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541.
P. Perkowski M. Mrukiewicz M. Żurowska R. Dąbrowski L. Jaroszewicz 《Liquid crystals》2013,40(7):864-870
A broad temperature antiferroelectric binary mixture has been investigated by means of dielectric spectroscopy. The sample was cooled down to –70°C. It was found that the sample was still in antiferroelectric phase. This is the widest antiferroelectric mixture ever seen (~170°) in which three well-separated modes have been detected at room temperature. In addition, the bias field influence on existing modes has been observed. All modes change their strengths with bias field. Results show that the fastest mode, called X mode previously, gradually disappears around –30°C. When the temperature decreases below –40°C, one can indisputably observe additional mode, faster than X mode. This mode (named as Y mode) observed for extra low temperatures is bias independent. It can be the molecular mode, connected with rotation around long molecular axis. The rotation around short molecular axis seems to be blocked in antiferroelectric packing. To calculate parameters of observed modes, Cole–Cole model was used. The parameters of Y mode are discussed in this article. 相似文献
542.
P. Perkowski K. Ogrodnik W. Piecek M. Żurowska Z. Raszewski R. Dąbrowski 《Liquid crystals》2013,40(9):1159-1167
In a large class of smectic mixtures prepared at our University, the phase transition between chiral ferroelectric smectic C (SmC*) and chiral antiferroelectric smectic C (SmCA*) phases can be observed on cooling. Under bias field the temperature of the phase transition SmC*?SmCA* decreases (ca. 100°C in the investigated mixture). The transition is called: unwound SmC*?twisted SmCA* phase transition. The Goldstone mode in SmC* phase is reduced by a direct current field while two modes (PH and PL) in the SmCA* phase are amplified. The amplitude of the fast X mode observed in the SmCA* phase is reduced. The aim of this paper is to show how parameters of the modes in SmCA* phase (calculated from Cole–Cole model) change with bias voltage—when twisted structure in SmCA* phase is gradually unwound. The character of the modes observed in SmCA* is discussed. A new effect is shown: a high value of dielectric loss is detected in the unwound SmC* phase, which is very close to SmCA*. 相似文献
543.
Barbara Szpikowska-Sroka Lidia Żur Rozalia Czoik Tomasz Goryczka Andrzej S. Swinarew Maria Żądło Wojciech A. Pisarski 《Journal of Sol-Gel Science and Technology》2013,68(2):278-283
This paper reports an optical investigation of Eu3+:PbF2 nanocrystals distributed into silica glasses fabricated by sol–gel methods. The sample microstructure was investigated using scanning transmission electron microscopy. The β-cubic PbF2 crystalline phase was identified using X-ray diffraction analysis. The observed emission bands correspond to 5D0 → 7FJ (J = 0–4) transitions of Eu3+. The spectroscopic parameters for Eu3+ ions were determined based on excitation and emission measurements as well as luminescence decay analysis. Emission originating from 5D0 state of Eu3+ ions in sample containing PbF2 nanocrystals is long-lived in comparison to precursor sol–gel silica glasses. 相似文献
544.
Calcium zirconate powders doped with a small amount of CaO were synthesised using the Pechini method. X-ray analysis revealed that solid solution was formed in the concentration up to 51.5% mol CaO. For synthesis of stoichiometric CaZrO3, the highest temperature was required (1150°C), but introduction of excess CaO from 50.5 to 51.5% mol enabled us to lower the synthesis temperature to 800°C. The sintering behaviour of such samples under non-isothermal conditions was studied by dilatometric methods. Deviations were found in stoichiometry; by increasing the CaO concentration in CaZrO3 sinterability improved in comparison to CaZrO3 with stoichiometric composition. The presence of CaO as second phase caused deterioration of the sinterability of the CaZrO3-based samples. Pellets sintered at 1500°C for 2 h reached 96–98% of theoretical density. SEM and TEM observations were used to characterise the microstructure of the prepared samples. The electrical properties of CaZrO3-based samples were investigated by the AC-impedance spectroscopy method. It was found that introduction of excess CaO into the CaZrO3 structure caused an increase in ionic conductivity up to the solubility limit. The possibility of using CaZrO3-based samples for constructing prototype electrochemical oxygen probes to determine activity of oxygen dissolved in molten copper is also demonstrated. 相似文献
545.
Mariusz Żaba Piotr Garbaczewski Vladimir A. Stephanovich 《Central European Journal of Physics》2014,12(3):175-184
We discuss two independent methods of solution of a master equation whose biased jump transition rates account for long jumps of Lévy-stable type and admit a Boltzmannian (thermal) equilibrium to arise in the large time asymptotics of a probability density function ρ(x, t). Our main goal is to demonstrate a compatibility of a direct solution method (an explicit, albeit numerically assisted, integration of the master equation) with an indirect pathwise procedure, recently proposed in [Physica A 392, 3485, (2013)] as a valid tool for a dynamical analysis of non-Langevin jump-type processes. The path-wise method heavily relies on an accumulation of large sample path data, that are generated by means of a properly tailored Gillespie’s algorithm. Their statistical analysis in turn allows to infer the dynamics of ρ(x, t). However, no consistency check has been completed so far to demonstrate that both methods are fully compatible and indeed provide a solution of the same dynamical problem. Presently we remove this gap, with a focus on potential deficiencies (various cutoffs, including those upon the jump size) of approximations involved in simulation routines and solutions protocols. 相似文献
546.
A new ruthenium ion imprinted polymer was prepared from the Ru(III) 2-thiobarbituric acid complex (the template), methacrylic acid or acrylamide (the functional monomers), and ethylene glycol dimethacrylate (the cross-linking agent) using 2,2′-azobisisobutyronitrile as the radical initiator. The ion imprinted polymer was characterized and used as a selective sorbent for the solid phase extraction of Ru(III) ions. The effects of type of functional monomer, sample volume, solution pH and flow rate on the extraction efficiency were studied in the dynamic mode. Ru(III) ion was quantitatively retained on the sorbents in the pH range from 3.5 to 10, and can be eluted with 4 mol L?1 aqueous ammonia. The affinity of Ru(III) for the ion imprinted polymer based on the acrylamide monomer is weaker than that for the polymer based on the methacrylic acid monomer, which therefore was used in interference studies and in analytical applications. Following extraction of Ru(III) ions with the imprint and their subsequent elution from the polymer with aqueous ammonia, Ru(III) was detected by electrothermal atomic absorption spectrometry with a detection limit of 0.21 ng mL?1. The method was successfully applied to the determination of trace amounts of Ru(III) in water, waste, road dust and platinum ore (CRM SARM 76) with a reproducibility (expressed as RSD) below 6.4 %. Figure
The new ion imprinted polymer was prepared and used for the separation of ruthenium from water and most complex environmental samples, such as road dust and platinum ore (CRM SARM 76) prior ETAAS determination. 相似文献
547.
Mariola Kozłowska Anna Żbikowska Eliza Gruczyńska Katarzyna Żontała Andrzej Półtorak 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1697-1705
The addition of natural antioxidants to the bakery products containing fats can extend their shelf life, and it may be more attractive to consumers. In this research, the antioxidant effect of spice extracts and synthetic antioxidant on oxidative stability of fat extracted from cookies was evaluated by differential scanning calorimetry (DSC). The results revealed that addition of spice extracts to the cookies in comparison to cookies without additives reduced the oxidation as evidenced by higher the onset oxidation temperature (t ON) of antioxidant-treated samples. Using the Ozawa–Flynn–Wall method, the activation energies (E a/kJ mol?1) and pre-exponential factors (Z/min?1) and then induction times (τ/min) were calculated and also used for evaluation of antioxidants efficiency. After baking, cookies were also subjected to sensory studies and to instrumental measurements of colour changes. Among the samples studied, cookies with 0.02 % of rosemary or 0.2 % thyme extracts showed good sensorial acceptability. Cookies fortified with spice extracts also characterised greater lightness compared to the control sample. 相似文献
548.
The interaction of the diethyl(quinolin-2-ylmethyl)phosphonate (2-qmpe) ligand with CoCl2 · 2H2O unexpectedly leads to the formation of a compound with the formula [Co(2-qca)2(EtOH)2] (2-qca = quinoline-2-carboxylate). This compound is a product of the oxidative cleavage of the C–P bond in 2-qmpe and the formation of the 2-qca ligand. The title compound was characterized by infrared, ligand field, EPR spectroscopy and low temperature magnetic (1.8–300 K) studies. Particularly, the crystal and molecular structures were determined by the X-ray diffraction. The CoN2O4 chromophore shows an elongated octahedron geometry, resulting from the two didentate N,O-bonded chelate ligands and two ethanol molecules – quinolil nitrogen atoms are located in axial positions and oxygen atoms are positioned in the basal plane. The crystal packing is due to hydrogen bonds and π–π stacking interactions, which give rise to a three-dimensional (3D) polymeric network. The magnetic properties reflect the molecular character of the compound, with a very weak magnetic exchange interaction. The moments are enhanced due to an important orbital contribution via spin–orbit coupling. 相似文献
549.
Emilia Grodzka Joanna Grabowska Monika Wysocka-Żołopa Krzysztof Winkler 《Journal of Solid State Electrochemistry》2008,12(10):1267-1278
The electrochemically active polymers have been formed during electro-reduction carried out in solution containing fullerenes,
C60 or C70, and transition metal complexes of Pd(II), Pt(II), Rh(III), and Ir(I). In these films, fullerene moieties are covalently
bounded to transition metal atoms (Pd and Pt) or their complexes (Rh and Ir) to form a polymeric network. All films exhibit
electrochemical activity at negative potentials due to the fullerene cages reduction process. For all studied metal complexes,
yields of formation of films containing C70 are higher than yields of electrodeposition of their C60 analogs. C70
/M films also exhibit higher porosity in comparison to C60/M layers. The differences in film morphology and efficiency of polymer formation are responsible for differences in electrochemical
responses of these films in acetonitrile containing supporting electrolyte only. C70/M films shows more reversible voltammeric behavior in negative potential range. They also show higher potential range of electrochemical
stability. Processes of film formation and electrochemical properties of polymers depend on the transition metal ions or atoms
bonding fullerene cages into polymeric network. The highest efficiency of polymerization was observed for fullerene/Pd and
fullerene/Rh films. In the case of fullerene/Pd films, the charge transfer processes related to the fullerene moieties reduction
in negative potential range exhibit the best reversibility among all of the studied systems. Capacitance performances of C60/Pd and C70/Pd films deposited on the porous Au/quartz electrode were also compared. Capacitance properties of both films are significantly
affected by the conditions of electropolymerization. Only a fraction of the film having a direct contact with solution contributes
to pseudocapacitance. Capacitance properties of these films also depend on the size of cations of supporting electrolyte.
The C70/Pd film exhibits much better capacitance performance comparison to C60/Pd polymer. 相似文献
550.
Rudowska M Wojewska D Kluczyk A Bąchor R Stefanowicz P Szewczuk Z 《Journal of the American Society for Mass Spectrometry》2012,23(6):1024-1028
Derivatization of peptides as quaternary ammonium salts (QAS) is a known method for sensitive detection by electrospray ionization
tandem mass spectrometry. Hydrogens at α-carbon atom in N,N,N-trialkylglycine residue can be easily exchanged by deuterons. The exchange reaction is base-catalyzed and is dramatically
slow at lower pH. Introduced deuterons are stable in acidic aqueous solution and are not back-exchanged during LC-MS analysis.
Increased ionization efficiency, provided by the fixed positive charge on QAS group, as well as the deuterium labeling, enables
the analysis of trace amounts of peptides. 相似文献