全文获取类型
收费全文 | 153篇 |
免费 | 3篇 |
专业分类
化学 | 92篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 26篇 |
物理学 | 34篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有156条查询结果,搜索用时 15 毫秒
21.
Recently, the PVLAS Collaboration reported an anomalously large rotation of the polarization of light in the presence of a magnetic field in vacuum. As a possible explanation, they consider the existence of a light spin-zero particle coupled to two photons. We propose here a method of independently testing this result using a high-energy photon regeneration experiment (the x-ray analogue of "invisible light shining through walls") using the synchrotron x rays from a free-electron laser. With such an experiment the region of parameter space implied by PVLAS could be probed in a matter of minutes. 相似文献
22.
Edder C Armstrong PB Prado KB Fréchet JM 《Chemical communications (Cambridge, England)》2006,(18):1965-1967
We report the design, synthesis and characterization of new benzothiadiazole- and pyrrole-based copolymers whose solubility and bandgap drastically change after thermal treatment of their thin films. 相似文献
23.
We introduce methods for visualization of data structured along trees, especially hierarchically structured collections of time series. To this end, we identify questions that often emerge when working with hierarchical data and provide an R package to simplify their investigation. Our key contribution is the adaptation of the visualization principles of focus-plus-context and linking to the study of tree-structured data. Our motivating application is to the analysis of bacterial time series, where an evolutionary tree relating bacteria is available a priori. However, we have identified common problem types where, if a tree is not directly available, it can be constructed from data and then studied using our techniques. We perform detailed case studies to describe the alternative use cases, interpretations, and utility of the proposed visualization methods. 相似文献
24.
Adissu Alemayehu Asfaw Juan Aspromonte Kris Wolfs Ann Van Schepdael Erwin Adams 《Journal of separation science》2019,42(1):214-225
Sample preparation and introduction techniques are very critical steps in gas chromatography analysis and particularly in the analysis of volatiles in solid samples. In these cases, they can be divided into two main categories: direct and indirect approaches, based on how the solid sample is treated, i.e. with and without dissolution (or extraction) of analytes from the solid sample. To enable routine application, coupling with sample preparation techniques (especially solid or solvent‐based microextractions) is needed to achieve automation. Here, an overview of the most common sample introduction techniques for gas chromatography with their advantages and drawbacks is presented and discussed, including references to relevant examples. So, this review can serve as guidance for new users. 相似文献
25.
De Gussem K Vandenabeele P Verbeken A Moens L 《Analytical and bioanalytical chemistry》2007,387(8):2823-2832
Confocal Raman spectroscopy is a non-destructive analytical method which is useful to obtain detailed information about the
molecular composition of biological samples. Its high spatial resolution was used to collect spectra of single basidiospores
of macrofungi of the genera Collybia, Gymnopus, Laccaria, Lactarius, Mycena and Russula. These spectra can be divided into three major taxon-related groups, with general compositional differences, such as the
relative amount of lipids compared to proteins. In this study, collapsing of thin-walled spores during storage was often observed,
a phenomenon which has been given little attention in the literature. The Raman spectra are treated with different chemometric
preprocessing techniques, including Savitsky–Golay, standard normal variate (SNV) preprocessing and extended multiplicative
scatter correction (EMSC). By using linear discriminant analysis, approximately 90% of the spectra can be assigned to the
correct genus, but identification on the species level was not possible. 相似文献
26.
De Gelder J De Gussem K Vandenabeele P Vancanneyt M De Vos P Moens L 《Analytica chimica acta》2007,603(2):167-175
In this paper we explore the possibilities of Raman spectroscopy in order to deduce information on the fatty acid composition of bacterial cells. Therefore, representative strains of two bacterial taxa were each cultured in different conditions and in parallel analyzed by Raman spectroscopy and gaschromatographic FAME analysis. Raman spectra of pure fatty acids were recorded and used as reference spectra. The culturing conditions for each strain could be easily distinguished by the fatty acid information retrieved from bacterial Raman spectra. Chemometric techniques such as EMSC and PCA allowed to extract information about groups of fatty acids, that was consistent with the results from FAME analysis. Although the information retrieved from Raman spectroscopy is not as refined as that from FAME analysis, the presented methods could be useful to obtain basic information on the fatty acid present in bacteria when performing Raman spectroscopic analysis for fast whole cell profiling, which provides information for different types of cell components (fatty acids, amino acids, primary metabolites, etc.). 相似文献
27.
28.
29.
V. M. Silonov T. V. Skorobogatova O. V. Kris’ko G. P. Zhmurko 《Moscow University Physics Bulletin》2009,64(4):430-432
Using x-ray analysis, at % the existence of regions with a long-range order of the Cu3Au type has been established in a polycrystalline Pd-30 at % Au solid solution. 相似文献
30.
Steven J. Craythorne Kris Anderson Dr. Fabio Lorenzini Christina McCausland Emily F. Smith Peter Licence Dr. Andrew C. Marr Dr. Patricia C. Marr Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7094-7100
Molecular hydrogenation catalysts have been co‐entrapped with the ionic liquid [Bmim]NTf2 inside a silica matrix by a sol–gel method. These catalytic ionogels have been compared to simple catalyst‐doped glasses, the parent homogeneous catalysts, commercial heterogeneous catalysts, and Rh‐doped mesoporous silica. The most active ionogel has been characterised by transmission electron microscopy, X‐ray photoelectron spectroscopy, and solid state NMR before and after catalysis. The ionogel catalysts were found to be remarkably active, recyclable and resistant to chemical change. 相似文献