全文获取类型
收费全文 | 358610篇 |
免费 | 30210篇 |
国内免费 | 18265篇 |
专业分类
电工技术 | 29864篇 |
技术理论 | 59篇 |
综合类 | 48656篇 |
化学工业 | 38590篇 |
金属工艺 | 14656篇 |
机械仪表 | 23692篇 |
建筑科学 | 48961篇 |
矿业工程 | 18686篇 |
能源动力 | 11005篇 |
轻工业 | 18156篇 |
水利工程 | 18163篇 |
石油天然气 | 15346篇 |
武器工业 | 3488篇 |
无线电 | 24169篇 |
一般工业技术 | 27029篇 |
冶金工业 | 18946篇 |
原子能技术 | 3847篇 |
自动化技术 | 43772篇 |
出版年
2024年 | 742篇 |
2023年 | 3434篇 |
2022年 | 6555篇 |
2021年 | 8265篇 |
2020年 | 8829篇 |
2019年 | 7352篇 |
2018年 | 7012篇 |
2017年 | 8744篇 |
2016年 | 10214篇 |
2015年 | 11650篇 |
2014年 | 21361篇 |
2013年 | 19379篇 |
2012年 | 24200篇 |
2011年 | 25971篇 |
2010年 | 20274篇 |
2009年 | 21417篇 |
2008年 | 20060篇 |
2007年 | 25892篇 |
2006年 | 24402篇 |
2005年 | 20860篇 |
2004年 | 17649篇 |
2003年 | 15858篇 |
2002年 | 13007篇 |
2001年 | 10970篇 |
2000年 | 9275篇 |
1999年 | 7575篇 |
1998年 | 5716篇 |
1997年 | 4955篇 |
1996年 | 4499篇 |
1995年 | 3818篇 |
1994年 | 3385篇 |
1993年 | 2499篇 |
1992年 | 2153篇 |
1991年 | 1620篇 |
1990年 | 1428篇 |
1989年 | 1243篇 |
1988年 | 1003篇 |
1987年 | 664篇 |
1986年 | 492篇 |
1985年 | 420篇 |
1984年 | 394篇 |
1983年 | 278篇 |
1982年 | 255篇 |
1981年 | 190篇 |
1980年 | 164篇 |
1979年 | 135篇 |
1978年 | 73篇 |
1977年 | 83篇 |
1976年 | 61篇 |
1975年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
81.
以中低温煤焦油沥青质为原料,采用NiMoW/γ-Al_2O_3商业催化剂,在反应温度380℃、反应压力8 MPa和反应时间1.5 h条件下,分别在不同剂油质量比(1∶25、1∶20、1∶15、1∶10)条件下进行加氢实验,通过采用元素分析、FT-IR、XRD、~1H-NMR和XPS等分析表征手段,考察不同剂油质量比对中低温煤焦油沥青质加氢转化过程的影响。结果表明,随着剂油质量比的增加,沥青质转化率提高,加氢产物分布也发生大幅变化,沥青质和芳香分轻质化转化为饱和分。但随着剂油质量比的进一步提高,同时也发生了更多的裂化反应和缩合反应,剂油质量比在合适范围能够很好地起到加氢轻质化且抑制结焦的效果。 相似文献
82.
83.
The supervision of a hybrid power plant, including solar panels, a gas microturbine and a storage unit operating under varying solar power profiles is considered. The Economic Supervisory Predictive controller assigns the power references to the controlled subsystems of the hybrid cell using a financial criterion. A prediction of the renewable sources power is embedded into the supervisor. Results deteriorate when the solar power is unsteady, owing to the inaccuracy of the predictions for a long-range horizon of 10 s. The receding horizon is switched between an upper and a lower value according to the amplitude of the solar power trend. Theoretical results show the relevance of horizon switching, according to a tradeoff between performance and prediction accuracy. Experimental results, obtained in a Hardware In the Loop (HIL) framework, show the relevance of the variable horizon approach. Power amplifiers allow us to simulate virtual components, such as a gas microturbine, and to blend their powers with that of real devices (storage unit, real solar panels). In this case, fuel savings, reaching 15%, obtained under unsteady operating conditions lead to a better overall performance of the hybrid cell. The overall savings obtained in the experiments amount to 12%. 相似文献
84.
A small handful of recent studies have addressed a phenomenon known as “phantom vibration syndrome”. This refers to when phone users perceive their device to vibrate, indicating that a call or text is incoming, when in fact the phone did not vibrate at all. Though these studies show that most users do not find phantom vibration hallucinations to be very bothersome, they also find that a large majority of users experience this phenomenon. This paper explores what the striking prevalence of phantom vibration syndrome means for our contemporary relationships with technology. I begin with a review of the theories purporting to explain these data, which largely rely on particular understandings of the brain. Next I develop an alternative theory of phantom vibration syndrome based on insights from the philosophical tradition of phenomenology. This account considers the ways users develop bodily and perceptual habits regarding how the phone is understood and used. By critically contrasting these different theories, we can refine our questions about what the high prevalence of phantom vibration syndrome implies about our contemporary technological situation. 相似文献
85.
86.
This paper introduces the potential feasibility that ELID (electrolytic in-process dressing) grinding replaces superfinishing in bearing manufacturing, but ELID grinding will bring new challenges. Different regions present distinguish surface profile due to the non-uniform contact in ELID groove grinding. However, few reports explaining the non-uniform contact are available. This article explores the mechanisms of the non-uniform contact during ELID groove grinding. Experiments on the non-uniform contact between bearing raceway and grinding wheel have been carried out under different conditions. The results show that non-uniform contact exists in ELID groove grinding process and it exerts influence on the profile of the raceway surface. Non-uniform contact influences the Rsk and Rku value all the time, but it influences the Ra value occasionally. Improvement strategies of eliminating the non-uniform contact are also discussed based on the experimental study. 相似文献
87.
Yange Yang Xiangyang Zhou Bing Li Cunman Zhang 《International Journal of Hydrogen Energy》2021,46(5):4259-4282
Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities. 相似文献
88.
89.
90.
近年来,我市因雷击而导致搅拌站系统瘫痪停产、影响工程进度的事件时有发生,在针对混凝土搅拌站配料秤的实际检定工作中,也常发现配料秤的称重传感器因雷击损坏而影响计量准确性。因此,对混凝土搅拌站防雷的研究具有重要意义。本文阐述了雷电对混凝土搅拌站的主要危害,分析了混凝土搅拌站常见的雷击原因及其防护措施,旨在引起生产方、安装方以及使用方对混凝土搅拌站防雷的共同重视。 相似文献