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81.
This note deals with the implementation of a second-order sliding mode control algorithm for a class of nonlinear systems in which the sign of the high-frequency gain, though constant, is unknown. A specific second-order sliding mode control algorithm, the “Suboptimal” algorithm, is properly modified in order to face the uncertainty in the control direction. It is shown that after a finite time the uncertain sign is identified and the standard finite time convergence takes place from that time on. Simulation results are provided. 相似文献
82.
This article studies the exponential stabilization problem for discrete-time switched linear systems based on a control-Lyapunov function approach. It is proved that a switched linear system is exponentially stabilizable if and only if there exists a piecewise quadratic control-Lyapunov function. Such a converse control-Lyapunov function theorem justifies many of the earlier synthesis methods that have adopted piecewise quadratic Lyapunov functions for convenience or heuristic reasons. In addition, it is also proved that if a switched linear system is exponentially stabilizable, then it must be stabilizable by a stationary suboptimal policy of a related switched linear-quadratic regulator (LQR) problem. Motivated by some recent results of the switched LQR problem, an efficient algorithm is proposed, which is guaranteed to yield a control-Lyapunov function and a stabilizing policy whenever the system is exponentially stabilizable. 相似文献
83.
Alessandro Pollini 《AI & Society》2009,24(2):165-171
In interacting with artificial social agents, novel forms of sociality between humans and machines emerge. The theme of Social
Agency between humans and robots is of emerging importance. In this paper key theoretical issues are discussed in a preliminary
exploration of the concept. We try to understand what Social Agency is and how it is created by, negotiated with, and attributed
to artificial agents. This is done in particular considering socially situated robots and by exploring how people recognize
and accept social agents. The interplay between humans and agents is investigated through dynamics of interpretation, signification
and attribution. The ultimate goal of this research is to explore the challenges and opportunities brought by the design of
socially intelligent agents.
相似文献
Alessandro PolliniEmail: |
84.
Alessandro Farinelli Masoume M. Raeissi Nicolo’ Marchi Nathan Brooks Paul Scerri 《Autonomous Agents and Multi-Agent Systems》2017,31(2):332-361
Team oriented plans have become a popular tool for operators to control teams of autonomous robots to pursue complex objectives in complex environments. Such plans allow an operator to specify high level directives and allow the team to autonomously determine how to implement such directives. However, the operators will often want to interrupt the activities of individual team members to deal with particular situations, such as a danger to a robot that the robot team cannot perceive. Previously, after such interrupts, the operator would usually need to restart the team plan to ensure its success. In this paper, we present an approach to encoding how interrupts can be smoothly handled within a team plan. Building on a team plan formalism that uses Colored Petri Nets, we describe a mechanism that allows a range of interrupts to be handled smoothly, allowing the team to efficiently continue with its task after the operator intervention. We validate the approach with an application of robotic watercraft and show improved overall efficiency. In particular, we consider a situation where several platforms should travel through a set of pre-specified locations, and we identify three specific cases that require the operator to interrupt the plan execution: (i) a boat must be pulled out; (ii) all boats should stop the plan and move to a pre-specified assembly position; (iii) a set of boats must synchronize to traverse a dangerous area one after the other. Our experiments show that the use of our interrupt mechanism decreases the time to complete the plan (up to 48 % reduction) and decreases the operator load (up to 80 % reduction in number of user actions). Moreover, we performed experiments with real robotic platforms to validate the applicability of our mechanism in the actual deployment of robotic watercraft. 相似文献
85.
This paper proposes a novel class of Command Governor (CG) strategies for input and state-related constrained discrete-time LTI systems subject to bounded disturbances in the absence of explicit state or output measurements. While in traditional CG schemes the set-point manipulation is undertaken on the basis of either the actual measure of the state or its suitable estimation, it is shown here that the CG design problem can be solved, with limited performance degradation and with similar properties, also in the case that such an explicit measure is not available. This approach, which will be referred to as the Feed-Forward CG (FF-CG) approach, may be a convenient alternative CG solution in all situations whereby the cost of measuring the state may be a severe limitation, e.g. in distributed or decentralized applications. In order to evaluate the method proposed here, numerical simulations on a physical example have been undertaken and comparisons with the standard state-based CG solution reported. 相似文献
86.
Damien Sulla-Menashe Mark A. Friedl Olga N. Krankina Alessandro Baccini Curtis E. Woodcock Adam Sibley Guoqing Sun Viacheslav Kharuk Vladimir Elsakov 《Remote sensing of environment》2011,115(2):392-403
The Northern Eurasian land mass encompasses a diverse array of land cover types including tundra, boreal forest, wetlands, semi-arid steppe, and agricultural land use. Despite the well-established importance of Northern Eurasia in the global carbon and climate system, the distribution and properties of land cover in this region are not well characterized. To address this knowledge and data gap, a hierarchical mapping approach was developed that encompasses the study area for the Northern Eurasia Earth System Partnership Initiative (NEESPI). The Northern Eurasia Land Cover (NELC) database developed in this study follows the FAO-Land Cover Classification System and provides nested groupings of land cover characteristics, with separate layers for land use, wetlands, and tundra. The database implementation is substantially different from other large-scale land cover datasets that provide maps based on a single set of discrete classes. By providing a database consisting of nested maps and complementary layers, the NELC database provides a flexible framework that allows users to tailor maps to suit their needs. The methods used to create the database combine empirically derived climate–vegetation relationships with results from supervised classifications based on Moderate Resolution Imaging Spectroradiometer (MODIS) data. The hierarchical approach provides an effective framework for integrating climate–vegetation relationships with remote sensing-based classifications, and also allows sources of error to be characterized and attributed to specific levels in the hierarchy. The cross-validated accuracy was 73% for the land cover map and 73% and 91% for the agriculture and wetland classifications, respectively. These results support the use of hierarchical classification and climate–vegetation relationships for mapping land cover at continental scales. 相似文献
87.
Alessandro Lapadula Rosario Pugliese Francesco Tiezzi 《Electronic Notes in Theoretical Computer Science》2008,200(3):133
To provide formal foundations to current (web) services technologies, we put forward using COWS, a process calculus for specifying, combining and analysing services, as a uniform formalism for modelling all the relevant phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, deployment and execution. In this paper, we show that constraints and operations on them can be smoothly incorporated in COWS, and propose a disciplined way to model multisets of constraints and to manipulate them through appropriate interaction protocols. Therefore, we demonstrate that also QoS requirement specifications and SLA achievements, and the phases of dynamic service discovery and negotiation can be comfortably modelled in COWS. We illustrate our approach through a scenario for a service-based web hosting provider. 相似文献
88.
Enver Sangineto Nicola Capuano Matteo Gaeta Alessandro Micarelli 《Universal Access in the Information Society》2008,7(1-2):1-23
This paper presents an approach to automatic course generation and student modeling. The method has been developed during
the European funded projects Diogene and Intraserv, focused on the construction of an adaptive e-learning platform. The aim
of the platform is the automatic generation and personalization of courses, taking into account pedagogical knowledge on the
didactic domain as well as statistic information on both the student’s knowledge degree and learning preferences. Pedagogical
information is described by means of an innovative methodology suitable for effective and efficient course generation and
personalization. Moreover, statistic information can be collected and exploited by the system in order to better describe
the student’s preferences and learning performances. Learning material is chosen by the system matching the student’s learning
preferences with the learning material type, following a pedagogical approach suggested by Felder and Silverman. The paper
discusses how automatic learning material personalization makes it possible to facilitate distance learning access to both
able-bodied and disabled people. Results from the Diogene and Intraserv evaluation are reported and discussed. 相似文献
89.
Sacchi M Spezzani C Carpentiero A Prasciolu M Delaunay R Lüning J Polack F 《The Review of scientific instruments》2007,78(4):043702
We have developed a setup for measuring holographically formed interference patterns using an integrated sample-mask design. The direct space image of the sample is obtained via a two-dimensional Fourier transform of the X-ray diffraction pattern. We present the details of our setup, commenting on the influence of geometrical parameters on the imaging capabilities. As an example, we present and discuss the results of test experiments on a patterned Co film. 相似文献
90.
Bissacco A Chiuso A Soatto S 《IEEE transactions on pattern analysis and machine intelligence》2007,29(11):1958-1972
We address the problem of performing decision tasks, and in particular classification and recognition, in the space of dynamical models in order to compare time series of data. Motivated by the application of recognition of human motion in image sequences, we consider a class of models that include linear dynamics, both stable and marginally stable (periodic), both minimum and non-minimum phase, driven by non-Gaussian processes. This requires extending existing learning and system identification algorithms to handle periodic modes and nonminimum phase behavior, while taking into account higher-order statistics of the data. Once a model is identified, we define a kernel-based cord distance between models that includes their dynamics, their initial conditions as well as input distribution. This is made possible by a novel kernel defined between two arbitrary (non-Gaussian) distributions, which is computed by efficiently solving an optimal transport problem. We validate our choice of models, inference algorithm, and distance on the tasks of human motion synthesis (sample paths of the learned models), and recognition (nearest-neighbor classification in the computed distance). However, our work can be applied more broadly where one needs to compare historical data while taking into account periodic trends, non-minimum phase behavior, and non-Gaussian input distributions. 相似文献