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221.
222.
超高效合相色谱-四极杆飞行时间质谱法测定水果和茶叶中手性农药顺式-氟环唑对映体残留 总被引:1,自引:0,他引:1
利用超高效合相色谱-四极杆飞行时间质谱( UPC2-QTOF/MS),建立了顺式-氟环唑在苹果、葡萄和茶叶中的手性对映体拆分与残留分析方法。对合相色谱条件(流动相改性剂及比例、色谱柱温度、背压、辅助溶剂等)进行了优化。样品采用乙腈提取, Cleanert TPT或Pesti-Carb柱净化, Chromega Chrial CCA柱进行分离,以CO2/异丙醇(95:5, V/V)为流动相,流速2.0 mL/min,动态背压13.79 MPa,柱温30℃,离子化辅助溶剂为2 mmol/L甲酸铵的甲醇-水(1:1, V/V),采用超高效合相色谱-四极杆飞行时间质谱分析测定,基质外标法定量。结果表明,本方法的线性范围为0.01 mg/L ~1.00 mg/L,相关系数大于0.99;在0.005,0.025和0.25 mg/kg添加浓度水平下,苹果和葡萄中顺式-氟环唑手性对映体平均回收率(n=6)为67.9%~92.8%,相对标准偏差小于10%,方法定量限为0.005 mg/kg;在0.01,0.05和0.5 mg/kg添加浓度水平下,茶叶中顺式-氟环唑手性对映体平均回收率( n=6)为74.1%~84.0%,相对标准偏差小于8%,方法定量限为0.01 mg/kg。本方法准确、简便、可靠,可以满足残留分析的要求。 相似文献
223.
A porous carbon derived from amino‐functionalized material of Institut Lavoisier as a solid‐phase microextraction fiber coating for the extraction of phthalate esters from tea
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Weiqian Liang Juntao Wang Xiaohuan Zang Chun Wang Zhi Wang 《Journal of separation science》2016,39(7):1331-1338
In this work, a porous carbon derived from amino‐functionalized material of Institut Lavoisier (C‐NH2‐MIL‐125) was prepared and coated onto a stainless‐steel wire through sol–gel technique. The coated fiber was used for the solid‐phase microextraction of trace levels of phthalate esters (diallyl phthalate, di‐iso‐butyl ortho‐phthalate, di‐n‐butyl ortho‐phthalate, benzyl‐n‐butyl ortho‐phthalate, and bis(2‐ethylhexy) ortho‐phthalate) from tea beverage samples before gas chromatography with mass spectrometric analysis. Several experimental parameters that could influence the extraction efficiency such as extraction time, extraction temperature, sample pH, sample salinity, stirring rate, desorption temperature and desorption time, were investigated. Under the optimal conditions, the linearity existed in the range of 0.05–30.00 μg/L for green jasmine tea beverage samples, and 0.10–30.00 μg/L for honey jasmine tea beverage samples, with the correlation coefficients (r) ranging from 0.9939 to 0.9981. The limits of detection of the analytes for the method were 2.0–3.0 ng/L for green jasmine tea beverage sample, and 4.0–5.0 ng/L for honey jasmine tea beverage sample, depending on the compounds. The recoveries of the analytes for the spiked samples were in the range of 82.0–106.0%, and the precision, expressed as the relative standard deviations, was less than 11.1%. 相似文献
224.
The use of etched, chemically modified, capillaries with a rectangular inner channel for open tubular electrochromatography is investigated. Comparisons of separation capabilities are made between circular and rectangular capillaries undergoing the same etching and chemical modification processes. With the long dimension of the rectangular column aligned in the direction of the optical light path, the relative sensitivities of the two capillary geometries are evaluated. The electrochromatographic properties of two catechins found in tea are investigated on the rectangular etched octadecyl-modified capillary. 相似文献
225.
Kralj B Krizaj I Bukovec P Slejko S Milacic R 《Analytical and bioanalytical chemistry》2005,383(3):467-475
Speciation of Al in tea infusions was studied by size exclusion chromatography (SEC) and anion-exchange fast protein liquid
chromatography (FPLC). Fractions were collected throughout the chromatographic separations and Al was determined “off line”
by inductively coupled plasma optical emission spectroscopy (ICP–OES). Black, green, and red tea samples were investigated.
The total concentration of Al in tea infusions was determined by ICP–OES and ranged between 0.5 and 4 mg dm−3. The pH of tea infusions ranged between 5.3 and 5.5. Data from SEC–ICP–OES analysis indicated that 10–35% of total Al in
tea infusions was eluted at a retention volume corresponding to a molecular mass of approximately 3800 Da. The remaining Al
was adsorbed on the column resin. The same tea infusions were also analysed by anion-exchange FPLC–ICP–OES. It was found experimentally
that the same percentage of total Al as from the SEC column was eluted at a retention volume that corresponded to negatively
charged Al-citrate. The remaining Al was adsorbed on the column resin. Identification of Al-binding ligands eluting under
the chromatographic peak was performed by electrospray ionisation tandem mass spectrometry (ES–MS–MS) analysis. It was proven
that ionic Al species in tea infusions (10–35% of the total Al) corresponded to negatively charged Al-citrate. The remaining
species that was adsorbed on the SEC or FPLC columns was most probably bound to phenolic compounds. Speciation of Al in tea
with milk or lemon was also studied. Results for tea with milk indicated that Al-citrate was not transformed and that approximately
60% of total Al was transformed into high-molecular-mass Al species. This fraction was subjected to sodium dodecyl sulfonate
polyacryl gel electrophoresis (SDS–PAGE). The results indicated that Al was occluded by milk proteins (mostly caseins). When
citric acid was added to tea infusions the percentage of negatively charged Al-citrate remained either the same or increased
to 40% of total Al. 相似文献
226.
Eduardo Costa Figueiredo Csar Ricardo Teixeira Tarley Lauro Tatsuo Kubota Susanne Rath Marco Aurlio Zezzi Arruda 《Microchemical Journal》2007,85(2):290-296
A molecularly imprinted polymer has been synthesized for a selective on-line catechol extraction, followed by its spectrophotometric determination in guarana powder, mate tea and tap water samples. A clean-up column, containing a methacrylic polymer + C18 solid phase, was also used in order to enhance selectivity. The imprinted polymer was prepared by bulk polymerization using catechol as template and 4-vinylpyridine as the functional monomer. Permanganate solution was used as spectrophotometric reagent, where Mn(VII) was reduced to Mn(II) by catechol in an acid medium, causing color loss, which was monitored at 528 nm. Physical (extraction flow rate, elution flow rate, coil length) and chemical (nature and concentration of the eluent, potassium permanganate concentration) variables were optimized, and the selectivity was appraised using three molecules (4-chloro-2-methylphenol, 2-cresol, 2-methoxyphenol) similar to catechol. These molecules did not present interference in 1:8, 1:10 and 1:10 (catechol/concomitant) proportions, respectively. The analytical calibration curve ranged from 3.0 up to 100 μmol L− 1 (r > 0.999; seven concentrations levels, n = 3) and the limits of detection (LOD) and quantification (LOQ) were 0.8 and 2.7 μmol L− 1, respectively. Precision, expressed as RSD, was of 3.0% (20 μmol L− 1, n = 10), and the analytical frequency was 15 h− 1. Accuracy was checked by the HPLC technique and the results did not present significant difference at 95% confidence levels according to the t test. 相似文献
227.
Tea glycoprotein (TGC) was purified by Sephadex G-100 gel filtration, and its purity and molecular weight (MW) were determined
by high performance gel permeation chromatography. The gel permeation chromatography (GPC) elution behavior of TGC on an Ultrahydrogel
500 (7.8×300 mm) column was studied using a mobile phase with various concentrations of NaCl. A dextran T system was found
to be unsuitable as MW calibration standards in GPC because the MW of TGC was changed with the change of ionic concentration
in the mobile phase. Thus, the purified TGC obtained in this study was standardized and used instead as the calibration standards
for the determination and comparison of TGCs in tea samples collected from different geographic locations and species varieties.
The GPC was run at 35°C on an Ultrahydrogel 500 column (7.8×300 mm) with a refractive index detector. Distilled water was
used as the mobile phase at a flow rate of 0.6 ml·min−1. The calibration curve was linear over the TGC concentration range of 0.604–6.04 mg·ml−1, with a correlation coefficient of r=0.9997. The TGC mass recovery ranged from 80.4 to 93.2%, with a relative standard deviation of 5.42%. The assay method developed
in this paper was found to be simple, reproducible, and reliable and, thus, ideally suitable for the quality control of TGC-derived
products and raw materials. 相似文献
228.
微量元素与茶叶药用价值的关系初探 总被引:3,自引:0,他引:3
茶叶之所以具有利尿解毒、明目益智、防治心血管疾病等药效,是因为它含有生物孩、维生素、多羟基化合物和Mn、Zn、Cu、Fe等微量元素,两者呈络合状态存在并起协同作用所致. 相似文献
229.
萃取分离—苯芴酮分光光度法测定茶叶中锗的含量 总被引:8,自引:0,他引:8
对苯芴酮分光光度法测定微量锗时的干扰情况进行了考查,发现在H3PO4和HClO4共存体系中,以CCl4萃取Ge,并在显色测定时加入乙酰丙酮作掩蔽剂,能有效地消除干扰,本实验还对茶叶样品的处理方法进行了比较,灰化法时间短,操作简单,Ge损失小。 相似文献
230.
《Electroanalysis》2006,18(17):1643-1648
A new multi‐flow‐through amperometric detectors design was employed as a sensors array system for the detection of flavor related phenols. Relevant parameters of the amperometric detection were examined and optimized. The multivariate analytical signal was processed with chemometric analysis for exploring and classifying the tea beverages. Multivariate regression was used to correlate the astringency value of several tea beverages, obtained by the UNI (Italian Organization for Standardization) sensory profile test, with the signals collected by this amperometric electronic tongue. 相似文献