全文获取类型
收费全文 | 5784篇 |
免费 | 540篇 |
国内免费 | 570篇 |
专业分类
安全科学 | 1184篇 |
废物处理 | 129篇 |
环保管理 | 1245篇 |
综合类 | 2620篇 |
基础理论 | 504篇 |
环境理论 | 13篇 |
污染及防治 | 308篇 |
评价与监测 | 290篇 |
社会与环境 | 286篇 |
灾害及防治 | 315篇 |
出版年
2024年 | 18篇 |
2023年 | 75篇 |
2022年 | 116篇 |
2021年 | 183篇 |
2020年 | 231篇 |
2019年 | 189篇 |
2018年 | 138篇 |
2017年 | 253篇 |
2016年 | 222篇 |
2015年 | 255篇 |
2014年 | 248篇 |
2013年 | 356篇 |
2012年 | 356篇 |
2011年 | 436篇 |
2010年 | 301篇 |
2009年 | 288篇 |
2008年 | 211篇 |
2007年 | 333篇 |
2006年 | 390篇 |
2005年 | 271篇 |
2004年 | 264篇 |
2003年 | 252篇 |
2002年 | 226篇 |
2001年 | 182篇 |
2000年 | 167篇 |
1999年 | 163篇 |
1998年 | 123篇 |
1997年 | 91篇 |
1996年 | 85篇 |
1995年 | 83篇 |
1994年 | 55篇 |
1993年 | 53篇 |
1992年 | 44篇 |
1991年 | 26篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1971年 | 15篇 |
1970年 | 6篇 |
排序方式: 共有6894条查询结果,搜索用时 734 毫秒
661.
Karen R. Hall Jean Spooner Robert J. Richardson Steve T. Hoyle Douglas J. Frederick 《Journal of the American Water Resources Association》2014,50(3):533-542
Microstegium vimineum is an invasive grass introduced from Asia that has spread throughout riparian areas of the eastern United States threatening native riparian vegetation. Postemergence (POST) herbicides registered for aquatic use were evaluated for control of M. vimineum on two riparian restoration sites in the Piedmont and Upper Coastal Plain of North Carolina. This study found that standard and lower than standard rates of diquat, fluridone, flumioxazin, glyphosate, imazamox, and imazapyr reduced weed stem density and biomass at 6 and 30 weeks after treatment (WAT). Both rates of bispyribac and penoxsulam provided less control of M. vimineum. Visual ratings showed both rates of diquat, flumioxazin, imazamox, and imazapyr controlled 63‐100% of M. vimineum at 6 WAT and 84‐100% at 30 WAT. Fluridone and glyphosate provided slightly less control. Bispyribac and penoxsulam treatments provided less control at 6 and 30 WAT compared to the other treatments. Plots treated with both rates of diquat, flumioxazin, imazamox, and imazapyr were nearly devoid of all vegetation at 30 WAT. Recommendations include POST application of lower than standard rates of diquat, flumioxazin, fluridone, glyphosate, imazamox, and imazapyr on riparian restoration sites infested with M. vimineum. Immediate vegetation management measures including temporary and permanent plant cover should be employed on treated sites where weeds are completely eradicated to prevent erosion. 相似文献
662.
663.
664.
Few studies exist on how chloride from chloride‐based deicers is transported in infiltration‐based stormwater control measures. In 2009, the U.S. Environmental Protection Agency (USEPA) constructed a 0.4 ha parking lot in Edison, New Jersey, that was surfaced with permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). Each surface type has four equally sized, lined sections that direct all infiltrate to separate 5.7 m3 collection tanks. The USEPA acute criterion for aquatic life (860 mg/l) was exceeded in events immediately following a snow event. Concentrations of the infiltrate exceeded the detection limit (5 mg/l) year round but did not exceed the USEPA chronic toxicity (230 mg/l) after April. The chloride concentration decreased with cumulative rainfall since previous snow event, and a power regression described this relationship. In the power regression, the coefficient (b) described the initial concentration following a snow event, and the exponent (m) described the rate in which chloride was flushed through the system with infiltrating water. PC had the largest coefficient (5,664) and largest absolute exponent (?0.92), followed closely by PICP (b = 4,943 and m = ?0.87), and distantly by PA (b = 2,907 and m = ?0.67). The differences in release rate were proportional to the measured surface infiltration rates of 4,000; 2,400; and 200 cm/h for PC, PICP, and PA, respectively. These results will assist those who manage or regulate stormwater where receiving waters are chloride impaired. 相似文献
665.
666.
667.
Kirk R. Vincent Jonathan M. Friedman Eleanor R. Griffin 《Environmental management》2009,44(2):218-227
Removal of nonnative riparian trees is accelerating to conserve water and improve habitat for native species. Widespread control
of dominant species, however, can lead to unintended erosion. Helicopter herbicide application in 2003 along a 12-km reach
of the Rio Puerco, New Mexico, eliminated the target invasive species saltcedar (Tamarix spp.), which dominated the floodplain, as well as the native species sandbar willow (Salix exigua Nuttall), which occurred as a fringe along the channel. Herbicide application initiated a natural experiment testing the
importance of riparian vegetation for bank stability along this data-rich river. A flood three years later eroded about 680,000 m3 of sediment, increasing mean channel width of the sprayed reach by 84%. Erosion upstream and downstream from the sprayed
reach during this flood was inconsequential. Sand eroded from channel banks was transported an average of 5 km downstream
and deposited on the floodplain and channel bed. Although vegetation was killed across the floodplain in the sprayed reach,
erosion was almost entirely confined to the channel banks. The absence of dense, flexible woody stems on the banks reduced
drag on the flow, leading to high shear stress at the toe of the banks, fluvial erosion, bank undercutting, and mass failure.
The potential for increased erosion must be included in consideration of phreatophyte control projects. 相似文献
668.
ANDREW T. KNIGHT RICHARD M. COWLING MARK DIFFORD BRUCE M. CAMPBELL 《Conservation biology》2010,24(5):1348-1358
Abstract Spatial prioritization techniques are applied in conservation‐planning initiatives to allocate conservation resources. Although typically they are based on ecological data (e.g., species, habitats, ecological processes), increasingly they also include nonecological data, mostly on the vulnerability of valued features and economic costs of implementation. Nevertheless, the effectiveness of conservation actions implemented through conservation‐planning initiatives is a function of the human and social dimensions of social‐ecological systems, such as stakeholders’ willingness and capacity to participate. We assessed human and social factors hypothesized to define opportunities for implementing effective conservation action by individual land managers (those responsible for making day‐to‐day decisions on land use) and mapped these to schedule implementation of a private land conservation program. We surveyed 48 land managers who owned 301 land parcels in the Makana Municipality of the Eastern Cape province in South Africa. Psychometric statistical and cluster analyses were applied to the interview data so as to map human and social factors of conservation opportunity across a landscape of regional conservation importance. Four groups of landowners were identified, in rank order, for a phased implementation process. Furthermore, using psychometric statistical techniques, we reduced the number of interview questions from 165 to 45, which is a preliminary step toward developing surrogates for human and social factors that can be developed rapidly and complemented with measures of conservation value, vulnerability, and economic cost to more‐effectively schedule conservation actions. This work provides conservation and land management professionals direction on where and how implementation of local‐scale conservation should be undertaken to ensure it is feasible. 相似文献
669.
/ A number of strategies for the control of vehicular emissions are being considered by the Philippine government to address Metropolitan Manila's air quality problem. An analytical tool is needed for optimizing criteria pollutant reductions given the budgetary constraints. The simplest approach is to take costs and pollutant removals to be linear with each strategy's scale of activity, and this is readily solved as a linear programming problem. Another approach is to use a dynamic system of weights which shift with progressive improvements in pollutant emissions. The two approaches yield somewhat different results, suggesting the sensitivity of the solution to the assumed weights. The study also illustrates the importance of a sound methodology for evaluating priorities given to different air quality goals. One such methodology may involve a polling of expert panels and the public to gain insight into the relative importance given to competing emissions reduction goals. An informal polling of resource agency staff was conducted and discussed in this paper. The authors take the position that proper planning involves tracing intermediate steps to the final outcome and not just focusing on the latter.KEY WORDS: Vehicular emissions; Urban air quality; Emissions control; Optimization; Manila; Environmental systems analysis 相似文献
670.
构建农民工的社会保障体系 总被引:38,自引:0,他引:38
农民工对城市和农村的发展功不可没。但是,由于制度不健全,遭遇市场风险的农民工缺乏基本的社会保障,处境艰难。本文分析了农民工缺乏社会保障的历史和现实原因,提出了构建农民工社会保障体系的设想,即以健康保障、失业保障和养老保障为主体的过渡性农民工社会保障体系,来衔接城乡社会保障。以适应城乡一体化的需要。 相似文献