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   784篇
  免费   8篇
  国内免费   10篇
综合类   25篇
化学工业   334篇
金属工艺   13篇
机械仪表   10篇
建筑科学   12篇
矿业工程   1篇
能源动力   100篇
轻工业   91篇
水利工程   3篇
石油天然气   13篇
武器工业   1篇
无线电   64篇
一般工业技术   123篇
冶金工业   3篇
原子能技术   3篇
自动化技术   6篇
  2023年   11篇
  2022年   26篇
  2021年   20篇
  2020年   15篇
  2019年   21篇
  2018年   18篇
  2017年   27篇
  2016年   25篇
  2015年   15篇
  2014年   33篇
  2013年   58篇
  2012年   38篇
  2011年   44篇
  2010年   45篇
  2009年   60篇
  2008年   34篇
  2007年   29篇
  2006年   32篇
  2005年   23篇
  2004年   29篇
  2003年   18篇
  2002年   28篇
  2001年   27篇
  2000年   24篇
  1999年   24篇
  1998年   16篇
  1997年   8篇
  1996年   6篇
  1995年   12篇
  1994年   7篇
  1993年   5篇
  1992年   6篇
  1991年   4篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1987年   4篇
  1985年   1篇
  1984年   1篇
排序方式: 共有802条查询结果,搜索用时 15 毫秒
81.
以邻氯硝基苯为原料,经氯磺化、氨解、水解酸化三步反应制备了2-硝基苯酚-4-磺酰胺.研究了各步反应的影响因素,在传统工艺的基础上优化了反应条件,最优反应条件是n(邻氯硝基苯)∶n(氯磺酸)=1∶4,分次投料,并加入一定量的无水硫酸钠,反应温度为140℃,反应时间为6~7h;将所得产品按n(2-硝基氯苯-4-磺酰氯)∶n(氨水)=1∶1.5加入氨水中,反应温度为38~40℃,低温反应2h;最后于30%氢氧化钠溶液中水解,反应温度100~105℃,反应时间为3~4h,并加入相转移催化剂,最后进行酸化,抽滤后得目标产品.总收率由50%提高为70%,并对三步所得产品进行了红外光谱分析.  相似文献   
82.
采用酰化法成功地合成了几种染料单体:2—羟基—4—丙烯酰氧二苯酮(HAOBP),1—羟基—2—丙烯酰氧蔥(西昆)(HAOAQ)和1,5,8—三羟基—2—丙烯酰氧蔥(西昆)(THAOAQ),并用元素分析法、红外光谱法和高分辨H~1NMR 谱对其结构进行了详细研究和表征。  相似文献   
83.
本文论述了着色型珠光颜料涂布纸的研制工作,并对影响珠光涂料制备的几个因素进行探讨.优化结果表明,瓷土0~30%,珠光颜料70%~100%,胶粘剂25%~30%,固含量23%~25%,涂布量10~15g/m2时,其纸面呈现强烈的珠光光泽,适用于胶印.  相似文献   
84.
张蕊萍 《合成纤维》2003,32(3):32-34
根据多年的科研和生产实践,详细讨论了影响汽车内饰用ATY质量的主要因素,并提出相应的改进技术和管理措施。  相似文献   
85.
MnO2 nanorods were synthesized by mechanochemical processing with subsequent heat treatment and their photocatalytic activity was studied on the decolourization of aqueous solution of Rhodamine B at different pH levels. A solid state redox reaction 2KMnO4 + MnCl2 → 3MnO2 + 2KCl + O2 was activated during mechanical milling. Excess KCl salt was added in the starting powder mixture to prevent agglomeration of MnO2 nanoparticles. The milling resulted in the production of amorphous MnO2 nanoparticles with a high surface area of 204 m2 g?1. Crystalline MnO2 nanorods of diameters about 15–20 nm were produced by heating the as-milled powder at 350 °C for 1 h in air. Amorphous MnO2 nanoparticles showed higher degradation rate of Rhodamine B than crystalline MnO2 nanorods under simulated sunlight. The degradation rate was higher under acidic conditions. This work demonstrates the potential for cost effective, green and scalable synthesis of MnO2 nano-catalysts for environmental applications.  相似文献   
86.
CuO/[Si]MCM‐41 catalysts with various Si/Cu molar ratios were prepared and characterized by X‐ray diffraction, nitrogen physisorption, temperature‐programmed reduction by H2, and UV‐vis and Raman spectroscopy. The effects of copper loading and pH on their activity in the decolorization of methyl orange were studied in a heterogeneous Fenton‐like process. With decreasing Si/Cu ratio, dye decolorization increased from 18 to 75 % at pH 3. CuO/[Si]MCM‐41 catalysts showed 75, 50, and 40 % conversion of methyl orange at pH 3, 5, and 7, respectively. This is a significant improvement to Fenton‐like reactions involving copper, and thus CuO/[Si]MCM‐41 catalysts are quite promising for pollutant degradation.  相似文献   
87.
镍络硫代双烯型红外激光染料的研究   总被引:3,自引:0,他引:3  
高昕  程铸生 《上海化工》1997,22(4):18-21
合成了三种结构为(RCSSCR)2Ni的镍张硫代双烯型经外激光染料,三种染料的最大吸收光波长为1020nm-1495nm。作者观察了它们在重原子溶剂间碘苯胺听最大向红位移,并研究了这类染料的优越光稳定性能。  相似文献   
88.
ZnO–SnO2 nanocubes were used as promising material for efficient sensing of p-nitrophenol and faster photocatalytic degradations of dyes like methyl orange (MO), methylene Blue (MB) and acid orange 74 (AO74). ZnO–SnO2 nanocubes were prepared by the facile solution process at 50 °C using Zn(NO3)2·6H2O and SnCl2·2H2O as a precursor in the presence of ethylenediammine. The synthesized material was examined for its morphological, structural, crystalline, optical, vibrational, and compositional studies by using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. FESEM studies revealed the formation of well-defined ZnO–SnO2 nanocubes where the structural examinations revealed the formation of a crystalline tetragonal rutile phase for SnO2 with some crystal sites doped with Zn. The as-synthesized nanocubes were explored for their photocatalytic activities towards three different dye viz. MO, MB, and AO74. Practically, complete degradation of AO74 was seen within 4 minutes of photo-irradiation in the presence of 0.05 g ZnO–SnO2 nanocubes. However, 97.17% and 41.63% degradations were observed for MB and MO within 15 and 60 minutes, respectively. All the dye degradation processes followed the pseudo-first-order kinetic model. Moreover, the as-synthesized nanocubes were utilized to fabricate highly sensitive and selective fluorescent chemical sensor for the detection of p-nitrophenol (PNP). ZnO–SnO2 nanocubes showed a very low detection limit of 4.09 μM for the detection of PNP as calculated according to the 3σ IUPAC criteria. Further, the as-synthesized ZnO–SnO2 nanotubes were found to be highly selective for p-nitrophenol as compared to the other two isomers.  相似文献   
89.
《Ceramics International》2016,42(11):13151-13160
In this work, we employed an impurity-free nanoparticle synthesis technique, known as pulsed laser ablation in liquid (PLAL), to integrate titanium dioxide nanoparticles (TiO2 NPs) into zinc oxide nanorods (ZnO NRs) with varying relative proportions. The main objective of this integration was to enhance the charge carrier separation of photo-generated electron hole pairs during solar irradiation. For the synthesis process, an Nd:YAG laser at 532 nm wavelength was applied as an ablation source, along with deionized water as a solvent medium in which the precursor materials were dispersed prior to laser irradiation. The nanocomposites were characterized by X-ray diffraction (XRD), UV–vis absorption and in-situ Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM). The synthesized nanocomposites were primarily utilised in two applications: firstly, as a catalyst in the degradation of methyl orange (MO) and secondly, as photo-anode in dye sensitized solar cell (DSSC). Our research has demonstrated that optimal performance was obtained for the nanocomposite containing 10% and 90% (by weight) TiO2 NPs and ZnO respectively, which we define as the ideal nanocomposite. Relative to pure ZnO, the photo-conversion efficiency of the ideal composite was improved substantially by 63.73%, whilst the photo-degradation rate was enhanced by 3 fold. The oxidation state and the microstructural of the segregated ideal nanocomposite confirms that oxygen vacancy defects were created when perfect surface integration occurs between TiO2 and ZnO. Nonetheless, we believe that the performance enhancement is predominantly due to the excellent charge carrier separation and fast interfacial electron flow in this nanocomposite.  相似文献   
90.
《Ceramics International》2015,41(4):5670-5676
Fixation of photocatalyst in glass matrix would solve the problem of photocatalyst recovery. In this study, the system 30 Bi2O3, 20 B2O3 and 50 (MoO3 or V2O5), was used for the preparation and stabilization of the photoactive phases of both bismuth molybdate β-Bi2Mo2O9 and monoclinic–scheelite BiVO4 in a glassy matrix. Proper heat-treatment schedule, based on differential thermal analysis (DTA) results, has been applied to improve the crystallinity of the prepared glass–ceramics. The applied heat-treatment program showed a significant effect on the size of the formed crystals, especially in samples with molybdenum content. For instance, one-step heat-treatment (500°C/2 h) improves the crystallinity of the material than two-step heat-treatment (355°C/1 h+400°C/2 h). It was also noticed that the amount of glassy matrix relative to crystalline part in case of vanadium-contained samples is much more than that in the corresponding molybdenum-contained samples. The prepared samples were used for the degradation of Red SPD Cotton dye in order to assess their photocatalytic activity. All molybdenum contained samples showed a promising photocatalytic activity. On contrary, vanadium-contained samples were inactive suggesting that most of photoactive crystals are in the bulk of materials.  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