全文获取类型
收费全文 | 120篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
化学 | 96篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 5篇 |
物理学 | 24篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 2篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有128条查询结果,搜索用时 15 毫秒
31.
The functionality of proteins is governed by their dynamics. We have performed a systematic investigation on four different proteins in the far-infrared spectral region under control of the two external parameters that have the strongest influence on the dynamics, namely temperature and hydration. The absorption measurements covering the frequency range from 40 cm(-1) to 690 cm(-1) (1-20 THz) close the gap between the well-studied mid-infrared and the recent THz investigations. By preparing the proteins as free-standing films, we achieve unprecedented reproducibility. Besides a featureless slope in the THz range, we can identify absorption peaks characteristic for each protein and others common to several proteins. We fit the spectra to extract the peak positions and suggest assignments for them. The far-infrared absorption spectra of all proteins are basically independent on hydration. By a detailed analysis of the sorption isotherms this can be explained by the low absorption of biological water, which resembles more the behavior of ice than that of liquid water. 相似文献
32.
The lattice thermal conductivity of three II–VI compounds, ZnS, ZnSe, and ZnTe has been analysed on the basis of full Callaway's formalism by considering the scattering of phonons by boundary, point defects, normal, and Umklapp processes. An acceptable agreement with the experimental results is found up to 250 K. From the analysis of the adjustable parameters useful information about the lattice anharmonicity and defects have been obtained. 相似文献
33.
From the optical absorption study of CuInTe2 crystals grown from non-stoichiometric compositions, it has been shown that the sharp increase in the absorption coefficient observed around 0.90 eV corresponds to the transition between the shallow acceptor level and the conduction band and not due to the energy gap as reported earlier. The origin of this shallow acceptor state has been attributed to Te vacancy, which confirms the covalent bonding model for CuInTe2. 相似文献
34.
Mohammad Wasim Mohammad Arif Mohammad S. Iqbal 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(1):249-254
Researcher’s interest is increasing worldwide to study the role of trace elements in brain tissues. This paper discusses the application of k 0-instrumental neutron activation analysis to study the distribution of trace elements in seven different anatomical regions of goat brain. These regions include cerebellum, cerebrum, medulla oblongata, meninges, midbrain, pons and thalamus. The analysis protocol followed 1 h irradiation at 10 MW material testing type nuclear research reactor with nominal thermal neutron flux of 2 × 1013 cm?2 s?1. A total of 14 elements, namely Br, Co, Cr, Eu, Fe, Hg, K, Na, Rb, Sb, Sc, Se, Tb and Zn were determined in all parts. Reliability of the method was assessed by analyzing biological reference material IAEA-336 (lichen). On comparing the analytical results with the healthy human brain data, it showed that eight elements (Eu, K, Na, Rb, Sb, Sc, Se, Tb) were found with relatively higher elemental concentrations in human brain. Principal component analysis revealed distribution of seven parts in different three groups having similar elemental concentrations of elements. 相似文献
35.
Mohammad Wasim Muhammad Daud Mohammad Arif Rameez ul-Islam Sajid Iqbal Yasir Anwar 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):653-659
In the under developed countries, the people of far-flung rural areas still depend to a large extent upon herbal medicines.
At the foundation of usage of herbal medicine is the experience of thousands of years. The present paper deals with the characterisation
of exotic fruits for essential and toxic elements. The samples include Morus nigra, Morus alba, Salvadora persica and Carissa opaca (from low and high altitude). Two standardizations of neutron activation analysis, that is, semi-absolute k
0-instrumental neutron activation analysis (k
0-INAA) and epithermal neutron activation analysis (ENAA) were employed for the quantification of elements. The analysis methodologies
were validated by analyzing the IAEA-336 (lichen) and NIST-SRM-1572 (citrus leaves). Sixteen elements including Br, Ca, Cl,
Co, Cr, Fe, I, K, Mg, Mn, Na, Rb, Sb, Sc Sr, and Zn were determined in all samples. Daily intakes of various elements from
the samples were measured and compared with the dietary reference intakes. Additionally, principal component analysis was
performed to extract information regarding samples and elements. 相似文献
36.
A innovative switchable polarity solvent,based on 1,8‐diazabicyclo‐[5.4.0]‐ undec‐7‐ene and decanol was prepared for enrichment of aluminum in biological sample prior to analysis by flame atomic absorption spectrometry
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A novel switchable solvent (SS) extraction methodology has been used for the enrichment of aluminium (Al) in acid‐digested blood samples of patients with neurological disorders before proceeding to flame atomic absorption spectrometry. 1,8‐Diazabicyclo[5.4.0]undec‐7‐ene and decanol in combination made a SS which reversibly changes from hydrophobic (nonpolar) to hydrophilic (polar) according to switch‐on and switch‐off phenomena in aqueous medium by exposure to anti‐solvent trigger (CO2). The SS polar micro‐emulsion was switched on by bubbling CO2, and switched off by heating from 40 to 70°C with exposure to N2 gas. The changes obtained in the structure and physical properties of the SS due to switching from lower polarity to higher polarity were investigated using Fourier transform infrared spectroscopic analysis. The SS was effectively analysed as an extractive medium for hydrophobic chelate of Al with 3,5,7,2,4‐pentahydroxyflavone (morin) and extracted in SS. Then hydrophobic enriched Al‐morin‐SS was treated with 1.0 M HNO3 and CO2 purging at various time intervals, switch to a miscible polar hydrophilic monophase state. The SS was easily recycled up to six times for further enrichment process. For the developed method, various parameters were optimized such as pH, volume of chelating reagent, CO2 purging time and pressure, and rate of heating. Under favourable conditions, enhancement factor and limit of detection were observed as 25 and 0.47 μg l?1, respectively, for 10 ml of samples/standards solution. The accuracy of the developed method was determined using certified reference material (SRM 3101a), with a standard addition procedure. The method was used for the pre‐concentration of Al in blood samples of patients with neurological disorders. 相似文献
37.
38.
Inductively Coupled Plasma Atomic Emission Spectroscopy measurements of six trace elements were performed on the scalp hair of 155 donors, 73 of which have been diagnosed with Hepatitis C and 82 Controls. Principal Components Analysis (PCA) was employed to visualise the separation between groups and show the relationship between the elements and the diseased state. Pattern recognition methods for classification involving Quadratic Discriminant Analysis and Partial Least Squares Discriminant Analysis (PLS-DA) were applied to the data. The number of significant components for both PCA and PLS were determined using the bootstrap. The stability of training set models were determined by repeatedly splitting the data into training and test sets and employing visualisation for two components models: the percent classification ability (CC), predictive ability (PA) and model stability (MS) were computed for test and training sets. 相似文献
39.
A graph, G, is called uniquely Hamiltonian if it contains exactly one Hamilton cycle. We show that if G=(V, E) is uniquely Hamiltonian then
Where #(G)=1 if G has even number of vertices and 2 if G has odd number of vertices. It follows that every n-vertex uniquely Hamiltonian graph contains a vertex whose degree is at most c log2n+2 where c=(log23−1)−1≈1.71 thereby improving a bound given by Bondy and Jackson [3]. 相似文献
40.