全文获取类型
收费全文 | 139篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 73篇 |
晶体学 | 7篇 |
力学 | 5篇 |
数学 | 13篇 |
物理学 | 27篇 |
无线电 | 20篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 26篇 |
2012年 | 8篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 1篇 |
2006年 | 6篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有145条查询结果,搜索用时 0 毫秒
31.
32.
M. M. Ghorab N. M. H. Taha M. A. A. Radwan N. E. Amin M. A. Shehab I. M. I. Faker 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2891-2905
This article describes the synthesis of some novel sulfone bis-compounds bearing the biologically active thioether 3–6 ; thioureido 7, 8, 15, 16; triazole 10, 11; thiosemicarbazido 9, 12, 13; and 1,3,4-thiadiazole 14, 17 moieties starting with 4,4′-diisothiocyanato-1,1-diphenylsulfone 2. The structures of newly synthesized compounds were confirmed by elemental analysis, IR, 1 H-NMR and mass spectral data. Compound 3 was found to be the most active compound against Escherichia coli. Also, compound 15 acted as potent cytotoxic agent. 相似文献
33.
In this paper, we report for the first time the nonlinear dynamics of three memristor based phase shift oscillators, and consider them as a plausible solution for the realization of parametric oscillation as an autonomous linear time variant system. Sustained oscillation is reported through oscillating resistance while time dependent poles are present. The memristor based phase shift oscillator is explored further by varying the parameters so as to present the resistance of the memristor as a time varying parameter, thus potentially eliminating the need of external periodic forces in order for it to oscillate. Multi memristors, used simultaneously with similar and different parameters, are investigated in this paper. Mathematical formulas for analyzing such oscillators are verified with simulation results and are found to be in good agreement. 相似文献
34.
This paper is a step forward to generalize the fundamentals of the conventional RC and RL circuits in fractional-order sense. The effect of fractional orders is the key factor for extra freedom, more flexibility, and novelty. The conditions for RC and RL circuits to act as pure imaginary impedances are derived, which are unrealizable in the conventional case. In addition, the sensitivity analyses of the magnitude and phase response with respect to all parameters showing the locations of these critical values are discussed. A?qualitative revision for the fractional RC and RL circuits in the frequency domain is provided. Numerical and PSpice simulations are included to validate this study 相似文献
35.
Masoome Sheikhi Shahab Siyamak Alnajjar Radwan Ahmadianarog Mahin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2019,93(12):2429-2443
Russian Journal of Physical Chemistry A - In the present work, the adsorption of the molecule cytosine on carbon nanotube [CNT] (6,6-6) was investigated for the first time using density functional... 相似文献
36.
Glaspell G Hassan HM Elzatahry A Fuoco L Radwan NR El-Shall MS 《The journal of physical chemistry. B》2006,110(43):21387-21393
Active gold and palladium nanoparticles supported on MgO nanocubes and ZnO nanobelts and transition-metal-containing MgO nanobelts were synthesized by combining evaporation and deposition-precipitation techniques. The high activity and stability of the Au/CeO2 and Pd/CeO2 nanoparticle catalysts deposited on the MgO cubes are remarkable and imply that a variety of efficient catalysts can be designed and tested using this approach. The significant increase in the concentration of corner and edge sites in MgO nanocubes make them well-defined supports to study the detailed mechanism of the catalytic activity enhancement. 相似文献
37.
38.
39.
I. Radwan Z. Pietrzak-Flis T. Wardaszko 《Journal of Radioanalytical and Nuclear Chemistry》2001,247(1):71-77
Concentrations of tritium in environmental waters (precipitation, rivers, lakes, tap water) have been determined using electrolytic enrichment and liquid scintillation counting. In waters of big rivers (the Vistula and the Odra rivers), lakes and tap water the annual average concentrations were similar to each other being from 1.4 to 1.9 Bq·dm-3. These concentrations were similar to those in the precipitation in which they ranged from 1.7 to 2.2 Bq·dm-3. The lowest tritium concentrations were found in waters of the Seashore Region rivers (average for 1994–1999 was 1.1 Bq·dm-3). The tritium concentrations in surface waters and in precipitation are still higher than that of natural level. The data obtained show that tritium concentration in the water of rivers might depend on the size of drainage area. The observed seasonal variations of tritium concentration in the precipitation collected in Warsaw and at the Mount Sniezka indicate the stratospheric source of tritium. It was found that about 30% of tritium deposited with precipitation is removed to the Baltic Sea with river waters. 相似文献
40.
Remon M. Zaki Adel M. Kamal El-Dean Shaban M. Radwan Mokhtar A. Abd ul-Malik 《中国化学会会志》2020,67(4):658-673
In the present investigation, a simple and straightforward methodology for the preparation of novel bifunctional thienopyrazolopyrazines 4a–d has been reported. Synthesis of thieno or furopyrazolopyrazines 5a , b , e , f was achieved by the reaction of o-amino-esters 4a , b , e , f with 2,5-dimethoxytetrahydrofuran. The latter pyrrolyl derivatives 5a , b , e , f were used as starting intermediates for the synthesis of new pyrimido, pyrido, and pyrazino heterocycles fused to the thieno or furopyrazolopyrazine moiety. Furthermore, alkaline hydrolysis of the o-amino-ester 4a followed by acidification afforded the corresponding o-amino carboxylic acid 15 , which was used as a versatile precursor for the synthesis of other heterocyclic compounds fused to the thienopyrazolopyrazine ring system, namely: pyrimidine, oxazine, oxazepine, and pyridine derivatives 16–23 . The chemical structures of the synthesized compounds were confirmed on the basis of elemental and spectral analyses (Fourier-transform infrared spectroscopy [FT-IR], 1H nuclear magnetic resonance [NMR], and mass spectroscopy [MS] in addition to 13C NMR for some of them). Moreover, from the biological screening, we found that most of the tested compounds exhibited promising antifungal, antibacterial, and anti-inflammatory activities compared with the corresponding reference drugs. 相似文献