全文获取类型
收费全文 | 8387篇 |
免费 | 697篇 |
国内免费 | 2442篇 |
专业分类
安全科学 | 802篇 |
废物处理 | 467篇 |
环保管理 | 890篇 |
综合类 | 4316篇 |
基础理论 | 1492篇 |
污染及防治 | 2305篇 |
评价与监测 | 398篇 |
社会与环境 | 421篇 |
灾害及防治 | 435篇 |
出版年
2024年 | 26篇 |
2023年 | 132篇 |
2022年 | 371篇 |
2021年 | 298篇 |
2020年 | 293篇 |
2019年 | 267篇 |
2018年 | 355篇 |
2017年 | 401篇 |
2016年 | 398篇 |
2015年 | 454篇 |
2014年 | 628篇 |
2013年 | 914篇 |
2012年 | 685篇 |
2011年 | 747篇 |
2010年 | 600篇 |
2009年 | 551篇 |
2008年 | 568篇 |
2007年 | 470篇 |
2006年 | 483篇 |
2005年 | 376篇 |
2004年 | 307篇 |
2003年 | 270篇 |
2002年 | 315篇 |
2001年 | 281篇 |
2000年 | 261篇 |
1999年 | 191篇 |
1998年 | 174篇 |
1997年 | 141篇 |
1996年 | 123篇 |
1995年 | 97篇 |
1994年 | 82篇 |
1993年 | 70篇 |
1992年 | 60篇 |
1991年 | 32篇 |
1990年 | 37篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The concern of this paper is with the spatial consequences of development in a given rural setting and the way in which physical planning fits into the revival of a dying rural area, particularly in Third World Countries. It is based on experience derived from Dekinal in Benue State, Nigeria and endeavours to define a rural area by briefly discussing its characteristics and highlighting its problems. It proposes a comprehensive development planning process to induce development based on available resources. 相似文献
992.
Chao‐Hsien Liaw Yao‐Lung Tsai Mow‐Soung Cheng 《Journal of the American Water Resources Association》2006,42(2):311-322
The Keelung River Basin in northern Taiwan lies immediately upstream of the Taipei metropolitan area. The Shijr area is in the lower basin and is subject to frequent flooding. This work applies micromanagement and source control, including widely distributed infiltration and detention/ retention runoff retarding measures, in the Wudu watershed above Shijr. A method is also developed that combines a genetic algorithm and a rainfall runoff model to optimize the spatial distribution of runoff retarding facilities. Downstream of Wudu in the Shijr area, five dredging schemes are considered. If 10‐year flood flows cannot be confined in the channel, then a levee embankment that corresponds to the respective runoff retarding scheme will be required. The minimum total cost is considered in the rule to select from the regional flood mitigation alternatives. The results of this study reveal that runoff retarding facilities installed in the upper and middle parts of the watershed are most effective in reducing the flood peak. Moreover, as the cost of acquiring land for the levee embankment increases, installing runoff retarding measures in the upper portion of the watershed becomes more economical. 相似文献
993.
Ming‐Hsi Hsu Chi‐Ray Wu Wen‐Cheng Liu Albert Y. Kuo 《Journal of the American Water Resources Association》2006,42(4):901-914
ABSTRACT: To comprehend the distributions of salinity, temperature, and suspended sediment in the Danshuei River estuary in Taiwan, monthly field surveys were conducted in 2003. These included several high and low slackwater surveys and intensive surveys. The results show that the Danshuei River estuary is predominately a partially mixed estuary. The highest concentration of suspended sediment is typically observed at the Chung‐Hsin Bridge, the most upstream sampling station. The suspended sediment concentration exhibits a general decreasing trend in the downstream direction. It may be concluded that the sediments mostly come from the upstream reach. A locally high concentration of suspended sediment is found at the Kuan‐Du station because of the local deep channel bathymetry and two‐layered estuarine circulation. A vertical two‐dimensional hydrodynamic and sediment transport model is applied to investigate the tidally averaged salinity distribution, residual circulation, and suspended sediment concentration. The modeling results reveal that, under the Q75 flow condition (i.e., low flow), a turbidity maximum occurs at the Kuan‐Du station due to the strong estuarine circulation. The model simulation with a much higher river flow condition results in a weaker residual circulation and weaker turbidity maximum. 相似文献
994.
Aaron C. Kite‐Powell Anna K. Harding 《Journal of the American Water Resources Association》2006,42(4):975-987
ABSTRACT: Approximately 4.5 million people in the United States who rely on well water are exposed to nitrate‐N concentrations exceeding the 10 mg/l standard. In this study in the Southern Willamette Valley in Oregon we reassessed nitrate‐N in rural wells sampled in 2000–2001, compared nitrate‐N concentrations among geological units, and surveyed residents about their perceptions of well water quality. Nitrate‐N concentrations were again sampled in 2002 and found to have increased significantly from the previous period. With rapid population growth in the area, the potential health risk in drinking well water that exceeds 10 mg/l nitrate‐N warrants continued public education. Nitrate‐N concentrations were found to be higher in the Holocene alluvium of the Willamette River and the Pleistocene sand and gravel post‐Missoula Flood deposits. Researchers conducting future studies may choose to stratify and monitor wells by geologic unit and by other parameters that estimate input of nutrients to the environment. Opinions differed between agricultural landowners and nonagricultural landowners with regard to the impact that agricultural fertilizers may have on water quality. Participants were supportive of a range of regulatory actions that might be used by homeowners or landowners to address ground water contamination. Given that the area is now designated a Groundwater Management Area, understanding local stakeholders’perceptions is critical and strategic and has the potential to help public agencies manage potential conflicts of opinion among stakeholders, build consensus, and help guide the approach to restoring ground water quality. 相似文献
995.
Jing Wu Shaw L. Yu Rui Zou 《Journal of the American Water Resources Association》2006,42(5):1193-1204
ABSTRACT: Watershed management strategies generally involve controlling nonpoint source pollution by implementing various best management practices (BMPs). Currently, stormwater management programs in most states use a performance‐based approach to implement onsite BMPs. This approach fails to link the onsite BMP performance directly to receiving water quality benefits, and it does not take into account the combined treatment effects of all the stormwater management practices within a watershed. To address these issues, this paper proposes a water quality‐based BMP planning approach for effective nonpoint source pollution control at a watershed scale. A coupled modeling system consisting of a watershed model (HSPF) and a receiving water quality model (CE‐QUAL‐W2) was developed to establish the linkage between BMP performance and receiving water quality targets. A Monte Carlo simulation approach was utilized to develop alternative BMP strategies at a watershed level. The developed methodology was applied to the Swift Creek Reservoir watershed in Virginia, and the results show that the proposed approach allows for the development of BMP strategies that lead to full compliance with water quality requirements. 相似文献
996.
Jessica Sargent‐Michaud Kevin J. Boyle Andrew E. Smith 《Journal of the American Water Resources Association》2006,42(5):1237-1245
ABSTRACT: This study was undertaken to investigate the cost effectiveness of selected arsenic avoidance methods. Annual costs of reverse osmosis (RO), activated alumina (AA), bottled water, and rented and purchased water coolers for various household sizes in Maine were compared. Relative ranking of systems shows that RO ($411 annually) is the most cost effective, followed by AA ($518) and one‐gallon jugs of water ($321 to $1,285), respectively, for households larger than one person. One‐gallon jugs ($321) followed by 2.5‐gallon jugs ($358) of water were found to be the most cost effective for households of one person or for households with arsenic III concentrations of 0.02 to 0.06 mg/L and arsenic V concentrations of 0.08 to 1.0 mg/L. Point‐of‐entry systems and water coolers were not found to be cost effective under any of the study's conditions. The research reported here will help states make more definitive treatment recommendations to households regarding the cost effectiveness of alternative treatment systems to reduce arsenic concentrations below 0.01 mg/L. While arsenic removal technologies are improving, which enhances removal rates and reduces costs, the major insights from this analysis appear to be reinforced by technological improvements. 相似文献
997.
Mark Dougherty Randel L. Dymond Thomas J. Grizzard Adil N. Godrej Carl E. Zipper John Randolph Christine M. Anderson‐Cook 《Journal of the American Water Resources Association》2006,42(5):1405-1419
ABSTRACT: Long term effects of precipitation and land use/land cover on basin outflow and nonpoint source (NFS) pollutant flux are presented for up to 24 years for a rapidly developing headwater basin and three adjacent headwater basins on the urban fringe of Washington, D.C. Regression models are developed to describe the annual and seasonal responses of basin outflow and IMPS pollutant flux to precipitation, mean impervious surface (IS), and land use. To quantify annual change in mean IS, a variable called delta IS is created as a temporal indicator of urban soil disturbance. Hydrologic models indicate that total annual surface outflow is significantly associated with precipitation and mean IS (r2= 0.65). Seasonal hydrologic models reveal that basin outflow is positively associated with IS during the summer and fall growing season (June to November). NPS pollutant flux models indicate that total and storm total suspended solids (TSS) flux are significantly associated with precipitation and urban soil disturbance in all seasons. Annual NPS total nitrogen flux is significantly associated with both urban and agricultural soil disturbance (r2= 0.51). Seasonal models of phosphorus flux indicate a significant association of total phosphorus flux with urban soil disturbance during the growing season. Total soluble phosphorus (TSP) flux is significantly associated with IS (r2= 0.34) and urban and agricultural soil disturbance (r2= 0.58). In urbanizing Cub Run basin, annual TSP concentrations are significantly associated with IS and cultivated agriculture (r2= 0.51). 相似文献
998.
999.
Treatment of perchlorate‐contaminated groundwater using highly selective, regenerable ion‐exchange technology has been recently demonstrated at Edwards Air Force Base, California. At an influent concentration of about 450 μg/l ClO4?, the bifunctional anion‐exchange resin bed treated approximately 40,000 empty bed volumes of groundwater before a significant breakthrough of ClO4? occurred. The presence of relatively high concentrations of chloride and sulfate in site groundwater did not appear to affect the ability of the bifunctional resin to remove ClO4?. The spent resin bed was successfully regenerated using the FeCl3?HCl regeneration technique recently developed at the Oak Ridge National Laboratory, and nearly 100 percent of sorbed ClO4? was displaced or recovered after elution with as little as about two bed volumes of the regenerant solution. In addition, a new methodology was developed to completely destroy ClO4? in the FeCl3?HCl solution so that the disposal of perchlorate‐containing hazardous wastes could be eliminated. It is therefore anticipated that these treatment and regeneration technologies may offer an efficient and cost‐effective means to remove ClO4? from contaminated groundwater with significantly reduced generation of waste requiring disposal. © 2002 Wiley Periodicals, Inc. 相似文献
1000.