全文获取类型
收费全文 | 160篇 |
免费 | 3篇 |
国内免费 | 4篇 |
专业分类
化学 | 69篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 45篇 |
物理学 | 50篇 |
出版年
2019年 | 3篇 |
2018年 | 2篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 2篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 5篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1963年 | 2篇 |
1962年 | 3篇 |
1961年 | 1篇 |
1960年 | 3篇 |
1959年 | 1篇 |
1956年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有167条查询结果,搜索用时 15 毫秒
1.
Varghese Mathai 《Annals of Global Analysis and Geometry》1992,10(2):103-123
We study topological obstructions to the existence of Riemannian metrics of non-negative scalar curvature on almost spin manifolds using the Dirac operator, the Bochner technique, C
* algebras and von Neumann algebras. We also derive some obstructions in terms of the eta invariants of Atiyah, Patodi and Singer. Next, we prove vanishing theorems for the Atiyah-Milnor genus. Finally, we derive obstructions to the existence of metrics of non-negative scalar curvature along the leaves of a leafwise non-amenable foliation on a spin manifold. 相似文献
2.
Experimental conditions have been developed for the titration of uraniumIV with ironIII alum solution, using Rhodamine 6G as a fluorescent indicator. The titration is best carried out at 98–100° in a 2–3N hydrochloric acid medium, under filtered ultraviolet light, using 2.0 ml of 0.05% Rhodamine 6G solution for 30 ml of the titration mixture. A slight excess of ironIII solution quenches the greenish-yellow fluorescence of the dye through inner filter action. With the titration assembly described here, it is possible to determine uraniumIV with an accuracy of about 0.4%. This method appears to be more convenient than the potentiometric titration or the method employing potassium thiocyanate as internal indicator.
Evidence is also presented to show that the reaction between uraniumIV and ironIII is slow at room temperature. 相似文献
3.
S. R. Sagi M. S. Prasada Rao Karri V. Ramana 《Journal of Thermal Analysis and Calorimetry》1981,20(1):93-100
The effect of the thallium(I) concentration on the potentiometric titration of thallium(III) with oxalic acid in 0.1M HNO3 or 0.05M H2SO4 is studied, and conditions are established for the preparation of the thallium(I) bis-oxalato diaquo thallate(III) complex. Chemical analysis of the salt corresponds to the formula T1I(T1III(C2O4)2) · 5 H2O. Thermal decomposition studies on the complex using TG, DTG and DTA techniques indicate the formation of thallium(I) oxalate (stable from 130° to 320°) as the intermediate, the final product being a mixture of thallium(I) oxide and thallium(III) oxide (stable from 520° to 600°). Infrared absorption spectra, X-ray diffraction patterns and microscopic observations are used to characterise the complex and the intermediate. 相似文献
4.
Titrimetric and spectrophotometric methods have been developed for the determination of hydrogen peroxide at mmole and mumole levels respectively. In these methods thallium(III) is used as the oxidant and the reduced thallium(I) is determined oxidimetrically with potassium bromate in the titrimetric method and by measuring the absorbance of thallium(III) at 260 nm in the presence of 0.1M hydrochloric acid and 1M perchloric acid in the spectrophotometric method. Photochemical redox methods for the estimation of hydrogen peroxide in the presence of a number of diverse ions are described. 相似文献
5.
Sagi D Peter-Katalinic J Conradt HS Nimtz M 《Journal of the American Society for Mass Spectrometry》2002,13(9):1138-1148
Application of the negative mode electrospray ionization-quadrupole time-of-flight mass spectrometry (ESI QTOF) tandem MS for determination of substitution patterns by sialic acid and/or fucose and extention by additional LacNAc disaccharide units in single branches of multianternary N-glycans from biological samples is described. Fragmentation patterns which can be obtained by low energy collision-induced dissociation (CID) using the QTOF instrument include cleavage ions, diagnostic for determination of antennarity and for specific structural features of single antennae. Systematic fragmentation studies in the negative ion mode were focussed toward formation of the D diagnostic ion relevant for assignment of 3- and 6-antennae in complex N-glycans carrying three and four antennae in combination with epitope-relevant B- and C-type ions. For validation of this approach ESI QTOF fragmentation of the permethylated analogues was carried out in the positive ion mode. Using this strategy, products of in vitro glycosylation reactions were investigated in order to clarify some general aspects of N-glycan acceptor specificity during biosynthesis. Alpha1-3fucosylation using GDP-fucose along with a soluble form of the recombinant human alpha1-3fucosyltransferase VI was carried out on tri- and tetraantennary precursors to test structural requirements for formation of Le(x) versus sLe(x) motifs. 相似文献
6.
Summary Previous studies have indicated that non-ionic surface active agents, such as n-dodecylhexaoxyethylene glycol monoether, confer considerable protection on silver iodide sols to flocculation by inorganic cations. In the present study the effects of hydrolysis of the flocculating cations, lanthanum, aluminium and thorium have been examined. It was found that with the hydrolysed cations the protective action of the non-ionic surface active agent was considerably diminished. It was deduced that the hydrolysed species are more strongly adsorbed than the nonionic surface active agent and either displace the latter from the surface or form species which are large enough to cause flocculation by interparticle bridging.
With 6 figures and 1 table 相似文献
Zusammenfassung Vorausgehende Untersuchungen haben gezeigt, daß nichtionische oberflächenaktive Substanzen wie n-Dodecylhexaoxyäthylen-glykol-monoäther beträchtliche Schutzwirkung Silberjodidsolen gegenüber Flokkung durch anorganische Kationen verleihen. In der vorliegenden Untersuchung wird die Wirkung der Hydrolyse flockender Kationen, Lanthan, Aluminium und Thorium, geprüft. Es wurde gefunden, daß durch die hydrolisierten Kationen die Schutzwirkung der nichtionischen oberflächenaktiven Substanz beträchtlich vermindert wird. Daraus ist zu schließen, daß die hydrolisierte Ionenart stärker als das nichtoberflächenaktive Agens adsorbiert wird und deshalb das letztere von der Oberfläche entfernt wird oder genügend große interpartikuläre Brücken, bildet, um Flockung zu verursachen.
With 6 figures and 1 table 相似文献
7.
A simple, rapid and convenient redox method has been developed for the estimation of formic acid. Formic acid is photochemically oxidized with thallium(III) in the presence of bromide as catalyst, and the thallium(I) formed is determined by titration with potassium bromate. The procedure can also be used for the estimation of thallium(III) with formic acid as reductant. 相似文献
8.
The use of tin(II) sulphate as a direct reductimetric titrant for thallium(III) has been investigated, with potentiometric and visual detection of the end-point. Some azure dyes are used as redox indicators and Methylene Blue is used as both a redox and an ion-pair indicator. 相似文献
9.
10.
Peter Bouwknegt Jarah Evslin Varghese Mathai 《Communications in Mathematical Physics》2015,337(2):909-954
We introduce spherical T-duality, which relates pairs of the form (P, H) consisting of a principal SU(2)-bundle \({P \rightarrow M}\) and a 7-cocycle H on P. Intuitively spherical T-duality exchanges H with the second Chern class c 2(P). Unless \({dim(M) \leq 4}\), not all pairs admit spherical T-duals and the spherical T-duals are not always unique. Nonetheless, we prove that all spherical T-dualities induce a degree-shifting isomorphism on the 7-twisted cohomologies of the bundles and, when \({dim(M) \leq 7}\), also their integral twisted cohomologies and, when \({dim(M) \leq 4}\), even their 7-twisted K-theories. While spherical T-duality does not appear to relate equivalent string theories, it does provide an identification between conserved charges in certain distinct IIB supergravity and string compactifications. 相似文献