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Farhad Ahmadi Maryam Rajabi Forozan Faizi Mehdi Rahimi-Nasrabadi Bozorgmehr Maddah 《International journal of environmental analytical chemistry》2013,93(11):1123-1138
Fe3O4-SiO2-C18 paramagnetic nanoparticles have been synthesised and used as magnetic solid-phase extraction (MSPE) sorbent for the extraction of Zineb from agricultural aqueous samples under ultrasonic condition and quantified through a first-derivative spectrophotometric method. The produced magnetic nanoparticles were characterised by using scanning electron microscopy, X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and zeta potential reader. The Fe3O4-SiO2-C18 paramagnetic nanoparticles had spherical structures with diameters in the range of 198–201 nm. Further, MSPE was performed by dispersion of Fe3O4-SiO2-C18 paramagnetic nanoparticles in a buffered aqueous solution accompanied by sonication. Next, the sorbents were accumulated by applying an external magnetic field and were washed with 4-(2-pyridylazo) resorcinol-dimethyl sulfoxide solution, for the purpose of desorbing the analyte. The extraction conditions (sample pH, washing and elution solutions, amount of sorbents, time of extraction, sample volume and effect of diverse ions), as well as Zineb-PAR first-order derivative spectra, were also evaluated. The calibration curve of the method was linear in the concentration range of 0.055–24.3 mg L?1 with a correlation coefficient of 0.991. The limit of detection and limit of quantification values were 0.022 and 0.055 mg L?1, respectively. The precision of the method for 0.27 mg L?1 solution of the analyte was found to be less than 3.2%. The recoveries of three different concentrations (0.27, 1.37 and 13.7 mg L?1) obtained 98.3%, 98.5% and 96.0%, respectively. The proposed Fe3O4-SiO2-C18 paramagnetic nanoparticles were found to have the capability of reusing for 7.0 times. 相似文献
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Shaheen Faizi Humaira Siddiqi Aneela Naz Samina Bano Lubna 《Helvetica chimica acta》2010,93(3):466-481
An H/D exchange process in patuletin ( 1 ) and its derivatives in D‐donor solvents (e.g., CF3COOD), which occurs regioselectively at C(8) was observed for the first time during NMR studies. The effect of substituents and temperature on the deuteration of various flavonoids (see Fig. 1) which include apigenin, chrysin, galangin, kaempferol, luteolin, morin, myricetin, patuletin, patulitrin, and quercetin, as well as derivatives of patuletin was examined extensively under NMR conditions. The rate constant of deuteration at C(8) of patuletin ( 1 ) and two flavones, luteolin ( 3 ) and apigenin ( 12 ), was also determined in CF3COOD. The D‐atom was introduced into the flavonoids via a keto–enol tautomerism (Scheme 1). During these studies, monodeuterated patuletin was also obtained as a new compound. The examined flavonoids have been reported to possess significant pharmacological activities, and their deuterated derivatives would be of importance for the identification and quantification of these compounds in biological matrices. 相似文献
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A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy 相似文献
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The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail. 相似文献
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By choosing a dynamical system with d different couplings, one can rearrange a system based on the graph with a given vertex dependent on the dynamical system
elements. The relation between the dynamical elements (coupling) is replaced by a relation between the vertexes. Based on
the E
0 transverse projection operator, we addressed synchronization problem of an array of the linearly coupled map lattices of
identical discrete time systems. The synchronization rate is determined by the second largest eigenvalue of the transition
probability matrix. Algebraic properties of the Bose-Mesner algebra with an associated scheme with definite spectrum has been
used in order to study the stability of the coupled map lattice. Associated schemes play a key role and may lead to analytical
methods in studying the stability of the dynamical systems. The relation between the coupling parameters and the chaotic region
is presented. It is shown that the feasible region is analytically determined by the number of couplings (i.e. by increasing
the number of coupled maps, the feasible region is restricted). It is very easy to apply our criteria to the system being
studied and they encompass a wide range of coupling schemes including most of the popularly used ones in the literature.
相似文献
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Catalyst‐Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes
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Darius J. Faizi Ashlee J. Davis Fiach B. Meany Prof. Dr. Suzanne A. Blum 《Angewandte Chemie (International ed. in English)》2016,55(46):14286-14290
The first ring‐forming thioboration reaction of C?C π bonds is reported. This catalyst‐free method proceeds in the presence of a commercially available external electrophilic boron source (B‐chlorocatecholborane) in good to high yields. The method is scalable and tolerates a variety of functional groups that are intolerant of other major borylation methods. The resulting borylated benzothiophenes participate in a variety of in situ derivatization reactions, showcasing that these borylated intermediates do not need to be isolated prior to downstream functionalization. This methodology has been extended to the synthesis of borylated dihydrothiophenes. Mechanistic experiments suggest that the operative mechanistic pathway is through boron‐induced activation of the alkyne followed by electrophilic cyclization, as opposed to S?B σ bond formation, providing a mechanistically distinct pathway to the thioboration of C?C π bonds. 相似文献