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121.
We investigate the morphology of a pentacene (C22H14) film adsorbed on the Cu(1 1 9) vicinal surface by scanning tunnelling microscopy (STM). Thermal treatment of a thick film of molecules generates a long-range ordered structure. Series of molecular rows are alternated with areas where the molecules assume two equivalent orientations. STM data analysis suggests that the ordered structure can be described by a rippled morphology. The behaviour of the film at different annealing temperatures suggests a possible explanation of the film structure as due to an adsorbate-induced modification of the substrate. 相似文献
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Mattia Gazzola Philippe Chatelain Wim M. van Rees Petros Koumoutsakos 《Journal of computational physics》2011,230(19):7093-7114
We present a vortex particle method coupled with a penalization technique to simulate single and multiple swimmers in an incompressible, viscous flow in two and three dimensions. The proposed algorithm can handle arbitrarily deforming bodies and their corresponding non-divergence free deformation velocity fields. The method is validated on a number of benchmark problems with stationary and moving boundaries. Results include flows of tumbling objects and single and multiple self-propelled swimmers. 相似文献
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C.?ManninoEmail author S.?Mattia A.?Sassano 《Computational Optimization and Applications》2011,48(3):533-551
Transmitters and receivers are the basic elements of wireless networks and are characterized by a number of radio-electrical
parameters. The generic planning problem consists of establishing suitable values for these parameters so as to optimize some
network performance indicator. The version here addressed, namely the Power Assignment Problem (pap), is the problem of assigning transmission powers to the transmitters of a wireless network so as to maximize the satisfied
demand. This problem has relevant practical applications both in radio-broadcasting and in mobile telephony. Typical solution
approaches make use of mixed integer linear programs with huge coefficients in the constraint matrix yielding numerical inaccuracy
and poor bounds, and so cannot be exploited to solve large instances of practical interest. In order to overcome these inconveniences,
we developed a two-phase heuristic to solve large instances of pap, namely a constructive heuristic followed by an improving local search. Both phases are based on successive shortest path
computations on suitable directed graphs. Computational tests on a number of instances arising in the design of the national
Italian Digital Video Broadcasting (DVB) network are presented. 相似文献
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Elisabetta Canè Mattia Villa Riccardo Tarroni Andrea Pietropolli Charmet Nicola Tasinato 《Molecular physics》2014,112(14):1899-1909
The v4 fundamental band of CF379Br and CF381Br, present in natural isotopic abundance, was investigated in the 8.3-μm region by high-resolution infrared spectroscopic techniques. Tuneable diode laser spectra were recorded in the ranges 1202.5–1205.0 cm?1, 1208.0–1210.1 cm?1 and 1212.5–1214.5 cm?1. The tuneable diode laser spectra were obtained at the reduced temperature of 200 K and in a free-jet expansion. The latter technique was used to reduce spectral congestion, achieving a rotational temperature of about 50 K, with a resolution up to 0.0008 cm?1. A Fourier transform infrared spectrum covering the entire spectral region of the v4 band, between 1190 and 1220 cm?1, was recorded at 298 K with a resolution of 0.004 cm?1. The experimental wavenumbers from the different spectroscopic techniques were combined to accomplish the complete ro-vibrational analysis of v4. In total, 4651 transitions were assigned to CF379Br, 4047 to CF381Br, with J″max? = K″max?=80; of these, 3171 for CF379Br and 2755 for CF381Br are from diode laser measurements. The data of each isotopologue were analysed using the model Hamiltonian for a degenerate vibrational state of a molecule of C3v symmetry. The v4 band of both the isotopologues resulted essentially unperturbed, but the Δl = Δk = ±2 l-resonance was found to be active within the v4 = 1 state. Precise values of the vibrational energy and of the ro-vibrational parameters of v4 = 1 for CF379Br and CF381Br were obtained. The bromine isotopic splitting amounts to 6.9 × 10?3 cm?1. In addition, the equilibrium geometry and the harmonic force field were calculated ab initio using the large-size basis set def2-QZVP in conjunction to the PBE0 functional. 相似文献
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Xishan Bai Mattia Cettolin Giulia Mazzoccanti Marco Pierini Umberto Piarulli Valentina Colombo Alberto Dal Corso Luca Pignataro Cesare Gennari 《Tetrahedron》2019,75(10):1415-1424
In this paper, we describe a small library of easy-to-prepare chiral (cyclopentadienone)iron pre-catalysts for enantioselective CO and CN hydrogenations. Starting from readily accessible achiral materials, six chiral (cyclopentadienone)iron complexes (1a-f) possessing a stereogenic plane were synthesized in racemic form. Based on the screening of pre-catalysts (±)-1a-f in the hydrogenation of ketones and ketimines, we selected two complexes (1a and 1d) for resolution by semipreparative enantioselective HPLC. The absolute configuration of the separated enantiomers of 1a and 1d was assigned by XRD analysis (1a) and by comparison between experimental and DFT-calculated ECD and ORD spectra (1d). The enantiopure pre-catalysts (S)-1a and (R)-1d were tested in the asymmetric hydrogenation of several ketones and ketimines and showed good activity and modest enantioselectivity, the e.e. values ranging from very low to moderate (54%). 相似文献