收费全文 | 21203篇 |
免费 | 237篇 |
国内免费 | 138篇 |
安全科学 | 533篇 |
废物处理 | 926篇 |
环保管理 | 2809篇 |
综合类 | 3419篇 |
基础理论 | 5907篇 |
环境理论 | 10篇 |
污染及防治 | 5542篇 |
评价与监测 | 1396篇 |
社会与环境 | 899篇 |
灾害及防治 | 137篇 |
2022年 | 179篇 |
2021年 | 203篇 |
2019年 | 152篇 |
2018年 | 265篇 |
2017年 | 284篇 |
2016年 | 436篇 |
2015年 | 335篇 |
2014年 | 499篇 |
2013年 | 1673篇 |
2012年 | 597篇 |
2011年 | 857篇 |
2010年 | 698篇 |
2009年 | 683篇 |
2008年 | 849篇 |
2007年 | 876篇 |
2006年 | 779篇 |
2005年 | 672篇 |
2004年 | 657篇 |
2003年 | 632篇 |
2002年 | 611篇 |
2001年 | 769篇 |
2000年 | 575篇 |
1999年 | 329篇 |
1998年 | 261篇 |
1997年 | 280篇 |
1996年 | 278篇 |
1995年 | 332篇 |
1994年 | 302篇 |
1993年 | 280篇 |
1992年 | 276篇 |
1991年 | 279篇 |
1990年 | 296篇 |
1989年 | 279篇 |
1988年 | 249篇 |
1987年 | 241篇 |
1986年 | 222篇 |
1985年 | 203篇 |
1984年 | 255篇 |
1983年 | 211篇 |
1982年 | 274篇 |
1981年 | 221篇 |
1980年 | 186篇 |
1979年 | 204篇 |
1978年 | 184篇 |
1977年 | 154篇 |
1975年 | 144篇 |
1974年 | 159篇 |
1973年 | 162篇 |
1972年 | 149篇 |
1971年 | 146篇 |
Climate change influences the agricultural sector by reducing available water resources, thereby influencing income, consumer and producer surplus, and crop prices. So, it is necessary to have a comprehensive integrated method to measure the effects of these changes on natural resources and social conditions. The present study aims to use the positive mathematical programming method to discover the trend and conditions of groundwater resources, agricultural water use, food security, and economic welfare of the agricultural sector in Iran. To this end, data for the period 2000–2015 was used under four different scenarios of normal climate change, climate change, climate variability, and concurrent climate change The results showed that the mean agricultural water use will amount to 35,103.6, 26,533.8, 35,216, and 26,510.7 million m3 and the mean decline in the reserves of aquifers will amount to 4422.22, 11,165.6, 4438.25, and 11,267.4 million m3 under the scenarios, respectively. With respect to food security, the net farm revenue will be 314,560, 248,753, 315,427, and 248,574 billion IRR, respectively. The mean crop price per ton will reach 905.3, 1141.8, 904, and 1142.8 million IRR, respectively. The mean consumer surplus will be 172,107.7, 166,450, 172,024, and 166,403 billion IRR and the mean producer surplus will be 419,959.2, 395,380, 419,751, and 395,204 billion IRR, respectively. Based on the results, to reduce the adverse impacts of climate change on different studied aspects, it is necessary to change policymaking in the water and agricultural sectors, especially regarding the shift from traditional agricultural water allocation to its market-based allocation and to change planting pattern.
相似文献Methods: Instances of non-traffic injuries and fatalities in the United States to children 0–14 years were tracked from January 1990 to December 2014 using a compilation of sources including media reports, individual accounts from families of affected children, medical examiner reports, police reports, child death review teams, coroner reports, medical professionals, legal professionals, and other various modes of publication.
Results: Over the 25-year period, there were at least 11,759 events resulting in 3,396 deaths. The median age of the affected child was 3.7 years. The incident types included 3,115 children unattended in hot vehicles resulting in 729 deaths, 2,251 backovers resulting in 1,232 deaths, 1,439 frontovers resulting in 692 deaths, 777 vehicles knocked into motion resulting in 227 deaths, 415 underage drivers resulting in 203 deaths, 172 power window incidents resulting in 61 deaths, 134 falls resulting in 54 deaths, 79 fires resulting in 41 deaths, and 3,377 other incidents resulting in 157 deaths.
Conclusions: Non-traffic injuries and fatalities present an important threat to the safety and lives of very young children. Future efforts should consider complementary surveillance mechanisms to systematically and comprehensively capture all non-traffic incidents. Continued education, engineering modifications, advocacy, and legislation can help continue to prevent these incidents and must be incorporated in overall child vehicle safety initiatives. 相似文献