全文获取类型
收费全文 | 90篇 |
免费 | 1篇 |
专业分类
化学 | 57篇 |
力学 | 1篇 |
数学 | 13篇 |
物理学 | 20篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1995年 | 3篇 |
1990年 | 8篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有91条查询结果,搜索用时 109 毫秒
1.
2.
3.
Thermal decomposition of zircon mineral was studied in the presence of sodium and potassium hydroxides and in the presence of a waste mixture of hydroxides containing NaOH and KOH in a weight ratio of 23. The process was controlled in such a way that the decomposition products might contain the minimum possible amount of alkali and could thus be applied for the syntheses of zircon pigments without any further exacting treatment.
Zusammenfassung Es wurde die thermische Zersetzung eines Zirkonminerals in Gegenwart von Natrium- und Kaliumhydroxid-sowie in Gegenwart einer Altlauge mit einem Gehalt an NaOH und KOH im Verhältnis zwei zu drei untersucht. Der Prozeß wird derart gesteuert, daß die Zersetzungsprodukte einen möglichst geringen Anteil an Lauge besitzen und so ohne weitere arbeitsaufwändige Behandlungen zur Synthese von Zirkonpigmenten verwendet werden können.
, 23. , , , - .相似文献
4.
The possibility of preparing binary cadmium-calcium cyclotetraphosphate (tetrametaphosphate) by means of thermal dehydration of the appropriate binary dihydrogen phosphate has been studied. The possible formation of this condensation product from the cadmium ions that are often present in the starting phosphoric compound used in the technological preparation of binary calcium cyclotetraphosphates (serving as new special pigments) would represent an important, hygienic method of binding them to an insoluble, less harmful cadmium compound. The maximum proportion of calcium in the binary product, as found by the authors of this paper, amounts to half of the cadmium constituent (in molar terms). That is why Cd2/3Ca1/3(H2PO4)2·2H2O was used as the starting material. Its dehydration was observed mainly by thermal analytical methods under quasi-isothermal-isobaric conditions. Isothermal calcination of the initial binary dihydrogenphosphate was carried out in an electric oven at various temperatures. The reaction products obtained were analysed by chromatography, IR spectroscopy, X-ray diffraction analysis, electron microscopy and AAS. The compositions of the calcinates were determined through extraction with solutions of inorganic compounds and with organic reagents. 相似文献
5.
Žaneta Mesíková Petra Šulcová M. Trojan 《Journal of Thermal Analysis and Calorimetry》2006,84(3):733-736
Synthesis of the green
spinel pigment Co0.46Zn0.55(Ti0.064Cr0.91)2O4 by a novel two-step method of preparation have
been investigated. Inorganic pigments are almost always prepared by a solid
state reaction. It is classical ceramic method which used oxides, hydroxides
or carbonates as precursors. The reaction is performed at temperature higher
than 1300°C and an agent of mineralization is usually present. The presented
novel method of preparation decreases the calcining temperature necessary
for reaching of bright and clear hue of the pigments prepared. Main attention
was focused on the influence of two types of titanium raw materials on the
temperature region of the spinel structure formation and on the colour properties
of the pigments. The mixture of precursors with TiO2
gives a one-phase system when calcining at 1100°C but the colour properties
are more interesting at 1150°C. Thermal stability of this pigment is limited
by temperature 1300°C. This temperature is connected with partial oxidation
of Cr(III) to Cr(VI). Thermal analysis provided the first information about
the temperature region of the pigment formation and determined the thermal
stability of pigment. 相似文献
6.
With the application of thermogravimetry under quasi-isothermal-isobaric conditions, the reaction course of the calcination of Mn(H2PO4 · H2O to give dimanganese cyclotetraphosphate has been studied. Isothermal calcination was also carried out in an electric furnace at various temperatures (200 min). The reaction products were analyzed by chromatography, IR and NMR spectrocopy, and X-ray diffraction analysis. The compositions of the calcinates were determined through extraction with various inorganic and organic solvents.
Zusammenfassung Der Verlauf der Dimangan-cyclotetraphosphat ergebenden Kalzinierung von Mn(H2PO4)2 · H2O wurde thermogravimetrisch unter quasi-isothermen-isobaren Bedingungen untersucht. Isotherme Kalzinierung wurde auch im elektrischen Ofen (200 min) bei verschiedenen Temperaturen ausgeführt. Die Reaktionsprodukte wurden chromatographisch, IR- und NMR-spektroskopisch sowie röntgendiffraktometrisch analysiert. Die Zusammensetzung der kalzinierten Produkte wurde via Extraktion mit verschiedenen anorganischen und organischen Lösungsmitteln bestimmt.
Mn(H2PO4 · H2O. . . - , - - . .相似文献
7.
The
aim of our research was to prepare yellow pigments based on structure of pseudobrookite
Fe2TiO5. Part of Fe was substituted
with Li and Ti from Fe2TiO5
to Li0.05Fe0.07Ti2.44O5.
Synthesis and pigmentary-application properties in the Li2O–Fe2O3–TiO2 system were studied for 800 and 900°C using classical ceramic
method of preparation. The main attention was aimed to usage of four different
sources of titanium compounds as raw materials. We studied the influence of
different sources of titanium compounds on the structural and the colour properties
of the prepared pigments. The thermal analysis was used for characterization
of titanium compounds and determination of their thermal stability. 相似文献
8.
Eremets MI Popov MY Trojan IA Denisov VN Boehler R Hemley RJ 《The Journal of chemical physics》2004,120(22):10618-10623
The high-pressure behavior of nitrogen in NaN(3) was studied to 160 GPa at 120-3300 K using Raman spectroscopy, electrical conductivity, laser heating, and shear deformation methods. Nitrogen in sodium azide is in a molecularlike form; azide ions N(3-) are straight chains of three atoms linked with covalent bonds and weakly interact with each other. By application of high pressures we strongly increased interaction between ions. We found that at pressures above 19 GPa a new phase appeared, indicating a strong coupling between the azide ions. Another transformation occurs at about 50 GPa, accompanied by the appearance of new Raman peaks and a darkening of the sample. With increasing pressure, the sample becomes completely opaque above 120 GPa, and the azide molecular vibron disappears, evidencing completion of the transformation to a nonmolecular nitrogen state with amorphouslike structure which crystallizes after laser heating up to 3300 K. Laser heating and the application of shear stress accelerates the transformation and causes the transformations to occur at lower pressures. These changes can be interpreted in terms of a transformation of the azide ions to larger nitrogen clusters and then polymeric nitrogen net. The polymeric forms can be preserved on decompression in the diamond anvil cell but transform back to the starting azide and other new phases under ambient conditions. 相似文献
9.
Structural transformation of molecular nitrogen to a single-bonded atomic state at high pressures 总被引:1,自引:0,他引:1
Eremets MI Gavriliuk AG Serebryanaya NR Trojan IA Dzivenko DA Boehler R Mao HK Hemley RJ 《The Journal of chemical physics》2004,121(22):11296-11300
The transformation of molecular nitrogen to a single-bonded atomic nitrogen is of significant interest from a fundamental stand point and because it is the most energetic non-nuclear material predicted. We performed an x-ray diffraction of nitrogen at pressures up to 170 GPa. At 60 GPa, we found a transition from the rhombohedral (R3c) epsilon-N(2) phase to the zeta-N(2) phase, which we identified as orthorhombic with space group P222(1) and with four molecules per unit cell. This transition is accompanied by increasing intramolecular and decreasing intermolecular distances. The major transformation of this diatomic phase into the single-bonded (polymeric) phase, recently determined to have the cubic gauche structure (cg-N), proceeds as a first-order transition with a volume change of 22%. 相似文献
10.
Some condensed phosphates, especially cyclo-tetraphosphates have been synthetized as new binary compounds and their existence has been proved. The synthesis of cyclo-CdMgP4O12 is shown as an example. The products crystallize in the monoclinic system (C2c group) and are stable to 900°C. The synthesis is based on a thermal procedure making use of the reversible transformation of cyclo-tetraphosphates to higher linear phosphates (the 1.method) and on a calcination of the starting binary dihydrogenphosphate at quasi-isothermal-isobaric conditions (the 2.method).
Zusammenfassung Einige kondensierte Phosphate, im besonderen Zyklotetraphosphate wurden als neue binäre Verbindungen hergestellt. Als Beispiel wird Zyklo-Cd MgP4 O12 angeführt. Das Produkt kristallisiert monoklin /Gruppe C2/c/ und ist bis 900°C stabil. Die Synthese basiert auf einem thermischen Verfahren unter Anwendung des reversiblen Überganges von Zyklotetraphosphaten zu höhereren linearen Phosphaten /Verfahren 1/ und auf dem Kalzinieren der binären Ausgangsverbindung Dihydrogenphos phat bei quasi-isothermen-isobaren Bedingungen /Verfahren 2/.
$ , . - dMgP4OI2. $ / 2/ $ 900°. $ $ , — $ - .相似文献