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21.
Ender Unsal Erdal Uguzdogan Süleyman Patir Ali Tuncel 《Journal of separation science》2009,32(11):1791-1800
An ion‐exchanger with polyanionic molecular brushes was synthesized by a “grafting from” route based on “surface‐controlled reversible addition‐fragmentation chain transfer polymerization” (RAFT). The RAFT agent, PhC(S)SMgBr was covalently attached to monodisperse‐porous poly(dihydroxypropyl methacrylate‐co‐ethylene dimethacrylate), poly(DHPM‐co‐EDM) particles 5.8 μm in size. The monomer, 3‐sulfopropyl methacrylate (SPM), was grafted from the surface of poly(DHPM‐co‐EDM) particles with an immobilized chain transfer agent by the proposed RAFT protocol. The degree of polymerization of SPM (i. e. the molecular length of the polyanionic ligand) on the particles was controlled by varying the molar ratio of monomer/RAFT agent. The particles carrying polyanionic molecular brushes with different lengths were tested as packing material in the separation of proteins by ion exchange chromatography. The columns packed with the particles carrying relatively longer polyanionic ligands exhibited higher separation efficiency in the separation of four proteins. Plate heights between 130–200 μm were obtained. The ion‐exchanger having poly‐(SPM) ligand with lower degree of polymerization provided better peak‐resolutions on applying a salt gradient with higher slope. The molecular length and the ion‐exchanger group content of polyionic ligand were adjusted by controlling the degree of polymerization and the grafting density, respectively. This property allowed control of the separation performance of the ion‐exchanger packing. 相似文献
22.
The subject of investigation is the early stage of self-consistent trapping of electrons into a potential well that forms during the development of aperiodic Pierce instability. An analytical estimate for threshold gap δth = d th/λD (λD is the Debye beam length) above which the trapping begins is derived. The nonlinear dynamics and distribution function of trapped electrons are studied in detail using a numerical method ((E, K) code). It is found that the trapped particles produce a localized steep-edge bunch, which “dangles” around between the electrodes, causing potential oscillations. Trapped electrons render the well shallower. Some of the particles in the bunch are shown to periodically escape to the electrodes. As a result, the potential oscillation amplitude fades away and the mean depth of the well increases. 相似文献
23.
Ender Erdik Author Vitae 《Tetrahedron》2004,60(40):8747-8782
24.
Kinetic studies on the t-amine inhibited catalytic OsO4 dihydroxylation of cyclooctene, octene, styrene and 4-methyl-, 4-methoxy-, 4-chloro-, 4-(chloromethyl), 4-(trifluoromethyl) and 3-chloro-derivatives of styrene with Me3NO in t-BuOH have been carried out at 50 °C. The reactions follow identical kinetics: first order in total osmium species, first order in Me3NO and zero order in alkene. All t-amines have been found to retard the catalysis and the reaction order in t-amine changes from inverse first order to zero. The involvement of dioxomonoglycolataosmium(VI) esters and their monoamine adducts in the rate-determining oxidation step was established by the linear plots of 1/k
2
versus. 1/[L] where k
2 is the decrease in second order rate constant in the presence of [L] concentration of t-amine ligand. Beyond a definite concentration of t-amine, the rate reaches a minimum and remains constant. Activation parameters were evaluated for catalytic OsO4 dihydroxylation of 4-(chloromethyl)styrene at different t-amine concentrations. The values of H
and S
are consistent with the proposed mechanism. 相似文献
25.
The C–S coupling reactions of aryl benzenesulfonates with phenylmagnesium bromide in THF:toluene (7:10) at 90 °C have been
studied. A Hammett-type kinetic study of the leaving group effect of aryloxy groups provides a conclusive support for a two
step addition-elimination mechanism in which C–S bond formation is rate determining step. 相似文献
26.
Ender Ercan Yan-Cheng Lin Chun-Kai Chen Yi-Kai Fang Wei-Chen Yang Yun-Fang Yang Wen-Chang Chen 《Journal of polymer science. Part A, Polymer chemistry》2022,60(3):525-537
Photonic field-effect transistor (FET) memory devices offer unique advantages owing to their solution processability, low cost production, and their lightweight and structural flexibility. Despite the plethora of research demonstrated the photon based programming process, limited reports are available for photoinduced recovery mechanism in such devices. To investigate the influence of polymer electret design on photonic memory performance, poly(9,9-dioctylfluorene) (PFO)–block–poly (vinylphenyl oxadiazole) (POXD) conjugated block copolymers were employed to a photonic FET memory with n-type semiconducting channel. The studied device exhibited bistable ON/OFF current states after electrical programming and photoinduced recovery (erasing) processes. The device operating mechanism was elaborated by comparing the device performance with respective electrets of PFO-b-POXD and PFO-b-polystyrene (PS) and PFO homopolymer. We found that PFO-b-POXD can efficiently generate photoexciton under UV illumination to neutralize the trapped hole, and assuage the hole trapping propensity of PFO segment, simultaneously. By optimizing the POXD content in the block copolymer, a decent memory ratio (ION/IOFF) of ~105 was achieved after 104 s, indicating its superior long-term stability and data discernibility. This research shows the judicious strategy to design polymer electret for photonic memory, and it opens up the possibility of developing photonic memory, human perception and futuristic communication systems using simple, convenient and reliable optoelectronic technique. 相似文献
27.
S. Wan J. Gerl J. Cub J.M. Holeczek P. Reiter D. Schwalm T. Aumann K. Boretzky W. Dostal B. Eberlein H. Emling Ch. Ender Th.W. Elze H. Geissel A. Grünschloß R. Holzmann N. Iwasa M. Kaspar A. Kleinböhl O. Koschorrek Y. Leifels A. Leistenschneider I. Peter H. Schaffner C. Scheidenberger R. Schubart R. Schubert H. Simon G. Stengel A. Surowiec H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》1999,6(2):167-174
This work demonstrates the feasibility of in-beam %-spectroscopy employing radioactive ion beam species at relativistic energies of E = 210 ~ 280 A · MeV. Neutron-rich nuclei below 48Ca with neutron number between the two magic numbers 20 and 28 have been investigated. Using a Pb target, single step inelastic excitation originating mainly from Coulomb interaction takes place populating preferentially low-lying low-spin states and enabling the extraction of B(E2) values. On a C target, nucleon removal reactions are dominating and medium-spin states are populated thus offering spectroscopic information in neighboring nuclei. Cross sections of inelastic excitation are determined and compared to coupled-channels calculations. Two new states of the very neutron-rich nucleus 44Ar at 1.78(8) MeV and 2.61(16) MeV are deduced from %-transitions. 相似文献
28.
Reaction of methyl arylzincs with acetone O‐(mesitylenesulfonyl)oxime in THF in the presence of CuCN at room temperature is efficient in selective electrophilic amination of aryl carbanions. This procedure allows for the preparation of arylamines in moderate to good yields and provides an efficient and atom economic alternative to existing amination methods for diarylzincs. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
29.
Synthesis,spectroscopic and voltammetric studies of mixed-ligand copper(II) complexes of amino acids
Two CuII complexes of the type [Cu(L1)(L2)] (where L1 = tryptophanate or phenylalaninate; L2 = cysteine thiolate) have been prepared and characterised, and their spectrophotometric and voltammetric behaviour has been investigated. The results obtained by means of FT-IR, e.s.r., u.v.–vis. spectroscopy and by voltammetry revealed the existence of two different [Cu(L1)(L2)] complexes. A significance decrease in the g
|| value and, concomitantly, an increase in the d–d transition energy was observed when a mixed-ligand complex is present. The observed anisotropic g-values indicate the presence of CuII in a tetragonally distorted octahedral geometry. Formation of a mixed-ligand copper complex can be considered as a type of synergism in the presence of cysteine. The redox state CuII or CuI of copper in the Cu(L2) complex depends on the analysing conditions, i.e., cysteine forms a CuII complex under aerobic conditions and a CuI complex in anaerobic media. Tryptophan or phenylalanine is bound to CuII ions in the Cu(L1) complexes. 相似文献
30.
Syariza Abdul Rahman Andrzej Bargiela Edmund K. Burke Ender Özcan Barry McCollum Paul McMullan 《European Journal of Operational Research》2014
In this paper, we investigate adaptive linear combinations of graph coloring heuristics with a heuristic modifier to address the examination timetabling problem. We invoke a normalisation strategy for each parameter in order to generalise the specific problem data. Two graph coloring heuristics were used in this study (largest degree and saturation degree). A score for the difficulty of assigning each examination was obtained from an adaptive linear combination of these two heuristics and examinations in the list were ordered based on this value. The examinations with the score value representing the higher difficulty were chosen for scheduling based on two strategies. We tested for single and multiple heuristics with and without a heuristic modifier with different combinations of weight values for each parameter on the Toronto and ITC2007 benchmark data sets. We observed that the combination of multiple heuristics with a heuristic modifier offers an effective way to obtain good solution quality. Experimental results demonstrate that our approach delivers promising results. We conclude that this adaptive linear combination of heuristics is a highly effective method and simple to implement. 相似文献