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61.
Quasi-linear fluorescence spectra were recorded at 63 K from polynuclear aromatic hydrocarbons with molecular weights of 378, consisting of seven cata-condensed benzene rings. The sensitivity of the method used is clearly sufficient for nine well resolved spectra to be recorded, even though the solubility of the compounds is low in most solvents. 相似文献
62.
Kantekin Halit Dilber Gülsev Gök Yasar Ocak Ümmühan Abbasoğlu Rıza 《Transition Metal Chemistry》2003,28(1):51-57
The novel (E,E)-dioxime, 5,6:ll,12:17,18-tribenzo-2,3-bis(hydroxyimino)-7,16-dithia-9, 14-dioxo-l,4,10,13-tetraazacyclooctadecane (H2L) has been synthesized by reacting (E,E)-dichloroglyoxime (2) with 2,3:8,9:14,15-tribenzo-4,13-di-thia-6,11-dioxa-l,7,10,16-tetraazahexzadecane (3), prepared by the reaction of N,N-bis(chloroacetyl)-1, 2-phenylene-diamine (1) with 2-aminothiophenol. Mononuclear complexes (4, 5) of this ligand have been synthesized by reacting the vic-dioxime (H2L) with K2PtCl4 and NiCl2 · 6H2O, respectively. Heterotrinuclear complexes (6)and(7) have been prepared by the reaction of (4) and (5) mononuclear complexes with [Cu(MeCN)4]PF6. The structures of the vic-dioxime and its mono and trinuclear complexes were identified by elemental analysis, 1H- and 13C-n.m.r, i.r. and m.s. data. 相似文献
63.
Evaluation of solid-phase microextraction with PDMS for air sampling of gaseous organophosphate flame-retardants and plasticizers 总被引:1,自引:0,他引:1
As an inexpensive, simple, and low-solvent consuming extraction technique, the suitability of solid-phase microextraction (SPME) with polydimethylsiloxane (PDMS) sorbent was investigated as a quantitative method for sampling gaseous organophosphate triesters in air. These compounds have become ubiquitous in indoor air, because of their widespread use as additive flame retardants/plasticizers in various indoor materials. Results obtained by sampling these compounds at controlled air concentrations using SPME and active sampling on glass fibre filters were compared to evaluate the method. A constant linear airflow of 10 cm s–1 over the fibres was applied to increase the extraction rate. For extraction of triethyl phosphate with a 100-m PDMS fibre, equilibrium was achieved after 8 h. The limit of detection was determined to be less than 10 pg m–3. The PDMS–air partition coefficients, Kfs, for the individual organophosphate triesters were determined to be in the range 5–60×106 at room temperature (22–23°C). Air measurements were performed utilising the determined coefficients for quantification. In samples taken from a lecture room four different airborne organophosphate esters were identified, the most abundant of which was tris(chloropropyl) phosphate, at the comparatively high level of 1.1 g m–3. The results from SPME and active sampling had comparable repeatability (RSD less than 17%), and the determined concentrations were also similar. The results suggest that the investigated compounds were almost entirely associated with the gaseous phase at the time and place sampled. 相似文献
64.
Summary A HPLC method for the clean up of PCDD and PCDF samples is presented. The method utilizes the possibility of separating compounds
according to the number of double bonds by using an amino bonded stationary phase. Aliphatics as well as compounds with higher
aromaticity than PCDD/PCDF are removed. In addition, the latter can be collected as one fraction. The fractionation in fast,
done in one step and automated. 相似文献
65.
Reduction of 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacylotetradecane-5,11-diene( 1 ) with sodium borohydride in ethanol generates 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacyclotetradecane( 2 ) in high yield. The macrocyclic ligand 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacyclotetradecane-N,N′-diacetic acid ( 3 ) has been synthesized and characterized. In addition, reaction of ( 2 ) with an excess of acrylonitrile gives 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacyclotetradecane-N,N′-di(2-cyanoethyl) ( 4 ). Several new complexes of these ligands with nickel(II), copper(II) and cobalt(II) have been prepared and identified. The structures of these complexes are proposed on the basis of elemental analysis, 1H, 13C-NMR, IR, UV-VIS spectra, magnetic susceptibility and conductivity data. 相似文献
66.
Faiza Naureen Yasar Shah Sayyed Ibrahim Shah Muhammad Abbas Inayat Ur Rehman Salar Muhammad Hamdullah Khang Wen Goh Fazli Khuda Amjad Khan Siok Yee Chan Mehwish Mushtaq Long Chiau Ming 《Molecules (Basel, Switzerland)》2022,27(13)
Mirtazapine is a tetracyclic anti-depressant with poor water solubility. The aim of this study was to improve the dissolution rate of mirtazapine by delivering the drug as a liquisolid compact. Central composite design (CCD) was employed for the preparation of mirtazapine liquisolid compacts. In this, the impacts of two independent factors, i.e., excipient ratio (carrier:coating) and different drug concentration on the response of liquisolid system were optimized. Liquisolid compacts were prepared using propylene glycol as a solvent, microcrystalline cellulose as a carrier, and silicon dioxide (Aerosil) as the coating material. The crystallinity of the formulated drug and the interactions between the excipients were examined using X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), respectively. The dissolution study for the liquisolid compact was carried out as per FDA guidelines. The results showed loss of crystallinity of the mirtazapine in the formulation and was completely solubilized in non-volatile solvent and equally dispersed throughout the powder system. Moreover, drug dissolution was found to be higher in liquisolid compacts than the direct compressed conventional tablets (of mirtazapine). The liquisolid technique appears to be a promising approach for improving the dissolution of poorly soluble drugs like mirtazapine. 相似文献
67.
Kavil Yasar N. Shaban Yasser A. Alelyani Saeed Saad Al-Farawati Radwan Orif Mohammad I. Ghandourah Mohammed A. Schmidt Mark Turki Adnan J. Zobidi Mousa 《Research on Chemical Intermediates》2020,46(1):755-768
Research on Chemical Intermediates - The effluents containing the discarded water from the textile industry are graded as one of the foremost pollutants in all industrial sectors. The wide... 相似文献
68.
Determination of metoprolol enantiomers in human plasma and saliva samples utilizing microextraction by packed sorbent and liquid chromatography–tandem mass spectrometry
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Hatem Elmongy Hytham Ahmed Abdel‐Aziz Wahbi Ahmad Amini Anders Colmsjö Mohamed Abdel‐Rehim 《Biomedical chromatography : BMC》2016,30(8):1309-1317
A sensitive, accurate and reliable bioanalytical method for the enantioselective determination of metoprolol in plasma and saliva samples utilizing liquid chromatography–electrospray ionization tandem mass spectrometry was developed and validated. Human plasma and saliva samples were pretreated by microextraction by packed sorbent (MEPS) prior to analysis. A new MEPS syringe form with two inputs was used. Metoprolol enantiomers and internal standard pentycaine (IS) were eluted from MEPS sorbent using isopropanol after removal of matrix interferences using aliquots of 5% methanol in water. Complete separation of metoprolol enantiomers was achieved on a Cellulose‐SB column (150 × 4.6 mm, 5 μm) using isocratic elution with mobile phase 0.1% ammonium hydroxide in hexane–isopropanol (80:20, v/v) with a flow rate of 0.8 mL/min. A post‐column solvent‐assisted ionization was applied to enhance metoprolol ionization signal in positive mode monitoring (+ES) using 0.5% formic acid in isopropanol at a flow rate of 0.2 mL/min. The total chromatographic run time was 10 min for each injection. The detection of metoprolol in plasma and saliva samples was performed using triple quadrupole tandem mass spectrometer in +ES under the following mass transitions: m/z 268.08 → 72.09 for metoprolol and m/z 303.3 → 154.3 for IS. The linearity range was 2.5–500 ng/mL for both R‐ and S‐metoprolol in plasma and saliva. The limits of detection and quantitation for both enantiomers were 0.5 and 2.5 ng/mL respectively, in both matrices (plasma and saliva). The intra‐ and inter‐day precisions were presented in terms of RSD values for replicate analysis of quality control samples and were <5%; the accuracy of determinations varied from 96 to 99%. The method was able to determine the therapeutic levels of metoprolol enantiomers in both human plasma and saliva samples successfully, which can aid in therapeutic drug monitoring in clinical laboratories. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
69.
Central European Journal of Operations Research - The objective of this study was to examine the change in efficiency of health care systems of 34 OECD countries between 2000 and 2012, a period... 相似文献
70.
In this paper we are concerned with the oscillation of solutions of a certain more general higher order nonlinear neutral
type functional differential equation with oscillating coefficients. We obtain two sufficient criteria for oscillatory behaviour
of its solutions. 相似文献