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   436篇
  免费   7篇
财政金融   2篇
工业经济   42篇
计划管理   28篇
经济学   8篇
综合类   2篇
运输经济   6篇
贸易经济   25篇
农业经济   2篇
经济概况   4篇
水利工程   324篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   6篇
  2012年   7篇
  2011年   51篇
  2010年   30篇
  2009年   62篇
  2008年   9篇
  2007年   2篇
  2006年   6篇
  2005年   27篇
  2004年   91篇
  2003年   9篇
  2002年   4篇
  2001年   14篇
  2000年   3篇
  1999年   15篇
  1998年   20篇
  1997年   12篇
  1996年   2篇
  1995年   1篇
  1994年   4篇
  1993年   22篇
  1992年   24篇
  1991年   5篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1986年   1篇
  1979年   1篇
排序方式: 共有443条查询结果,搜索用时 31 毫秒
1.
党的十六大报告提出,要“实施海洋开发,搞好国土资源的综合整治”。天津市委八届三次全会提出“三步走”战略目标,把开发利用海洋、发展海洋经济作为实现奋斗目标的五大战略举措之一。为此,天津市滨海新区管委会就天津如何开发利用海洋资源、大力发展海洋经济,与有关方面开展了  相似文献   
2.
Based on model test,the statistical distribution of extreme values of wave-current in-line forces acting on vertical circular cylinder is analyzed in this paper.It is shownthat the results calculated by the simplified method,proposed by authors,agree well with the testdata;Weibull distribution is also adoptable in the region of high KC number, and the shapeparameter a and scale parameter β are related well with KC number respectively.  相似文献   
3.
1. INTRODUCTIONThemaingoalofthispaperistoexplorethepossibilitytolearnmoreaboutthemechanismofturbulentboundarylayerflowinteractionsanditseffectsoncompliantwallperformance.Therearecertainprerequisiteconditionstofurtherthestudyonthemechanism,i.e.theco…  相似文献   
4.
吴岭水库土坝渗流及坝坡稳定性分析   总被引:3,自引:0,他引:3  
本文对湖北省京山县吴岭水库土坝进行了有限元渗流计算和坝坡稳定性计算,在分析大坝基础部位的残坡积土、强风化砂岩的强透水性和下游排水体对于大坝渗流场的影响的基础上,得出渗流是引起下游坝坡不稳定的主要因素,为大坝的加固处理提供了理论依据,也可供同类土坝设计时参考。  相似文献   
5.
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion.  相似文献   
6.
This paper will introduce experimental studies and numerical calculation onturbulent boundary layer of water flow along curved surface in our country in recent years.Onthe basis of the experimental studies,the effects of curvature and roughness on velocitydistribution and pressure distribution and the change of turbulent flow boundary layer onoverflow bucket concave surface is discussed.We proposed the empirical formula of velocity,pressure and the change of turbulent flow boundary layer on outlet bucket concave.According tothe momentum principle,we have deduced the momentum integral equation full water depthboundary layer and using the element as control unit inside the boundary layer on concavesurface of bucket.Combining with continuity equation,we have computed the boundary layerdevelopment on the bucket of a spillway.Compared with the field experimental data,thecalculation results are available.Under polar coordinates,a mathematical model for simulatingtime-averaged flow characteristics in concave surface of bucket is established.The turbulent flowfield on concave surface of bucket is calculated by SIMPLE method and this mathematicalmodel.The flow velocity field,pressure field,distribution of turbulent kinetic energy,distribution of turbulent energy dissipating rate and distribution of shear stress are available.Thecalculation value is consistent with measured test data.  相似文献   
7.
1 . INTRODUCTIONWhenhigh speedairfloworcurrentpassesovergapsorcavitiesinaflatplate ,self excitedoscillationsmayoccur ,leadingtodramaticpressureandvelocityfluctuationandintensivenoise .Thesephenomenamayappearinmanyengineeringapplications .Forexample ,weaponb…  相似文献   
8.
A generic characterization of the dynamics of market penetration by technological artifacts is here formulated on the basis of entry rate and exit rate considerations. It is shown that low-order reductions lead to the biologically based logistic dynamic, which—by empirical fit—has been found to be in very good agreement with numerous specific cases. In addition to the derivational justification of the logistic for artifact market penetration, we find that but a small number of parameters are involved in these autonomous characterizations suggesting therefore that market penetration may well be reduced to a similarly small number of dominant operative processes. Some nonautonomous extensions are also discussed.  相似文献   
9.
在市场经济条件下,随着水利工程建设市场的不断规范和完善,招标代理机构如何在市场竞争中开展招标代理业务,其自身建设就显得尤为重要。现结合南水北调工程实际,提出了招标代理机构应从法律意识、诚实信用、专业特长、激励机制和沟通协调等5个方面加强自身建设,以便能在南水北调工程建设中更好地发挥作用。  相似文献   
10.
It is mentioned in this paper that the adjustment of flow structure occurs when themain-flow swings.The changes of turbulence structure and flow energy loss in the indoor rivermodel are measured.The experimental data are presented for the first time for the further studyof complicated river flow structure.  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