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   2071篇
  免费   261篇
  国内免费   117篇
电工技术   170篇
综合类   135篇
化学工业   674篇
金属工艺   52篇
机械仪表   129篇
建筑科学   135篇
矿业工程   108篇
能源动力   67篇
轻工业   248篇
水利工程   32篇
石油天然气   193篇
武器工业   2篇
无线电   129篇
一般工业技术   141篇
冶金工业   163篇
原子能技术   38篇
自动化技术   33篇
  2024年   4篇
  2023年   23篇
  2022年   54篇
  2021年   86篇
  2020年   94篇
  2019年   77篇
  2018年   66篇
  2017年   87篇
  2016年   63篇
  2015年   94篇
  2014年   137篇
  2013年   195篇
  2012年   179篇
  2011年   154篇
  2010年   117篇
  2009年   122篇
  2008年   86篇
  2007年   115篇
  2006年   115篇
  2005年   69篇
  2004年   63篇
  2003年   47篇
  2002年   64篇
  2001年   47篇
  2000年   36篇
  1999年   37篇
  1998年   26篇
  1997年   28篇
  1996年   14篇
  1995年   24篇
  1994年   18篇
  1993年   12篇
  1992年   10篇
  1991年   14篇
  1990年   10篇
  1989年   7篇
  1988年   6篇
  1987年   7篇
  1986年   8篇
  1985年   8篇
  1984年   11篇
  1983年   4篇
  1982年   3篇
  1981年   3篇
  1980年   1篇
  1976年   1篇
  1974年   1篇
  1961年   1篇
  1956年   1篇
排序方式: 共有2449条查询结果,搜索用时 265 毫秒
41.
田贺忠 《国际电力》2005,9(6):56-57,67
向烟气中喷入像粉末状活性炭之类的吸收剂,是一种最简单和最成熟的控制燃煤锅炉汞排放的方法。在4个不同的燃烟煤和次烟煤的,tY开展的第一次吸收剂喷射实验计划,证明了活性炭喷射(ACI)在控制汞排放方面的有效性。由于具有以下优点,ACI技术尤其适合现有燃煤锅炉的汞排放控制:(1)投资成本低(〈5美元/kW);(2)改造容易且耗时短,几乎无需机组停运;(5)不论烟煤还是次烟煤均适用;(4)当使用布袋除尘器时在较低的吸收剂喷射速率下就可达到90%以上的汞去除效率。  相似文献   
42.
利用湿式静电除尘器(ESP)脱除汞   总被引:2,自引:0,他引:2  
田贺忠 《国际电力》2005,9(6):62-64
燃烧高硫煤或低硫煤电厂应认真考虑的一种汞排放控制方式是采用湿式电除尘器脱除烟气中的汞。烟气中的汞如果以水溶性的氧化物形式存在就可以直接以颗粒物形式脱除,而如果以元素汞形式存在可以被吸附剂吸附后再被间接脱除。已经证实湿式电除尘器可去除燃中、高硫煤锅炉产生的亚微米级的颗粒物和酸雾排放。现在来看,如果在ESP(静电除尘器)之后布置湿式电除尘器(WESP)代替布袋除尘器,则对燃低硫份的次烟煤或褐煤锅炉可能会得到相同的汞排放控制效果。  相似文献   
43.
碱性锌锰电池中的有机代汞缓蚀剂   总被引:2,自引:1,他引:2  
综述了90年代碱性锌锰电池中有机代汞缓蚀剂的研究概况。从亲水基和疏水基两方面总结了缓蚀剂分子结构对缓蚀效果的影响,并提出了发展适合我国国情的有机代汞缓蚀剂的设想。作者的研究结果表明,将一种阳离子表面活性剂和一种肟类有机物复配,可得到一种缓蚀效率更高并有实用价值的代汞缓蚀剂。  相似文献   
44.
低气压汞灯紫外辐射的物理模型   总被引:1,自引:0,他引:1  
简述了低气压汞灯253.7nm紫外辐射空间传播的衰减机制,给出了物理模型及表达式并与实测结果作了对比,提供了紫外辐射实际应用时的参照数据及考虑要素.  相似文献   
45.
《分离科学与技术》2012,47(10):1638-1646
Sodium tripolyphosphate crosslinked chitosan was prepared and immobilized with pentamine moieties. The samples obtained were characterized by elemental analysis and FT-IR. The adsorption behavior of the samples was studied towards Hg2+ using batch and column methods. The adsorption depended on the pH of the medium and was explained to proceed via complex formation and/or ion exchange mechanisms. The uptake capacity was found to be 4.7 mmol/g at pH = 2. Selective separation of Hg2+ from a solution containing Pb2+, Cu2+, Ca2+, Zn2+, Fe3+, and Mg2+ was achieved at pH = 1. The values of the kinetics and the thermodynamic parameters of the uptake process were reported. The flow rate of 3 mL/min in column experiments was found to be the most preferable rate. The regeneration of the loaded resin was performed using 0.5 M potassium iodide.  相似文献   
46.
Particulate matter (PM) air pollution derives from combustion and non‐combustion sources and consists of various chemical species that may differentially impact human health and climate. Previous reviews of PM chemical component concentrations and sources focus on high‐income urban settings, which likely differ from the low‐ and middle‐income settings where solid fuel (ie, coal, biomass) is commonly burned for cooking and heating. We aimed to summarize the concentrations of PM chemical components and their contributing sources in settings where solid fuel is burned. We searched the literature for studies that reported PM component concentrations from homes, personal exposures, and direct stove emissions under uncontrolled, real‐world conditions. We calculated weighted mean daily concentrations for select PM components and compared sources of PM determined by source apportionment. Our search criteria yielded 48 studies conducted in 12 countries. Weighted mean daily cooking area concentrations of elemental carbon, organic carbon, and benzo(a)pyrene were 18.8 μg m?3, 74.0 μg m?3, and 155 ng m?3, respectively. Solid fuel combustion explained 29%‐48% of principal component/factor analysis variance and 41%‐87% of PM mass determined by positive matrix factorization. Multiple indoor and outdoor sources impacted PM concentrations and composition in these settings, including solid fuel burning, mobile emissions, dust, and solid waste burning.  相似文献   
47.
A simple and rapid non-chromatographic method was developed to determine methylmercury (MeHg) and inorganic mercury (iHg) levels in muscles tissues of 10 freshwater fish species. The MeHg and iHg were determined by cold vapour atomic absorption spectrometry after alkaline wet digestion of samples. The digested samples were reduced sequentially with stannous chloride and sodium tetrahydroborate for iHg and MeHg, respectively. Parameters such as carrier gas flow rate (argon), volume of oxidizing and potassium persulphate solutions were investigated in detail. The accuracy of the technique was evaluated by using certified reference material (DORM-2) and spiking the both Hg species in muscles tissue of a fish. The limits of detection were 0.117 and 0.133 μg kg−1 for MeHg and iHg, respectively. The concentrations of MeHg and iHg in muscles tissues of ten fish species were found in the range of (28.4–56.3) and (3.01–8.11) μg kg−1, respectively.  相似文献   
48.
Recent work on reactive flash sintering of powders of two oxides, bismuth and of iron oxide, into pure single phase bismuth ferrite, which was accomplished in a few seconds at low furnace temperatures, is expanded to four constituents, alumina, lithia, zirconia, and lanthana, to produce reasonably dense polycrystals of a predominantly single phase, cubic LLZO(Al). Transformation and sintering occur concurrently at a furnace temperature near 700°C, in ambient atmosphere, in just a few seconds. The process may simplify the preparation of complex ceramics with new chemistries and dopants, which are predicted from ab intio calculations to have special attributes, not only because the powders sinter quickly at low temperatures, but also because the need for stoichiometric powders as starting materials is obviated.  相似文献   
49.
50.
This study investigated mercury contamination levels in eight commercially valuable crustacean species caught off the Central Adriatic and Tyrrhenian coasts of Italy. Total mercury levels were measured by Thermal Decomposition-Amalgamation-Atomic Absorption Spectrophotometry. Results showed a high variability among species with values ranging from 0.070 to 1.24 (mg kg?1 wet weight). The lowest mercury levels were detected in caramote prawn (Penaeus kerathurus), warty crab (Eriphia verrucosa) and European spider crab (Maja squinado), decapods living in shallow waters. Levels exceeding the limits established by the European Commission were found in species living in close contact with bottom sediments: deepwater rose shrimp (Parapenaeus longirostris), blue and red shrimp (Aristeus antennatus) and Norway lobster (Nephrops norvegicus). For shrimps, the inter-individual variability observed was mostly related to the body size, indicating the accumulation of mercury with age. An estimation of the human intake of mercury associated to the consumption of the crustaceans sampled and its comparison with the Tolerable Weekly Intake are provided.  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