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101.
A simple and efficient synthetic method for highly ordered nanoporous carbons with high mechanical and thermal stability has been performed through a direct template carbonization using as-synthesized MCM-48 hosts. 相似文献
102.
The lifetime of a large repairable system can be decomposed into two parts. The first one is the cumulative time spent in
the perfect state (all components are operating), and the second one is the restoration time when some components have failed.
For highly reliable systems, the first time is close to the system lifetime, and it turns out that this approximation is accurate
in many practical cases. Nevertheless, it is important to evaluate the error of such an approximation. Some bounds exist if
each component has a constant failure rate. In this paper, using estimates of geometric sums, we get bounds for the general
case.
Proceedings of the Seminar on Stability Problems for Stochastic Models, Hajdúszoboszló, Hungary, 1997, Part III. 相似文献
103.
Van Bon Nguyen Quang Vinh Nguyen Anh Dzung Nguyen San-Lang Wang 《Research on Chemical Intermediates》2017,43(6):3599-3612
α-Glucosidase inhibitors have received much attention due to their important use in treating diabetes mellitus. Although some synthetic α-glucosidase inhibitors have been available for a long time, they often cause various unexpected side effects. Thus, the present study was aimed at finding a safe, natural source of α-glucosidase inhibitors. Twenty-six samples of 22 medicinal plants were collected in the Dak Lak province of Vietnam and evaluated for α-glucosidase inhibitory activity. Trunk bark extract from Euonymus laxiflorus Champ (ELC extract) was selected as the best α-glucosidase inhibitor with the smallest IC50 = 0.36 mg/mL against rat-derived α-glucosidase. This extract had a stronger inhibitory activity against α-glucosidase from Saccharomyces cerevisiae (IC50 = 1.32 µg/mL) and Bacillus stearothermophilus (IC50 = 5.15 µg/mL). The potential inhibition against some other enzymes were tested, and the results showed that the ELC extract did not inhibit fungal cellulase but strongly inhibited porcine α-amylase (IC50 = 6.7 µg/mL). The ELC extract also inhibited the proteases papain and bromelain, with IC50 = 339 µg/mL and IC50 = 226 µg/mL, respectively. The thermal and pH stabilities of the ELC extract were also investigated. 相似文献
104.
Vladimir V. Bon Svetlana I. Orysyk Vasilii I. Pekhnyo Viktor V. Orysyk Sergei V. Volkov 《Polyhedron》2007
The present paper describes the synthesis and spectral properties of Rh(III) and Pd(II) coordination compounds with N-(pyridine-2-yl)morpholine-4-carbothioamide (PMCTA). The compounds have the general composition [RhL2Cl2]Cl · C2H5OH (1), [PdL2]Cl2 (2), [PdL2](ClO4)2 · 2C3H6O (2a), [PdLCl2] · 2H2O (3). All complexes were characterized by elemental analysis, IR, 1H NMR, 13C NMR, XPS and UV–Vis spectra. It has been shown that PMCTA behaves as a bidentate (N,S)-ligand, forming six membered metallocycles and coordinating to the metal ion through the carbothioamide sulfur atom and the pyridine nitrogen atom. The UV–Vis spectra suggest that the Pd(II) complexes are square planar, while the Rh(III) complex has an octahedral geometry. The molecular structure of the Pd(II) complex with PMCTA (M:L = 1:2) was determined by single-crystal X-ray diffraction. 相似文献
105.
Solid-stabilized, or Pickering, miniemulsion polymerizations using Laponite clay discs as stabilizer are investigated. Free radical polymerizations are carried out using a variety of hydrophobic monomers (i.e., styrene, lauryl (meth)acrylate, butyl (meth)acrylate, octyl acrylate, and 2-ethyl hexyl acrylate). Armored latexes, of which the surfaces of the particles are covered with clay discs, are obtained, as confirmed by scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Overall polymerization kinetics of the Pickering miniemulsion polymerizations of styrene were investigated via gravimetry. Comparison with the bulk polymerization analogue clearly shows compartmentalization. Moreover, retardation effects up to intermediate monomer conversions are observed; they are more prominent for the smaller particles and are ascribed to the Laponite clay. A model is presented that allows for the prediction of the average particle size of the latexes produced as a function of the amounts of monomer and Pickering stabilizers used. It shows that under specific generic conditions the number of clay discs used correlates in a linear fashion with the total surface area of the latex particles. This is a direct result of the reversibility of the Laponite clay disc adhesion process under the emulsification conditions (i.e., sonication) used. 相似文献
106.
Dr. Kornel Roztocki Dr. Volodymyr Bon Dr. Irena Senkovska Prof. Dariusz Matoga Prof. Stefan Kaskel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202255
We present an autonomous, chemical logic gate based on a switchable metal–organic framework (MOF) composite, containing carbon nanoparticles and a Pt catalyst. The switchable MOF composite performs as AND logic gate. Hydrogen and oxygen gas streams serve as binary inputs. Catalytically formed water induces a structural transition (crystal volume expansion) of the MOF, and as a consequence, a detectable drop in conductance of the composite as a ‘true’ output only if both gases come in contact with the composite. 相似文献
107.
108.
109.
Lukšič M Bončina M Vlachy V Druchok M 《Physical chemistry chemical physics : PCCP》2012,14(6):2024-2031
Aliphatic x,y-ionenes are polyelectrolytes in which x and y denote the numbers of methylene groups separating quaternary ammonium ions. They represent useful model substances for studying hydrophobic and charge effects in aqueous solutions. We used isothermal titration calorimetry to measure the enthalpies of mixing, ΔH(mix), of 3,3- and 6,6-ionene fluorides and bromides with low molecular weight salts (NaF, NaCl, NaBr, and NaI) at 298 K in water. The signs and magnitudes of the measured enthalpies depend on the hydrophobicity of the ionene and on the nature of the added salt. For example, addition of sodium fluoride to solutions of 3,3- and 6,6-ionene fluorides produced endothermic effects, while addition of sodium bromide to 3,3-ionene bromide resulted in a strong exothermic effect. Interestingly, mixing of 6,6-ionene bromide and NaBr solutions in water gave a small exothermic heat effect. Polyelectrolyte theories, based on continuum-solvent models, predict enthalpies of mixing to be positive (endothermic) for all the solutions examined in this work. The ion-specific effect is more strongly expressed in ionene solutions with higher charge density (3,3-ionene). The most important result of this work is the finding that the enthalpy of mixing of 3,3- (and of 6,6-ionene) fluorides with sodium halides can be expressed as a linear function of the enthalpy of hydration of the halide counterions. The experimental results were complemented with an explicit water molecular dynamics simulation of solutions of oligoions modelling 3,3- and 6,6-ionenes. The computer simulation results for various nitrogen-counterion pair distribution functions were in most cases consistent with the enthalpy measurements. 相似文献
110.
V Bon V Senkovskyy I Senkovska S Kaskel 《Chemical communications (Cambridge, England)》2012,48(67):8407-8409
Zr and Hf based MOFs with enhanced pore accessibility for large molecules and good hydrothermal stability were obtained using a bent dithienothiophene dicarboxylate and Zr(4+) or Hf(4+) source. A modulator (benzoic acid) facilitates formation of an eight-connecting cluster leading to a new framework which adopts reo topology. 相似文献