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排序方式: 共有64条查询结果,搜索用时 328 毫秒
21.
Basra S De Vries JG Hyett DJ Harrison G Heslop KM Orpen AG Pringle PG Von Der Luehe K 《Dalton transactions (Cambridge, England : 2003)》2004,(12):1901-1905
The unsymmetrical, optically active ligands 1,2-C(6)H(4)(PPh(2))((R,R)-2,5-dimethylphospholanyl) and the new 1,1'-Fe(C(5)H(4))(2)(PPh(2))((R,R)-2,5-dimethylphospholanyl) form complexes of the type [PtCl(2)(diphos)] and [Rh(diphos)(diene)][BF(4)]. The crystal structure of reveals that only one quadrant is blocked. Asymmetric hydrogenation of acrylic esters and enamides using and as catalysts show that the phenylene-backboned diphosphine gives a more efficient catalyst in terms of asymmetric induction than the more flexible ferrocene-backboned diphosphine. The best results, which were obtained with and enamide substrates, exceeded those obtained with Duphos catalysts. The rate of hydrogenation of the enamides with was 10 times faster than with [Rh(Duphos)(diene)][BF(4)]. A quadrant diagram can be used to predict the configuration of the major product, provided it is assumed to be derived from the less sterically congested intermediate. 相似文献
22.
Kirsty J. Pringle J. Christopher Whitehead Jonathan J. Wilman Jinhui Wu 《Plasma Chemistry and Plasma Processing》2004,24(3):421-434
The destruction of methane by a nonthermal plasma in atmospheric pressure gas streams of nitrogen with variable amounts of added oxygen has been investigated. The identities and concentrations of the endproducts are determined by online FTIR spectroscopy and the plasma chemistry is interpreted using kinetic modelling. For a deposited energy of 118 kJ m–3, the destruction is 12% in nitrogen decreasing monotonically to 5% in air. The major endproducts are HCN and NH3 in nitrogen and CO, CO2, N2O, NO and NO2 for gas streams containing oxygen. The chemistry in pure nitrogen is predominantly due to reactions of electronicallyexcited nitrogen atoms, N(2D). The addition of oxygen converts the excited state nitrogen into nitrogen oxides reducing the methane destruction which then arises by O and OH reactions yielding CO and, to a lesser extent, CO2. The modelling correctly predicts the magnitude of the methane destruction as a function of added oxygen and the concentrations of the endproducts for processing in both nitrogen and air. 相似文献
23.
Single Oxygen‐Atom Insertion into PB Bonds: On‐ and Off‐Metal Transformation of a Borylphosphine into a Borylphosphinite
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Jonathan A. Bailey Dr. Hazel A. Sparkes Prof. Dr. Paul G. Pringle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5360-5363
An oxygen atom is selectively inserted into the P?B bond of a borylphosphine ( L1 ) by reaction with Me3NO to afford the corresponding borylphosphinite ( L2 ). This transformation can also be effected when L1 is coordinated to rhodium. The ν(CO) values for trans‐[RhCl(CO)(L)2] reveal very different electronic properties for coordinated L1 and L2 which translate into the strikingly different performances of the complexes [RhCl(L)(cod)] (L= L1 or L2 , cod=1,5‐cyclooctadiene) in hydrosilylation and hydroboration catalysis. 相似文献
24.
McDonald S Pringle JM Bishop AG Prenzler PD Robards K 《Journal of chromatography. A》2007,1153(1-2):203-213
Fulvic acids from an Australian floodplain river and billabong were isolated using DEAE and DAX-8 resins, and characterised with the use of size exclusion chromatography and solid-state CP-MAS (13)C NMR spectroscopy. Differences between the two resin isolates were evident. Fulvic acids isolated using DEAE-cellulose had higher apparent M(n) and M(w) values, while the DAX-8 resin showed a slight preference for aliphatic components. Fulvic acids from the river and billabong had the same functional groups present, however, the river fulvic acids had higher apparent M(n) (number average molecular weight) and M(w) values (weight average molecular weight), and were more polydisperse than the billabong fulvic acid. There were no significant changes in the characteristics of the fulvic acid isolated from the river at four sampling times: summer, autumn, winter and spring. In contrast, fulvic acids isolated from a billabong displayed seasonal variation in molecular weights. This work emphasizes the importance in ecological studies of isolation procedure for the operationally defined fulvic acids. 相似文献
25.
We report herein the synthesis of cytotoxic cyanobactin, Wewakazole B through an efficient solution-phase approach. The key steps of the synthesis are the macrocyclic lactamization of linear dodecapeptide and construction of two hexapeptides with three different substituted oxazole rings. 相似文献
26.
ETD in a Traveling Wave Ion Guide at Tuned Z-Spray Ion Source Conditions Allows for Site-Specific Hydrogen/Deuterium Exchange Measurements 总被引:1,自引:0,他引:1
Rand KD Pringle SD Morris M Engen JR Brown JM 《Journal of the American Society for Mass Spectrometry》2011,22(10):1784-1793
The recent application of electron transfer dissociation (ETD) to measure the hydrogen exchange of proteins in solution at
single-residue resolution (HX-ETD) paves the way for mass spectrometry-based analyses of biomolecular structure at an unprecedented
level of detail. The approach requires that activation of polypeptide ions prior to ETD is minimal so as to prevent undesirable
gas-phase randomization of the deuterium label from solution (i.e., hydrogen scrambling). Here we explore the use of ETD in
a traveling wave ion guide of a quadrupole-time-of-flight (Q-TOF) mass spectrometer with a “Z-spray” type ion source, to measure
the deuterium content of individual residues in peptides. We systematically identify key parameters of the Z-spray ion source
that contribute to collisional activation and define conditions that allow ETD experiments to be performed in the traveling
wave ion guide without gas-phase hydrogen scrambling. We show that ETD and supplemental collisional activation in a subsequent
traveling wave ion guide allows for improved extraction of residue-specific deuterium contents in peptides with low charge.
Our results demonstrate the feasibility, and illustrate the advantages of performing HX-ETD experiments on a high-resolution
Q-TOF instrument equipped with traveling wave ion guides. Determination of parameters of the Z-spray ion source that contribute
to ion heating are similarly pertinent to a growing number of MS applications that also rely on an energetically gentle transfer
of ions into the gas-phase, such as the analysis of biomolecular structure by native mass spectrometry in combination with
gas-phase ion-ion/ion-neutral reactions or ion mobility spectrometry. 相似文献
27.
Abraham TJ MacFarlane DR Pringle JM 《Chemical communications (Cambridge, England)》2011,47(22):6260-6262
Measurement of Seebeck coefficients in a range of ionic liquids (ILs) suggests that these electrolytes could enable the development of thermoelectric devices to generate electrical energy from low-grade heat in the 100-150 °C range. 相似文献
28.
Jaka Sunarso Youssof Shekibi Jim Efthimiadis Liyu Jin Jennifer M. Pringle Anthony F. Hollenkamp Douglas R. MacFarlane Maria Forsyth Patrick C. Howlett 《Journal of Solid State Electrochemistry》2012,16(5):1841-1848
Organic ionic plastic crystal (OIPC) electrolytes are among the key enabling materials for solid-state and higher than ambient
temperature lithium batteries. This work overviews some of the parameter studies on the Li|OIPC interface using lithium symmetrical
cells as well as the optimisation and performance of Li|OIPC|LiFePO4 cells. The effects of temperature and electrolyte thickness on the cycle performance of the lithium symmetrical cell, particularly
with respect to the interfacial and bulk resistances, are demonstrated. Whilst temperature change substantially alters both
the interfacial and bulk resistance, changing the electrolyte thickness predominantly changes the bulk resistance only. In
addition, an upper limit of the current density is demonstrated, above which irreversible processes related to electrolyte
decomposition take place. Here, we demonstrate an excellent discharge capacity attained on LiFePO4|10 mol% LiNTf2-doped [C2mpyr][NTf2]|Li cell, reaching 126 mAh g-1 at 50 °C (when the electrolyte is in its solid form) and 153 mAh g-1 at 80 °C (when the electrolyte is in its liquid form). Most remarkably, at high temperature operation, the capacity retention
at long cycles and high current is excellent with only a slight (3%) drop in discharge capacity upon increasing the current
from 0.2 C to 0.5 C. These results highlight the real prospects for developing a lithium battery with high temperature performance
that easily surpasses that achievable with even the best contemporary lithium-ion technology. 相似文献
29.
Laura E. Rush Prof. Dr. Paul G. Pringle Prof. Dr. Jeremy N. Harvey 《Angewandte Chemie (International ed. in English)》2014,53(33):8672-8676
Density functional theory, coupled‐cluster theory, and transition state theory are used to build a computational model of the kinetics of phosphine‐free cobalt‐catalyzed hydroformylation and hydrogenation of alkenes. The model provides very good agreement with experiment, and enables the factors that determine the selectivity and rate of catalysis to be determined. The turnover rate is mainly determined by the alkene coordination step. 相似文献
30.
Zhang J Bond AM MacFarlane DR Forsyth SA Pringle JM Mariotti AW Glowinski AF Wedd AG 《Inorganic chemistry》2005,44(14):5123-5132
The electrochemical reduction of tetrabutylammonium salts of isostructural pairs of polyoxometalates [Bu4N]2[M6O19], [Bu4N]4[alpha-SiM12O40], and [Bu4N]4[alpha-S2M18O62] (M = Mo or W) has been investigated at glassy carbon electrodes in dissolved and surface-confined states in ionic liquids and other media. In the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF(6)], between two and six reversible one-electron-transfer processes were detected. Detailed studies on the process [alpha-S2W18O62](4-/5-) in a range of ionic liquids, water, and conventional organic solvents (containing 0.1 M electrolyte) suggest that the polarity of the medium plays a key role in the determination of the reversible potential. Reduction processes involving very highly charged [alpha-S2W18O62](8-/9-/10-) species are strongly influenced by the purity of the medium. 相似文献