全文获取类型
收费全文 | 62篇 |
免费 | 0篇 |
专业分类
化学 | 23篇 |
力学 | 1篇 |
数学 | 4篇 |
物理学 | 34篇 |
出版年
2019年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有62条查询结果,搜索用时 125 毫秒
1.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
2.
Alberti G Brunet E Dionigi C Juanes O de La Mata MJ Rodríguez-Ubis JC Vivani R 《Angewandte Chemie (International ed. in English)》1999,38(22):3351-3353
The hydrophilic oxygen atoms of polyethylenoxide chains inserted as pillars in gamma-zirconium phosphate form hydrogen bonds with the acid groups of the host. As a result the pillars are almost perpendicular to the gamma layers. Upon changing the pH level of the supernatant solution the hydrogen bonds are broken and the pillars become almost perpendicular to the layers (shown schematically). Thus there is a reversible enlargement-shortening of the interlayer space. 相似文献
3.
Streeter I Wain AJ Thompson M Compton RG 《The journal of physical chemistry. B》2005,109(25):12636-12649
An in situ electrochemical electron spin resonance (ESR) study on the electro-oxidation of para-chloroaniline, para-bromoaniline, and para-iodoaniline dissolved in acetonitrile at gold electrodes is reported. ESR spectra obtained using a tubular flow cell reveal the presence of a paramagnetic dimer product derived from para-aminodiphenylamine, during oxidative electrolysis, suggesting the coupling of reactive electrogenerated radical cations with neutral parent haloaniline molecules. The ESR signal intensity behaves in a manner expected for a radical species reacting with second-order kinetics, suggesting the paramagnetic dimer is, itself, unstable. The theory describing the ESR signal intensity flow rate behavior for this reaction mechanism is developed for the tubular arrangement and used to extract mechanistic and kinetic data from the experimental results for the cases of para-chloroaniline and para-bromoaniline. Further mechanistic aspects, including proton and halide ion expulsion during dimerization, are explored voltammetrically and with the aid of digital simulations using Digisim. Comparison of the ESR signal and voltammetric measurements suggests that an additional mechanism operates which does not lead to paramagnetic products. Additionally, the in situ electrolysis of N,N-dimethyl-para-bromoaniline is reported to generate the stable radical cation of N,N,N',N'-tetramethylbenzidine, and a mechanism of electro-oxidation is, thus, proposed. 相似文献
4.
Streeter TC Bol R Bardgett RD 《Rapid communications in mass spectrometry : RCM》2000,14(15):1351-1355
It is becoming increasingly apparent that soil amino acids are a principal source of nitrogen (N) for certain plants, and especially those of N-limited environments. This study of temperate upland grasslands used glycine-2-(13)C-(15)N and ((15)NH4)(2)SO(4) labelling techniques to test the hypothesis that plant species which dominate 'unimproved' semi-natural grasslands (Festuca-Agrostis-Galium) are able to utilise amino acid N for growth, whereas those plants which dominate 'improved' grasslands (Lolium-Cynosurus), that receive regular applications of inorganic fertiliser, use inorganic N forms as their main N source. Data from field experiments confirmed that 'free' amino acids were more abundant in 'unimproved' than 'improved' grassland and that glycine was the dominant amino acid type (up to 42% of total). Secondly, the injection of representative amounts of glycine-2-(13)C-(15)N (4.76 and 42.86 mM) into intact soil cores from the two grassland types provided evidence of direct uptake of glycine by plants, with both (15)N and (13)C being detected in plant material of both grasslands. Finally, a microcosm experiment demonstrated no preferential uptake of amino acid N by the grasses which dominate the grassland types, namely Holcus lanatus, Festuca rubra, Agrostis capillaris from the 'unimproved' grassland, and Lolium perenne from the 'improved' grassland. Again, both (13)C and (15)N were detected in all grass species suggesting uptake of intact glycine by these plants. 相似文献
5.
6.
7.
Roland K. Robins Ganapathi R. Revankar Darrell E. O'Brien Robert H. Springer Thomas Novinson Anthony Albert Keitaro Senga Jon P. Miller David G. Streeter 《Journal of heterocyclic chemistry》1985,22(3):601-634
A number of new hypoxanthine analogs have been prepared as substrate inhibitors of xanthine oxidase. Most noteworthy inhibitory new hypoxanthine analogs are 3-(m-tolyl)pyrazolo[1,5-a]pyrimidin-7-one ( 47 ), ID50 0.06 μM and 3-phenylpyrazolo[1,5-a]pyrimidin-7-one ( 46 ), ID50 0.40 μM. 5-(p-Chlorophenyl)pyrazolo[1,5-a]pyrimidin-7-one ( 63 ) and the corresponding 5-nitrophenyl derivative 64 exhibited an ID50 of 0.21 and 0.23 μM, respectively. 7-Phenylpyrazolo[1,5-a]-s-triazin-4-one ( 40 ) is shown to exhibit an ID50 of 0.047 μM. The structure-activity relationships of these new phenyl substituted hypoxanthine analogs are discussed and compared with the xanthine analogs 3-m-tolyl- and 3-phenyl-7-hydroxypyrazolo[1,5-a]pyrimidin-5-ones ( 90 ) and ( 91 ), previously reported from our laboratory to have ID50 of 0.025 and 0.038 μM, respectively. The presence of the phenyl and substitutedphenyl groups contribute directly to the substrate binding of these potent inhibitors. This work presents an updated study of structure-activity relationships and binding to xanthine oxidase. In view of the recent elucidation of the pterin cofactor and the proposed binding of this factor to the molybdenum ion in xanthine oxidase, a detailed mechanism of xanthine oxidase oxidation of hypoxanthine and xanthine is proposed. Three types of substrate binding are viewed for xanthine oxidase. The binding of xanthine to xanthine oxidase is termed Type I binding. The binding of hypoxanthine is termed Type II binding and the specific binding of alloxanthine is assigned as Type III binding. These three types of substrate binding are analyzed relative to the most potent compounds known to inhibit xanthine oxidase and these inhibitors have been classified as to the type of inhibitor binding most likely to be associated with specific enzyme inhibition. The structural requirements for each type of binding can be clearly seen to correlate with the inhibitory activity observed. The chemical syntheses of the new 3-phenyl- and 3-substituted phenylpyrazolo[1,5-a]pyrimidines with various substituents are reported. The syntheses of various 8-phenyl-2-substituted pyrazolo-[1,5-a]-s-triazines, certain s-triazolo[1,5-a]-s-triazines and s-triazolo[1,5-a]pyrimidine derivatives prepared in connection with the present study are also described. 相似文献
8.
Ohne Zusammenfassung 相似文献
9.
Vincent KA Tilley GJ Quammie NC Streeter I Burgess BK Cheesman MR Armstrong FA 《Chemical communications (Cambridge, England)》2003,(20):2590-2591
Addition of an equivalent of a polyaminocarboxylate ligand (L) to a solution of a redox protein and the aqua Eu2+ ion results in the instantaneous in situ generation of a very powerful reductant Eu(II)-L that can rapidly drive an electron stoichiometrically onto a redox centre having an extremely negative reduction potential (lower than -1 V): this is exemplified by straightforward generation of the super-reduced state of the Fe-protein of nitrogenase. 相似文献
10.