全文获取类型
收费全文 | 4531篇 |
免费 | 314篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 80篇 |
综合类 | 14篇 |
化学工业 | 1361篇 |
金属工艺 | 142篇 |
机械仪表 | 204篇 |
建筑科学 | 169篇 |
矿业工程 | 16篇 |
能源动力 | 271篇 |
轻工业 | 436篇 |
水利工程 | 74篇 |
石油天然气 | 51篇 |
无线电 | 445篇 |
一般工业技术 | 706篇 |
冶金工业 | 142篇 |
原子能技术 | 34篇 |
自动化技术 | 741篇 |
出版年
2024年 | 15篇 |
2023年 | 85篇 |
2022年 | 140篇 |
2021年 | 310篇 |
2020年 | 245篇 |
2019年 | 323篇 |
2018年 | 390篇 |
2017年 | 343篇 |
2016年 | 337篇 |
2015年 | 191篇 |
2014年 | 345篇 |
2013年 | 485篇 |
2012年 | 323篇 |
2011年 | 336篇 |
2010年 | 250篇 |
2009年 | 186篇 |
2008年 | 112篇 |
2007年 | 59篇 |
2006年 | 60篇 |
2005年 | 41篇 |
2004年 | 39篇 |
2003年 | 31篇 |
2002年 | 26篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 11篇 |
1998年 | 22篇 |
1997年 | 8篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
排序方式: 共有4886条查询结果,搜索用时 0 毫秒
51.
Jafar Biazar Behzad Ghanbari Mehdi Gholami Porshokouhi Mohammad Gholami Porshokouhi 《Computers & Mathematics with Applications》2011,61(4):1016-1023
In this paper, He’s homotopy perturbation method is applied to solve non-linear systems of mixed Volterra–Fredholm integral equations. Two examples are presented to illustrate the ability of the method. Also comparisons are made between the Adomian decomposition method and the homotopy perturbation method. The results reveal that He’s homotopy perturbation method is very effective and simple and in these examples leads to the exact solutions. 相似文献
52.
We investigate the one-dimensional variable-sized bin-packing problem. This problem requires packing a set of items into a minimum-cost set of bins of unequal sizes and costs. Six optimization-based heuristics for this problem are presented and compared. We analyze their empirical performance on a large set of randomly generated test instances with up to 2000 items and seven bin types. The first contribution of this paper is to provide evidence that a set covering heuristic proves to be highly effective and capable of delivering very-high quality solutions within short CPU times. In addition, we found that a simple subset-sum problem-based heuristic consistently outperforms heuristics from the literature while requiring extremely short CPU times. 相似文献
53.
In this paper, we present a topology control algorithm for ad hoc networks. By considering the weight of the links, each node orders its one-hop neighbors in an ordered list and then the ordered lists are exchanged between the neighbors. This information enables the nodes to compute their transmission radius on the basis of its one- and two-hop neighbors’ information. We demonstrate that compared to the best known algorithms, the degree and transmission radius of the nodes in the topology produced by the proposed algorithm are smaller. In addition to Euclidean graphs, the algorithm works correctly on general weighted graphs. Also an extension of our algorithm is proposed which adapts its topology to network changes. Finally, we use the four metrics, node degree, transmission radius, the power stretch factor and, packet loss ratio to measure the performance improvements of the presented algorithms through simulations. 相似文献
54.
Shahla Nemati Mohammad Ehsan Basiri Nasser Ghasem-Aghaee Mehdi Hosseinzadeh Aghdam 《Expert systems with applications》2009,36(10):12086-12094
Protein function prediction is an important problem in functional genomics. Typically, protein sequences are represented by feature vectors. A major problem of protein datasets that increase the complexity of classification models is their large number of features. Feature selection (FS) techniques are used to deal with this high dimensional space of features. In this paper, we propose a novel feature selection algorithm that combines genetic algorithms (GA) and ant colony optimization (ACO) for faster and better search capability. The hybrid algorithm makes use of advantages of both ACO and GA methods. Proposed algorithm is easily implemented and because of use of a simple classifier in that, its computational complexity is very low. The performance of proposed algorithm is compared to the performance of two prominent population-based algorithms, ACO and genetic algorithms. Experimentation is carried out using two challenging biological datasets, involving the hierarchical functional classification of GPCRs and enzymes. The criteria used for comparison are maximizing predictive accuracy, and finding the smallest subset of features. The results of experiments indicate the superiority of proposed algorithm. 相似文献
55.
Building extraction from high-resolution satellite images (HRSI) in urban areas is an intricate problem. Recent studies proposed different methods during 2005–2015. However, in HRSI, they have not investigated the effects of challenges altogether. This paper studies the effects of non-building features which are the main drawbacks in building extraction. To overcome each challenge, it reviews recent strategies between 2005 and 2015. The pros and cons of each strategy are discussed, and proper strategies are combined to generate hybrid methods. Lower cost and fewer strategies are efficient attributes to recognize the best hybrid methods. Hybrid methods can be useful for different case studies in the future. 相似文献
56.
Handling objects with robotic soft fingers without considering the odds of slippage are not realistic. Grasping and manipulation algorithms have to be tested under such conditions for evaluating their robustness. In this paper, a dynamic analysis of rigid object manipulation with slippage control is studied using a two-link finger with soft hemispherical tip. Dependency on contact forces applied by a soft finger while grasping a rigid object is examined experimentally. A power-law model combined with a linear viscous damper is used to model the elastic behavior and damping effect of the soft tip, respectively. In order to obtain precise dynamic equations governing the system, two second-order differential equations with variable coefficients have been designed to describe the different possible states of the contact forces accordingly. A controller is designed based on the rigid fingertip model using the concept of feedback linearization for each phase of the system dynamics. Numerical simulations are used to evaluate the performance of the controller. The results reveal that the designed controller shows acceptable performance for both soft and rigid finger manipulation in reducing and canceling slippage. Furthermore, simulations indicate that the applied force in the soft finger manipulation is considerably less than the rigid “one.”. 相似文献
57.
Seyedali Mirjalili Seyed Mohammad Mirjalili Abdolreza Hatamlou 《Neural computing & applications》2016,27(2):495-513
This paper proposes a novel nature-inspired algorithm called Multi-Verse Optimizer (MVO). The main inspirations of this algorithm are based on three concepts in cosmology: white hole, black hole, and wormhole. The mathematical models of these three concepts are developed to perform exploration, exploitation, and local search, respectively. The MVO algorithm is first benchmarked on 19 challenging test problems. It is then applied to five real engineering problems to further confirm its performance. To validate the results, MVO is compared with four well-known algorithms: Grey Wolf Optimizer, Particle Swarm Optimization, Genetic Algorithm, and Gravitational Search Algorithm. The results prove that the proposed algorithm is able to provide very competitive results and outperforms the best algorithms in the literature on the majority of the test beds. The results of the real case studies also demonstrate the potential of MVO in solving real problems with unknown search spaces. Note that the source codes of the proposed MVO algorithm are publicly available at http://www.alimirjalili.com/MVO.html. 相似文献
58.
In this work, we present a scheme which is based on non-staggered grids. This scheme is a new family of non-staggered central schemes for hyperbolic conservation laws. Motivation of this work is a staggered central scheme recently introduced by A.A.I. Peer et al. [A new fourth-order non-oscillatory central scheme for hyperbolic conservation laws, Appl. Numer. Math. 58 (2008) 674–688]. The most important properties of the technique developed in the current paper are simplicity, high-resolution and avoiding the use of staggered grids and hence is simpler to implement in frameworks which involve complex geometries and boundary conditions. Numerical implementation of the new scheme is carried out on the scalar conservation laws with linear, non-linear flux and systems of hyperbolic conservation laws. The numerical results confirm the expected accuracy and high-resolution properties of the scheme. 相似文献
59.
Mehdi Ghatee 《Computer Communications》2011,34(7):835-846
This paper treats with integral multi-commodity flow through a network. To enhance the Quality of Service (QoS) for channels, it is necessary to minimize delay and congestion. Decreasing the end-to-end delay and consumption of bandwidth across channels are dependent and may be considered in very complex mathematical equations. To capture with this problem, a multi-commodity flow model is introduced whose targets are minimizing delay and congestion in one model. The flow through the network such as packets, also needs to get integral values. A model covering these concepts, is NP-hard while it is very important to find transmission strategies in real-time. For this aim, we extend a cooperative algorithm including traditional mathematical programming such as path enumeration and a meta-heuristic algorithm such as genetic algorithm. To find integral solution satisfying demands of nodes, we generalize a hybrid genetic algorithm to assign the integral commodities where they are needed. In this hybrid algorithm, we use feasible encoding and try to keep feasibility of chromosomes over iterations. By considering some random networks, we show that the proposed algorithm yields reasonable results in a few number of iterations. Also, because this algorithm can be applied in a wide range of objective functions in terms of delay and congestion, it is possible to find some routs for each commodity with high QoS. Due to these outcomes, the presented model and algorithm can be utilized in a variety of application in computer networks and transportation systems to decrease the congestion and increase the usage of channels. 相似文献
60.
The Optimal Sequenced Route (OSR) query strives to find a route of minimum length starting from a given source location and passing through a number of typed locations in a specific sequence imposed on the types of the locations. In this paper, we propose a pre-computation approach
to OSR query in both vector and metric spaces. We exploit the geometric properties of the solution space and theoretically
prove its relation to additively weighted Voronoi diagrams. Our approach recursively accesses these diagrams to incrementally build the OSR. Introducing the analogous diagrams for
the space of road networks, we show that our approach is also efficiently applicable to this metric space. Our experimental
results verify that our pre-computation approach outperforms the previous index-based approaches in terms of query response
time.
This research has been funded in part by NSF grants EEC-9529152 (IMSC ERC), IIS-0238560 (PECASE), IIS-0324955 (ITR), IIS-0534761,
and unrestricted cash gifts from Google and Microsoft. Any opinions, findings, and conclusions or recommendations expressed
in this material are those of the author(s) and do not necessarily reflect the views of the NSF.
Mehdi Sharifzadeh received his B.S. and M.S. degrees in Computer Engineering from Sharif University of Technology in Tehran, Iran, in 1995, and 1998, respectively. He received his Ph.D. degree in Computer Science from the University of Southern California in May 2007. His research interests include spatial and spatio-temporal databases, data stream processing, and sensor networks. Cyrus Shahabi is currently an Associate Professor and the Director of the Information Laboratory (InfoLAB) at the Computer Science Department and also a Research Area Director at the NSF’s Integrated Media Systems Center at the University of Southern California. He received his B.S. in Computer Engineering from Sharif University of Technology in 1989 and then his M.S. and Ph.D. degrees in Computer Science from the University of Southern California in May 1993 and August 1996, respectively. He has two books and more than hundred articles, book chapters, and conference papers in the areas of databases, GIS and multimedia. Dr. Shahabi’s current research interests include Geospatial and Multidimensional Data Analysis, Peer-to-Peer Systems and Streaming Architectures. He is currently an associate editor of the IEEE Transactions on Parallel and Distributed Systems and on the editorial board of ACM Computers in Entertainment magazine. He is also a member of the steering committees of IEEE NetDB and general co-chair of ACM GIS 2007. He serves on many conference program committees such as ACM SIGKDD 2006-08, IEEE ICDE 2006 and 08, SSTD 2005-08 and ACM SIGMOD 2004. Dr. Shahabi is the recipient of the 2002 NSF CAREER Award and 2003 Presidential Early Career Awards for Scientists and Engineers. In 2001, he also received an award from the Okawa Foundations. 相似文献
Mehdi Sharifzadeh (Corresponding author)Email: URL: http://infolab.usc.edu |
Cyrus ShahabiEmail: |
Mehdi Sharifzadeh received his B.S. and M.S. degrees in Computer Engineering from Sharif University of Technology in Tehran, Iran, in 1995, and 1998, respectively. He received his Ph.D. degree in Computer Science from the University of Southern California in May 2007. His research interests include spatial and spatio-temporal databases, data stream processing, and sensor networks. Cyrus Shahabi is currently an Associate Professor and the Director of the Information Laboratory (InfoLAB) at the Computer Science Department and also a Research Area Director at the NSF’s Integrated Media Systems Center at the University of Southern California. He received his B.S. in Computer Engineering from Sharif University of Technology in 1989 and then his M.S. and Ph.D. degrees in Computer Science from the University of Southern California in May 1993 and August 1996, respectively. He has two books and more than hundred articles, book chapters, and conference papers in the areas of databases, GIS and multimedia. Dr. Shahabi’s current research interests include Geospatial and Multidimensional Data Analysis, Peer-to-Peer Systems and Streaming Architectures. He is currently an associate editor of the IEEE Transactions on Parallel and Distributed Systems and on the editorial board of ACM Computers in Entertainment magazine. He is also a member of the steering committees of IEEE NetDB and general co-chair of ACM GIS 2007. He serves on many conference program committees such as ACM SIGKDD 2006-08, IEEE ICDE 2006 and 08, SSTD 2005-08 and ACM SIGMOD 2004. Dr. Shahabi is the recipient of the 2002 NSF CAREER Award and 2003 Presidential Early Career Awards for Scientists and Engineers. In 2001, he also received an award from the Okawa Foundations. 相似文献