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81.
82.
Vanida Choomuenwai Brett D. Schwartz Karren D. Beattie Katherine T. Andrews Shahan Khokhar Rohan A. Davis 《Tetrahedron letters》2013
Bioassay-guided fractionation of an antimalarial extract derived from the fungus Ramaria subaurantiaca afforded the known polyamine alkaloid, pistillarin. Nine pistillarin analogues were synthesised via EDC-mediated chemistry and these compounds along with the previously reported natural product polyamines, ianthelliformisamines A–C and spermatinamine, were evaluated against Plasmodium falciparum (3D7) parasites and a normal human cell line to determine parasite-specific activity. Spermatinamine (IC50 0.23 μM) and pistillarin (IC50 1.9 μM) were the two most potent antimalarials identified during these studies. 相似文献
83.
Synthesis of a key precursor 2-allyl-3-bromo-1,4-dimethoxynaphthalene (1) used in constructing various naturally occurring biologically active pyranonaphthoquinones is carried out utilizing easily available 1-methoxynaphthalene as a starting material. The synthesis was accomplished with Dakin's oxidation and Claisen rearrangement, thereby providing another easy approach toward (1) without involving highly lachrymatric 2-bromonaphthoquinone. 相似文献
84.
A notion of material stability is introduced and discussed in the setting of nonlinear thermoelasticity. Necessary and sufficient
conditions are established for the stability of a general thermoelastic material. The adiabatic theory and the theory that
accounts for heat conduction are considered separately.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
85.
The paper deals with analysis of the elastic waves in the Reissner-Mindlin type of plates formed by strongly heterogeneous structures. The homogenized plate model involves frequency-dependent mass coefficients associated with the plate cross-section rotations and the plate deflections. Intervals of frequencies called band gaps exist for which these coefficients constituting a mass matrix can be negative, so that certain wave modes cannot propagate. A spectral decomposition based method is proposed which is suitable to compute the plate response for an external loading by periodic forces with frequencies in range of the band gaps. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
86.
Pulse Radiolysis and Ultra‐High‐Performance Liquid Chromatography/High‐Resolution Mass Spectrometry Studies on the Reactions of the Carbonate Radical with Vitamin B12 Derivatives 下载免费PDF全文
Rohan S. Dassanayake Dr. Jacob T. Shelley Dr. Diane E. Cabelli Dr. Nicola E. Brasch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6409-6419
The reactions of the carbonate radical anion (CO3 . ?) with vitamin B12 derivatives were studied by pulse radiolysis. The carbonate radical anion directly oxidizes the metal center of cob(II)alamin quantitively to give hydroxycobalamin, with a bimolecular rate constant of 2.0×109 M ?1 s?1. The reaction of CO3 . ? with hydroxycobalamin proceeds in two steps. The second‐order rate constant for the first reaction is 4.3×108 M ?1 s?1. The rate of the second reaction is independent of the hydroxycobalamin concentration and is approximately 3.0×103 s?1. Evidence for formation of corrinoid complexes differing from cobalamin by the abstraction of two or four hydrogen atoms from the corrin macrocycle and lactone ring formation has been obtained by ultra‐high‐performance liquid chromatography/high‐resolution mass spectrometry (UHPLC/HRMS). A mechanism is proposed in which abstraction of a hydrogen atom by CO3 . ? from a carbon atom not involved in the π conjugation system of the corrin occurs in the first step, resulting in formation of a CoIII C‐centered radical that undergoes rapid intramolecular electron transfer to form the corresponding CoII carbocation complex for about 50 % of these complexes. Subsequent competing pathways lead to formation of corrinoid complexes with two fewer hydrogen atoms and lactone derivatives of B12. Our results demonstrate the potential of UHPLC combined with HRMS in the separation and identification of tetrapyrrole macrocycles with minor modifications from their parent molecule. 相似文献
87.
Saran Dayal Sagar Rohan Gaur Mulayam Singh 《Journal of Thermal Analysis and Calorimetry》2019,136(4):1687-1687
Journal of Thermal Analysis and Calorimetry - In the original publication of the article, Tables 1 and 2 were swapped. The correct versions are given below. The original article has been... 相似文献
88.
Eduard Rohan Salah Naili Thibault Lemaire 《Continuum Mechanics and Thermodynamics》2016,28(5):1263-1293
We propose a model of complex poroelastic media with periodic or locally periodic structures observed at microscopic and mesoscopic scales. Using a two-level homogenization procedure, we derive a model coherent with the Biot continuum, describing effective properties of such a hierarchically structured poroelastic medium. The effective material coefficients can be computed using characteristic responses of the micro- and mesostructures which are solutions of local problems imposed in representative volume elements describing the poroelastic medium at the two levels of heterogeneity. In the paper, we discus various combinations of the interface between the micro- and mesoscopic porosities, influence of the fluid compressibility, or solid incompressibility. Gradient of porosity is accounted for when dealing with locally periodic structures. Derived formulae for computing the poroelastic material coefficients characterize not only the steady-state responses with static fluid, but are relevant also for quasistatic problems. The model is applicable in geology, or in tissue biomechanics, in particular for modeling canalicular-lacunar porosity of bone which can be characterized at several levels. 相似文献
89.
Physically cross-linked, fibrillar hydrogel networks are formed by the self-assembly of β-hairpin peptide molecules with varying degrees of strand asymmetry. The peptide registry in the self-assembled state can be used as a design element to generate fibrils with twisting, nontwisting, or laminated morphology. The mass density of the networks varies significantly, and can be directly related to the local fibrillar morphology as evidenced by small angle neutron scattering (SANS) and in situ substantiation using cryogenic transmission electron microscopy (cryo-TEM) under identical concentrations and conditions. Similarly, the density of the network is dependent on changes in the peptide concentration. Bulk rheological properties of the hydrogels can be correlated to the fibrillar nanostructure, with the stiffer, laminated fibrils forming networks with a higher G' as compared to the flexible, singular fibrillar networks. 相似文献
90.
Rohan J. Kumar Dr. Susanne Karlsson Daniel Streich Alice Rolandini Jensen Michael Jäger Dr. Hans‐Christian Becker Dr. Jonas Bergquist Prof. Olof Johansson Dr. Leif Hammarström Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(9):2830-2842
The first examples of rodlike donor–photosensitizer–acceptor arrays based on bis‐2,6‐di(quinolin‐8‐yl)pyridine RuII complexes 1 a and 3 a for photoinduced electron transfer have been synthesized and investigated. The complexes are synthesized in a convergent manner and are isolated as linear, single isomers. Time‐resolved absorption spectroscopy reveals long‐lived, photoinduced charge‐separated states (τCSS ( 1 a )=140 ns, τCSS ( 3 a )=200 ns) formed by stepwise electron transfer. The overall yields of charge separation (≥50 % for complex 1 a and ≥95 % for complex 3 a ) are unprecedented for bis‐tridentate RuII polypyridyl complexes. This is attributed to the long‐lived excited state of the [Ru(dqp)2]2+ complex combined with fast electron transfer from the donor moiety following the initial charge separation. The rodlike arrangement of donor and acceptor gives controlled, vectorial electron transfer, free from the complications of stereoisomeric diversity. Thus, such arrays provide an excellent system for the study of photoinduced electron transfer and, ultimately, the harvesting of solar energy. 相似文献