全文获取类型
收费全文 | 93篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 80篇 |
力学 | 1篇 |
数学 | 7篇 |
物理学 | 12篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1992年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1963年 | 2篇 |
1941年 | 1篇 |
排序方式: 共有100条查询结果,搜索用时 15 毫秒
91.
U Myint Ba Han Khin Mg Myoe Aung Kywe Thida J. Tölgyessy 《Journal of Radioanalytical and Nuclear Chemistry》1994,187(2):117-122
A single line system with a detector of radioactivity was used for the determination of60Co. In the determination, no additional chemistry is involved and limited dispersion is desirable. For this application, the FIA system is used only as a transport system for the sample up to the detector. 相似文献
92.
The synthesis of a series of ReI, RuII, and OsII complexes that contain rigid polyphosphine/cumulene spacers is reported here. These cumulenic ligands, namely, 1,1',3,3'-tetrakis(diphenylphosphino)allene (C3P4) and 1,1',4,4'-tetrakis(diphenylphosphino)cumulene (C4P4), utilize diphenylphosphino linkage components to coordinate to the metal-polypyridyl or metal-carbonyl units. Characterization of all mono-, homo-, and heterobimetallic complexes is achieved using 31P(1H) NMR, IR, and fast atom bombardment mass spectroscopy (FAB/MS) and elemental analysis. The two ReI homobimetallic complexes were also characterized by single-crystal X-ray structure determination, which provided the structural evidence of a 90 degrees rotation between the C3 and C4 adducts causing a change in the electrochemical behavior. The ground-state electronic absorption and redox interactions, along with the excited-state photophysical characteristics, are also explored. Electrochemical studies showed that an increase in the carbon chain length resulted in a greater amount of sigma-donation from the ligand to the metal centers, as well as a greater amount of electronic communication between the metal termini of the bimetallic species. The electronic absorption and emission spectra of the new complexes were also determined and characterized. The lifetimes of the excited-state luminescence of the ReI mono- and homobimetallic complexes were found to be an order of magnitude shorter than the lifetimes of the heterobimetallic complexes containing the RuII and OsII moieties. Excited-state energy transfer was observed from the higher MLCT excited state of the ReI centers to the lower energy MLCT excited state of the RuII and OsII centers on the following basis: no ReI-based emission was detected in the steady-state emission measurements, the time-resolved decay traces were fitted to only single-exponential decays, and the quantum yields were identical for each compound at two different excitation wavelengths where different percentages of the metal-based chromophores were excited. 相似文献
93.
U Myint J. Tölgyessy Naing Win Khaing San Ba Han Khin Mg Myoe 《Journal of Radioanalytical and Nuclear Chemistry》1994,187(5):345-349
Radiometric Flow Injection Analysis of a radioactive (131I) sample is described. For analysis an ASIA (Ismatec) analyzer with a NaI (Tl) scintillation detector was used. 相似文献
94.
Nonionic surfactant and temperature effects on the viscosity of hydrophobically modified hydroxyethyl cellulose solutions 总被引:2,自引:0,他引:2
Nonionic surfactant and temperature effects on the viscosity of hydrophobically modified hydroxyethyl cellulose (HMHEC) solutions are investigated experimentally. Weak shear thickening at intermediate shear rates takes place for HMHEC at moderate concentrations and becomes more significant at lower temperatures. While this amphiphilic polymer in surfactant-free solution does not turn turbid by heating to 95 degrees C, its mixture with nonionic surfactant shows a lower cloud point temperature than does a pure surfactant solution. For some mixture cases, phase separation takes place at temperatures as low as 2 degrees C. The drop of cloud point temperature is attributed to an additional attractive interaction between mixed micelles via chain bridging. With increasing temperature, the viscosity of an HMHEC-surfactant mixture in aqueous solution first decreases but then rises considerably until around the cloud point. The observed viscosity increase can be explained by the interchain association because of micellar aggregation. 相似文献
95.
Ana C. Carvalho João C. S. Lira Thaís M. Pereira Sebastião C. Silva Simone Y. Simote-Silva Fernando K. D. Oliveira 《Natural product research》2019,33(4):557-562
Four compounds were isolated from roots and aerial parts of Pluchea sagittalis (Asteraceae), 3, 5-dihydroxy-6, 7, 3′, 4′-tetramethoxiflavunol (1), 5-hydroxymethylfurfural (2), 3, 4-dimethoxybenzaldehyde (3) and 2, 3, 4-trihydroxybenzaldeyde (4). Their herbicidal potential was detected by polarographic techniques. All of them inhibited the non-cyclic electron transport on basal, phosphorylating and uncoupled conditions from H2O to methylviologen (MV); thus, they act as Hill reaction inhibitors. Studies on fluorescence of chlorophyll a (ChL a) indicated they have different modes of interaction and inhibition sites on the photosystem II electron transport chain; 1–3 have interacted with the acceptor side while 4 has interacted at the donor side. 相似文献
96.
97.
Andr Mayer Tha Pith Guo-hua Hu Morand Lambla 《Journal of Polymer Science.Polymer Physics》1995,33(12):1793-1801
This article, the second part of this series, concerns the development of an analogy between the peel behavior of pressure-sensitive adhesives and the dynamic mechanical properties of the corresponding copolymers. The adhesive copolymers used were synthesized by emulsion polymerization processes. Their physical and dynamic mechanical properties were characterized and presented in Part I of this series. In this study, an analogy was built up between the force in a peel test as a function of peel velocity, Fp(vp), and the loss modulus of the adhesive as a function of the angular frequency in a dynamic mechanical experiment, G″(ω). This was done by superimposing the curves of Fp versus vp and those of G″ versus ωβ0/β, where β0/β is a shift factor with β being a parameter in the Kaelble theory and β0 being some reference value of the Kaelble parameter. When the curves of Fp ~ vp and those of G″ ~ ωβ0 were plotted together, they followed the same trend of variation. This analogy between G″(ωβ0/β) and Fp(vp) was further confirmed by the fact that the apparent activation energies of the primary glass transition for G″(ω) and Fp(vp) are virtually the same, suggesting that the analogy between G″(ω) and Fp(vp) is dictated by the glass transition. The existence of the above-mentioned analogy between G″(ω) and Fp(vp) shows that the performance of an adhesive can be evaluated or predicted from the dynamical loss modulus of the corresponding (co)polymer. ©1995 John Wiley & Sons, Inc. 相似文献
98.
Cailleau T Cooke JW Davies SG Ling KB Naylor A Nicholson RL Price PD Roberts PM Russell AJ Smith AD Thomson JE 《Organic & biomolecular chemistry》2007,5(24):3922-3931
Chiral alpha,beta-unsaturated esters, containing a single, gamma-stereogenic centre, show modest levels of substrate control upon conjugate addition of lithium dibenzylamide. Double diastereoselective conjugate additions of homochiral lithium N-benzyl-N-(alpha-methylbenzyl)amide to the homochiral alpha,beta-unsaturated esters display "matching" and "mismatching" effects. In each case, however, these additions proceed under the dominant stereocontrol of the lithium amide to give the corresponding beta-amino esters in high de. A remarkable reversal in stereoselectivity is noted by changing the ester functionality to an oxazolidinone. Subsequent O-deprotection and cyclisation of the resultant beta-amino adducts gives access to the corresponding beta-amino-gamma-substituted-gamma-butyrolactones in good yield and high de. 相似文献
99.
100.
The Multicomponent Hantzsch Reaction: Comprehensive Mass Spectrometry Monitoring Using Charge‐Tagged Reagents
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)
Vanessa G. Santos Marla N. Godoi Thaís Regiani Fernando H. S. Gama Mirela B. Coelho Prof. Dr. Rodrigo O. M. A. de Souza Prof. Dr. Marcos N. Eberlin Prof. Dr. Simon J. Garden 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12808-12816
A novel strategy for the ESI‐MS monitoring of reaction solutions involving the alternate use of permanently charge‐tagged reagents has been used for comprehensive mass spectrometry monitoring of the multicomponent Hantzsch 1,4‐dihydropyridine reaction. By placing a charge tag on either, or both, of the two key reactants, ion suppression effects for ESI were eliminated or minimized, and comprehensive detection of charge‐tagged intermediates was achieved. The strategy allowed the trapping and characterization of the important intermediates in the mechanism for 1,4‐dihydropyridine formation. 相似文献