全文获取类型
收费全文 | 45090篇 |
免费 | 5437篇 |
国内免费 | 3501篇 |
专业分类
电工技术 | 10224篇 |
技术理论 | 3篇 |
综合类 | 4076篇 |
化学工业 | 1892篇 |
金属工艺 | 1123篇 |
机械仪表 | 2146篇 |
建筑科学 | 2305篇 |
矿业工程 | 10336篇 |
能源动力 | 1997篇 |
轻工业 | 957篇 |
水利工程 | 558篇 |
石油天然气 | 953篇 |
武器工业 | 311篇 |
无线电 | 2555篇 |
一般工业技术 | 1827篇 |
冶金工业 | 2609篇 |
原子能技术 | 190篇 |
自动化技术 | 9966篇 |
出版年
2024年 | 161篇 |
2023年 | 490篇 |
2022年 | 1116篇 |
2021年 | 1422篇 |
2020年 | 1667篇 |
2019年 | 1168篇 |
2018年 | 1161篇 |
2017年 | 1377篇 |
2016年 | 1469篇 |
2015年 | 1627篇 |
2014年 | 3081篇 |
2013年 | 2471篇 |
2012年 | 3832篇 |
2011年 | 3631篇 |
2010年 | 2608篇 |
2009年 | 2901篇 |
2008年 | 3010篇 |
2007年 | 3392篇 |
2006年 | 3084篇 |
2005年 | 2687篇 |
2004年 | 2324篇 |
2003年 | 2204篇 |
2002年 | 1479篇 |
2001年 | 1219篇 |
2000年 | 1034篇 |
1999年 | 756篇 |
1998年 | 549篇 |
1997年 | 400篇 |
1996年 | 360篇 |
1995年 | 307篇 |
1994年 | 252篇 |
1993年 | 163篇 |
1992年 | 154篇 |
1991年 | 96篇 |
1990年 | 62篇 |
1989年 | 64篇 |
1988年 | 56篇 |
1987年 | 43篇 |
1986年 | 22篇 |
1985年 | 10篇 |
1984年 | 29篇 |
1983年 | 41篇 |
1982年 | 20篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1975年 | 2篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1955年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
简述了我国钨矿业概况、现有采选技术水平及钨矿加工利用率 ;从资源配置出发 ,阐述了钨矿业发展存在的几个主要问题 ,并且针对性地提出了可持续发展的几点建议。 相似文献
52.
浅析异步电机电子软起动器的现状和展望 总被引:4,自引:0,他引:4
本文在分析异步电机电子软起动器的现状和展望的基础上,以一个当前正在设计完善的电子软起动器为例,基本说明新型电子软起动器的特点和结构功能。 相似文献
53.
54.
D.H.R. Price J.A. Sharp 《International Journal of Electrical Power & Energy Systems》1985,7(3):131-137
Peak demand forecasts obtained from six different univariate forecasting methods, under a range of conditions, were used to drive a capacity acquisition model of a large electrical supply system; and the resulting physical and financial performance of the model was observed for each set of forecasts. The results obtained are discussed in the context of their implications for the choice of load forecasting method used in capacity acquisition planning by a power supply undertaking. 相似文献
55.
Investigations of water inrushes from aquifers under coal seams 总被引:6,自引:0,他引:6
In many coal mines, limestone-confined aquifers underlie coal seams. During coal extraction from these mines, water inrushes occur frequently with disastrous consequences. This paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams. It then presents the water inrush mechanism. The main factors which control water inrushes include strata pressure, mining size, geologic structures and the water pressure in the underlying aquifer. Analysis shows that reduction of confinement due to mining is the major cause of the water-conducting failure in the floor strata. The depth of the failure zone is strongly dependent on the mining width. This paper also presents field observation results of the water-conducting failure in the floor strata, and applies the finite element method coupled with stress-dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction. Finally, theoretical and empirical methods to predict water inrushes are given, and technical measures for improving mine design and safety for coal extraction over aquifers are presented. These measures include fault and fracture grouting and mining method modification such as changing long-wall to short-wall mining. 相似文献
56.
57.
58.
Using Web resources to construct multilingual medical thesaurus for cross-language medical information retrieval 总被引:1,自引:0,他引:1
Due to the language barrier, non-English users are unable to retrieve the most updated medical information from the U.S. authoritative medical websites, such as PubMed and MedlinePlus. However, currently, there is no any cross-language medical information retrieval (CLMIR) system that can help Chinese-speaking consumers cross the language barrier in finding useful English medical information. A few CLMIR systems utilize MeSH (Medical Subject Headings) to help overcome the language barrier. Unfortunately, the traditional Chinese version of MeSH is currently unavailable.In this paper, we employ a semi-automatic term translation method to construct a Chinese–English MeSH by exploiting abundant multilingual Web resources, including Web anchor texts and search–result pages. Through this method, we have developed a Chinese–English Mesh Compilation System to assist knowledge engineers in compiling a Chinese–English medical thesaurus with more than 19,000 entries. Furthermore, this thesaurus has been used to develop a prototypical system for cross-language medical information retrieval, MMODE, which can help consumers retrieve top-quality English medical information using Chinese terms. 相似文献
59.
60.
铜铬锆合金是一种形变热处理材料,兼具了铜铬合金和铜锆合金的各种优良性能,经过时效处理的铜铬锆合金,与铜相比,高温强度有很大的改善,而且具有较高的导电率。所以铜铬锆合金广泛应用于电焊机、低压电器等行业。根据对铜铬锆成分的适当调整,可用作为电焊机电极,低压电器触桥、短路环等各种电接触材料。铜铬锆合金用于RMT1-250转换开关,接近于触桥材料的应用,但使用的条件更苛刻一些,要承受部分电弧的侵蚀和由此产生的高温,因此对材料要求具有良好的导电导热性和更高的高温强度。 相似文献