全文获取类型
收费全文 | 10459篇 |
免费 | 1060篇 |
国内免费 | 442篇 |
专业分类
电工技术 | 290篇 |
技术理论 | 2篇 |
综合类 | 1023篇 |
化学工业 | 160篇 |
金属工艺 | 23篇 |
机械仪表 | 42篇 |
建筑科学 | 4391篇 |
矿业工程 | 255篇 |
能源动力 | 509篇 |
轻工业 | 51篇 |
水利工程 | 4273篇 |
石油天然气 | 284篇 |
武器工业 | 9篇 |
无线电 | 64篇 |
一般工业技术 | 267篇 |
冶金工业 | 62篇 |
原子能技术 | 11篇 |
自动化技术 | 245篇 |
出版年
2024年 | 11篇 |
2023年 | 102篇 |
2022年 | 215篇 |
2021年 | 250篇 |
2020年 | 266篇 |
2019年 | 297篇 |
2018年 | 240篇 |
2017年 | 324篇 |
2016年 | 415篇 |
2015年 | 483篇 |
2014年 | 864篇 |
2013年 | 698篇 |
2012年 | 814篇 |
2011年 | 935篇 |
2010年 | 683篇 |
2009年 | 650篇 |
2008年 | 637篇 |
2007年 | 657篇 |
2006年 | 584篇 |
2005年 | 501篇 |
2004年 | 360篇 |
2003年 | 321篇 |
2002年 | 308篇 |
2001年 | 244篇 |
2000年 | 182篇 |
1999年 | 182篇 |
1998年 | 126篇 |
1997年 | 97篇 |
1996年 | 87篇 |
1995年 | 68篇 |
1994年 | 61篇 |
1993年 | 49篇 |
1992年 | 67篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1979年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
为充分利用高层建筑物内部的水能包括生活污水及高层建筑物顶楼雨水,可将其转化为电能。由此设计的储能水管-冲击式水轮机装置即通过冲击式水轮机和发电机将高层建筑物内部储存的生活污水及雨水的势能转变为可供使用的电能,并通过建立单户用水模拟模型,设置储能水管对30、100层建筑进行发电模拟。模拟结果表明,储能水管-冲击式水轮机发电具有很好的发电效益和节能减排社会效益,获得了日发电过程中冲击式水轮机的水头变换和启停特性,为该系统中冲击式水轮机的个性设计提供了依据。 相似文献
2.
Sebastian Biba 《国际水》2018,43(5):622-641
This article analyzes China’s Mekong River politics before and after the establishment of the Lancang-Mekong Cooperation (LMC) from a comparative benefit-sharing perspective. China’s pre-LMC approach focused too much on the creation of economic benefits from and beyond the river while neglecting ecological benefits to the river. Moreover, despite the problems this ‘old’ approach caused for China and its downstream neighbours, China’s current LMC strategy seems to essentially replicate its former approach. While sustainable water resources management is identified as a priority area, actual cooperation and benefit sharing in this field remain insufficient. 相似文献
3.
Outcome‐based ventilation: A framework for assessing performance,health, and energy impacts to inform office building ventilation decisions 下载免费PDF全文
This article presents an outcome‐based ventilation (OBV) framework, which combines competing ventilation impacts into a monetized loss function ($/occ/h) used to inform ventilation rate decisions. The OBV framework, developed for U.S. offices, considers six outcomes of increasing ventilation: profitable outcomes realized from improvements in occupant work performance and sick leave absenteeism; health outcomes from occupant exposure to outdoor fine particles and ozone; and energy outcomes from electricity and natural gas usage. We used the literature to set low, medium, and high reference values for OBV loss function parameters, and evaluated the framework and outcome‐based ventilation rates using a simulated U.S. office stock dataset and a case study in New York City. With parameters for all outcomes set at medium values derived from literature‐based central estimates, higher ventilation rates’ profitable benefits dominated negative health and energy impacts, and the OBV framework suggested ventilation should be ≥45 L/s/occ, much higher than the baseline ~8.5 L/s/occ rate prescribed by ASHRAE 62.1. Only when combining very low parameter estimates for profitable impacts with very high ones for health and energy impacts were all outcomes on the same order. Even then, however, outcome‐based ventilation rates were often twice the baseline rate or more. 相似文献
4.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。 相似文献
5.
6.
ABSTRACTThis article explores how private owners can protect bodies of water through private property rights. It compares the use of conventional property rights in the Netherlands and New Zealand with a novel approach whereby a New Zealand river owns itself. 相似文献
7.
This study concerns an innovative project in the Dutch river Waal: the construction of longitudinal dams. By splitting the river into a main and secondary channel, these dams significantly impact the river landscape and the way it is used by different stakeholders. We report the results of a baseline study of the expectations local water-based recreationists (fishermen and boaters) had of the longitudinal dams before they were constructed. In addition, we explore their levels of place attachment, and use the visions of nature approach to elicit their lay philosophy of nature. We found that fishermen were more strongly attached to the area than boaters. Though expectations of the dams were generally negative, this differed significantly between fishermen and boaters, and between different dimensions of landscape change. We demonstrate the relevance of place attachment and visions of nature for understanding how recreationists perceive landscape change. 相似文献
8.
Cristina S. Borba Joo D. Latini Matheus T. Baumgartner Luiz C. Gomes Angelo A. Agostinho 《河流研究与利用》2019,35(4):386-395
The building of adduction channels (penstocks) that conduct water from reservoirs to turbines, which are located kilometres from the dam, is becoming common, optimizing the electricity generation in small dams. This design creates a river stretch with reduced discharge between the dam and the powerhouse. This study evaluates the short‐term impacts of the below‐dam decrease in river flow on fish assemblages. Samples were collected in the reduced flow stretch of the Castro Alves Hydropower Plant (Antas River, Rio Grande do Sul, Brazil) before the reservoir started operating (January 2008; mean discharge of 103.7 m3/s) and immediately after operation began (March 2008; mean discharge of 12.4 m3/s). Sampling was conducted in distinct habitats of the reduced flow stretch (slow waters—gillnets, sand beaches—seining nets, structured littoral—electrofishing, and fast waters—cast nets) with a strongly standardized effort. The attributes of the fish assemblages were not negatively affected by the flow reduction in any habitat sampled. However, distinct changes in the spatial structure were observed considering the different types of habitat predominantly used by the species, which represents an entire reorganization of the fish assemblages in the short term. It is fundamental that these short‐term aspects be considered in the licensing of hydropower plants in addition to the long‐term changes. 相似文献
9.
推进澜湄合作是构建周边命运共同体的具体实践,以“同饮一江水,命运紧相连”为主题的澜湄合作机制也为构建澜湄国家命运共同体提供了推进方向。环境问题是澜湄流域最为核心的问题之一,面向澜湄合作中的环境利益问题,文章结合共同体的理念,基于霍尔三维结构理论,总结出合作伙伴环境利益共同体模式、合作联盟环境利益共同体模式与一体化环境利益共同体模式的三种环境利益共同体模式,通过建立环境利益共同体模式的评价指标体系,利用网络层次分析法对澜湄环境利益共同体模式进行评价,选择适合澜沧江-湄公河的环境利益共同体模式。结果表明,在当前的澜湄现状下,以“澜湄六国通过开发流域资源发展本国经济而同时受到其他主体监督以保证不破坏澜沧江-湄公河的生态环境”为主要内容的合作联盟环境利益共同体模式更适合澜湄流域各国,这一模式可以有效解决流域各国经济与环境“两难重”的困境。 相似文献
10.
扬子江城市群地处长江经济带的下游重要门户地区,是江苏省“1+3”重点功能区发展的龙头引擎,打造扬子江城市群的绿色生态走廊对建设“强富美高”新江苏和落实长江大保护均具有重要战略意义。论文聚焦扬子江城市群工业能源碳排放脱钩及其驱动因素分析,研究得出:1)扬子江城市群整体工业碳排放量呈现波动上升的变化趋势,其中南京市和苏州市的碳排放增量明显大于其他城市;2)扬子江城市群工业能源碳排放脱钩大致经历了扩张连接、强脱钩以及弱脱钩3个阶段,整体上脱钩水平逐渐提高,但稳定性不高,各城市工业能源碳排放脱钩水平差异较大,但在逐步优化中;3)从驱动因素看,碳排放强度效应和能源强度效应对脱钩水平有促进作用,工业经济规模效应、区域经济比重和能源结构则相反。基于此,论文提出加强低碳城市试点建设、探索构建全域碳权交易市场、调整优化能源结构、推动科技创新等建议,以促进扬子江城市群工业建设高质量发展。 相似文献