全文获取类型
收费全文 | 3228篇 |
免费 | 205篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 40篇 |
化学工业 | 815篇 |
金属工艺 | 40篇 |
机械仪表 | 84篇 |
建筑科学 | 128篇 |
矿业工程 | 5篇 |
能源动力 | 114篇 |
轻工业 | 573篇 |
水利工程 | 29篇 |
石油天然气 | 19篇 |
无线电 | 204篇 |
一般工业技术 | 473篇 |
冶金工业 | 116篇 |
原子能技术 | 13篇 |
自动化技术 | 788篇 |
出版年
2024年 | 7篇 |
2023年 | 40篇 |
2022年 | 127篇 |
2021年 | 143篇 |
2020年 | 116篇 |
2019年 | 133篇 |
2018年 | 121篇 |
2017年 | 109篇 |
2016年 | 143篇 |
2015年 | 112篇 |
2014年 | 147篇 |
2013年 | 286篇 |
2012年 | 236篇 |
2011年 | 265篇 |
2010年 | 210篇 |
2009年 | 192篇 |
2008年 | 179篇 |
2007年 | 152篇 |
2006年 | 124篇 |
2005年 | 96篇 |
2004年 | 77篇 |
2003年 | 64篇 |
2002年 | 69篇 |
2001年 | 35篇 |
2000年 | 33篇 |
1999年 | 27篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 19篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1967年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有3441条查询结果,搜索用时 15 毫秒
991.
Davide Figo Pedro C. Diniz Diogo R. Ferreira João M. P. Cardoso 《Personal and Ubiquitous Computing》2010,14(7):645-662
The ubiquity of communication devices such as smartphones has led to the emergence of context-aware services that are able
to respond to specific user activities or contexts. These services allow communication providers to develop new, added-value
services for a wide range of applications such as social networking, elderly care and near-emergency early warning systems.
At the core of these services is the ability to detect specific physical settings or the context a user is in, using either
internal or external sensors. For example, using built-in accelerometers, it is possible to determine whether a user is walking
or running at a specific time of day. By correlating this knowledge with GPS data, it is possible to provide specific information
services to users with similar daily routines. This article presents a survey of the techniques for extracting this activity
information from raw accelerometer data. The techniques that can be implemented in mobile devices range from classical signal
processing techniques such as FFT to contemporary string-based methods. We present experimental results to compare and evaluate
the accuracy of the various techniques using real data sets collected from daily activities. 相似文献
992.
Rodríguez Erasmo Sánchez Inés Duque Nicolás Arboleda Pedro Vega Carolina Zamora David López Patricia Kaune Alexander Werner Micha García Camila Burke Sophia 《Water Resources Management》2020,34(7):2179-2199
Water Resources Management - Reanalysis and earth observation data have enormous potential to support water resources management, particularly in river basins where data availability is poor or... 相似文献
993.
Pedro Arsnio Patricia María Rodríguez‐Gonzlez Ivan Bernez Filipe S. Dias Miguel N. Bugalho Simon Dufour 《河流研究与利用》2020,36(6):907-920
Social‐ecological contexts are key to the success of ecological restoration projects. The ecological quality of restoration efforts, however, may not be fully evident to stakeholders, particularly if the desired aesthetic experience is not delivered. Aesthetically pleasing landscapes are more highly appreciated and tend to be better protected than less appealing landscapes, regardless of their ecological value. Positive public perception of restoration actions may therefore facilitate stakeholder involvement and catalyse recognition of ecological improvement. Here we aim to contrast aesthetical perception and ecological condition in headwater river reaches restored through passive ecological restoration in study areas in Portugal (Alentejo) and France (Normandy). We recorded structural and functional indicators of riparian vegetation to monitor the ecological condition of study sites along a passive restoration trajectory. Aesthetical perception indicators were assessed through stakeholder inquiries developed under a semantic differential approach. We analysed perception responses to changes in the riparian ecosystems resulting from passive ecological restoration across different geographical contexts and social groups. The analysed social groups comprised stakeholders (environmental managers and landowners) and university students (landscape architecture and geography students). Results indicate that (a) visual preferences often do not reflect changes in ecological condition, (b) perception of the restoration process is strongly context dependent, and (c) experience and cultural background affect perception of ecological condition across the different social groups analysed. Clear identification of relevant stakeholder groups (those interested in or directly affected by restoration), effective communication, and stakeholder engagement are therefore essential for assuring the success of river restoration projects. 相似文献
994.
Stability of gaseous samples is a major concern when dealing with odours and airborne pollutants sampling. In terms of odours, the representativeness of the sample can be very seriously compromised, despite the rigorous application of the maximum storage time established by EN-13725. The present paper is focused on the use of the cryo-condensation technique (Cryocore) for time-weighted-average (TWA) sampling in waste water treatment plants (WWTPs), with the aim of comparing the values of TWA odour and H(2)S concentration when using the Cryocore system and other well established sampling methods, such as those described in EN-13725 and passive sampling. The study showed comparable results when comparing all the methodologies tested. 相似文献
995.
996.
Pedro Lara Fábio Borges Renato Portugal Nadia Nedjah 《Journal of Computer and System Sciences》2012,78(2):575-582
The modular exponentiation operation of the current algorithms for asymmetric cryptography is the most expensive part in terms of computational cost. The RSA algorithm, for example, uses the modular exponentiation algorithm in encryption and decryption procedure. Thus, the overall performance of those asymmetric cryptosystems depends heavily on the performance of the specific algorithm used for modular exponentiation. This work proposes new parallel algorithms to perform this arithmetical operation and determines the optimal number of processors that yields the greatest speedup. The optimal number is obtained by balancing the processing load evenly among the processors. Practical implementations are also performed to evaluate the theoretical proposals. 相似文献
997.
The phenomenon of birefringence may be observed when light arrives at an anisotropic crystal surface and refracts through
it, causing the incident light ray to split into two rays; these become polarized in mutually orthogonal directions, and two
images are formed. The principal goal of this paper is the study of the directional issues involved in the behavior of light
when refracting through a homogeneous, non-participating medium, including both isotropic and anisotropic media (uniaxial
and, for the first time, biaxial). The paper focuses on formulating and solving the non-linear algebraic system that is obtained
when the refraction process is simulated using the geometric model of Huygens. The main contribution focuses on the case of
biaxial media. In the case of uniaxial media, we rely on symbolic calculus techniques to formulate and solve the problem. 相似文献
998.
999.
This paper proposes a new method to perform real-time face pose estimation for ± 90° yaw rotations and under low light conditions. The algorithm works on the basis of a completely automatic and run-time incremental 3D face modelling. The model is initially made up upon a set of 3D points derived from stereo grey-scale images. As new areas of the subject face appear to the cameras, new 3D points are automatically added to complete the model. In this way, we can estimate the pose for a wide range of rotation angles, where typically 3D frontal points are occluded. 相似文献
1000.
Pilar Manzanares-Lopez Josemaria Malgosa-Sanahuja Juan Pedro Muñoz-Gea 《Journal of Parallel and Distributed Computing》2012
In peer-to-peer (P2P) networks, trust management is a key tool to minimize the impact of malicious nodes. EigenTrust is claimed to be one of the most powerful distributed reputation management systems focused on P2P file-sharing applications. It is the theoretical base of other systems, and it has also been directly modified in an attempt to improve its performance. However, none of them give appropriate importance to all the information about transactions. This paper proposes an enhancement of EigenTrust, which considers unsatisfactory transactions in greater depth. Pos&Neg EigenTrust is able to obtain a blacklist of the identities of the malicious nodes. Therefore, it is able to significantly reduce the number of unsatisfactory transactions in the network. 相似文献