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   2631篇
  免费   127篇
  国内免费   4篇
电工技术   32篇
综合类   11篇
化学工业   370篇
金属工艺   141篇
机械仪表   122篇
建筑科学   110篇
矿业工程   12篇
能源动力   57篇
轻工业   265篇
水利工程   11篇
石油天然气   10篇
无线电   325篇
一般工业技术   413篇
冶金工业   381篇
原子能技术   13篇
自动化技术   489篇
  2023年   17篇
  2022年   30篇
  2021年   64篇
  2020年   33篇
  2019年   53篇
  2018年   63篇
  2017年   66篇
  2016年   88篇
  2015年   59篇
  2014年   87篇
  2013年   178篇
  2012年   110篇
  2011年   146篇
  2010年   114篇
  2009年   148篇
  2008年   135篇
  2007年   122篇
  2006年   131篇
  2005年   131篇
  2004年   95篇
  2003年   95篇
  2002年   83篇
  2001年   45篇
  2000年   37篇
  1999年   48篇
  1998年   100篇
  1997年   71篇
  1996年   68篇
  1995年   52篇
  1994年   28篇
  1993年   46篇
  1992年   21篇
  1991年   16篇
  1990年   17篇
  1989年   17篇
  1988年   12篇
  1987年   13篇
  1986年   17篇
  1985年   12篇
  1984年   8篇
  1983年   11篇
  1982年   7篇
  1980年   5篇
  1979年   6篇
  1978年   7篇
  1977年   5篇
  1976年   15篇
  1975年   6篇
  1973年   5篇
  1972年   4篇
排序方式: 共有2762条查询结果,搜索用时 15 毫秒
71.
We provide a technique to detect the singularities of rational planar curves and to compute the correct order of each singularity including the infinitely near singularities without resorting to blow ups. Our approach employs the given parametrization of the curve and uses a μ-basis for the parametrization to construct two planar algebraic curves whose intersection points correspond to the parameters of the singularities including infinitely near singularities with proper multiplicity. This approach extends Abhyankar's method of t-resultants from planar polynomial curves to rational planar curves. We also derive the classical result that for a rational planar curve of degree n the sum of all the singularities with proper multiplicity is (n−1)(n−2)/2. Examples are provided to flesh out our results.  相似文献   
72.
This paper explores the problem of similarity criteria between nonrigid shapes. Broadly speaking, such criteria are divided into intrinsic and extrinsic, the first referring to the metric structure of the object and the latter to how it is laid out in the Euclidean space. Both criteria have their advantages and disadvantages: extrinsic similarity is sensitive to nonrigid deformations, while intrinsic similarity is sensitive to topological noise. In this paper, we approach the problem from the perspective of metric geometry. We show that by unifying the extrinsic and intrinsic similarity criteria, it is possible to obtain a stronger topology-invariant similarity, suitable for comparing deformed shapes with different topology. We construct this new joint criterion as a tradeoff between the extrinsic and intrinsic similarity and use it as a set-valued distance. Numerical results demonstrate the efficiency of our approach in cases where using either extrinsic or intrinsic criteria alone would fail.  相似文献   
73.
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.
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   
74.
This paper presents interactive smart battery-based storage (BBS) for wind generator (WG) and photovoltaic (PV) systems. The BBS is composed of an asymmetric cascaded H-bridge multilevel inverter (ACMI) with staircase modulation. The structure is parallel to the WG and PV systems, allowing the ACMI to have a reduction in power losses compared to the usual solution for storage connected at the DC-link of the converter for WG or PV systems. Moreover, the BBS is embedded with a decision algorithm running real-time energy costs, plus a battery state-of-charge manager and power quality capabilities, making the described system in this paper very interactive, smart and multifunctional. The paper describes how BBS interacts with the WG and PV and how its performance is improved. Experimental results are presented showing the efficacy of this BBS for renewable energy applications.  相似文献   
75.
76.
The application of object oriented concepts (OO) to the requirements phase of information systems (IS) and software development has been adopted by many proponents of IS and software development methodologies. Although many claims have been made about the effectiveness of OO techniques for improving requirements analysis, very few experimental studies have been done to substantiate these claims. This paper addresses this gap in the literature by conducting an experimental study that attempts to validate the effectiveness of object-oriented analysis (OOA) by comparing it to structured analysis (SA) for producing requirements. We argue that the quality of the requirements specification can be measured and that measurement can be used to compare the effectiveness of OOA and SA. We present an overview of the basic models and principles associated with OOA and SA, a discussion of quality in requirements definition, and a detailed discussion of the research methodology used. A review of relevant research is also presented and directions for further research are suggested. Our findings suggest that the OOA methodology does not necessarily produce better requirements statements.  相似文献   
77.
The Fisher Linear Discriminant (FLD) is commonly used in pattern recognition. It finds a linear subspace that maximally separates class patterns according to the Fisher Criterion. Several methods of computing the FLD have been proposed in the literature, most of which require the calculation of the so-called scatter matrices. In this paper, we bring a fresh perspective to FLD via the Fukunaga-Koontz Transform (FKT). We do this by decomposing the whole data space into four subspaces with different discriminability, as measured by eigenvalue ratios. By connecting the eigenvalue ratio with the generalized eigenvalue, we show where the Fisher Criterion is maximally satisfied. We prove the relationship between FLD and FKT analytically, and propose a unified framework to understanding some existing work. Furthermore, we extend our our theory to Multiple Discriminant Analysis (MDA). This is done by transforming the data into intra- and extra-class spaces, followed by maximizing the Bhattacharyya distance. Based on our FKT analysis, we identify the discriminant subspaces of MDA/FKT, and propose an efficient algorithm, which works even when the scatter matrices are singular, or too large to be formed. Our method is general and may be applied to different pattern recognition problems. We validate our method by experimenting on synthetic and real data.  相似文献   
78.
The past few decades have seen a resurgence ofreasoning techniques in artificial intelligenceinvolving both classical and non-classical logics. Inhis paper, ``Multi-valued Logics: A Uniform Approach toReasoning in Artificial Intelligence', Ginsberg hasshown that through the use of bilattices,several reasoning techniques can be unified under asingle framework. A bilattice is a structure that canbe viewed as a class of truth values that canaccommodate incomplete and inconsistent informationand in certain cases default information. Inbilattice theory, knowledge is ordered along twodimensions: truth/falsity and certainty/uncertainty. By defining the corresponding bilattices as truthspaces, Ginsberg has shown that the same theoremprover can be used to simulate reasoning in firstorder logic, default logic, prioritized default logicand assumption truth maintenance system. Although thisis a significant contribution, Ginsberg's paper waslengthy and involved. This paper summarizes some ofthe essential concepts and foundations of bilatticetheory. Furthermore, it discusses the connections ofbilattice theory and several other existingmulti-valued logics such as the various three-valuedlogics and Belnap's four-valued logic. It is notedthat the set of four truth values in Belnap's logicform a lattice structure that is isomorphic to thesimplest bilattice. Subsequently, Fitting proposed aconflation operation that can be used to selectsub-sets of truth values from this and otherbilattices. This method of selecting sub-sets oftruth values provides a means for identifyingsub-logic in a bilattice.  相似文献   
79.
Traumatic brain injury (TBI) is a major cause of morbidity and mortality among children and adolescents. To gain insight into developmental events influenced by TBI, we analyzed subacute mouse brain proteome changes in a percussion head trauma model at P7 ipsi- and contralateral to the site of injury. The comparison of brain proteomes of trauma mice and controls revealed reproducible changes in the intensity of 28 proteins (30 protein spots) in response to trauma. The changes detected suggest that TBI leads to apoptosis, inflammation, and oxidative stress. These changes were consistent with our results of histological and biochemical evaluation of the brains which revealed widespread apoptotic neurodegeneration, microglia activation, and increased levels of protein carbonyls. Furthermore, we detected changes in proteins involved in neuronal migration as well as axonal and dendritic growth and guidance, suggesting interference of trauma with these developmental events.  相似文献   
80.
Since the introduction of sodium metabisulfite as a food preservative, it has been associated with several idiosyncratic reactions (eg, bronchospasm, oculonasal symptoms, and urticaria/angioedema) in sulfite-sensitive individuals. The pathogenic mechanism of these reactions is not yet understood. We report the case of two crewmen on a shrimp trawler who were found dead in the ship's hold. Their deaths had occurred while they were applying dry sodium metabisulfite, referred to as "shrimp dip" in the shrimping industry. Postmortem examinations showed diffuse pulmonary edema consistent with death secondary to asphyxia. Associated findings were visceral congestion. Although it is possible to measure death from sodium metabisulfite with available records, its potential morbidity cannot be estimated. It is known that sodium metabisulfite can react with acids and water, releasing toxic sulfur dioxide (SO2) gas. In addition, SO2 gas reacts with respiratory tissue forming sulfureous acid, and inducing a pulmonary reaction causing hypoxemia. Furthermore, sodium metabisulfite, compared with sodium bisulfite, has a much greater propensity to release SO2 gas. We conclude that there is a need for improved education regarding the potential side effects of sodium metabisulfite, thus eliminating needless occupational morbidity and mortality.  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