全文获取类型
收费全文 | 2456篇 |
免费 | 53篇 |
国内免费 | 46篇 |
专业分类
安全科学 | 1267篇 |
废物处理 | 19篇 |
环保管理 | 192篇 |
综合类 | 735篇 |
基础理论 | 68篇 |
环境理论 | 1篇 |
污染及防治 | 60篇 |
评价与监测 | 93篇 |
社会与环境 | 38篇 |
灾害及防治 | 82篇 |
出版年
2024年 | 1篇 |
2023年 | 23篇 |
2022年 | 15篇 |
2021年 | 74篇 |
2020年 | 83篇 |
2019年 | 35篇 |
2018年 | 15篇 |
2017年 | 35篇 |
2016年 | 67篇 |
2015年 | 69篇 |
2014年 | 101篇 |
2013年 | 89篇 |
2012年 | 103篇 |
2011年 | 115篇 |
2010年 | 64篇 |
2009年 | 88篇 |
2008年 | 76篇 |
2007年 | 80篇 |
2006年 | 78篇 |
2005年 | 139篇 |
2004年 | 174篇 |
2003年 | 141篇 |
2002年 | 93篇 |
2001年 | 70篇 |
2000年 | 107篇 |
1999年 | 108篇 |
1998年 | 111篇 |
1997年 | 66篇 |
1996年 | 68篇 |
1995年 | 99篇 |
1994年 | 40篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有2555条查询结果,搜索用时 937 毫秒
881.
Introduction: An essential aspect of motorcycle rider education is how the instructor selection process impacts student learning, sometimes referred to as the human element, as it is a significant factor influencing curriculum success. Student and program achievements are partially contingent on instructors who understand the curriculum and facilitate student learning during instruction. Previous research on motorcycle rider education has emphasized a need for the examination of instructor selection and development, stating that quality education is reliant on instructors who are competent and qualified. Method: By applying an exploratory study method, state and military Motorcycle Safety Education Program Managers and Instructor Trainers were examined and compared through telephonic interviews to develop a greater understanding of instructor candidate selection criteria and vetting processes. Results: The results suggest that changes in instructor candidate selection systems may improve decisions about a candidate's job and organizational fit. Conclusions: Study conclusions indicate that use of multiple and thorough assessments to determine a candidate’s motivation, social disposition, and emotional intelligence before preparation courses may better identify candidates and align potential job and organization fit within the discipline. Practical Application: Applications of the findings would include a standardized selection process with improved interviews and pre-course auditing, and candidate expectation management before the selection to attend preparation or certification courses. The efforts potentially decrease long-term costs and deficiencies when candidates have an inconsistent job or organizational fit, departing from organizations after short periods or by not providing consistent quality instruction to students. The study recommendations, when implemented, can improve most educational disciplines where instructors are selected for technical instructional positions where students risk injury or harm. 相似文献
882.
883.
884.
我国区域性大气污染问题频频发生,成为当前亟待解决的重大环境问题。区域联防联控工作需要建立相应的区域空气质量监测体系和评价方法,这对已有的监测体系提出了新的要求。在区域监测体系中需要增加臭氧、细粒子等区域性污染物及其前体物的监测,同时设立区域监控点使监测网络覆盖面由城市建成区拓展到广大近郊及农村地区。采用移动式柱浓度监测和卫星遥感监测等多样化监测手段结合超级空气站来增强区域综合监测和源解析能力。在区域内搭建监测信息共享平台和实时发布机制并建立区域空气质量预警预报系统。建立区域内统一的质量管理和质量控制方案,城市监测点质控工作由所在省市管理,区域监控点质控工作由国家统一直管。采用分区分层次的区域空气质量评价方法,评价因子包括所有六项监测指标。 相似文献
885.
谢永明 《环境与可持续发展》2011,36(5):65-66
世界银行(以下简称"世行")与环境保护部联合开展的"中国大气污染控制综合管理研究"项目,在环保部污防司指导下,在世行驻华代表处的合作和支持下,在环境保护部对外合作中心的精心组织管理和项目专家的共同努力下,经过半年多的 相似文献
886.
本文介绍金山店铁矿微震实时监测系统的构成;并通过运用一种全新的虚拟仪器软件LabVIEW编程分析处理现场所采集的监测数据,确定井下地震事件的时间与空间分布. 相似文献
887.
888.
889.
The hybrid mixture of combustible dusts and flammable gases/vapours widely exist in various industries, including mining, petrochemical, metallurgical, textile and pharmaceutical. It may pose a higher explosion risk than gas/vapor or dust/mist explosions since the hybrid explosions can still be initiated even though both the gas and the dust concentration are lower than their lower explosion limit (LEL) values. Understanding the explosion threat of hybrid mixtures not only contributes to the inherent safety and sustainability of industrial process design, but promotes the efficiency of loss prevention and mitigation. To date, however, there is no test standard with reliable explosion criteria available to determine the safety parameters of all types of hybrid mixture explosions, nor the flame propagation and quenching mechanism or theoretical explanation behind these parameters. This review presents a state-of-the-art overview of the comprehensive understanding of hybrid mixture explosions mainly in an experimental study level; thereby, the main limitations and challenges to be faced are explored. The discussed main contents include the experimental measurement for the safety parameters of hybrid mixtures (i.e., explosion sensitivity and severity parameters) via typical test apparatuses, explosion regime and criterion of hybrid mixtures, the detailed flame propagation/quenching characteristics behind the explosion severities/sensitivities of hybrid mixtures. This work aims to summarize the essential basics of experimental studies, and to provide the perspectives based on the current research gaps to understand the explosion hazards of hybrid mixtures in-depth. 相似文献
890.
For the development of a standardized method for measuring the explosion safety characteristics of combustible hybrid dust/vapor mixtures, the influence of the ignition delay time needs to be investigated. The ignition delay time, defined as the time between the injection of dust and the activation of the ignition source, is related to the turbulence of the mixture and thus to the pressure rise rate. The ignition source for pure vapors, however, has to be activated in a quiescent atmosphere according to the standards. Nevertheless, when measuring the explosion safety characteristics of hybrid mixtures, it is important that the dust be in suspension around the igniter. Like pure dust/air mixtures, hybrid dust/vapor/air mixtures need to be ignited in a turbulent atmosphere to keep the dust in suspension.This work will therefore investigate the influence of ignition delay times on the severity of hybrid explosions. It was generally found that at shorter ignition delay times, (dp/dt)ex increased due to higher turbulence and decreases as the dust sinks to the bottom of the 20 L-sphere. This effect is more pronounced for hybrid mixtures with higher vapor content compared to dust content. 相似文献