全文获取类型
收费全文 | 49篇 |
免费 | 4篇 |
专业分类
化学 | 34篇 |
数学 | 11篇 |
物理学 | 8篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1995年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1938年 | 2篇 |
1918年 | 1篇 |
排序方式: 共有53条查询结果,搜索用时 31 毫秒
1.
Roland Bonneau Philippe Fornier de Violet Jacques Joussot-Dubien 《Photochemistry and photobiology》1974,19(2):129-132
Abstract— The pH dependence of the apparent reactivity of thiazine dyes in their triplet states has been studied in aqueous solutions, using as electron donor HY-3 , the trianionic species of ethylene diamine tetraacetic acid (EDTA), in the pH range 4–8. The pH dependence is found to be related to a change in the degree of protonation of the triplet excited dye. The apparent reactivity and lifetime of two differently protonated forms of thionine, azur B and methylene blue were determined by classical and dye-laser flash techniques, making it possible to evaluate the rate constant for electron abstraction of these molecules in their triplet states. It is found that: (a) protonation on the ring nitrogen increases the electron-abstraction rate constant of the triplet-state species about twenty-fold, and (b) methylation on the side amino groups decreases it. 相似文献
2.
Abstract The antimalarial drugs, chloroquine, hydroxychloroquine, quinine, quinacrine, amodiaquine and primaquine and the local anaesthetic, dibucaine, were tested for in vitro photosensitizing capability by irradiation with 365 nm UV light in aqueous solutions. The ability of these compounds to photosensitize the oxidation of 2,5-dimethylfuran, histidine, tryptophan or xanthine, and to initiate the free radical polymerization of acrylamide was examined in the pH range 2-12. Chloroquine and hydroxychloroquine show maximal photooxidative behaviour when in the monocation form at pH 9, in contrast to quinine which is extremely efficient as the dication below pH 4. This pattern appears to relate to the fluorescence yield as a function of pH. Chloroquine in the monocation or neutral form was found to undergo dechlorination upon irradiation, and this correlates directly with its ability to initiate photo-polymerization of acrylamide. Quinine also gives rise to small polymerization rates, attributed to photo-ionization in the quinoline ring, yielding a cation radical. Amodiaquine, primaquine and quinacrine do not have significant photochemical activity in aqueous solution. Dibucaine exhibits a strong photosensitizing capability at low pH, similar to quinine. 相似文献
3.
The time-optimal control of a soft spring is discussed. The domain of controllability and the switching locus are described. It is shown that the switching locus changes in a discontinuous manner as the nonlinearity varies continuously.This research was partially supported by the Joint Services Electronics Program, Grant No. (4711) N00014-67-A-0226 ARPA 1129, and by NASA, Grant No. NGR 15-005-021. 相似文献
4.
Conclusions The results of our analysis strongly support our two Fe environment hypothesis. The critical concentration at about 12 at.% suggests that the dependence of H(0,x) on x undergoes a fundamental change at this concentration. Furthermore, the so-called critical concentration at about 17 at.% apparently has little to do with any fundamental alloy property. Rather, it reflects the 12 at.% critical composition when properties are analyzed in terms of the average rather than the local Fe concentration. The two Fe environments appear to have differing configurations.This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. 相似文献
5.
Inhibition of corrosion of commercial mild steel in presence of tetrazole derivatives in acid medium
V. Violet Dhayabaran I. Sharmila Lydia J. Princy Merlin P. Srirenganayaki 《Ionics》2004,10(1-2):123-125
The inhibitive influence of tetrazole derivatives namely, 1-(91-acridinyl)-5-(4′-aminophenyl) tetrazole, 1-(9′-acridinyl)-5-(4′-hydroxy phenyl) tetrazole and 1-(9′-acridinyl)-5-(4′-chlorophenyl)
tetrazole on the corrosion of commercial mild steel in 1 N hydrochloric acid medium was studied by weight loss method. The
monolayer adsorption has been confirmed by fitting the data to the Langmuir adsorption isotherm. Weight loss studies have
been carried out at 303K, 318K and 333K. Thermodynamic parameters like heat of adsorption, activation energy and free energy
change have been calculated. The maximum inhibition of efficiency of tetrazole derivatives, 1-(9′-acridinyl)-5-(4′-amoinophenyl)
tetrazole, 1-(9′acridinyl)-5-(4′-hydroxyphenyl) tetrazole and 1-(9′-acridinyl)-5-(4′-Chlorphenyl) tetrazole was found to be
60.59%, 89.00% and 92.74, respectively.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献
6.
V. Violet Dhayabaran J. Princy Merlin I. Sharmila Lydia R. Shanthi R. Sivaraj 《Ionics》2004,10(3-4):288-290
The influence of Fluorescein in conjunction with calcium oxide on the corrosion of Aluminium in 1.0 N NaOH was studied by
galvanostatic studies and weight loss studies. It has been found that the inhibition of corrosion of aluminium increased with
the increasing concentration of the inhibitor. The maximum inhibition efficiency of fluorescein alone was found to be 30.80%.
However, the addition of calcium oxide increased the maximum inhibition efficiency to 53.71%. The corrosion process was found
to be under the anodic control, in the presence or in the absence of inhibitor. The inhibition was found to be mixed type.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, Inida, Nov. 28–30, 2003. 相似文献
7.
C. E. Violet R. J. Borg Leopold May K. V. Rao J. Nogues R. D. Taylor A. P. Batra 《Hyperfine Interactions》1988,42(1-4):963-966
The magnetic properties of two amorphous Fe?Ni?Zr alloys, Fe89.7Ni0.03Zr10 and Fe70Ni20Zr10, both in the “as cast” and neutron irradiated states were investigated by Mössbauer spectroscopy and dc magnetic susceptibility measurements. The upper magnetic ordering temperatures of Fe89.7Ni0.03Zr10 are 232K and 246K for the “as cast” and irradiated samples, respectively. The magnetic ordering temperature for Fe70Ni20Zr10 was about 478K for both the “as cast” and irradiated samples. Both compositions yield magnetic hyperfine spectra, which show a considerable relaxation effect that must be explicitly considered in the calculation of the average local Fe moments. When this is done, these values derived from Mössbauer spectra are in good agreement with the dc susceptibility values. The effects of neutron irradiation on the magnetic properties of these alloys are small. 相似文献
8.
9.
Abstract Since their discovery in 1986 [11], the high temperature superconducting (HTS) copper oxides have presented a continuing challenge to both experiment and theory. The identification of the underlying mechanism (or mechanisms) responsible for their superconductivity remains an unanswered question. Numerous theories have been proposed ranging from phonon-mediated pairing of the charge carriers, similar to the Bardeen–Cooper–Schrieffer (BCS) [2] theory developed for conventional low-temperature superconductors, to novel concepts independent of phonons [3–-l0]. For conventional superconductors the variation of the transition temperature Tc , with isotopic mass M (from BCS theory Tc ~ M?a ) was an important verification of the contribution of electron-phonon interactions to electron pairing. Measurements of this effect of HTS cuprates resulted in isotope shifts much smaller than predicted by theory [ll-14], raising doubts about the role of phonons. However, Barbee [15] argued that the size of the isotope shift is not a unique indicator of phonon-mediated pairing. Since the HTS materials contain Cu ions with partially filled 3d shells, many of the alternative theories of HTS have focused on magnetic interactions and associated spin fluctuations [3–10]. The reader is referred to Ref. 16 for the details of other theories that have been proposed and to the article by Schrieffer and Anderson [17) for an overview discussion of the theory of high temperature superconductivity. 相似文献
10.