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排序方式: 共有104条查询结果,搜索用时 31 毫秒
1.
Gilles Gosselin Jean Louis Imbach Leroy B. Townsend Raymond P. Panzica 《Journal of heterocyclic chemistry》1979,16(6):1185-1191
Ribosylation of the trimethylsilyl derivative ( 1b ) of imidazole-2-thione ( 1a ) using either stannic chloride or silver perchlorate as catalyst resulted in the formation of the acylated derivatives of 1-(β-D-ribofuranosyl)imidazole-2-thione ( 3c ) and 1,3-di-(β-D-ribofuranosyl)imidazole-2-thione ( 4c ) with the latter predominating ( 4c:3c , ca. 2:1 ). The diribosylated nucleoside 4c was shown to be the N,N-disubstituted product rather than the N,S-disubstituted product by 1H nmr and 13C nmr spectroscopy. Employment of the iodine-catalyzed fusion procedure reversed the aforementioned product ratios and provided the monoriboside 3c in excellent yield. When the trimethylsilyl derivative ( 5b ) of 2-methylthioimidazole ( 5a ) was reacted with 2,3,5-tri-O-benzoyl-D-ribofuranosyl bromide ( 2d ) in acetonitrile, the major product was 1,3-di-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-imidazole-2-thione ( 4b ). The formation of 4b in this reaction is thought to arise via the Hilbert-Johnson mechanism. 相似文献
2.
3.
This work describes the synthesis of certain nucleoside synthons which are necessary in order to obtain oligoxylonucleotides. The utilization of a non-symmetrically substituted xyloside substituted at the 2-position permits one to obtain, in satisfactory yields, the described nucleoside which is conveniently protected. All of the compounds described have been fully characterized using the usual analytical methods. 相似文献
4.
Rydberg spectra are shown to provide a spectral fingerprint that is sensitive to molecular structure in unique ways. The concepts are demonstrated using a set of isomeric fluorophenols and a sequence of aliphatic diamines. In the fluorophenols, the sensitivity extends to the placement of a single hydrogen atom and can be traced to the molecular charge distributions associated with the locations of atoms and functional groups with respect to the charge center. Experiments on tetramethyl diamines demonstrate that the structural sensitivity encompasses the extended molecular structure, including parts of the molecule that are remote from the ionization center. This global structure sensitivity makes Rydberg fingerprint spectroscopy uniquely suited to characterize structures of large-scale molecular systems. 相似文献
5.
Chong Han Sean M. Kelly Theresa Cravillion Scott J. Savage Tina Nguyen Francis Gosselin 《Tetrahedron》2019,75(32):4351-4357
An efficient synthesis of PI3K inhibitor GDC-0077, featuring two consecutive Cu-catalyzed CN coupling reactions, is reported. The described synthetic route involves a chemoselective Ullmann-type coupling of a chiral difluoromethyl-substituted oxazolidinone, a Cu-catalyzed N-arylation of l-alanine with high stereochemical integrity, and a high-yielding final amide bond formation step to produce GDC-0077 in >99.5 area % HPLC purity. 相似文献
6.
A versatile and practical approach for synthesizing azabicyclo[X.Y.0]alkane amino acids of different ring sizes from a common diaminodicarboxylate precursor has been developed as a means for mimicking different peptide conformations. (2S,9S)-1-tert-Butyl 10-benzyl 5-oxo-2-[N-(PhF)amino] 9-[N-(BOC)amino]dec-4-enedioate (18) was first prepared in 83% yield by the Horner-Wadsworth-Emmons olefination of N-(PhF)aspartate beta-aldehyde 8 with pyroglutamate-derived beta-keto phosphonate 12 (PhF = 9-phenylfluoren-9-yl). The practicality of this approach for making azabicyclo[X.Y.0]alkane amino acids was then illustrated by the first synthesis of enantiopure quinolizidin-2-one amino acid 6 in seven steps and 40% overall yield from L-pyroglutamic acid. Hydrogenation of delta-keto alpha,omega-diaminosebacate 18, followed by lactam cyclization and protection, gave quinolizidin-2-one amino acid 6 as a single diastereomer. The versatility of this approach was next demonstrated by the synthesis of both ring-fusion isomers of pyrroloazepin-2-one amino acid 6 in 11 steps and 13% overall yield from pyroglutamic acid. Hydride reduction of 18, followed by methanesulfonate displacement, gave 5-alkylproline 22. Protective group manipulations, lactam cyclization, and removal of the ester group afforded readily separable pyrroloazepinone amino acids (7S)- and (7R)-7 in a 1:2 diastereomeric ratio. By introducing two new azabicycloalkane amino acids using our olefination approach, we have expanded the diversity of these important heterocycles for studying the conformational requirements for peptide biological activity. 相似文献
7.
A
cha Ali-Bey Hasna Fatiha Loukil Gilles Gosselin Andr Mathieu Abderrezzak Mesli 《Journal of heterocyclic chemistry》1982,19(3):617-624
Hydrolysis of the imine function of a series of Schiff bases derived from pyrrole-2-carboxaldehyde and substituted anilines (X = H, p-OCH3, p-OC2H5, p-CH3, p-Cl, p-Br, m-CN, m-NO2, p-NO2) was studied in all of the pH ranges. The hydrolysis curves log kabs (mn?1) = f(pH) were established in buffered aqueous methanol by polarography or amperometry. The shapes of the curves obtained for pH > 5 indicates that N-pyrrolylmethylene-2 anilines hydrolyse according to the same mechanism as N-benzylidene anilines. The particular stability of these products for pH < 5 permits one to obtain complete hydrolysis curves in acid media. A very good Hammett correlation (kobs = + 1,73) has been established from the maxima which appear for strong acidity. This stability is interpreted as due to the specific electron-donating effect of the pyrrole nucleus. The influence of the structural parameter X on the morphology of the curves log kabs = f(pH) and on the hydrolysis mechanism of the imine function is discussed in all of the pH ranges. 相似文献
8.
Valérie Fargeas Myriam Baalouch Jerôme Baffreau Pascal Gosselin Chantal Barthomeuf 《Tetrahedron》2004,60(45):10359-10364
A simple and efficient methodology to introduce an 1,3-diketone motif from various aldehyde precursors in three steps with good overall yields is described using β-ketosulphone 7 as masked equivalent of acetone. 相似文献
9.
Dr. Meaghan M. Deegan Michael R. Dworzak Aeri J. Gosselin Kyle J. Korman Prof. Dr. Eric D. Bloch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(14):4531-4547
Molecules with permanent porosity in the solid state have been studied for decades. Porosity in these systems is governed by intrinsic pore space, as in cages or macrocycles, and extrinsic void space, created through loose, intermolecular solid-state packing. The development of permanently porous molecular materials, especially cages with organic or metal–organic composition, has seen increased interest over the past decade, and as such, incredibly high surface areas have been reported for these solids. Despite this, examples of these materials being explored for gas storage applications are relatively limited. This minireview outlines existing molecular systems that have been investigated for gas storage and highlights strategies that have been used to understand adsorption mechanisms in porous molecular materials. 相似文献
10.
Pascal Gosselin Serge Masson Monique Saquet André Thuillier 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):103-104
Abstract A new synthesis of dithioesters, starting from phenylisothiocyanate is described (scheme I) and this method is convenient for the preparation of β-olefinic dithioesters (e. g. 1, scheme II). 相似文献