全文获取类型
收费全文 | 5982篇 |
免费 | 254篇 |
国内免费 | 274篇 |
专业分类
电工技术 | 152篇 |
技术理论 | 10篇 |
综合类 | 286篇 |
化学工业 | 104篇 |
金属工艺 | 41篇 |
机械仪表 | 150篇 |
建筑科学 | 1163篇 |
矿业工程 | 96篇 |
能源动力 | 93篇 |
轻工业 | 27篇 |
水利工程 | 2756篇 |
石油天然气 | 149篇 |
武器工业 | 11篇 |
无线电 | 135篇 |
一般工业技术 | 223篇 |
冶金工业 | 408篇 |
原子能技术 | 27篇 |
自动化技术 | 679篇 |
出版年
2024年 | 5篇 |
2023年 | 34篇 |
2022年 | 62篇 |
2021年 | 62篇 |
2020年 | 120篇 |
2019年 | 80篇 |
2018年 | 111篇 |
2017年 | 122篇 |
2016年 | 125篇 |
2015年 | 143篇 |
2014年 | 409篇 |
2013年 | 428篇 |
2012年 | 373篇 |
2011年 | 538篇 |
2010年 | 317篇 |
2009年 | 323篇 |
2008年 | 311篇 |
2007年 | 354篇 |
2006年 | 346篇 |
2005年 | 373篇 |
2004年 | 290篇 |
2003年 | 294篇 |
2002年 | 247篇 |
2001年 | 166篇 |
2000年 | 152篇 |
1999年 | 176篇 |
1998年 | 155篇 |
1997年 | 117篇 |
1996年 | 81篇 |
1995年 | 60篇 |
1994年 | 39篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 13篇 |
1985年 | 3篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1966年 | 6篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有6510条查询结果,搜索用时 0 毫秒
1.
High dimensionality in real-world multi-reservoir systems greatly hinders the application and popularity of evolutionary algorithms, especially for systems with heterogeneous units. An efficient hierarchical optimization framework is presented for search space reduction, determining the best water distributions, not only between cascade reservoirs, but also among different types of hydropower units. The framework is applied to the Three Gorges Project (TGP) system and the results demonstrate that the difficulties of multi-reservoir optimization caused by high dimensionality can be effectively solved by the proposed hierarchical method. For the day studied, power output could be increased by 6.79 GWh using an optimal decision with the same amount of water actually used; while the same amount of power could be generated with 2.59 × 107 m3 less water compared to the historical policy. The methodology proposed is general in that it can be used for other reservoir systems and other types of heterogeneous unit generators. 相似文献
2.
随着BIM技术的进步,建筑行业越来越重视BIM技术的应用,并在应用过程中取得一定的成效。本文从工程造价决策、设计、招投标、施工、竣工五个阶段阐述BIM技术在建筑工程造价中的应用对策。 相似文献
3.
Risk allocation decisions are of critical importance in project management. The present study proposes an explanation for how risk allocation in a contract motivates a contractor to cooperate with a project owner. Theories of risk allocation and trust were used to motivate the research. Using a survey methodology, we collected data concerning 124 construction projects in China. We found that risk allocation influenced the contractor’s role behavior through the contractor’s feeling of being trusted but not the contractor’s trust in the owner. Feeling of being trusted partially mediated the effect of risk allocation on the contractor’s in-role (i.e., contractual) behavior and fully mediated the effect on extra-role behavior. The study introduces a social and psychological view of the impacts of risk allocation to the project and engineering management literature. We contribute to theory by arguing and demonstrating the mediating effect of trust on the relationship between risk allocation and contractor behavior. From a practical standpoint, we conclude that contractual risk allocation has a significant impact on building a trusting relationship between owners and contractors and that contractors who feel trusted perform both contractually mandated actions and actions external to the contract more diligently, resulting in the likelihood of improved outcomes for both parties. 相似文献
4.
威海市污水处理深海排放工程是为改善其水域环境而建设的一英包括市区排水系统,污水预处理厂,输水管道和海洋放流管系统在内的完整而典型的工程,因此其工程设计扣的经验将会对同类项目的设计与工程建设有所借鉴。 相似文献
5.
三峡船闸深槽开挖与锚固工程量大,工期紧,施工强度高,施工难度大。因此,合理的施工程序有利于边坡稳定和施工,是快速和高质量施工的关键。分析了永久船闸直立墙基坑开挖与锚固施工程序的复杂性和进行研究的必要性。介绍了设计阶段研究船闸开挖与锚固的施工程序。对施工过程中研究施工程序时考虑的因素,研究的主要内容以及实际采用的施工程序作了简要的分析,归纳和总结。 相似文献
6.
7.
一级开发大柳树高坝原始库容比二级开发小观音高坝多 4 0亿m3 ,库容大带来的好处体现在 5~ 7月可多向下游增供水量 ,缓解下游河道断流 ;延长泄放清水时间 ;增加发电效益 ;满足宁蒙河段防凌要求 ;增加汛期集中泄水 ,减缓下游河道淤积萎缩 ;满足南水北调西线工程水量调节要求等。为了更好优化配置黄河水资源 ,从全局和长远利益考虑 ,应采用一级开发方案 ,修建大柳树高坝大库 相似文献
8.
9.
Central to cost-based competition is the capability to accurately predict the cost of delivering a project. Most literature on cost estimation focuses on specific estimation methods as generic techniques and little attention has been paid to the unique requirements at each project stage. This note attempts to identify the critical factors for effective estimation at various stages of typical construction projects. Drawing from organization control theory and cost estimating literature, this note develops a theoretical framework that identifies the critical factors for effective cost estimation during each project phase of a conventional construction project. The underlying logic is that as a cost estimating effort progresses, both task programmability and output measurability improve. As a result, control effort will shift from input-oriented control to a combination of output and behavior control. 相似文献
10.
Hong Long Chen 《Canadian Metallurgical Quarterly》2007,23(4):171-181
The difficulty in applying the standard curve (S-curve) and cost-schedule integration (CSI) techniques for company-level cost flow forecasting in a project-based industry is the prerequisite of forecasting future unknown individual projects and contract classifications. By analyzing cost flows at the company level through a pool of macroeconomic and internal financial data, this paper proposes an innovative approach to firm-specific model estimation. First, a series of data transformations introduce linear relationships between cost, macroeconomic, and internal financial variables. Second, multivariate regression analysis is employed for initial model building. Third, for the purposes of model restructuring, a subsequent application of Yule–Walker estimates and incomplete principal component analysis is used. This paper uses a sample of four project-based construction firms to demonstrate model performance. Using this methodology, mean absolute percentage error (MAPE) values of the forecasting models range from 0.27 to 0.60%. As such, the transformed cost, macroeconomic, internal financial data could strongly predict company-level cost flow forecasting. While converting the predicted cumulative cost data to periodic cost flows, the MAPE values were augmented, ranging from 7.04 to 17.55%, thus, requiring future research. 相似文献