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81.
Stir bar sorptive extraction with liquid desorption followed by large volume injection coupled to gas chromatography-quadrupole mass spectrometry (SBSE-LD/LVI-GC-qMS) was applied for the quantification of varietal and fermentative volatiles in sparkling wines. The analytical data were performed by using suitable standards of monoterpene hydrocarbons (α-pinene), monoterpenols (linalool), sesquiterpenoids (E,E-farnesol, Z-nerolidol, and guaiazulene), C13 norisoprenoids (β-ionone), aliphatic and aromatic alcohols (hexanol and 2-phenylethanol), and esters (hexyl acetate and ethyl decanoate) as model compounds. The wine volatiles were quantified using the structurally related standards. The methodology showed good linearity over the concentration range tested, with correlation coefficients ranging from 0.950 to 0.997, and a reproducibility of 9-18%. The SBSE-LD/LVI-GC-qMS methodology allowed, in a single run, the quantification of 71 wine volatiles that can be quantified accurately at levels lower than their respective olfactory thresholds. This methodology was used for assessment of sparkling wine volatiles from different soils, ripening stages, and varieties. The variety and soil influenced significantly the volatile composition of sparkling wines; lower effect was observed for the ripening stage of grapes picked up one week before or after the maturity state. 相似文献
82.
Elisabete M.S. Castanheira Ana S. Abreu Maria-Joo R.P. Queiroz Paula M.T. Ferreira Paulo J.G. Coutinho Nair Nazareth M. So-Jos Nascimento 《Journal of photochemistry and photobiology. A, Chemistry》2009,206(2-3):220-226
Fluorescence properties of the antitumoral methyl 3-(benzo[b]thien-2-yl)-benzothieno[3,2-b]pyrrole-2-carboxylate (BTP) were studied in solution and in lipid bilayers of dipalmitoyl phosphatidylcholine (DPPC), dioleoyl phosphatidylethanolamine (DOPE) and egg yolk phosphatidylcholine (Egg-PC). BTP presents good fluorescence quantum yields in all solvents studied (0.20 ≤ ΦF ≤ 0.32) and a bathochromic shift in polar solvents. The results indicate an ICT character of the excited state, with an estimated dipole moment of μe = 7.38 D.Fluorescence (steady-state) anisotropy measurements of BTP incorporated in lipid membranes of DPPC, DOPE and Egg-PC indicate that this compound is deeply located in the lipid bilayer, feeling the difference between the rigid gel phase and fluid phases.BTP inhibits the growth of three human tumour cell lines, MCF-7 (breast adenocarcinoma), SF-268 (glioma) and NCI-H460 (non-small cell lung cancer), being significantly more potent against the NCI-H460 tumour cells. 相似文献
83.
Santinha DR Marques DR Maciel EA Simões CS Rosa S Neves BM Macedo B Domingues P Cruz MT Domingues MR 《Analytical and bioanalytical chemistry》2012,403(2):457-471
Lipids are important in several biological processes because they act as signalling and regulating molecules, or, locally,
as membrane components that modulate protein function. This paper reports the pattern of lipid composition of dendritic cells
(DCs), a cell type of critical importance in inflammatory and immune responses. After activation by antigens, DCs undergo
drastic phenotypical and functional transformations, in a process known as maturation. To better characterize this process,
changes of lipid profile were evaluated by use of a lipidomic approach. As an experimental model of DCs, we used a foetal
skin-derived dendritic cell line (FSDC) induced to mature by treatment with lipopolysaccharide (LPS). The results showed that
LPS treatment increased ceramide (Cer) and phosphatidylcholine (PC) levels and reduced sphingomyelin (SM) and phosphatidylinositol
(PI) content. Mass spectrometric analysis of a total lipid extract and of each class of lipids revealed that maturation promoted
clear changes in ceramide profile. Quantitative analysis enabled identification of an increase in the total ceramide content
and enhanced Cer at m/z 646.6, identified as Cer(d18:1/24:1), and at m/z 648.6, identified as Cer(d18:1/24:0). The pattern of change of these lipids give an extremely rich source of data for evaluating
modulation of specific lipid species triggered during DC maturation. 相似文献
84.
85.
Laurito TL Mendes GD Santagada V Caliendo G de Moraes ME De Nucci G 《Journal of mass spectrometry : JMS》2004,39(2):168-176
A rapid, sensitive and specific method to quantify bromazepam in human plasma using diazepam as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by liquid-liquid extraction using diethyl ether-hexane (80 : 20, v/v). The extracts were analyzed by high-performance liquid chromatography (HPLC) coupled to electrospray tandem mass spectrometry (MS/MS). Chromatography was performed isocratically on a Genesis C(18) analytical column (100 x 2.1 mm i.d., film thickness 4 microm). The method had a chromatographic run time of 5.0 min and a linear calibration curve over the range 5.0-150 ng ml(-1) (r(2) > 0.9952). The limit of quantification was 5 ng ml(-1). This HPLC/MS/MS procedure was used to assess the bioequivalence of two bromazepam 6 mg tablet formulations (bromazepam from Medley SA Indústria Farmacêutica as the test formulation and Lexotan from Produtos Roche Químico e Farmacêutico SA as the reference formulation). A single 6 mg dose of each formulation was administered to 24 healthy volunteers (12 males and 12 females). The study was conducted using an open, randomized, two-period crossover design with a 3 week washout interval. Since the 90% CI for C(max), AUC(last), AUC(0-240 h) (linear) and AUC((0- infinity )) ratios were all inside the 80-125% interval proposed by the US Food and Drug Administration, it was concluded that the bromazepam formulation from Medley is bioequivalent to the Lexotan formulation for both the rate and the extent of absorption. 相似文献
86.
87.
Instrumental neutron activation analysis for assessing homogeneity of a whole rice candidate reference material 总被引:1,自引:0,他引:1
Lilian Seiko Kato Elisabete A. De Nadai Fernandes Márcio Arruda Bacchi Camila Elias Silvana R. Vicino Sarriés Gabriel Adrián Sarriés Paula Sancinetti Modolo 《Journal of Radioanalytical and Nuclear Chemistry》2013,297(2):271-275
A whole rice reference material was prepared for use in quality control of trace elements in rice and in similar matrices. This study aimed at evaluating the homogeneity of the material. As, Br, Co, Cs, Fe, K, Na, Rb and Zn were determined in the samples by instrumental neutron activation analysis. The material is homogeneous for the elements determined (p < 0.05), except for Co and Fe, which presented dispersion of results much higher than the predicted degree of repeatability. 相似文献
88.
Analysis of low molecular weight aldehydes in air samples by capillary electrophoresis after derivatization with 4-hydrazinobenzoic acid 总被引:1,自引:0,他引:1
This work reports the analysis of selected aldehydes in air samples using capillary electrophoresis (CE). The method is based on the reaction of aldehydes with 4-hydrazinobenzoic acid (HBA) to give the corresponding hydrazones with maximum absorbance at 290 nm. Under optimized CE conditions, the HBA derivatives of four carbonyls (formaldehyde, acetaldehyde, propionaldehyde, and acrolein) were completely separated from one another, in less than 6 min, using a pH 9.3 tetraborate buffer at 0.040 mol L(-1) concentration as background electrolyte. A few method validation parameters were determined revealing good migration time repeatability (< 1.5% CV) and area repeatability (< 2% CV), excellent linearity (50-300 microg/L, r > 0.996) and adequate sensitivity for environmental applications. The limits of detection with respect to each single aldehyde were in the range of 2.7-8.8 ng L(-1). The methodology was applied to the determination of aldehydes indoors. Samples were collected in HBA impregnated octadecylsilica cartridges, at different times during the day. The most abundant carbonyls in the samples were acetaldehyde followed by formaldehyde, with estimated peak concentrations of 4.3 and 2.9 ppbv, respectively. 相似文献
89.
Mauricio P. de Paula Talita M. Lacerda Márcia D. Zambon Elisabete Frollini 《Cellulose (London, England)》2012,19(3):975-992
The present work is inserted into the broad context of the upgrading of lignocellulosic fibers. Sisal was chosen in the present
study because more than 50% of the world’s sisal is cultivated in Brazil, it has a short life cycle and its fiber has a high
cellulose content. Specifically, in the present study, the subject addressed was the hydrolysis of the sisal pulp, using sulfuric
acid as the catalyst. To assess the influence of parameters such as the concentration of the sulfuric acid and the temperature
during this process, the pulp was hydrolyzed with various concentrations of sulfuric acid (30–50%) at 70 °C and with 30% acid
(v/v) at various temperatures (60–100 °C). During hydrolysis, aliquots were withdrawn from the reaction media, and the solid
(non-hydrolyzed pulp) was separated from the liquid (liquor) by filtering each aliquot. The sugar composition of the liquor
was analyzed by HPLC, and the non-hydrolyzed pulps were characterized by viscometry (average molar mass), and X-ray diffraction
(crystallinity). The results support the following conclusions: acid hydrolysis using 30% H2SO4 at 100 °C can produce sisal microcrystalline cellulose and the conditions that led to the largest glucose yield and lowest
decomposition rate were 50% H2SO4 at 70 °C. In summary, the study of sisal pulp hydrolysis using concentrated acid showed that certain conditions are suitable
for high recovery of xylose and good yield of glucose. Moreover, the unreacted cellulose can be targeted for different applications
in bio-based materials. A kinetic study based on the glucose yield was performed for all reaction conditions using the kinetic
model proposed by Saeman. The results showed that the model adjusted to all 30–35% H2SO4 reactions but not to greater concentrations of sulfuric acid. The present study is part of an ongoing research program, and
the results reported here will be used as a comparison against the results obtained when using treated sisal pulp as the starting
material. 相似文献
90.
The development of a DNA biosensor for the detection of cylindrospermopsin, based on self‐assembled monolayers (SAMs) of 4‐aminothiophenol, is investigated. SAMs were characterized by electrochemical reductive desorption. Detection of probe immobilization and hybridization has been achieved by cyclic and square‐wave voltammetry (SWV), using methylene blue (MB) as electroactive indicator. The SWV data obtained in phosphate buffer, with and without NaCl, after MB accumulation, revealed an increase of the redox indicator current peaks after the hybridization step. This behavior is consistent with MB intercalation into DNA, for high ionic strength media and attributed to electrostatic interactions in the absence of salt. Evidence for surface modification is also provided by atomic force microscopy and ellipsometry. 相似文献