全文获取类型
收费全文 | 7366篇 |
免费 | 396篇 |
国内免费 | 194篇 |
专业分类
电工技术 | 386篇 |
综合类 | 295篇 |
化学工业 | 2037篇 |
金属工艺 | 337篇 |
机械仪表 | 371篇 |
建筑科学 | 477篇 |
矿业工程 | 295篇 |
能源动力 | 368篇 |
轻工业 | 604篇 |
水利工程 | 106篇 |
石油天然气 | 463篇 |
武器工业 | 32篇 |
无线电 | 620篇 |
一般工业技术 | 420篇 |
冶金工业 | 388篇 |
原子能技术 | 48篇 |
自动化技术 | 709篇 |
出版年
2024年 | 30篇 |
2023年 | 104篇 |
2022年 | 164篇 |
2021年 | 189篇 |
2020年 | 231篇 |
2019年 | 151篇 |
2018年 | 114篇 |
2017年 | 183篇 |
2016年 | 200篇 |
2015年 | 200篇 |
2014年 | 450篇 |
2013年 | 366篇 |
2012年 | 529篇 |
2011年 | 546篇 |
2010年 | 424篇 |
2009年 | 413篇 |
2008年 | 317篇 |
2007年 | 467篇 |
2006年 | 465篇 |
2005年 | 447篇 |
2004年 | 406篇 |
2003年 | 342篇 |
2002年 | 247篇 |
2001年 | 189篇 |
2000年 | 179篇 |
1999年 | 124篇 |
1998年 | 116篇 |
1997年 | 105篇 |
1996年 | 68篇 |
1995年 | 47篇 |
1994年 | 39篇 |
1993年 | 28篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有7956条查询结果,搜索用时 0 毫秒
21.
针对该厂离心制冷机组冷凝 /蒸发系统严重积垢危及设备安全运行这一现状 ,研究出了一种适宜的清洗方案并成功地应用于现场。为化学清洗技术如何有效地用于制冷行业特殊污垢的处理 ,提供了一个成功的范例 相似文献
22.
Concrete structures in main coal cleaning plants have been rebuilt and reinforced in the coal mines of the Shanghai Da-tun Energy Sources Co. Ltd., the first colliery of the Pingdingshan Coal Co. Ltd. and the Sanhejian mine of the Xuzhou Mining Group Co. Ltd. In these projects, the operating environment and reliability of concrete structures in the main plants of the three companies were investigated and the safety of the structures inspected. Qualitative and quantitative analyses were made on the spe-cial natural, technological and mechanical environments around the structures. On the basis of these analyses, we discuss the long-term, combined actions of the harsh natural (corrosive gases, liquids and solids) and mechanical environments on concrete structures and further investigated the damage and deteriorating mechanisms and curing techniques of concrete structures in the main coal cleaning plants. Our study can provide a theoretical basis for ensuring the reliability of concrete structures in main coal cleaning plants. 相似文献
23.
针对农村生活污水直接排放已经成为影响我国农村水环境质量主要因素之一的现状,从适合我国农村的以村落或居民点为单位进行生活污水分散式处理的思维入手,介绍了我国现今主要的分散式生活污水处理技术的原理、特点、不足及其应用现状;继而综合比较了这些技术的技术经济指标,提出了适合我国农村的分散式生活污水处理技术的设计原则;最后提出发展有较高水力负荷,并具备小规模设备化特征和多种生物处理单元复合的创新技术是我国农村生活污水处理技术发展的主要方向。 相似文献
24.
Children and youth who are hospitalized for a short or long term become socially isolated from their family, school and classmates. As their isolation increases, so does their vulnerability as a result of disrupted schooling. Research studies suggest different ways of using technologies to overcome this isolation and support children during this critical time of their lives. With technology for children in hospitals becoming increasingly commonplace, evaluating how it is used and its impact on children's learning and well‐being is necessary. In this paper, we systematically evaluated existing research on use of technologies for communication, support and educational purposes and its contribution to the well‐being of hospitalized children. A rigorous selection process yielded 14 research articles meeting the following criteria: empirical studies, using technologies for network of support, targeting hospitalized children and adolescents and targeting learning or social and emotional well‐being in the last decade. This review indicates that the use of technologies with children and youth in hospitals generally increased their potential for learning and improved connectivity with school. Our findings revealed that implementing digital pedagogies and creating online communities were helpful but underutilized features in the research. 相似文献
25.
CNGI 青海湖系统支撑青海湖区域的生态保护和多学科交叉融合的科研协作。针对青海湖基础设施种类众多的特点,我们发展了 IPv6 相关关键技术,应用于基础网络环境建设、数据传输、设备管理与状态监控等多个层面,并充分考虑了由此带来的安全隐患,制定了相应安全策略。这些技术可以支持多种传感器构成的 IPv6 网络,并支持 IPv6 的相关应用软件研发,促进大规模、跨领域复杂科学问题研究工作。 相似文献
26.
闫锦秀 《网络安全技术与应用》2013,(11):13-14
随着高新科学技术的发展,互联网的规模也不断扩大.人们对互联网需求也越来越多,而现有的网络体系结构开始难以满足人们的需求.本文主要通过讨论现今网络体系结构存在的问题,对相关技术进行研究. 相似文献
27.
28.
Hui Zhang Yinkun Sun Junjie Yang Zhiyu Sun Yanxin Zhao Xin Li Wei Wang Dongwei Lu Jun Ma 《Advanced functional materials》2023,33(40):2302816
Precise adjustment of the pore size, damage repair, and efficient cleaning is all challenges for the wider application of inorganic membranes. This study reports a simple strategy of combining dry-wet spinning and electrosynthesis to fabricate stainless-steel metal–organic framework composite membranes characterized by customizable pore sizes, targeted reparability, and high catalytic activity for membrane cleaning. The membrane pore size can be precisely customized in the range of 14–212 nm at nanoscale, and damaged membranes can be repaired by targeted treatment in 120 s. In addition, advanced oxidation processes can be used to quickly clean the membrane and achieve 98% flux recovery. The synergistic actions of the membrane matrix and the selective layer increase the adsorption energy of active sites to oxidant, shorten the electron transfer cycle, and enhance the overall catalytic performance. This study can provide a new direction for the development of advanced membranes for water purification and high-efficiency membrane cleaning methods. 相似文献
29.
Hosam El- El-Sofany 《计算机系统科学与工程》2022,43(2):573-589
Most user authentication mechanisms of cloud systems depend on the credentials approach in which a user submits his/her identity through a username and password. Unfortunately, this approach has many security problems because personal data can be stolen or recognized by hackers. This paper aims to present a cloud-based biometric authentication model (CBioAM) for improving and securing cloud services. The research study presents the verification and identification processes of the proposed cloud-based biometric authentication system (CBioAS), where the biometric samples of users are saved in database servers and the authentication process is implemented without loss of the users’ information. The paper presents the performance evaluation of the proposed model in terms of three main characteristics including accuracy, sensitivity, and specificity. The research study introduces a novel algorithm called “Bio_Authen_as_a_Service” for implementing and evaluating the proposed model. The proposed system performs the biometric authentication process securely and preserves the privacy of user information. The experimental result was highly promising for securing cloud services using the proposed model. The experiments showed encouraging results with a performance average of 93.94%, an accuracy average of 96.15%, a sensitivity average of 87.69%, and a specificity average of 97.99%. 相似文献
30.