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   276篇
  免费   21篇
  国内免费   15篇
安全科学   58篇
废物处理   7篇
环保管理   55篇
综合类   88篇
基础理论   37篇
污染及防治   13篇
评价与监测   17篇
社会与环境   15篇
灾害及防治   22篇
  2024年   1篇
  2023年   1篇
  2022年   7篇
  2021年   3篇
  2020年   2篇
  2019年   9篇
  2018年   5篇
  2017年   6篇
  2016年   11篇
  2015年   8篇
  2014年   13篇
  2013年   10篇
  2012年   15篇
  2011年   23篇
  2010年   13篇
  2009年   14篇
  2008年   12篇
  2007年   13篇
  2006年   10篇
  2005年   12篇
  2004年   14篇
  2003年   13篇
  2002年   11篇
  2001年   11篇
  2000年   10篇
  1999年   4篇
  1998年   7篇
  1997年   8篇
  1996年   9篇
  1995年   3篇
  1994年   7篇
  1993年   4篇
  1992年   5篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   3篇
  1987年   1篇
  1985年   1篇
  1984年   2篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有312条查询结果,搜索用时 0 毫秒
301.
行业特性和技术约束致使一些制造企业产生大量的副产品和边角废料,对环境造成巨大压力.而可持续发展要求则促使制造企业寻求一种与自然生态环境和谐共处、资源良性循环的物流模式,构建再循环物流系统.因此,为了有效解决经济发展与环境的矛盾,促进产业间或产业内工业企业进行循环经济实践,设计具有生态柔性的B2B网络下再循环物流系统的结构模型.运用环境影响分析模型,分析再循环物流系统各个业务单元的环境影响因子.基于结构模型,运用混合整数规划方法,构建再循环物流系统多目标优化模型.该模型同时考虑了再循环系统的物流成本和外部环境影响;适合于多物料、单周期、有产能限制的再循环网络设施选址-分配问题.通过算例验证了模型的有效性.   相似文献   
302.
The traditional view of fire as a destructive agent requiring immediate suppression is giving way to the view that fire can and should be used to meet land management goals. Thus,fire control is being replaced by the more general concept offire management, which is based on the need to integrate fire policy with land management objectives. The social, economic, and ecologic effects of fire must be evaluated in the selection of land management alternatives.The activities of fire management organizations—fire prevention, control, and use of fire—must respond to needs of land management. Many agencies have developed fire organizations as separate entities that set their own objectives. The many land and resource managers who have recognized the need to incorporate fire considerations into land-use planning have so far lacked the techniques to do so.As a natural process, fire has an important function in forest and range ecosystems. Fire can greatly influence the quantity and quality of resource outputs; it is a two-edged sword that can either harm or benefit our goals, depending upon the complex effects of fire and the nature of our wants.The Fire in Multiple-Use Management Research, Development, and Applications (RD&A) Program was initiated by the U.S. Department of Agriculture, Forest Service, at the Northern Forest Fire Lab in Missoula to assist land managers. This profile explains what an RD&A program is; discusses its mission, goals, and approach to the problem; and tells why the approach involves federal laboratories, universities, and private research foundations.  相似文献   
303.
清洁生产审核中审核师的导向作用   总被引:3,自引:0,他引:3  
中油辽河工程有限公司清洁生产审核中心对下属企业进行了清洁生产审核。确定了变压器检修车间烘干室为清洁生产审核的重点,对其实施了技术改造,审核工作取得了成功。在审核过程中,审核人员发挥了正确的导向作用,他们具备审核知识并熟练掌握审核程序和方法以及现代管理知识,具有一定的专业技术和实际工作经验。  相似文献   
304.
We evaluated ecological monitoring data and landowner perceptions to the federally funded Wetlands Reserve Program (WRP) in a three-county region in Wisconsin. We surveyed landowner satisfaction, involvement, participation, and use of the WRP restoration sites. We found that landowners are satisfied with the overall program (mean, 3.6 ± 0.2 [SE], on a scale of 1–5, with 5 being completely satisfied). WRP restorations significantly increased the area of wetland within the sites surveyed, the increase was primarily of fresh meadow (736.32 ha after restoration). Satisfaction is related to landowner participation during restoration and to the economic incentives provided by the WRP, Landowner satisfaction and the number of plant communities after restoration are unrelated to each other or to restoration and easement costs per hectare. Survey participants recommended some changes to the WRP, including a reduction in the tax rate of land enrolled in the WRP, approval for permanent deer stands, and increased communication with WRP officials during the restoration. Monitoring information collected for WRP restoration sites does not allow assessment of whether WRP sites are functionally equivalent to natural sites. We suggest that the WRP require a more rigorous monitoring program, including guidelines for invasive species control. Managers should also encourage collaborations with external researchers and consider restorations within an experimental framework.  相似文献   
305.
在板材数字化成形过程中零件的直壁部分常因为金属变形量过大而极易发生破裂 ,故在加工前需要进行适当的路径规划以控制成形中直壁部分金属过度变形 ,使板材整体壁厚变化缓慢而均匀 ,优化其成形过程 ,最终完成薄板材的直壁部分成形。研究了具体的路径规划方法及其加工轨迹自动生成 ,主要从工艺角度对直壁部分成形作了有益的探索  相似文献   
306.
ABSTRACT: This report summarizes the findings of a ten week study made by the eight member Urban and Environmental Studies Program student staff of the Rock Creek Area Community Projects Board to assist the Village in its search for funds to improve its inadequate water and sewage systems. The ten year history of the Village of Rock Creek in its previous attempts to secure funding from outside sources is summarized. An analysis of federal funding programs’criteria is developed. Recommendations and a step by step analysis of how to precure these funds by the Village Council is presented. This report highlights the ten week activity which successfully produced earmarked federal funds for the Village's water project.  相似文献   
307.
新疆鄯善县吐峪沟千佛洞崩塌灾害特征及防治对策探讨   总被引:1,自引:0,他引:1  
为了查清新疆鄯善县吐峪沟千佛洞旅游区崩塌灾害的危害,对区内崩塌灾害的分布、发育特征、形成影响因素及破坏模式等进行了详细勘查,结果表明崩塌灾害主要受地形地貌、地层岩性、地质构造、风化、降水、地震、人类工程活动等多种内外因素的影响,崩塌危岩体直接威胁旅游区内人行栈道和部分佛窟;同时针对勘查结果,提出了避让与治理相结合的防治...  相似文献   
308.

Introduction

This paper investigates potential gender and age differences in conviction and crash occurrence subsequent to being directed to attend Iowa's Driver Improvement Program (DIP).

Methods

Binary logit models were developed to investigate the factors that influence conviction occurrence after DIP by gender and age. Because of the low crash occurrence subsequent to DIP, association rules were applied to investigate the factors that influence crash occurrence subsequent to DIP, in lieu of econometric models.

Results

There were statistical significant differences by driver gender, age, and conviction history in the likelihood of subsequent convictions. However, this paper found no association between DIP outcome, crash history, and crash occurrence.

Impact on industry

Evaluating the differences in conviction and crash occurrence subsequent to DIP between female and male drivers, and among different age groups can lead to improvements of the effectiveness of DIPs and help to identify low-cost intervention measures, customized based on drivers’ gender and age, for improving driving behaviors.  相似文献   
309.
随着民航运输业的发展,航班密度不断增加,相邻停机位间推出冲突概率不断增加。为合理分配大型繁忙机场停机位,兼顾安全与效率,建立基于运行安全的停机位分配问题优化模型。在模型中加入约束条件以避免潜在的推出冲突,以及考虑将重要航班优先分配到指定的旅客行走距离较短的停机位,来提高旅客的整体满意度。通过分析机位分配特点,选择性能比较优越的遗传算法进行求解。最后用实际算例进行验证,得到停机位分配甘特图以及算法收敛曲线。从结果中可以看到,停机位分配比较合理,算法收敛性能良好。就整体而言,达到了预期的要求。  相似文献   
310.
济南某商业广场超过50000 m2的基坑采用一种改进的斜支撑支护体系进行支护,与普通斜支撑支护型式不同,该支护体系包括支护桩、斜撑、立柱与支撑桩.本文采用FLAC3D显式有限差分数值计算分析方法,并结合支护桩水平位移测斜数据,对该支护体系的变形特性进行分析研究,从中论证各支护单元在3个开挖阶段的运动学效应.研究结果表明...  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