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61.
Krzysztof Augustynek Iwona Adamiec-Wójcik 《Archive of Applied Mechanics (Ingenieur Archiv)》2012,82(2):283-295
The paper presents a method of modelling dynamics of mechanisms in which assembly errors can occur. One of the features of
the method is that such errors can be included when the kinematics of the mechanism is modelled. A closed kinematic chain
consisting of flexible and rigid links with one joint displaced and turned is discussed. Use of joint coordinates together
with the rigid finite element method for discretisation of flexible links has allowed us to considerably decrease the size
of the problem. Numerical simulations are carried out in order to analyse the influence of inaccurate assembly on the load
on joints of a four-bar linkage. 相似文献
62.
Zygfryd Smiatacz Eugenia Paszkiewicz Iwona Chrzczanowicz 《Journal of carbohydrate chemistry》2013,32(3):315-327
ABSTRACT 3,6-Di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-2-deoxy-2-hydroxyimino-α- and -β-D-arabino-hexopyranosides of N-benzyloxycarbonyl-L-serine methyl ester as well as of ethanol have been synthesised from D-lactal hexaacetate via nitrosyl chloride, followed by condensation with L-serine derivatives and ethanol, respectively. The compounds of L-serine thus obtained were modified at C-2 and C-3 to afford L-serine derivatives attached to disaccharides containing terminal α-D-gluco-, 2-acetamido-α-D-gluco-, β-D-manno, 2-acetamido-β-D-manno-pyranosyl, 3-azido-2-hydroxyimino-α-D-arabino-, and α-D-ribo-hexopyranosyl residues. 相似文献
63.
Janusz Zachara Izabela D. Madura Andrzej Zimniak Irena Oszczapowicz Iwona Chrobak 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(11):o625-o627
The structural analysis of deacetylcephalothin [systematic name: (6R,7R)‐3‐hydroxymethyl‐8‐oxo‐7‐(2‐thiophen‐2‐ylacetylamino)‐5‐thia‐1‐azabicyclo[4.2.0]oct‐2‐ene‐2‐carboxylic acid], C14H14N2O5S2, shows that the geometry of the central bicyclic moiety is close to the geometry exhibited by other biologically active cephalosporin antibiotics. The molecules are arranged in a helical chain running parallel to the 21 axis via a strong O—H⋯O hydrogen bond. The main helices are zipped together via N—H⋯O interactions, forming infinite layers. The supramolecular architecture is stabilized by O—H⋯S and C—H⋯O hydrogen bonds. 相似文献
64.
Romana Anulewicz Iwona Wawer Boguslawa Piekarska-Bartoszewicz Andrzej Temeriusz 《Journal of carbohydrate chemistry》2013,32(6):617-628
ABSTRACT The X-ray diffraction analysis of methyl 3,4,6-tri-O-acetyl-2-deoxy-(3-phenylureido)-β-D-glucopyranoside was performed and showed that the molecules are associated by two NHz.O=C hydrogen bonds. One molecule with disorder of an acetyl group at C-4 was found in the asymmetric crystal unit. The signals in 13C CPMAS NMR spectrum are duplicated indicating that local symmetry is lower than those of the crystal. 相似文献
65.
Maria Chrzanowska Agnieszka Grajewska Zofia Meissner Maria Rozwadowska Iwona Wiatrowska 《Tetrahedron》2012,68(14):3092-3097
A sequence of two reactions: the Petasis reaction, in which an aminoacetaldehyde acetal was used as the amine component, followed by Pomeranz–Fritsch–Bobbitt cyclization, has been shown to be a convenient and simple method for the synthesis of tetrahydroisoquinoline-1-carboxylic acids. Using this method several acids have been prepared in good to excellent yields and characterized as hydrochloride salts. 相似文献
66.
The title complex, denoted as [Cu(Msap)2], is a deep brown solid soluble in common solvents like chloroform, toluene, benzene, dioxane, acetone, methanol, ethanol,
2-propanol, dimethylformamide, dimethyl sulfoxide, and acetonitrile that is a necessary condition for solvatochromism observation.
The complex has been characterized by elemental analysis, molar conductivity, ultraviolet, and visible spectroscopy. The available
X-ray data for similar compounds show that copper atom adopts planar coordination geometry. The molar conductivities indicate
their non-electrolytic properties. The electronic spectra have been used to study the coordination properties of donor atoms
and their bonding abilities, as well as solvatochromism. The results obtained show that the interactions of metal with donors
depend on solvent polarity and the color changes are subtle. 相似文献
67.
68.
Marcin Kubisiak Karolina Zelga Wojciech Bury Iwona Justyniak Krzysztof Budny-Godlewski Zbigniew Ochal Janusz Lewiński 《Chemical science》2015,6(5):3102-3108
This paper reports a series of comparative experiments on the activity of carbon- and oxygen-centred radical species in a model reaction of the radical addition of THF to imines mediated by a series of zinc alkyl/air reaction systems. The study strongly contradicts the notion that generally R˙ radicals are the initiating species in organic reactions mediated by RnM/air systems, and simultaneously demonstrates that oxygen-centred radical species are the key intermediates responsible for the initiation process. In addition, a new efficient RZn(L)/air initiating system for radical organic reactions exampled by a model reaction of radical addition of THF to imines is developed. Moreover, the isolation and structural characterization of the first zinc alkylperoxide supported by a carboxylate ligand, [Zn4(μ3-OOtBu)3(μ4-O)(O2CEt)3]2, as well as the novel octanuclear zinc oxo(alkoxide) aggregate with entrapped O–THF species, [Zn4(μ4-O)(μ3-2-O–THF)(O2CEt)5]2, provide clear mechanistic signatures for the mode of function of the RZn(O2CR′)/air system. 相似文献
69.
Tomasz Pospieszny Marta Pakiet Iwona Kowalczyk Bogumił Brycki 《Supramolecular chemistry》2017,29(2):81-93
New dimers have been obtained from propargyl ester of bile acids and α,α′-diazide-m-xylene by intermolecular 1,3-dipolar cycloaddition. These compounds have been used as ligands to form intermolecular hydrogen bonds with various aromatic acids. The structures of all products were confirmed by spectroscopic (1H NMR, 13C NMR and FT-IR) analysis, mass spectrometry (ESI, MALDI) and PM5 semiempirical methods. 相似文献
70.
Krzysztof Dȩbicki Peng Liu Michel Mandjes Iwona Sierpińska-Tułacz 《Queueing Systems》2017,85(3-4):249-267
In this paper, we derive exact large buffer asymptotics for a two-class generalized processor sharing (GPS) model, under the assumption that the input traffic streams generated by both classes correspond to heavy-tailed Lévy processes. Four scenarios need to be distinguished, which differ in terms of (i) the level of heavy-tailedness of the driving Lévy processes as well as (ii) the values of the corresponding mean rates relative to the GPS weights. The derived results are illustrated by two important special cases, in which the queues’ inputs are modeled by heavy-tailed compound Poisson processes and by \(\alpha \)-stable Lévy motions. 相似文献