全文获取类型
收费全文 | 106篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 85篇 |
力学 | 1篇 |
数学 | 8篇 |
物理学 | 21篇 |
出版年
2023年 | 8篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 1篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 6篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 3篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1930年 | 2篇 |
1926年 | 2篇 |
排序方式: 共有115条查询结果,搜索用时 15 毫秒
1.
2.
3.
The use of stable carbon isotope analysis to detect the abuse of testosterone in cattle. 总被引:3,自引:0,他引:3
The use of stable carbon isotope analysis to detect the administration of anabolic steroids to cattle was investigated. Samples were extracted by solid-phase extraction on C18 cartridges. Stable isotope ratios (13C:12C) were measured by gas chromatography-isotope ratio mass spectrometry (GC-IRMS) of the underivatised extracts. A programmed temperature vaporiser (PTV) injector was installed in the GC-IRMS system, which conferred a number of advantages. First, it allowed large volumes of sample to be injected whilst the injector liner was cool. The solvent was subsequently vented to the atmosphere prior to transfer of the sample to the GC column. Thus a significantly greater amount of sample could be presented for analysis, thereby increasing the sensitivity. Second, by this means virtually all the solvent could be removed prior to analysis. This eliminates solvent peak tailing, which can be a major problem in GC-IRMS. Finally, the PTV allowed the use of higher initial GC oven temperatures, which in turn facilitated the analysis of underivatised steroids by reducing the GC run time and improving the chromatographic peak shape. The carbon isotope composition of 5 beta-androstane-3 alpha,17 alpha-diol, the major metabolite of testosterone found in bovine bile, was measured in bile samples from untreated cattle and from cattle injected intramuscularly with testosterone or a mixture of testosterone esters. There was considerable inter-animal variation in the values obtained and there was no significant difference between samples from treated and untreated animals. However, when the isotopic composition of the metabolite was normalised with respect to that of an endogenous reference compound (cholesterol) in the same sample, the difference between treated and untreated animals become statistically significant. 相似文献
4.
5.
6.
7.
8.
We have investigated and characterised possible sources of variation in measured isotope ratios in the resonance ionisation
mass spectrometry of krypton using resonant transitions at 116.48 and 558.04 nm and ionisation at 1064 nm. Variation arises
when the spectral width of the hyperfine structure of the odd isotopes is comparable to the laser bandwidth and from the alignment
of the first excited state, which depends on the relative polarisations of the laser pulses exciting the resonant transitions. 相似文献
9.
Susann Paul W. Bernd Schweizer Graham Rugg Hans Martin Senn Ryan Gilmour 《Tetrahedron》2013,69(27-28):5647-5659
Herein, we report the synthesis and X-ray structural analysis of a collection of fluorinated metal N-heterocyclic carbenes (Ag, Au, Pd, Rh, Ir) and their precursor salts. The common structural feature of these species is a flanking fluoroethyl group, which is either freely rotating or embedded within a bicyclic framework. Solid state analysis confirmed a gauche conformational preference in all cases with the fluorine adopting a syn clinal arrangement (?[NCCF]~60°) with respect to the triazolium nitrogen at the vicinal position of the NHC. A density functional theory analysis was employed to quantify these effects and evaluate the influence of electronic modulation of the carbenic carbon [(CN+); neutral carbene (C:); metal-bound carbene (CM)], on the relative gauche/anti preference, thus highlighting the potential of this conformational phenomenon as a useful molecular design strategy for controlling the topology of organometallic complexes. 相似文献
10.
J. J. A. Wijs G. D. Elsdon J. R. Stubbs H. Lührig H. Atkinson A. Azadian G. Spitzer F. W. Epple C. H. Manley H. S. Shrewsbury L. V. Cocks E. Nightingale L. Hoton D. W. Steuart P. Smith G. H. Leopold W. J. de Mooy G. van B. Gilmour S. H. Blichfeldt T. Thornley E. L. Smith H. P. Kaufmann E. R. Bolton und C. Revis 《Fresenius' Journal of Analytical Chemistry》1930,80(7-8):303-314
Ohne Zusammenfassung 相似文献