全文获取类型
收费全文 | 3621篇 |
免费 | 204篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 37篇 |
综合类 | 1篇 |
化学工业 | 747篇 |
金属工艺 | 73篇 |
机械仪表 | 82篇 |
建筑科学 | 162篇 |
矿业工程 | 1篇 |
能源动力 | 117篇 |
轻工业 | 239篇 |
水利工程 | 33篇 |
石油天然气 | 13篇 |
无线电 | 366篇 |
一般工业技术 | 778篇 |
冶金工业 | 428篇 |
原子能技术 | 34篇 |
自动化技术 | 728篇 |
出版年
2023年 | 26篇 |
2022年 | 67篇 |
2021年 | 92篇 |
2020年 | 78篇 |
2019年 | 71篇 |
2018年 | 118篇 |
2017年 | 104篇 |
2016年 | 116篇 |
2015年 | 100篇 |
2014年 | 141篇 |
2013年 | 228篇 |
2012年 | 219篇 |
2011年 | 275篇 |
2010年 | 194篇 |
2009年 | 225篇 |
2008年 | 209篇 |
2007年 | 188篇 |
2006年 | 129篇 |
2005年 | 101篇 |
2004年 | 99篇 |
2003年 | 95篇 |
2002年 | 83篇 |
2001年 | 44篇 |
2000年 | 52篇 |
1999年 | 62篇 |
1998年 | 113篇 |
1997年 | 83篇 |
1996年 | 62篇 |
1995年 | 29篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 15篇 |
1986年 | 25篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1972年 | 7篇 |
排序方式: 共有3839条查询结果,搜索用时 109 毫秒
61.
Why would people use Short Message Service (SMS) to say something they would not say in person? There is a trend that SMS is becoming more and more popular because it facilitates more extended modes of communications. Using technology acceptance model, we hypothesize the attitude of SMS would be influenced by its perceived effectiveness for communications, perceived ease of use, and subjective norm. Besides the special aspects of communications, conflict avoidance and privacy protection will enforce the impact of perceived effectiveness of SMS for communication. We investigated 953 SMS users and the results support most of our hypotheses. Furthermore, our analyses also show there are differences between females and males on the influence mechanism behind their attitude towards SMS. 相似文献
62.
Jean-François Jerier Vincent Richefeu Didier Imbault Fréderic-Victor Donzé 《Computer Methods in Applied Mechanics and Engineering》2010,199(25-28):1668-1676
We introduce a new geometric method to generate sphere packings with restricted overlap values. Sample generation is an important, but time-consuming, step that precedes a calculation performed with the discrete element method (DEM). At present, there does not exist any software dedicated to DEM which would be similar to the mesh software that exists for finite element methods (FEM). A practical objective of the method is to build very large sphere packings (several hundreds of thousands) in a few minutes instead of several days as the current dynamic methods do. The developed algorithm uses a new geometric procedure to position very efficiently the polydisperse spheres in a tetrahedral mesh. The algorithm, implemented into YADE-OPEN DEM (open-source software), consists in filling tetrahedral meshes with spheres. In addition to the features of the tetrahedral mesh, the input parameters are the minimum and maximum radii (or their size ratio), and the magnitude of authorized overlaps. The filling procedure is stopped when a target solid fraction or number of spheres is reached. Based on this method, an efficient tool can be designed for DEMs used by researchers and engineers. The generated packings can be isotropic and the number of contacts per sphere is very high due to its geometric procedure. In this paper, different properties of the generated packings are characterized and examples from real industrial problems are presented to show how this method can be used. The current C++ version of this packing algorithm is part of YADE-OPEN DEM [20] available on the web (https://yade-dem.org). 相似文献
63.
The performance evaluation is regarded as a multiple criteria decision making (MCDM) problem and has a significant impact on the operations of the enterprise. This paper develops an integrated MCDM approach that combines the voting method and the fuzzy TOPSIS (technique for order preference by similarity to ideal solution) method to evaluate the performance of multiple manufacturing plants in a fuzzy environment. Fuzzy TOPSIS helps decision-makers carry out analysis and comparisons in ranking their preference of the alternatives with vague or imprecise data. Since the evaluation result is often greatly affected by the weights used in the evaluation process, the voting method is used in this study to determine the appropriate criteria weights. A case study demonstrating the applicability of the proposed model is presented. The case company is the world’s largest manufacturer of power supplies. It has three primary manufacturing bases located in Wujiang, Dongguan, and Tianjin, China. The proposed approach is used to evaluate the performance of the company’s five manufacturing plants in Wujiang, which produce switch power, telecom power, DC/DC converters, uninterruptible power systems (UPS) and AC/DC adapters. 相似文献
64.
This paper proposes a novel fault tolerant control (FTC) scheme for hybrid systems modeled by hybrid Petri nets (HPNs). The HPNs model consists of discrete and continuous PNs. The faults are represented by unobservable discrete transitions or the normal observable discrete transitions with abnormal firing time in discrete PNs. First, an observer‐based fault diagnosis method is proposed to estimate the marking in discrete places with unknown initial marking and diagnose the faulty behavior simultaneously. Then, an adaptive fault tolerant controller is designed to maintain the general mutual exclusion constraints (GMEC) of discrete PNs, and a scheme that adjusts firing speeds of continuous transitions is provided to maintain the optimality of continuous PNs. Finally, an example of an intelligent transportation system consisting of automated vehicles on a bridge is included to demonstrate the effectiveness of our developed techniques. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
65.
A large number of methods have been proposed for ranking fuzzy numbers in the last few decades. Nevertheless, none of these methods can always guarantee a consistent result for every situation. Some of them are even non-intuitive and not discriminating. Chen proposed a ranking method in 1985 to overcome these limitations and simplify the computational procedure based on the criteria of total utility through maximizing set and minimizing set. However, there were some shortcomings associated with Chen’s ranking method. Therefore, we propose a revised ranking method that can overcome these shortcomings. Instead of considering just a single left and a single right utility in the total utility, the proposed method considers two left and two right utilities. In addition, the proposed method also takes into account the decision maker’s optimistic attitude of fuzzy numbers. Several comparative examples and an application demonstrating the usage, advantages, and applicability of the revised ranking method are presented. It can be concluded that the revised ranking method can effectively resolve the issues with Chen’s ranking method. Moreover, the revised ranking method can be used to differentiate different types of fuzzy numbers. 相似文献
66.
Comparing e-Learning tools’ success: The case of instructor–student interactive vs. self-paced tools
e-Learning tools have profoundly transformed modern pedagogical approaches. Vendors provide different types of systems, such as self-paced (SP) and instructor–student interactive (ISI) e-Learning tools. Although both types of tools represent promising solutions to facilitate the learning process, it is important to theoretically identify a framework to evaluate the success of these tools and assess whether one type of tool is more effective than another. Toward this end, we (1) propose a model to evaluate e-Learning tools’ success by extending and contextualizing Seddon’s information systems (IS) success model for the e-Learning environment and (2) formulate four hypotheses to predict the differences in the success factors between SP and ISI tools. We test the model and hypotheses using data from 783 students across seven higher education institutions in Hong Kong. The results support the proposed e-Learning tool success model and three of the four hypotheses. ISI tools outperform SP tools in terms of system quality, perceived usefulness, satisfaction, and learning outcome. 相似文献
67.
We study a probabilistic version of coherence spaces and show that these objects provide a model of linear logic. We build a model of the pure lambda-calculus in this setting and show how to interpret a probabilistic version of the functional language PCF. We give a probabilistic interpretation of the semantics of probabilistic PCF closed terms of ground type. Last we suggest a generalization of this approach, using Banach spaces. 相似文献
68.
Gregory Chockler Seth Gilbert Vincent Gramoli Peter M. Musial Alex A. Shvartsman 《Journal of Parallel and Distributed Computing》2009
This paper presents a new algorithm for implementing a reconfigurable distributed shared memory in an asynchronous dynamic network. The algorithm guarantees atomic consistency (linearizability) in all executions in the presence of arbitrary crash failures of the processing nodes, message delays, and message loss. The algorithm incorporates a classic quorum-based algorithm for read/write operations, and an optimized consensus protocol, based on Fast Paxos for reconfiguration, and achieves the design goals of: (i) allowing read and write operations to complete rapidly and (ii) providing long-term fault-tolerance through reconfiguration, a process that evolves the quorum configurations used by the read and write operations. The resulting algorithm tolerates dynamism. We formally prove our algorithm to be correct, we present its performance and compare it to existing reconfigurable memories, and we evaluate experimentally the cost of its reconfiguration mechanism. 相似文献
69.
Sanjiv Singh Marcel Bergerman Jillian Cannons Benjamin Grocholsky Bradley Hamner German Holguin Larry Hull Vincent Jones George Kantor Harvey Koselka Guiqin Li James Owen Johnny Park Wenfan Shi James Teza 《Intelligent Service Robotics》2010,3(4):245-262
Comprehensive Automation for Specialty Crops is a project focused on the needs of the specialty crops sector, with a focus on apples and nursery trees. The project’s main thrusts are the integration of robotics technology and plant science; understanding and overcoming socio-economic barriers to technology adoption; and making the results available to growers and stakeholders through a nationwide outreach program. In this article, we present the results obtained and lessons learned in the first year of the project with a reconfigurable mobility infrastructure for autonomous farm driving. We then present sensor systems developed to enable three real-world agricultural applications—insect monitoring, crop load scouting, and caliper measurement—and discuss how they can be deployed autonomously to yield increased production efficiency and reduced labor costs. 相似文献
70.
Computational aspects of the expected differential probability of 4-round AES and AES-like ciphers 总被引:1,自引:0,他引:1
Joan Daemen Mario Lamberger Norbert Pramstaller Vincent Rijmen Frederik Vercauteren 《Computing》2009,85(1-2):85-104
In this paper we study the security of the Advanced Encryption Standard (AES) and AES-like block ciphers against differential cryptanalysis. Differential cryptanalysis is one of the most powerful methods for analyzing the security of block ciphers. Even though no formal proofs for the security of AES against differential cryptanalysis have been provided to date, some attempts to compute the maximum expected differential probability (MEDP) for two and four rounds of AES have been presented recently. In this paper, we will improve upon existing approaches in order to derive better bounds on the EDP for two and four rounds of AES based on a slightly simplified S-box. More precisely, we are able to provide the complete distribution of the EDP for two rounds of this AES variant with five active S-boxes and methods to improve the estimates for the EDP in the case of six active S-boxes. 相似文献