全文获取类型
收费全文 | 245篇 |
免费 | 3篇 |
专业分类
化学 | 178篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 28篇 |
物理学 | 36篇 |
出版年
2022年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 9篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 19篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1968年 | 1篇 |
1964年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有248条查询结果,搜索用时 0 毫秒
31.
32.
33.
Bing-Xin Yang Yi-Han Kao Janos Kirz Chang-Xin Gu R.N. Bhargava D.A. Cammack R.J. Dalby 《Physics letters. A》1985,113(5):283-288
Transmission measurements of the extended X-ray absorption fine structure above the oxygen K-edge have been made by using a new scintillation detection technique. The absorption spectrum is in close resemblance with the total electron yield spectrum recorded at the same time. This new technique is of interest for studies of soft X-ray absorption spectroscopy for thin films of solid materials. 相似文献
34.
Zusammenfassung Auf Grund derivatographischer Untersuchungen werden die thermischen Zersetzungsreaktionen von Kaliumtrioxalatoferrat(III), Kaliumtrioxalatochromat(III) und Kaliumtrioxalatokobaltat(III) diskutiert. Mit Hilfe der Derivatogramme konnten manche gut erklärbare Zersetzungsetappen und -Verbindungen getrennt werden. Die Zersetzungsprodukte wurden mittels stöchiometrischer Berechnung sowie durch Röntgen-diffraktionsanalyse kontrolliert.
Die Verfasser fühlen sich verpflichtet, Herrn Prof. Dr.E. Pungor für seine wertvollen Ratschläge ihren besten Dank auszusprechen. 相似文献
Summary The thermal decomposition reactions of potassium trioxalatoferrate (III), potassium trioxalatochromate(III) and potassium trioxalatocobaltate(III) are discussed on the basis of derivatographic investigations. Many well-explainable decomposition stages and compounds can be separated with the aid of the derivatograms. The decomposition products were checked by stoichiometric calculation as well as by röntgen diffraction analysis.
Résumé On a discuté les réactions de décomposition thermique des ferritrioxalate de potassium, chromitrioxalate de potassium et cobaltitrioxalate de potassium, d'après les expériences effectuées avec le «Derivatograph». On peut distinguer bien clairement sur le dérivatogramme la plupart des étapes de la décomposition et les produits correspondants. On peut contrôler la nature des produits de décomposition par un calcul stoechiométrique ainsi que par analyse par diffraction de rayons X.
Die Verfasser fühlen sich verpflichtet, Herrn Prof. Dr.E. Pungor für seine wertvollen Ratschläge ihren besten Dank auszusprechen. 相似文献
35.
Grieshaber D Vörös J Zambelli T Ball V Schaaf P Voegel JC Boulmedais F 《Langmuir : the ACS journal of surfaces and colloids》2008,24(23):13668-13676
We developed a new platform at the interface of polyelectrolyte multilayers (PEMs) and electroactive polymers (EAPs) by combining the easy buildup of PEM thin films and the deformation characteristics of the EAPs. The PEM films were made of poly(L-glutamic acid) (PGA) and poly(allylamine hydrochloride) (PAH). After [Fe(CN)6]4- ions (FCIV) were added, cyclic voltammetry (CV) was performed, resulting in a reversible expansion and contraction of the film. The shape change as well as the film buildup prior to the cycling were monitored in situ using the electrochemical quartz crystal microbalance with dissipation monitoring (EC-QCM-D). Electrochemical atomic force microscopy (EC-AFM) images confirmed the rapid shape deformation. The process takes place in an aqueous environment under mild conditions (maximum potential of 600 mV and no pH change), which makes it a promising tool for biomedical applications. In addition, the electrochemically active films are produced using the layer-by-layer (LbL) method that is already established in biotechnology and biomaterials science; therefore, the presented approach can be readily adapted in these areas, bringing about a new possibility for the nanoscale dynamic control of coating thickness in various applications. 相似文献
36.
A numerical investigation is performed addressing the optimal design of stiff structures accounting for uncertainty in loading amplitudes. A minimum volume problem is endowed with a stochastic compliance constraint handling normal distributions and solved adopting mathematical programming. The formulation, originally conceived for a single load case, is extended to handle multiple load cases. Numerical simulations are performed to test the proposed algorithms, pointing out features of the numerical procedures and peculiarities of the stochastic-based optimal solutions achieved for different values of the second-order moments. Comparisons with respect to conventional deterministic layouts are provided as well. 相似文献
37.
Alessandro Marrone Dr. Andrea Renzetti Dr. Paolo De Maria Prof. Stéphane Gérard Dr. Janos Sapi Prof. Antonella Fontana Prof. Nazzareno Re Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11537-11550
The condensation of dialkyl β‐diesters with various aldehydes promoted by TiCl4 has been studied by DFT approaches and experimental methods, including NMR, IR and UV/Vis spectroscopy. Various possible reaction pathways have been investigated and their energy profiles evaluated to find out a plausible mechanism of the reaction. Theoretical results and experimental evidence point to a three‐step mechanism: 1) Ti‐induced formation of the enolate ion; 2) aldol reaction between the enolate ion and the aldehyde, both coordinated to titanium; and 3) intramolecular elimination that leads to a titanyl complex. The presented mechanistic hypothesis allows one to better understand the pivotal role of titanium(IV) in the reaction. 相似文献
38.
39.
Let X and Y be independent identically distributed (i.i.d.) nondegenerate and positive random variables with a common absolutely continuous distribution function F(x). We use the notation Z?=?max(X, Y) and W?=?min(X, Y). In the present paper, we prove that ${\frac{(Z - W)}{(Z + W)}}$ and (Z +?W) are independent if and only if X and Y have gamma distribution. 相似文献
40.
Yuri Park Godwin A. Ayoko Janos Kristof Erzsébet Horváth Ray L. Frost 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1137-1142
High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications.
In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised
by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays
intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this
study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition.
There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant
to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability
of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important
in the synthesis and processing of organoclays for environmental applications. 相似文献