that is significantly different than the previously published one. Specifically, the 1H and 13C NMR assignments are inconsistent with an N-terminal isopropyl ester and point instead to a 3-methylbutanoyl group. Our data also indicate that oxazolone rings instead of hydroxyimidazolate rings form the core of the two chromophoric residues. Because these rings are directly involved in the binding of Cu(I) and other metals by methanobactin and are likely involved in the many chemical activities displayed by methanobactin, their correct identity is central to developing an accurate and detailed understanding of methanobactin's many chemical and biological roles. For example, the oxazolone rings make methanobactin structurally more similar to other bacterially produced bactins and siderophores and suggest pathways for its biosynthesis. 相似文献
77.
Sabrina Giofr Roberto Sala Egle Maria Beccalli Leonardo Lo Presti Gianluigi Broggini 《Helvetica chimica acta》2019,102(7)
A procedure for the iodoamination of unfunctionalized olefins tethered to a tosyl‐protected NH‐group has been developed. The combined use of KI and H2O2 in aqueous medium was effective for the preparation of iodomethyl‐substituted nitrogen‐containing heterocycles. The selective exo‐trig iodocyclization provided 1,2‐bifunctional 5‐, 6‐, and 7‐membered cyclic skeletons. 相似文献
78.
Dr. Marcin Górecki Dr. Filippo Lipparini Dr. Gianluigi Albano Dr. Tamás Jávorfi Dr. Rohanah Hussain Dr. Giuliano Siligardi Prof. Gennaro Pescitelli Prof. Lorenzo Di Bari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202103632
Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm2 with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recorded with a bench-top instrument (1 cm2 area). This is due to the anisotropic part of the ECD (ACD), which averages to zero in solution or on a large number of randomly oriented crystallites, but can otherwise be extremely large. Two-way singular value decomposition (SVD) analysis, through experimental and simulated TDDFT spectra, disclosed that the measured and theoretical principal components are in line with each other. This finding demonstrates that the observed isotropic ss-ECD spectrum is governed by the anisotropy of locally oriented crystals. It also introduces a new quality for ss-ECD measurements and opens a new future for probing and mapping chiral materials in the solid state such as active pharmaceutical ingredients (APIs). 相似文献
79.
Tullio Pilati Gianluigi Casalone 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):495-496
(5S,9S,17S)‐17‐Hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐dione, C18H26O3, (II), and (5R,9R,17S)‐17‐hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐dione, C18H26O3, (III), are equimolecular products of the FeII‐induced transposition of 10β‐hydroperoxy‐17β‐hydroxyestr‐4‐en‐3‐one, (I). With respect to reagent molecules, the configuration at C9 is retained for (II) while it is inverted in (III). The conformations of the five‐ and six‐membered rings are compared. 相似文献
80.
Polarized absorption spectra of single crystals of Ca2PO4Cl doped with V(V) ions have been measured at liquid-helium temperature. Only one broad and very intense band is observed from 30000 to 45000 cm?1. In Td symmetry it is assigned as a charge-transfer transition 1T2 ← 1A1. Under theTd→ D2d site perturbation, the excited state 1T2 is split into 1B2 and 1E. 相似文献