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   328104篇
  免费   29556篇
  国内免费   18565篇
电工技术   27841篇
技术理论   51篇
综合类   42499篇
化学工业   39160篇
金属工艺   13531篇
机械仪表   17783篇
建筑科学   42038篇
矿业工程   17201篇
能源动力   10591篇
轻工业   17719篇
水利工程   15922篇
石油天然气   14330篇
武器工业   3310篇
无线电   22340篇
一般工业技术   25847篇
冶金工业   18730篇
原子能技术   3987篇
自动化技术   43345篇
  2024年   1185篇
  2023年   3617篇
  2022年   6884篇
  2021年   8248篇
  2020年   8910篇
  2019年   7582篇
  2018年   7176篇
  2017年   8817篇
  2016年   10008篇
  2015年   10977篇
  2014年   18853篇
  2013年   18028篇
  2012年   22249篇
  2011年   23602篇
  2010年   18421篇
  2009年   19257篇
  2008年   18017篇
  2007年   22960篇
  2006年   21543篇
  2005年   18638篇
  2004年   15870篇
  2003年   14163篇
  2002年   11745篇
  2001年   9946篇
  2000年   8420篇
  1999年   7006篇
  1998年   5305篇
  1997年   4579篇
  1996年   4156篇
  1995年   3548篇
  1994年   3196篇
  1993年   2386篇
  1992年   2075篇
  1991年   1555篇
  1990年   1370篇
  1989年   1201篇
  1988年   944篇
  1987年   664篇
  1986年   501篇
  1985年   418篇
  1984年   378篇
  1983年   271篇
  1982年   249篇
  1981年   184篇
  1980年   149篇
  1979年   126篇
  1978年   68篇
  1977年   76篇
  1975年   62篇
  1959年   62篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) X¯ scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA X¯ scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA X¯ scheme.  相似文献   
2.
In practical applications of structural health monitoring technology, a large number of distributed sensors are usually adopted to monitor the big dimension structures and different kinds of damage. The monitored structures are usually divided into different sub-structures and monitored by different sensor sets. Under this situation, how to manage the distributed sensor set and fuse different methods to obtain a fast and accurate evaluation result is an important problem to be addressed deeply. In the paper, a multi-agent fusion and coordination system is presented to deal with the damage identification for the strain distribution and joint failure in the large structure. Firstly, the monitoring system is adopted to distributedly monitor two kinds of damages, and it self-judges whether the static load happens in the monitored sub-region, and focuses on the static load on the sub-region boundary to obtain the sensor network information with blackboard model. Then, the improved contract net protocol is used to dynamically distribute the damage evaluation module for monitoring two kinds of damage uninterruptedly. Lastly, a reliable assessment for the whole structure is given by combing various heterogeneous classifiers strengths with voting-based fusion. The proposed multi-agent system is illustrated through a large aerospace aluminum plate structure experiment. The result shows that the method can significantly improve the monitoring performance for the large-scale structure.  相似文献   
3.
The proliferating need for sustainability intervention in food grain transportation planning is anchoring the attention of researchers in the interests of stakeholders and environment at large. Uncertainty associated with food grain supply further intensifies the problem steering the need for designing robust, cost-efficient and sustainable models. In line with this, this paper aims to develop a robust and sustainable intermodal transportation model to facilitate single type of food grain commodity shipments while considering procurement uncertainty, greenhouse gas emissions, and intentional hub disruption. The problem is designed as a mixed integer non-linear robust optimisation model on a hub and spoke network for evaluating near optimal shipment quantity, route selection and hub location decisions. The robust optimisation approach considers minimisation of total relative regret associated with total cost subject to several real-time constraints. A version of Particle Swarm Optimisation with Differential Evolution is proposed to tackle the resulting NP-hard problem. The model is tested with two other state-of the art meta-heuristics for small, medium, and large datasets subject to different procurement scenarios inspired from real time food grain operations in Indian context. Finally, the solution is evaluated with respect to total cost, model and solution robustness for all instances.  相似文献   
4.
In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals.  相似文献   
5.
高素质人才培养是我国可持续发展战略、科教兴国战略以及人才强国战略等多项发展战略的一项基础性工程。本文针对中医药类院校程序设计类课程实践教学模式单一等教学实际,以“学科竞赛”为平台,“赛教结合”为理念,以《C语言程序设计》为例,从现存问题、赛教结合模式的引入、建立实施及其评价机制4个方面展开阐述,旨在提高学生学习积极性和能力。  相似文献   
6.
本文以云杉八齿小蠹Ips typographus Linnaeus为例,经标本选取,观察虫体整体形态,绘制整体结构草图,电子显微镜观察局部、得到局部数字图像,分别建立虫体每一部分的高精度细节。把模型每部分拼装在一起组成整体模型,构建出了云杉八齿小蠹三维虚拟昆虫数字化模型。  相似文献   
7.
SDN中基于KMOBPSO的高可靠性控制器部署算法   总被引:1,自引:0,他引:1  
针对SDN中控制器系统的单节点故障问题,兼顾系统成本和系统时延,应用N+1冗余备份模型来提高SDN控制器部署的可靠性,并将其抽象为多目标优化问题.同时,提出了一种融合K-means聚类算法和遗传算子的多目标二进制粒子群算法——KMOBPSO算法,以求解SDN控制器高可靠性部署问题的解.仿真结果表明,所提算法具有求解精度高、分布均匀、沿Pareto前沿面覆盖广的特点,能够显著提高SDN中控制器部署的可靠性.  相似文献   
8.
9.
10.
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