全文获取类型
收费全文 | 647篇 |
免费 | 32篇 |
国内免费 | 9篇 |
专业分类
安全科学 | 30篇 |
废物处理 | 19篇 |
环保管理 | 159篇 |
综合类 | 88篇 |
基础理论 | 221篇 |
污染及防治 | 113篇 |
评价与监测 | 32篇 |
社会与环境 | 16篇 |
灾害及防治 | 10篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 13篇 |
2020年 | 23篇 |
2019年 | 18篇 |
2018年 | 21篇 |
2017年 | 39篇 |
2016年 | 24篇 |
2015年 | 23篇 |
2014年 | 29篇 |
2013年 | 44篇 |
2012年 | 41篇 |
2011年 | 47篇 |
2010年 | 38篇 |
2009年 | 32篇 |
2008年 | 34篇 |
2007年 | 36篇 |
2006年 | 26篇 |
2005年 | 20篇 |
2004年 | 19篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有688条查询结果,搜索用时 390 毫秒
451.
At many sites, long‐term monitoring (LTM) programs include metals as chemicals of concern, although they may not be site‐related contaminants and their detected concentrations may be natural. At other sites, active remediation of organic contaminants in groundwater results in changes to local geochemical conditions that affect metal concentrations. Metals should be carefully considered at both types of sites, even if they are not primary contaminants of concern. Geochemical evaluation can be performed at LTM sites to determine if the monitored metals reflect naturally high background and, hence, can be removed from the analytical program. Geochemical evaluation can also be performed pre‐ and post‐treatment at active remediation sites to document the effects of organics remediation on metals and identify the processes controlling metal concentrations. Examples from both types of sites are presented in this article. © 2008 Wiley Periodicals, Inc. 相似文献
452.
453.
454.
In interior western North America, many riparian forests dominated by cottonwood and willow are failing to reproduce downstream
of dams. We tested the hypothesis that establishment is now prevented by absence of the bare, moist substrate formerly provided
by floods and channel movement. Along Boulder Creek, a dammed stream in the Colorado plains, we tested the effects of disturbance
(sod removal), irrigation, and addition of seed on the establishment of seedings of plains cottonwood (Populus deltoides subsp.monilifera) and peachleaf willow (Salix amygdaloides). In unirrigated, undisturbed plots, mean cottonwood density was 0.03 seedlings/m2. Irrigation or disturbance alone produced mean cottonwood densities of 0.39 and 0.75 seedlings/m2. Plots that were both irrigated and disturbed produced a mean cottonwood density of 10.3 seedlings/m2. The effects of irrigation and disturbance on cottonwood establishment were significant (P<0.005); added seed had no significant effect (P=0.78). The few cottonwood seedlings in unirrigated plots were in low positions susceptible to scour by future moderate flows.
We conclude that cottonwood establishment along Boulder Creek is limited by the scarcity of bare, moist sites safe from future
scour. Establishment of peachleaf willow was significantly affected only by disturbance; daily sprinkler irrigation did not
provide sufficient moisture to increase survival of this species. Our results demonstrate the feasibility of restoring plains
cottonwood forests using natural seedfall, even where only widely scattered adult trees are present. Because use of natural
seedfall conserves the genetic makeup of the local population, this method may be preferable to the use of imported cuttings. 相似文献
455.
456.
Jonathan Kazmierski Megan Kram Elizabeth Mills David Phemister Nicholas Reo Christopher Riggs 《Journal of Environmental Planning and Management》2004,47(5):709-736
This paper illustrates a landscape ecology approach for land trusts undertaking conservation at the watershed scale. A conservation plan was created for the Grand Traverse Regional Land Conservancy (GTRLC) in the headwaters of Michigan's Manistee River Watershed (USA). Eight conservation drivers were devised to identify Conservation Focus Areas (CFAs) of highest ecological importance. The CFAs were ranked based on ecological importance, feasibility of protection and size. Parcels were ranked, totalling nearly 5000 ha, within the three highest-ranking CFAs in one key county. This approach is useful to land trusts trying to operationalize three distinct goals in conservation planning: to find areas of high ecological importance, to promote the landscape's spatial integrity and to delineate threats to ecological systems and processes. 相似文献
457.
Charles E. Rodes Phil A. Lawless Jonathan W. Thornburg Ronald W. Williams Carry W. Croghan 《Atmospheric environment (Oxford, England : 1994)》2010,44(11):1386-1399
This analysis provides the initial summary of PM2.5 mass concentrations relationships for all seasons and participants for a general population in the Detroit Exposure and Aerosol Research Study (DEARS). The summary presented highlights the utility of the new methodologies applied, in addition to summarizing the particulate matter (PM) data.Results include the requirement to adjust the exposure data for monitor wearing compliance and measured environmental tobacco smoke (ETS) levels, even though the study design specified a non-smoking household. A 40% wearing compliance acceptance level was suggested as necessary to balance minimizing exposure misclassification (from poor compliance) and having sufficient data to conduct robust statistical analyses. An ETS threshold level equivalent to adding more than 1.5 μg m?3 to the collected sample was found to be necessary to detect changes in the personal exposure factor (Fpex). It is not completely clear why such a large threshold level was necessary.Statistically significant spatial PM2.5 gradients were identified in three of the six DEARS neighborhoods in Wayne County. These were expected, given the number of strong, localized PM sources in the Detroit (Michigan) metro area. Some residential outdoor bias levels compared with the central site at Allen Park exceeded 15%. After adjusting for ETS biases, the outdoor contributions to the personal exposure were typically larger by factors from 1.75 to 2.2 compared with those of the non-outdoor sources. The outdoor contribution was larger in the summer than in the winter, which is consistent with the fractions of time spent outdoors in the summer vs. the winter (6.7% vs. 1.1% of the time).Mean personal PM2.5 cloud levels for the general population DEARS cohort ranged from 1.5 to 3.8 (after ETS adjustment) and were comparable to those reported previously. The personal exposure collections indoors were typically at least 13 times greater than those contributed outdoors. 相似文献
458.
Jonathan E. M. Baillie 《Conservation biology》2010,24(5):1432-1434
459.
460.