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111.
Viviana Heguaburu Hugo do Carmo Florencia Parpal María Eugenia Amorós Andrés González 《Tetrahedron letters》2017,58(18):1738-1741
The synthesis of 3-hydroxy-2-hexanone and 2,3-hexanediol, two components of the aggregation pheromone of several cerambycid species, is disclosed in here. Starting from 2-hexanone, through an α-hydroxylation using (diacetoxyiodo)benzene, 3-hydroxy-2-hexanone is obtained in good yield. Further reduction of this compound, gives 2,3-hexanediol in excellent yield. A study of the α-hydroxylation reaction of several alkylketones using an hypervalent iodine reagent is also disclosed in here. The synthesis of optically active compounds (R)- and (S)-3-hydroxy-2-hexanone was achieved starting from 2-hexanone with nitrosobenzene and l- and d-proline respectively, in several reaction media. 相似文献
112.
113.
David Alonso-Gutiérrez Bernardo González Merino C. Hugo Jiménez Rafael Villa 《Journal of Geometric Analysis》2018,28(2):1182-1201
We extend the notion of John’s ellipsoid to the setting of integrable log-concave functions. This will allow us to define the integral ratio of a log-concave function, which will extend the notion of volume ratio, and we will find the log-concave function maximizing the integral ratio. A reverse functional affine isoperimetric inequality will be given, written in terms of this integral ratio. This can be viewed as a stability version of the functional affine isoperimetric inequality. 相似文献
114.
115.
Florent Balacheff Hugo Parlier Stéphane Sabourau 《Geometric And Functional Analysis》2012,22(1):37-73
Given a Riemannian surface, we consider a naturally embedded graph which captures part of the topology and geometry of the
surface. By studying this graph, we obtain results in three different directions. 相似文献
116.
Anaí Duarte Wilson Cunico Claudio M.P. Pereira Alex F.C. Flores Rogério A. Freitag Geonir M. Siqueira 《Ultrasonics sonochemistry》2010,17(2):281-283
An ultrasound-enhanced method has been developed for the synthesis of a variety of thioesters from benzoyl chlorides and 2-mercaptobenzoxa(thia)zoles. Applying this methodology, 14 compounds were synthesized in excellent yields. 相似文献
117.
Hugo R. Fernandes Dilshat U. Tulyaganov José M. F. Ferreira 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1359-1368
The crystallisation kinetics of experimental glasses in 3 different systems: (A) Li2O–SiO2, (B) Li2O–Al2O3–SiO2 and (C) Li2O–K2O–Al2O3–SiO2 were studied under non-isothermal conditions. The DTA results revealed a stronger tendency to crystallisation of binary compositions in comparison to the ternary and quaternary compositions comprising Al2O3 and K2O which present the lower crystallisation, i.e. the crystallisation propensity follows the trend A > B > C. The devitrification process in the Li2O–SiO2 and Li2O–Al2O3–SiO2 systems began earlier and the rate was higher in comparison to that of glasses in the quaternary Li2O–K2O–Al2O3–SiO2 system. Thus, addition of Al2O3 and K2O to glasses of Li2O–SiO2 system was demonstrated to promote glass stability against crystallisation. However, the activation energy for crystallisation was shown to depend also on the SiO2/Li2O ratio with the binary system showing a decreasing trend with increasing SiO2/Li2O ratio, while the opposite tendency was being observed for compositions with added Al2O3 and K2O. 相似文献
118.
Estela de Pieri Troiani Edenir Rodrigues Pereira‐Filho Ronaldo Censi Faria 《Electroanalysis》2013,25(8):1988-1994
A simple and sensitive method for simultaneously measuring dopamine (DA), ascorbic acid (AA), and uric acid (UA) using a poly(1‐aminoanthracene) and carbon nanotubes nanocomposite electrode is presented. The experimental parameters for composite film synthesis as well as the variables related to simultaneous determination of DA, AA, and UA were optimized at the same time using fractional factorial and Doehlert designs. The use of carbon nanotubes and poly(1‐aminoanthracene) in association with a cathodic pretreatment led to three well‐defined oxidation peaks at potentials around ?0.039, 0.180 and 0.351 V (vs. Ag/AgCl) for AA, DA, and UA, respectively. Using differential pulse voltammetry, calibration curves for AA, DA, and UA were obtained over the range of 0.16–3.12×10?3 mol L?1, 3.54–136×10?6 mol L?1, and 0.76–2.92×10?3 mol L?1, with detection limits of 3.95×10?5 mol L?1, 2.90×10?7 mol L?1, and 4.22×10?5 mol L?1, respectively. The proposed method was successfully applied to determine DA, AA, and UA in biological samples with good results. 相似文献
119.
Bruno M. Soares Ederson R. Pereira Juliana V. Maciel Augusto A. Vieira Fabio A. Duarte 《Journal of separation science》2013,36(20):3411-3418
This work reports the development of a dispersive liquid – liquid microextraction method for the simultaneous extraction, preconcentration, and derivatization of Hg2+ and CH3Hg+ species from water samples for further determination by GC – MS. Some parameters of the proposed method, such as volume and type of disperser and extraction solvent, and Na[B(C6H5)4] concentration were investigated using response surface methodology. Suitable recoveries were obtained using 80 μL C2Cl4 (as extraction solvent), 1000 μL ethanol (as disperser solvent), and 300 μL 2.1 mmol/L Na[B(C6H5)4] (as derivatizing agent). Accuracy was evaluated in terms of recovery and ranged from 87 to 99% with RSD values <7%. In addition, a certified reference material of water (NIST 1641d) was analyzed and agreed with the certified value about 107% (for Hg2+), with RSD values <8.5%. LODs were 0.3 and 0.2 μg/L, with enrichment factors of 112 and 115 for Hg2+ and CH3Hg+, respectively. The optimized method was applied for the determination of Hg2+ and CH3Hg+ in tap, well, and lake water samples. 相似文献
120.
A methodology for kinetic modeling of conversion processes is presented.The proposed approach allows to overcome the lack of molecular detail of the petroleum fractions and to simulate the reactions of the process by means of a two-step procedure.In the first step,a synthetic mixture of molecules representing the feedstock is generated via a molecular reconstruction method,termed SR-REM molecular reconstruction.In the second step,a kinetic Monte Carlo method,termed stochastic simulation algorithm(SSA),is used to simulate the effect of the conversion reactions on the mixture of molecules.The resulting methodology is applied to the Athabasca vacuum residue hydrocracking.An adequate molecular representation of the vacuum residue is obtained using the SR-REM algorithm.The reaction simulations present a good agreement with the laboratory data for Athabasca vacuum residue conversion.In addition,the proposed methodology provides the molecular detail of the vacuum residue conversion throughout the reactions simulations. 相似文献