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91.
Most mesogens formed by banana-shaped molecules exhibit liquid-like smectic phases. Here we present the synthesis and properties of homologous series of derivatives of resorcinol and 2,6-disubstituted pyridine. One of these classes of bent-core molecules displays the nematic phase. 相似文献
92.
Krzysztof Łapsa Agnieszka Marcinkowska Adam Rachocki Ewa Andrzejewska Jadwiga Tritt‐Goc 《Journal of Polymer Science.Polymer Physics》2010,48(12):1336-1348
The influence of the viscosity of a two‐component system on its molecular dynamics (on the basis of hypersonic wave velocity and attenuation coefficient) and photopolymerization kinetics was studied. The system investigated represented the solution of poly(benzyl methacrylate), PBzMA (MW = 70000) in its monomer, benzyl methacrylate (BzMA). The viscosity of the system was varied by adding various amounts of the polymer to the monomer (10–50 wt %). The molecular dynamics in the neat BzMA was studied by the proton Nuclear Magnetic Resonance (NMR) spin‐lattice relaxation time measurements and the wide‐line 1H NMR spectroscopy in a wide range of temperature. Information on the local dynamics in liquid BzMA above its melting temperature was gained from the high‐resolution 1H and 13C NMR spectra. The hypersonic wave velocity and the attenuation coefficient were investigated in the appropriate temperature range related to a viscoelastic relaxation process by the Brillouin light scattering method. The kinetic measurements have demonstrated that the photopolymerization rate rapidly increases and the monomer conversion decreases with increasing polymer‐to‐monomer ratio; this effect has been noted in the whole range of polymer concentration and reaction temperature studied. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1336–1348, 2010 相似文献
93.
Yuriy Trach Oksana Makota Jadwiga Skubiszewska-Zięba Tadeusz Borowiecki Roman Leboda 《Transition Metal Chemistry》2010,35(3):345-348
Disilicides of molybdenum, tungsten, tantalum, and titanium were studied using FTIR spectroscopy to establish the origin of
their different catalytic activities in the decomposition of tert-butyl hydroperoxide. The FTIR spectra of the metal disilicides before and after the decomposition reaction show that their
different catalytic activities are caused not only by the nature of the transition metal, but also by different abilities
of their surfaces to adsorb water. The increase in the catalyst’s ability to adsorb water leads to a decrease in catalyst
activity. 相似文献
94.
Wojciech Szczolko Lukasz Sobotta Piotr Fita Tomasz Koczorowski Michal Mikus Maria Gdaniec Aleksandra Orzechowska Kvetoslava Burda Stanislaw Sobiak Marcin Wierzchowski Jadwiga Mielcarek Ewa Tykarska Tomasz Goslinski 《Tetrahedron letters》2012,53(16):2040-2044
The synthesis and physicochemical properties of novel porphyrazines possessing an alternate system of two peripheral substituents, 2,5-dimethylpyrrol-1-yl and dimethylamino, are presented. All the macrocycles were subjected to HPLC purity studies. Spectroscopic studies of magnesium(II) porphyrazine encompassed steady state absorption, emission measurements, including fluorescence decays, transient absorption spectra, and thermoluminescence. Additionally, magnesium(II) porphyrazine was found to be a moderate photosensitizer with singlet oxygen generation values of 0.12 and 0.14 in DMF and DMSO, respectively. Comparison of the quantum yields of singlet oxygen generation before and after deoxygenation showed that the photodynamic effect of magnesium(II) porphyrazine is governed by the photosensitization mechanism II. Magnesium(II) and manganese(III) porphyrazines were characterized using X-ray crystallography. 相似文献
95.
Jadwiga Nowak Izabela Poplewska Dorota Antos Andreas Seidel-Morgenstern 《Journal of chromatography. A》2009,1216(50):8697-8704
In this work the activity of three carbohydrates (sucrose, glucose and fructose) in highly concentrated aqueous solutions was studied along with its effect on the adsorption behaviour of the investigated compounds. Activities of individual sugars in aqueous solutions of single solute as well as in binary mixtures were quantified on the basis of solubility properties. Solid–liquid equilibria of sugars were correlated with the NRTL (nonrandom, two liquid) model of activity coefficient formulation. Activities of individual sugars were incorporated into the single component adsorption isotherm model, which reproduced accurately the course of the adsorption equilibria of sugars in aqueous solutions obtained experimentally in previous work using an ion-exchange resin. Activities of sugars determined in binary solute systems along with the single component isotherms were used to predict competitive adsorption equilibria. To calculate adsorbed phase concentrations of individual sugars in binary mixtures the adsorbed solution theory was adopted. The isotherm shapes calculated were compared to the data of competitive adsorption from the former study and found to be able to describe these experimental results. 相似文献
96.
Jadwiga Szydłowska Dr. Adam Krówczyński Dr. Damian Pociecha Dr. Jacek Szczytko Dr. Paweł Budzowski Andrzej Twardowski Prof. Ewa Górecka Prof. 《Chemphyschem》2010,11(8):1735-1741
Herein, two new groups of isomeric bimetallic nickel(II) and copper(II) complexes containing pyrazine or pyrimidine rings are synthesized and examined. The complexes exhibit liquid‐crystalline columnar phases in a broad temperature range. For the copper(II) complexes, super‐exchange coupling between two CuII ions is observed. For the pyrimidine derivative in which the paramagnetic CuII ions are separated only by three atoms, an antiferromagnetic spin alignment is detected. When the distance between CuII ions increases to four atoms in the pyrazine derivative, the magnetic interaction becomes significantly weaker. 相似文献
97.
Doskocz J Doskocz M Roszak S Soloducho J Leszczynski J 《The journal of physical chemistry. A》2006,110(51):13989-13994
Structures, electron ionization and excitation energies, and electron density distribution are studied for carbazole and fluorene derivatives substituted symmetrically by thiophene, ethylenodioxythiophene, furane, or pyrrole. The calculated properties of the molecules directly or indirectly mimic molecular parameters that are important for the design of processes of polymerization or for modeling the final polymer. The studies have been focused on the variation in the properties as a function of the chemical composition of the central fragment and the external rings. The calculated properties of consecutive oligomers indicate their fast convergence to values characterizing polymers. 相似文献
98.
Jadwiga Frelek Zbigniew Pakulski Aleksander Zamojski 《Journal of carbohydrate chemistry》2013,32(4-5):625-639
Abstract Heptofuranose derivatives 1–6 having free 1, 3-diol systems form in situ complexes with Mo2(OAc)4 whose CD spectra permit the assignment of absolute configuration at C-5 using a sector rule proposed by G. Snatzke.2–6 The interpretation of CD spectra of analogous complexes formed from derivatives 7–12 was more complicated and did not lead to direct configuralional conclusions. CD spectra of complexes formed from Rh2(CF3COO)4 and sugar derivatives 13–21, containing an “isolated” hydroxyl group, permit the assignment of absolute configuration. Conclusions were corroborated by the investigation of CD spectra of rhodium complexes with compounds 22–27. 相似文献
99.
Jadwiga Szyd owska Adam Kr wczy ski Urszula Pietrasik Agnieszka Rogowska 《Liquid crystals》2005,32(5):651-658
Mesogenic tetradentate cis-enaminoketone Ni(II), Cu(II) and VO(II) complexes with rod-like and disc-like molecular shapes were synthesized. In these compounds some of the alkyl chains were perfluorinated. Replacing the alkyl chains by fluorinated chains stabilizes the columnar hexagonal Colh phase whereas lamellar phases are destroyed. 相似文献
100.