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1.
Sean D. Brooks M. F. Mahmood J. A. Donaldson 《Journal of Mathematical Modelling and Algorithms》2004,3(1):19-29
A numerical investigation, based on the split-step Fourier transform algorithm of all optical switching of solitons in a low
birefringent optical fiber is presented. The numerical algorithm is described in detail.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Andrew C. Brooks Peter Day John D. Wallis 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(5):o245-o247
The crystal structure of the title compound [systematic name: 2‐(1,3‐dithiolo[4,5‐b][1,4]dithiin‐2‐ylidene)‐6,6‐bis(methoxyethoxymethoxymethyl)‐1,3‐dithiolo[4,5‐b][1,4]dithiepine], C21H30O6S8, a spiro‐substituted BEDT–TTF analogue [BEDT–TTF is bis(ethylenedithio)tetrathiafulvalene], has a strongly bent heterocyclic framework. The seven‐membered ring adopts a pseudo‐chair conformation with notably widened ring bond angles, especially at the methylene C atoms [119.49 (11) and 117.60 (11)°]. The axial side chain adopts an extended conformation, but the equatorial side chain curls back on itself and the O atom nearest the ring system is involved in three short contacts to H atoms (2.45–2.53 Å). The molecules pack in centrosymmetrically related pairs, which are isolated from each other by columns of the polyether side chains. This study emphasizes the ease of distortion of the neutral bis(propylenedithio)tetrathiafulvalene ring structure, and how the need to accommodate side chains can easily override the tendency of these donor systems to form stacks in the crystalline state. 相似文献
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A technique has been developed for the determination of In and Tl at very low concentrations in silicate rocks. The iodo-complexes of these elements are extracted from the rock silicate into ethyl cther and the ethereal residues are analysed spectrochemically. The optimum working conditions were established by a study of the variation of percentage extraction as a function of hydrogen iodide normality ; the reproducibility of the spectrochemical procedure was investigated. In and Tl were determined in eight silicate rocks including standard granite G-I and standard diabase W-I. Good agreement was obtained with results of other workers for these two rocks and with the author's previous results. The evidence for a In/Mn coherence in silicate rocks is sufficiently strong to warrant further investigations. 相似文献
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A series of normal mode analyses of bovine pancreatic trypsin inhibitor (BPTI) has been performed. The results of modifying the long-range truncation of electrostatics, reducing the conformational space of the system (reduced basis normal mode analysis), and using different parameter sets and models for the potential function are reported. Both explicit (904 atoms) and polar hydrogen (580 atoms) representations of BPTI were examined and produced nearly identical normal mode vectors but slightly modified vibrational frequencies. The truncation methods—no cutoff, shift, and switch—were examined, and the use of a short switching function was found to alter harmonic motion greatly. A table relating the different cutoff methods to several previously published frequencies for BPTI indicates that the diversity of published lowest frequencies is due to the use of different electrostatic models rather than to inherent differences in the models or energy parameters. Examining reduced basis results demonstrates that a dihedral basis yields similar normal mode vectors, though the vibrational frequencies are shifted to higher values. The analysis of BPTI harmonic dynamics using a spherical harmonic reduced basis set yields significantly altered dynamics, indicating that BPTI is not well represented as a homogeneous object at low temperatures. © 1995 John Wiley & Sons, Inc. 1 This article is a U.S. Government work and, as such, is in the public domain in the United States of America. 相似文献
8.
Gallagher LA Serron SA Wen X Hornstein BJ Dattelbaum DM Schoonover JR Meyer TJ 《Inorganic chemistry》2005,44(6):2089-2097
Photocurrent measurements have been made on nanocrystalline TiO2 surfaces derivatized by adsorption of a catalyst precursor, [Ru(tpy)(bpy(PO3H2)2)(OH2)]2+, or chromophore, [Ru(bpy)2 (bpy(PO3H2)2)]2+ (tpy is 2,2':6',2' '-terpyridine, bpy is 2,2'-bipyridine, and bpy(PO3H2)2 is 2,2'-bipyridyl-4,4'-diphosphonic acid), and on surfaces containing both complexes. This is an extension of earlier work on an adsorbed assembly containing both catalyst and chromophore. The experiments were carried out with the I3-/I- or quinone/hydroquinone (Q/H2Q) relays in propylene carbonate, propylene carbonate-water mixtures, and acetonitrile-water mixtures. Electrochemical measurements show that oxidation of surface-bound Ru(III)-OH2(3+) to Ru(IV)=O(2+) is catalyzed by the bpy complex. Addition of aqueous 0.1 M HClO4 greatly decreases photocurrent efficiencies for adsorbed [Ru(tpy)(bpy(PO3H2)2)(OH2)]2+ with the I3-/I- relay, but efficiencies are enhanced for the Q/H2Q relay in both propylene carbonate-HClO4 and acetonitrile-HClO4 mixtures. The dependence of the incident photon-to-current efficiency (IPCE) on added H2Q in 95% propylene carbonate and 5% 0.1 M HClO4 is complex and can be interpreted as changing from rate-limiting diffusion to the film at low H2Q to rate-limiting diffusion within the film at high H2Q. There is no evidence for photoelectrochemical cooperativity on mixed surfaces containing both complexes with the IPCE response reflecting the relative surface compositions of the two complexes. These results provide insight into the possible design of photoelectrochemical synthesis cells for the oxidation of organic substrates. 相似文献
9.
Saw LK Brooks BW Carpenter KJ Keight DV 《Journal of colloid and interface science》2004,279(1):235-243
Previous work has identified distinct regions, on a phase inversion map, for dispersions of polyurethane ionomer (PUI) and water. In this study, events that occur, before, during, and after catastrophic phase inversion (provoked by adding water to polyurethane ionomer (PUI) in the RII regions of the phase inversion map) have been studied in order to characterise the inversion mechanism. Before phase inversion, initial water addition leads to the hydration of ionic groups and eventually water drops start to form in the hydrophobic portions of the polymer matrix. At the phase inversion point, the PUI-water interface restructures and the ionomer disintegrates into a dispersion of spherical particles enclosed by a continuous aqueous phase. It is suggested that pseudo-drop structures are formed simultaneously during the production of the small polymer-in-water drops. After phase inversion, water addition dilutes the emulsion and destroys the apparent ionic-centre-rich environment surrounding any isolated ionic groups on a particle surface. The larger water-in-polymer drops are likely to have participated in the phase inversion and the smaller water drops form the primary water drops in the multiple emulsions. The resultant emulsions are stable over a period of a few months but very few multiple drops remain after 1(1/4) years. 相似文献
10.
A procedure for the determination of ruthenium in iron meteorites involves its oxidation to RuO4 by sodium periodate in hydrochloric acid and extraction of the tetroxide into chloroform. Various parameters of the method were studied: sample dissolution, optimum amount of oxidant, shaking time, distribution ratio and stability of the complex. The relative standard deviation assessed from replicate analyses of the North Chile iron meteorite was 6.6%. There are no certified standards for iron meteorites, but the value of 20.0 μg g? obtained for this meteorite compares well with a reported abundance of 19.3 μg g?1 obtained by radiometric neutron-activation analysis (RNAA). The analysis of 15 meteorites that had previously been analysed by RNAA gave values averaging 11% below those reported by the latter method, but within the standard deviation of the RNAA data. It is considered that the present method is a more practical alternative to RNAA for the determination of ruthenium in iron meteorites. 相似文献