全文获取类型
收费全文 | 2741篇 |
免费 | 228篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 791篇 |
金属工艺 | 58篇 |
机械仪表 | 72篇 |
建筑科学 | 105篇 |
矿业工程 | 11篇 |
能源动力 | 96篇 |
轻工业 | 449篇 |
水利工程 | 23篇 |
石油天然气 | 12篇 |
无线电 | 185篇 |
一般工业技术 | 403篇 |
冶金工业 | 134篇 |
原子能技术 | 25篇 |
自动化技术 | 589篇 |
出版年
2024年 | 9篇 |
2023年 | 43篇 |
2022年 | 117篇 |
2021年 | 151篇 |
2020年 | 88篇 |
2019年 | 110篇 |
2018年 | 118篇 |
2017年 | 105篇 |
2016年 | 147篇 |
2015年 | 93篇 |
2014年 | 153篇 |
2013年 | 243篇 |
2012年 | 209篇 |
2011年 | 203篇 |
2010年 | 154篇 |
2009年 | 138篇 |
2008年 | 131篇 |
2007年 | 123篇 |
2006年 | 82篇 |
2005年 | 70篇 |
2004年 | 73篇 |
2003年 | 49篇 |
2002年 | 57篇 |
2001年 | 30篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 31篇 |
1997年 | 32篇 |
1996年 | 15篇 |
1995年 | 23篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2972条查询结果,搜索用时 15 毫秒
71.
Luis V. Santana-Quintero Alfredo G. Hernández-Díaz Julián Molina Carlos A. Coello Coello Rafael Caballero 《Computers & Operations Research》2010,37(3):470-480
The aim of this paper is to show how the hybridization of a multi-objective evolutionary algorithm (MOEA) and a local search method based on the use of rough set theory is a viable alternative to obtain a robust algorithm able to solve difficult constrained multi-objective optimization problems at a moderate computational cost. This paper extends a previously published MOEA [Hernández-Díaz AG, Santana-Quintero LV, Coello Coello C, Caballero R, Molina J. A new proposal for multi-objective optimization using differential evolution and rough set theory. In: 2006 genetic and evolutionary computation conference (GECCO’2006). Seattle, Washington, USA: ACM Press; July 2006], which was limited to unconstrained multi-objective optimization problems. Here, the main idea is to use this sort of hybrid approach to approximate the Pareto front of a constrained multi-objective optimization problem while performing a relatively low number of fitness function evaluations. Since in real-world problems the cost of evaluating the objective functions is the most significant, our underlying assumption is that, by aiming to minimize the number of such evaluations, our MOEA can be considered efficient. As in its previous version, our hybrid approach operates in two stages: in the first one, a multi-objective version of differential evolution is used to generate an initial approximation of the Pareto front. Then, in the second stage, rough set theory is used to improve the spread and quality of this initial approximation. To assess the performance of our proposed approach, we adopt, on the one hand, a set of standard bi-objective constrained test problems and, on the other hand, a large real-world problem with eight objective functions and 160 decision variables. The first set of problems are solved performing 10,000 fitness function evaluations, which is a competitive value compared to the number of evaluations previously reported in the specialized literature for such problems. The real-world problem is solved performing 250,000 fitness function evaluations, mainly because of its high dimensionality. Our results are compared with respect to those generated by NSGA-II, which is a MOEA representative of the state-of-the-art in the area. 相似文献
72.
The linear complete differential resultant of a finite set of linear ordinary differential polynomials is defined. We study the computation by linear complete differential resultants of the implicit equation of a system of n linear differential polynomial parametric equations in n−1 differential parameters. We give necessary conditions to ensure properness of the system of differential polynomial parametric equations. 相似文献
73.
David Schleicher Luis M. Bergasa Manuel Ocaña Rafael Barea Elena López 《Robotics and Autonomous Systems》2010,58(8):991-1002
In this paper we present a new real-time hierarchical (topological/metric) Visual SLAM system focusing on the localization of a vehicle in large-scale outdoor urban environments. It is exclusively based on the visual information provided by a cheap wide-angle stereo camera. Our approach divides the whole map into local sub-maps identified by the so-called fingerprints (vehicle poses). At the sub-map level (low level SLAM), 3D sequential mapping of natural landmarks and the robot location/orientation are obtained using a top-down Bayesian method to model the dynamic behavior. A higher topological level (high level SLAM) based on fingerprints has been added to reduce the global accumulated drift, keeping real-time constraints. Using this hierarchical strategy, we keep the local consistency of the metric sub-maps, by mean of the EKF, and global consistency by using the topological map and the MultiLevel Relaxation (MLR) algorithm. Some experimental results for different large-scale outdoor environments are presented, showing an almost constant processing time. 相似文献
74.
Rafael Rieder Alberto Barbosa Raposo Márcio Sarroglia Pinho 《Journal of Visual Languages and Computing》2010,21(3):136-156
This work presents a methodology to formally model and to build three-dimensional interaction tasks in virtual environments using three different tools: Petri Nets, the Interaction Technique Decomposition taxonomy, and Object-Oriented techniques. User operations in the virtual environment are represented as Petri Net nodes; these nodes, when linked, represent the interaction process stages. In our methodology, places represent all the states an application can reach, transitions define the conditions to start an action, and tokens embody the data manipulated by the application. As a result of this modeling process we automatically generate the core of the application's source code. We also use a Petri Net execution library to run the application code. In order to facilitate the application modeling, we have adapted Dia, a well-known graphical diagram editor, to support Petri Nets creation and code generation. The integration of these approaches results in a modular application, based on Petri Nets formalism that allows for the specification of an interaction task and for the reuse of developed blocks in new virtual environment projects. 相似文献
75.
Rafael Bárcena Ainhoa Etxebarria 《International Journal of Control, Automation and Systems》2010,8(2):244-249
A study on the convenient tuning of fractional-order hold electronic devices for digital control systems is presented. When certain constraints are fulfilled, this study assures in advance the attainment of inverse stable discrete plants. The main result is based on classic numerical analysis techniques and is applicable when the process to be digitally controlled is described as a second order plant or as a first order plant with time delay. In such cases, by using a conveniently tuned fractional-order hold, the discretization nonminimum-phase zeros emerged when using a common zero-order hold are avoided. In this way, the performance of the digitally controlled system may be improved. 相似文献
76.
J. Rafael Sendra 《Journal of Symbolic Computation》2011,46(9):1030-1038
We present algorithms for parametrizing by radicals an irreducible curve, not necessarily plane, when the genus is less than or equal to 4 and the curve is defined over an algebraically closed field of characteristic zero. In addition, we also present an algorithm for parametrizing by radicals any irreducible plane curve of degree d having at least a point of multiplicity d−r, with 1≤r≤4 and, as a consequence, every irreducible plane curve of degree d≤5 and every irreducible singular plane curve of degree 6. 相似文献
77.
Rafael Marín-LópezAuthor Vitae Fernando Pereñíguez Author VitaeGabriel López Author Vitae Alejandro Pérez-Méndez Author Vitae 《Computer Standards & Interfaces》2011,33(5):494-504
Kerberos is a well-known standard protocol which is becoming one of the most widely deployed for authentication and key distribution in application services. However, whereas service providers use the protocol to control their own subscribers, they do not widely deploy Kerberos infrastructures to handle subscribers coming from foreign domains, as happens in network federations. Instead, the deployment of Authentication, Authorization and Accounting (AAA) infrastructures has been preferred for that operation. Thus, the lack of a correct integration between these infrastructures and Kerberos limits the service access only to service provider's subscribers. To avoid this limitation, we design an architecture which integrates a Kerberos pre-authentication mechanism, based on the use of the Extensible Authentication Protocol (EAP), and advanced authorization, based on the standards SAML and XACML, to link the end user authentication and authorization performed through an AAA infrastructure with the delivery of Kerberos tickets in the service provider's domain. We detail the interfaces, protocols, operation and extensions required for our solution. Moreover, we discuss important aspects such as the implications on existing standards. 相似文献
78.
79.
Cross-entropy has been recently proposed as a heuristic method for solving combinatorial optimization problems. We briefly review this methodology and then suggest a hybrid version with the goal of improving its performance. In the context of the well-known max-cut problem, we compare an implementation of the original cross-entropy method with our proposed version. The suggested changes are not particular to the max-cut problem and could be considered for future applications to other combinatorial optimization problems. 相似文献
80.
Particle swarm optimization (PSO) is an evolutionary metaheuristic inspired by the flocking behaviour of birds, which has successfully been used to solve several kinds of problems, although there are few studies aimed at solving discrete optimization problems. One disadvantage of PSO is the risk of a premature search convergence. To prevent this, we propose to introduce diversity into a discrete PSO by adding a random velocity. The degree of the introduced diversity is not static (i.e. preset before running PSO) but instead changes dynamically according to the heterogeneity of the population (i.e. if the search has converged or not). We solve the response time variability problem (RTVP) to test these two new ideas. The RTVP is an NP-hard combinatorial scheduling problem that has recently appeared in the literature. It occurs whenever products, clients or jobs need to be sequenced in such a way that the variability in the time between the instants at which they receive the necessary resources is minimized. The most efficient algorithm for solving non-small instances of the RTVP published to date is a classical PSO algorithm, referred to by the authors as PSO-M1F. In this paper, we propose 10 discrete PSO algorithms for solving the RTVP: one based on the ideas described above (PSO -c3dyn) and nine based on strategies proposed in the literature and adapted for solving a discrete optimization problem such as the RTVP. We compare all 11 PSO algorithms and the computational experiment shows that, on average, the best results obtained are due to our proposal of dynamic control mechanism for introducing diversity. 相似文献