全文获取类型
收费全文 | 51479篇 |
免费 | 4989篇 |
国内免费 | 2146篇 |
专业分类
电工技术 | 5123篇 |
技术理论 | 4篇 |
综合类 | 10911篇 |
化学工业 | 4391篇 |
金属工艺 | 1102篇 |
机械仪表 | 3190篇 |
建筑科学 | 6477篇 |
矿业工程 | 926篇 |
能源动力 | 846篇 |
轻工业 | 1376篇 |
水利工程 | 1047篇 |
石油天然气 | 871篇 |
武器工业 | 435篇 |
无线电 | 7079篇 |
一般工业技术 | 2913篇 |
冶金工业 | 895篇 |
原子能技术 | 288篇 |
自动化技术 | 10740篇 |
出版年
2024年 | 122篇 |
2023年 | 663篇 |
2022年 | 1234篇 |
2021年 | 1444篇 |
2020年 | 1675篇 |
2019年 | 1240篇 |
2018年 | 982篇 |
2017年 | 1367篇 |
2016年 | 1692篇 |
2015年 | 2076篇 |
2014年 | 4329篇 |
2013年 | 3026篇 |
2012年 | 4506篇 |
2011年 | 5086篇 |
2010年 | 4222篇 |
2009年 | 3873篇 |
2008年 | 3163篇 |
2007年 | 3611篇 |
2006年 | 2862篇 |
2005年 | 2370篇 |
2004年 | 1887篇 |
2003年 | 1612篇 |
2002年 | 1304篇 |
2001年 | 1085篇 |
2000年 | 822篇 |
1999年 | 573篇 |
1998年 | 368篇 |
1997年 | 292篇 |
1996年 | 245篇 |
1995年 | 202篇 |
1994年 | 134篇 |
1993年 | 98篇 |
1992年 | 93篇 |
1991年 | 72篇 |
1990年 | 55篇 |
1989年 | 57篇 |
1988年 | 50篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1966年 | 5篇 |
1962年 | 5篇 |
1959年 | 4篇 |
1957年 | 4篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
本文主要总结了新冠疫情期间作者的电磁场理论课程在线教学经验。对比分析了录播和直播的优缺点后,选择录播教学方式。基于超星网络教学平台,展示了录播网络教学的具体措施,包括网上答疑和学习效果检查以及在线批改作业等。给出了网络教学可以为线下教学继续使用的方法和手段,为疫情结束后的正常教学提供了新的网络教学补充措施。 相似文献
5.
6.
《International Journal of Hydrogen Energy》2022,47(52):22203-22214
The gas purging states affect electricity output and energy storage capacity of unitized regenerative fuel cells. In this study, a model of unitized regenerative fuel cell is established. Cell voltages and operating temperatures influences on the dynamic distribution of thermal fluid during purging process and the discharge of residual liquid water in electrolytic cell mode are investigated. The motivation of the present study is better understanding the gas purging characteristics and its effect on reaction behaviors of unitized regenerative fuel cells. Simulation results reveal a significant influence of purging gas temperature on the water flooding and a great effect of operating voltage on the water diffusion. The operating temperature of electrolytic cell model almost has little effect on purging results at different cell temperature and the same purging gas temperature. When the purging gas temperature is changed, higher temperatures of cell and purging gas facilitate liquid water discharging out from the cell regions. In cell water flooding situation, when having large liquid content, the purging gas has little effects on the water expelling process. 相似文献
7.
《International Journal of Hydrogen Energy》2022,47(78):33272-33281
According to the International Energy Agency, only a small part of the full potential of biomass energy is currently used in the world. The annual amount of agricultural waste in the Russian Federation is estimated at about 152 million tons, and the energy potential of animal waste is 201 PJ/year. Anaerobic digestion is an efficient method of converting organic waste into renewable energy sources. Previously, the positive effect of pretreatment of various organic feedstocks in vortex layer apparatus (VLA) on the characteristics of anaerobic digestion and energy efficiency was shown. Currently, there is a significant interest in the world in obtaining biohydrogen from organic waste using the dark fermentation (DF) process. During pretreatment in the VLA, the iron working bodies are abraded and iron particles are introduced into the feedstock of the DF reactor. This may have a positive effect on the production rate and yield of hydrogen, which has not been previously studied. This work is aimed at evaluating the possibility of using the VLA as a method for pretreatment of a dark fermentation feedstock for the intensification of biohydrogen production. To achieve this goal, an experimental setup was constructed. It consisted of a 45 L DF reactor, a VLA and a process control system to collect data on the DF process parameters every 5 min. At a hydraulic retention time in the DF reactor of 24 h and in the VLA of 30 s, the hydrogen content in the biogas increased from 51.1% to 52.2%. At the same time, the pH increased from 3.85 to 4.8–4.9, and the hydrogen production rate increased by 16% to 1.941 L/(L day). The hydrogen yield was 80.9 ml/g VS. Thus, pretreatment of the feedstock in VLA can be an effective way to intensify the DF process; however, further study of the VLA operating modes is required in order to optimize the concentrations of iron particles introduced into the feedstock for the most efficient continuous production of dark fermentative biohydrogen. 相似文献
8.
土木工程施工课程作为土木工程及工程管理专业的学科基础课和核心专业课程,在疫情防控期间"停课不停教""停课不停学"的要求下,通过线上平台进行授课。由于土木工程施工课程内容庞杂、综合性强、实践性强,且章节之间关联性较弱,探究既能使学生快速适应,又能保证教学质量的在线教学方法至关重要。以华南某高校土木工程施工课程为例,基于中国大学MOOC、建筑云课、腾讯课堂、QQ群等线上平台讲授教学内容,并运用问卷调查对课程线上教学效果进行评价。结果表明,线上教学为学生提供了丰富灵活的学习方式,显著提高了学生的自主学习能力,扩大了学生的知识面,达到了较好的学习效果。 相似文献
9.
《Mechatronics》2022
This paper considers the shared path following control of an unmanned ground vehicle by a single person. A passive measure of human intent is used to blend the human and machine inputs in a mixed initiative approach. The blending law is combined with saturated super-twisting sliding mode speed and heading controllers, so that exogenous disturbances can be counteracted via equivalent control. It is proven that when the proposed blending law is used, the combined control signals from both the human and automatic controller respect the actuator magnitude constraints of the machine. To demonstrate the approach, shared control experiments are performed using an unmanned ground vehicle, which follows a lawn mower pattern shaped path. 相似文献
10.