全文获取类型
收费全文 | 164篇 |
免费 | 5篇 |
专业分类
化学 | 130篇 |
力学 | 4篇 |
数学 | 5篇 |
物理学 | 30篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1957年 | 1篇 |
1952年 | 1篇 |
1951年 | 1篇 |
1948年 | 1篇 |
1944年 | 1篇 |
1943年 | 3篇 |
排序方式: 共有169条查询结果,搜索用时 15 毫秒
91.
The enantiomeric composition of derivatives of new classes of optically active sulphur compounds (variously substituted sulphoxides, sulphoximes, sulphilimines) has been readily determined with the aid of chiral europium shift reagents. 相似文献
92.
A Versatile Organocatalytic Approach for the Synthesis of Enantioenriched gem‐Difluorinated Compounds
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Steve Saulnier Dr. Moira Ciardi Dr. Veronica Lopez‐Carrillo Dr. Andrea Gualandi Prof. Pier Giorgio Cozzi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13689-13695
The combination of a practical and highly enantioselective organocatalytic reaction, which allows the stereoselective introduction of a benzodithiol group, with a fluorination step, gives a new and effective strategy for the stereoselective synthesis of difluorinated building blocks. The benzodithiol group is a versatile and chameleonic group that can be further functionalized before fluorination, giving customized and tailored useful synthetic strategies. As an example of the application of this facile strategy, the effective enantioselective synthesis of difluoroarundic acid is described. 相似文献
93.
94.
95.
Micro synchrotron radiation X‐ray fluorescence (μ‐SRXRF) is a powerful spectroscopy technique that uses synchrotron radiation to induce X‐ray fluorescence in samples and provides exhaustive information on the micron and submicron scale. Among the major advantages of μ‐SRXRF spectroscopy are its nondestructive nature and that samples can usually be analyzed without pretreatment. At the ESRF (Grenoble, France) ID‐21 beamline, we examined PM10 samples collected at two sites in the Province of Trieste, Italy, in order to determine possible correlations among some low‐ to mid‐Z elements (S, Cl, K, Ca, Ti, V, Cr, Mn, and Fe), as well as investigated the possibility of using synchrotron radiation imaging techniques as a way to examine the granulometry of PM10 particles containing the various chemical elements. A consistent significant correlation between Ca and S has been found, which, coupled with the data obtained in a related study, indicates that a major part of the sulfate is present as CaSO4. Granulometry measurement via imaging techniques has shown that some elements such as Fe, Ca, and S are more amenable to this type of analysis than others. Additionally, the spatial homogeneity of a PM2.5 certified reference material (NIST SRM‐2783) has been investigated by analyzing four adjacent areas on the certified sample (total area 1 mm2). The certified reference material has shown a percentage relative standard deviation less than 7% for Al, Si, P, S, Cl, K, Ca, V, Cr, and Fe, and close to 17% for Ti and Mn. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
96.
Del Boccio P Raimondo F Pieragostino D Morosi L Cozzi G Sacchetta P Magni F Pitto M Urbani A 《Electrophoresis》2012,33(4):689-696
Urinary exosomes are released from every renal epithelial cell type facing the urinary space and therefore, they may carry molecular markers of renal dysfunction and structural injury. Here, we present a hyphenated microLC-Q-TOF-MS platform for lipidomics studies applied to investigate the urinary exosome lipid repertoire. Lipids were separated by reversed-phase chromatography using a linear gradient of formic acid 0.2% and tetrahydrofuran, in 40 min of analysis. Features (m/z with associated own retention time) were extracted by MarkerLynx(TM) (Waters) and processed, demonstrating good analytical performance in terms of repeatability and mass accuracy of the microLC Q-TOF MS platform. In particular, a stable retention time (RSD less than 4%) and relative intensity (RSD from 2.9% to 11%) were observed. Moreover, the method takes advantages by the use of a lock spray interface (Waters) that allows readjusting the m/z data after acquisition, obtaining inaccuracy below 6 ppm in measuring the m/z value of the reference compound during chromatographic run. The method was employed in a preliminary application to perform comparative analysis from healthy control subjects and renal cell carcinoma (RCC) patients, in order to possibly highlight differences in lipid composition to be exploited as potential tumor biomarker. Differential lipid composition in RCC urinary exosomes was achieved and tentatively identified by accurate mass, providing a preliminary indication of a relationship between lipid composition of urinary exosomes and RCC disease. Among the total features significantly different in RCC exosomes, the ion at m/z 502.3 was taken as an example for molecular confirmation by MS/MS fragmentation analysis. 相似文献
97.
Xia JL Liu SH Cozzi F Mancinelli M Mazzanti A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(12):3611-3620
Simple model systems based on the 2,11-dithia[3,3]-metaparacyclophane skeleton were synthesized to study the effects of substituents on the intramolecular aromatic-aromatic interactions between benzene rings. X-ray crystallography established that, in their more stable conformations, these metaparacyclophanes featured partially overlapping aromatic rings (interplanar distances of about 3.5??), with the planes of the aromatic systems arranged in a slightly tilted disposition (interplanar angles in the range 5-19°). Calculations showed that these derivatives underwent topomerization by flipping of the meta-substituted ring over the para-substituted one, a process in which the two rings adopted a continuum of edge-to-face dispositions, including an orthogonal one, which were less stable than the starting face-to-face arrangement. The energy barriers to the isomerization process were experimentally determined by variable-temperature NMR spectroscopy, by using an internal temperature standard to assess even minor differences in energy (relative experimental error: (±0.1?kJ?mol(-1)). The variation in the barriers as a function of the different substituents on the interacting ring was small and apparently unrelated to the effect of the substituents on the polarity of the π-systems. An explanation based on the charge-penetration effect seemed more-suitable to rationalize the observed trends in the barriers. 相似文献
98.
Federico Cozzi Gianpiero Adami Pierluigi Barbieri Edoardo Reisenhofer Pietro Apostoli Massimo Bovenzi 《Central European Journal of Chemistry》2010,8(5):1014-1026
PM10 samples were collected during winter and summer seasons at two different sites in the area of Trieste (Italy). The content
of As, Cd, Cr, Mn, Ni, Pb and V in the PM10 samples was determined by inductively coupled plasma-mass spectrometry, with the purpose of evaluating the relevance of PM10 inhalation as a route of human exposure to these elements. The results showed that the ambient air concentration of the aforementioned
elements were below the limits or target values for both sites and season. Site and season-specific correlation analysis was
conducted for the identification of metals with similar origin: very good correlation for the couple Ni-V was found in both
sites and seasons, showing the influence of combustion of heavy oils in PM10 composition. The inter-site and seasonal variability of both PM10 and metal concentrations were examined. A stronger impact by the vehicular traffic on the PM10 and metal concentrations was found for the urban site in both seasons. Because of the great importance of the “Bora” wind
on the local climate, variability of PM10 and toxic elements concentration with wind were analysed, allowing determination of the effect of wind on dilution of the
pollutants for the urban site during both seasons.
相似文献
99.
100.
BODIPYs are renowned fluorescent dyes with strong and tunable absorption in the visible region, high thermal and photo-stability and exceptional fluorescence quantum yields. Transition metal complexes are the most commonly used triplet photosensitisers, but, recently, the use of organic dyes has emerged as a viable and more sustainable alternative. By proper design, BODIPY dyes have been turned from highly fluorescent labels into efficient triplet photosensitizers with strong absorption in the visible region (from green to orange). In this perspective, we report three design strategies: (i) halogenation of the dye skeleton, (ii) donor–acceptor dyads and (iii) BODIPY dimers. We compare pros and cons of these approaches in terms of optical and electrochemical properties and synthetic viability. The potential applications of these systems span from energy conversion to medicine and key examples are presented.BODIPYs offer a versatile platform to build organic triplet photosensitisers for PDT, TTA upconversion and photocatalysis. Tuning their properties provides the opportunity of replacing heavy-metal complexes and can lead to improved sustainability. 相似文献