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排序方式: 共有76条查询结果,搜索用时 15 毫秒
31.
Liang Wu Yuzheng WuHanyuan Shen Ping GongLijuan Cao Guangji Wang Haiping Hao 《Analytica chimica acta》2013
The lack of authentic standards represents a major bottleneck in the quantitative analysis of complex samples. Here we propose a quantitative structure and ionization intensity relationship (QSIIR) approach to predict the absolute levels of compounds in complex matrixes. An absolute quantitative method for simultaneous quantification of 25 organic acids was firstly developed and validated. Napierian logarithm (LN) of the relative slope rate derived from the calibration curves was applied as an indicator of the relative ionization intensity factor (RIIF) and serves as the dependent variable for building a QSIIR model via a multiple linear regression (MLR) approach. Five independent variables representing for hydrogen bond acidity, HOMO energy, the number of hydrogen bond donating group, the ratio of organic phase, and the polar solvent accessible surface area were found as the dominant contributors to the RIIF of organic acids. This QSIIR model was validated to be accurate and robust, with the correlation coefficients (R2), R2 adjusted, and R2 prediction at 0.945, 0.925, and 0.89, respectively. The deviation of accuracy between the predicted and experimental value in analyzing a real complex sample was less than 20% in most cases (15/18). Furthermore, the high adaptability of this model was validated one year later in another LC/MS system. The QSIIR approach is expected to provide better understanding of quantitative structure and ionization efficiency relationship of analogous compounds, and also to be useful in predicting the absolute levels of analogous analytes in complex mixtures. 相似文献
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Determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid‐phase microextraction 下载免费PDF全文
Mengliang Zhang Glen P. Jackson Natalie A. Kruse Jennifer R. Bowman Peter de B. Harrington 《Journal of separation science》2014,37(19):2751-2756
A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid‐phase microextraction. Nonequilibrium headspace solid‐phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9–65.7%. Two‐way extracted ion chromatogram data were used to construct calibration curves. The relative error was <±15% and the relative standard deviation was <15%, which are respective measures of the accuracy and precision. The method was validated with certified soil samples and the predicted concentrations for Aroclor 1260 agreed with the certified values. The method was demonstrated to be linear from 10 to 1000 ng/g for Aroclor 1260 in dry soil. 相似文献
34.
A simple and sensitive method was developed and validated for fingerprint analysis of semen zizyphi spinosae (SZS) and simultaneous determination of six flavonoids in SZS by ultra‐high‐performance liquid chromatography coupled to diode‐array detector (DAD). The analysis was performed on an Agilent ZORBAX Eclipse Plus C18 RRHD column. The column was maintained at 40°C and the eluents were monitored with DAD at 270 nm. A gradient elution of acetonitrile and water containing 20 mM sodium dihydrogen phosphate was used. The solvent flow rate was 0.4 mL/min. The method was validated. Standard calibration curves showed good linear behaviors (r=1.000) in the range of 0.33–201.00 μg/mL. Acceptable intra‐day precision (RSD<1.9%), inter‐day precision (RSD<4.0%), repeatability (RSD<4.1%) and recovery in the range of 97.4–104% were obtained. The validated method was successfully applied to obtain the chromatographic fingerprints and the contents of six flavonoids in 23 samples of SZS. The principal component analysis (PCA) had been applied for the chromatographic fingerprint analysis and quantitative analysis of six flavonoids to classify and discriminate the 23 samples of SZS. These results demonstrated that the method was very suitable in the analysis and quality control of SZS. 相似文献
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An efficient and convenient method, biological fingerprinting chromatogram analysis is presented, which is applied to the comparison of fingerprinting chromatograms of the extracts of Chinese herbal medicines after the interaction with biological systems (cell, DNA, protein, etc.). The method was established for the purpose of screening and analysis of the multiple bioactive compounds in herbal medicines. In this work, microdialysis sampling combined with high performance liquid chromatography-mass spectrometry (HPLC-MS) was studied for binding property of MCF-7 and multidrug resistant MCF-7 cell systems. The results showed that pseudolaric acid A (PAA) and pseudolaric acid B (PAB) in the cortex of Pseudolarix kaempferi (Lamb.) Gorden can easily bind to the MCF-7 cells ranging from 0 to 16.3% (PAA) and from 0 to 35.7% (PAB), and another compound, tetrandrine (TET) from the root of Stephania tetrandrae S. Moore, showed higher binding activity with multidrug resistant MCF-7 cells ranging from 0 to 39.9%. 相似文献
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An improved method is proposed for the quantitative determination of multicomponent overlapping chromatograms based on a known transmutation method. To overcome the main limitation of the transmutation method caused by the oscillation generated in the transmutation process, two techniques—wavelet transform smoothing and the cubic spline interpolation for reducing data points—were adopted, and a new criterion was also developed. By using the proposed algorithm, the oscillation can be suppressed effectively, and quantitative determination of the components in both the simulated and experimental overlapping chromatograms is successfully obtained. 相似文献
39.
The combination of photoaffinity labeling (PAL) with modern mass spectrometric techniques is a powerful approach for the characterization of peptide–protein interactions. Depending on the analytical strategy applied, a PAL experiment can provide different levels of information ranging from the identification of interaction partners to the structural characterization of ligand-binding sites. On the basis of LC/MS data generated in the framework of the identification of the binding site of the neuropeptide corticotropin-releasing factor (CRF) on its binding protein (CRFBP), the key role of LC/MS in the characterization of photoadducts on different structural levels was demonstrated. Covalent photoadducts of rat CRFBP (rCRFBP) were obtained by PAL with different mono- and bifunctional benzophenone photoprobes designed on the basis of the sequence of the synthetic CRF fragment human/rat CRF6–33 which binds to CRFBP with high affinity. In view of the stoichiometry, LC/MS analysis revealed that the photoadducts consisted of one molecule of photoprobe and one molecule of rCRFBP. For a further characterization of the photoadducts on the oligopeptide level, enzymatic digests of unlabeled rCRFBP and of the respective photoadduct were compared by peptide mapping monitored with LC/MS. Thereby, it was found that the photoprobe that contained the photophore at its N-terminus labeled the amino acid sequence rCRFBP(34–38), whereas the photoprobe that contained the photophore at its C-terminus labeled rCRFBP(12–26). On the basis of the characterization of the photoadduct formed by rCRFBP and the bifunctional photoprobe that contained photophores on both termini, semiquantitative comparison of different enzymatic digests was accomplished by application of the mass-selective multiple ion chromatogram strategy. 相似文献
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