全文获取类型
收费全文 | 4229篇 |
免费 | 327篇 |
国内免费 | 290篇 |
专业分类
电工技术 | 292篇 |
综合类 | 458篇 |
化学工业 | 157篇 |
金属工艺 | 199篇 |
机械仪表 | 325篇 |
建筑科学 | 424篇 |
矿业工程 | 92篇 |
能源动力 | 69篇 |
轻工业 | 104篇 |
水利工程 | 200篇 |
石油天然气 | 99篇 |
武器工业 | 68篇 |
无线电 | 270篇 |
一般工业技术 | 361篇 |
冶金工业 | 149篇 |
原子能技术 | 13篇 |
自动化技术 | 1566篇 |
出版年
2024年 | 6篇 |
2023年 | 38篇 |
2022年 | 67篇 |
2021年 | 104篇 |
2020年 | 108篇 |
2019年 | 75篇 |
2018年 | 83篇 |
2017年 | 90篇 |
2016年 | 125篇 |
2015年 | 154篇 |
2014年 | 291篇 |
2013年 | 276篇 |
2012年 | 313篇 |
2011年 | 373篇 |
2010年 | 312篇 |
2009年 | 323篇 |
2008年 | 295篇 |
2007年 | 293篇 |
2006年 | 302篇 |
2005年 | 228篇 |
2004年 | 207篇 |
2003年 | 156篇 |
2002年 | 138篇 |
2001年 | 100篇 |
2000年 | 70篇 |
1999年 | 57篇 |
1998年 | 44篇 |
1997年 | 39篇 |
1996年 | 23篇 |
1995年 | 30篇 |
1994年 | 26篇 |
1993年 | 29篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1970年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1957年 | 2篇 |
1956年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有4846条查询结果,搜索用时 31 毫秒
1.
乡村产业中的化石能源设备逐渐被电能技术替代,引起了乡村负荷波动增大、部分时段产生集中高负荷的问题。为了解决以上问题,将低品位清洁能源应用至乡村的茶叶生产中,针对烘茶全过程的工艺要求提出了跨临界CO2热泵烘茶技术;并以某茶叶生产乡村为对象,对其代表台区的全年日用电量及产茶日负荷进行了分析,得出采用CO2热泵烘茶后其负荷得到大幅度削减,整体可降低至原负荷的39.6%~46.8%,峰值负荷与平时负荷的比值由原本的13.6降至5.4~6.2。跨临界CO2热泵应用至农产品生产中可有效缓解乡村供电压力。 相似文献
2.
3.
博物馆恒湿文物展柜的湿度控制至关重要,为实现展柜的自动恒湿功能,本文基于吸附式空气取水原理,提出了一种将环境水汽自动补充至恒湿文物展柜系统水箱的方法,并搭建了相应的小型空气取水装置,证明了该方法的可行性;同时,构建了传热传质耦合的空气取水装置数学模型,在获取环境温湿度对装置取水量的影响规律后,分析加热功率和吸附床结构对装置单位能耗取水量的影响;此外,为便于装置的后期推广应用,提出了两个基于吸附床高度和直径的量纲为1参数。结果表明:进口空气的温度对取水量影响较小,但进口空气的湿度对取水量影响较明显,取水量随着湿度增加而增加;加热功率存在最优值,单位能耗取水量随着加热功率先增大后减小;在当前几何参数组合下,两个量纲为1参数η=2、β=4时,装置的单位能耗取水量最高。 相似文献
4.
Biomass combined heat and power (CHP) plants connected to district heating networks are a very good opportunity to increase the share of renewable sources into energy systems. Frequently, important consumers are connected to ensure a stable base heat demand throughout the year but they often have higher requirements in terms of temperature (i.e. steam), which involves a high level of temperature in the district heating network during the whole year and high levels of heat losses in the network. This contribution presents the possibility to decrease the level of temperature at which the district heating network operates and to use high-temperature heat pumps connected locally at the consumption point to produce steam when it is required. An investigation of the global design and integration through thermodynamic simulation models is realised for the University of Liège district heating network. This study is intended to determine the heat pump coefficient of performance and, therefore, to assess the balance between the savings in terms of heat losses and the additional heat pump electricity consumption. 相似文献
5.
Energy impacts of urban water systems are substantial, but not typically analysed systemically. We develop a new system boundary framework including a utility, the ‘bulk water supply authority’ (SB1); the ‘urban water system’ including water use (SB2); and the ‘regional water system’ (SB3). We use the framework to review existing models and show that most address only one boundary. We apply the framework to quantify thermal equivalents of water-related energy in SB1 and SB2, and identify that over 96% of water-related energy in South East Queensland (SEQ) is outside SB1 and within SB2. Consideration of energy influenced by water use is paramount to systemic energy efficiency and optimisation in the urban water system. Clear articulation of system boundaries will improve modelling and management of the energy impact of urban water. Systemic modelling will help decision makers answer increasingly integrated and cross-system and sector questions regarding water and energy interactions. 相似文献
6.
7.
Fog computing has emerged to support the requirements of IoT applications that could not be met by today’s solutions. Different initiatives have been presented to drive the development of fog, and much work has been done to improve certain aspects. However, an in-depth analysis of the different solutions, detailing how they can be integrated and applied to meet specific requirements, is still required. In this work, we present a unified architectural model and a new taxonomy, by comparing a large number of solutions. Finally, we draw some conclusions and guidelines for the development of IoT applications based on fog. 相似文献
8.
Maqbool Ali Jamil Hussain Sungyoung Lee Byeong Ho Kang Kashif Sattar 《Expert Systems》2020,37(1):e12401
The case-based learning (CBL) approach has gained attention in medical education as an alternative to traditional learning methodology. However, current CBL systems do not facilitate and provide computer-based domain knowledge to medical students for solving real-world clinical cases during CBL practice. To automate CBL, clinical documents are beneficial for constructing domain knowledge. In the literature, most systems and methodologies require a knowledge engineer to construct machine-readable knowledge. Keeping in view these facts, we present a knowledge construction methodology (KCM-CD) to construct domain knowledge ontology (i.e., structured declarative knowledge) from unstructured text in a systematic way using artificial intelligence techniques, with minimum intervention from a knowledge engineer. To utilize the strength of humans and computers, and to realize the KCM-CD methodology, an interactive case-based learning system(iCBLS) was developed. Finally, the developed ontological model was evaluated to evaluate the quality of domain knowledge in terms of coherence measure. The results showed that the overall domain model has positive coherence values, indicating that all words in each branch of the domain ontology are correlated with each other and the quality of the developed model is acceptable. 相似文献
9.
Peter Adjei-Bamfo Kwame Ameyaw Domfeh Justice Nyigmah Bawole Albert Ahenkan Theophilus Maloreh-Nyamekye Stephanie Adjei-Bamfo 《Information Technology for Development》2020,26(4):742-761
ABSTRACT Governments globally are leveraging information and communication technology (ICT) growth towards improving the quality of public procurement services for socio-economic development. However, the extent of its application differs across nations. Notwithstanding the extant theoretical and empirical literature on IT for development, knowledge on how to assess readiness for adopting a full e-procurement system in the public sector of lower and lower-middle income countries (LMICs) begs for understanding. With the narrative of Ghana, we address this gap by drawing on the institutional and economic theory and the United Nations E-Government Development Index towards a holistic framework beyond the dyad of linear website functionalities and internet focus of prior e-government adoption models. Elite interviews gathered from multiple cases from Ghana’s public sector reveals the key readiness determinants for a full public sector e-procurement system. This study has significant implications for shaping the process-oriented management of government e-procurement projects towards socio-economic development in LMICs amid their complex institutional and socio-technical environments. 相似文献
10.