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61.
We describe a method to compute the internal parameters (focal and principal point) of a camera with known position and orientation, based on the observation of two or more conics on a known plane. The conics can even be degenerate (e.g., pairs of lines). The proposed method can be used to re-estimate the internal parameters of a fully calibrated camera after zooming to a new, unknown, focal length. It also allows estimating the internal parameters when a second, fully calibrated camera observes the same conics. The parameters estimated through the proposed method are coherent with the output of more traditional procedures that require a higher number of calibration images. A deep analysis of the geometrical configurations that influence the proposed method is also reported. 相似文献
62.
João André Cristina Santos Lino Costa 《Journal of Intelligent and Robotic Systems》2016,82(3-4):379-397
Robots must be able to adapt their motor behavior to unexpected situations in order to safely move among humans. A necessary step is to be able to predict failures, which result in behavior abnormalities and may cause irrecoverable damage to the robot and its surroundings, i.e. humans. In this paper we build a predictive model of sensor traces that enables early failure detection by means of a skill memory. Specifically, we propose an architecture based on a biped locomotion solution with improved robustness due to sensory feedback, and extend the concept of Associative Skill Memories (ASM) to periodic movements by introducing several mechanisms into the training workflow, such as linear interpolation and regression into a Dynamical Motion Primitive (DMP) system such that representation becomes time invariant and easily parameterizable. The failure detection mechanism applies statistical tests to determine the optimal operating conditions. Both training and failure testing were conducted on a DARwIn-OP inside a simulation environment to assess and validate the failure detection system proposed. Results show that the system performance in terms of the compromise between sensitivity and specificity is similar with and without the proposed mechanism, while achieving a significant data size reduction due to the periodic approach taken. 相似文献
63.
Rodrigo Costa Mateus Thiago Luís Lopes Siqueira Valéria Cesário Times Ricardo Rodrigues Ciferri Cristina Dutra de Aguiar Ciferri 《Distributed and Parallel Databases》2016,34(3):425-461
Cloud computing systems handle large volumes of data by using almost unlimited computational resources, while spatial data warehouses (SDWs) are multidimensional databases that store huge volumes of both spatial data and conventional data. Cloud computing environments have been considered adequate to host voluminous databases, process analytical workloads and deliver database as a service, while spatial online analytical processing (spatial OLAP) queries issued over SDWs are intrinsically analytical. However, hosting a SDW in the cloud and processing spatial OLAP queries over such database impose novel obstacles. In this article, we introduce novel concepts as cloud SDW and spatial OLAP as a service, and afterwards detail the design of novel schemas for cloud SDW and spatial OLAP query processing over cloud SDW. Furthermore, we evaluate the performance to process spatial OLAP queries in cloud SDWs using our own query processor aided by a cloud spatial index. Moreover, we describe the cloud spatial bitmap index to improve the performance to process spatial OLAP queries in cloud SDWs, and assess it through an experimental evaluation. Results derived from our experiments revealed that such index was capable to reduce the query response time from 58.20 up to 98.89 %. 相似文献
64.
Cristian Danila Georgiana Stegaru Aurelian Mihai Stanescu Cristina Serbanescu 《Journal of Intelligent Manufacturing》2016,27(1):73-82
Integration of Web-Services and “smart objects” in supply chain manufacturing systems (SCM) enables enterprise innovation and competitiveness in a globalized economy. The paper proposes a web-service based architecture for SCM that enables enterprises to develop context-awareness and to achieve interoperability at data, services, processes and business levels using event based web service notifications. The architecture is analyzed and implemented following the case study of an enterprise in the automotive industry. 相似文献
65.
In the study of data exchange one usually assumes an open-world semantics, making it possible to extend instances of target schemas. An alternative closed-world semantics only moves ‘as much data as needed’ from the source to the target to satisfy constraints of a schema mapping. It avoids some of the problems exhibited by the open-world semantics, but limits the expressivity of schema mappings. Here we propose a mixed approach: one can designate different attributes of target schemas as open or closed, to combine the additional expressivity of the open-world semantics with the better behavior of query answering in closed worlds. We define such schema mappings, and show that they cover a large space of data exchange solutions with two extremes being the known open and closed-world semantics. We investigate the problems of query answering and schema mapping composition, and prove two trichotomy theorems, classifying their complexity based on the number of open attributes. We find conditions under which schema mappings compose, extending known results to a wide range of closed-world mappings. We also provide results for restricted classes of queries and mappings guaranteeing lower complexity. 相似文献
66.
Rodrigo RomanAuthor Vitae Cristina AlcarazAuthor Vitae 《Computers & Electrical Engineering》2011,37(2):147-159
If a wireless sensor network (WSN) is to be completely integrated into the Internet as part of the Internet of Things (IoT), it is necessary to consider various security challenges, such as the creation of a secure channel between an Internet host and a sensor node. In order to create such a channel, it is necessary to provide key management mechanisms that allow two remote devices to negotiate certain security credentials (e.g. secret keys) that will be used to protect the information flow. In this paper we will analyse not only the applicability of existing mechanisms such as public key cryptography and pre-shared keys for sensor nodes in the IoT context, but also the applicability of those link-layer oriented key management systems (KMS) whose original purpose is to provide shared keys for sensor nodes belonging to the same WSN. 相似文献
67.
68.
Dolors Costal Cristina Gómez Anna Queralt Ruth Raventós Ernest Teniente 《Software and Systems Modeling》2008,7(4):469-486
An important aspect in the specification of conceptual schemas is the definition of general constraints that cannot be expressed
by the predefined constructs provided by conceptual modeling languages. This is generally achieved by using general-purpose
languages like OCL. In this paper we propose a new approach that facilitates the definition of such general constraints in
UML. More precisely, we define a profile that extends the set of predefined UML constraints by adding certain types of constraints
that are commonly used in conceptual schemas. We also show how our proposal facilitates reasoning about the constraints and
their automatic code generation, study the application of our ideas to the specification of two real-life applications, and
present a prototype tool implementation.
相似文献
Ernest TenienteEmail: |
69.
Fernández-Miyakawa ME Dorr R Fernández LE Uzal FA Ibarra C 《Computer methods and programs in biomedicine》2007,85(2):95-100
This paper describes the development of a simple system for measurement of net water movement through biological membrane barriers. The system is based on the detection of a water meniscus inside a polyethylene tube, which reflects the water movement inside one hemichamber of a modified Ussing chamber containing a membrane barrier. The detection device consists of a commercial computer-controlled flat bed scanner and specifically developed software. This system allows one to perform a relatively high number of individual experiments per physical unit. It is a flexible and affordable device, which allows comparatively more information per unit to be obtained than previously described methods. 相似文献
70.
Ignacio Fernández Manuel Mazo José L. Lázaro Daniel Pizarro Enrique Santiso Pedro Martín Cristina Losada 《Autonomous Robots》2007,23(4):305-324
This paper presents a new proposal for positioning and guiding mobile robots in indoor environments. The proposal is based
on the information provided by static cameras located in the movement environment. This proposal falls within the scope of
what are known as intelligent environments; in this case, the environment is provided with cameras that, once calibrated,
allow the position of the robots to be obtained. Based on this information, control orders for the robots can be generated
using a radio frequency link. In order to facilitate identification of the robots, even under extremely adverse ambient lighting
conditions, a beacon consisting of four circular elements constructed from infrared diodes is mounted on board the robots.
In order to identify the beacon, an edge detection process is carried out. This is followed by a process that, based on the
algebraic distance, obtains the estimated ellipses associated with each element of the beacon. Once the beacon has been identified,
the coordinates of the centroids for the elements that make up the beacon are obtained on the various image planes. Based
on these coordinates, an algorithm is proposed that takes into account the standard deviation of the error produced in the
various cameras in ascertaining the coordinates of the beacon’s elements. An odometric system is also used in guidance that,
in conjunction with a Kalman Filter, allows the position of the robot to be estimated during the time intervals required to
process the visual information provided by the cameras.
相似文献
Cristina LosadaEmail: |