全文获取类型
收费全文 | 95013篇 |
免费 | 11403篇 |
国内免费 | 6392篇 |
专业分类
电工技术 | 15546篇 |
技术理论 | 16篇 |
综合类 | 7964篇 |
化学工业 | 9451篇 |
金属工艺 | 2658篇 |
机械仪表 | 3678篇 |
建筑科学 | 11033篇 |
矿业工程 | 4263篇 |
能源动力 | 13387篇 |
轻工业 | 2326篇 |
水利工程 | 5564篇 |
石油天然气 | 2545篇 |
武器工业 | 745篇 |
无线电 | 7469篇 |
一般工业技术 | 7986篇 |
冶金工业 | 4334篇 |
原子能技术 | 1323篇 |
自动化技术 | 12520篇 |
出版年
2024年 | 410篇 |
2023年 | 1925篇 |
2022年 | 3102篇 |
2021年 | 3605篇 |
2020年 | 3843篇 |
2019年 | 3347篇 |
2018年 | 2923篇 |
2017年 | 3535篇 |
2016年 | 3947篇 |
2015年 | 4055篇 |
2014年 | 6629篇 |
2013年 | 6229篇 |
2012年 | 7004篇 |
2011年 | 7631篇 |
2010年 | 6020篇 |
2009年 | 6041篇 |
2008年 | 5678篇 |
2007年 | 6451篇 |
2006年 | 5248篇 |
2005年 | 4285篇 |
2004年 | 3597篇 |
2003年 | 3091篇 |
2002年 | 2647篇 |
2001年 | 2204篇 |
2000年 | 1848篇 |
1999年 | 1445篇 |
1998年 | 1117篇 |
1997年 | 858篇 |
1996年 | 776篇 |
1995年 | 610篇 |
1994年 | 521篇 |
1993年 | 389篇 |
1992年 | 300篇 |
1991年 | 263篇 |
1990年 | 208篇 |
1989年 | 169篇 |
1988年 | 141篇 |
1987年 | 105篇 |
1986年 | 78篇 |
1985年 | 110篇 |
1984年 | 92篇 |
1983年 | 58篇 |
1982年 | 77篇 |
1981年 | 38篇 |
1980年 | 53篇 |
1979年 | 33篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1959年 | 6篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
石雪靖 《电力系统及其自动化学报》2020,(3):129-134
能源互联网是实现未来可持续发展的重要建设内容之一。构建能源互联网需要众多关键技术的支撑,而技术处于不断地进化过程中,了解技术发展的现实水平,把握技术的未来需求,可以指导正确的发展路线和科学的战略决策的制定。本文旨在评估能源互联网关键技术成熟度。基于文献计量方法评估理念建立具有系统性和普适性的综合评估指标体系,并引入数据分析方法和变异系数法构建技术成熟度综合评估方法,为能源互联网的建设提供科学的指导。对能源互联网的云大物移创新应用关键技术进行算例分析,结果表明该方法能准确地判断技术的成熟度,定位技术性能。 相似文献
83.
The metric representing the wind energy forecast error, when reported as a percent, is calculated quite differently than the error metrics for electricity transmission, electricity load, or in other industries such as manufacturing when they are also reported as a percent. The resulting calculated metric is quite different from what would be reported if the method utilized elsewhere was employed. This paper examines the possible forecast assessment and operational challenges associated with this finding. Concerning the prospects for improvement, the errors reported in MW of energy have a systematic component. With this insight, we developed a model to improve accuracy. 相似文献
84.
Youngseok Lee Cheolmin Park Nagarajan Balaji Youn-Jung Lee Vinh Ai Dao 《Israel journal of chemistry》2015,55(10):1050-1063
Over the past few decades, crystalline silicon solar cells have been extensively studied due to their high efficiency, high reliability, and low cost. In addition, these types of cells lead the industry and account for more than half of the market. For the foreseeable future, Si will still be a critical material for photovoltaic devices in the solar cell industry. In this paper, we discuss key issues, cell concepts, and the status of recent high-efficiency crystalline silicon solar cells. 相似文献
85.
Photocatalysts have attracted great research interest owing to their excellent properties and potential for simultaneously addressing challenges related to energy needs and environmental pollution. Photocatalytic particles need to be in contact with their respective media to exhibit efficient photocatalytic performances. However, it is difficult to separate nanometer-sized photocatalytic materials from reaction media later, which may lead to secondary pollution and a poor recycling performance. Hydrogel photocatalysts with a three-dimensional (3D) network structures are promising support materials for photocatalysts based on features such as high specific surface areas and adsorption capacities and good environmental compatibility. In this review, hydrogel photocatalysts are classified into two different categories depending on their elemental composition and recent progresses in the methods for preparing hydrogel photocatalysts are summarized. Moreover, current applications of hydrogel photocatalysts in energy conversion and environmental remediation are reviewed. Furthermore, a comprehensive outlook and highlight future challenges in the development of hydrogel photocatalysts are presented. 相似文献
86.
利用风电场历史功率数据预测未来一段时间内的风功率,对保障电网安全稳定运行具有重要的意义。本文提出一种基于奇异谱分析SSA(singular spectrum analysis)和长短时记忆LSTM(long-short term memory net⁃work)网络的时序特征预测框架用于短期风功率的预测。首先通过SSA对历史风功率原始数据进行降噪处理,然后经过数据转换之后,以LSTM网络为基础进行预测模型的训练,最后通过某风电场提供的两个风机的历史功率数据进行验证。实验结果表明,奇异谱分析对风电场的历史数据具有良好的降噪性,SSA+LSTM模型在测试数据上取得了较好的预测性能,能够有效进行短期风功率的预测。 相似文献
87.
Aline Kövilein Christin Kubisch Liyin Cai Katrin Ochsenreither 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(3):513-526
Malic acid derived from fossil resources is currently applied in the food and beverage industries with a medium global production capacity. However, in the transition from a fossil-based to a bio-based economy, biotechnologically produced l -malic acid may become an important platform chemical with many new applications, especially in the field of biopolymers. In this review, currently used petrochemical production routes to dl -malic acid are outlined and insights into possible bio-based alternatives for microbial l -malic acid production are provided. Besides ecological reasons, the possibility to produce enantiopure l -malic acid by microbial fermentation is the biggest advantage over chemical synthesis. State-of-the-art and open challenges concerning production host engineering, substrate choice and downstream processing are addressed. With regard to production hosts, a literature overview is given covering the leading natural production strains of Aspergillus, Ustilago and Aureobasidium, as well as Escherichia coli as the most important engineered recombinant host. The utilization of renewable substrates as an alternative to glucose is emphasized in particular as a key aspect for a competitive bio-based production. Out of the alternative substrates discussed in this review, the industrial side-streams crude glycerol and molasses seem to be most promising for large-scale l -malic acid production. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献
88.
流域泥沙灾害与泥沙资源性的研究 总被引:5,自引:0,他引:5
泥沙灾害与泥沙资源性是流域泥沙的重要属性,二者在一定条件下可以相互转化。本文论述了泥沙淤积、泥沙冲刷、岸滩崩塌、山地崩塌与泥石流、粗沙淤积的土地沙化等泥沙灾害,指出泥沙灾害具有时空分布的不均匀性、渐变性或突发性、群发性、转化性及危害严重性等;流域泥沙资源化的主要途径包括填海造陆及造地、引洪淤灌、堤防淤临淤背、建筑材料、湿地形成(河流、湖泊与河口海岸)等,指出流域泥沙资源化及其优化配置既要解决思想观念、基本理论、目标效益等方面的问题,还要考虑与水资源联合配置问题。 相似文献
89.
文中对曲沃县水资源开发利用现状进行了认真分析,并从思想观念、管理体制、管理模式上提出了问题,为解决问题提出了相应对策。 相似文献
90.