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81.
James R. Birch 《Mikrochimica acta》1987,93(1-6):105-122
A review is presented of recent developments in the methods of dispersive Fourier transform spectroscopy that have demonstrated the unique value of this broad band method for determining the optical constants of gases, liquids and solids. 相似文献
82.
Alexander M. Macmillan Dalibor Panek Colin D. McGuinness John C. Pickup Duncan Graham W. Ewen Smith David J. S. Birch Jan Karolin 《Journal of Sol-Gel Science and Technology》2009,49(3):380-384
By using the fluorescent dye 6-propionyl-2-(N,N-dimethylamino) naphthalene (PRODAN) to monitor methanol generated during tetramethyl orthosilicate polymerization we have
optimised the encapsulation of protein in silica sol–gel monoliths with respect to completion of hydrolysis and distillation
in order to remove methanol such that protein can be added without denaturation. A minimum of 24 h at +4 °C was found to be
required before hydrolysis is complete and 3–5 min of vacuum distillation at 50 °C and 300 mbar needed to remove methanol
before the gel is formed. The biocompatibility of a tetramethyl orthosilicate sol–gel monolith was demonstrated by preserving
the trimer protein allophycocyanin (APC) in its native form for up to 500 h. This obviates the previously essential requirement
of covalently binding the trimer together in order to prevent dissociation into monomers and has enabled observation of native
APC trimer in a sol–gel pore for the first time down to the single molecule level using combined fluorescence spectroscopy
and confocal microscopy. The higher stability afforded by the protocol we describe could impact on the application of sol–gel
materials to single-molecule studies of wider bearing such as protein folding and aggregation. 相似文献
83.
Olav Vahtras Hans rgren Hans Jrgen AA. Jensen 《Journal of computational chemistry》1994,15(6):573-579
The evaluation of gradient vectors of a general operator with one-index, double-one-index, or higher-order one-index transformed integrals is a key operation in multiconfiguration response theory calculations. We describe an integral-driven direct algorithm that carries out this operation efficiently without pretransforming the integrals. The use of this algorithm leads to a considerable reduction in disk space and timing. © 1994 by John Wiley & Sons, Inc. 相似文献
84.
Ryan J. MacDonell Claire E. Dickerson Clare J. T. Birch Alok Kumar Claire L. Edmunds Michael J. Biercuk Cornelius Hempel Ivan Kassal 《Chemical science》2021,12(28):9794
Ultrafast chemical reactions are difficult to simulate because they involve entangled, many-body wavefunctions whose computational complexity grows rapidly with molecular size. In photochemistry, the breakdown of the Born–Oppenheimer approximation further complicates the problem by entangling nuclear and electronic degrees of freedom. Here, we show that analog quantum simulators can efficiently simulate molecular dynamics using commonly available bosonic modes to represent molecular vibrations. Our approach can be implemented in any device with a qudit controllably coupled to bosonic oscillators and with quantum hardware resources that scale linearly with molecular size, and offers significant resource savings compared to digital quantum simulation algorithms. Advantages of our approach include a time resolution orders of magnitude better than ultrafast spectroscopy, the ability to simulate large molecules with limited hardware using a Suzuki–Trotter expansion, and the ability to implement realistic system-bath interactions with only one additional interaction per mode. Our approach can be implemented with current technology; e.g., the conical intersection in pyrazine can be simulated using a single trapped ion. Therefore, we expect our method will enable classically intractable chemical dynamics simulations in the near term.Dynamics governing ultrafast chemical reactions can be efficiently simulated using analog quantum simulators composed of a coupled system of qudits and bosonic modes. 相似文献
85.
Tuck KL Saldanha SA Birch LM Smith AG Abell C 《Organic & biomolecular chemistry》2006,4(19):3598-3610
Pantothenate synthetase catalyses the ATP-dependent condensation of D-pantoate and beta-alanine to form pantothenate. Ten analogues of the reaction intermediate pantoyl adenylate, in which the phosphodiester is replaced by either an ester or sulfamoyl group, were designed as potential inhibitors of the enzyme. The esters were all modest competitive inhibitors, the sulfamoyls were more potent, consistent with their closer structural similarity to the pantoyl adenylate intermediate. 相似文献
86.
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88.
We have developed a new method for measuringin- situ the growth of the nanometre-size silica particles which lead to the formation of sol-gel glasses. This technique is based
on the decay of fluorescence polarisation anisotropy due to Brownian rotation of dye molecules bound to the particles. Results
to date give near ?ngstrom resolution and demonstrate the feasibility of the approach both for providing industrial quality
control and helping fundamental research. Our approach has several key advantages over traditional techniques for nanometre
metrology, such as small angle X-ray and neutron scattering and electron microscopy. In this paper we present silica particle
growth dynamics in a hydrogel as detected by two near-infrared dyes, the effect of adding D2O on the hydrodynamic radius and the effect of salt addition. 相似文献
89.
It is shown how one can transform scalar first-order ordinarydifferential equations which admit non-local symmetries of theexponential type to integrable equations admitting canonicalexponential non-local symmetries. As examples we invoke theAbel equation of the second kind, the Riccati equation and naturalgeneralizations of these. Moreover, our method describes howa double reduction of order for a second-order ordinary differentialequation which admits a two-dimensional Lie algebra of generatorsof point symmetries can be affected if the second-order equationis first reduced in order once by a symmetry which does notspan an ideal of the two-dimensional Lie algebra. 相似文献
90.
A method is described for the production of screen-printed graphite electrodes and also for similar electrodes chemically modified with the electrocatalyst cobalt phthalocyanine. Using cyclic voltammetry, the electrochemical behaviour of these electrodes towards ascorbic acid, reduced glutatione and coenzyme A (CoA-SH) was investigated. The modified electrodes were found to give significant decreases in the over-potential required for the oxidation of these species at carbon electrodes. The useful electrochemical window for the unmodified carbon film electrodes was ?1.08 V to +0.85 V vs. SCE, using 1 μA background current cut-off points.Amperometry in stirred solutions was used to investigate the hydrodynamic behaviour of the electrodes and their calibration performance. The limits of detection for ascorbic acid and reduced glutathione at the modified films were 5 × 10?8 and 1 × 10?7 M, respectively. The calibration graphs were also linear up to 2 mM concentrations of both analytes. Using differential-pulse voltammetry, linear calibration graphs were obtained for both species up to 2.5 mM. This technique was also used to assess the reproducibility of the electrode manufacture; the coefficient of variation was 2.8% for 1.49 mM ascorbic acid and 6.9% for 0.92 mM reduced glutathione. 相似文献