全文获取类型
收费全文 | 2116篇 |
免费 | 123篇 |
国内免费 | 128篇 |
专业分类
电工技术 | 197篇 |
综合类 | 133篇 |
化学工业 | 499篇 |
金属工艺 | 81篇 |
机械仪表 | 60篇 |
建筑科学 | 151篇 |
矿业工程 | 76篇 |
能源动力 | 355篇 |
轻工业 | 62篇 |
水利工程 | 17篇 |
石油天然气 | 88篇 |
武器工业 | 171篇 |
无线电 | 45篇 |
一般工业技术 | 80篇 |
冶金工业 | 245篇 |
原子能技术 | 31篇 |
自动化技术 | 76篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 48篇 |
2021年 | 52篇 |
2020年 | 45篇 |
2019年 | 42篇 |
2018年 | 31篇 |
2017年 | 44篇 |
2016年 | 51篇 |
2015年 | 53篇 |
2014年 | 106篇 |
2013年 | 92篇 |
2012年 | 133篇 |
2011年 | 194篇 |
2010年 | 127篇 |
2009年 | 138篇 |
2008年 | 101篇 |
2007年 | 142篇 |
2006年 | 162篇 |
2005年 | 116篇 |
2004年 | 94篇 |
2003年 | 103篇 |
2002年 | 87篇 |
2001年 | 89篇 |
2000年 | 62篇 |
1999年 | 61篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 24篇 |
1995年 | 24篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2367条查询结果,搜索用时 0 毫秒
991.
To solve the limitation of the fire test in high‐altitude areas only detecting a limited number of low‐pressure environments, in this paper, appropriate modifications of the FDS source codes were made to generate a new simulator program for low‐pressure applications. Standard fire experiments with different counts (1, 2, 18, and 27) of cardboard boxes were numerically simulated under different pressure levels (101, 90, 75, and 64 kPa). The computation data show consistent trends with the experimental results obtained in the low‐pressure tank at Lang Fang. Furthermore, the simulation results have been examined to show typical quantitative relationships: (a) The peak mass burning rate divided by the fire base dimension is correlated with the product of the pressure squared and the combustible characteristic length cubed. The exponential indices for the 1‐box fire, 18‐box fire, and 27‐box fire are 0.31, 0.29, and 0.29, respectively. (b) The heat release rate and mass burning rate show a good linearity at each fixed environmental pressure. In conclusion, the modified FDS is validated to work well under low‐pressure conditions, which can provide a receivable means to conduct low‐pressure fire simulation and analysis. 相似文献
992.
The burning and dripping behaviour of polyurethane (PU) foam is crucial for upholstered furniture fires due to the melting and dripping behaviour of the foam that results in a pool fire under the furniture, which enhances the combustion. The sample feeding vertical cone is developed to investigate the two-dimensional small-scale burning and dripping behaviour of vertically oriented PU foams where a constant irradiance is maintained at the exposed surface by means of automatic sample compensation. Seven different PU foams were investigated and classified as conventional foam or char-forming foam according to the observed surface phenomena during exposure to heat fluxes. The burning and dripping behaviour is found to depend on the foam density as well as the solid-phase char formation by the presence of fire retardant additives. The total mass loss rate and the dripping rate increase with higher foam density and with the presence of char formation. In contrary, the vaporisation rate is favoured at lower foam density and with the absence of char formation. Flexible foams of low density without the ability to form char tend to achieve low dripping rate where majority of the mass loss is via vaporisation, contributing directly to the gas-phase combustion. 相似文献
993.
Alexandra M. Lai Sierra Clark Ellison Carter Ming Shan Kun Ni Xudong Yang Jill Baumgartner James J. Schauer 《Indoor air》2020,30(2):294-305
Biomass combustion for cooking and heating releases particulate matter (PM2.5) that contributes to household air pollution. Fuel and stove types affect the chemical composition of household PM, as does infiltration of outdoor PM. Characterization of these impacts can inform future exposure assessments and epidemiologic studies, but is currently limited. In this study, we measured chemical components of PM2.5 (water-soluble organic matter [WSOM], ions, black carbon, elements, organic tracers) in rural Chinese households using traditional biomass stoves, semi-gasifier stoves with pelletized biomass, and/or non-biomass stoves. We distinguished households using one stove type (traditional, semi-gasifier, or LPG/electric) from those using multiple stoves/fuels. WSOM concentrations were higher in households using only semi-gasifier or traditional stoves (31%-33%) than in those with exclusive LPG/electric stove (13%) or mixed stove use (12%-22%). Inorganic ions comprised 14% of PM in exclusive LPG/electric households, compared to 1%-5% of PM in households using biomass. Total PAH content was much higher in households that used traditional stoves (0.8-2.8 mg/g PM) compared to those that did not (0.1-0.3 mg/g PM). Source apportionment revealed that biomass burning comprised 27%-84% of PM2.5 in households using biomass. In all samples, identified outdoor sources (vehicles, dust, coal combustion, secondary aerosol) contributed 10%-20% of household PM2.5. 相似文献
994.
Taina Siponen Tarja Yli‐Tuomi Pekka Tiittanen Pekka Taimisto Juha Pekkanen Raimo O. Salonen Timo Lanki 《Indoor air》2019,29(3):413-422
A six‐month winter‐spring study was conducted in a suburb of the northern European city of Kuopio, Finland, to identify and quantify factors determining daily personal exposure and home indoor levels of fine particulate matter (PM2.5, diameter <2.5 µm) and its light absorption coefficient (PM2.5abs), a proxy for combustion‐derived black carbon. Moreover, determinants of home indoor ozone (O3) concentration were examined. Local central site outdoor, home indoor, and personal daily levels of pollutants were monitored in this suburb among 37 elderly residents. Outdoor concentrations of the pollutants were significant determinants of their levels in home indoor air and personal exposures. Natural ventilation in the detached and row houses increased personal exposure to PM2.5, but not to PM2.5abs, when compared with mechanical ventilation. Only cooking out of the recorded household activities increased indoor PM2.5. The use of a wood stove room heater or wood‐fired sauna stove was associated with elevated concentrations of personal PM2.5 and PM2.5abs, and indoor PM2.5abs. Candle burning increased daily indoor and personal PM2.5abs, and it was also a determinant of indoor ozone level. In conclusion, relatively short‐lasting wood and candle burning of a few hours increased residents’ daily exposure to potentially hazardous, combustion‐derived carbonaceous particulate matter. 相似文献
995.
铜陵海螺10000t/d熟料生产线是中国第一、世界第四条生产线.该线烧成系统窑规格为O6.0m×95m,开创性采用了单分解炉双系列预热器,更加方便系统参数的调节和控制,系统操作更易于平衡和优化,并使系统投资额降低15%以上.系统配置的分解炉设有低NOx分解段,窑用燃烧器为丹麦史密斯公司的低NOx的DBC型Duoflex四通道煤粉燃烧器,经标定,在系统满负荷运行的正常工况下,出C1级预热器废气的NOx含量只有3×10-4左右.文章同时对该系统的设计进行了客观评价. 相似文献
996.
采用化学共沉淀法制备了纳米Fe3O4粒子,以微米Fe3O4、微米TiO2、纳米TiO2/Fe3O4及纳米Fe3O4为氧化剂配制了不同的发烟剂.采用XRD、DTA、红外透过率测试等方法对纳米Fe3O4及发烟剂的性能进行了表征,研究了发烟剂的燃烧性能和红外消光性能.结果表明,与常规氧化剂相比,纳米Fe3O4作氧化剂的发烟剂放热峰温前移,燃烧热变小,燃速加快,红外消光性能有一定提高.纳米Fe3O4用于发烟剂中氧化剂,有助于提高发烟剂的燃烧性能和红外消光性能. 相似文献
997.
张建辉 《中国锅炉压力容器安全》2008,(6):12-15
结合我市1台UG635—3.82/450-M型层燃电站锅炉改造成45t/h循环流化床锅炉的成功经验.对这2种炉型的燃烧特点进行比较和分析。 相似文献
998.
本文介绍了当前能源与环保问题的紧迫性,提出了根据我国的能源状况应对能源危机的措施———煤制甲醇,同时分析了甲醇柴油双燃料发动机的性能。 相似文献
999.
1000.
本文详细介绍了中温分离循环流化床生物质锅炉技术特点,设计工作中遇到的难点及解决的方案.以湖南某浆纸公司已运行的两台75/h生物质锅炉为例,详细介绍了锅炉运行产生的显著经济效益和社会效益.并客观分析其运行反应出的问题.对今后生物质锅炉制造提供借鉴. 相似文献