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排序方式: 共有105条查询结果,搜索用时 15 毫秒
11.
Colette J. Whitfield Andrew T. Turley Dr. Eimer M. Tuite Prof. Bernard A. Connolly Dr. Andrew R. Pike 《Angewandte Chemie (International ed. in English)》2015,54(31):8971-8974
A polymerase chain reaction (PCR) derived method for preparing long DNA, consisting of multiple repeat units of one to ten base pairs, is described. Two seeding oligodeoxynucleotides, so‐called oligoseeds, which encode the repeat unit and produce a duplex with 5′‐overhangs, are extended using a thermostable archaeal DNA polymerase. Multiple rounds of heat–cool extension cycles, akin to PCR, rapidly elongate the oligoseed. Twenty cycles produced long DNA with uniformly repeating sequences to over 20 kilobases (kb) in length. The polynucleotides prepared include [A]n/[T]n, [AG]n/[TC]n, [A2G]n/[T2C]n, [A3G]n/[T3C]n, [A4G]n/[T4C]n, [A9G]n/[T9C]n, [GATC]n/[CTAG]n, and [ACTGATCAGC]n/[TGACTAGTCG]n, indicating that the method is extremely flexible with regard to the repeat length and base sequence of the initial oligoseeds. DNA of this length (20 kb≈7 μm) with strictly defined base reiterations should find use in nanomaterial applications. 相似文献
12.
13.
T.J. Bastow M.E. Hobday M.E. Smith H.J. Whitfield 《Solid state nuclear magnetic resonance》1996,5(4):293-303
The NMR interactions of crystalline phases in the system Na2O-ZrO2-SiO2 have been studied by a combination of static and magic angle spinning NMR methods for the first time. A full multinuclear (17O, 23Na, 29Si and 91Zr) approach has been employed that allows the phases to be clearly identified. NMR interactions such as 29Si isotropic chemical shift correlate with the known structural units present. For 23Na the different sites can often be distinguished on the basis of differing quadrupolar interactions. 相似文献
14.
P.H. Cannington H.J. Whitfield 《Journal of Electron Spectroscopy and Related Phenomena》1977,10(1):35-44
The He(I) UV photoelectron spectra of As4S3, P4S3, P4Se3 and As4O6 are reported in this paper. The spectra of As4S3 and the isostructural molecules P4S3 and P4Se3 comprise seven broad but clearly defined peaks, whilst the spectrum of As4O6 consists of six peaks and two shoulders. By comparing the spectra with one another and with the photoelectron spectra of other arsenic and phosphorus compounds, the character and symmetry species of the highest-energy occupied molecular orbitals of the molecules have been assigned. 相似文献
15.
Authentication and authenticated key exchanges 总被引:41,自引:0,他引:41
Whitfield Diffie Paul C. Van Oorschot Michael J. Wiener 《Designs, Codes and Cryptography》1992,2(2):107-125
We discuss two-party mutual authentication protocols providing authenticated key exchange, focusing on those using asymmetric techniques. A simple, efficient protocol referred to as the station-to-station (STS) protocol is introduced, examined in detail, and considered in relation to existing protocols. The definition of a secure protocol is considered, and desirable characteristics of secure protocols are discussed.This work was done while Whitfield Diffie was with Northern Telecom, Mountain View, California. 相似文献
16.
Pulsed Fourier transform NQR spectroscopy has been used to study polytypism in the monochalcogenides GaS, GaSe and InSe at 77 K. The spectrum of GaS was consistent with a major contribution from the β phase but showed evidence of higher polytypes, possibly due to ? or γ type faulting. The GaSe spectrum is simply interpreted as an equal mixture of ? and γ types. The four InSe spectra (115In), showed a multiplicity of lines. The sharpness of the NQR lines of all spectra suggests the existence of regions with a hitherto overlooked high degree of order. 相似文献
17.
If a separable Banach spaceX admits a real valued function ф with bounded nonempty support, φ 艂 is locally Lipschitzian and if no subspace ofX is isomorphic toc
o, thenX admits an equivalent twice Gateaux differentiable norm whose first Frechet differential is Lipschitzian on the unit sphere
ofX.
This author's research supported in part by NSERC (Canada) Grant A7535. 相似文献
18.
19.
Whitfield TW Martyna GJ Allison S Bates SP Vass H Crain J 《The journal of physical chemistry. B》2006,110(8):3624-3637
The results of classical molecular dynamics (MD) simulations and Raman spectroscopy studies of neat liquid N-methylacetamide (NMA), the simplest model system relevant to the peptides, are reported as a function of temperature and pressure. The MD simulations predict that near ambient conditions, the molecules form a hydrogen bond network consisting primarily of linear chains. Both the links between molecules within the hydrogen-bonded chains and the associations between chains are stabilized by weak methyl-donated "improper" hydrogen bonds. The three-dimensional structural motifs observed in the liquid show some similarity to protein beta-sheets. The temperature and pressure dependence of the hydrogen bond network, as probed by the mode frequency of the experimentally determined amide-I Raman band, blue shifts on heating and red shifts under compression, respectively, suggesting weakened and enhanced hydrogen bonding in response to temperature and pressure increases. Disruption of the hydrogen-bonding network is clearly observed in the simulation data as temperature is increased, whereas the improper hydrogen bonding is enhanced under compression to reduce the energetic cost of increasing the packing fraction. Because of the neglect of polarizability in the molecular model, the computed dielectric constant is underestimated compared to the experimental value, indicating that the simulation may underestimate dipolar coupling in the liquid. 相似文献
20.
James D. Whitfield 《Molecular physics》2013,111(5):735-750
Over the last century, a large number of physical and mathematical developments paired with rapidly advancing technology have allowed the field of quantum chemistry to advance dramatically. However, the lack of computationally efficient methods for the exact simulation of quantum systems on classical computers presents a limitation of current computational approaches. We report, in detail, how a set of pre-computed molecular integrals can be used to explicitly create a quantum circuit, i.e. a sequence of elementary quantum operations, that, when run on a quantum computer, obtains the energy of a molecular system with fixed nuclear geometry using the quantum phase estimation algorithm. We extend several known results related to this idea and discuss the adiabatic state preparation procedure for preparing the input states used in the algorithm. With current and near future quantum devices in mind, we provide a complete example using the hydrogen molecule of how a chemical Hamiltonian can be simulated using a quantum computer. 相似文献