全文获取类型
收费全文 | 24372篇 |
免费 | 3218篇 |
国内免费 | 2014篇 |
专业分类
电工技术 | 3469篇 |
技术理论 | 2篇 |
综合类 | 2343篇 |
化学工业 | 1247篇 |
金属工艺 | 437篇 |
机械仪表 | 2041篇 |
建筑科学 | 1066篇 |
矿业工程 | 479篇 |
能源动力 | 451篇 |
轻工业 | 3259篇 |
水利工程 | 355篇 |
石油天然气 | 1271篇 |
武器工业 | 282篇 |
无线电 | 2396篇 |
一般工业技术 | 1922篇 |
冶金工业 | 628篇 |
原子能技术 | 165篇 |
自动化技术 | 7791篇 |
出版年
2024年 | 201篇 |
2023年 | 530篇 |
2022年 | 968篇 |
2021年 | 1152篇 |
2020年 | 1177篇 |
2019年 | 955篇 |
2018年 | 878篇 |
2017年 | 1097篇 |
2016年 | 1097篇 |
2015年 | 1224篇 |
2014年 | 1786篇 |
2013年 | 1643篇 |
2012年 | 1986篇 |
2011年 | 2100篇 |
2010年 | 1441篇 |
2009年 | 1427篇 |
2008年 | 1269篇 |
2007年 | 1492篇 |
2006年 | 1304篇 |
2005年 | 1041篇 |
2004年 | 858篇 |
2003年 | 680篇 |
2002年 | 600篇 |
2001年 | 441篇 |
2000年 | 384篇 |
1999年 | 277篇 |
1998年 | 256篇 |
1997年 | 222篇 |
1996年 | 156篇 |
1995年 | 152篇 |
1994年 | 118篇 |
1993年 | 98篇 |
1992年 | 84篇 |
1991年 | 71篇 |
1990年 | 59篇 |
1989年 | 54篇 |
1988年 | 38篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 26篇 |
1984年 | 33篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1961年 | 4篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A non-iterative identification method with parameterization of the unknown dead-zone is proposed for Hammerstein systems in presence of asymmetric dead-zone nonlinearities.The canonical parameterized model which is a single expression without segmentation is utilized to describe the dead-zone,based on which a universal-type parametric model can be established to approximate the entire system.This model can be established without separating the nonlinear part from the linear part.The dead-zone parameters and the coefficients in the linear transfer function can be estimated simultaneously according to the proposed algorithm.Numerical experiments are presented to illustrate the effectiveness of the proposed scheme. 相似文献
42.
43.
A terahertz time-domain spectroscopy(THz-TDS)imaging system can obtain high-dimensional signals with substance fingerprint information.By introducing geometric algebra,a novel signal analysis approach to THz-TDS signals is developed based on an optical physical mechanism.Using this approach,signals are represented with vectors in the high-dimensional real vector space.Geometric distribution properties and algebraic relationships of THz-TDS signals are deduced.It is proved that every complex refractive index of substances relates to a unique 2-blade,the vectors corresponding to the samples of the same substance are collinear and belong to the intrinsic 2-blade of the substance.When decomposed through the conformal split with respect to a 2-blade,THz-TDS signals of high dimensionality can be related to vectors in a 2-dimensional subspace.Based on the conformal split properties we deduced,two criteria for substance identification on the basis of THz-TDS signals are proposed.Accordingly,a novel substance identification method via the conformal split is presented.In the method,the 2-blade related to each "known" substance is calculated with two vectors corresponding to THz-TDS signals measured from samples of the substance but with dierent thicknesses.Using the conformal split with respect to those 2-blades,an identified vector corresponding to a THz-TDS signal is linearly related to the vector in a 2-dimensional subspace.The substance of a sample can be identified using criteria on the projected vectors in the subspaces.This method can contribute to accurate classification and identification.Finally,two experiments are presented that show the feasibility and accuracy of this method. 相似文献
44.
开关柜误操作造成的事故越来越成为影响电力行业安全生产的主要事故类型之一。鉴于此,文章研究了一套智能高压开关柜自动识别系统。本系统中开关柜侧的装置在柜门被打开时可播放语音提示信息,并将开关柜开门关门等事件通过PT2262编码,再无线发送传输到后台。后台接收后,经F330单片机软件解码,并在触摸屏上记录事件的类型和时间。该系统对防止由于工作人员选错开关柜造成的误操作有一定的效果。 相似文献
45.
46.
王勇杰 《电脑编程技巧与维护》2012,(10):50-52
针对校园电子商务的产生和发展进行了阐述,对校园电子商务的功能模块进行设计和描述,提出了校园电子商务带来的影响,并探讨了校园电子商务在信用、物流、市场规划、管理模式、安全支付等方面存在的问题。 相似文献
47.
Roberto Truzoli Veronica Pirola Stella Conte 《Journal of Computer Assisted Learning》2021,37(4):940-952
The lockdown due to COVID-19 in Italy resulted in the sudden closure of schools, with a shift from traditional teaching to the online one. Through an online questionnaire, this survey explores teachers' experience of online teaching, the level of risk factors (e.g., stress) and protective factors (e.g., locus of control) and their impact on satisfaction levels during the social distancing. One hundred seven high school teachers from Lombardy, an Italian region very affected by the COVID-19 outbreak, participated. Results show that depression and stress are the main predictors of satisfaction levels for online teaching. In addition, coping, locus of control and self-efficacy emerge as important protective factors. Finally, although there is great satisfaction with the online teaching experience, critical elements emerged. This study is relevant because it describes the critical elements of the online teaching experience, and identifies some protective factors and the main risk factors in teachers operating in an area strongly marked by social restrictions imposed by the pandemic. High school teachers emerge as a sub-group of the general population with specific psychological reactions. Considering the results, it is possible to suggest providing high-quality educational support and crisis-psychological oriented services to teachers, and help to maintain the psychological well-being. 相似文献
48.
Nowadays, cities are the most relevant type of human settlement and their population has been endlessly growing for decades. At the same time, we are witnessing an explosion of digital data that capture many different aspects and details of city life. This allows detecting human mobility patterns in urban areas with more detail than ever before. In this context, based on the fusion of mobility data from different and heterogeneous sources, such as public transport, transport‐network connectivity and Online Social Networks, this study puts forward a novel approach to uncover the actual land use of a city. Unlike previous solutions, our work avoids a time‐invariant approach and it considers the temporal factor based on the assumption that urban areas are not used by citizens all the time in the same manner. We have tested our solution in two different cities showing high accuracy rates. 相似文献
49.
Huihua Liu Eva Bracht Xin‐an Zhang Bret Bradley Rolf van Dick 《Creativity & Innovation Management》2021,30(1):129-143
An increasing number of individuals work in jobs with little standardization and repetition, that is, with high levels of job non‐routinization. At the same time, demands for creativity are high, which raises the question of how employees can use job non‐routinization to develop creativity. Acknowledging the importance of social processes for creativity, we propose that transformational leaders raise feelings of organizational identification in followers and that this form of identification then helps individuals to develop creativity in jobs with little routinization. This is because organizational members evaluate and promote those ideas as more creative, which are in line with a shared understanding of creativity within the organization. To investigate these relationships, we calculated a mediated moderation model with 173 leader–follower dyads from China. Results confirm our hypotheses that transformational leadership moderates the relationship between job non‐routinization on employee creativity through organizational identification. We conclude that raising feelings of social identity is a key task for leaders today, especially when working in uncertain and fast developing environments with little repetition and the constant need to develop creative ideas. 相似文献
50.
铁路信号电缆是保证列车安全运营的重要组成部分,其故障严重影响列车的安全运营;由于其经多个分线盒接线柱连接的敷设特点,存在中间接头过多,致使传统的电缆故障检测方法应用受到了极大的限制;为此,通过在电缆中间分线盒的备用芯线对接线柱中接入固定阻值的电阻,将备用芯线对形成闭合回路网络,然后在线监测其电阻阻值,利用回路阻值的变化来反映电缆状态,并以在线监测备用芯线对代替在用芯线对,进而在不影响正常列控信号传输的情况下实现了信号电缆的故障在线监测;经实际测试,有效地解决了铁路信号电缆断线故障的在线监测及定位。 相似文献