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排序方式: 共有52条查询结果,搜索用时 15 毫秒
1.
Lehto S Lappalainen R Viirola H Niinistö L 《Analytical and bioanalytical chemistry》1996,355(2):129-134
Sb-doped SnO(2) thin films, deposited by atomic layer epitaxy (ALE) for gas sensor applications, have been characterized by secondary ion mass spectrometry (SIMS). Quantification of the depth profile data has been carried out by preparing a series of ion implanted standards. Average concentrations determined by SIMS have been compared with Sb/Sn ratios obtained by X-ray fluorescence (XRF) spectrometry and proton induced X-ray emission (PIXE) spectrometry and have been found to be in good agreement. However, a detection limit of 5x10(18) at cm(-3) could only be obtained because of mass interferences. SIMS data show that the ALE technique can be used to produce a controllable growth and doping of thin films. 相似文献
2.
Sari Lehto Lauri Niinistö Inkeri Yliruokanen 《Fresenius' Journal of Analytical Chemistry》1993,346(6-9):608-611
Summary For the analysis of electroluminescent thin films, X-ray fluorescence (XRF) provides a convenient method as both the concentration of the dopant and the film thickness can be determined rapidly and non-destructively. An XRF method for the determination of thickness and lead concentration in lead doped calcium sulfide thin films was developed. Calibration standards made of polyvinyl alcohol and gelatin as well as filter paper standards were used. In addition, the applicability of a fundamental parameter program UniQuant was investigated. For comparison, the concentrations of lead and calcium were determined after dissolution by atomic absorption spectrometry. Generally, the correlation between the different methods excluding the use of filter paper standards was satisfactory. When the dopant concentration was very low or very high, however, the fundamental parameter program yielded best results. Determination of thicknesses by XRF was made by comparing the sulfur K
intensities of the sample and those of a zinc sulfide standard. A correction factor for molar masses and densities was applied. The thicknesses obtained were compared to those measured with a profilometer after etching and the deviations were found to be less than 10%.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday 相似文献
3.
An on-line method developed for separating plutonium and americium was developed. The method is based on the use of HPLC pump
with three analytical chromatographic columns. Plutonium is reduced throughout the procedure to trivalent oxidation state,
and is recovered in the various separation steps together with americium. Light lanthanides and trivalent actinides are separated
with TEVA resin in thiocyanate/formic acid media. Trivalent plutonium and americium are pre-concentrated in a TCC-II cation-exchange
column, after which the separation is performed in CS5A ion chromatography column by using two different eluents. Pu(III)
is eluted with a dipicolinic acid eluent, and Am(III) with oxalic acid eluent. Radiochemical and chemical purity of the eluted
plutonium and americium fractions were ensured with alpha-spectrometry. 相似文献
4.
The effects of four wash procedures on the concentration of chromium in a pooled sample of human scalp hair are compared. The wash solutions examined are Triton X-100, sodium lauryl sulphate, acetone, and a mixture (1 + 1) of hexane and ethanol. The plateaux reached for hair chromium concentration are functions of the number of washings, and are characteristic for each wash solution. The wash procedure recommended involves two 20-min washes with aqueous 1% sodium lauryl sulphate solution after a hexane rinse. 相似文献
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Excursion to the World of Heptacyclic Compounds Made of Azulenes and Acetylenedicarboxylates
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Yi Chen Erja Lehto Peter Uebelhart Anthony Linden Hans‐Jürgen Hansen 《Helvetica chimica acta》2015,98(7):913-937
Azulenes and acetylenedicarboxylates react under acid catalysis (Brønsted or Lewis) and form (2aRS,8aSR)‐2a,8a‐dihydrocyclopenta[cd]azulene‐1,2‐dicarboxylates as intermediate products, which then dimerize by central bond‐formation between C(2a1) and C(2′a1) and various peripheral C,C′‐atoms of the dihydroazulene fragments, depending on the substituents present. The reactions are often accompanied by the formation of side‐products, such as 2‐(azulen‐1‐yl)fumarates and ‐maleates and others caused by H‐shifts of the primary intermediates. H‐Shifts between the two tetrahydrocyclopenta[cd]azulene parts of the heptacyclic structures were also found. 相似文献
8.
This article deals with empty spacetime and the question of its physical reality. By “empty spacetime” we mean a collection of bare spacetime points, the remains of ridding spacetime of all matter and fields. We ask whether these geometric objects—themselves intrinsic to the concept of field—might be observable through some physical test. By taking quantum-mechanical notions into account, we challenge the negative conclusion drawn from the diffeomorphism invariance postulate of general relativity, and we propose new foundational ideas regarding the possible observation—as well as conceptual overthrow—of this geometric ether. 相似文献
9.
We derive a theorem of exponential decay of correlation functions at high temperature for a general statistical mechanical system following the approach introduced by L. Gross. The theorem is formulated so as to be useful for locality problems in lattice quantum gravity. 相似文献
10.