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71.
Vectorfields have traditionally been used in computer graphics as a means of visualizing models over time. This paper presents a system which extends the use of vector fields as an interactive tool for physically based three dimensional particle systems and soft objects. The techniques implemented in the system provide the user with new flexibility in animation, modeling and simulation. This paper describes bounded interactive vectorfields and how they can be used to manipulate particle systems and a class of soft objects. Applications to animation, modeling and simulation are also presented. 相似文献
72.
We propose a target tracking method based on particle filtering(PF) to solve the nonlinear non-Gaussian targettracking problem in the bistatic radar systems using external radiation sources. Traditional nonlinear state estimation method is extended Kalman filtering (EKF), which is to do the first level Taylor series extension. It will cause an inaccuracy or even a scatter estimation result on condition that there is either a highly nonlinear target or a large noise square-error. Besides, Kalman filtering is the optimal resolution under a Gaussian noise assumption, and is not suitable to the nonGaussian condition. PF is a sort of statistic filtering based on Monte Carlo simulation that is using some random samples (particles) to simulate the posterior probability density of system random variables. This method can be used in any nonlinear random system. It can be concluded through simulation that PF can achieve higher accuracy than the traditional EKF. 相似文献
73.
74.
四川省作为国家第一批实施节能发电调度的试点省份之一,在落实节能减排政策过程中,面临巨大挑战.研究了适用于电网调度员节能减排发电实时调度的优化模型,以指导调度员实时发电调度.该模型依据节能减排发电排序表.结合四川电网发电运行特点,采用小步长最优次序法,以发电能耗最少为目标函数,并以实例计算验证了该模型的正确性. 相似文献
75.
对访问控制机制中存在的安全性和有效性的问题进行了研究,提出了基于访问树剪枝的属性加密ATP-ABE(Access Tree Pruning Attribute Based Encryption)的访问控制方案。当ATP-ABE算法需要访问它的树型结构访问策略时,通过剪枝处理访问树结构中包含用户ID属性节点的分支,提高了用户所有者DO(Data Owner)管理和控制属性的效率,更加有效地实现了数据共享。还为访问树结构设计了许可访问属性,使DO仍保留共享数据的关键属性,并且能够完全控制它们的共享数据。基于决策双线性密钥交换算法DBDH(Decisional Bilinear Diffie-Hellman)假设分析了ATP-ABE方案的安全性,研究结果表明与两种经典ABE方案比较,ATP-ABE更加有效地减少了算法的系统设置、私钥生成、密文大小、用户属性撤销以及加解密过程中的计算开销,并给出了定量结论。 相似文献
76.
To design a workflow process that is efficient, meaningful, and understandable it is important to properly consider how to compose the activities it will consist of. In this paper, guidelines are presented for this exact purpose. These focus on the elementary data-processing steps that are at the core of a workflow process. The guidelines help to determine the relative importance of these data-processing steps as well as their relatedness, such that activities can be composed in a fully automated manner. We implemented this approach in freely available software. A thorough evaluation that incorporates real-life workflow designs indicates that the use of these guidelines leads to activities that closely resemble those designed by experienced modelers. As such, the proposed guidelines provide a proper and automated alternative to what is otherwise a complex and time-consuming task. 相似文献
77.
Modelling flow phenomena and their related weathering effects is often cumbersome due their dependence on the environment, materials and geometric properties of objects in the scene. Example‐based modelling provides many advantages for reproducing real textures, but little effort has been devoted to reproducing and transferring complex phenomena. In order to produce realistic flow effects, it is possible to take advantage of the widespread availability of flow images on the Internet, which can be used to gather key information about the flow. In this paper, we present a technique that allows the transfer of flow phenomena between photographs, adapting the flow to the target image and giving the user flexibility and control through specifically tailored parameters. This is done through two types of control curves: a fitted theoretical curve to control the mass of deposited material, and an extended colour map for properly adapting to the target appearance. In addition, our method filters and warps the input flow in order to account for the geometric details of the target surface. This leads to a fast and intuitive approach to easily transfer phenomena between images, providing a set of simple and intuitive parameters to control the process. 相似文献
78.
Target design methodologies (DfX) were developed to cope with specific engineering design issues such as cost-effectiveness, manufacturability, assemblability, maintainability, among others. However, DfX methodologies are undergoing the lack of real integration with 3D CAD systems. Their principles are currently applied downstream of the 3D modelling by following the well-known rules available from the literature and engineers’ know-how (tacit internal knowledge).This paper provides a method to formalize complex DfX engineering knowledge into explicit knowledge that can be reused for Advanced Engineering Informatics to aid designers and engineers in developing mechanical products. This research work wants to define a general method (ontology) able to couple DfX design guidelines (engineering knowledge) with geometrical product features of a product 3D model (engineering parametric data). A common layer for all DfX methods (horizontal) and dedicated layers for each DfX method (vertical) allow creating the suitable ontology for the systematic collection of the DfX rules considering each target. Moreover, the proposed framework is the first step for developing (future work) a software tool to assist engineers and designers during product development (3D CAD modelling).A design for assembly (DfA) case study shows how to collect assembly rules in the given framework. It demonstrates the applicability of the CAD-integrated DfX system in the mechanical design of a jig-crane. Several benefits are recognized: (i) systematic collection of DfA rules for informatics development, (ii) identification of assembly issues in the product development process, and (iii) reduction of effort and time during the design review. 相似文献
79.
This work attempts to develop a procedure for the optimal design of a redundantly actuated six degree of freedom parallel
manipulator. A concept of composite design index is developed to deal with multi-criteria based design in a systematic manner,
and this index is employed to obtain a set of optimal dimensions for this manipulator. Two different designs are investigated,
and they are compared in terms of their local characteristics. Finally, the fault-tolerant capability afforded by redundant
actuation is evaluated in terms of partial actuator failures. 相似文献
80.
工业以太网技术的介绍和比较 总被引:6,自引:0,他引:6
杜品圣 《仪器仪表标准化与计量》2005,(5):16-19
近二十多年由于通信技术、计算机技术、网络技术的迅速发展,工业自动化控制领域也随之得到了迅速的提高和改革。自动化工程师不仅将这种新技术大胆地运用到工业实践,而且对如何将现代通信技术成功地应用到工业自动化控制问题进行了激烈的争论。事实证明现代自动控制的发展是与现代通信技术的发展紧密相关的。无论是现场总线还是工业以太网都对工业控制系统的分散化、数字化、智能化和一体化起了决定性的作用。因此学术上的争论将对我们如何看待工业以太网技术的迅猛发展有很大启示。本文对不同的工业以太网的技术作了简单的介绍,并作相应的比较,从而明确未来工业以太网技术的发展方向。 相似文献