全文获取类型
收费全文 | 11451篇 |
免费 | 1361篇 |
国内免费 | 669篇 |
专业分类
电工技术 | 593篇 |
综合类 | 1390篇 |
化学工业 | 755篇 |
金属工艺 | 360篇 |
机械仪表 | 882篇 |
建筑科学 | 1086篇 |
矿业工程 | 675篇 |
能源动力 | 563篇 |
轻工业 | 530篇 |
水利工程 | 391篇 |
石油天然气 | 284篇 |
武器工业 | 145篇 |
无线电 | 1428篇 |
一般工业技术 | 2742篇 |
冶金工业 | 485篇 |
原子能技术 | 183篇 |
自动化技术 | 989篇 |
出版年
2024年 | 18篇 |
2023年 | 118篇 |
2022年 | 237篇 |
2021年 | 294篇 |
2020年 | 354篇 |
2019年 | 276篇 |
2018年 | 278篇 |
2017年 | 319篇 |
2016年 | 450篇 |
2015年 | 428篇 |
2014年 | 682篇 |
2013年 | 711篇 |
2012年 | 829篇 |
2011年 | 918篇 |
2010年 | 725篇 |
2009年 | 765篇 |
2008年 | 634篇 |
2007年 | 812篇 |
2006年 | 775篇 |
2005年 | 618篇 |
2004年 | 498篇 |
2003年 | 444篇 |
2002年 | 357篇 |
2001年 | 347篇 |
2000年 | 281篇 |
1999年 | 220篇 |
1998年 | 200篇 |
1997年 | 161篇 |
1996年 | 135篇 |
1995年 | 120篇 |
1994年 | 100篇 |
1993年 | 74篇 |
1992年 | 67篇 |
1991年 | 41篇 |
1990年 | 45篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 22篇 |
1986年 | 13篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1963年 | 3篇 |
1959年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
41.
《能源学会志》2020,93(6):2511-2525
Oxy-fuel combustion of heavy oil can be applied to oil field steam injection boilers, allowing the utilization of both heavy oil and CO2 resources. This paper studied the local distribution characteristics of OH on oxy-fuel combustion of heavy oil during the ignition and stable combustion processes. During the ignition process, we observed the generation and evolution of fire kernel, and got the flame propagation velocity. During the stable combustion process, the results showed that the OH distribution and its relative signal intensity were influenced by the oxygen concentration, excess air coefficient, gas flow, reaction atmosphere, oil mist scattering, incident laser energy and laser sheet position. In the same reaction atmosphere, the ranges of OH dense distribution and the high temperature area increased as O2 concentration increased. In the same O2 concentration, both the ranges of OH dense distribution and the high temperature area in O2/N2 were larger than that in O2/CO2. In 29% O2/71% CO2, the flame shape was similar to combust in air, while the OH relative signal intensity and its volatility were much larger than that in air. In the same combustion condition, the location of high concentration of OH relative concentration field lagged behind the high temperature area. The results further reveal the differences between the conventional and oxy-fuel combustion. 相似文献
42.
43.
The combustion and emission formation process of liquid fuel in the trapped vortex combustor(TVC)are very complicated.A trapped vortex combustor with replaceable bluff-bodies was designed to investigate these processes.The bluff-body widths varied from 0.021 m to 0.036 m.Experimental tests were carried out.Liquid RP-3 aviation kerosene was used in the tests.Emissions were measured under atmospheric pressure.The combustion process was analyzed theoretically in the viewpoints of relative evaporation time,mixing time and reaction time.Numerical simulations were also conducted to help analyze the formation and depletion processes of pollutants in TVC.The results reveal that atomization was a critical factor for formation and depletion processes of pollutants.By controlling mixing speed of burned and unburned gases and thus fuel-air uniformity,turbulence intensity could also affect emission levels.In addition,residence time also affected the emissions by affecting combustion completeness and the time for NOx formation.All these factors were combined in a complicated way to affect combustion process and pollutant emissions. 相似文献
44.
生物燃料作为化石燃料的替代物越来越受到人们的重视,脂肪酸甲酯(FAEEs)是生物燃料中的重要组成成分。本文利用布里渊散射法,分别沿0.1、1、3、5、7和10 MPa六条等压线,在293.15 ~ 373.15 K的温度范围内,测量了碳酸二甲酯的液相音速。为方便工程应用,根据实验数据给出了碳酸二甲酯音速与温度和压力的关联式。在本文的p – T热力学区域内,实验值与关联计算值之间的平均绝对误差为0.20%。最后,结合碳酸二甲酯音速实验值和密度文献值,给出了碳酸根
(-CO3)、甲氧基(CH3O-)基团的Wada常数基团贡献值,分别为0.72769±103和0.66851±103。 相似文献
45.
为了降低既有建筑附属用房产生的噪声对居民生活的影响、改善居住建筑声环境,对既有居住建筑附属用房地下换热站的噪声源以及噪声传播途径进行了分析;以既有居住建筑地下换热站室内噪声实测数据为基础,对室内环境的声学特征进行分析。在综合考虑居民的健康和舒适的基础上,提出了针对该附属用房的降噪处理改造设计方案。经过改造后的空间噪声明显降低,空间声环境指标达到标准要求,有效地改善了居住建筑的声环境。文中提出的改造设计方案为制定民用建筑附属用房声学设计标准提供了技术支撑。 相似文献
46.
文中针对变电站高压并联电抗器噪声对环境的影响问题及其控制要求,通过实验研究了高压并联电抗器噪声的影响因素及其控制措施。文中采用改进声强法实测了湖北省内15座变电站37组共111台500 kV高压并联电抗器声功率级,并对其进行了分析。测试结果表明,随着运行年限的增加,电抗器最大声功率级逐步增大。由于设备额定容量与额定电压的提高,使用新的绝缘材料和设计方案后,在一定程度上会起到减震降噪作用。同时,电抗器采用散热片四周布置方式,也能实现对噪声的控制。针对高压电抗器的噪声控制,文中从声源控制、传播过程控制角度,提出相应的控制措施。其中,声源主要通过改善材料和设计进行控制。以某500 kV变电站的降噪处理为例,利用SoundPLAN噪声分析软件,提出了隔声屏障控制方案,使噪声平均声压级降低约6 dB(A),从而满足噪声控制的要求。文中的研究内容对于指导变电站的设计及降噪处理具有重要意义。 相似文献
47.
48.
某微细粒嵌布磁铁矿选矿工艺研究 总被引:1,自引:0,他引:1
针对某微细粒磁铁矿进行了全磁选流程和磁选-反浮选流程对比试验研究。结果表明,在最终磨矿细度相当的情况下,2种工艺流程都获得了产率48%左右、TFe品位66%左右、回收率80%左右的铁精矿指标,而采用磁选-反浮选流程的第三段磨矿量比全磁选流程减少了2/3。磁选-反浮选流程具有显著的节能降耗优势。 相似文献
49.
The balance between low carbon development and rapid economic growth is a ‘Gordian knot’ for most countries. This study aims to explore the practicable route of lowering carbon intensity with the expansion of the Information and Communication Technologies (ICT) industry in China. Using the provincial panel data from 2000 to 2017, the paper employs five indicators to empirically investigate the determinant mechanism of carbon intensity based on the refined Stochastic Impact by Regression on Population, Affluence, and Technology (STIRPAT) and spatial econometric models. The findings demonstrate that the ICT industry is the main force in adjusting carbon intensity. Despite constraint by the rebound effect, the net effect of the ICT industry shows a significant positive impact on lowering carbon intensity under the consideration of spatial dependence. Furthermore, compared with developed regions, the contribution of ICT on regional inequality of carbon intensity shows a higher share in developing regions. By applying the Oaxaca-Ransom counterfactual decomposition, the results reveal that there are substantial regional gaps between multi-comparable groups. The composite effect of informatization, industrialization, and urbanization accounts for the major share of the regional gap. Thus, policymakers should pay more attention to enhancing the ICT infrastructure in developing regions, boosting the ICT-related technology investment in specific sectors, coordinating regional cooperation, and balancing the migration of skilled workers. 相似文献
50.