收费全文 | 1837篇 |
免费 | 162篇 |
国内免费 | 351篇 |
安全科学 | 247篇 |
废物处理 | 43篇 |
环保管理 | 324篇 |
综合类 | 995篇 |
基础理论 | 204篇 |
环境理论 | 5篇 |
污染及防治 | 147篇 |
评价与监测 | 98篇 |
社会与环境 | 231篇 |
灾害及防治 | 56篇 |
2024年 | 4篇 |
2023年 | 35篇 |
2022年 | 68篇 |
2021年 | 76篇 |
2020年 | 93篇 |
2019年 | 95篇 |
2018年 | 69篇 |
2017年 | 120篇 |
2016年 | 136篇 |
2015年 | 113篇 |
2014年 | 104篇 |
2013年 | 145篇 |
2012年 | 173篇 |
2011年 | 163篇 |
2010年 | 107篇 |
2009年 | 93篇 |
2008年 | 81篇 |
2007年 | 107篇 |
2006年 | 98篇 |
2005年 | 64篇 |
2004年 | 61篇 |
2003年 | 48篇 |
2002年 | 41篇 |
2001年 | 37篇 |
2000年 | 25篇 |
1999年 | 36篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
Method: A total of 128 volunteer drivers in 4 age groups were asked to finish 2-, 3-, and 4-h continuous driving tasks on expressways, during which the driver's fixation, saccade, and blink measures were recorded by an eye-tracking system and the subjective sleepiness level was measured through the Stanford Sleepiness Scale. Two-way repeated measures analysis of variance was then used to examine the change in visual behavior measures across age groups over time and compare the interactive effects of these 2 factors on the dependent visual measures.
Results: Drivers' visual behavior measures and subjective sleepiness levels vary significantly over time but not across age groups. A statistically significant interaction between age group and driving duration was found in drivers' pupil diameter, deviation of search angle, saccade amplitude, blink frequency, blink duration, and closure duration. Additionally, change in a driver's subjective sleepiness level is positively or negatively associated with variation in visual behavior measures, and such relationships can be expressed in regression models for different period of driving duration.
Conclusions: Driving duration affects drivers' sleepiness significantly, so the amount of continuous driving time should be strictly controlled. Moreover, driving sleepiness can be quantified through the change rate of drivers' visual behavior measures to alert drivers of sleepiness risk and to encourage rest periods. These results provide insight into potential strategies for reducing and preventing traffic accidents and injuries. 相似文献
Introduction
Fall-related occupational injuries and fatalities are serious problems in the U.S. construction industry, especially incidents related to unguarded holes. The National Institute for Occupational Safety and Health, Division of Safety Research, Morgantown, WV conducted a project to evaluate the effectiveness of guardrail systems to prevent falls through roof and floor holes.Methods
Two commercial edge-protection products were evaluated when used as perimeter guarding around a roof hole. Installations of the commercial products were compared to job-built guardrails constructed of 2″ × 4″ construction-grade lumber. Occupational Safety and Health Administration (OSHA) regulations require that “a force of at least 200 pounds” must be supported by the top rail of a guardrail system “in any outward or downward direction at any point along the top edge.” A laboratory testing system was developed to evaluate this requirement. A dynamic 200-lb force was generated against the top rail using a weighted manikin mounted on a hinged steel frame. Nine construction workers, who served as test subjects, each built five different guardrail configurations.Results
All 45 configurations met the 200-lb OSHA requirement. Installation time for one commercial product was 32% quicker than the job-built configuration (25.6 min vs. 37.9 min).Impact on Industry
This study: (a) indicates that the two edge-protection products can be used as perimeter guarding; (b) highlights the importance of using proper materials and fasteners to construct guardrails to protect workers from falling into unguarded roof and floor holes; and (c) discusses an overall-strength-testing methodology that can be used by fall-protection researchers. 相似文献针对我国2030年碳达峰要求,立足当前经济和能源需求快速发展的现状,选取2000—2020年时间序列数据,采用Tapio脱钩模型,定量分析中国能源消费CO2排放量与经济增长的脱钩状况;建立扩展的STIRPAT模型,探讨中国能源消费CO2排放的影响因素;运用情景分析法对基准情景(S0)、产业结构优化情景(S1)、能源结构优化情景(S2)、多要素优化情景(S3)4种情景下的CO2排放量进行了预测。结果表明:中国能源消费CO2排放量与经济增长之间的脱钩状态总体以弱脱钩为主。人口规模、能源消费结构、第二产业占比、城镇化率、人均GDP、第三产业占比、碳排放强度每变动1%时,分别引起能源消费CO2排放量的2.857%、0.879%、0.836%、0.623%、(0.221+0.011ln