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101.
A study of the influence of cationic Na+ substitution in the archetype KMnF3 perovskite crystal was performed using the Raman method. The Raman spectra of mixed K1-xNaxMnF3 crystals with x = 0.029, 0.048 and 0.065 were recorded versus temperature and fully interpreted in terms of a “one mode” behaviour. In addition to the soft mode not completely vanishing close to Tc, attention was especially paid to evidence of static and dynamical disorder. From this point of view the behaviour of the hard Raman modes versus temperature has been studied together with two unexpected Raman bands in the cubic phase. The interpretation has been made within the more general framework of structural disorder existing in such perovskites with anisotropic interactions. 相似文献
102.
Jaworska Alicja 《Central European Journal of Mathematics》2007,5(4):665-685
Trivial extensions of a certain subclass of minimal 2-fundamental algebras are examined. For such algebras the characterization
of components of the Auslander-Reiten quiver which contain indecomposable projective modules is given.
相似文献
103.
Alicja Bory?o Bogdan Skwarzec Jacek Fabisiak 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):165-172
In the paper was presented results of our study about uranium 234U and 238U radioactivity in the marine birds samples, collected in the Polish area of the southern Baltic Sea. We chose 11 species
of sea birds: three species permanently residing at southern Baltic, four species of wintering birds and three species of
migrating birds. The obtained results indicated that uranium is very irregularly distributed in organs and tissues of marine
birds. The highest uranium content is characterized in liver, rest of viscera and feathers, the smallest in skin and muscles.
The uranium concentration was higher for carnivorous species (long-tailed duck (C. hyemalis), common eider (S. mollissima), lower for species eating fish (great cormorant (P. carbo), common guillemot (U. aalge), red-throated diver (G. stellata) and razorbill (A. tarda)), but the biggest amounts for herbivorous species [tufted duck (A. fuligula) and eurasian coot (F. atra)]. About 63–67% of uranium, which was located in feathers of two species of marine birds: razorbill (A. tarda) and long-tailed duck (C. hymealis), was apparently adsorbed, which suggests that uranium adsorption on the feathers may be an important transfer from air to
water. 相似文献
104.
Krystyna Czaja Marzena Biaek Alicja Utrata 《Journal of polymer science. Part A, Polymer chemistry》2004,42(10):2512-2519
The study of ethylene/1‐hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2)/methylaluminoxane (MAO), anchored on a MgCl2(THF)2 support was carried out. The influence of 1‐hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethlaluminum (AlMe3), or diethylaluminum chloride (Et2AlCl)] on the behavior of the MgCl2(THF)2/Cp2ZrCl2/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp2ZrCl2 compound on the complex magnesium support MgCl2(THF)2 resulted in an effective system for the copolymerization of ethylene with 1‐hexene. The modification of the support as well as the kind of organoaluminum compound used as a modifier influenced the activity of the examined catalyst system. Additionally, the profitable influence of immobilization of the homogeneous catalyst as well as modification of the support applied on the molecular weight and molecular weight distribution of the copolymers was established. Finally, with the successive self‐nucleation/annealing procedure, the copolymers obtained over both homogeneous and heterogeneous metallocene catalysts were heterogeneous with respect to their chemical composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2512–2519, 2004 相似文献
105.
106.
Hydrogen‐deuterium exchange of α‐carbon protons and fragmentation pathways in N‐methylated glycine and alanine‐containing peptides derivatized by quaternary ammonium salts 下载免费PDF全文
Remigiusz Bąchor Magdalena Rudowska Alicja Kluczyk Piotr Stefanowicz Zbigniew Szewczuk 《Journal of mass spectrometry : JMS》2014,49(6):529-536
Recently, we developed a selective and efficient method of hydrogen‐deuterium exchange (HDX) at the α‐carbon (α‐C) of sarcosine residue (N‐methylglycine) in model peptides [B?chor et al. J. Mass Spectrom. 2014, 49, 43]. Here, we report the influence of quaternary ammonium (QA) group on HDX at the α‐C of sarcosine and N‐methylalanine in peptides. The obtained results suggest a significant acceleration of the HDX in sarcosine residue caused by the presence of QA. The effect depends on the distance between the sarcosine residue and QA moiety. The deuterons, introduced at α‐C, are resistant to the back‐exchange in acidic aqueous solution. The collision induced dissociation of the deuterium‐labeled analogs of QA‐tagged oligosarcosine peptides without mobile hydrogen revealed the mobilization of the hydrogens localized at α‐C of sarcosine residue. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
107.
108.
The first synthesis of the bis(2-hydroxybenzoyl)dinaphthotetraaza[14]annulene ligand and its O,O-bis-alkylated derivatives containing a decanedioxy bridging moiety, pendant bis-alkoxy groups as well as dicationic butoxypyridinium substituents is reported. The synthetic procedures, full analytical and spectroscopic characterisation (NMR, MS and IR) and crystal structures of the new products are described. The crystal structures show that naphthylene moieties incorporated into the investigated derivatives provide additional opportunities for non-covalent interactions between the molecules. 相似文献
109.
Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II,Their Reactivity toward Organic Substrates,and the Influence of N‐Methylimidazole Axial Ligation 下载免费PDF全文
Maria Oszajca Agnieszka Drzewiecka‐Matuszek Dr. Alicja Franke Dr. Dorota Rutkowska‐Zbik Dr. Małgorzata Brindell Prof. Małgorzata Witko Prof. Grażyna Stochel Prof. Rudi van Eldik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2328-2343
High‐valent iron‐oxo species have been invoked as reactive intermediates in catalytic cycles of heme and nonheme enzymes. The studies presented herein are devoted to the formation of compound II model complexes, with the application of a water soluble (TMPS)FeIII(OH) porphyrin ([meso‐tetrakis(2,4,6‐trimethyl‐3‐sulfonatophenyl)porphinato]iron(III) hydroxide) and hydrogen peroxide as oxidant, and their reactivity toward selected organic substrates. The kinetics of the reaction of H2O2 with (TMPS)FeIII(OH) was studied as a function of temperature and pressure. The negative values of the activation entropy and activation volume for the formation of (TMPS)FeIV?O(OH) point to the overall associative nature of the process. A pH‐dependence study on the formation of (TMPS)FeIV?O(OH) revealed a very high reactivity of OOH? toward (TMPS)FeIII(OH) in comparison to H2O2. The influence of N‐methylimidazole (N‐MeIm) ligation on both the formation of iron(IV)‐oxo species and their oxidising properties in the reactions with 4‐methoxybenzyl alcohol or 4‐methoxybenzaldehyde, was investigated in detail. Combined experimental and theoretical studies revealed that among the studied complexes, (TMPS)FeIII(H2O)(N‐MeIm) is highly reactive toward H2O2 to form the iron(IV)‐oxo species, (TMPS)FeIV?O(N‐MeIm). The latter species can also be formed in the reaction of (TMPS)FeIII(N‐MeIm)2 with H2O2 or in the direct reaction of (TMPS)FeIV?O(OH) with N‐MeIm. Interestingly, the kinetic studies involving substrate oxidation by (TMPS)FeIV?O(OH) and (TMPS)FeIV?O(N‐MeIm) do not display a pronounced effect of the N‐MeIm axial ligand on the reactivity of the compound II mimic in comparison to the OH? substituted analogue. Similarly, DFT computations revealed that the presence of an axial ligand (OH? or N‐MeIm) in the trans position to the oxo group in the iron(IV)‐oxo species does not significantly affect the activation barriers calculated for C?H dehydrogenation of the selected organic substrates. 相似文献
110.
V2O3 room and low temperature structures have been refined using PXRD and Rietveld procedures. At 15 K, in addition to the umbrella like opening of V—O bonds associated to the typical large V—V distance through the face shared octahedra (V—Vfsh) we have observed three different V—V distances through the edge shared octahedra (V—Vedsh) : 2.985Å, 2.908Å, and 2.847Å. This splitting is a consequence of the rotation of V—V pairs in a plane itself rotated out of the ( ac ) one which appears to be the origin for the well‐known rhombohedral to monoclinic distortion. Ni for V substitutions drive to a V2—xNixO3 solid solution with a wide homogeneity range (0 < x < 0.75). Structure refinements on selected compositions show that at both room and 15 K temperatures the typical V2O3 corundum type is kept. At 300 K, the main Ni effect is a drastic decrease of the c parameter associated to a flattening of the octahedra but also to an increase of the M—Mfsh distance without rotation of the M—M pairs. This explains the absence of the monoclinic transition in the whole homogeneity and temperature ranges and shows clearly that a large M—Mfsh distance is not necessarily associated with the monoclinic form. Despite this large distance observed in the whole temperature range, the electric behavior exhibits a conductor to insulator transition. It is explained in terms of semi conduction via an electron hopping process between V3+ and V4+ cations which depends on Ni amounts. This last result implies also that a large M—Mfsh distance is not associated with an insulating behavior. 相似文献