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排序方式: 共有131条查询结果,搜索用时 218 毫秒
101.
Boyd DR Sharma ND Bowers NI Boyle R Harrison JS Lee K Bugg TD Gibson DT 《Organic & biomolecular chemistry》2003,1(8):1298-1307
Toluene dioxygenase (TDO)-catalysed benzylic hydroxylation of indene substrates (8, 16 and 17), using whole cell cultures of Pseudomonas putida UV4, was found to yield inden-1-ol (14 and 22) and indan-1-one bioproducts (15 and 23). The formation of these bioproducts is consistent with the involvement of carbon-centred radical intermediates. TDO-catalysed oxidation of indenes 8 and 16 also gave cis-diols 13 and 18 respectively. TDO and naphthalene dioxygenase (NDO), used as both whole-cell preparations and as purified enzymes, were found to catalyse the benzylic hydroxylation of chromane 30, deuteriated (+/-)-chromane 30D and enantiomers (4S)-30D and (4R)-30D to yield (4R)- and (4S)-chroman-4-ols 31/31D respectively. The mechanism of benzylic hydroxylation of chromane 30/30D involves the stereoselective abstraction of a pro-R (with TDO) or a pro-S (with NDO) hydrogen atom at C-4 and a marked preference for retention of configuration. 相似文献
102.
Zhao L Niel V Thompson LK Xu Z Milway VA Harvey RG Miller DO Wilson C Leech M Howard JA Heath SL 《Dalton transactions (Cambridge, England : 2003)》2004,(9):1446-1455
Polynuclear manganese(II), cobalt(II)/(III), iron(II)/(III) and nickel(II) complexes of a group of flexible polydentate dihydrazone ligands, based on pyridine-2,6-dipicolinic (A), oxalic (B) and malonic (C) subunits are described. Structural details are reported for the linear dinuclear complexes [Ni2(2poap)2(H2O)2](NO3)4 . 2CH3OH . 2.5H2O (1), [Mn2(pttp)(NO3)2(CH3OH)2(H2O)2](NO3)2 . H2O (2) and [Mn2(mapttp)2(NO3)2(H2O)2](NO3)2 . 10H2O (3), a square tetranuclear complex [Co4(pttp)4]Br6 . 9H2O (4), a tetranuclear tetrahedral complex [Ni4(pttp)6](BF4)6F2 . 14H2O (7), and a mixed spin state tetranuclear Ni(II) complex [(2pyoap)2Ni4(CH3OH)4] . 1.5CH3OH (10), with a diamond-like arrangement of metal ions. The paramagnetic metal centers are well separated in each case, leading to weak antiferromagnetic coupling or non-existent spin exchange. 相似文献
103.
Structurally Divergent Lithium Catalyzed Friedel–Crafts Reactions on Oxetan‐3‐ols: Synthesis of 3,3‐Diaryloxetanes and 2,3‐Dihydrobenzofurans
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Rosemary A. Croft Dr. James J. Mousseau Chulho Choi Dr. James A. Bull 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16271-16276
The first examples of 3,3‐diaryloxetanes are prepared in a lithium‐catalyzed and substrate dependent divergent Friedel–Crafts reaction. para‐Selective Friedel–Crafts reactions of phenols using oxetan‐3‐ols afford 3,3‐diaryloxetanes by displacement of the hydroxy group. These constitute new isosteres for benzophenones and diarylmethanes. Conversely, ortho‐selective Friedel–Crafts reactions of phenols afford 3‐aryl‐3‐hydroxymethyl‐dihydrobenzofurans by tandem alkylation–ring‐opening reactions; the outcome of the reaction diverging to structurally distinct products dependent on the substrate regioselectivity. Further reactivity of the oxetane products is demonstrated, suitable for incorporation into drug discovery efforts. 相似文献
104.
Rosemary Castorina Marie Tysman Asa Bradman Sara Hoover Shoba Iyer Marion Russell 《International journal of environmental analytical chemistry》2016,96(13):1247-1263
There is little published research examining volatile organic compound (VOC) emissions from art markers. In this study, we characterised VOC emission rates from markers commonly used by children at home and in school, and by teachers in their classrooms. We developed a method to measure standardised emission rates under controlled laboratory conditions, focusing on four major marker types: permanent, dry erase, highlighter, and washable. Emission rates for other less common marker types were also measured. We conducted additional experiments determining changes in emission profiles over short and long time periods (several hours up to daily use over about 2 months), as well as during periods of active drawing. We tested a total of 101 markers and report emission rates for 60 chemicals. Permanent and dry erase markers had average total VOC emissions more than 400 times higher than highlighters and washable markers. Alcohols were the most highly emitted class of VOCs from permanent and dry erase markers. Some chemicals associated with potentially serious health concerns were also identified. Future studies that employ full-scale chamber experiments and personal monitoring in classrooms to measure children’s actual exposures are recommended. 相似文献
105.
Dr. Huy N. Hoang Dr. Russell W. Driver Dr. Renée L. Beyer Dr. Timothy A. Hill Dr. Aline D. de Araujo Dr. Fabien Plisson Dr. Rosemary S. Harrison Lena Goedecke Dr. Nicholas E. Shepherd Prof. David P. Fairlie 《Angewandte Chemie (International ed. in English)》2016,55(29):8275-8279
Cyclic pentapeptides (e.g. Ac‐(cyclo‐1,5)‐[KAXAD]‐NH2; X=Ala, 1 ; Arg, 2 ) in water adopt one α‐helical turn defined by three hydrogen bonds. NMR structure analysis reveals a slight distortion from α‐helicity at the C‐terminal aspartate caused by torsional restraints imposed by the K(i)–D(i+4) lactam bridge. To investigate this effect on helix nucleation, the more water‐soluble 2 was appended to N‐, C‐, or both termini of a palindromic peptide ARAARAARA (≤5 % helicity), resulting in 67, 92, or 100 % relative α‐helicity, as calculated from CD spectra. From the C‐terminus of peptides, 2 can nucleate at least six α‐helical turns. From the N‐terminus, imperfect alignment of the Asp5 backbone amide in 2 reduces helix nucleation, but is corrected by a second unit of 2 separated by 0–9 residues from the first. These cyclic peptides are extremely versatile helix nucleators that can be placed anywhere in 5–25 residue peptides, which correspond to most helix lengths in protein–protein interactions. 相似文献
106.
107.
108.
Kevin W. Kells Nathan H. Nielsen Rosemary J. Armstrong-Chong J. Michael Chong 《Tetrahedron》2002,58(52)
Norephedrine carbamate derivatives of α-hydroxystannanes can be readily prepared and the resulting diastereomers are separable by column chromatography. Removal of the carbamate moiety by reduction provides enantiomerically-enriched α-hydroxystannanes. 相似文献
109.
Fast algorithms, based on the unsymmetric look‐ahead Lanczos and the Arnoldi process, are developed for the estimation of the functional Φ(?)= u T?(A) v for fixed u , v and A, where A∈??n×n is a large‐scale unsymmetric matrix. Numerical results are presented which validate the comparable accuracy of both approaches. Although the Arnoldi process reaches convergence more quickly in some cases, it has greater memory requirements, and may not be suitable for especially large applications. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
110.
M. J. Rosemary V. Suryanarayanan P. Ganapatireddy Ian Maclaren S. Baskaran T Pradeep 《Journal of Chemical Sciences》2003,115(5-6):703-709
We report a new nanomaterial in which ciprofloxacin molecules are incorporated inside silica nanobubbles, denoted as ciprofloxacin@SiO2. The material has been characterised using UV/Vis absorption spectroscopy, transmission electron microscopy, cyclic voltammetry,
and emission spectroscopy. The material is stable and the freestanding particles can be precipitated and redispersed in several
solvents. Confinement of the molecule is complete as leaching through the shell is minimal. The material behaves like free
ciprofloxacin in solution; however, effects of confinement are manifested. Energy transfer reaction between ciprofloxacin@SiO2 and Tb3+ was monitored by emission spectroscopy. The emission intensity decreased with metal ion exposure indicating selective electronic
interaction.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献