首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   26篇
  完全免费   7篇
  物理学   33篇
  2019年   1篇
  2017年   3篇
  2015年   1篇
  2013年   6篇
  2011年   7篇
  2010年   1篇
  2009年   5篇
  2008年   2篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2002年   2篇
排序方式: 共有33条查询结果,搜索用时 31 毫秒
1.
两种芳香植物非挥发性组分抗氧化和对DNA损伤的保护作用   总被引:5,自引:1,他引:4  
采用6种化学发光体系和两种比色体系研究了芳香植物罗勒和香柠檬的非挥发性组分(简称罗勒、香柠檬)直接清除活性氧、活性氮和对^.OH引起的DNA损伤的保护作用。结果表明,罗勒和香柠檬不仅能直接清除O2,而且可抑制黄嘌呤氧化酶的活性从而减少O2的产生。罗勒和香柠檬也能有效清除^.OH、H2O2、ONOO^.和DPPH^.,两者相比,香柠檬除对^.OH的清除作用弱于罗勒外,清除以上各种自由基的能力均强于罗勒。结果还显示,罗勒和香柠檬都能抑制脂质过氧化,明显地抑制和延缓DNA损伤,起到预防型抗氧化剂和断链型抗氧化剂的双重作用。这些结果表明,罗勒和香柠檬的非挥发性组分是有效的、多功能的天然抗氧化剂和自由基清除剂。  相似文献
2.
雷震子护康胶囊制剂抗氧化和对DNA损伤保护作用研究   总被引:3,自引:0,他引:3  
雷震子护康胶囊以低聚原花青素、灵芝多糖、绞股蓝总皂甙及一定量的维生素C等为主要成分而制成,有多种保健功能。为研究该复方制剂的抗氧化作用,采用七种化学发光体系和一种比色体系研究了雷震子直接清除活性氧、活性氮和对^.OH引起的DNA损伤的保护作用。结果表明雷震子能有效清除O2^-.、^.OH、H2O2、ONOO^-和全血嗜中性白细胞“呼吸爆发”产生的活性氧,抑制脂质过氧化,保护DNA免受^.OH的氧化损伤。这些结果提示,雷震子是一种有效的抗氧化复方制剂,其强烈的抗氧化活性可能是其保健功能的重要药理基础之一。  相似文献
3.
利用共沉淀法制备了几种稀土金属氧化物改性的氧化镍催化剂 ,考察了其乙烷氧化脱氢 (ODE)制乙烯的催化性能 ,讨论了不同稀土金属氧化物掺杂浓度对催化剂催化性能的影响 ,利用Raman光谱技术初步表征反应在该类催化剂上的活性氧物种为Raman谱带出现在 1 0 60cm- 1 的表面双原子超氧物种O-2 ,该谱峰的大小与催化剂的ODE性能有很好的对应关系。  相似文献
4.
Ni3V2O8催化性能与X射线光电子能谱分析   总被引:1,自引:0,他引:1  
文章采用微波加热,草酸盐共沉淀法制备了Ni3V2O8催化剂,并对催化剂进行了BET,XRD,H2-TPR,XPS,TEM和电导等技术表征,分析研究了Ni3V2O8催化剂的丙烷氧化脱氢(ODH)制丙烯催化性能与其表面物种的关系.XRD,TEM和电导实验结果表明本方法制得的Ni3V2O8催化剂晶粒均匀,平均粒径为30 nm,具有p-型半导体性质.TPR和XPS实验结果显示Ni3V2O8催化剂中,晶格氧可以较容易转换成未完全还原氧,使催化剂内各种价态的钒之间易于进行氧化还原反应并形成氧缺位,从而催化剂的表面含有较多未充分还原氧物种O-和V4 物种.催化活性结果显示当丙烷的转化率为18.60%,丙烯选择性达到60.02%,在相同转化率条件下,比文献报道的NiO和Ni3V2O8共存催化体系中的丙烯选择性高,说明Ni3V2O8催化剂中存在未充分还原的O-和V4 物种有利于提高丙烯的选择性.  相似文献
5.
列举了一些具有代表性的研究结果,概括介绍了一些产生旁观者效应的可能机制以及辐照引起的活性氧基团或分子、细胞通讯和细胞因子在旁观者效应中的重要作用.此外,还讨论了旁观者效应的表达程度与辐照剂量和射线品质的关系.旁观者效应的研究结果表明:辐射产生的潜在危害可能要比以前估计的大,这给如何评估辐射对人类造成的危害带来了新的冲击.  相似文献
6.
In this review, we have focused on the oxidation reactions of single dye molecules by reactive oxygen species (ROS). The methodologies for the single-molecule detection of ROS, such as hydroxyl radical (HO), singlet oxygen (O2(a1Δg)), and hydrogen peroxide (H2O2), have been introduced together with examples. In particular, a successful application using the single-molecule fluorescence technique for the investigation of the TiO2 photocatalytic oxidation reactions is demonstrated in detail.  相似文献
7.
Treatment of chlorella green algae (Chlorella sp.) for 2 h in the dark with the photodynamic herbicide glutaphen (GTP), consisting of 0.3 mM 1,10-phenanthroline and 0.6 mM glutamic acid, followed by illumination leads to efficient generation of active oxygen species (AOS). After 15 min of illumination, AOS accumulation reaches 200% compared with the level in cells of the control culture, then it decreases down to 130% and 115% after 1 day and 3 days of illumination. During the first few days after treatment, we observe inhibition of synthesis of a specific precursor of chlorophyll (Chl): 5-aminolevulinic acid molecules, and then we observe stimulation of the synthesis. The effect of GTP on the photosynthetic activity of chlorella does not depend on the AOS level but rather remains uniform, in contrast to its effect on the Chl biosynthesis system. GTP does not change the efficiency of light harvesting and charge separation at the reaction centers of photosystem (PS) 2, but significantly lowers the functional efficiency of the electron transport chain: the photochemical quenching constants for Chl a fluorescence and the effective quantum yield of photochemical reactions in photosystem 2 decrease. The major mechanism of action for GTP is probably displacement of the secondary quinone acceptor QB from its binding site on the D1 protein by the 1,10-phenanthroline, consequent inhibition of electron efflux from Q A and increase in the fraction of QB-nonreducing centers of PS 2. The active oxygen species generated in the cells have a photodegradative effect on the Chl biosynthesis system, in particular on its initial steps, and do not involve already formed pigment-protein complexes of PS 2. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 801–806, November–December, 2006.  相似文献
8.
Plasma medicine is an innovative and emerging field combining plasma physics, life science and clinical medicine. In a more general perspective, medical application of physical plasma can be subdivided into two principal approaches. (i) “Indirect” use of plasma-based or plasma-supplemented techniques to treat surfaces, materials or devices to realize specific qualities for subsequent special medical applications, and (ii) application of physical plasma on or in the human (or animal) body to realize therapeutic effects based on direct interaction of plasma with living tissue. The field of plasma applications for the treatment of medical materials or devices is intensively researched and partially well established for several years. However, plasma medicine in the sense of its actual definition as a new field of research focuses on the use of plasma technology in the treatment of living cells, tissues, and organs. Therefore, the aim of the new research field of plasma medicine is the exploitation of a much more differentiated interaction of specific plasma components with specific structural as well as functional elements or functionalities of living cells. This interaction can possibly lead either to stimulation or inhibition of cellular function and be finally used for therapeutic purposes. During recent years a broad spectrum of different plasma sources with various names dedicated for biomedical applications has been reported. So far, research activities were mainly focused on barrier discharges and plasma jets working at atmospheric pressure.  相似文献
9.
Superparamagnetic iron oxide nanoparticles (SPIONs) are one of the most versatile and safe nanoparticles in a wide variety of biomedical applications. In the past decades, considerable efforts have been made to investigate the potential adverse biological effects and safety issues associated with SPIONs, which is essential for the development of next-generation SPIONs and for continued progress in translational research. In this mini review, we summarize recent developments in toxicity studies on SPIONs, focusing on the relationship between the physicochemical properties of SPIONs and their induced toxic biological responses for a better toxicological understanding of SPIONs.  相似文献
10.
The sonodynamic damage of bovine serum albumin (BSA) under ultrasonic irradiation in the presence of amsacrine (AMSA) was studied by hyperchromic effect of UV-vis spectra and quenching effect of intrinsic fluorescence. In addition, several influencing factors such as ultrasonic irradiation time, AMSA concentration, system acidity and ionic strength about the damage of BSA molecules were reviewed. The results showed that the damage degree was obviously enhanced with the increase of ultrasonic irradiation time and AMSA concentration, but it was only slightly increased with the increase of solution pH value and ionic strength. Furthermore, the binding and damaging sites to BSA molecules were estimated by synchronous fluorescence spectra. The different chances to damage tryptophan (Trp) and tyrosine (Tyr) residues were found through the ratios of synchronous fluorescence quenching (RSFQ). At last, the generation of reactive oxygen species (ROS) in sonodynamic process was estimated by the method of oxidation-extraction Spectrometry (OES). And then, several radical scavengers were used to determine the kind of ROS, which includes singlet oxygen (1O2) and hydroxyl radicals (·OH). Perhaps, the result would bring a certain guiding significance to use sonosensitive drugs in the fields of tumor treatment.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号