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131.
Simona Rada Maria Bosca Eugen Culea Marius Rada Viorel Dan Vistrian Maties 《Structural chemistry》2009,20(5):801-805
Glasses in the system xGd2O3 · (100 − x)[0.7TeO2 · 0.3V2O5] with 0 ≤ x ≤20 mol% have been prepared from melt quenching method. Influence of gadolinium ions on structural behavior in vanadate–tellurate
glasses has been investigated using FTIR spectroscopy, X-ray diffraction (XRD), and magnetic susceptibility measurements.
The structural changes have been analyzed with increasing rare earth concentration. The structural changes, as recognized
by analyzing band shapes of XRD and FTIR spectra, revealed that Gd2O3 causes a higher extent of network polymerization as far as 20 mol%. The structure of the heat-treated glasses was found to
consist mainly of the Te2V2O9 crystalline phase. These vitreous systems were investigated by magnetic susceptibility measurements. From the paramagnetic
susceptibility χ was calculated at different temperature and from the 1/χ(T) graph, the Curie temperature of the glass has been evaluated. Magnetic susceptibility data show the presence of small antiferromagnetic
interactions between the Gd+3 ions. 相似文献
132.
133.
134.
B Kükrer IM Barbu J Copps P Hogan SS Taylor E van Duijn AJ Heck 《Journal of the American Society for Mass Spectrometry》2012,23(9):1534-1543
In the gas-phase, ions of protein complexes typically follow an asymmetric dissociation pathway upon collisional activation, whereby an expelled small monomer takes a disproportionately large amount of the charges from the precursor ion. This phenomenon has been rationalized by assuming that upon activation, a single monomer becomes unfolded, thereby attracting charges to its newly exposed basic residues. Here, we report on the atypical gas-phase dissociation of the therapeutically important, heterodimeric calcium/calmodulin-dependent serine/threonine phosphatase calcineurin, using a combination of tandem mass spectrometry, ion mobility mass spectrometry, and computational modeling. Therefore, a hetero-dimeric calcineurin construct (62?kDa), composed of CNa (44?kDa, a truncation mutant missing the calmodulin binding and auto-inhibitory domains), and CNb (18?kDa), was used. Upon collisional activation, this hetero-dimer follows the commonly observed dissociation behavior, whereby the smaller CNb becomes highly charged and is expelled. Surprisingly, in addition, a second atypical dissociation pathway, whereby the charge partitioning over the two entities is more symmetric is observed. The presence of two gas-phase conformational isomers of calcineurin as revealed by ion mobility mass spectrometry (IM-MS) may explain the co-occurrence of these two dissociation pathways. We reveal the direct relationship between the conformation of the calcineurin precursor ion and its concomitant dissociation pathway and provide insights into the mechanisms underlying this co-occurrence of the typical and atypical fragmentation mechanisms. 相似文献
135.
Two-dimensional and one-dimensional models are used to evaluate the seashore effects of the tsunami generated by an asteroid hitting the deep water in the Eastern region of the Black Sea. The shallow water theory has been used to describe tsunami propagation. The distance between the impact point and the nearest coast is about 150 km. The effects on the coastal regions depend on many factors among which the most important is asteroid size. The tsunami generated by a 250 m asteroid reaches the nearest dry land location in 20 minutes and needs about two hours to hit all over the Black Sea coast. The horizontal inundation length is also known as run-in or run-off distance, according to the direction of water movement. The run-up values may be up to 39 m in the Eastern basin and a more than ten times smaller in theWestern region. The Northern part of the Black Sea coast is not affected by the tsunami. The run-in values of a tsunami generated by a 1000 m diameter asteroid are sensibly larger than the similar values associated to a 250 m diameter asteroid. The run-in strongly depends on the distance from the impact position to the shore and on coastal topographical profile. For instance, the run-in distance in case of a tsunami generated by a 250 m size asteroid is 0.1 km (at Varna), 0.5 km (Ordu), 0.7 km (Yalta) and 1.4 km (Sochi). In case of the 1000 m diameter asteroid the run-in distance is 0.7 km (at Varna) and 2.9 km (Yalta). The results accuracy is also discussed. 相似文献
136.
Mirela Barbu Mircea Stefanescu Marcela Stoia Gabriela Vlase Paul Barvinschi 《Journal of Thermal Analysis and Calorimetry》2012,108(3):1059-1066
In this article, we present a new method for the obtaining of ZnCr2O4 and MgCr2O4 embedded in silica matrix. This method consists in the formation of Cr(III), Zn(II) and Cr(III), Mg(II) hydroxycarboxylate/carboxylate compounds, during the redox reaction between the nitrate ion and diol (1,3-propanediol), uniformly dispersed in the pores of hybrid gels. The thermal decomposition of these precursors leads to a mixture of corresponding metal oxides. The gels were synthesized starting from mixtures of Cr(NO3)3·9H2O, Zn(NO3)2·6H2O and Cr(NO3)3·9H2O, Mg(NO3)2·6H2O with tetraethyl orthosilicate and 1,3-propanediol for final compositions 50% ZnCr2O4/50% SiO2 and 50% MgCr2O4/50% SiO2. The obtained gels have been thermally treated at 140?°C, when the redox reaction nitrates-diol took place with formation of the precursors within the xerogels pores. The thermal decomposition of all precursors took place up to 300?°C, with formation of oxides mixtures (Cr2O3?+?x and ZnO) and (Cr2O3?+?x and MgO), respectively. At 400?°C, Cr2O3?+?x turn to Cr2O3 which reacts with ZnO forming ZnCr2O4/SiO2. Starting with 400?°C, Cr2O3 reacts with MgO to an intermediary phase MgCrO4, which decomposes with the formation of MgCr2O4/SiO2. The formation of the precursors inside the silica matrix and the evolution of the crystalline phases were studied by thermal analysis, FT-IR spectrometry, XRD, and TEM. 相似文献
137.
Viorel Cîrcu Ana S. Mocanu Constantin Roşu Doina Manaila-Maximean Florea Dumitraşcu 《Journal of Thermal Analysis and Calorimetry》2012,107(3):877-886
A series of ortho-metallated palladium(II) complexes with two dimeric liquid crystals Schiff base (methoxy and decyloxy as terminal groups)
as cyclometallated ligands and N-aryl-N′-benzoyl thiourea derivatives as co-ligands were prepared and investigated for their liquid crystalline properties. Their
structures were assigned based on elemental analysis, FT-IR and 1H NMR spectroscopy while the thermal behaviour was investigated by differential scanning calorimetry and polarising optical
microscopy. The complexes with Schiff base ligand bearing methoxy group as terminal group show extensive decomposition during
melting while the complexes with Schiff base having decyloxy group as terminal group show monotropic nematic phases, with
the mesophase stability strongly related to the type of N-aryl-N′-benzoyl thiourea derivative used. Their liquid crystalline properties are compared with their analogues having N,N-dialkyl-N′-benzoyl thiourea as co-ligands which were reported previously. One of the latter complexes was also investigated by thermally
stimulated depolarisation currents method while the optical transmission was recorded simultaneously. The thermally stimulated
depolarisation currents and optical transmission spectra confirmed the previous observation regarding the phase transition
temperatures. The current intensity–applied voltage dependencies of this complex were investigated by specific electrical
measurements. 相似文献
138.
Soto Tellini VH Jover A Galantini L Pavel NV Meijide F Vázquez Tato J 《The journal of physical chemistry. B》2006,110(28):13679-13681
The self-aggregation of the sodium salt of a new adamantyl amide of the 3beta-amino derivative of cholic acid (Na-AdC) in aqueous solution has been investigated by surface tension, dynamic light scattering, fluorescence, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) measurements. These last two techniques suggest that a lamellar phase, consisting of charged bilayers of Na-AdC separated by solvent and periodically stacked, is formed in aqueous solution. The structure of the bilayer is inferred from the resolution of the crystal of the compound in its acid form. The adamantyl moieties, which are mutually interlocked, reside in the central region of the bilayer, and the carboxylic groups are directed toward the hydrophilic region. The structure is open enough to allow water molecules to interact with a fluorescence probe located at the central hydrophobic region. 相似文献
139.
Viorel Barbu Irena Lasiecka Roberto Triggiani 《Nonlinear Analysis: Theory, Methods & Applications》2006
The present paper seeks to continue the analysis in Barbu et al. [Tangential boundary stabilization of Navier–Stokes equations, Memoir AMS, to appear] on tangential boundary stabilization of Navier–Stokes equations, d=2,3, as deduced from well-posedness and stability properties of the corresponding linearized equations. It intends to complement [V. Barbu, I. Lasiecka, R. Triggiani, Tangential boundary stabilization of Navier–Stokes equations, Memoir AMS, to appear] on two levels: (i) by casting the Riccati-based results of Barbu et al. [Tangential boundary stabilization of Navier–Stokes equations, Memoir AMS, to appear] for d=2,3 in an abstract setting, thus extracting the key relevant features, so that the resulting framework may be applicable also to other stabilizing boundary feedback operators, as well as to other parabolic-like equations of fluid dynamics; (ii) by including, in the case d=2 this time, also the low-level gain counterpart of the results in Barbu et al. [Tangential boundary stabilization of Navier–Stokes equations, Memoir AMS, to appear] with both Riccati-based and spectral-based (tangential) feedback controllers. This way, new local boundary stabilization results of Navier–Stokes equations are obtained over [V. Barbu, I. Lasiecka, R. Triggiani, Tangential boundary stabilization of Navier–Stokes equations, Memoir AMS, to appear]. 相似文献
140.