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   3314篇
  免费   361篇
  国内免费   244篇
电工技术   180篇
综合类   368篇
化学工业   156篇
金属工艺   78篇
机械仪表   154篇
建筑科学   486篇
矿业工程   111篇
能源动力   133篇
轻工业   71篇
水利工程   177篇
石油天然气   150篇
武器工业   37篇
无线电   242篇
一般工业技术   433篇
冶金工业   178篇
原子能技术   64篇
自动化技术   901篇
  2024年   6篇
  2023年   24篇
  2022年   51篇
  2021年   65篇
  2020年   114篇
  2019年   96篇
  2018年   58篇
  2017年   95篇
  2016年   116篇
  2015年   131篇
  2014年   189篇
  2013年   256篇
  2012年   219篇
  2011年   258篇
  2010年   178篇
  2009年   219篇
  2008年   214篇
  2007年   227篇
  2006年   196篇
  2005年   159篇
  2004年   163篇
  2003年   121篇
  2002年   119篇
  2001年   109篇
  2000年   78篇
  1999年   68篇
  1998年   36篇
  1997年   53篇
  1996年   55篇
  1995年   37篇
  1994年   39篇
  1993年   28篇
  1992年   18篇
  1991年   25篇
  1990年   11篇
  1989年   11篇
  1988年   12篇
  1987年   5篇
  1986年   2篇
  1985年   10篇
  1984年   7篇
  1983年   3篇
  1982年   4篇
  1981年   5篇
  1980年   5篇
  1978年   3篇
  1977年   3篇
  1965年   2篇
  1957年   2篇
  1956年   3篇
排序方式: 共有3919条查询结果,搜索用时 78 毫秒
1.
2.
WRESTORE (Watershed Restoration Using Spatio-Temporal Optimization of Resources) is a web-based, participatory planning tool that can be used to engage with watershed stakeholder communities, and involve them in using science-based, human-guided, interactive simulation–optimization methods for designing potential conservation practices on their landscape. The underlying optimization algorithms, process simulation models, and interfaces allow users to not only spatially optimize the locations and types of new conservation practices based on quantifiable goals estimated by the dynamic simulation models, but also to include their personal subjective and/or unquantifiable criteria in the location and design of these practices. In this paper, we describe the software, interfaces, and architecture of WRESTORE, provide scenarios for implementing the WRESTORE tool in a watershed community's planning process, and discuss considerations for future developments.  相似文献   
3.
Power transformers are protected by different relays that operate independently. Malfunction of each relay has a major role in reducing the reliability of the protection system. In order to mitigate the main drawbacks of the power transformer relays, an overall protection scheme is presented in this paper. This scheme proposes a novel multi criterion algorithm using decision-making based on fuzzy logic. In this paper the outputs of restricted earth fault relay and a directional check unit, are combined with the output of the differential protection relay. Therefore, problems that are pertaining to independent operation of each relay have been mitigated and the relays cover protection blind spots of each other. The improved power transformer protection (IPTP) scheme enhances the sensitivity and reliability of the power transformer protection. Extensive simulations are used to measure the effectiveness and merit of the proposed IPTP relay. The above efforts result in a multi criteria approach for protection of power transformers.  相似文献   
4.
In this paper, we consider an integrated Resource Selection and Operation Sequences (iRS/OS) problem in Intelligent Manufacturing System (IMS). Several kinds of objectives are taken into account, in which the makespan for orders should be minimized; workloads among machine tools should be balanced; the total transition times between machines in a local plant should also be minimized. To solve this multiobjective iRS/OS model, a new two vectors-based coding approach has been proposed to improve the efficiency by designing a chromosome containing two kinds of information, i.e., operation sequences and machine selection. Using such kind of chromosome, we adapt multistage operation-based Genetic Algorithm (moGA) to find the Pareto optimal solutions. Moreover a special technique called left-shift hillclimber has been used as one kind of local search to improve the efficiency of our algorithm. Finally, the experimental results of several iRS/OS problems indicate that our proposed approach can obtain best solutions. Further more comparing with previous approaches, moGA performs better for finding Pareto solutions. Received: May 2005/Accepted: December 2005  相似文献   
5.
6.
硫酸厂主鼓风机的主要设计准则   总被引:1,自引:1,他引:0  
论述现代硫酸厂主鼓风机设计时必须考虑的关键因素,通过实例讨论操作费用与投资之间的平衡关系以及对装置竞争力的影响。建议在硫酸厂严酷的操作条件下改进风机特性,提高耐磨性并采用维修友好的设计。  相似文献   
7.
管道风险管理方法研究   总被引:6,自引:0,他引:6  
按照管道风险管理的流程分别对管道风险评价、风险控制和决策支持、效能测试和响应进行了论述。针对目前国内管道行业的情况,提出了进行管道风险评价的有效方法及维护措施。着重介绍了国外管道风险可接受标准的情况,作为国内制定管道风险评价标准的参考。  相似文献   
8.
本文分析并推导了应力波在弹性体中传播时,质点的运动速度、压力、位移及应力载波的聚流的形成与表达式.利用得到的公式描述了冲击能传感器的工作机理.给出了某风动工具的测试结果.  相似文献   
9.
In DS-WCDMA mobile systems such the UMTS, asynchronous cell site operation,assigning different long spreading code to each cell, yields the advantageof flexible system deployment. We can design an indoor system basedon an outdoor one. However, in general, much longer search time isrequired in asynchronous operation than in synchronous. This paperproposes three techniques to take decisions about synchronizationbased on observation of correlated signals. Classical decision criterialike maximum and threshold criterion are presented. A new decisioncriteria that we call Threshold&Max combined decision criteriais analyzed. The results of this new introduced technique is comparedwith the classical ones.  相似文献   
10.
根据化学事故危害的主要影响因素对化学事故进行危害评估,考查了危害纵深、人员杀伤率、危害地域估算、爆炸燃烧事故危害等内容。  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