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21.
Owen S. Skinner Kathrin Breuker Fred W. McLafferty 《Journal of the American Society for Mass Spectrometry》2013,24(6):807-810
A conventional electron capture dissociation (ECD) spectrum of a protein is uniquely characteristic of the first dimension of its linear structure. This sequence information is indicated by summing the primary c m+ and z m+? products of cleavage at each of its molecular ion’s inter-residue bonds. For example, the ECD spectra of ubiquitin (M?+?nH)n+ ions, n?=?7–13, provide sequence characterization of 72 of its 75 cleavage sites from 1843 ions in seven c (1–7)+ and eight z (1–8)+? spectra and their respective complements. Now we find that each of these c/z spectra is itself composed of “charge site (CS)” spectra, the c m+ or z m+? products of electron capture at a specific protonated basic residue. This charge site has been H-bonded to multiple other residues, producing multiple precursor ion forms; ECD at these residues yields the multiple products of that CS spectrum. Closely similar CS spectra are often formed from a range of charge states of ubiquitin and KIX ions; this indicates a common secondary conformation, but not the conventional α-helicity postulated previously. CS spectra should provide new capabilities for comparing regional conformations of gaseous protein ions and delineating ECD fragmentation pathways. Figure
? 相似文献
22.
2,3-Dichloroquinoline was prepared in three steps in good overall yield from commercial 3-bromoquinoline via N-oxide formation and rearrangement to 3-bromocarbostyril, followed by a one-pot conversion to 3-bromo-2-chloroquinoline and halogen exchange to the title compound. 相似文献
23.
Siegfried E. Drewes Owen L. Njamela Neville D. Emslie Niyum Ramesar John S. Field 《合成通讯》2013,43(20):2807-2815
The acrylate ester of salicylaldehyde, in the presence of DABCO, affords a crystalline coumarin salt. Formation of this derivative confirms a vital intermediate in the mechanism of the reaction. Salicylaldehyde, suitably protected, reacts with methyl acrylate to afford a novel coumarin not unlike the vasodilator chromonar. 相似文献
24.
We study the dynamics of patterns exhibited by rule 52, a totalistic cellular automaton displaying intricate behaviors and wide regions of active/inactive synchronization patches. Systematic computer simulations involving 2(30) initial configurations reveal that all complexity in this automaton originates from random juxtaposition of a very small number of interfaces delimiting active/inactive patches. Such interfaces are studied with a sidewise spatial updating algorithm. This novel tool allows us to prove that the interfaces found empirically are the only interfaces possible for these periods, independently of the size of the automata. The spatial updating algorithm provides an alternative way to determine the dynamics of automata of arbitrary size, a way of taking into account the complexity of the connections in the lattice. 相似文献
25.
Owen W. Webster 《Macromolecular Symposia》1994,77(1):177-182
The water soluble tritriptycene 1 was synthesized starting with triptycene trisquinone and anthracene. The hydrophobic binding of substrates to the benzene-walled cavities in 1 was studied by noting the up-field shift of substrate protons in the NMR of the substrate in the presence of aqueous 1. Small substrates, negatively charged substrates or substrates larger than the cavities do not bind as strongly as substrates about the same size as the cavities or those bearing a positive charge. Based on differences in AHz'S, the bound substrates position themselves in the cavities so that polar groups are at the water interface. 相似文献
26.
Substituted μ3-carbido-capped tricobalt carbonyl clusters have been synthesised by reaction of [Co3(μ3-C(O)OCH2CHCH2)(CO)9] with a range of monodentate and chelating phosphane ligands. The products have been characterised by microanalysis, IR and NMR spectroscopy, mass spectrometry and, in the case of [Co3(μ3-CR)(CO)7(dppe)], [Co3(μ3-CR)(CO)7(dppm)], [Co3(μ3-CR)(CO)7(PPh3)2], [Co3(μ3-CR)(CO)7(PMe3)2] and [Co3(μ3-CR)(CO)6(PEt3)3] (R=C(O)OCH2CHCH2), single crystal X-ray diffraction. 相似文献
27.
The pressure-flow characteristics of a Zobel-type vortex diode have been measured using a working fluid of compressible wet steam. Tests using superheated steam with inlet/outlet pressure ratios across the diode of up to 30 have shown clearly the effects of compressibility and choking on the diode characteristics. Repeating the tests using wet steam, with known dryness fractions, has shown separately the effects of wetness on the diode performance.
When the diode was installed into the pipwork in the high-resistance direction, excessive steam wetness (quality <0.93) led to a build-up of water and when this was eventually swept through to the diode the resistance was seen to fall substantially as the strong internal vortex was destroyed. 相似文献
28.
C.R. Leonardi D.R.J. Owen Y.T. Feng 《ournal of non Newtonian Fluid Mechanics》2011,166(12-13):628-638
In the present study, the flow of bulk materials is characterised as a non-Newtonian fluid and modelled using the lattice Boltzmann method. A power law and a Bingham model is implemented in the LBM, which is hydrodynamically coupled to the discrete element method (DEM) for structural interaction. The performance of both non-Newtonian models is assessed, both qualitatively and quantitatively, in benchmark problems. The validated, non-Newtonian LBM–DEM framework is then applied to the geometry of a cylindrical Couette rheometer to numerically determine the constitutive response of a sample of Leighton Buzzard sand. The numerical results, which employ the power law, are compared with experimental data, and a number of other synthetic soil samples are defined using the presented process of numerical rheometry. Finally, the numerical stress–strain rate response of the synthetic soil samples is interpreted within the context of a regularised Bingham model, and the similarities discussed. 相似文献
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