全文获取类型
收费全文 | 1504篇 |
免费 | 54篇 |
专业分类
公路运输 | 269篇 |
综合类 | 682篇 |
水路运输 | 370篇 |
铁路运输 | 137篇 |
综合运输 | 100篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 24篇 |
2021年 | 30篇 |
2020年 | 25篇 |
2019年 | 34篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 45篇 |
2015年 | 49篇 |
2014年 | 83篇 |
2013年 | 78篇 |
2012年 | 98篇 |
2011年 | 118篇 |
2010年 | 96篇 |
2009年 | 107篇 |
2008年 | 104篇 |
2007年 | 141篇 |
2006年 | 122篇 |
2005年 | 80篇 |
2004年 | 60篇 |
2003年 | 37篇 |
2002年 | 34篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有1558条查询结果,搜索用时 15 毫秒
881.
用区间代数能表示不确定的时态关系,可以方便地应用于时态推理,表达能力强。将区间代数及区间矩阵中有端点相等的基本关系去掉,只保留现实世界中真正可能发生的基本关系,大大降低了问题的复杂性,然后,对每个原子矩阵建立一个特征集,用特征集的并运算来取代矩阵的复合运算,提高了计算效率。 相似文献
882.
袁永新 《江苏科技大学学报(社会科学版)》2008,22(2):83-86
考虑矩阵方程AXB=D在约束条件X([1r∶,1∶s])=X0下的可解性问题,其中X([1∶r,1∶s])表示矩阵X的前r行,前s列组成的子矩阵。给出了此问题有解的充分必要条件,并在有解时给出了通解的显式表示。 相似文献
883.
Major accidental oil spills still affect ecologically and economically sensitive marine areas and shorelines, even though environmental programs and policies have led to an increase of ship safety measures. The aim of decision making during oil spill response management is to minimize pollution effects on coastal areas, once spills occur. However, limited equipments or options prevent such a globally satisfying combat strategy. Thus, often preferences between different coastal areas or uses, respectively, have to be made in an operational way. Such a management issue is here taken as a multigroup multicriteria decision-making problem involving a variety of stakeholders and natural dynamic environments. For solving such a complex problem, this article proposes a second order fuzzy comprehensive evaluation (FCE) model, which takes the influence of multiple criteria and the knowledge of different interested groups into account and further provides a basis for simulating a voting-based decision process. With the combination of oil fate simulations and FCE technique, managers are able to realize an integrated management for oil spill. Through a case study of the Prestige accident off the Spanish coast in 2002, it is demonstrated that the model provides a simple, effective and adaptable method to solve operational management problems related to complex human nature interactions as realized during oil spill management. Moreover, a series of analyses and comparisons are focused on to explore potentials and limitations of the FCE for further applications in the field of multigroup multicriteria decision making. 相似文献
884.
Coastal management information is frequently communicated to stakeholders and the public through complicated management documents and engineering plans. With the recognition that public involvement in coastal decision-making processes should be widened have come calls to develop new techniques to communicate complicated coastal information. Using Virtual Reality Geographical Information Systems and visualization packages, such information may be presented using formats more suitable for public consultation and information dissemination exercises than those currently employed. Using a site on the north Norfolk coast of England, an integrated Geographical Information Systems based methodology is presented that allows the visualization of proposed coastal management interventions. Visualizations have been produced that can be published in traditional paper-based management documents, or electronically. The different visualizations are compared and the technical issues surrounding their use discussed. It is argued that the methodology has clear advantages over traditional communication methods, although further research is necessary to determine how it may be practically employed by coastal managers. 相似文献
885.
886.
887.
Sucharita Gopal Les Kaufman Valerie Pasquarella Marta Ribera Chris Holden Burton Shank 《Coastal management》2015,43(3):217-237
The livelihood of coastal communities is directly linked to the health of intertidal and marine ecosystems. Coastal zones and marine areas are rapidly changing and highly vulnerable to impacts from climate change, accelerating human development, and over-fishing. Quality of life and the benefits of coastal development can be greatly enhanced, and costs minimized, by projecting and comparing alternative policy outcomes before management decisions are made. This article describes the Marine Integrated Decision Analysis System (MIDAS), an interactive decision support tool designed to assist the users and managers of Belize's system of marine management areas (MMAs) in understanding the interactions among various ecological, socioeconomic, and governance conditions in a spatially explicit manner. MIDAS can simulate and visualize the likely effects of alternative management strategies and therefore provides an important tool for evaluating potential scenarios. We developed two MIDAS modules to address specific threats in Belize –spatial risk resulting from mangrove deforestation in coastal areas and the potential effect of an oil spill off the coast of Belize. Workshops conducted in Belize indicate that diverse user groups such as fishers, tourism operators, and public environmental agencies can successfully utilize MIDAS to understand MMA outcomes, and environmental risks. 相似文献
888.
海上风电是最有前途的清洁能源之一,在概念设计时,海上风机的支撑结构选型优化非常重要。选型优化是一个多属性决策问题,本文将广泛应用的多因素、多层次模糊优选理论引入支撑结构的选型决策中。针对环境等影响因素复杂、确定隶属函数主观因素较强的问题, 成功引入因素的优先关系法来确定优选矩阵的隶属度,较好地减少了确定隶属函数的人为影响。通过此优选模型成功地将四种优选方案(单桩,三脚架,五桩,高桩门架)和影响支撑结构选型的8种因素(施工难度,维护成本,CO2排放量,海水浑浊度,珊瑚礁形成,强度,刚度,耐久性)进行了多级模糊综合优选决策,得到了比较科学的决策结果,本研究为海上风机支撑结构的方案选型决策提出了一种量化分析的手段。 相似文献
889.
舰船长损管决策指挥训练模拟系统设计与实现 总被引:1,自引:0,他引:1
为解决舰船长损管决策指挥和应急处置能力培养难题,提出基于舰船原理和不沉性理论,采用计算机仿真和虚拟现实等技术,设计实现了"舰船长损管决策指挥训练模拟系统"。该系统具有舰船防沉与抗沉、防火与灭火、搁浅与脱浅等损管决策指挥训练功能,通过实践应用发挥了重要作用,为舰船长的损管训练提供有效的训练平台,促进了舰船长损管决策能力与水平的提高。 相似文献
890.
静水压力作用的水下结构振动及声辐射 总被引:5,自引:0,他引:5
采用有限元/边界元方法开发了静水压力作用的水下结构振动与声辐射的计算程序。依据不同分析域的特点,对结构域和流体内域采用有限元方法,对流体外域采用边界元方法。分析了流体一结构相似特性,使通过对常规结构有限元分析程序中的参数作合理设置,使之能直接用于内域流体声学有限元分析。流体外域采用边界元方法,选取合适的格林函数,能够考虑无穷远和自由液面边界条件。流体对结构的作用表现附加质量和附加阻尼。采用FORTRAN代码计算外域流体附加质量和附加阻尼矩阵,采用结构有限元分析程序对结构和内域流体作有限元分析,采用DMAP代码将附加质量和附加阻尼同结构质量矩阵和阻尼矩阵相叠加,实现了流固耦合计算。通过几何刚度矩阵对结构刚度矩阵修正来考虑静水压力对结构声辐射的影响。 相似文献