全文获取类型
收费全文 | 3457篇 |
免费 | 134篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 44篇 |
综合类 | 6篇 |
化学工业 | 787篇 |
金属工艺 | 110篇 |
机械仪表 | 65篇 |
建筑科学 | 71篇 |
矿业工程 | 5篇 |
能源动力 | 251篇 |
轻工业 | 242篇 |
水利工程 | 22篇 |
石油天然气 | 9篇 |
无线电 | 331篇 |
一般工业技术 | 882篇 |
冶金工业 | 333篇 |
原子能技术 | 24篇 |
自动化技术 | 418篇 |
出版年
2024年 | 10篇 |
2023年 | 44篇 |
2022年 | 78篇 |
2021年 | 150篇 |
2020年 | 97篇 |
2019年 | 127篇 |
2018年 | 150篇 |
2017年 | 128篇 |
2016年 | 111篇 |
2015年 | 76篇 |
2014年 | 122篇 |
2013年 | 305篇 |
2012年 | 150篇 |
2011年 | 209篇 |
2010年 | 135篇 |
2009年 | 154篇 |
2008年 | 113篇 |
2007年 | 138篇 |
2006年 | 99篇 |
2005年 | 85篇 |
2004年 | 72篇 |
2003年 | 76篇 |
2002年 | 61篇 |
2001年 | 46篇 |
2000年 | 42篇 |
1999年 | 50篇 |
1998年 | 70篇 |
1997年 | 61篇 |
1996年 | 52篇 |
1995年 | 54篇 |
1994年 | 48篇 |
1993年 | 45篇 |
1992年 | 44篇 |
1991年 | 36篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 29篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 33篇 |
1982年 | 29篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 21篇 |
1977年 | 4篇 |
1976年 | 22篇 |
1975年 | 7篇 |
排序方式: 共有3600条查询结果,搜索用时 31 毫秒
81.
Identifying some important success factors in adopting agile software development practices 总被引:3,自引:0,他引:3
Agile software development (ASD) is an emerging approach in software engineering, initially advocated by a group of 17 software professionals who practice a set of “lightweight” methods, and share a common set of values of software development. In this paper, we advance the state-of-the-art of the research in this area by conducting a survey-based ex-post-facto study for identifying factors from the perspective of the ASD practitioners that will influence the success of projects that adopt ASD practices. In this paper, we describe a hypothetical success factors framework we developed to address our research question, the hypotheses we conjectured, the research methodology, the data analysis techniques we used to validate the hypotheses, and the results we obtained from data analysis. The study was conducted using an unprecedentedly large-scale survey-based methodology, consisting of respondents who practice ASD and who had experience practicing plan-driven software development in the past. The study indicates that nine of the 14 hypothesized factors have statistically significant relationship with “Success”. The important success factors that were found are: customer satisfaction, customer collaboration, customer commitment, decision time, corporate culture, control, personal characteristics, societal culture, and training and learning. 相似文献
82.
Exception handling enables programmers to specify the behavior of a program when an exceptional event occurs at runtime. Exception handling, thus, facilitates software fault tolerance and the production of reliable and robust software systems. With the recent emergence of multi-processor systems and parallel programming constructs, techniques are needed that provide exception handling support in these environments that are intuitive and easy to use. Unfortunately, extant semantics of exception handling for concurrent settings is significantly more complex to reason about than their serial counterparts.In this paper, we investigate a similarly intuitive semantics for exception handling for the future parallel programming construct in Java. Futures are used by programmers to identify potentially asynchronous computations and to introduce parallelism into sequential programs. The intent of futures is to provide some performance benefits through the use of method-level concurrency while maintaining as-if-serial semantics that novice programmers can easily understand — the semantics of a program with futures is the same as that for an equivalent serial version of the program. We extend this model to provide as-if-serial exception handling semantics. Using this model our runtime delivers exceptions to the same point it would deliver them if the program was executed sequentially. We present the design and implementation of our approach and evaluate its efficiency using an open source Java virtual machine. 相似文献
83.
Saikat Basu Manohar Karki Sangram Ganguly Robert DiBiano Supratik Mukhopadhyay Shreekant Gayaka Rajgopal Kannan Ramakrishna Nemani 《Neural Processing Letters》2017,45(3):855-867
Learning sparse feature representations is a useful instrument for solving an unsupervised learning problem. In this paper, we present three labeled handwritten digit datasets, collectively called n-MNIST by adding noise to the MNIST dataset, and three labeled datasets formed by adding noise to the offline Bangla numeral database. Then we propose a novel framework for the classification of handwritten digits that learns sparse representations using probabilistic quadtrees and Deep Belief Nets. On the MNIST, n-MNIST and noisy Bangla datasets, our framework shows promising results and outperforms traditional Deep Belief Networks. 相似文献
84.
Anirban Bhowmick Mahesh Chandra Astik Biswas 《International Journal of Speech Technology》2017,20(4):813-827
In recent past, wavelet packet (WP) based speech enhancement techniques have been gaining popularity due to their inherent nature of noise minimization. WP based techniques appeared as more robust and efficient than short-time Fourier transform based methods. In the present work, a speech enhancement method using Teager energy operated equal rectangular bandwidth (ERB)-like WP decomposition has been proposed. Twenty four sub-band perceptual wavelet packet decomposition (PWPD) structure is implemented according to the auditory ERB scale. ERB scale based decomposition structure is used because the central frequency of the ERB scale distribution is similar to the frequency response of the human cochlea. Teager energy operator is applied to estimate the threshold value for the PWPD coefficients. Lastly, Wiener filtering is applied to remove the low frequency noise before final reconstruction stage. The proposed method has been applied to evaluate the Hindi sentences database, corrupted with six noise conditions. The proposed method’s performance is analysed with respect to several speech quality parameters and output signal to noise ratio levels. Performance indicates that the proposed technique outperforms some traditional speech enhancement algorithms at all SNR levels. 相似文献
85.
Solving shortest path problem using particle swarm optimization 总被引:6,自引:0,他引:6
This paper presents the investigations on the application of particle swarm optimization (PSO) to solve shortest path (SP) routing problems. A modified priority-based encoding incorporating a heuristic operator for reducing the possibility of loop-formation in the path construction process is proposed for particle representation in PSO. Simulation experiments have been carried out on different network topologies for networks consisting of 15–70 nodes. It is noted that the proposed PSO-based approach can find the optimal path with good success rates and also can find closer sub-optimal paths with high certainty for all the tested networks. It is observed that the performance of the proposed algorithm surpasses those of recently reported genetic algorithm based approaches for this problem. 相似文献
86.
Anindya Kanti De Achintya Mukhopadhyay Ishwar K. Puri 《Microfluidics and nanofluidics》2008,4(5):463-470
The suitable surface modification of microfluidic channels can enable a neutral electrolyte solution to develop an electric
double layer (EDL). The ions contained within the EDL can be moved by applying an external electric field, inducing electroosmotic
flows (EOFs) that results in associated stirring. This provides a solution for the rapid mixing required for many microfluidic
applications. We have investigated EOFs generated by applying a steady electric field across a square cavity that has homogenous
electric potentials along its walls. The flowfield is simulated using the lattice Boltzmann method. The extent of mixing is
characterized for different electrode configurations and electric field strengths. We find that rapid mixing can be achieved
by using this simple configuration which increases with increasing electric field strength. The mixing time for water-soluble
organic molecules can be decreased by four orders of magnitude by suitable choice of wall zeta potential and electric field.
We dedicate this paper to the memory of our colleagues Professors Kevin Granata and Liviu Librescu who fell tragically on
April 16, 2007 while answering their call to serve higher education. They continue to inspire us. AM gratefully acknowledges
support from Jadavpur University under the World Bank funded Technical Education Quality Improvement Programme of the Government
of India and the hospitality of the Virginia Tech ESM Department where he conducted a portion of this work. 相似文献
87.
Visual media data such as an image is the raw data representation for many important applications. Reducing the dimensionality of raw visual media data is desirable since high dimensionality degrades not only the effectiveness but also the efficiency of visual recognition algorithms. We present a comparative study on spatial interest pixels (SIPs), including eight-way (a novel SIP detector), Harris, and Lucas‐Kanade, whose extraction is considered as an important step in reducing the dimensionality of visual media data. With extensive case studies, we have shown the usefulness of SIPs as low-level features of visual media data. A class-preserving dimension reduction algorithm (using GSVD) is applied to further reduce the dimension of feature vectors based on SIPs. The experiments showed its superiority over PCA.
相似文献
Chandra KambhamettuEmail: |
88.
The execution model for mobile, dynamically‐linked, object‐oriented programs has evolved from fast interpretation to a mix of interpreted and dynamically compiled execution. The primary motivation for dynamic compilation is that compiled code executes significantly faster than interpreted code. However, dynamic compilation, which is performed while the application is running, introduces execution delay. In this paper we present two dynamic compilation techniques that enable high performance execution while reducing the effect of this compilation overhead. These techniques can be classified as (1) decreasing the amount of compilation performed, and (2) overlapping compilation with execution. We first present and evaluate lazy compilation, an approach used in most dynamic compilation systems in which individual methods are compiled on‐demand upon their first invocation. This is in contrast to eager compilation, in which all methods in a class are compiled when a new class is loaded. In this work, we describe our experience with eager compilation, as well as the implementation and transition to lazy compilation. We empirically detail the effectiveness of this decision. Our experimental results using the SpecJVM Java benchmarks and the Jalapeño JVM show that, compared to eager compilation, lazy compilation results in 57% fewer methods being compiled and reductions in total time of 14 to 26%. Total time in this context is compilation plus execution time. Next, we present profile‐driven, background compilation, a technique that augments lazy compilation by using idle cycles in multiprocessor systems to overlap compilation with application execution. With this approach, compilation occurs on a thread separate from that of application threads so as to reduce intermittent, and possibly substantial, delay in execution. Profile information is used to prioritize methods as candidates for background compilation. Methods are compiled according to this priority scheme so that performance‐critical methods are invoked using optimized code as soon as possible. Our results indicate that background compilation can achieve the performance of off‐line compiled applications and masks almost all compilation overhead. We show significant reductions in total time of 14 to 71% over lazy compilation. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
89.
Summary The amount of nondeterminism in a nondeterministic finite automaton (NFA) is measured by counting the minimal number of guessing points a string w has to pass through on its way to an accepting state. NFA's with more nondeterminism can achieve greater savings in the number of states over their deterministic counterparts than NFA's with less nondeterminism. On the other hand, for some nontrivial infinite regular languages a deterministic finite automaton (DFA) can already be quite succinct in the sense that NFA's need as many states (and even context-free grammars need as many nonterminals) as the minimal DFA has states.This research was supported in part by the National Science Foundation under Grant No. MCS 76-10076 相似文献
90.
Three results are established. The first is that every nondeterministic strict interpretation of a deterministic pushdown acceptor (dpda) has an equivalent, deterministic, strict interpretation. The second is that ifM
1 andM
2 are two compatible strict interpretations of the dpdaM, then there exist deterministic strict interpretationsM
andM
such thatL(M
) =L(M
1)L(M
2) andL(M
) =L(M
1)L(M
2). The third states that there is no dpda whose strict interpretations yield all the deterministic context-free languages.This author was supported in part by the National Science Foundation under Grant MCS-77-22323. 相似文献