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   743篇
  免费   34篇
  国内免费   5篇
电工技术   13篇
综合类   2篇
化学工业   173篇
金属工艺   22篇
机械仪表   21篇
建筑科学   19篇
矿业工程   1篇
能源动力   36篇
轻工业   32篇
水利工程   18篇
石油天然气   10篇
无线电   79篇
一般工业技术   121篇
冶金工业   32篇
原子能技术   4篇
自动化技术   199篇
  2024年   4篇
  2023年   27篇
  2022年   50篇
  2021年   67篇
  2020年   59篇
  2019年   60篇
  2018年   64篇
  2017年   55篇
  2016年   53篇
  2015年   20篇
  2014年   52篇
  2013年   58篇
  2012年   41篇
  2011年   52篇
  2010年   26篇
  2009年   14篇
  2008年   15篇
  2007年   10篇
  2006年   8篇
  2005年   1篇
  2004年   6篇
  2003年   1篇
  2002年   2篇
  2000年   1篇
  1999年   3篇
  1998年   8篇
  1997年   6篇
  1996年   3篇
  1993年   2篇
  1992年   1篇
  1991年   5篇
  1990年   3篇
  1987年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1975年   1篇
排序方式: 共有782条查询结果,搜索用时 15 毫秒
91.
The exponential growth in the volume of digital image databases is making it increasingly difficult to retrieve relevant information from them. Efficient retrieval systems require distinctive features extracted from visually rich contents, represented semantically in a human perception-oriented manner. This paper presents an efficient framework to model image contents as an undirected attributed relational graph, exploiting color, texture, layout, and saliency information. The proposed method encodes salient features into this rich representative model without requiring any segmentation or clustering procedures, reducing the computational complexity. In addition, an efficient graph-matching procedure implemented on specialized hardware makes it more suitable for real-time retrieval applications. The proposed framework has been tested on three publicly available datasets, and the results prove its superiority in terms of both effectiveness and efficiency in comparison with other state-of-the-art schemes.  相似文献   
92.
Capability of microstrip nonuniform transmission lines (MNTLs) for construction of dual‐band and broadband unequal Wilkinson power dividers with arbitrary‐way, arbitrary frequency band operations, and arbitrary power divisions is evaluated. Also, the MNTL transformers are introduced for dual‐band/broadband matching of the unequal output impedances of the MNTL power divider with arbitrary output terminal impedances. The strip width of MNTLs is considered variable and is written as a truncated Fourier series expansion. To show the validity of the design procedure, three experimental MNTL Wilkinson power dividers, which are dual‐band two‐ and three‐way power dividers with different power divisions working at 1 and 3.4 GHz and one broadband equal power divider working from 0.4 to 1.8 GHz, have been designed and fabricated. In the first ones with power division of 1.5, outputs isolation and ports matching of less than ?30 dB are achieved. Next, an extended recombinant structure is presented for achieving three‐way MNTL power dividers with dual‐band operation. The measured isolation between outputs and ports matching are better than 30 dB and measured forward transmissions are between ?4.87 and ?5.45 in two passbands of the divider. Also, for the proposed broadband divider, the measured isolation between the outputs is better than 13 dB in 127% desired bandwidth. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.  相似文献   
93.
To improve the resource limitation of mobile devices, mobile users may utilize cloud-computational and storage services. Although the utilization of the cloud services improves the processing and storage capacity of mobile devices, the migration of confidential information on untrusted cloud raises security and privacy issues. Considering the security of mobile-cloud-computing subscribers’ information, a mechanism to authenticate legitimate mobile users in the cloud environment is sought. Usually, the mobile users are authenticated in the cloud environment through digital credential methods, such as password. Once the users’ credential information theft occurs, the adversary can use the hacked information for impersonating the mobile user later on. The alarming situation is that the mobile user is unaware about adversary’s malicious activities. In this paper, a light-weight security scheme is proposed for mobile user in cloud environment to protect the mobile user’s identity with dynamic credentials. The proposed scheme offloads the frequently occurring dynamic credential generation operations on a trusted entity to keep minimum processing burden on the mobile device. To enhance the security and reliability of the scheme, the credential information is updated frequently on the basis of mobile-cloud packets exchange. Furthermore, the proposed scheme is compared with the existing scheme on the basis of performance metrics i.e. turnaround time and energy consumption. The experimental results for the proposed scheme showed significant improvement in turnaround time and energy consumption as compared to the existing scheme.  相似文献   
94.
In the present paper, the dynamic facilities layout problem is studied in presence of ambiguity of information flow. Product demand (and consequently material flow) is defined as fuzzy numbers with different membership functions. The problem is modeled in fuzzy programming. Three models of expected value, chance-constrained programming and dependent-chance programming and two hybrid intelligent algorithms are then presented. At the end, efficiency of algorithms for solving fuzzy models of dynamic facilities layout is shown through some numerical examples.  相似文献   
95.
96.
A 10-cell Mk 9 stack was characterized using current/voltage mapping during automotive drive cycle testing. A minimally invasive current mapping technique was used to determine localized polarization curves which together with open circuit voltage (OCV) profile measurements provide useful information about crossover leak formation and location. Through a systematic variation of reactant gas pressures it is further possible to distinguish between electrical shorts, diffusive and convective leaks.  相似文献   
97.
The Journal of Supercomputing - The cloud of things (CloudIoT) represents a general system of supporting infrastructure for storing and processing information gathered from smart objects and their...  相似文献   
98.
The present work is designed to discover new perovskite-based materials, which are expected to show high mechanical stability during their applications, using machine learning (ML) techniques, and based on the Pugh's criterion for distinguishing brittle and ductile behaviors. For this purpose, ML models to predict the moduli of materials, bulk (B) and shear (G), are built using their crystal structure and composition information. The ML process is initiated with the information of 5663 compounds, including composition, crystal structure and moduli, as listed in AFLOW database. Following a procedure of data characteristics, feature generation, feature processing, training, and testing, the ML models are constructed with acceptable accuracy (tenfold cross-validation R2 score of 0.90 and 0.89 for B and G, respectively). The validation process of the models, which is conducted using the corresponding density functional theory calculations, reveals that these models are reliable to be employed in a large-scale screening process. Indeed, the B- and G-based ML models are incorporated in a screening process, and this is also conjugated with other screening criterions, to find out thermodynamically stable and formable perovskite-based materials with improved mechanical performance.  相似文献   
99.
Among various speech enhancement methods, two-microphone noise reduction systems are utilized for their low cost implementation and acceptable performance. Coherence-based methods are well known as efficient two-microphone noise reduction techniques. These techniques, however, do not work well when the received noise signals are correlated. Coherence-based methods can be improved when the cross power spectral density (CPSD) of input noises is available. In this paper, we propose a new method for estimating noise CPSD based on the assumption of a diffuse noise field. With this assumption, we estimate the noise CPSD using phase information. Then, the estimated noise CPSD is used to calculate a coherence-based gain filter which is then employed to enhance noisy signals. We compare the proposed phase-based noise CPSD estimation with a noise CPSD estimation technique based on a voice activity detector (VAD), both of which are herein separately employed in a two-microphone speech enhancement configuration. The comparison shows that the two-microphone speech enhancement scheme utilizing the proposed noise CPSD estimation technique outperforms the enhancement system using the VAD-based noise CPSD estimation.  相似文献   
100.
Concentric braced frames are commonly used in steel structures to withstand lateral forces. However, brace hysteretic behavior is asymmetric in tension and compression. These frames typically exhibit substantial strength deterioration when loaded in compression. Consequently, the concept of Buckling Restrained Brace (BRB) has been introduced to overcome this deficiency.The length of a BRB steel core could have a significant effect on its overall behavior since it directly influences the energy dissipation of the member. Furthermore, BRB could be effectively utilized as a damper to dissipate seismic input energy, particularly when used as a fuse within the brace in a frame. Modified BRBs with shorter lengths may be called damper BRBs, because they function as if a typical damper is utilized along any brace member. These damper BRBs are fabricated and tested in this study both experimentally and analytically. Useful insights into local retrofitting of core plates and connections are also provided.  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