收费全文 | 17755篇 |
免费 | 288篇 |
国内免费 | 381篇 |
安全科学 | 633篇 |
废物处理 | 745篇 |
环保管理 | 2656篇 |
综合类 | 3001篇 |
基础理论 | 4543篇 |
环境理论 | 7篇 |
污染及防治 | 4682篇 |
评价与监测 | 1006篇 |
社会与环境 | 1026篇 |
灾害及防治 | 125篇 |
2023年 | 96篇 |
2022年 | 174篇 |
2021年 | 171篇 |
2020年 | 192篇 |
2019年 | 156篇 |
2018年 | 292篇 |
2017年 | 271篇 |
2016年 | 421篇 |
2015年 | 340篇 |
2014年 | 450篇 |
2013年 | 1449篇 |
2012年 | 628篇 |
2011年 | 897篇 |
2010年 | 680篇 |
2009年 | 768篇 |
2008年 | 837篇 |
2007年 | 878篇 |
2006年 | 734篇 |
2005年 | 612篇 |
2004年 | 629篇 |
2003年 | 574篇 |
2002年 | 546篇 |
2001年 | 646篇 |
2000年 | 521篇 |
1999年 | 317篇 |
1998年 | 213篇 |
1997年 | 231篇 |
1996年 | 227篇 |
1995年 | 269篇 |
1994年 | 213篇 |
1993年 | 210篇 |
1992年 | 178篇 |
1991年 | 183篇 |
1990年 | 180篇 |
1989年 | 182篇 |
1988年 | 157篇 |
1987年 | 139篇 |
1986年 | 157篇 |
1985年 | 143篇 |
1984年 | 196篇 |
1983年 | 150篇 |
1982年 | 176篇 |
1981年 | 157篇 |
1980年 | 131篇 |
1979年 | 149篇 |
1978年 | 96篇 |
1977年 | 100篇 |
1975年 | 90篇 |
1974年 | 93篇 |
1972年 | 97篇 |
Methods: During 4 consecutive school years, 2011–2015, the Give Kids a Boost (GKB) program was implemented in a total of 8 schools with similar demographics in Dallas County. Observational surveys were conducted at project schools before project implementation (P0), 1–4 weeks after the completion of project implementation (P1), and 4–5 months later (P2). Changes in booster seat use for the 3 time periods were compared for the 8 project and 14 comparison schools that received no intervention using a nonrandomized trial process.
The intervention included (1) train-the-trainer sessions with teachers and parents; (2) presentations about booster seat safety; (3) tailored communication to parents; (4) distribution of fact sheets/resources; (5) walk-around education; and (6) booster seat inspections.
The association between the GKB intervention and proper booster seat use was determined initially using univariate analysis. The association was also estimated using a generalized linear mixed model predicting a binomial outcome (booster seat use) for those aged 4 to 7 years, adjusted for child-level variables (age, sex, race/ethnicity) and car-level variables (vehicle type). The model incorporated the effects of clustering by site and by collection date to account for the possibility of repeated sampling.
Results: In the 8 project schools, booster seat use for children 4–7 years of age increased an average of 20.9 percentage points between P0 and P1 (P0 = 4.8%, P1 = 25.7%; odds ratio [OR] = 6.9; 95% confidence interval [CI], 5.5, 8.7; P < .001) and remained at that level in the P2 time period (P2 = 25.7%; P < .001, for P0 vs. P2) in the univariate analysis. The 14 comparison schools had minimal change in booster seat use. The multivariable model showed that children at the project schools were significantly more likely to be properly restrained in a booster seat after the intervention (OR = 2.7; 95% CI, 2.2, 3.3) compared to the P0 time period and compared to the comparison schools.
Conclusion: Despite study limitations, the GKB program was positively associated with an increase in proper booster seat use for children 4–7 years of age in school settings among diverse populations in economically disadvantaged areas. These increases persisted into the following school year in a majority of the project schools. The GKB model may be a replicable strategy to increase booster seat use among school-age children in similar urban settings. 相似文献
While progress has been made in reducing external nutrient inputs to the Baltic Sea, further actions are needed to meet the goals of the Baltic Sea Action Plan (BSAP), especially for the Baltic Proper, Gulf of Finland, and Gulf of Riga sub-basins. We used the net anthropogenic nitrogen and phosphorus inputs (NANI and NAPI, respectively) nutrient accounting approach to construct three scenarios of reduced NANI-NAPI. Reductions assumed that manure nutrients were redistributed from areas with intense animal production to areas that focus on crop production and would otherwise import synthetic and mineral fertilizers. We also used the Simple as Necessary Baltic Long Term Large Scale (SANBALTS) model to compare eutrophication conditions for the scenarios to current and BSAP-target conditions. The scenarios suggest that reducing NANI-NAPI by redistributing manure nutrients, together with improving agronomic practices, could meet 54–82% of the N reductions targets (28–43 kt N reduction) and 38–64% P reduction targets (4–6.6 kt P reduction), depending on scenario. SANBALTS output showed that even partial fulfillment of nutrient reduction targets could have ameliorating effects on eutrophication conditions. Meeting BSAP targets will require addressing additional sources, such as sewage. A common approach to apportioning sources to external nutrients loads could enable further assessment of the feasibility of eutrophication management targets.
相似文献Understanding how cities can transform organic waste into a valuable resource is critical to urban sustainability. The capture and recycling of phosphorus (P), and other essential nutrients, from human excreta is particularly important as an alternative organic fertilizer source for agriculture. However, the complex set of socio-environmental factors influencing urban human excreta management is not yet sufficiently integrated into sustainable P research. Here, we synthesize information about the pathways P can take through urban sanitation systems along with barriers and facilitators to P recycling across cities. We examine five case study cities by using a sanitation chains approach: Accra, Ghana; Buenos Aires, Argentina; Beijing, China; Baltimore, USA; and London, England. Our cross-city comparison shows that London and Baltimore recycle a larger percentage of P from human excreta back to agricultural lands than other cities, and that there is a large diversity in socio-environmental factors that affect the patterns of recycling observed across cities. Our research highlights conditions that may be “necessary but not sufficient” for P recycling, including access to capital resources. Path dependencies of large sanitation infrastructure investments in the Global North contrast with rapidly urbanizing cities in the Global South, which present opportunities for alternative sanitation development pathways. Understanding such city-specific social and environmental barriers to P recycling options could help address multiple interacting societal objectives related to sanitation and provide options for satisfying global agricultural nutrient demand.
相似文献