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421.
422.
Klaus Mayer Maria Wallenius Klaus Lützenkirchen Joan Horta Adrian Nicholl Gert Rasmussen Pieter vanBelle Zsolt Varga Razvan Buda Nicole Erdmann Jens‐Volker Kratz Norbert Trautmann L. Keith Fifield Stephen G. Tims Michaela B. Frhlich Peter Steier 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(45):13654-13658
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Anastasia Grishina Dr. Stancho Stanchev Lukáš Kumprecht Dr. Miloš Buděšínský Dr. Michaela Pojarová Dr. Michal Dušek Dr. Michaela Rumlová Ivana Křížová Dr. Lubomír Rulíšek Dr. Tomáš Kraus 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12292-12304
New tubular host molecules, which are composed of two β‐cyclodextrin macrocycles that are connected through two disulfide bonds, have been prepared by the air‐promoted oxidation of 6I,6IV‐dideoxy‐6I,6IV‐disulfanyl‐β‐cyclodextrin in aqueous solution. This reaction leads to three products: monomeric intramolecular disulfide and two dimeric species, which are termed as “non‐eclipsed” and “eclipsed” cyclodextrin duplexes. Oxidation at a concentration of the starting thiol of 0.1 mM gave the intramolecular disulfide as the major product whereas a concentration in the millimolar range afforded the dimeric species as the dominant products. The tubular structure of the “non‐eclipsed” isomer was unequivocally determined by X‐ray analysis. The binding affinities of the duplexes to a wide range of compounds, including fluorescent dyes and clinically used drugs Imatinib and Esomeprazol, were studied in water by ITC. For most guest compounds, the experimentally determined Ka values were in the range 107–108 M ?1. These binding affinities are significantly higher than those found in the literature for analogous complexes with native cyclodextrins. In cases of binding of neutral or anionic guest molecules cyclodextrin duplexes outperformed cucurbiturils. A complex between a duplex and Nile blue was used to investigate its ability to penetrate the cytoplasmic membrane of HeLa cells. We found that the complex accumulated in the cell membrane but did not pass into cytosol. Importantly, the complex did not decompose to a significant extent under high dilution in the cellular environment. 相似文献
425.
Dr. Samy Cecioni Dr. Jean‐Pierre Praly Dr. Susan E. Matthews Dr. Michaela Wimmerová Dr. Anne Imberty Dr. Sébastien Vidal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(20):6250-6263
The design of multivalent glycoclusters requires the conjugation of biologically relevant carbohydrate epitopes functionalized with linker arms to multivalent core scaffolds. The multigram‐scale syntheses of three structurally modified triethyleneglycol analogues that incorporate amide moiety(ies) and/or a phenyl ring offer convenient access to a series of carbohydrate probes with different water solubilities and rigidities. Evaluation of flexibility and determination of preferred conformations were performed by conformational analysis. Conjugation of the azido‐functionalized carbohydrates with tetra‐propargylated core scaffolds afforded a library of 18 tetravalent glycoclusters, in high yields, by CuI‐catalyzed azide–alkyne cycloaddition (CuAAC). The compounds were evaluated for their ability to bind to PA‐IL (the LecA lectin from the opportunistic pathogen Pseudomonas aeruginosa). Biochemical evaluation through inhibition of hemagglutination assays (HIA), enzyme‐linked lectin assays (ELLA), surface plasmon resonance (SPR), and isothermal titration microcalorimetry (ITC) revealed improved and unprecedented affinities for one of the monovalent probes (Kd=5.8 μM ) and also for a number of the tetravalent compounds that provide several new nanomolar ligands for this tetrameric lectin. 相似文献
426.
427.
Iridium Catalyzed Carbocyclizations: Efficient (5+2) Cycloadditions of Vinylcyclopropanes and Alkynes
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Michaela‐Christina Melcher Henrik von Wachenfeldt Anders Sundin Prof. Daniel Strand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):531-535
Third‐row transition metal catalysts remain a largely untapped resource in cycloaddition reactions for the formation of medium‐sized rings. Herein, we report the first examples of iridium‐catalyzed inter‐ and intramolecular vinylcyclopropane (VCP)–alkyne (5+2) cycloadditions. DFT modeling suggests that catalysis by iridium(I) proceeds through a mechanism similar to that previously reported for rhodium(I)‐catalyzed VCP–alkyne cycloadditions, but a smaller free energy span for iridium enables substantially faster catalysis under favorable conditions. The system is characterized by up to quantitative yields and is amenable to an array of disubstituted alkynes and vinylcyclopropanes. 相似文献
428.
Diffusive equilibrium (DET) and diffusive gradient in thin film (DGT) techniques with an inductively coupled plasma mass spectrometry detection of elements were applied to characterize uranium, manganese, iron and 238U/235U isotopic ratio depth profiles in sediment pore water at high spatial resolution and to monitor uranium uptake/remobilization processes in uranium spiked sediment core samples under laboratory, well controlled conditions. Modified constrained sediment DGT probes, packed with Spheron-Oxin® resin gel, were employed for selective uranium measurements. Spatially resolved DET and DGT responses were indicative of local redistribution of uranium in naturally uranium poor and rich sediments. 相似文献
429.
Lenka Malinová Michaela Stolínová Daniela Lubasová Lenka Martinová Jiří Brožek 《European Polymer Journal》2013
The paper is focused on the preparation of nanofiber layers of polyesteramides with various ratios of ε-caprolactam/ε-caprolactone structural units. We have studied the effect of the system parameters, i.e., the composition of the copolymer, its molar mass and the concentration of the solution on morphology of fiber layers being formed during the electrostatic wet spinning. The process parameters were constant during the processing. Morphology of the fiber layers is given by the composition of the copolymer, i.e., by its polarity, the content of the crystalline phase and thus its separation in the process of evaporating the solvent. Fibers with diameters ranging from 100 to 160 nm were obtained for polyesteramides containing 20 or 40 mol% lactone units during optimizing the system parameters, i.e., the concentration of the solution and molar mass of polyesteramide. 相似文献
430.
Felix Diewald Charlotte Kuhn Ricardo Blauwhoff Michaela Heier Stefan Becker Stephan Werth Martin Horsch Hans Hasse Ralf Müller 《PAMM》2016,16(1):519-520
In the proposed phase field model a continuous order parameter indicates the phase distribution (liquid/gas). An energy density functional which is dependent on the surface tensions and defined by three contributions yields the total energy of the system. An equilibrium state is then computed by minimizing this energy of the system using an evolution equation. Details of the algorithmic implementation are discussed by illustrative examples. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献