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101.
102.
Zamani E.D. Cele Sphelele C. Sosibo Pher G. Andersson Hendrik G. Kruger Glenn E.M. Maguire Thavendran Govender 《Tetrahedron: Asymmetry》2013,24(4):191-195
The use of TIQ-N,N′-dioxide ligands in asymmetric C–C bond forming reactions is described. In the Michael addition of cyclohexane-1,3-dione and malonates to β,γ-unsaturated α-ketoesters, excellent yields (up to 93%) and moderate to good enantioselectivities (70–89% ee) were obtained. The catalytic hetero-ene reaction of 2-methoxypropene with phenylglyoxal gave the ene product in excellent yield (95%) with moderate enantioselectivity (77% ee). The catalyst system performed well at temperatures ranging from 0 to 30 °C and relatively low catalyst loading (0.2–5 mol %) with dichloromethane being the preferred solvent for all reactions. 相似文献
103.
Declan P. Gavin Aoife Foley Thomas S. Moody U.B. Rao Khandavilli Simon E. Lawrence Pat ONeill Anita R. Maguire 《Tetrahedron: Asymmetry》2017,28(4):577-585
Hydrolase-catalysed dynamic kinetic resolutions of chroman-2-ol and 3-methyl chroman-2-ol can be effected with up to 88% conversion and 92% ee through the use of organic solvents. Extension to the resolution of the tolterodine precursor 1 proved more challenging. The presence of the remote phenyl substituent had a significant impact on the resolution and it was not possible to achieve high enantioselectivity together with efficient conversion from the focussed panel of enzymes screened. 相似文献
104.
Dash BP Satapathy R Gaillard ER Norton KM Maguire JA Chug N Hosmane NS 《Inorganic chemistry》2011,50(12):5485-5493
The ability of ortho-, meta- and para-carboranes to enhance the emission intensity has been compared. For this purpose a series of carborane-appended 1,3,5-triphenylbenzene (TB) and 1,3,5- tris(biphenyl-4-yl)benzene (TBB) containing three ortho-, meta- and para-carborane clusters directly attached to the conjugated cores have been synthesized employing Suzuki, Heck, and trimerization reactions. The incorporation of the icosahedral carboranes was associated with a red shift in the UV absorption spectrum of up to 13 nm as well as enhancements of the emission intensities of up to 154%. The presence of ortho-carboranes showed the maximum red shift in the UV spectrum whereas the maximum enhancement of the emission intensity was observed in the presence of meta-carborane clusters. The order of π-conjugation extension is found to be ortho > meta ≈ para. A comparative thermal analysis indicated o-carborane-appended trimers to be the most thermally stable in the series. Proton NMR spectra of reported carborane-appended trimers indicated that ortho- and meta-carborane cages have benzenelike characteristics. 相似文献
105.
Elidrisi I Negin S Bhatt PV Govender T Kruger HG Gokel GW Maguire GE 《Organic & biomolecular chemistry》2011,9(12):4498-4506
Five new cavitands were prepared that have four pendant n-undecyl chains and "headgroups" connected by 2-carbon spacers. The headgroups were ~OCH(2)CONH-Ala-OCH(3), 1; ~OCH(2)CONH-Phe-OCH(3), 2; ~OCH(2)CONH-Ala-OH, 3; ~OCH(2)CONH-Phe-OH, 4; and ~OCH(2)CONHCH(2)CH(2)-thyminyl, 5. Pore formation by each cavitand was studied by use of the planar bilayer conductance experiment. All five compounds were found to form pores in asolectin bialyer membranes. Compounds 1-3 behaved in a generally similar fashion and exhibited open-close dynamics. Compounds 4 and 5 formed pores more rapidly, were more dynamic, and led more quickly to membrane rupture. Differences in the ion transport activity are rationalized in terms of structure and aggregate cavitand assemblies. 相似文献
106.
Mohamed S. Altaib Per I. Arvidsson Thavendran Govender Glenn E. M. Maguire Maya Makatini Oluseye K. Onajole Hendrik G. Kruger 《Magnetic resonance in chemistry : MRC》2010,48(6):435-442
The synthesis and NMR elucidation of two novel pentacycloundecane (PCU)‐based peptides are reported. The PCU cage amino acids were synthesised as racemates and the incorporation of the cage amino acid with (S)‐natural amino acids produced diastereomeric peptides. The diastereomeric ‘cage’ peptides were separated using preparative HPLC and the NMR elucidation of these PCU containing peptides are reported for the first time. The 1H and 13C NMR spectra showed series of overlapping signals of the cage skeleton and that of the peptide, making it extremely difficult to resolve the structure using one‐dimensional NMR techniques only. The use of two‐dimensional NMR techniques proved to be a highly effective tool in overcoming this problem. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
107.
Grant A. Boyle Thavendran Govender Hendrik G. Kruger Glenn E. M. Maguire Tricia Naicker 《Structural chemistry》2008,19(3):429-434
The complete NMR elucidation of three novel pentacycloundecane (PCU)-derived ligands is reported. 2D NMR techniques are used
to overcome the problem of major overlapping of methine signals on the cage skeleton. The compounds were synthesized as potential
ligands to be used in asymmetric catalysis. They represent the first instance where aromatic moieties have been attached directly
to the cage skeleton using lithiation techniques. The X-ray crystal structure of one of the ligands was obtained. The X-ray
structure was helpful in determining the potential NOESY interactions within the set of molecules. For the other ligands a
high level Density Functional Theory (DFT) optimization was performed [B3LYP/6-31+g(d)] to visualize possible NOE interactions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
108.
109.
Fiber optic hydrophones typically use a long sensor fiber wrapped around an air-filled mandrel to achieve high responsivity. Minimum mandrel diameter is determined by fiber reliability considerations. A miniature hydrophone, with diameter of about a third that of previous hydrophones, is reported. Such a hydrophone has applications for very thin towed arrays. Small diameter fiber with high strength Bragg gratings written through the coating are key enablers. 相似文献
110.
Zhu Yinghuai Koh Cheng Yan Chong Siow Hwei A. Emi Monalisa Winata John A. Maguire 《Journal of organometallic chemistry》2007,692(20):4244-4250
Iridium(I) salicylaldiminato-cyclooctadiene complexes, Ir(-o-O-C6H4-CHN-R)(cod) (R = CH2Ph (1), Ph (2); cod = 1,5-cyclooctadiene), have been prepared, characterized and used as catalysts for arylborylation via C-H activation. With 1 as a catalyst, isolated yields of up to 91% has been achieved for the borylation of benzene by bis(pinacolato)diboron in the presence of tetra-2-pyridinylpyrazine and an ionic liquid. The catalytic system could be recycled for at least three times without loss of activity. 相似文献