首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   107篇
  免费   5篇
  国内免费   3篇
化学   45篇
综合类   2篇
物理学   68篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2018年   4篇
  2017年   3篇
  2016年   6篇
  2015年   6篇
  2014年   1篇
  2013年   10篇
  2012年   10篇
  2011年   7篇
  2010年   11篇
  2009年   7篇
  2008年   6篇
  2007年   1篇
  2006年   8篇
  2005年   2篇
  2004年   6篇
  2003年   8篇
  2002年   3篇
  2001年   1篇
  2000年   3篇
  1999年   2篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
排序方式: 共有115条查询结果,搜索用时 437 毫秒
101.
The Ru kiln is one of the five famous kilns of the Song Dynasty in China, and it is said that the Ru Porcelain is the chief of the five. As the Ru Porcelain was produced for a short time in history, no other than approximately 20 a, and exclusively fired only for the royalty, the remains are rather rare, with the total number falling short of one hundred pieces all over the world excluding the ones excavated in Qingliang Temple, Baofeng County, Henan Province. Especially, the celadon of …  相似文献   
102.
The work presents an investigation on metal availability in sediments during 13 months using the dispersive-energy X-ray fluorescence (EDXRF) and atomic emission spectrometry with induced argon plasma (ICP-OES) techniques and single extraction (0.1 mol l−1 HCl) and Tessie’s sequential speciation methods. The EDXRF technique could yield essentially the same profile as ICP-OES for the seasonal variation of metals in sediments, but in a more practical way. The sequential extraction procedure (SEP) was more efficient in metal dissolution than single extraction. The Pb, Ni, Al, Cr, and Fe elements were less efficiently extracted with single extraction in relation to sequential extraction. For Co both methodologies were equivalent, but for Cu and Mn the extraction was higher with single extraction. Single extraction does not mobilize Pb, Ni, Al, Cr, and Fe adsorbed on oxides and bound to organic matter. However for Cu and Mn, not only extracted these metals from the four fractions, but it also dissolved part of the fifth fraction (residual). Principal Component Analysis discriminated seasonal variations in the content of several metals, mainly Fe, Co, Ni, and Zn. The mobility of metallic ions in the sediments is conditioned to the seasonal flow of organic and inorganic material coming from the river or by the erosion of adjacent soils.  相似文献   
103.
The aim of this work was to determine the concentrations of some essential and toxic elements in the muscle of ten species of commercial fish consumed in Portugal. We combined two different techniques for determination of the elements—energy-dispersive X-ray fluorescence (EDXRF) was used to quantify K, Ca, Fe, Zn, Se, Rb, and Sr and flame atomic-absorption spectrometry for analysis of Cr, Ni, Cu, Cd, Hg, and Pb. The latter technique was used because of its higher sensitivity, because these elements were not detected by EDXRF. The results obtained show a similar pattern for the trace elements. K and Ca are present at the highest concentrations in all the samples studied, from 0.6–1.3% and from 0.04–0.08%, respectively, followed by Zn, Fe, Sr, Se, and Rb. Sr is present at higher concentrations than Rb in all the species studied except meagre. Concentrations of the elements in octopus do not follow this pattern—Fe is present at a higher concentration than Zn. Low concentrations of Cr (0.66–1.5 g g–1), Ni (0.11–0.24 g g–1), Cd (0.01–0.08 g g–1), Hg (0.49–2.74 g g–1), and Pb (0.02–0.06 g g–1) were observed in all the samples analysed. The concentration of Hg was highest in Helicolenus dactylopterus—5.4 g g–1 in one sample.  相似文献   
104.
The energy-dispersive X-ray fluorescence spectrometer for analysis of conventional and micro-samples using pinhole collimators of various sizes is developed. The measurements can be performed in the air or, in order to decrease the absorption of long-wavelength radiation of low-Z elements, in helium atmosphere. The sample is excited by the air-cooled Rh target X-ray tube of ca. 100 μm nominal focal spot size and maximum power 75 W. The X-ray spectra of the samples are collected by thermoelectrically cooled Si-PIN detector. The tungsten pinhole collimators of the size holes from 50 to 2000 μm are placed between primary filter and analyzed sample to reduce size of analyzed area. The sample can be moved using the XY stage. The position of the sample is monitored by CCD camera and two laser pointers. The beam spot sizes for various collimators are evaluated by the thin-wire and knife-edge methods. Beside the beam spot sizes, the loss of radiation intensity and the changes of spectral distribution of the incident radiation caused by applying various collimators are also investigated. The sample-surface-down geometry in the designed spectrometer allows for a simple analysis of various samples: solutions, loose powders, solid samples of conventional size and micro-samples.  相似文献   
105.
Trace element analysis of some fly ash samples and soil samples have been carried out by Energy Dispersive X-Ray Fluorescence technique. Fourteen elements namely K, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Se, Rb, Sr and Pb have been quantified in the fly ash samples by this technique. It was found that there is no huge concentration difference between the fly ash and soil samples as a result of which fly ash can be used as soil manure without any adverse impact on the plants.   相似文献   
106.
景德镇窑和德化窑是南方白釉瓷窑口中最具有代表性的两个窑口。该文利用能量色散X射线荧光光谱分析仪,对30件宋、元、明时期的德化白瓷以及元代景德镇枢府白瓷样品进行了测试,并从时空角度对比分析了不同白瓷样品胎釉的组成特征。结果表明,景德镇枢府白瓷胎釉组成铁含量均明显偏高,而德化白瓷胎釉组成中的钾含量均明显偏高,且随着时间发展具有上升趋势,这应是德化雕塑白瓷异军突起的主要原因。  相似文献   
107.
 Art Nouveau (Tiffany, Loetz) and modern (Jack Ink, Strini Art Glass) iridescent glass fragments were characterized using energy dispersive X-ray fluorescence analysis (EDXRF) and energy dispersive X-ray microanalysis in a scanning electron microscope (SEM/EDX) in combination with factor analysis in order to obtain clustring. A character istic of Tiffany glass fragments is leaded bulk glass, whereas in the case of Loetz K-Ca-Si bulk glass could be determined. Modern glass fragments show a high amount of Na (7 wt% in the bulk of Jack Ink) and 0.6–1.5 wt% Sr in the bulk of Strini Art Glass. The contents of Si and Ca are similar to Loetz glass. Furthermore, the differences in the structure of the glass artifacts could be determined. The cross-sections of Tiffany show a layered structure of the bulk without a specific surface layer whereas the cross-sections of Loetz glass reveal a homogeneous bulk material with one or two homogeneous surface layers in the BE-image. In the case of the Jack Ink a homogeneous bulk glass and an inhomogeneous multilayered surface could be determined. Strini Art Glass show a homogeneous bulk glass and a homogeneous surface layer in the backscattered electron image.  相似文献   
108.
制作了一组表面具有不同厚度镀铬层的45碳钢标准块,并应用能量色散X荧光光谱法(EDXRF)对镀层厚度进行了测度基数据处理中运用Newton迭代法对工作曲线进行了拟合,结果满意。  相似文献   
109.
定窑是我国宋代五大名窑中唯一以生产白瓷而闻名于世的窑厂,其高超的刻印花纹技术及首创的支圈覆烧工艺,对国内外许多窑场产生了深远的影响。采用(energy dispersive X-ray fluorescence, EDXRF)探索了历代定窑白瓷的组成配方,并采用X射线吸收精细结构(XAFS)法分析了瓷釉中Fe元素的价态,以探讨定窑白瓷的相关烧制工艺。研究发现,定窑白瓷瓷胎具有典型北方瓷器“高铝低硅”的特征,并在瓷胎中特意添加了富含CaO的矿物原料,对瓷胎的烧结有一定的促进作用。瓷胎中的TiO2应主要是高岭土原料中的杂质。定窑白瓷瓷釉具有“高钙高镁”特征,基本属于钙镁釉或钙镁碱釉。其瓷釉配方中应含有一定量的白云石或滑石。瓷釉中K2O的含量逐步增加,反映了定窑瓷釉由钙镁釉向钙碱釉发展演变的过程。此外,根据瓷釉中的Al2O3,MnO和P2O5等含量的特征,可以推测釉料配方中应添加了草木灰和高岭土。由XAFS分析结果可知,晚唐五代时期定窑白瓷釉中Fe3+比例最高,金代次之,宋代最低,不同时期定窑白瓷皆是在还原气氛中烧成。宋金时期定窑白瓷白中泛黄可能由于燃料煤中富含的硫在燃烧过程中与瓷釉反应,生成Fe-S化合物所致。  相似文献   
110.
This paper presents a systematic micro-analytical study for the assessment of the influence of a typical hot-air blow-in heating system on the generation, transport and deposition of suspended particulate matter (SPM) in the church of Rocca Pietore (Italian Alps). This kind of heating system is very popular in cold regions due to its fast response and economic properties. The size, chemical composition and abundance of individual particles responsible for the negative impact on the displayed artworks are determined by ultra-thin window EPMA. EDXRF is used to determine the bulk chemical composition of SPM. Some gaseous pollutants (SO2, NO2 and O3) are sampled with the application of passive diffusion tubes and quantified with ion-chromatography and spectrophotometry. It is pointed out that several deterioration processes, such as the abrasion of the plastered walls, the re-suspension of the particulate pollution and the generation of NO2 gas, arise mainly from using the heating system. Each of these observations is a concern for the preservation of the displayed works of art.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号