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排序方式: 共有199条查询结果,搜索用时 15 毫秒
191.
研究发现,盐酸多巴酚丁胺在碱性条件下能大大增强Luminol—K3Fe(CN)6化学发光强度,基于此,并结合HPLC分离技术,建立起盐酸多巴酚丁胺的HPLC-CL分析新方法。在C18反相键合相为色谱柱,乙腈为流动相的条件下,实现了对人体血清中的盐酸多巴酚丁胺的分离与测定。方法的线性范围为1.0~100μg/L,相关系数为0.9995;检出限为0.76μg/L;相对标准偏差为2.9%(n=11)。  相似文献   
192.
有机-无机杂化膜的研究进展   总被引:15,自引:0,他引:15  
艾晓莉  胡小玲 《化学进展》2004,16(4):654-659
有机-无机杂化膜由于具备了无机膜和有机膜各自的特点,具有良好的分离特性和物化稳定性,因而成为当前膜技术领域新型膜材料研究的热点.本文主要介绍了近年来国内外有机-无机杂化膜的研究现状、杂化膜的制备方法、结构和应用.  相似文献   
193.
Micellar-enhanced ultrafiltration (MEUF) process was explored for obtaining pure water from an aqueous solution containing small amount of trihalomethanes (THMs). A homologous series of polyethylene glycol alkylether was used as nonionic surfactant. To understand effects of membrane hydrophilicity on the performance of MEUF process, membranes for the ultrafiltration were prepared from polysulfone blends containing various amount of a hydrophilic copolymer, poly(1-vinylpyrrolidone-co-acrylonitrile) (P(VP-AN)). An increase in the permeate flux was observed with an increase of the membrane hydrophilicity. The performance of MEUF process in removing THM and surfactant was shown to depend on the membrane characteristics, surfactant characteristics, and operating pressure. The rejections of THM and surfactant were increased with increasing hydrophobicity of surfactant and hydrophilicity of membrane. The rejections of THM examined with hydrophilic membranes were increased with increasing operating pressure, while those examined with hydrophobic membranes were decreased with increasing operating pressure. THM included in water could be removed up to 99% via MEUF process. The performance of MEUF examined with hydrophilic membranes could be explained with the rejection of micelles containing THM, while that examined with hydrophobic membranes could be explained with hydrophobic interactions between surfactant and membrane materials.  相似文献   
194.
In this study, new poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes were prepared firstly and then characterized. Then they were used in the removal of Fe(III) and Co(II) ions from wastewater with a stirred ultrafiltration cell. Also, alginic acid polymer was used as complexing agent to enhance the retention. In the filtration of Fe(III) and Co(II) solutions, the effects of pH, concentration of solutions, and pressure on the retention percentage were examined. Aqueous solutions of Fe(III) and Co(II) were filtrated at the stirred velocity of 400?rpm. The maximum retention percentage was found as 78.66% for Fe(III) solution at the pH of 3.3, concentration of 0.3?×?10?4 M Fe(III) solution, pressure of 40?psi by using 2.5 (w/v)% Poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes. For Co(II) solutions the maximum retention percentage was found as 77% at the pH of 6, concentration of 0.3?×?10?4 M Co(II) solution, pressure of 50?psi by using 2.5 (w/v)%Poly(acrylonitrile-co-methyl acrylate)/cellulose composite membranes.  相似文献   
195.
建立了超滤管净化技术结合高效液相色谱-串联质谱同时测定动物源食品中10种喹诺酮类药物残留的新方法。样品经酸化乙腈提取后,采用50mLMillipore超滤管(截留分子量3kD)净化,离心液氮吹复溶后,经WatersXbridgeC18色谱柱进行分离,以0.1%甲酸-乙腈作为流动相进行梯度洗脱,电喷雾正离子(ESI+)模式电离,多反应监测(MRM)模式检测,外标法定量。结果表明,10种喹诺酮类药物在5.0~100μg/kg浓度范围内线性关系良好,方法的检出限为0.15~0.75μg/kg,定量下限为0.49~2.59μg/kg,在5.0,10,50μg/kg3个加标水平下的回收率为71.4%~85.9%,相对标准偏差(n=6)为3.9%~10.7%。方法简便快速、灵敏度高、重复性好,可用于动物源食品中10种喹诺酮类药物残留的快速确证和定量分析。  相似文献   
196.
    
《Natural product research》2012,26(6):429-434
Abstract

Two new aromatic compounds have been isolated from the reverse osmosis fraction of the olive mill waste-waters and identified as C6-C2 dimers on the basis of their physical features.  相似文献   
197.
    
α-Glucosidase inhibitors have been used for the management of type 2 diabetes mellitus (T2DM) for a long time. The natural α-glucosidase inhibitors from Chinese herbal medicine have become an attractive therapeutic approach for treating T2DM due to their low toxicity. The assays for the discovery of compounds in natural product extracts, however, mostly needed labor-intensive and time-consuming purification. In the current study, the screening of α-glucosidase inhibitors from Coptidis-Rehmanniae herb couple which was composed of Rhizoma Coptidis and Radix Rehmanniae, was investigated by ultrafiltration liquid chromatography/mass spectrometry (UF-LC/MS). As a result, four compounds binding to α-glucosidase were observed and identified to be jatrorrhizine, coptisine, palmatine, and berberine. Subsequently, the sustained off-resonance irradiation collision-induced dissociation Fourier transform mass spectrometry was performed for validation. In addition, the specific binding of ligands to α-glucosidase was demonstrated using UF-LC/MS and the ligands were ranked in order of affinity for α-glucosidase. The relative affinity order for the ligands was coptisine > jatrorrhizine > palmatine ≈ berberine, which indicated that coptisine and jatrorrhizine exhibited more potent α-glucosidase inhibitory activity compared to palmatine and berberine. Therefore, UF-LC/MS might provide not only a powerful tool for screening α-glucosidase inhibitors in complex samples but also a useful platform for bioactive compounds discovery of the efficient anti-diabetic drugs.  相似文献   
198.
    
Glucosinolates are secondary metabolites, as well as representative bioactive therapeutic small molecules, which are found in Camelina seed meal. In this study, an ultrafiltration (UF) membrane was employed to remove protein after ethanol extraction of glucosinolates. After UF, preparative chromatography, based on acidic aluminum oxide, was used to further purify glucosinolates. The impact of different concentrations of NaCl elution buffer at 0.2, 0.5, and 1.0 mol/L on the recovery of glucosinolates was evaluated. The results indicated that elution with a 1.0 mol/L salt solution recovered 91.0% of glucosinolates from the UF permeate. The glucosinolate yield recovered from the seed meal was 9.52 µmol/g. High-performance liquid chromatography analysis showed that only the major glucosinolates peaks at retention times 13.0, 17.6, and 19.2 min appeared. This result indicated that most impurities of UF permeate were removed after anion exchange. Traditional protein removal methods for recovering glucosinolates, such as using heavy metal salt precipitate, are expensive and environmentally harmful. The glucosinolate separation process described herein can be used as a model process for purifying other natural bioactive chemicals from biofuel processing and other agricultural residues.  相似文献   
199.
Lactic acid is a simple and effective indicator for estimating physiological function. Rapid and sensitive detection of lactic acid is very useful in clinical diagnosis. However, the concentration of lactic acid in the physiological state is too low to be detected using traditional Raman spectroscopy. We applied silver colloidal nanoparticles‐mediated surface‐enhanced Raman spectroscopy (SERS) for rapid identification and quantification of lactic acid. The standard SERS spectra of lactic acid were defined and the 1395 cm−1 band intensity was used for quantification from 0.3 to 2 mM (R2 = 0.99). In clinical blood sample measurement, the ultrafiltration (cutoff value 5 kDa) can efficiently reduce background fluorescence to improve SERS performance. We established identical and optimal procedure by adjusting reaction time and volume ratio of serum and nanoparticles to obtain high SERS reproducibility. Finally, we showed that silver colloidal nanoparticles‐mediated SERS technique was successfully applied to detect lactic acid at physiological concentrations in the blood. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
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