全文获取类型
收费全文 | 1804篇 |
免费 | 36篇 |
国内免费 | 368篇 |
专业分类
电工技术 | 82篇 |
综合类 | 118篇 |
化学工业 | 118篇 |
金属工艺 | 306篇 |
机械仪表 | 93篇 |
建筑科学 | 155篇 |
矿业工程 | 8篇 |
能源动力 | 22篇 |
轻工业 | 135篇 |
水利工程 | 41篇 |
石油天然气 | 76篇 |
武器工业 | 125篇 |
无线电 | 303篇 |
一般工业技术 | 176篇 |
冶金工业 | 51篇 |
原子能技术 | 176篇 |
自动化技术 | 223篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 25篇 |
2012年 | 31篇 |
2011年 | 272篇 |
2010年 | 113篇 |
2009年 | 68篇 |
2008年 | 55篇 |
2007年 | 41篇 |
2006年 | 56篇 |
2005年 | 56篇 |
2004年 | 300篇 |
2003年 | 176篇 |
2002年 | 166篇 |
2001年 | 104篇 |
2000年 | 42篇 |
1999年 | 109篇 |
1998年 | 63篇 |
1997年 | 43篇 |
1996年 | 37篇 |
1995年 | 47篇 |
1994年 | 58篇 |
1993年 | 85篇 |
1992年 | 58篇 |
1991年 | 54篇 |
1990年 | 42篇 |
1989年 | 23篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1962年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有2208条查询结果,搜索用时 15 毫秒
1.
铁路预应力混凝土技术研究及开发的回顾 总被引:1,自引:0,他引:1
本文概述铁道部科学研究院40多年来对预应力混凝土技术的研究及开发情况,如基本参数研究、新材料和新结构的试验和应用、新型桥梁支座的研制等.还论及对现有桥梁的评估和加固方法.文末对铁路预应力混凝土桥梁的近期发展作了介绍. 相似文献
2.
低温地板辐射供暖特性参数的研究 总被引:5,自引:0,他引:5
建立了低温地板辐射供暖房间各围护结构的热平衡关系式,计算了地板表面温度、热流密度、室内空气温度和围护结构内表面温度。介绍了计算地板表面温度和围护结构内表面温度的耦合程序,测试了地板辐射供暖房间的特性参数。 相似文献
3.
4.
5.
建筑能耗分析逐时气象资料的开发研究 总被引:16,自引:4,他引:16
逐时气象资料对建筑能耗动态模拟是不可缺少的。在编制《夏热冬冷地区居住建筑节能设计标准》时 ,应用了动态模拟计算软件。为了开发逐时气象资料 ,通过与美国劳伦斯·伯克利国家实验室的技术合作 ,研究建立了我国城市的逐时资料。介绍了由我国气象台站报道的气象参数建立太阳辐射量的数学模型 ,阐述了典型气象月的选取原则 ,以及逐时数值插补方法。 相似文献
6.
利用扫描电镜(SEM)、X-射线衍射(XRD)以及傅立叶红外光谱(FTIR)技术研究改性聚丙烯酰胺(MPAm)对其改性超细水泥复合材料水化的影响。结果表明,由于聚合物与水化物之间的强烈的相互作用,改性聚丙烯酰胺大大影响了水泥的正常水化程度,但却改善了水化产物的微观结构,有助于提高水泥的韧性以及其他性能如抗折强度。 相似文献
7.
Vizard CG Rimmer DL Pless-Mulloli T Singleton I Air VS 《The Science of the total environment》2006,370(1):61-69
A study of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) concentrations was undertaken in the vicinity of a municipal solid waste incinerator (MSWI) in Newcastle upon Tyne as a result of concerns raised by local residents about potential contamination from fugitive and stack emissions. The study area was divided into four sectors (north-east (NE), south-east (SE), north-west (NW) and south-west (SW)) around the MSWI, and sampling sites were located up to a distance of 2.25 km. Based on air dispersion modelling, the sampling density was four times greater in the NE (downwind) sector compared to the SW (upwind) direction, and twice as great in the NW and SE sectors. PCDD/F concentrations found in soil samples ranged from 6 to 1911 ng I-TEQ/kg DW with a median of 32 ng I-TEQ/kg DW. There was no evidence of elevated concentrations downwind of the MSWI compared to other directions, nor of any trend in concentration at increasing distance from the MSWI. We concluded, therefore, that the MSWI fugitive and stack emissions were not a major source of PCDD/F contamination. Analysis of PCDD/F homologue profiles showed that samples exhibiting furan-dominated and OCDD-dominated profiles and a profile characteristic of the MSWI ash occurred in distinct clusters. Those samples showing the furan-dominated profile had the largest PCDD/F concentrations measured as I-TEQ, followed by samples with the incinerator profile, the deposition profile, and the OCDD-dominated profile. We identified some contamination hotspots located in the SW and SE sampling sectors (upwind of the MSWI), and potential sources for these hotspots were sought by using historic land use data from maps of the locality dating back to 1856. We concluded that the cluster of very high concentrations of PCDD/F in soils showing the furan homologue profile were most likely to have resulted from the disposal of graphite electrode sludges from brine electrolysis carried out at a chemical works between the 1890s and the 1930s. 相似文献
8.
9.
Metal contamination of urban soils in the vicinity of a municipal waste incinerator: one source among many 总被引:7,自引:0,他引:7
Rimmer DL Vizard CG Pless-Mulloli T Singleton I Air VS Keatinge ZA 《The Science of the total environment》2006,356(1-3):207-216
Concern from local residents about possible contamination with metals and PCDD/F (dioxins and furans) from fugitive and stack emissions from the Byker municipal solid waste incinerator in Newcastle upon Tyne led the City Council to initiate a study of the concentration of these pollutants in soils. We report here the results for the metals and arsenic. Soils were sampled at distances up to 2.25 km from the incinerator stack. The intensity of sampling in concentric zones was four times greater in the northeast (down-wind) direction, and twice as great in the northwest and southeast directions, compared to the southwest (up-wind) direction. In total 163 samples were collected and analyzed for total As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Concentrations were generally elevated above background levels, but were typical of those found in other urban areas. For As, Cd, Cu, Hg, Pb, and Zn, contamination hotspots were identified. These were spread throughout the sampling area, and there was no evidence of greater concentrations down-wind of the incinerator compared to other directions, nor of any trend in concentration at increasing distance from the incinerator. We concluded that metal contamination resulting from the incinerator could not be detected in an environment with generally elevated concentrations. Potential sources for many of the hotspots of contamination were identified in a survey of historic land use based on maps of the locality dating back to 1856. Detailed investigations of particular areas with serious contamination will now be undertaken by the local authorities using the CLEA (Contaminated Land Exposure Assessment) model. 相似文献
10.