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   2005篇
  免费   61篇
  国内免费   49篇
财政金融   183篇
工业经济   72篇
计划管理   385篇
经济学   292篇
综合类   249篇
运输经济   38篇
旅游经济   78篇
贸易经济   240篇
农业经济   133篇
经济概况   145篇
水利工程   300篇
  2024年   4篇
  2023年   22篇
  2022年   20篇
  2021年   35篇
  2020年   82篇
  2019年   62篇
  2018年   58篇
  2017年   84篇
  2016年   62篇
  2015年   67篇
  2014年   121篇
  2013年   211篇
  2012年   177篇
  2011年   166篇
  2010年   114篇
  2009年   125篇
  2008年   126篇
  2007年   126篇
  2006年   101篇
  2005年   76篇
  2004年   65篇
  2003年   41篇
  2002年   28篇
  2001年   26篇
  2000年   28篇
  1999年   15篇
  1998年   13篇
  1997年   15篇
  1996年   9篇
  1995年   5篇
  1994年   3篇
  1993年   4篇
  1992年   5篇
  1991年   5篇
  1990年   3篇
  1989年   1篇
  1988年   3篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
排序方式: 共有2115条查询结果,搜索用时 968 毫秒
31.
The Jackfish Bay Remedial Action Plan is the first of Lake Superior's Areas of Concern (AOCs) to consider recognition as an Area in Recovery (AiR). As a result of a high degree of complexity and uncertainty, ecosystem recovery in Jackfish Bay has been determined using a combination of regulatory policies and scientific evidence and extensive public and expert-based decision making. As a result, the conceptualization of the AiR status in Jackfish Bay has been developed with the adaptive management and the ecosystem approach, which provide the basic principles of assessing, monitoring, and managing the Area of Concern. To determine the status of beneficial use impairments caused by effluent from the Terrace Bay Pulp Inc., three public advisory committees—an academic panel of experts, a government technical review committee, and the Jackfish Bay Public Area in Recovery Review Committee (PARRC)—reviewed relevant scientific data and documents, including peer-reviewed publications, to assess changes in pollution levels in Jackfish Bay and improvements to aquatic, biotic, and benthic environments of the bay. The public decision-making process concluded with recommendations by the PARRC to develop a systematic monitoring program so that the ecosystem recovery process in the bay could be assessed on a continued basis, leading to its eventual delisting as an AOC. The entire process provides an example of blending science and public policies for remediation of a degraded ecosystem on the Great Lakes.  相似文献   
32.
基于拉格朗日粒子追踪的渤海冬季与夏季环流及影响因素   总被引:1,自引:0,他引:1  
基于三维非结构有限体积海洋模式(FVCOM)对渤海环流进行了数值模拟研究.数值模拟中采用三角形网格,以更好地拟合渤海复杂的岸线边界.潮位、潮流、温盐模拟结果验证良好.通过对粒子的拉格朗日追踪研究了渤海冬季与夏季环流及潮、风、海气热交换和人海径流对渤海环流的影响.研究表明:粒子输移存在明显的三维结构;与渤海中部及海峡附近...  相似文献   
33.
针对坝王河流域忽明忽暗、明伏交替、落水洞遍布、地下暗河系统发育等强喀斯特特点,拟对羡塘至大井、小井河段的开发采取分段开发的思路,上河段为合理规避河段喀斯特渗漏问题,采用长隧洞引水方式;下河段为避开地下暗河系统和渗漏河段,选择成库条件较为可靠的坝址和引水线路较短的开发方案.其工程经验可供类似流域开发借鉴.  相似文献   
34.
Abstract

Water is an important factor in conflicts among stakeholders at the local, regional, and even international level. Water conflicts have taken many forms, but they almost always arise from the fact that the freshwater resources of the world are not partitioned to match the political borders, nor are they evenly distributed in space and time. Two or more countries share the watersheds of 261 major rivers and nearly half of the land area of the world is in international river basins. Water has been used as a military and political goal. Water has been a weapon of war, and water systems have been targets during the war. A systemic approach has been taken in this research to approach resolution of conflicts over water. By helping stakeholders to explore and resolve the underlying structural causes of conflict our approach offers a significant opportunity for its resolution. We define the five main functional activities for assisting the conflict resolution process as: (i) communication; (ii) problem formulation; (iii) data gathering and information generation; (iv) information sharing; and (v) evaluation of consequences. A computerized technical support is developed in the form of the Conflict Resolution Support System (CRSS) for implementation of a systemic approach to water conflicts. Its principal components include an artificial intelligence-based communication system, a database management system, and a model base management system. At this stage of the development, the model base management system consists of tools for multipurpose reservoir operation, river flow routing, multi-criteria decision-making, spatial data analysis, and other general utilities. A hypothetical river basin with potential conflict between stakeholders with respect to water sharing and flood control is used to demonstrate the utility of the new approach and the computer system developed for its implementation.  相似文献   
35.
从水的生态服务功能的机理出发,深入剖析了其内涵与水的两层次生态服务结构,并在此基础上构建评价水的生态服务功能的指标体系,介绍了评价流域水的生态服务功能的主要方法;最后提出了维系流域水的生态服务功能主要思路与手段,为水的生态服务功能研究提供了新思路与新方法。  相似文献   
36.
A physical approach of the wind power prediction based on the CFD pre-calculated flow fields is proposed in this paper. The flow fields are obtained based on a steady CFD model with the discrete inflow wind conditions as the boundary conditions, and a database is established containing the important parameters including the inflow wind conditions, the flow fields and the corresponding wind power for each wind turbine. The power is predicted via the database by taking the Numerical Weather Prediction (NWP) wind as the input data. In order to evaluate the approach, the short-term wind power prediction for an actual wind farm is conducted as an example during the period of the year 2010. Compared with the measured power, the predicted results enjoy a high accuracy with the annual Root Mean Square Error (RMSE) of 15.2% and the annual MAE of 10.80%. A good performance is shown in predicting the wind power’s changing trend. This approach is independent of the historical data and can be widely used for all kinds of wind farms including the newly-built wind farms. At the same time, it does not take much computation time while it captures the local air flows more precisely by the CFD model. So it is especially practical for engineering projects.  相似文献   
37.
基于却荷岩体力学理论和方法,采用大型岩土工程数值分析软件(FLAC3 D ),对小湾水电站高水位运行大坝与边坡相互作用进行了研究,建立了其坝肩边坡和拱坝三维有限元模型。根据施工过程,在初始工况、开挖工况、却荷工况、加固工况基础上,考虑了正常蓄水位情况时拱端推力、坝肩边坡的应力和位移变化规律,并与其监测值进行了对比。结果表明计算值与监测值十分吻合,论证了坝体设计的合理性,为小湾水电站高水位安全运营提供了一定的参考依据。  相似文献   
38.
桃花江旅游景观船闸在布置上因受到枢纽地形与河道防洪的限制,难以满足规范要求.采用几何比尺为1∶25的整体水工模型进行了试验研究,2座枢纽的控制运行条件均为最高通航水位组合,主河道中流速较大,特别是上下游口门处引航道的横向流速较大,不能满足规范要求.修改方案主要通过减小2座船闸上下游引航道与桃花江主河道夹角,并对口门附近地形进行了相应的疏浚.试验结果表明,修改方案有效降低了2座船闸上游口门处横向流速等不利因素.  相似文献   
39.
某水电站引水线路通过一高阶地前缘滑坡体,前期勘察时对该滑坡稳定性进行过稳定分析,但未作有效支挡处理,渠道施工开挖2 a后发生滑动,对渠道造成严重破坏,并推迟发电日期。滑动后对滑坡体进行了勘察和稳定性分析,估算出支挡结构断面处的下滑推力,并提出治理建议,为滑坡治理设计提供了可靠依据。  相似文献   
40.
内部评级法在国内商业银行实施的本土化研究   总被引:1,自引:0,他引:1  
内部评级法的实施需要建立在一定的前提基础之上,中国目前的实施条件还存在一定的缺陷,因此如何在内部评级体系的构建过程中体现本土化的原则将成为有效实施的关键。中国特有的金融生态决定了地区之间的金融风险差异较大,因此在具体实施过程中,应将地区金融风险差异作为调整系数对内部评级法的评级结果进行调整。中国的商业银行尚处于内部评级法实施的准备或开始阶段,受实施条件和金融生态的限制,本土化将是一个长期的、渐进的创新过程。本土化并不仅仅是内部评级法相关标准的本地化应用,同时也要求在这一过程中有创造性地发挥内部评级法对银行风险管理的积极作用。  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