全文获取类型
收费全文 | 273152篇 |
免费 | 21481篇 |
国内免费 | 14085篇 |
专业分类
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 |
出版年
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
14.
Salman M.A. Salman 《国际水资源开发杂志》2015,31(1):4-16
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.
《Food Control》2015
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