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   1486篇
  免费   93篇
  国内免费   12篇
电工技术   18篇
综合类   34篇
化学工业   267篇
金属工艺   57篇
机械仪表   106篇
建筑科学   41篇
矿业工程   6篇
能源动力   68篇
轻工业   118篇
水利工程   10篇
石油天然气   20篇
无线电   223篇
一般工业技术   329篇
冶金工业   119篇
原子能技术   9篇
自动化技术   166篇
  2023年   17篇
  2022年   19篇
  2021年   41篇
  2020年   35篇
  2019年   41篇
  2018年   39篇
  2017年   52篇
  2016年   30篇
  2015年   30篇
  2014年   78篇
  2013年   93篇
  2012年   102篇
  2011年   102篇
  2010年   72篇
  2009年   84篇
  2008年   73篇
  2007年   61篇
  2006年   70篇
  2005年   51篇
  2004年   31篇
  2003年   43篇
  2002年   46篇
  2001年   35篇
  2000年   29篇
  1999年   30篇
  1998年   51篇
  1997年   46篇
  1996年   38篇
  1995年   22篇
  1994年   21篇
  1993年   15篇
  1992年   18篇
  1991年   10篇
  1990年   12篇
  1989年   7篇
  1988年   4篇
  1987年   6篇
  1986年   2篇
  1985年   6篇
  1984年   4篇
  1983年   3篇
  1980年   2篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1974年   4篇
  1972年   1篇
  1971年   1篇
  1968年   1篇
  1944年   1篇
排序方式: 共有1591条查询结果,搜索用时 78 毫秒
31.
随着现代制造业的迅速发展,我国的物流行业也随之崛起,并且逐渐受到全社会的广泛关注。早期的人工物流、机械化物流方式,已经远远不能满足现在大规模生产流水线的需求。本文提出了一种基于RGV、AGV的柔性输送系统,其中环形RGV输送系统通过成对的码头和码头之间的流水线与AGV输送系统、非环形往复式RGV输送系统相接驳;AGV输送系统和非环形往复式RGV输送系统用于将物流货品从环形RGV输送系统送入或送出指定物流系统。该系统有效地克服传统单一RGV输送系统对使用场所的适应性差、轨道占用空间大等缺点,同时避免使用单一AGV输送系统带来的输送效率较低、设备及维护成本较高等问题。  相似文献   
32.
VoIP (Voice over Internet Protocol), which provides voice calls as well as additional services at cheaper prices than PSTN (Public Switched Telephone Network), is gaining ground over the latter, which had been the dominant telephone network in the past. This kind of a VoIP service is evolving into a dedicated mVoIP service for the smartphone which allows calls to be made at cheap prices using a WiFi network, as the number of smartphone users is skyrocketing as of late. While an increase in the user base is expected for mVoIP, a packet network is an open network which means anyone can easily gain access and so there can be various problems. To mitigate this, in this paper an authentication system is designed which has an AA (Attribute Authority) server added to VoIP in order to increase security and discriminate user access. In this paper a system for addressing security vulnerabilities from the increase in the use of VoIP services and providing differentiated services according to user access privileges is designed. This paper is organized as follows: Chapter 1 gives the introduction; Chapter 2 is on related research; Chapter 3 describes the proposed technique and system; Chapter 4 implements the system and analyzes its the performance; and Chapter 5 gives the conclusions.  相似文献   
33.
We present an immaterial display that uses a generalized form of depth-fused 3D (DFD) rendering to create unencumbered 3D visuals. To accomplish this result, we demonstrate a DFD display simulator that extends the established depth-fused 3D principle by using screens in arbitrary configurations and from arbitrary viewpoints. The feasibility of the generalized DFD effect is established with a user study using the simulator. Based on these results, we developed a prototype display using one or two immaterial screens to create an unencumbered 3D visual that users can penetrate, examining the potential for direct walk-through and reach-through manipulation of the 3D scene. We evaluate the prototype system in formative and summative user studies and report the tolerance thresholds discovered for both tracking and projector errors.  相似文献   
34.
This paper presents a redundant multicast routing problem in multilayer networks that arises from large-scale distribution of realtime multicast data (e.g., Internet TV, videocasting, online games, stock quotes). Since these multicast services commonly operate in multilayer networks, the communications paths need to be robust against a single router or link failure as well as multiple such failures due to shared risk link groups (SRLGs). The main challenge of this multicast is to ensure the service availability and reliability using a path protection scheme, which is to find a redundant path that is SRLG-disjoint (diverse) from each working path. The objective of this problem is, therefore, to find two redundant multicast trees, each from one of the two redundant sources to every destination, at a minimum total communication cost whereas two paths from the two sources to every destination are guaranteed to be SRLG-diverse (i.e., links in the same risk group are disjoint). In this paper, we present two new mathematical programming models, edge-based and path-based, for the redundant multicast routing problem with SRLG-diverse constraints. Because the number of paths in path-based model grows exponentially with the network size, it is impossible to enumerate all possible paths in real life networks. We develop three approaches (probabilistic, non-dominated and nearly non-dominated) to generate potentially good paths that may be included in the path-based model. This study is motivated by emerging applications of internet-protocol TV service, and we evaluate the proposed approaches using real life network topologies. Our empirical results suggest that both models perform very well, and the nearly non-dominated path approach outperforms all other path generation approaches.  相似文献   
35.
Recently, requests for accurate process planning using simulation have been increasing in many engineering fields, including the shipbuilding industry. To date, designers of shipyards have developed in-house simulation systems or used commercial systems such as the QUEST by Dassault system when requests for the simulation of process planning have occurred. However, these methods have some limitations. First, it requires a lot of time to develop a new in-house simulation system. In addition, it is hard to reuse previously developed systems when developing a new one and it is also hard for these to satisfy the various needs of shipyards effectively.  相似文献   
36.
Abstract— The surface‐friction characteristics of the post‐bake temperature were compared to that of the rubbing condition on VA‐mode alignment films (AFs) using frictional force microscopy (FFM). The surface roughness and the surface frictional force increased when the temperature was elevated. However, the frictional asymmetry could not be detected by the frictional loop due to the instability of the side‐chain molecular arrangement. For the inter‐influences of the total friction and surface roughness, the density of the side chain was changed and it was intentionally rubbed for evaluation. The results showed that the total friction was higher when the rubbing was stronger and side‐chain density lower, and the surface roughness also increased in the same manner. This can be explained by the potential interaction due to the curved structure of the side‐chain surface that establishes the probe that is scanned and the top surface layer. In order to confirm the influence of the pre‐tilt angle on the tilt of the side chain, a test cell was produced under the same conditions and evaluated. The results showed that the pre‐tilt‐angle decreased according to the difference in density of the side chain and strength of rubbing after injecting liquid‐crystal (LC).  相似文献   
37.
杨建良  查开德 《自动化仪表》2000,21(3):19-20,30
介绍一种本征型强度调制绞合式光纤应变传感器,分析了该传感器的应变传感原理。理论与实验均表明,该传感器既能测量拉应变,又能测量压应变,对应变的响应具有良好的线性和重复性、灵敏度高、无迟滞现象。  相似文献   
38.
Efficient Algorithms for Image Template and Dictionary Matching   总被引:3,自引:0,他引:3  
Given a large text image and a small template image, the Template Matching Problem is that of finding every location within the text which looks like the pattern. This problem, which has received attention for low-level image processing, has been formalized by defining a distance metric between arrays of pixels and finding all subarrays of the large image which are within some threshold distance of the template. These so-called metric methods tends to be too slow for many applications, since evaluating the distance function can take too much time. We present a method for quickly eliminating most positions of the text from consideration as possible matches. The remaining candidate positions are then evaluated one by one against the template for a match. We are still guaranteed to find all matching positions, and our method gives significant speed-ups. Finally, we consider the problem of matching a dictionary of templates against a text. We present methods which are much faster than matching the templates individually against the input image.  相似文献   
39.
基于G2的实时生产调度系统研究   总被引:2,自引:0,他引:2  
该文以实时专家系统工具G2作为生产调度的平台 ,通过对G2中的知识表达、知识库管理以及实时推理等关键问题的探讨 ,以某钢厂炼钢车间调度为例 ,建立调度的复合知识模型 ,最终开发一个调度的原型系统 ,并给出仿真结果  相似文献   
40.
In distributed meeting applications, microphone arrays have been widely used to capture superior speech sound and perform speaker localization through sound source localization (SSL) and beamforming. This paper presents a unified maximum likelihood framework of these two techniques, and demonstrates how such a framework can be adapted to create efficient SSL and beamforming algorithms for reverberant rooms and unknown directional patterns of microphones. The proposed method is closely related to steered response power-based algorithms, which are known to work extremely well in real-world environments. We demonstrate the effectiveness of the proposed method on challenging synthetic and real-world datasets, including over six hours of recorded meetings.  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