全文获取类型
收费全文 | 108篇 |
免费 | 1篇 |
专业分类
化学 | 90篇 |
数学 | 6篇 |
物理学 | 13篇 |
出版年
2022年 | 4篇 |
2021年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2008年 | 1篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有109条查询结果,搜索用时 15 毫秒
61.
62.
63.
The introduction of Fourier transform methods has not only remarkably enhanced the sensitivity of high-resolution NMR spectroscopy, thus allowing measurements to be made on less sensitive nuclei of the Periodic Table, but also has paved the way for the development of a large number of new experimental techniques. On the one hand, procedures already known have been improved and can now be performed more rapidly, and, on the other, completely new experimental approaches have become available. This situation resulted mainly from the introduction of programmable pulse transmitters and the separation of the experiment into preparation, evolution, and detection. In particular, the concept of two-dimensional spectroscopy has opened up new possibilities important for the analysis of complicated spectra and is able to provide information previously not accessible. As elsewhere, optimum application of the techniques and correct interpretation of the results require sound understanding of the underlying physical principles. Since a rigorous mathematical treatment is complicated and does not necessarily improve the comprehensibility, this article attempts to give an illustrative presentation of the new pulse techniques within the framework of the Bloch vector model. After a short introduction covering the basic principles, one-dimensional pulse techniques that can be applied using standard experimental equipment are dealt with. The main areas of application are signal assignment, sensitivity enhancement for measurements on less abundant nuclei, and selective excitation of individual resonances. Subsequently, the various techniques of two-dimensional NMR spectroscopy are treated: these enable shift correlations for different types of nuclei to be made, the presentation of spin multiplets without overlap, and the analysis of geometrical relations as well as of chemical exchange phenomena. 相似文献
64.
Solutions to the Stephenson-Yang theory of gravity and its generalizations are discussed. By considering the inclusion of a cosmological term in the action spherically symmetric static solutions are presented that do not fall into the vacuum Einstein class. A simple double-duality ansatz is responsible for all the solutions that are discussed.On leave from the Physics Department, Middle East Technical University, Ankara, Turkey. 相似文献
65.
This paper studies sums of periodograms in a random field setting. In a one dimensional or time series setting these can be studied using a method of cumulants, as done by Brillinger. This method does not carry over well to the random field case. Instead one should apply an argument as used by Rosenblatt. In order to have asymptotically correct confidence intervals, one needs to center these sums properly in the random field case. 相似文献
66.
67.
The 1H NMR spectra of various alkyl substituted η3-allyl transition metal complexes (M?Ni, Ru) have been analysed. The chemical shifts of the η3-allyl protons can be calculated using additive increments; the values of the syn and anti vicinal proton-proton coupling constants approach each other on alkyl substitution of the η3-allyl group. 相似文献
68.
69.
70.
The reaction of methylenetrimethylphosphorane with isomeric mixtures of cis and trans 1-t-butyl- or l-cyclohexyl-2-vinylphosphirane produce new phosphino-substituted phosphorus ylids via ring-opening and proton transfer. The products are fully characterized by NMR. 相似文献