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   5563篇
  免费   360篇
  国内免费   94篇
电工技术   82篇
综合类   183篇
化学工业   117篇
金属工艺   44篇
机械仪表   226篇
建筑科学   3071篇
矿业工程   190篇
能源动力   155篇
轻工业   69篇
水利工程   138篇
石油天然气   45篇
武器工业   11篇
无线电   169篇
一般工业技术   109篇
冶金工业   131篇
原子能技术   21篇
自动化技术   1256篇
  2023年   31篇
  2022年   56篇
  2021年   88篇
  2020年   120篇
  2019年   72篇
  2018年   85篇
  2017年   79篇
  2016年   191篇
  2015年   228篇
  2014年   343篇
  2013年   382篇
  2012年   298篇
  2011年   429篇
  2010年   295篇
  2009年   367篇
  2008年   328篇
  2007年   415篇
  2006年   400篇
  2005年   327篇
  2004年   294篇
  2003年   267篇
  2002年   176篇
  2001年   144篇
  2000年   120篇
  1999年   85篇
  1998年   84篇
  1997年   52篇
  1996年   49篇
  1995年   31篇
  1994年   20篇
  1993年   20篇
  1992年   12篇
  1991年   17篇
  1990年   11篇
  1989年   8篇
  1988年   5篇
  1987年   5篇
  1986年   23篇
  1985年   9篇
  1984年   10篇
  1983年   9篇
  1982年   8篇
  1981年   2篇
  1979年   5篇
  1977年   2篇
  1973年   2篇
  1968年   2篇
  1965年   1篇
  1958年   2篇
  1956年   1篇
排序方式: 共有6017条查询结果,搜索用时 7 毫秒
1.
The proposed work involves the multiobjective PSO based adaption of optimal neural network topology for the classification of multispectral satellite images. It is per pixel supervised classification using spectral bands (original feature space). This paper also presents a thorough experimental analysis to investigate the behavior of neural network classifier for given problem. Based on 1050 number of experiments, we conclude that following two critical issues needs to be addressed: (1) selection of most discriminative spectral bands and (2) determination of optimal number of nodes in hidden layer. We propose new methodology based on multiobjective particle swarm optimization (MOPSO) technique to determine discriminative spectral bands and the number of hidden layer node simultaneously. The accuracy with neural network structure thus obtained is compared with that of traditional classifiers like MLC and Euclidean classifier. The performance of proposed classifier is evaluated quantitatively using Xie-Beni and β indexes. The result shows the superiority of the proposed method to the conventional one.  相似文献   
2.
利用TM资料测量毛乌素沙地面积的方法和结果   总被引:1,自引:0,他引:1  
利用1:25万陆地卫星TM资料和地形图,在GIS支持下,建立毛乌素沙地图形数据库,对毛乌素沙地目前流沙分布的范围进行了调查研究。重.资、介绍了利用陆地卫星TM资料对毛乌素沙地的面积进行测童计算的技术和方法,给出了最新测贡得到的毛乌素沙地全区总面积和分布于各旗县的沙地面积数据。  相似文献   
3.
台北101层国际金融中心之结构施工技术与其设计考量概述   总被引:1,自引:0,他引:1  
本文旨在简要说明目前正在施工中之超高层大楼—台北国际金融中心之结构系统、钢结构工程、钢筋混凝土工程基础与深开挖工程等特殊施工技术,并佐以相关之设计考量与施工规划概要,以供工程界做参考。  相似文献   
4.
Based on an idea introduced by Benjamin and Cornell (1970. Probability, statistics and decision for civil engineers. New York: McGaw Hill) and previous works by the authors it is demonstrated how condition indicators may be formulated for the general purpose of quality control and for assessment and inspection planning in particular. The formulation facilitates quality control based on sampling of indirect information about the condition of the considered components. This allows for a Bayesian formulation of the indicators whereby the experience and expertise of the inspection personnel may be fully utilized and consistently updated as frequentistic information is collected. The approach is illustrated on an example considering a concrete structure subject to corrosion. It is shown how half-cell potential measurements may be utilized to update the probability of excessive repair after 50 years. Furthermore in the same example it is shown how the concept of condition indicators might be applied to develop a cost optimal maintenance strategy composed of preventive and corrective repair measures.  相似文献   
5.
Struts是基于模型视图控制体系(MVC)的Web应用框架。详细介绍了基于MVC体系的Struts工作原理,探讨应用Struts框架构建企业级应用系统的步骤及方法。给出了基于Struts的科研资源计划系(SRRPS)的设计实现,结果表明Struts框架能极大地提高系统的可扩展性、可重用性及可维护性。  相似文献   
6.
Planning is an essential function of project management. Yet, many small- and medium-sized contractors do a relatively poor job of operational planning. Better prebid plans will reduce costs, shorten schedules, and improve labor productivity. Unfortunately, the published literature offers little guidance for smaller contractors on what constitutes effective planning. Most papers describe planning as a macrolevel process for owners. Most emphasize scope definition for industrial projects. This paper describes a microlevel planning process for contractors. It consists of eight steps which are: (1) assess contract risks; (2) develop a preliminary execution plan; (3) develop site layout plans; (4) identify the sequences that are essential-to-success; (5) develop detailed operational plans; (6) develop proactive strategies to assure construction input into design; (7) revise the preliminary plan; and (8) communicate and enforce the plan. The entire process is illustrated with a case study project and is fully illustrated with figures which show how to integrate the work of multiple contractors, keep key resources (crews or equipment) fully engaged with no downtime, provide time buffers so the work of follow on crews can be efficiently done, expedite the schedule using multiple work stations and concurrent work, ways to communicate the work plan to the superintendent and foremen, and how to assess the feasibility of various work methods. The steps are easy to understand and implement. They will yield immediate positive results.  相似文献   
7.
用于钻水平井的低密度水包油乳化钻井液   总被引:4,自引:0,他引:4  
续丽琼  赵翰宝 《油田化学》1993,10(3):204-208
针对任平1井水平钻井的特点,研制了一种低密度、高油水比的水包油乳化钻井液。考察了乳化剂、增粘剂和配制工艺对乳状液性能的影响,评定了钻井液性能,介绍了现场应用情况。该钻井液性能稳定,润滑性好,净化井眼的能力强,能满足水平段钻井的要求。  相似文献   
8.
Solid-waste management, and in particular the disposal of used packaging, is currently the subject of much topical debate. This is driven by both consumer and legislative pressures. Consumers see used packaging as a highly visible element of municipal solid waste, complaining of excessive packaging and low levels of recycling. Legislators, perhaps in pandering to the views expressed by consumer bodies, have been active within the CEC and individual Member States by introducing (or proposing) legislation or similar regulatory tools and targets to facilitate a greater diversion of used packaging from disposal by landfill to alternative solid-waste management practices, in particular recycling, which are widely accepted to have a lower impact on the environment. In this paper the relative environmental profiles of pursuing alternative solid-waste management practices to disposal by landfill are explored, focusing not just on solid waste per se but also on associated considerations of energy consumption and emissions, which are invariably overlooked as factors contributing to the environmental impact of solid-waste management practices.  相似文献   
9.
借鉴英国经验完善中国土地产权流转   总被引:1,自引:0,他引:1  
本文在简要介绍中、英两国土地产权制度和土地产权流转的基础上,分析了我国土地产权流转过程中出现的问题,如征地过程中的赔偿过低且不完善、国有土地拆迁补偿不公以及补偿的分配方式不公平等问题。由于英国在土地制度方面与中国的相似性,文章借鉴英国土地补偿中的补偿金与改善金相结合原则、土地使用权的租赁行为以及开发收益回馈社会的方法,为完善和健全我国的土地产权流转机制提出措施和建议。  相似文献   
10.
柘树青青     
晓芙 《中国园林》2004,20(10):75-76
柘树是中华大地上最古老的树种之一,柘木是制弓的良材,汁能染赤黄色,叶可以饲蚕,皮、茎、叶、果实均可入药.早在远古时代,柘与人民的生活就有着密切的关系.历史上,柘就被用来命名后宫,柘枝还被用作曲调、歌舞之名.  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