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101.
102.
Zaira Domínguez Javier Hernández Lorena Silva-Gutiérrez Magali Salas-Reyes Mario Sánchez Gabriel Merino 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):772-784
The effect of electron-withdrawing (EW) and electron-releasing (ER) substituents on the 31P NMR chemical shifts and the structural parameters of a series of tris-(p-X-aryl)selenophosphates is reported in this article. Similarly to O-aryl phosphates and O-aryl thiophosphates, EW groups attached to aromatic rings induce a shielding effect on the 31P NMR signal. After a detailed experimental and theoretical analysis, we confirmed that the selenium atom is the main part responsible for the charge density transfer toward phosphorus through a back-bonding effect. The obtained 1JP-Se values for the complete series agree with this observation. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
103.
Self‐assembled monolayers of cucurbit[6]uril (CB[6]) on a gold electrode have been used for 4,4′‐oxydialine (ODA) analysis. The formation of the supramolecular complex between ODA and CB[6] was used for the molecular selection and the electroanalytical determination of this analyte. In addition to this, all the parameters affecting the modification of the gold electrode and the determination of 4,4′‐oxydianiline were optimized by square wave voltammetry. Upon the electrode modification, pentanethiol was employed to fill up the exposed surface between CB[6] molecules. The calculated detection and determination limits were 0.06 µg mL?1 and 0.19 µg mL?1, respectively, with good accuracy and precision as shown by the calculated values for the relative error and relative standard deviation (Er=0.1 % and RDS=2.9 %; n=10 ). Moreover, the developed methodology was successfully applied to the 4,4′‐oxydialine determination in real wastewaters and shoe‐dyeing samples. 相似文献
104.
Photoactive materials based on dye molecules incorporated into thin films or bulk solids are useful for applications as photosensitization, photocatalysis, solar cell sensitization and fluorescent labeling, among others. In most cases, high concentrations of dyes are desirable to maximize light absorption. Under these circumstances, the proximity of dye molecules leads to the formation of aggregates and statistical traps, which dissipate the excitation energy and lower the population of excited states. The search for enhancement of light collection, avoiding energy wasting requires accounting the photophysical parameters quantitatively, including the determination of quantum yields, complicated by the presence of light scattering when particulate materials are considered. In this work we summarize recent advances on the photophysics of dyes in light‐scattering materials, with particular focus on the effect of dye concentration. We show how experimental reflectance, fluorescence and laser‐induced optoacoustic spectroscopy data can be used together with theoretical models for the quantitative evaluation of inner filter effects, fluorescence and triplet formation quantum yields and energy transfer efficiencies. 相似文献
105.
106.
C. Hernández-Jaimes B. Fouconnier C. Pérez-Alonso J. L. Munguía-Guillén 《Journal of Dispersion Science and Technology》2013,34(1):64-71
Equisetum arvense supercritical CO2 extracts (EAE) contained an initial antioxidant activity of 10.3 mM TEAC that suffered a sharp first order kinetics decay characterized by half-life time (t1/2) of 1.05 ± 0.03 and 0.86 ± 0.03 weeks at 25 and 4°C, respectively. The aim of the present work was to develop a nanoemulsion formulation for providing EAE protection against deleterious environmental factors and extending its shelf-life functionality. The nanoemulsion area was identified by constructing pseudoternary phase diagrams and response surface methodology was used to optimize the preparation conditions. The best formulation achieved an EAE encapsulation efficiency of 97.5 ± 0.5% and antioxidant activity half-life time (t1/2) was extended to 12.32 ± 0.40 and 14.56 ± 0.60 weeks at 25 and 4°C, respectively. 相似文献
107.
Crispín Cristóbal Dr. Yohar A. Hernández Dr. Joaquín López‐Serrano Prof. Dr. Margarita Paneque Dr. Ana Petronilho Prof. Dr. Manuel L. Poveda Dr. Verónica Salazar Florencia Vattier Dr. Eleuterio Álvarez Dr. Celia Maya Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):4003-4020
The reactivity of a series of iridium? pyridylidene complexes with the formula [TpMe2Ir(C6H5)2(C(CH)3C(R)N H] ( 1 a – 1 c ) towards a variety of substrates, from small molecules, such as H2, O2, carbon oxides, and formaldehyde, to alkenes and alkynes, is described. Most of the observed reactivity is best explained by invoking 16 e? unsaturated [TpMe2Ir(phenyl)(pyridyl)] intermediates, which behave as internal frustrated Lewis pairs (FLPs). H2 is heterolytically split to give hydride? pyridylidene complexes, whilst CO, CO2, and H2C?O provide carbonyl, carbonate, and alkoxide species, respectively. Ethylene and propene form five‐membered metallacycles with an IrCH2CH(R)N (R=H, Me) motif, whereas, in contrast, acetylene affords four‐membered iridacycles with the IrC(?CH2)N moiety. C6H5(C?O)H and C6H5C?CH react with formation of Ir? C6H5 and Ir? C?CPh bonds and the concomitant elimination of a molecule of pyridine and benzene, respectively. Finally the reactivity of compounds 1 a – 1 c against O2 is described. Density functional theory calculations that provide theoretical support for these experimental observations are also reported. 相似文献
108.
Daniel Tordera Andreas M. Bünzli Antonio Pertegás Dr. José M. Junquera‐Hernández Prof. Edwin C. Constable Dr. Jennifer A. Zampese Prof. Catherine E. Housecroft Prof. Enrique Ortí Dr. Henk J. Bolink 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8597-8609
A new approach to obtain green‐emitting iridium(III) complexes is described. The synthetic approach consists of introducing a methylsulfone electron‐withdrawing substituent into a 4‐phenylpyrazole cyclometalating ligand in order to stabilize the highest‐occupied molecular orbital (HOMO). Six new complexes have been synthesized incorporating the conjugate base of 1‐(4‐(methylsulfonyl)phenyl)‐1 H‐pyrazole as the cyclometalating ligand. The complexes show green emission and very high photoluminescence quantum yields in both diluted and concentrated films. When used as the main active component in light‐emitting electrochemical cells (LECs), green electroluminance is observed. High efficiencies and luminances are obtained at low driving voltages. This approach for green emitters is an alternative to the widely used fluorine‐based substituents in the cyclometalating ligands and opens new design possibilities for the synthesis of green emitters for LECs. 相似文献
109.
Iván Escalona Edgar Del Carpio Lino Hernández Vito Lubes 《Journal of solution chemistry》2014,43(6):1001-1010
In this work, the ternary complex formation among copper(II), 6-methylpicolinic acid (H6Mepic) as primary ligand, and the amino acids aspartic acid (H2Asp), glutamic acid (H2Glu) and histidine (HHis) as secondary ligands, were studied in aqueous solution at 25 °C using 1.0 mol·dm?3 KNO3 as the ionic medium. Analysis of the potentiometric data using the least squares computational program LETAGROP indicates formation of the species [Cu(6Mepic)]+, Cu(6Mepic)(OH), [Cu(6Mepic)(OH)2]?, Cu(6Mepic)2 and [Cu(6Mepic)3]? in the binary Cu(II)–H6Mepic system. In the ternary Cu(II)–H6Mepic–H2Asp system the complexes [Cu(6Mepic)(H2Asp)]+, Cu(6Mepic)(HAsp), [Cu(6Mepic)(Asp)]? and [Cu(6Mepic)(Asp)(OH)]2? were observed. In the case of the Cu(II)–H6Mepic–H2Glu system the complexes Cu(6Mepic)(HGlu), [Cu(6Mepic)(Glu)]?, [Cu(6Mepic)(Glu)(OH)]2? and [Cu(6Mepic)(glu)(OH)2]3? were detected. Finally, in the Cu(II)–H6Mepic–HHis system the complexes [Cu(6Mepic)(HHis)]+, Cu(6Mepic)(His) and [Cu(6Mepic)(His)(OH)]? were observed. The species distribution diagrams as a function of pH are briefly discussed. 相似文献
110.
Determination of estrogens in environmental water samples using 1,3‐dipentylimidazolium hexafluorophosphate ionic liquid as extraction solvent in dispersive liquid–liquid microextraction
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Bárbara Socas‐Rodríguez Javier Hernández‐Borges María Asensio‐Ramos Antonio V. Herrera‐Herrera Jose A. Palenzuela Miguel Ángel Rodríguez‐Delgado 《Electrophoresis》2014,35(17):2479-2487
In this work, the potential of a symmetric dialkyl‐substituted ionic liquid (IL), 1,3‐dipenthylimidazolium hexafluorophosphate ([PPIm][PF6]), as extraction solvent in dispersive liquid–liquid microextraction (DLLME) has been studied for the analysis of a group of three natural (estriol, 17β‐estradiol, and 17α‐estradiol) and four synthetic (17α‐ethynylestradiol, diethylstibestrol, dienestrol, and hexestrol) estrogenic compounds as well as one mycotoxin with estrogenic activity (zearalenone) in different types of water samples (Milli‐Q, mineral, and wastewater). Separation, determination, and quantification were developed by HPLC‐DAD and a fluorescence detector (FD) connected in series. Factors influencing the IL‐DLLME procedure (sample pH, amount of IL, type and volume of disperser solvent, ionic strength, and assistance of vortex agitation) were investigated and optimized by means of a step‐by‐step approach. Once the optimum extraction conditions were established (10 mL of water at pH 8, 60 mg of [PPIm][PF6], 500 μL of ACN as disperser solvent and vortex agitation for 1 min), the calibration curves of the whole method (IL‐DLLME‐HPLC‐DAD/FD) were obtained and precision and accuracy were evaluated. It was demonstrated that the developed methodology was repeatable, accurate, and selective with limits of detection in the 0.30–0.57 μg/L and 13.8–37.1 μg/L range for FD and DAD, respectively. Relative recovery values were higher than 85% for the different types of water samples and the Student's t test demonstrated that there were not significant differences between the added and the found concentration. 相似文献