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   394篇
  免费   138篇
  国内免费   3篇
电工技术   2篇
综合类   5篇
化学工业   400篇
金属工艺   1篇
机械仪表   1篇
建筑科学   9篇
能源动力   2篇
轻工业   5篇
石油天然气   1篇
无线电   42篇
一般工业技术   58篇
冶金工业   2篇
原子能技术   6篇
自动化技术   1篇
  2024年   1篇
  2023年   6篇
  2022年   11篇
  2021年   37篇
  2020年   30篇
  2019年   20篇
  2018年   27篇
  2017年   28篇
  2016年   27篇
  2015年   24篇
  2014年   40篇
  2013年   50篇
  2012年   21篇
  2011年   22篇
  2010年   19篇
  2009年   33篇
  2008年   20篇
  2007年   21篇
  2006年   17篇
  2005年   15篇
  2004年   15篇
  2003年   8篇
  2002年   7篇
  2001年   6篇
  2000年   2篇
  1999年   3篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   5篇
  1994年   3篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
  1951年   1篇
排序方式: 共有535条查询结果,搜索用时 15 毫秒
121.
BACKGROUND: Low‐pressure batch and continuous‐flow microwave photoreactors were equipped with microwave powered quartz mercury electrodeless discharge lamps (Hg‐EDLs). Photohydrolysis of aqueous mono‐chloroacetic acid (MCAA) into hydroxyacetic acid and HCl was chosen as the model reaction to evaluate these photoreactors. The effects of operational parameters on the MCAA photolysis through a UV/MW process were investigated. RESULTS: Studies were carried out at relatively high MCAA concentration (0.1 mol L?1). The photoreaction course was monitored by the pH change in the solution. The MCAA conversion was optimized as a result of a trade‐off between the thermal dependence of the photochemical quantum yield (which increases with increasing temperature) and the thermal dependence of the EDL light intensity of 254 nm line (which increases with decreasing temperature). The microwave photoreactors made it possible to study the temperature dependence of MCAA photohydrolysis. CONCLUSION: It was found that operational parameters (i.e. reaction temperature, quantum yield) had important effects on photoefficiency. Photohydrolysis of MCAA in the microwave photoreactors can be enhanced by the UV/MW system. The results of conversions (in 120 min) for the particular photoreactor set‐ups show that the best reaction conditions for MCAA photolysis were obtained in the low‐pressure batch microwave photoreactor (the conversion was 46% at 80 °C). Copyright © 2009 Society of Chemical Industry  相似文献   
122.
123.
抗生素的滥用所导致的细菌耐药性增强以及抗性基因污染问题,对人类健康和生态安全造成了极大的威胁,如何高效地去除水中抗生素抗性菌(简称ARB)和和抗生素抗性基因(简称ARGs)成为当前研究重点.光化学高级氧化技术(简称AOPs)可以利用光辐照产生具有强氧化性的活性氧物种来氧化分解水中难降解有机污染物,对于水中抗性菌和抗性基因的去除具有广阔的应用前景.该文首先介绍了抗生素抗性基因传播扩散机制及污染现状,其次对光化学AOPs应用于去除水中抗生素ARB和ARGs的研究进展进行归纳,并分析了影响去除效果的因素及其应用的局限性,最后指出未来应加强对于光化学AOPs灭活的氧化损伤机制以及与规模化实际工程应用相结合的研究.  相似文献   
124.
以污染物作为电子给体进行的光催化制氢体系代表着一种新型的现代水处理技术,在污染物被降解的同时还可以将太阳能转化为清洁的氢能,有效地缓解了环境污染和能源短缺两大难题。为此,本文结合光催化制氢协同污染物降解反应的机理,概述了近年来国内外在该方向上的主要研究成果,列举了几种常用的催化剂,分析了不同的操作参数,如污染物种类、催化剂类型和组分、催化剂的微观结构、催化剂投加量、pH、污染物浓度、溶液中存在的不同阴阳离子及其他共存物、反应温度以及光照强度对光催化降解率和产氢活性的影响。最后,指出了以污染物作为电子给体的光催化水处理技术在光催化材料的选择上依然面临种类偏少、产氢效率偏低的挑战,并且在反应影响因素的探究上仍存在不充分、不全面的问题。同时,评述了将多项工艺结合起来的多单元水处理系统是未来水处理领域的一个主流模式。  相似文献   
125.
光催化分解水制氢是获取氢能的理想方式,开发高效的光催化剂成为本领域研究的热点。碳点因为具有独特的上转换性能、可见光响应以及带隙可调的性质且水溶性好、无生物毒性、光致发光性能优异,在光催化产氢领域的应用引起了极大关注。目前合成碳点的方法主要包括自上而下和自下而上两种方式。通过表面钝化、表面功能化或元素掺杂等改性手段可以进一步增强碳点的光电性能和抗腐蚀性能。本文从碳点主要的制备和改性手段出发,概述了近年来碳点用于光催化分解水制氢领域主要的研究成果,总结了碳点分别作为光催化剂主体、助催化剂、光敏剂以及Z型结构的电子转移介质在光催化制氢中的应用。同时指出目前碳点在光催化制氢领域还普遍存在着机理不明晰、产氢效率偏低的问题,未来该领域的研究方向将侧重于大规模合成结构更精确、目标特定性更强的碳点以及探究碳点在光催化产氢过程中的优化机制。  相似文献   
126.
Nowadays water scarcity represents a threat for human and living beings. Therefore, to satisfy the demands of people for clean and safe water, new technologies for wastewater treatment have been developed. Thus, photocatalysis has emerged as a green chemical approach for such treatment. In this context, new polyoxometalate (POM)/polymer composites with relevant photocatalytic properties have been developed via an easy and cheap photopolymerization process upon mild visible light irradiation at 405 nm. This fruitful association between POM and polymer allowed the obtention of shaped materials facile to collect and reuse at the end of the photocatalytic treatment avoiding then the usual time-consuming regeneration methods. The prepared photocomposites displayed excellent photocatalytic performance for the removal of bisphenol-A from water under different sources of irradiation. Hence, 100%, 88%, and 50% of this model compound were decomposed by the phosphomolybdic composite under just 90 min of UV lamp, solar and LED@375 nm irradiations, respectively. The effectiveness of these developed photocatalysts towards the degradation of other organic compounds, as well as the degradation mechanism based on the generation of highly reactive chemicals such as OH radicals promoting the degradation were already reported. Bisphenol-A degradation pathway and the identification of the photoproducts were discussed using mass spectroscopy technique. Therefore, this paper highlighted the photocatalytic efficiency of the new manufactured materials for the photodegradation of the bisphenol-A, thus expanding their application fields, under different sources of irradiation and under pure solar irradiation which make their applications more interesting and less energy consuming.  相似文献   
127.
The inclusion of the metal free semiconductor graphitic carbon nitride (g-CN) into polymer systems brings a variety of new options, for instance as a heterogeneous photoredox polymer initiator. In this context, we present here the decoration of the inner surface of poly(styrene-co-divinylbenzene) beads with organomodified g-CN via one pot suspension photopolymerization. The resulting beads are varied by changing reaction parameters, such as, crosslinking ratio, presence of porogens, and mechanical agitation. The photocatalytic activity of so-formed beads was tested by aqueous rhodamine B dye photodegradation experiments. Additionally, dye adsorption/desorption properties were examined in aqueous as well as in organic solvents. Photoinduced surface modification with vinylsulfonic acid and 4-vinyl pyridine is introduced. Overall, metal-free semiconductor g-CN donates photoactivity to polymer networks that can be employed for dye photodegradation and acid–base catalyst transformation through facile photoinduced surface modifications.  相似文献   
128.
Two donor units (D)-acceptor units (A) type monomers were synthesized by Stille coupling reaction, and then three D-A type hybrid polymers based on 3,4-ethylenedioxythiophene and various benzodiazoles were synthesized by electrochemical polymerization. Spectroelectrochemical and kinetic studies of these polymers showed that all polymer films exhibited excellent electrochromic behavior, obvious optical contrast, and excellent stability. Among them, the response time of P3 film was the shortest (tc = 1.6 s, tb = 2.2 s), the coloring efficiency of P2 film was the highest (CE = 333 cm2·C−1), and the stability of P1 was the best (the ΔT loss of P1 after 1000 s cycles is only 2.3%). Therefore, these data prove that these new polymers have great potential in applications as electrochromic materials.  相似文献   
129.
溶解有机质矿化为溶解无机碳是全球碳循环中的一个重要过程.利用模拟太阳光对Suwannee河腐植酸的光氧化过程模拟,研究了溶解氧浓度、模拟太阳光波长范围和铁浓度对溶解无机碳产量的影响.研究表明,基于前24 h空气饱和的无机碳矿化速率4.40μmol/(L.h),氧气饱和条件下照射增加1.56倍,氮气饱和条件下照射下降36%.UV-B,UV-A和可见光部分分别占溶解无机碳产量的31.8%、32.6%和25.6%.当加入20μmol/L铁络合剂DFOM时(初始样品Suwannee河腐植酸铁含量为5.46μmol/L),溶解无机碳产量下降55.6%.  相似文献   
130.
Singlet molecular oxygen is a reactive oxygen species that plays an important role in a number of biological processes, both as a signalling agent and as an intermediate involved in oxidative degradation reactions. Singlet oxygen is commonly generated by the so-called photosensitization process wherein a light-absorbing molecule, the sensitizer, transfers its energy of excitation to ground-state oxygen to make singlet oxygen. This process forms the basis of photodynamic therapy, for example, where light, a sensitizer, and oxygen are used to initiate cell death and ultimately destroy undesired tissue. Although the photosensitized production of singlet oxygen has been studied and used in biologically pertinent systems for years, the photoinitiated behaviour is often indiscriminate and difficult to control. In this Concept, we discuss new ideas and results in which spatial and temporal control of photosensitized singlet oxygen production can be implemented through the incorporation of the sensitizer into a conjugate system that selectively responds to certain triggers or stimuli.  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