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51.
A.M. Pitts 《Fuzzy Sets and Systems》1982,8(1):101-104
The relationship between fuzzy sets and H-valued sets is briefly examined and a claim of Eytan's that the former comprise the objects of a topos is corrected. 相似文献
52.
The gas-phase reaction of the NO3 radical with NO2 was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10?13 cm3 molecule?1 s?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N2 and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O2. These data show that the third-body efficiencies of N2 and O2 are identical, within the error limits, and that previous evaluations for M = N2 are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO3 radical with methanol, ethanol, and propan-2-ol of ?6 × 10?16, ?9 × 10?16, and ?2.3 × 10?15 cm3 molecule?1 s?1, respectively, at 298 ± 2 K. 相似文献
53.
Dr. Phil Liebing Dr. Cody Ross Pitts Marc Reimann Dr. Nils Trapp Dr. David Rombach Dustin Bornemann Prof. Dr. Martin Kaupp Prof. Dr. Antonio Togni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(19):6086-6093
The analysis of crystal structures of SF5- or SF4-containing molecules revealed that these groups are often surrounded by hydrogen or other fluorine atoms. Even though fluorine prefers F⋅⋅⋅H over F⋅⋅⋅F contacts, the latter appeared to be important in many compounds. In a significant number of datasets, the closest F⋅⋅⋅F contacts are below 95 % of the van der Waals distance of two F atoms. Moreover, a number of repeating structural motifs formed by contacts between SF5 groups was identified, including different supramolecular dimers and infinite chains. Among SF4-containing molecules, the study focused on SF4Cl compounds, including the first solid-state structure analyses of these reactive species. Additionally, electrostatic potential surfaces of a series of Ph-SF5 derivatives were calculated, pointing out the substituent influence on the ability of F⋅⋅⋅X contact formation (X=F or other electronegative atom). Interaction energies were calculated for different dimeric arrangements of Ph-SF5, which were extracted from experimental crystal structure determinations. 相似文献
54.
3D X-ray computer microtomography (CT) experiments have been performed to assess the microstructure of scaled cellular polysiloxane elastomers and to predict how key morphological features alter as a function of compressive loading. In the work reported here, full scale (nominally 600 μm pore size) and half scale (nominally 300 μm pore size) polydimethylsiloxane foams (M97) were prepared using extractable urea particles, and tested. CT test methodology was developed to image foam microstructure at different levels of compression. 1D magnetic resonance imaging (MRI) experiments have also been performed on full scale foams for baseline characterisation. Material porosity, bulk density and dynamic mechanical analysis (DMA) stress/strain responses as a function of compression were recorded. Our results show that undesirable engineering stress responses are evident when the material microstructure (cell size and shape) is non-uniform and complex. This is particularly evident when non-spherical urea particles are used, leading to undesirable scaled foam microstructures with mechanical responses that do not match that shown by ‘full scale’ versions. Through the use of X-ray CT and MRI, our studies have provided insights into the link between manufacturing, polymer architecture (cell size/shape) and mechanical response of scaled M97 cellular materials. The data collected will support materials FEA (finite element model) code development activities, as well as help identify how the material architecture can be modified to achieve more controlled and uniform mechanical responses. 相似文献
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56.
J. N. Lisgarten B. S. Potter R. A. Palmer James E. Pitts C. W. Wright 《Journal of chemical crystallography》2008,38(11):815-819
Abstract The structure of C16H10N4O4[HCl,1.5CH3OH], Mr = 406.80, has been determined from X-ray diffraction data. The crystals are monoclinic, space group C2/c, with eight molecules
per unit cell and a = 21.482(4), b = 7.131(1), c = 24.495(5) ?, β = 111.01(3)°, crystal density Dc = 1.546 g/cm3. The material was difficult to crystallize and crystals produced were found to be poor diffractors. Intensity data were measured
at liquid nitrogen temperature using a weakly diffracting crystal typical of the batch. However the X-ray analysis has finally
enabled the chemical constitution of this cryptolepine derivative, which was previously incorrectly assigned, to be unequivocally
established. Direct methods were used to solve the structure which was refined by full-matrix least squares to a conventional
R-index of 0.0798 for 2,861 reflections and 268 parameters. The 7,9-dinitrocryptolepine molecule is highly planar with a strong
intramolecular hydrogen bond between N(10) in ring C and O(92) of a nitro group. There are a number of intermolecular hydrogen
bonds involving the cryptolepine derivative the hydrochloride and both solvated methanols. One of the methanol solvate molecules
(methanol 2) is unusually disordered with its C atom lying exactly on a crystallographic twofold axis. Consequently the methanol
OH and H3 groups are at 0.5 occupancy and repeated by the twofold symmetry.
Graphical Abstract Cryptolepine (5-methyl, 10H-indolo[3,2-b]quinoline) the principal constituent of Cryptolepis sanguinolenta (Periplocaceae) is currently of interest as a lead compound for the development of both antimalarial and anticancer agents.
Cryptolepine has potent activity against malaria parasites in vitro, but it is also cytotoxic on account of its abilities
to intercalate into DNA, inhibit DNA synthesis and inhibit topoisomerase II. The 7,9-dinitroanalogue of cryptolepine was synthesised
as part of a program designed to discover new antimalarial and anticancer agents. The X-ray structure of this compound will
help to determine whether or not 7,9-dinitrocryptolepine is able to intercalate into DNA and facilitate the design of new
cryptolepine analogues with DNA binding properties appropriate for antimalarial (with no DNA intercalation) or anticancer
(sequence-specific binding) applications.
相似文献
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59.
In vivo sodium-23 magnetic resonance surface coil imaging: Observing experimental cerebral ischemia in the rat 总被引:2,自引:0,他引:2
Michael E. Moseley Ph.D. Wil M. Chew B.S. Merry C. Nishimura B.S. Todd L. Richards Ph.D. Joseph Murphy-Boesch Ph.D. Gregory B. Young Ph.D. Thomas M. Marschner Ph.D. Lawrence H. Pitts M.D. Thomas L. James Ph.D. 《Magnetic resonance imaging》1985,3(4):383-387
Sodium-23 magnetic resonance imaging can be used to detect and assess experimental cerebral ischemia in the rat. An imaging technique utilizing a surface coil is described to produce sodium magnetic resonance images of good quality and resolution within 10 min. A novel method of hemispheric occlusion showed edema in the right brain of the rat head within 3 hr after injury. The edema was especially pronounced by 12 hr with effects in the right brain, eye and surrounding muscle evident. 相似文献
60.
Third order rate constants have been determined for the reaction O + SO2 + N2O → SO3 + N2O over the temperature range 299–392 K using a modulation technique. The Arrhenius expression obtained is k2N2O = 3.32 × 1010 exp[?(2000±400)/RT] liter2 mole?2 s?1. This temperature dependence is in good agreement with recent flash photolysis-resonance fluorescence measurements using N2 as a third body. 相似文献