首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   273152篇
  免费   21481篇
  国内免费   14085篇
电工技术   17461篇
技术理论   51篇
综合类   37731篇
化学工业   29344篇
金属工艺   9856篇
机械仪表   14642篇
建筑科学   40002篇
矿业工程   15211篇
能源动力   8107篇
轻工业   14977篇
水利工程   14161篇
石油天然气   11293篇
武器工业   2555篇
无线电   18253篇
一般工业技术   19454篇
冶金工业   15551篇
原子能技术   2754篇
自动化技术   37315篇
  2024年   852篇
  2023年   2590篇
  2022年   5086篇
  2021年   6032篇
  2020年   6380篇
  2019年   5318篇
  2018年   5044篇
  2017年   6120篇
  2016年   7315篇
  2015年   8313篇
  2014年   15276篇
  2013年   13942篇
  2012年   18198篇
  2011年   19388篇
  2010年   15338篇
  2009年   16128篇
  2008年   15112篇
  2007年   19727篇
  2006年   18522篇
  2005年   16190篇
  2004年   13750篇
  2003年   12434篇
  2002年   10217篇
  2001年   8646篇
  2000年   7278篇
  1999年   5973篇
  1998年   4469篇
  1997年   3951篇
  1996年   3636篇
  1995年   3085篇
  1994年   2742篇
  1993年   2060篇
  1992年   1835篇
  1991年   1368篇
  1990年   1188篇
  1989年   1055篇
  1988年   841篇
  1987年   571篇
  1986年   434篇
  1985年   357篇
  1984年   337篇
  1983年   244篇
  1982年   218篇
  1981年   170篇
  1980年   135篇
  1979年   112篇
  1978年   64篇
  1977年   74篇
  1976年   55篇
  1975年   55篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
11.
12.
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   
13.
14.
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter.  相似文献   
15.
16.
针对现有海量点云可视化方法存在索引构建时间长、内存占用大等问题,研究一种八叉树索引结合OSG分页结点的快速可视化方法,可在占用较小内存的基础上快速建立点云索引并实时调度。采用八叉树索引结构对海量点云进行数据组织,建立各层级的八叉树结点并以文件映射的方式分块保存,对结点文件重组织转换为支持OSG渲染引擎的多分辨率点云数据。采用基于OSG分页结点的实时调度技术,对海量点云进行高质量可视化。与目前两款主流的点云数据处理商业软件进行实验对比分析,结果表明所提方法具有索引建立速度快、内存占用小等优点,同时可视化交互更加流畅,适用于各种配置计算机下海量点云数据的调度管理与实时可视化。  相似文献   
17.
In this letter, we address the problem of Direction of Arrival (DOA) estimation with nonuniform linear array in the context of sparse Bayesian learning (SBL) framework. The nonuniform array output is deemed as an incomplete-data observation, and a hypothetical uniform linear array output is treated as an unavailable complete-data observation. Then the Expectation-Maximization (EM) criterion is directly utilized to iteratively maximize the expected value of the complete-data log likelihood under the posterior distribution of the latent variable. The novelties of the proposed method lie in its capability of interpolating the actual received data to a virtual uniform linear array, therefore extending the achievable array aperture. Simulation results manifests the superiority of the proposed method over off-the-shelf algorithms, specially on circumstances such as low SNR, insufficient snapshots, and spatially adjacent sources.  相似文献   
18.
19.
The rate of penetration (ROP) model is of great importance in achieving a high efficiency in the complex geological drilling process. In this paper, a novel two-level intelligent modeling method is proposed for the ROP considering the drilling characteristics of data incompleteness, couplings, and strong nonlinearities. Firstly, a piecewise cubic Hermite interpolation method is introduced to complete the lost drilling data. Then, a formation drillability (FD) fusion submodel is established by using Nadaboost extreme learning machine (Nadaboost-ELM) algorithm, and the mutual information method is used to obtain the parameters, strongly correlated with the ROP. Finally, a ROP submodel is established by a neural network with radial basis function optimized by the improved particle swarm optimization (RBFNN-IPSO). This two-level ROP model is applied to a real drilling process and the proposed method shows the best performance in ROP prediction as compared with conventional methods. The proposed ROP model provides the basis for intelligent optimization and control in the complex geological drilling process.  相似文献   
20.
This study aims to assess the degree of HACCP implementation in small business butcher shops and understand which factors most influence butchers' intention to fully implement it, through the application of the Theory of Planned Behaviour. One hundred and one butchers managing or owning small butcher's responded to the interview regarding their Attitudes, Subjective Norm, Perceived Behavioural Control, Personal Norm, and Knowledge with regard to their Intention to fully implement a HACCP system in their shops. Before the interviews, a certified veterinarian visited all the shops. Visits included an inspection of the establishments using the Official Portuguese Control Plan checklist for meat retailers. Conformance level measured past performance regarding food safety practices. Based on past performance, butchers were divided into “high performers” and “low performers”. “High performers” yielded high values of Attitude and Intention towards the Behaviour. For these, Attitude and Personal Norm emerge as predictors of the Intention to fully implement a HACCP system. For “low performers”, Personal Norm was the strongest predictor of Intention, with results pointing to the need for an intervention from the authorities to promote increased conformance to food safety practices. For both groups, neither Social Norm nor Perceived Behavioural Control acted as significant predictors of Intention.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号