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21.
《Journal of separation science》2018,41(7):1625-1634
The presence of pesticides in food items and beverages is a big threat to humankind, and their quantitative estimation with high precision and accuracy is always a challenge for analytical chemists. Hence, a simple and rapid method is proposed for the simultaneous determination of 30 pesticides in beverages (alcoholic and non‐alcoholic drinks). The proposed method hyphenated with triple quadrupole liquid chromatography mass spectrometry has only 2 min chromatographic runtime for the analysis of all the pesticides. All the factors affecting the extraction yield have been optimized using an experimental design; and under optimized conditions, the developed method has been validated. The detection limits for all the pesticides were in the range of 0.001–0.348 μg/L with good linearity in the concentration range of 0.01–80.0 μg/L. The coefficient of determination was in the range of (R2) ≥ 0.977 to 0.999 for all the pesticides. The method was also checked for the precision of the relative standard deviation, which was below 4.75 (intra‐day) and 8.96% (inter‐day). The recovery of the method was 92–138%. 相似文献
22.
多波长叠加近红外吸收光谱法直接测定酒精饮料中的乙醇 总被引:17,自引:0,他引:17
利用乙醇在1382nm,1691nm和1730nm处的吸光度值,采用多波长叠加近红外吸收光谱法测定乙醇的含量。结果表明,乙醇在0%~24%(V/V)浓度范围内呈良好的线性关系;回归方程为: A= 0. 01754+ 0. 04747C;相关系数r=0. 9994。用该法可直接测定葡萄酒、啤酒和黄酒中乙醇的含量,6次平行测定的RSD分别为;葡萄酒4.0%,啤酒2.5%,黄酒2.4%。回收率为97.5%~105.0%,本方法具有操作简便,准确和快速等优点。 相似文献
23.
The mathematical optimization of a continuous alcoholic fermentation process combined with a flash column under vacuum was
studied. The objective was to maximize % yield and productivity in the fermentor. The results using surface response analysis
combined with modeling and simulation were compared withy those obtained when the problem was written as a nonlinear programming
problem and was solved with a successive quadratic programming (SQP) technique. Two process models were evaluated when the
process was optimized using the SQP technique. The first one is a deterministic model, whose kinetic parameters were experimentally
determined as functions of the temperature, and the second is a statistical model obtained using the factorial design technique
combined with simulation. Although the best result was the one obtained using the rigorous model, the values for productivity
and % yield obtained using the simplified model are acceptable, and these models can be used when the development of a rigorous
model is excessively difficult, slow, or expensive. 相似文献
24.
《Biomedical chromatography : BMC》2017,31(8)
Baclofen is used to manage alcohol dependence. This study describes a simple method using liquid chromatography coupled to high‐resolution mass spectrometry (LC‐HR‐MS) developed in plasma samples. This method was optimized to allow quantification of baclofen and determination of metabolic ratio of its metabolites, an oxidative deaminated metabolite of baclofen (M1) and its glucuronide form (M2). The LC‐HR‐MS method on Exactive® apparatus is a newly developed method with all the advantages of high resolution in full‐scan mode for the quantification of baclofen and detection of its metabolites in plasma. The present assay provides a protein precipitation method starting with 100 μL plasma giving a wide polynomial dynamic range (R 2 > 0.999) between 10 and 2000 ng/mL and a lower limit of quantitation of 3 ng/mL for baclofen. Intra‐ and inter‐day precisions were <8.1% and accuracies were between 91.2 and 103.3% for baclofen. No matrix effect was observed. The assay was successfully applied to 36 patients following baclofen administration. Plasma concentrations of baclofen were determined between 12.2 and 1399.9 ng/mL and metabolic ratios were estimated between 0.4 and 81.8% for M1 metabolite and on the order of 0.3% for M2 in two samples. 相似文献
25.
Palma A Lapresta-Fernández A Ortigosa-Moreno JM Fernández-Ramos MD Carvajal MA Capitán-Vallvey LF 《Analytical and bioanalytical chemistry》2006,386(5):1215-1224
A field-portable photometer for potassium determination with disposable sensors has been developed. It can be applied to routine
water and beverage analysis. The disposable sensor is based on ionophore-chromoionophore chemistry. A colour change in the
sensing film is detected by measuring the transmitted intensity with a solid state photodetector. Optical excitation at 660 nm
is emitted by a light-emitting diode (LED). Negative feedback for LED bias and thermal correction were included to improve
system stability. Additionally, a measurement procedure is presented, characterized and validated for in situ photometer use
and real-time results. This simplified procedure is based on prior preparation of the disposable sensor in its acidic form
and on the use of an absorbance ratio as analytical parameter. The only requirement for analysis is prior equilibration with
a buffered sample solution for 3 min and absorbance measurement before and after equilibration. Good sensitivity in the concentration
range 5 μM to 100 mM and very good repetitively and stability were achieved that are comparable to those obtained with bulkier
analytical instrumentation. Given the compact size, low weight, rapid response and low energy requirement of the electronic
photometer developed here, this measurement system is suitable for potassium determination in the field. 相似文献
26.
Raman spectral changes associated with vitrification were measured for ZnCl2·4OROH solutions (ROH=methanol, ethanol and 1-propanol). Solvated ZnCl2 is the only major Zn-species in these solutions at room temperature while the dominant Zn-species stabilized in the glassy alcoholic solutions are ZnCl
3
–
, ZnCl
4
2–
and [Zn(MeOH)6]2+ for the methanol solution, ZnCl2 and ZnCl
3
–
for the ethanol solution and ZnCl2 for the 1-propanol solution. Together with Raman data for aqueous ZnCl2 solutions, the differences in the dominant Zn-species in the glassy alcoholic solutions are discussed in terms of the dielectric constants of solvents (water and alcohols). 相似文献
27.
28.
将纤维素-三(3,5-二甲基苯基氨基甲酸酯)(CDMPC)涂敷于自制的球形氨丙基硅胶上,制备了手性固定相.在正相条件下,用高效液相色谱法在该固定相上直接拆分了农药禾草灵的外消旋体,并系统地选用了多种二元及三元流动相体系对样品进行拆分.实验结果表明,流动相中不同的醇类改性剂及其含量的不同对样品保留时间和立体选择性有不同程度的影响,选用异丙醇改性剂时样品的拆分效果较好,在三元流动相体系正己烷/异丙醇/乙醇中可以实现对禾草灵外消旋体快速有效的拆分. 相似文献
29.
The rheological properties and particle size distributions of cocoa beverage as well as aggregate structures of solid particles were studied to elucidate the effects of microcrystalline cellulose (MCC) on suspension stability of solid particles in cocoa beverage. Fluidity curve, dynamic viscoelasticity, particle size distribution, and SEM observation were made for beverage samples containing 0.1–0.5 wt% MCC and 11 model samples with various combinations of six ingredients. This revealed that cocoa and MCC particles are highly cohered into an aggregate and the aggregated particles further interact weakly with the milk component, leading to stabilization of the whole system of cocoa beverage. 相似文献
30.
Anton Korban Siarhei Charapitsa Radomír abala Sobolenko Lidia Svetlana Sytova 《Journal of mass spectrometry : JMS》2020,55(3)
The potential use of ethanol as an internal standard (IS) for GC‐MS analysis was studied. The paper describes the analysis of spirit drinks and other alcoholic products which consist of a mixture of water, ethanol, and volatile compounds. In the suggested method, ethanol was employed as an IS for the common procedure of volatile compounds quantification. A number of standard solutions of nine compounds with different concentrations was prepared in a water‐ethanol matrix and measured with GC‐MS in the SIM mode. Two possible approaches were suggested to avoid detector saturation during ethanol detection. The first one consisted in using less abundant m/z 47 as quantifiers. These ions mainly correspond to unfragmented heavy ethanol molecules containing one 13C isotope. The second method consisted in reduction of the voltage of MS electron multiplier. The experiment also included the preparation and subsequent dilution of the standard solution and ethanol with water, which determined the linearity of the modified MS response relative to the ethanol content. Analysis of the obtained results revealed that volatile compounds can be successfully accurately determined with GC‐MS by employing ethanol as an IS. Application of the suggested method is not limited to the reported volatile compounds and alcoholic products. 相似文献