收费全文 | 626篇 |
免费 | 98篇 |
国内免费 | 164篇 |
安全科学 | 209篇 |
废物处理 | 7篇 |
环保管理 | 76篇 |
综合类 | 467篇 |
基础理论 | 26篇 |
污染及防治 | 34篇 |
评价与监测 | 53篇 |
社会与环境 | 11篇 |
灾害及防治 | 5篇 |
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 32篇 |
2021年 | 45篇 |
2020年 | 41篇 |
2019年 | 49篇 |
2018年 | 37篇 |
2017年 | 50篇 |
2016年 | 53篇 |
2015年 | 38篇 |
2014年 | 46篇 |
2013年 | 37篇 |
2012年 | 37篇 |
2011年 | 57篇 |
2010年 | 41篇 |
2009年 | 32篇 |
2008年 | 26篇 |
2007年 | 41篇 |
2006年 | 41篇 |
2005年 | 31篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 13篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1982年 | 1篇 |
Methods: Data came from administrative records maintained by a nonprofit ride service program and include 2,661 individuals aged 65+ residing in 14 states who joined the program between April 1, 2010, and November 8, 2013. Latent class analysis was used to group current drivers into 3 classes of driving status of low, medium, and high self-regulation, based on their self-reported avoidance of certain driving situations and weekly driving frequency. Demographics and ride service use rate for rides taken through March 31, 2014, by type of ride (e.g., medical, social, etc.) were calculated for nondrivers and drivers in each driving status class.
Results: The majority of ride service users were female (77%) and aged 65–74 years (82%). The primary method of getting around when enrolling for the transportation service was by riding with a friend or family member (60%). Among the 67,883 rides given, nondrivers took the majority (69%) of rides. Medical rides were the most common, accounting for 40% of all rides.
Conclusions: Reported ride usage suggests that older adults are willing to use such ride services for a variety of trips when these services are not limited to specific types (e.g., medical). Further research can help tailor strategies to encourage both nondrivers and drivers to make better use of alternative transportation that meets the special needs of older people. 相似文献
Methods: Speed cameras measured travel speeds and photographed license plates and drivers of passenger vehicles traveling on roadways in Northern Virginia during daytime off-peak hours in spring 2013. The driver licensing agencies in the District of Columbia, Maryland, and Virginia provided vehicle information numbers (VINs) by matching license plate numbers with vehicle registration records and provided the age, gender, and ZIP code of the registered owner(s). VINs were decoded to obtain the curb weight and horsepower of vehicles. The study focused on 26,659 observed vehicles for which information on horsepower was available and the observed age and gender of drivers matched vehicle registration records. Log-linear regression estimated the effects of vehicle power on mean travel speeds, and logistic regression estimated the effects of vehicle power on the likelihood of a vehicle traveling over the speed limit and more than 10 mph over the limit.
Results: After controlling for driver characteristics, speed limit, vehicle type, and traffic volume, a 1-unit increase in vehicle power was associated with a 0.7% increase in mean speed, a 2.7% increase in the likelihood of a vehicle exceeding the speed limit by any amount, and an 11.6% increase in the likelihood of a vehicle exceeding the limit by 10 mph. All of these increases were highly significant.
Conclusions: Speeding persists as a major factor in crashes in the United States. There are indications that travel speeds have increased in recent years. The current findings suggest the trend toward substantially more powerful vehicles may be contributing to higher speeds. Given the strong association between travel speed and crash risk and crash severity, this is cause for concern. 相似文献
Methods: We conducted a cross-sectional study of all 88 government-funded primary care centers in the city of Riyadh, Saudi Arabia. We administered a self-reported questionnaire to PCPs that inquired about their driving risk assessment for specific medical conditions.
Results: Among all PCPs and centers, 189 PCPs (63%) from 74 centers (84%) participated in our survey. The mean age of the PCPs was 40 ± 10 years, and 108 (57%) were men. The average clinical experience of the group was 13 ± 9 years. Fewer than half of PCPs considered diabetes mellitus (45%) and obstructive sleep apnea (46%) as potential risks for MVCs. Approximately 45% of PCPs did not notify any authority or relatives of potential driving issues that they noticed in their patients. Only 15% of the participants believed that PCPs were responsible for alerting authorities about their fitness to drive.
Conclusions: PCPs did not adequately assess their patients' driving history and eligibility. Efforts are needed to improve awareness among PCPs regarding the effects of chronic medical conditions on driving. 相似文献