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   9557篇
  免费   733篇
  国内免费   91篇
电工技术   185篇
综合类   41篇
化学工业   2622篇
金属工艺   213篇
机械仪表   396篇
建筑科学   358篇
矿业工程   20篇
能源动力   615篇
轻工业   911篇
水利工程   192篇
石油天然气   145篇
武器工业   5篇
无线电   992篇
一般工业技术   1641篇
冶金工业   226篇
原子能技术   67篇
自动化技术   1752篇
  2024年   40篇
  2023年   191篇
  2022年   347篇
  2021年   613篇
  2020年   556篇
  2019年   682篇
  2018年   778篇
  2017年   736篇
  2016年   726篇
  2015年   429篇
  2014年   717篇
  2013年   1038篇
  2012年   653篇
  2011年   735篇
  2010年   476篇
  2009年   405篇
  2008年   244篇
  2007年   184篇
  2006年   149篇
  2005年   102篇
  2004年   102篇
  2003年   61篇
  2002年   58篇
  2001年   28篇
  2000年   24篇
  1999年   28篇
  1998年   27篇
  1997年   25篇
  1996年   30篇
  1995年   21篇
  1994年   13篇
  1993年   17篇
  1992年   10篇
  1991年   17篇
  1990年   16篇
  1989年   13篇
  1988年   9篇
  1987年   10篇
  1986年   9篇
  1985年   9篇
  1984年   15篇
  1983年   12篇
  1982年   4篇
  1981年   3篇
  1980年   2篇
  1979年   6篇
  1978年   3篇
  1977年   2篇
  1976年   2篇
  1973年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Utility is an important factor for serviceproviders, and they try to increase their utilities through adopting different policies and strategies. Because of unpredictable failures in systems, there are many scenarios in which the failures may cause random losses for service providers. Loss sharing can decrease negative effects of unexpected random losses. Because of capabilities of learning automata in random and stochastic environments, in this paper, a new learning automaton based method is presented for loss sharing purpose. It is illustrated that the loss sharing can be useful for service providers and helps them to decrease negative effect of the random losses. The presented method can be used especially in collaborative environments such as federated clouds. Results of the conducted experiments show the usefulness of the presented approach to improve utility of service providers.  相似文献   
72.
Grid computing is emerging as the foundation upon which virtual organizations can be built. Such organizations are becoming of increasing importance for tackling various projects, both in academic and in business fields. This paper is concerned with presenting an integrated view of the grid to readers interested in understanding it, or perhaps in developing it further or making use of it in the future. The target view is based on the STOPE (strategy/technology/organization/people/environment) framework that has previously been used to integrate the issues of various information technology problems over its well‐defined domains. For strategy, the view considers the reasons associated with the need for the grid, including grid services and grid benefits. For technology, the technical components of the grid and their functions are taken into account. For organization, the organizations concerned with the development, technology production, service provisioning and use of the grid are considered. For people, those associated with the grid in the related organizations are taken into account. For the environment, rules, practices and support associated with the grid are discussed. Finally, the paper emphasizes questions that need to be answered in order to contribute to the future development of the grid. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
73.
International Journal of Wireless Information Networks - Dynamic variation of network topology in mobile ad hoc networks (MANET) forces network nodes to work together and rely on each other for...  相似文献   
74.

Wireless sensor network has special features and many applications, which have attracted attention of many scientists. High energy consumption of these networks, as a drawback, can be reduced by a hierarchical routing algorithm. The proposed algorithm is based on the Low Energy Adaptive Clustering Hierarchy (LEACH) and Quadrant Cluster based LEACH (Q-LEACH) protocols. To reduce energy consumption and provide a more appropriate coverage, the network was divided into several regions and clusters were formed within each region. In selecting the cluster head (CH) in each round, the amount of residual energy and the distance from the center of each node were calculated by the base station (including the location and residual energy of each node) for all living nodes in each region. In this regard, the node with the largest value had the highest priority to be selected as the CH in each network region. The base station calculates the CH due to the lack of energy constraints and is also responsible for informing it throughout the network, which reduces the load consumption and tasks of nodes in the network. The information transfer steps in this protocol are similar to the LEACH protocol stages. To better evaluate the results, the proposed method was implemented with LEACH LEACH-SWDN, and Q-LEACH protocols using MATLAB software. The results showed better performance of the proposed method in network lifetime, first node death time, and the last node death time.

  相似文献   
75.
Wireless sensor networks (WSNs) are known to be highly energy-constrained and  consequently lifetime is a critical metric in their design and implementation. Range assignment by adjusting the transmission powers of nodes create a energy-efficient topology for such networks while preserving other network issues, however, it may effect on the performance of other techniques such as network coding. This paper addresses the problem of lifetime optimization for WSNs where the network employs both range assignment and network-coding-based multicast. We formulate the problem and then reformulated it as convex optimization that offer a numerous theoretical or conceptual advantages. The proposed programming leads to efficient or distributed algorithms for solving the problem. Simulation results show that the proposed optimized mechanism decreases end-to-end delay and improve lifetime as compared by other conventional ones.  相似文献   
76.
Wireless Personal Communications - The position of mobile devices is determined by Real Time Differential Global Positioning System (RTDGPS). This system is composed of fixed and mobile station....  相似文献   
77.
ABSTRACT

Outdoor positioning systems based on the Global Navigation Satellite System have several shortcomings that have deemed their use for indoor positioning impractical. Location fingerprinting, which utilizes machine learning, has emerged as a viable method and solution for indoor positioning due to its simple concept and accurate performance. In the past, shallow learning algorithms were traditionally used in location fingerprinting. Recently, the research community started utilizing deep learning methods for fingerprinting after witnessing the great success and superiority these methods have over traditional/shallow machine learning algorithms. This paper provides a comprehensive review of deep learning methods in indoor positioning. First, the advantages and disadvantages of various fingerprint types for indoor positioning are discussed. The solutions proposed in the literature are then analyzed, categorized, and compared against various performance evaluation metrics. Since data is key in fingerprinting, a detailed review of publicly available indoor positioning datasets is presented. While incorporating deep learning into fingerprinting has resulted in significant improvements, doing so, has also introduced new challenges. These challenges along with the common implementation pitfalls are discussed. Finally, the paper is concluded with some remarks as well as future research trends.  相似文献   
78.
79.
Many applications, such as e-passport, e-health, credit cards, and personal devices that utilize Radio frequency Identification (RFID) devices for authentication require strict security and privacy. However, RFID tags suffer from some inherent weaknesses due to restricted hardware capabilities and are vulnerable to eavesdropping, interception, or modification. The synchronization and untraceability characteristics are the major determinants of RFID authentication protocols. They are strongly related to privacy of tags and availability, respectively. In this paper, we analyze a new lightweight RFID authentication protocol, Song and Mitchell, in terms of privacy and security. We prove that not only is the scheme vulnerable to desynchronization attack, but it suffers from traceability and backward traceability as well. Finally, our improved scheme is proposed which can prevent aforementioned attacks.  相似文献   
80.
Advanced forms of hydrogels have many inherently desirable properties and can be designed with different structures and functions. In particular, bioresponsive multifunctional hydrogels can carry out sophisticated biological functions. These include in situ single-cell approaches, capturing, analysis, and release of living cells, biomimetics of cell, tissue, and tumor-specific niches. They can allow in vivo cell manipulation and act as novel drug delivery systems, allowing diagnostic, therapeutic, vaccination, and immunotherapy methods. In the present review of multitasking hydrogels, new approaches and devices classified into point-of-care testing (POCT), microarrays, single-cell/rare cell approaches, artificial membranes, biomimetic modeling systems, nanodoctors, and microneedle patches are summarized. The potentials and application of each format are critically discussed, and some limitations are highlighted. Finally, how hydrogels can enable an “all-in-one platform” to play a key role in cancer therapy, regenerative medicine, and the treatment of inflammatory, degenerative, genetic, and metabolic diseases is being looked forward to.  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