全文获取类型
收费全文 | 32039篇 |
免费 | 5479篇 |
国内免费 | 4213篇 |
专业分类
电工技术 | 6027篇 |
技术理论 | 4篇 |
综合类 | 4456篇 |
化学工业 | 1051篇 |
金属工艺 | 539篇 |
机械仪表 | 2145篇 |
建筑科学 | 2282篇 |
矿业工程 | 604篇 |
能源动力 | 994篇 |
轻工业 | 695篇 |
水利工程 | 477篇 |
石油天然气 | 610篇 |
武器工业 | 554篇 |
无线电 | 5255篇 |
一般工业技术 | 2318篇 |
冶金工业 | 753篇 |
原子能技术 | 93篇 |
自动化技术 | 12874篇 |
出版年
2024年 | 349篇 |
2023年 | 832篇 |
2022年 | 1188篇 |
2021年 | 1361篇 |
2020年 | 1530篇 |
2019年 | 1292篇 |
2018年 | 1190篇 |
2017年 | 1419篇 |
2016年 | 1478篇 |
2015年 | 1678篇 |
2014年 | 2471篇 |
2013年 | 2360篇 |
2012年 | 2615篇 |
2011年 | 2724篇 |
2010年 | 2140篇 |
2009年 | 2094篇 |
2008年 | 2085篇 |
2007年 | 2166篇 |
2006年 | 2009篇 |
2005年 | 1637篇 |
2004年 | 1352篇 |
2003年 | 1134篇 |
2002年 | 864篇 |
2001年 | 752篇 |
2000年 | 632篇 |
1999年 | 442篇 |
1998年 | 365篇 |
1997年 | 294篇 |
1996年 | 259篇 |
1995年 | 210篇 |
1994年 | 158篇 |
1993年 | 139篇 |
1992年 | 124篇 |
1991年 | 81篇 |
1990年 | 77篇 |
1989年 | 57篇 |
1988年 | 38篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1962年 | 3篇 |
1960年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
该文首先介绍了三相并联型有源电力滤波器的主电路和工作原理,然后分析了基于瞬时无功功率理论的ip—iq电流检测算法并对比研究了滞环比较和三角载波比较两种控制策略,据此建立了仿真模型并进行仿真研究。仿真结果和仿真试验波形验证了该方法的准确性和有效性。 相似文献
992.
Automatic human face detection from video sequences is an important component of intelligent human computer interaction systems for video surveillance, face recognition, emotion recognition and face database management. This paper proposes an automatic and robust method to detect human faces from video sequences that combines feature extraction and face detection based on local normalization, Gabor wavelets transform and Adaboost algorithm. The key step and the main contribution of this work is the incorporation of a normalization technique based on local histograms with optimal adaptive correlation (OAC) technique to alleviate a common problem in conventional face detection methods: inconsistent performance due to sensitivity to variation illuminations such as local shadowing, noise and occlusion. The approach uses a cascade of classifiers to adopt a coarse-to-fine strategy for achieving higher detection rates with lower false positives. The experimental results demonstrate a significant performance improvement gains and achieved by local normalization over methods without normalizations in real video sequences with a wide range of facial variations in color, position, scale, and varying lighting conditions. 相似文献
993.
Tong-Hua Su Author Vitae Tian-Wen Zhang Author Vitae Hu-Jie Huang 《Pattern recognition》2009,42(1):167-182
Great challenges are faced in the off-line recognition of realistic Chinese handwriting. This paper presents a segmentation-free strategy based on Hidden Markov Model (HMM) to handle this problem, where character segmentation stage is avoided prior to recognition. Handwritten textlines are first converted to observation sequence by sliding windows. Then embedded Baum-Welch algorithm is adopted to train character HMMs. Finally, best character string maximizing the a posteriori is located through Viterbi algorithm. Experiments are conducted on the HIT-MW database written by more than 780 writers. The results show the feasibility of such systems and reveal apparent complementary capacities between the segmentation-free systems and the segmentation-based ones. 相似文献
994.
Combining reduced technique with iterative strategy, we propose a recursive reduced least squares support vector regression. The proposed algorithm chooses the data which make more contribution to target function as support vectors, and it considers all the constraints generated by the whole training set. Thus it acquires less support vectors, the number of which can be arbitrarily predefined, to construct the model with the similar generalization performance. In comparison with other methods, our algorithm also gains excellent parsimoniousness. Numerical experiments on benchmark data sets confirm the validity and feasibility of the presented algorithm. In addition, this algorithm can be extended to classification. 相似文献
995.
K. Geihs P. Barone F. Eliassen J. Floch R. Fricke E. Gjorven S. Hallsteinsen G. Horn M. U. Khan A. Mamelli G. A. Papadopoulos N. Paspallis R. Reichle E. Stav 《Software》2009,39(4):385-422
Driven by the emergence of mobile and pervasive computing there is a growing demand for context‐aware software systems that can dynamically adapt to their run‐time environment. We present the results of project MADAM that has delivered a comprehensive solution for the development and operation of context‐aware, self‐adaptive applications. The main contributions of MADAM are (a) a sophisticated middleware that supports the dynamic adaptation of component‐based applications, and (b) an innovative model‐driven development methodology that is based on abstract adaptation models and corresponding model‐to‐code transformations. MADAM has demonstrated the viability of a general, integrated approach to application‐level adaptation. We discuss our experiences with two real‐world case studies that were built using the MADAM approach. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
996.
Juan Wang Author Vitae Dan Feng Author VitaeAuthor Vitae Chengtao Lu Author Vitae 《Journal of Systems and Software》2009,82(12):2004-2011
This paper proposes a novel distributed metadata management strategy to efficiently handle different metadata workloads. It can deliver high performance and scalable metadata service through four techniques, including directory conversion metadata, mimic hierarchical directory structure, flexible partition methods targeted different kinds of metadata of diverse characteristics, and the application of database to metadata backend. Using micro-benchmarks and a prototype system, we firstly demonstrate the performance superiority of our strategy compared to Lazy Hybrid, and then present the detailed performance results and analysis of our strategy on different MDS scales. 相似文献
997.
An adaptive hybrid model (AHM) based on nondominated solutions is presented in this study for multi-objective optimization problems (MOPs). In this model, three search phases are devised according to the number of nondominated solutions in the current population: 1) emphasizing the dominated solutions when the population contains very few nondominated solutions; 2) maintaining the balance between nondominated and dominated solutions when nondominated ones become more; 3) when the population consists of adequate nondominated solutions, dominated ones could be ignored and the isolated nondominated ones are allocated more computational budget by their crowding distance values for heuristic search. To exploit local information efficiently, a local incremental search algorithm, LISA, is proposed and merged into the model. This model maintains the adaptive mechanism between the optimization process by the online discovered nondominated solutions. The proposed model is validated using five ZDT and five DTLZ problems. Compared with three other state-of-the-art multi-objective algorithms, namely NSGA-II, SPEA2, and PESA-II, AHM achieves comparable results in terms of convergence and diversity metrics. Finally, the sensitivity of introduced parameters and scalability to the number of objectives are investigated. 相似文献
998.
General Adaptive Neighborhood Choquet Image Filtering 总被引:1,自引:0,他引:1
A novel framework entitled General Adaptive Neighborhood Image Processing (GANIP) has been recently introduced in order to
propose an original image representation and mathematical structure for adaptive image processing and analysis. The central
idea is based on the key notion of adaptivity which is simultaneously associated with the analyzing scales, the spatial structures
and the intensity values of the image to be addressed. In this paper, the GANIP framework is briefly exposed and particularly
studied in the context of Choquet filtering (using fuzzy measures), which generalizes a large class of image filters. The
resulting spatially-adaptive operators are studied with respect to the general GANIP framework and illustrated in both the
biomedical and materials application areas. In addition, the proposed GAN-based filters are practically applied and compared
to several other denoising methods through experiments on image restoration, showing a high performance of the GAN-based Choquet
filters.
相似文献
Jean-Charles PinoliEmail: |
999.
Holding strategies are among the most commonly used operation control strategies in transit systems. In this paper, a dynamic
holding strategy is developed, which consists of two major steps: (1) judging whether an early bus should be held, and (2) optimizing
the holding times of the held bus. A model based on support vector machine (SVM), which contains four input variables (time-of-day,
segment, the latest speed on the next segment, and the bus speed on the current segment) for forecasting the early bus departure
times from the next stop is also developed. Then, in order to determine the optimal holding times, a model aiming to minimize
the user costs is constructed and a genetic algorithm is used to optimize the holding times. Finally, the dynamic holding
strategy proposed in this study is illustrated with the microscopic simulation model Paramics and some conclusions are drawn.
相似文献
Bin YuEmail: |
1000.
Fault based testing aims at detecting hypothesized faults based on specifications or program source. There are some fault
based techniques for testing Boolean expressions which are commonly used to model conditions in specifications as well as
logical decisions in program source. The MUMCUT strategy has been proposed to generate test cases from Boolean expressions.
Moreover, it detects eight common types of hypothesized faults provided that the original expression is in irredundant disjunctive
normal form, IDNF. Software practitioners are more likely to write the conditions and logical decisions in general form rather
than IDNF. Hence, it is interesting to investigate the fault detecting capability of the MUMCUT strategy with respect to general
form Boolean expressions. In this article, we perform empirical studies to investigate the fault detection capability of the
MUMCUT strategy with respect to general form Boolean expressions as well as mutated expressions. A mutated expression can
be obtained from the original given Boolean expression by making a syntactic change based on a particular type of fault.
T. Y. Chen obtained his BSc and MPhil from the University of Hong Kong, MSc and DIC from the Imperial College of Science and Technology, PhD from the University of Melbourne. He is currently a Professor of Software Engineering at the Swinburne University of Technology. Prior to joining Swinburne, he has taught at the University of Hong Kong and the University of Melbourne. His research interests include software testing, debugging, maintenance, and validation of requirements. M. F. Lau received the Ph.D. degree in Software Engineering from the University of Melbourne, Australia. He is currently a Senior Lecturer in the Faculty of Information and Communication Technologies, Swinburne University of Technology, Australia. His research publications have appeared in various scholarly journals, including ACM Transactions on Software Engineering and Methodology, The Journal of Systems and Software, The Computer Journal, Software Testing, Verification and Reliability, Information and Software Technology, Information Sciences, and Information Processing Letters. His research interests include software testing, software quality, software specification and computers in education. K. Y. Sim received his Bachelor of Engineering in Electrical, Electronics and Systems from the National University of Malaysia in 1999 and the Master of Computer Science from the University of Malaya, Malaysia in 2001. Currently, he is a Senior Lecturer in the School of Engineering, Swinburne University of Technology, Sarawak Campus, Malaysia. His current research interests include software testing and information security. C. A. Sun received the PhD degree in Computer Software and Theory in 2002 from Beijing University of Aeronautics and Astronautics, China; the bachelor degree in Computer and Its application in 1997 from University of Science and Technology Beijing, China. He is currently an Assistant Professor in the School of Computer and Information Technology, Beijing Jiaotong University, China. His research areas are software testing, software architecture and service-oriented computing. He has published about 40 referred papers in the above areas. He is an IEEE member. 相似文献
M. F. LauEmail: |
T. Y. Chen obtained his BSc and MPhil from the University of Hong Kong, MSc and DIC from the Imperial College of Science and Technology, PhD from the University of Melbourne. He is currently a Professor of Software Engineering at the Swinburne University of Technology. Prior to joining Swinburne, he has taught at the University of Hong Kong and the University of Melbourne. His research interests include software testing, debugging, maintenance, and validation of requirements. M. F. Lau received the Ph.D. degree in Software Engineering from the University of Melbourne, Australia. He is currently a Senior Lecturer in the Faculty of Information and Communication Technologies, Swinburne University of Technology, Australia. His research publications have appeared in various scholarly journals, including ACM Transactions on Software Engineering and Methodology, The Journal of Systems and Software, The Computer Journal, Software Testing, Verification and Reliability, Information and Software Technology, Information Sciences, and Information Processing Letters. His research interests include software testing, software quality, software specification and computers in education. K. Y. Sim received his Bachelor of Engineering in Electrical, Electronics and Systems from the National University of Malaysia in 1999 and the Master of Computer Science from the University of Malaya, Malaysia in 2001. Currently, he is a Senior Lecturer in the School of Engineering, Swinburne University of Technology, Sarawak Campus, Malaysia. His current research interests include software testing and information security. C. A. Sun received the PhD degree in Computer Software and Theory in 2002 from Beijing University of Aeronautics and Astronautics, China; the bachelor degree in Computer and Its application in 1997 from University of Science and Technology Beijing, China. He is currently an Assistant Professor in the School of Computer and Information Technology, Beijing Jiaotong University, China. His research areas are software testing, software architecture and service-oriented computing. He has published about 40 referred papers in the above areas. He is an IEEE member. 相似文献