全文获取类型
收费全文 | 3218篇 |
免费 | 296篇 |
国内免费 | 84篇 |
专业分类
电工技术 | 164篇 |
综合类 | 183篇 |
化学工业 | 355篇 |
金属工艺 | 52篇 |
机械仪表 | 111篇 |
建筑科学 | 240篇 |
矿业工程 | 16篇 |
能源动力 | 60篇 |
轻工业 | 100篇 |
水利工程 | 69篇 |
石油天然气 | 37篇 |
武器工业 | 9篇 |
无线电 | 554篇 |
一般工业技术 | 261篇 |
冶金工业 | 54篇 |
原子能技术 | 80篇 |
自动化技术 | 1253篇 |
出版年
2023年 | 11篇 |
2022年 | 26篇 |
2021年 | 37篇 |
2020年 | 62篇 |
2019年 | 62篇 |
2018年 | 72篇 |
2017年 | 61篇 |
2016年 | 87篇 |
2015年 | 118篇 |
2014年 | 129篇 |
2013年 | 134篇 |
2012年 | 142篇 |
2011年 | 233篇 |
2010年 | 163篇 |
2009年 | 222篇 |
2008年 | 240篇 |
2007年 | 243篇 |
2006年 | 183篇 |
2005年 | 174篇 |
2004年 | 170篇 |
2003年 | 231篇 |
2002年 | 149篇 |
2001年 | 139篇 |
2000年 | 78篇 |
1999年 | 50篇 |
1998年 | 32篇 |
1997年 | 33篇 |
1996年 | 47篇 |
1995年 | 33篇 |
1994年 | 40篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 24篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1965年 | 1篇 |
排序方式: 共有3598条查询结果,搜索用时 15 毫秒
31.
Tsukasa Kinjo Naoki Saito Makoto Omodani 《Journal of the Society for Information Display》2012,20(10):559-565
Projected image on a screen is not always vivid enough when it is projected in a bright room. We generally have to choose either vivid image in a dark room or dull image in a bright room. We have suggested a new projection system which can realize high contrast image projection in a bright room. It is consisted of electronic paper screen, projector, and light‐emitting diode room light. The electronic paper (e‐Paper) screen alternates its whole surface white/black with 120 Hz. Room lights are controlled with the same frequency of 120 Hz with the opposite phase as that of the e‐Paper screen. We have confirmed that our new system has achieved higher contrast than the conventional projection system and also enough readability of paper documents in the room simultaneously. We have thus confirmed that our new system can bring an ideal condition, for audience, which can realize a vivid image projection in a bright room. 相似文献
32.
33.
嫦娥工程分为3个阶段,目前已经进行到第二阶段,即发射可在月球表面软着陆的登陆器,这便是嫦娥三号的主要任务。为了保证登月探测器在月球表面平稳地降落并且能够有效应对外太空环境下各种因素造成的干扰,需要对控制方案进行深入的研究和认真的设计。选择非线性变结构控制与状态反馈相结合的办法设计控制方案,设定关于系统高度、速度以及加速度等状态变量的性能指标,通过对相应的哈密尔顿函数采用极小值原理来得到变结构控制的相关输入,从而完成控制方案的数学模型。使用Simulink软件对所得到的数学模型分别在理想的情况以及存在干扰的情况下进行仿真,并且得到了满意的仿真结果。所设计的控制方案有一定的可行性,但因为大多数工作只是理论层次的分析,因此还需要进一步的研究。 相似文献
34.
35.
36.
37.
三盐基硫酸铅的生产工艺条件研究 总被引:2,自引:0,他引:2
介绍了氧化铅法中硝酸铅法生产三盐基硫酸铅两种生产工艺 ,对氧化铅法中硫酸的加入量、酸度、温度、时间等生产条件进行了研究 ,确定了最佳生产工艺条件 ,并对两种方法进行了简单对比 相似文献
38.
列举了业主规定的压型钢板的涂装配套及膜厚要求,介绍了锌加的涂装工艺、安全与环保、质量检验。 相似文献
39.
B. Giesbers B. Rienties D. Tempelaar W. Gijselaers 《Journal of Computer Assisted Learning》2014,30(1):30-50
With the increased affordances of synchronous communication tools, more opportunities for online learning to resemble face‐to‐face settings have recently become available. However, synchronous communication does not afford as much time for reflection as asynchronous communication. Therefore, a combination of synchronous and asynchronous communication in e‐learning would seem desirable to optimally support learner engagement and the quality of student learning. It is still an open question though, how to best design online learning with a blend of synchronous and asynchronous communication opportunities over time. Few studies have investigated the relationship between learners' actual use of synchronous and asynchronous communication over time. Therefore, this study addressed that relationship in an online course (N = 110), taking into account student motivation, and employing a dynamic inter‐temporal perspective. In line with our assumptions, we found some support for the expected association between autonomous motivation and engagement in asynchronous and synchronous communication, be it restricted primarily to the first course period. Also, positive relations between engagement in synchronous and asynchronous communication were found, with the strongest influence from using asynchronous to synchronous communication. This study adds to the knowledge base needed to develop guidelines on how synchronous communication can be combined with asynchronous learning. 相似文献
40.
The current paper examined the relationship between perceived characteristics of the learning environment in an e‐module in relation to test performance among a group of e‐learners. Using structural equation modelling, the relationship between these variables is further explored in terms of the proposed double mediation as outlined by Ning and Downing. These authors initially proposed that motivation and self‐regulation strategies are mediators between the perception of the learning environment and performance. In our replication and extension study, we substituted self‐reported self‐regulation with behavioural indicators of self‐regulation using navigation log files and focused on test‐taking rather than general motivation. We proposed that navigational patterns captured using log files can also help deduce self‐regulation in e‐modules and provide information in the absence of self‐reports. Path analyses provide partial support for our navigational hypotheses and the model. Implications of our results for the use of e‐module data and conclusions based on navigation are discussed. 相似文献