全文获取类型
收费全文 | 1024篇 |
免费 | 88篇 |
国内免费 | 276篇 |
专业分类
安全科学 | 20篇 |
废物处理 | 6篇 |
环保管理 | 505篇 |
综合类 | 535篇 |
基础理论 | 120篇 |
污染及防治 | 79篇 |
评价与监测 | 27篇 |
社会与环境 | 54篇 |
灾害及防治 | 42篇 |
出版年
2023年 | 11篇 |
2022年 | 30篇 |
2021年 | 29篇 |
2020年 | 26篇 |
2019年 | 29篇 |
2018年 | 47篇 |
2017年 | 40篇 |
2016年 | 29篇 |
2015年 | 54篇 |
2014年 | 50篇 |
2013年 | 70篇 |
2012年 | 92篇 |
2011年 | 76篇 |
2010年 | 57篇 |
2009年 | 54篇 |
2008年 | 63篇 |
2007年 | 63篇 |
2006年 | 71篇 |
2005年 | 45篇 |
2004年 | 37篇 |
2003年 | 34篇 |
2002年 | 35篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 9篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有1388条查询结果,搜索用时 0 毫秒
421.
结合燃煤电厂电袋复合除尘器的入口烟道气流分布的工程案例,采用计算流体动力学(简称CFD)数值模拟技术,对烟道内的速度场进行三维数值模拟;根据分析结果进行烟道的导流板的设置,改善烟道的流场,并使入口烟道的各分支烟道流量分配均匀。对比现场烟道流量分配的测试结果,验证了CFD模拟计算的准确性。 相似文献
422.
Clayton B. Marlow Robert Finck Harrie Sherwood 《Journal of the American Water Resources Association》2006,42(4):891-900
ABSTRACT: Efforts by state and federal agencies to develop standards and guidelines for protecting and enhancing water quality on grazing lands have led to suggestions that grazed stubble height criteria could be used to determine when cattle should be removed from a specific pasture or grazing area. Until recently only indirect scientific evidence from agronomy and laboratory studies gave support to the stubble height concept. Consequently, a grazing study was initiated on a Montana ranch in 1997 to determine the reduction in overland sediment achieved by grazing a pasture to a predetermined stubble height. Treatments consisted of 7 cm (3 in) grazed, 7 cm (3 in) clipped or mowed, 15 cm (6 in) grazed; 15 cm (6 in) clipped and untreated or natural forage plant height. The five treatments were used in a two‐year trial spanning 1997 to 1999. At the conclusion of this study the magnitude of sediment production was related to the number of intense rain events during the March through June period rather than total precipitation. There was a significant year effect in terms of sediment accumulation (P < 0.01) but no year by treatment effect (P = 0.11). Even though a significant difference in sediment accumulation was detected between the shorter and taller stubble heights (P = 0.04) in both 1998 and 1999, the difference could not be explained by grazed stubble height alone. Close grazing (7 cm stubble) consistently ranked lowest in sediment production (P < 0.01) among all treatments, including the ungrazed control. These results suggest that changes in plant community structure and microtopographic caused by grazing influence sediment entrapment (retention) on hillslopes more than those caused by plant height. 相似文献
423.
Stanley A. Changnon 《Journal of the American Water Resources Association》1982,18(5):857-861
ABSTRACT: Accurate forecasting of heavy rainstorms that affect the Chicago Metropolitan area and lead to the undesirable release of storm runoff into Lake Michigan is a major objective. These releases (overflows) were found to be produced by storm events yielding 2 inches or more in a few hours, although only 24 percent of such ≥ 2-inch storms in the area during 1948-1981 produced overflows. Failure to forecast properly or to be able to react to these 2-inch overflow producing events has occurred most often in the spring and fall, although relatively often in June and July in recent years. These overflows have exhibited an inexplicable trebling during 1972-1981 without an increase in ≥ 2-inch storm events. This type of troublesome storm can be reliably predicted, using a recently developed radar man forecast system for the Chicago area. 相似文献
424.
Christopher A. Ellison Quentin D. Skinner Katta J. Ready 《Journal of the American Water Resources Association》2006,42(1):55-68
Sage Creek in south‐central Wyoming is listed as impaired by the U.S. Environmental Protection Agency (USEPA) due to its sediment contribution to the North Platte River. Despite the magnitude of sediment impacts on streams, little research has been conducted to characterize patterns of sediment transport or to model suspended sediment concentration in many arid western U.S. streams. This study examined the relationship between stream discharge and suspended sediment concentration near the Sage Creek and North Platte River confluence from 1998 through 2003. The objectives were to determine patterns of stream discharge and suspended sediment concentration, produce a sediment prediction model, and compare sediment concentrations for the six‐year period. Stream discharge and suspended sediment transport responded rapidly to convective storms and spring runoff events. During the study period, events exceeding 0.23 m3/s accounted for 92 percent of the sediment load, which is believed to originate from erodible headwater uplands. Further analysis of these data indicates that time series modeling is superior to simple linear regression in predicting sediment concentration. Significant increases in suspended sediment concentration occurred in all years except 2003. This analysis suggests that a six‐year monitoring record was insufficient to factor out impacts from climate, geology, and historical sediment storage. 相似文献
425.
Everett M. White 《Journal of the American Water Resources Association》1983,19(2):231-234
ABSTRACT: Soil surface roughness and the topographic orientation of microrelief influence runoff and water storage. Distances measured following the surface of the microrelief and horizontally across the area with the microrelief can be used with the number of microridges or microhills to estimate the average cross-sectional areas of the depression, the microslope angles, and crest heights. Microridge sideslope angles which effect the rate of runoff were estimated reasonably well in field plots by the method. 相似文献
426.
427.
Bacterial abundance and diversity in snow of East Rongbuk,Laohugou and Hailuogou glaciers on the Tibetan Plateau were investigated through epifluorescence microscope and denaturing gradient gel electrophoresis.Cell abundance ranged from 4.0 × 10 3 to 290.2 × 10 3 cells/mL.The phylogenetic trees placed the 16S rRNA sequences in four major groups:Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes.Brevundimonas,Flavobacterium,Hymenobacter,Bacillus,Polaromonas,Rhodoferax and Streptomyces were widely distributed bacteria in glaciers from different cold regions.The remaining five genera of Hylemonella,Delftia,Zoogloea,Blastococcus and Rhodococcus were endemism,only recovered from our investigated glaciers.It is proposed that the three glaciers on the Tibetan Plateau provide a specific ecological niche for prolonging survival of diverse microbial lineages. 相似文献
428.
429.
430.
北京城市道路地表径流中PAHs的污染特征研究 总被引:13,自引:2,他引:11
以北京城市道路地表径流中的PAHs为研究对象,于2006年雨季在海淀区成府路和海淀路设置3个采样点采集了6场地表径流和同期雨水样品,分析了溶解相和颗粒相PAHs的浓度.对地表径流和雨水样品中PAHs的浓度特征,地表径流中PAHs在时间和空间上的变化,及辅助参数的相关性进行了探讨.结果表明,海淀路地表径流EMC值大于成府路,自行车道地表径流EMC值与机动车道相近,道路地表径流PAHs的污染程度不能仅根据车流量判断.对单场径流历时中PAHs浓度变化的分析和累积污染负荷曲线的研究均表明,道路径流初期冲刷效应并不是普遍发生的,而是受路面积尘特征和降雨条件等多种因素的影响. 相似文献