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101.
Chevella Durgaiah Mameda Naresh Macharla Arun Kumar Peraka Swamy Marri Mahender Reddy Kodumuri Srujana 《合成通讯》2016,46(13):1133-1144
A simple, efficient, and environmentally benign protocol for the synthesis of vicinal iodohydrins and iodoesters from olefins using NH4I and Oxone in CH3CN/H2O (1:1) and dimethylformamide (DMF) / dimethylacetamide (DMA), respectively, without employing a catalyst at room temperature is described. Regio- and stereoselective iodohydroxylation and iodoesterification of various olefins with anti fashion, following Markonikov’s rule, was achieved and the corresponding products were obtained in good to excellent yields. In addition, 1,2-disubstituted olefins afforded excellent diastereoselectivity. 相似文献
102.
De Novo Synthesis of Furanose Sugars: Catalytic Asymmetric Synthesis of Apiose and Apiose‐Containing Oligosaccharides 下载免费PDF全文
Mijin Kim Soyeong Kang Prof. Young Ho Rhee 《Angewandte Chemie (International ed. in English)》2016,55(33):9733-9737
A de novo synthetic method towards apiose, a structurally unusual furanose, is reported. The key feature is sequential metal catalysis consisting of the palladium‐catalyzed asymmetric intermolecular hydroalkoxylation of an alkoxyallene and subsequent ring‐closing metathesis (RCM). This strategy enabled the efficient synthesis of various apiose‐containing disaccharides and a unique convergent synthesis of trisaccharides. 相似文献
103.
104.
Gagnepain J Castet F Quideau S 《Angewandte Chemie (International ed. in English)》2007,46(9):1533-1535
105.
Fustero S Chiva G Piera J Volonterio A Zanda M González J Ramallal AM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(30):8530-8542
Aza-Michael additions of alpha-amino esters to fluorinated acceptors take place in a highly stereoselective manner, to give partially modified Psi[NHCH2]retropeptides incorporating a hydrolytically stable trifluoroalanine mimic. The reaction mechanism has been investigated experimentally and theoretically, in order to explain the effect of the trifluoromethyl group on the reactivity and the origins of the experimentally observed stereocontrol. The reaction is a two-step process, involving a tandem aza-Michael addition followed by a stereoselective hydrogen transfer. Both steps are base-catalyzed. The high level of stereocontrol is the result of a combination of electrostatic interactions and steric effects. 相似文献
106.
Mechanism and diastereoselectivity of sulfur ylide promoted aziridination reactions were studied by density functional theory with inclusion of solvent effects through the continuum solvation model. The general reaction pathway was modeled for the addition of substituted sulfur ylides (Me(2)S(+)CH(-)R) to an aldimine ((E)-methyl ethylidenecarbamate, MeHC=NCO(2)Me). The nature of the substituents on the ylidic carbon atom substantially affects the reaction profile. The stabilized (R=COMe) and semistabilized (R=Ph) ylides follow a cisoid addition mode leading to trans aziridines via anti betaine intermediates. The simplest model ylide (unstabilized, R=H) underwent cisoid addition in a similar fashion. In the case of stabilized ylides product diastereoselectivity is controlled by the barriers of the elimination step leading to the 2,3-trans aziridine, whereas it is decided in the addition step in the case of semistabilized ylides. The importance of steric and electronic factors in diastereoselective addition (2 and 5) and elimination (5) transition states was established. Comparison of results obtained with the gas-phase optimized geometries and with the fully optimized solvent-phase geometries reveals that the inclusion of solvent effects does not bring about any dramatic changes in the reaction profiles for all three kinds of ylides. In particular, diastereoselectivity for both kinds of ylides was found to be nearly the same in both these approaches. 相似文献
107.
Jiménez-González L García-Muñoz S Alvarez-Corral M Muñoz-Dorado M Rodríguez-García I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(2):557-568
The condensation of 2,3-dihydrobenzoxasilepins with aromatic aldehydes in the presence of boron trifluoride to form 2,3-dihydrobenzofurans shows a level of diastereoselection which is a function of the electronic nature of the aldehyde and the polarity of the solvent. The study of the mechanism of the reaction demonstrated that it proceeds through a ring-opened allylfluorosilane, which is stable enough to be isolated and characterized. 相似文献
108.
Shadpour E. Mallakpour Abdol‐Reza Hajipour Ali‐Reza Mahdavian Sepideh Khoee 《Journal of polymer science. Part A, Polymer chemistry》1999,37(8):1211-1219
The reaction of N‐phthaloyl‐L ‐leucine acid chloride (1) with isoeugenol (2) was carried out in chloroform, and novel optically active isoeugenol ester derivative 3 as a chiral monomer was obtained in high yield. Compound 3 was characterized by 1H‐NMR, IR, and mass and elemental analysis and then was used for the preparation of model compound 5 and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione, PhTD (4), was allowed to react with compound 3. The reaction is very fast and gives only one diastereomer of 5 via Diels–Alder and ene pathways in quantitative yield. In order to explain this diastereoselectivity, a nonconcerted two‐step mechanism involving benzylic cation (BC) and aziridinium (AI) have been proposed for the Diels–Alder and ene reactions, respectively. The polymerization reactions of novel monomer 3 with bis(triazolinedione)s [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (8) and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (9)] were performed in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and gave novel optically active polymers 10 and 11 via repetitive Diels–Alder–ene polyaddition reactions. These polymers have inherent viscosities in a range about 0.18–0.22 dL/g. Some physical properties and structural characterizations of these new polymers have been studied and are reported. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1211–1219, 1999 相似文献
109.
Shaojin Chen Zhaohai Ge Qiang Jia Kun‐Peng Wang Li‐Hua Gan Zhi‐Qiang Hu 《化学:亚洲杂志》2019,14(9):1462-1466
A general and efficient synthetic methodology for the preparation of enantio‐ and diastereopure [6]‐, and [7]helicenes is developed. Commercially available chiral binaphthanols are utilized to generate the arylene‐vinylene precursors, which undergo helical folding via photocyclization to give enantio‐ and diastereopure [6]‐, and [7]helicenes. These optically pure helicenes could be easily obtained via silica gel column chromatography without the use of expensive HPLC or chiral resolution reagents. The configurations and structures of these helicenes are confirmed by CD spectra and X‐ray crystallographic analysis. This work provides a new method for preparation of enantiopure helicenes. 相似文献
110.