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1.
Zusammenfassung Es werden die Resultate des isothermen Zerfalles und der Reduktion vonstandardisiertem Ammoniumpolyuranat im Bereich von 285 bis 463° C (in Wasserstoff) wiedergegeben. Der Zerfall zu UO3 wurde schon bei einer Temp. unter 290° C festgestellt, diese Phase blieb jedoch darauf stabil bis 320° C. Zwischen 320° C und 380° C verläuft die Reduktion zu U3O8, über 380° C aber zu UO2. Die Aktivierungsenergien bei der Reduktion von UO3 zu U3O8 und von U3O8 zu UO2 wurden berechnet, und zwar 32,2 kcal/g-mol und 41,7 kcal/g-mol. Die Ergebnisse können mit den Literaturangaben für die Reduktion der einzelnen Phasen UO3 und U3O8 verglichen werden. Die beobachteten Unterschiede weisen auf den Einfluß der Aktivität der Präparate hin.
Mit 4 Abbildungen 相似文献
The isothermal decomposition and reduction of ammonium polyuranate (ADU) was investigated in the temperature interval 285–463° C in hydrogen. The formation of UO3 was noticed below 290° C and this product was stable up to 320° C. U3O8 was stable from this temperature on up to 380° C, where the reduction to UO2 was observed. The activation energies 32,2 Kcal/mole and 41.7 Kcal/mole were calculated for the reduction of UO3 to U3O8 and for the reduction of U3O8 to UO2, respectively. The results are comparable with the published data on reduction of separate phases UO3 and U3O8. Some differences noticed show the influence of the activities of the products.
Mit 4 Abbildungen 相似文献
2.
Substituted pyrrolo[1,2-a]imidazoles and imidazo[1,2-a]imidazoles are prepared in a simple one pot reaction sequence from esters of heterocyclic or aromatic α-amino acids. The reaction involves condensation with acetoine followed by cyclization with either malonodinitrile, ethyl cyanoacetate or cyanamide. 相似文献
3.
4.
Kolar Tjaša Mušič Branka Korošec Romana Cerc Kokol Vanja 《Cellulose (London, England)》2021,28(14):9441-9460
Cellulose - Differently structured aluminum (tri/mono) hydroxide (Al(OH)3 /AlO(OH)) nanoparticles were prepared and used as thermal-management additives to microfibrillated cellulose (MFC),... 相似文献
5.
6.
When dealing with simple phenols such as caffeic acid (CA) and ferulic acid (FA), found in a variety of plants, it is very important to have control over the most important factors that accelerate their degradation reactions. This is the first report in which the stabilities of these two compounds have been systematically tested by exposure to various different factors. Forced degradation studies were performed on pure standards (trans-CA and trans-FA), dissolved in different solvents and exposed to different oxidative, photolytic and thermal stress conditions. Additionally, a rapid, sensitive, and selective stability-indicating gas chromatographic-mass spectrometric method was developed and validated for determination of trans-CA and trans-FA in the presence of their degradation products. Cis-CA and cis-FA were confirmed as the only degradation products in all the experiments performed. All the compounds were perfectly separated by gas chromatography (GC) and identified using mass spectrometry (MS), a method that additionally elucidated their structures. In general, more protic solvents, higher temperatures, UV radiation and longer storage times led to more significant degradation (isomerization) of both trans-isomers. The most progressive isomerization of both compounds (up to 43%) was observed when the polar solutions were exposed to daylight at room temperature for 1 month. The method was validated for linearity, precision as repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The method was confirmed as linear over tested concentration ranges from 1−100 mg L−1 (r2s were above 0.999). The LOD and LOQ for trans-FA were 0.15 mg L−1 and 0.50 mg L−1, respectively. The LOD and LOQ for trans-CA were 0.23 mg L−1 and 0.77 mg L−1, respectively. 相似文献
7.
D. Dobnik M. Kolar J. Komljenovi Nj. Radi 《Fresenius' Journal of Analytical Chemistry》1999,365(4):314-319
The preparation of an ion-selective electrode by chemical treatment of copper wire and its application for the measurements
of copper (II) and iodide ions is described. The proposed reaction mechanism at the sensing surface, which explains the response
of the electrode to Cu2+ and iodide ions, is discussed. The prepared electrode was suitable for direct potentiometric measurements of iodide and copper
(II) in batch experiments down to concentrations of 1 × 10–5 mol L–1. A tubular electrode, prepared in the same way, may be used as a potentiometric sensor in a flow-injection analysis for Cu
(II) and/or iodide determinations.
Received: 4 December 1998 / Revised: 31 March 1999 / Accepted: 6 April 1999 相似文献
8.
Z. I. Kolar W. Martens P. A. J. van Hooft 《Journal of Radioanalytical and Nuclear Chemistry》1990,146(6):391-400
A method for the preparation of a radioactive tracer for sand,56Mn-labelled sand, using NH4MnF3 as the label carrier was developed. The labelling process is based on the adsorption of the label carrier onto the sand particles. 相似文献
9.
From the early precipitation-based techniques, introduced more than a century ago, to the latest development of enzymatic bio- and nano-sensor applications, the analysis of phytic acid and/or other inositol phosphates has never been a straightforward analytical task. Due to the biomedical importance, such as antinutritional, antioxidant and anticancer effects, several types of methodologies were investigated over the years to develop a reliable determination of these intriguing analytes in many types of biological samples; from various foodstuffs to living cell organisms. The main aim of the present work was to critically overview the development of the most relevant analytical principles, separation and detection methods that have been applied in order to overcome the difficulties with specific chemical properties of inositol phosphates, their interferences, absence of characteristic signal (e.g., absorbance), and strong binding interactions with (multivalent) metals and other biological molecules present in the sample matrix. A systematical and chronological review of the applied methodology and the detection system is given, ranging from the very beginnings of the classical gravimetric and titrimetric analysis, through the potentiometric titrations, chromatographic and electrophoretic separation techniques, to the use of spectroscopic methods and of the recently reported fluorescence and voltammetric bio- and nano-sensors. 相似文献
10.
Kokol Vanja Vivod Vera Peršin Zdenka Čolić Miodrag Kolar Matjaž 《Cellulose (London, England)》2021,28(10):6545-6565
Cellulose - Bio-based, renewable and biodegradable products with multifunctional properties are also becoming basic trends in the textile sector. In this frame, cellulose nanofibrils (CNFs) have... 相似文献