全文获取类型
收费全文 | 79篇 |
免费 | 0篇 |
专业分类
化学 | 76篇 |
力学 | 1篇 |
物理学 | 2篇 |
出版年
2020年 | 2篇 |
2016年 | 1篇 |
2013年 | 3篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有79条查询结果,搜索用时 31 毫秒
61.
An intercomparison to establish the performance of routine laboratories in the determination of polybrominated flame retardants
in polymers was organised. Commercial poly(ethyleneterephthalate) was fortified with technical pentabromodiphenyl ether, octabromodiphenyl
ether and decabromodiphenyl ether mixtures and with a decabromobiphenyl technical mixture at 0.4–0.8 g/kg. Homogeneity and
stability of the total Br content in the material was confirmed. Thirty-seven laboratories from Europe, Asia and the Americas
submitted results. Relative repeatability standard deviations for individual congeners ranged from 7 to 17%. Relative between-laboratory
standard deviations ranged from 22 to 61%. No significant influence of a common standard, application of a standard method
or method parameters could be identified. The quality and uncertainty of the results of this study are significantly worse
than those reported in the environmental field and indicate a clear need for a learning process among the laboratories involved.
Figure Mandel’s h (between labs): critical level: 1.91 相似文献
62.
Hans Günther Wahl Birgid Tetschner Hartmut M. Liebich 《Journal of separation science》1992,15(12):815-818
3-Carboxy-4-methyl-5-propyl-2-furanpropionic acid (furanpropionic acid), a metabolite commonly found in human blood and urine, is one of the major acidic components which accumulates in the blood of patients with renal failure. Polyunsaturated fatty acids such as eicosapentaenoic acid (C20:5 ω?3) and long chain furan fatty acids, both present in commonly available fish oil capsules, are regarded as possible precursors of furanpropionic acid. Because of its strong binding to albumin and its various interactions with other endogenous and exogenous components, it is of great importance to determine the concentration of furanpropionic acid in blood and urine regularly. Solid phase extraction has been used to concentrate furanpropionic acid from both blood and urine samples. After esterification with ethereal diazomethane, gas chromatographic separation was performed on a HP-1 column (dimethylpolysiloxane). Quantitation with an internal standard was performed by mass selective detection in SIM-mode, qualifier ions being used for identification and accuracy. Fish oil supplementation of the diet of 24 patients for four weeks led to 3-fold and 5 to 6-fold increases in the levels of furanpropionic acid in serum and urine, respectively. 相似文献
63.
64.
65.
The combination of a new thermodesorption module with a cooled injection system now provides a powerful system for direct analysis of volatile trace compounds in gaseous, liquid and solid samples by gas chromatography-mass spectrometry (GC-MS). As a cooled injection system is used for the cryofocusing of the desorbed volatiles the GC-MC system still can be used for the regular analysis of liquid samples. Although plasticizers usually are analyzed by GC-MS after solvent extraction, contaminated solvents and glassware are very well known problems. Analysis of plasticizers in plastic materials by direct thermodesorption instead saves time and avoids cross contaminations. Many medical products are made of plasticized polyvinyl chloride. Extraction of the common plasticizer di(2-ethylhexyl) phthalate (DEHP) into blood will occur, and harmful effects of DEHP in the human body have been suggested. We therefore analyzed 21 different plastic devices which are used for various invasive techniques in medicine by direct thermodesorption GC-MS. In some of the plastics up to 30 different components were identified. By far the most common plasticizer found was DEHP, followed by diethyl and dibutyl phthalates. 相似文献
66.
67.
Mohammed Abu-Bajeh Melanie Cameron Kyung-Hoon Jung Christoph Kappel Almuth L?uter Kyoung-Seok Lee Harip Upadhyaya Rajesh K. Vatsa Hans-Robert Volpp 《Journal of Chemical Sciences》2002,114(6):675-686
The dynamics of formation of oxygen atoms after UV photoexcitation of SO2 in the gas-phase was studied by pulsed laser photolysis-laser-inducedfluorescence ‘pump-and-probe’ technique in a flow reactor.
SO2 at room-temperature was excited at the KrCl excimer laser wavelength (222.4 nm) and O(3Pj) photofragments were detected under collision-free conditions by vacuum ultraviolet laser-induced fluorescence. The use of
narrow-band probe laser radiation, generated viaresonant third-order sum-difference frequency conversion of dye laser radiation
in Krypton, allowed the measurement of the nascent O(3Pj=2,1,0) fine-structure state distribution:n
j=2/nj=1/nj=0 = (0.88 ± 0.02)/(0.10 ± 0.01)/(0.02 ± 0.01). Employing NO2photolysis as a reference, a value of Φ0(3P) = 0.13 ± 0.05 for the absolute O(3P) atom quantum yield was determined. The measured O(3P) quantum yield is compared with the results of earlier fluorescence quantum yield measurements. A suitable mechanism is
suggested in which the dissociation proceeds via internal conversion from high rotational states of the initially excited
SO2(~C1B2 (1, 2, 2) vibronic level to nearby continuum states of the electronic ground state. 相似文献
68.
Combination of enantioselective allylation reactions with a tandem hydroformylation-Fischer indole synthesis sequence as a highly diversity-oriented strategy for the synthesis of tryptamines and homologues was explored. This modular approach allows the substituents at C3 of the indole core, the type of the amine moiety, and the distance of the amine moiety to the indole core in the final synthetic step to be defined. The starting materials required for the hydroformylation step were synthesized via iridium catalyzed enantioselective allylic substitution reactions in high yields and excellent enantioselectivities. The Rh catalyzed hydroformylation step in the presence of phenyl hydrazine, allows the in situ formed aldehyde to be trapped as the hydrazone. Subsequent acid catalyzed indolization furnishes the desired indole structures in moderate to good yields. 相似文献
69.
Summary Elemental analysis of thin films by Rutherford Backscattering Spectrometry (RBS) has been chemometrics-aided in borderline cases: Spectra simulation based on a physical model of Rutherford backscattering is applied for both the prediction of critical analytical parameters and quantitative analysis of overlapping peaks. Non-linear regression using a semi-empirical model of depth profiling allows to improve the determination of concentrations near surface and interface. Statistical tests and multivariate techniques, respectively, enable depth profiles to be judged and compared objectively. Benefits of these methods are demonstrated for high-Tc superconducting and resistor thin layers. 相似文献
70.
V. Liebich 《Fresenius' Journal of Analytical Chemistry》1995,352(5):420-425
Some further possibilities of widespread multivariate methods are checked for usefulness in chemometrical characterising the inhomogeneity of solid materials. The methods are applied to data of ten elements obtained by spark source mass spectrometric milliprobing along radial and azimuthal co-ordinates on the surface of a copper disc sample. Special multivariate control charting reveals locations with significant concentration deviations. Two-factor analysis of variance can distinguish very sensitively between radial and azimuthal contributions. Principal components analysis and hierarchical cluster analysis need three or four main components to explain sufficiently some groups of chemical elements with similar behaviour. Factor analysis clearly confirms four element groups as background factors causing inhomogeneity in a different manner. An extended strategy is proposed how to use which chemometrical method in which sequence for characterising the inhomogeneity.Dedicated to Professor Dr. K. Doerffel on the occasion of his 70th birthday 相似文献