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91.
When two or more halides are determined in solution by precipitation titration with silver nitrate as the titrant, significant errors can occur at the first equivalence point as a result of coprecipitation. Errors of up to 33% were found for the first equivalence point for solutions containing mixtures of halides at micromolar levels. The addition of a flocculating agent to the solution reduced coprecipitation by increasing the rate of exchange between the precipitated silver halide and the halide ion remaining in solution. A logarithmic relationship was observed between the charge of the flocculating agent and the logarithmic concentration of the agent needed to minimise coprecipitation. Although flocculating agents reduced coprecipitation, they do not, however, completely eliminate equivalence point errors. Here a new method is presented which effectively eliminates the problem of coprecipitation during precipitation titrations for solutions containing two halides. In order to decrease the possibility of coprecipitation, we used selective complexation of the precipitation ion Ag+ in order to control the AgX solubility. For example, in the case of CF− plus X− (X=Br− or I−), we added sufficient NH3 to form Ag(NH3)+ so that the free Ag+ activity was reduced below that required for theoretical AgCl precipitation in the absence of the other halides. Once the titration of the less soluble halide was completed and the first equivalence point determined, the Ag(NH3)+ complex was destroyed by acidification of the solution to a pH less than 6. The titration is then continued and the second equivalence point determined. Equivalence point errors were reduced to less than 1.5% with careful application of the method. 相似文献
92.
93.
本文首先利用物料平衡和林邦副反应思想分别推导出n1=n2和n1≠n2两种情况时的氧化还原滴定曲线方程,然后应用Origin软件对所推导的不同曲线方程进行解析,建立起以溶液电势E为因变量,滴定分数a为自变量的函数关系,并绘制其滴定曲线。 相似文献
94.
Fifteen international titration standards were evaluated to determine minimum and maximum combined standard uncertainties. Assuming most thorough performance of the analyses revealed minimum values, whereas maximum values of uncertainty were obtained assuming that the analyses had been done under high time pressure. Minimum and maximum uncertainties were compared with the corresponding reproducibility standard deviations. Since the combined standard uncertainty is expected to lie between the reproducibility standard deviation and the maximum combined standard uncertainty, realistic standard uncertainties of individual influence quantities of volumetric and weighing procedures could be calculated. This top-down approach revealed up to 4 times higher uncertainties for volumetric operations compared to the bottom-up approach according to the current literature. Hence, uncertainty due to volumetric operations is obviously strongly underestimated. The present study additionally contains a ranking of the contributions to the uncertainty of titrimetric results. 相似文献
95.
Hans Gantner 《Fresenius' Journal of Analytical Chemistry》1977,284(1):39-40
96.
Annelore Drescher und Rolf Kucharkowski 《Fresenius' Journal of Analytical Chemistry》1979,298(2-3):144-149
Zusammenfassung Für die Vanadiumbestimmung in supraleitenden Verbindungen, z.B. V3Si, sind relative Standardabweichungen < 0,001 erforderlich, wobei die Richtigkeit innerhalb dieser Grenzen garantiert werden muß. Es wird untersucht, unter welchen Bedingungen die volumetrische Titration mit Eisen(II) und die coulometrische Titration mit Eisen(II) und Kupfer(I) mit potentiometrischer Äquivalenzpunktsindikation diese Anforderungen erfüllen. Dafür werden Titrationskurven zur Ermittlung der Lage des Äquivalenzpunktes und der Potentialänderungen in dessen Nähe berechnet. Daraus und aus Untersuchungen zur Stromausbeute bei der coulometrischen Titration lassen sich optimale Analysenbedingungen ableiten. Ein Verfahren zur Vanadiumbestimmung in V3Si wird beschrieben.
Accuracy of the determination of vanadium by volumetric and coulometric titration in silicovanadium
Summary For the determination of vanadium in superconducting compounds, e.g. V3Si, relative standard deviations < 0.001 are required and any systematic error must not exceed this limit. Conditions are investigated, on which the volumetric titration with iron(II) and the coulometric titration with iron(II) and copper(I) using potentiometric detection of the equivalent point fulfill these requirements. Titration curves are calculated to identify the position of the equivalent point and the changes of potential in its vicinity. From these calculations and from investigations of current efficiency in the case of coulometric titration optimum conditions for analysis are deduced. A method for the determination of vanadium in V3Si with high accuracy is described.
Gleichermaßen gilt unser Dank Herrn Dr. R. Stahlberg für die Förderung dieser Arbeit. 相似文献
97.
98.
S. Ebel und R. Krömmelbein 《Fresenius' Journal of Analytical Chemistry》1973,264(5):342-347
Zusammenfassung Für die Auswertung potentiometrischer Titrationen mit Digitalrechnern ist das von Gran angegebene Verfahren gut anwendbar. Bei den Titrationskurven schwacher Säuren ergeben sich allerdings keine Geraden, so daß die üblicherweise durchgeführte lineare Regression zu ziemlich großen Fehlern führen kann. Es wird deshalb die Approximation über Polynome vorgenommen. Aus numerischen Gründen sind dabei Orthogonalpolynome vorzuziehen.Der Deutschen Forschungsgemeinschaft danken wir für die großzügige Unterstützung dieser Arbeiten durch Sach- und Personalmittel. 相似文献
99.
Siegfried Ebel Angelika Seuring 《Angewandte Chemie (International ed. in English)》1977,16(3):157-169
Fully automatic titration systems consist of at least two units: the sample-changing system and the measuring system, the latter including addition of the reagent. These systems are preferably coupled to a computer. The possibilities of fully automatic titration can be best utilized if the sources of error are taken into account and the evaluation procedure optimal for the specific analysis is selected. 相似文献
100.
Ali Akbar Saboury Shahriar Saeidian Mohammad Hosain Sanati Ali Akbar Moosavi‐Movahedi Fatameh Alasti 《中国化学会会志》2001,48(4):827-831
The interaction of myelin basic protein (MBP) from bovine central nervous system with divalent zinc ion was studied by UV‐Vis titration spectrophotometry and isothermal titration calorimetry techniques at 27°C in Tris buffer solution at pH = 7.2. MBP has one binding site for a zinc ion. The binding of a zinc ion is endothermic (ΔH = + 159 kJ mol?1) with a dissociation binding constant of 0.445 μM. The results obtained by two previous methods of isothermal titration spectrophotometry and calorimetry are similar and consistent with the result obtained from a new calculation method of calorimetric data analysis according to the Scatchard plot. 相似文献