全文获取类型
收费全文 | 1203篇 |
免费 | 20篇 |
国内免费 | 11篇 |
专业分类
安全科学 | 68篇 |
废物处理 | 75篇 |
环保管理 | 292篇 |
综合类 | 126篇 |
基础理论 | 221篇 |
环境理论 | 2篇 |
污染及防治 | 296篇 |
评价与监测 | 98篇 |
社会与环境 | 39篇 |
灾害及防治 | 17篇 |
出版年
2023年 | 9篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 134篇 |
2012年 | 40篇 |
2011年 | 56篇 |
2010年 | 53篇 |
2009年 | 50篇 |
2008年 | 59篇 |
2007年 | 66篇 |
2006年 | 68篇 |
2005年 | 48篇 |
2004年 | 33篇 |
2003年 | 53篇 |
2002年 | 46篇 |
2001年 | 19篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 23篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1981年 | 24篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有1234条查询结果,搜索用时 858 毫秒
681.
Garten CT 《Journal of environmental management》2006,81(4):323-332
A model-based analysis of the effect of prescribed burning and forest thinning or clear-cutting on stand recovery and sustainability was conducted at Fort Benning, GA, in the southeastern USA. Two experiments were performed with the model. In the first experiment, forest recovery from degraded soils was predicted for 100 years with or without prescribed burning. In the second experiment simulations began with 100 years of predicted stand growth, then forest sustainability was predicted for an additional 100 years under different combinations of prescribed burning and forest harvesting. Three levels of fire intensity (low, medium, and high), that corresponded to 17%, 33%, and 50% consumption of the forest floor C stock by fire, were evaluated at 1-, 2-, and 3-year fire return intervals. Relative to the control (no fire), prescribed burning with a 2- or 3-year return interval caused only a small reduction in predicted steady state soil C stocks (< or =25%) and had no effect on steady state tree wood biomass, regardless of fire intensity. Annual high intensity burns did adversely impact forest recovery and sustainability (after harvesting) on less sandy soils, but not on more sandy soils that had greater N availability. Higher intensity and frequency of ground fires increased the chance that tree biomass would not return to pre-harvest levels. Soil N limitation was indicated as the cause of unsustainable forests when prescribed burns were too frequent or too intense to permit stand recovery. 相似文献
682.
Single-pass electrofishing was used to define the most efficient sampling distance to assess stream condition using the index of biotic integrity (IBI) methodology in headwater (<36 km2 drainage area), warmwater streams in the Eastern Corn Belt Plain ecoregion. Based on wetted widths (1–3.3 m) of sampled reaches, we defined effort based on increased area (range 50–555 m2). Sampled area necessary to capture a representative fish assemblage increased until 167-m2 distance, which is equivalent to a minimum sampling distance of one habitat cycle. No significant difference in metric actual observed value response was found with increasing habitat cycle. Increased effort is required in smaller streams widths (≤1 m) to achieve the recommended sample area. The effect of rare fish on the IBI was tested using a modified Walford method. A significant decrease in IBI score was observed when 10 % of the rare data were removed. The presence of rare fish did not influence individual IBI metrics or scores for either the increased effort or reduced effort calibrations until greater than 3 % of the data was removed for number of species, 15 % removal of data for number of minnow species, and 5 % removal of data for catch per unit effort (CPUE). Increased effort did not affect any metric or IBI score, while reduced effort influenced the number of darter, madtom, and sculpin species and catch per unit effort metric scores but did not affect IBI score. 相似文献
683.
Benoît Jobin Claudie Latendresse Alain Baril Charles Maisonneuve Céline Boutin Dominique Côté 《Environmental monitoring and assessment》2014,186(4):2215-2229
We studied landscape dynamics for three time periods (<1950, 1965, and 1997) along a gradient of agricultural intensity from highly intensive agriculture to forested areas in southern Québec. Air photos were analyzed to obtain long-term information on land cover (crop and habitat types) and linear habitats (hedgerows and riparian habitats) and landscape metrics were calculated to quantify changes in habitat configuration. Anthropogenic areas increased in all types of landscapes but mostly occurred in the highly disturbed cash crop dominated landscape. Perennial crops (pasture and hayfields) were largely converted into annual crops (corn and soybean) between 1965 and 1997. The coalescence of annual crop fields resulted in a more homogeneous agricultural landscape. Old fields and forest cover was consistently low and forest fragmentation remained stable through time in the intensive agriculture landscapes. However, forest cover increased and forest fragmentation receded in the forest-dominated landscapes following farm abandonment and the transition of old fields into forests. Tree-dominated hedgerows and riparian habitats increased in areas with intensive agriculture. Observed changes in land cover classes are related to proximate factors, such as surficial deposits and topography. Agriculture intensification occurred in areas highly suitable for agriculture whereas farm abandonment was observed in poor-quality agriculture terrains. Large-scale conversion of perennial crops into annual crops along with continued urbanization exerts strong pressures on residual natural habitats and their inhabiting wildlife. The afforestation process occurring in the more forested landscapes along with the addition of tree-dominated hedgerows and riparian habitats in the agriculture-dominated landscapes should improve landscape ecological value. 相似文献
684.
This paper describes the development and testing of a deterministic simulation model for pest and resistance management of the Colorado potato beetle (CPB). Historically, CPB have developed resistance to new pesticides quickly. A potato farmer's pesticide application decisions trade off current crop yields and resistance development. The simulation incorporates major aspects of beetle life processes, pesticide resistance, and potato growth in order to predict the consequences of a pesticide application strategy over a ten-year planning horizon. 相似文献
685.
Mercury concentrations in fish from a Sierra Nevada foothill reservoir located downstream from historic gold-mining operations 总被引:1,自引:0,他引:1
Michael K. Saiki Barbara A. Martin Thomas W. May Charles N. Alpers 《Environmental monitoring and assessment》2010,163(1-4):313-326
This study examined mercury concentrations in whole fish from Camp Far West Reservoir, an 830-ha reservoir in northern California, USA, located downstream from lands mined for gold during and following the Gold Rush of 1848–1864. Total mercury (reported as dry weight concentrations) was highest in spotted bass (mean, 0.93 μg/g; range, 0.16–4.41 μg/g) and lower in bluegill (mean, 0.45 μg/g; range, 0.22–1.96 μg/g) and threadfin shad (0.44 μg/g; range, 0.21–1.34 μg/g). Spatial patterns for mercury in fish indicated high concentrations upstream in the Bear River arm and generally lower concentrations elsewhere, including downstream near the dam. These findings coincided with patterns exhibited by methylmercury in water and sediment, and suggested that mercury-laden inflows from the Bear River were largely responsible for contaminating the reservoir ecosystem. Maximum concentrations of mercury in all three fish species, but especially bass, were high enough to warrant concern about toxic effects in fish and consumers of fish. 相似文献
686.
Ecological network analyses and their use for establishing reference domain in functional assessment of an estuary 总被引:1,自引:0,他引:1
Robert R. Christian Mark M. Brinson James K. Dame Galen Johnson Charles H. Peterson Daniel Baird 《Ecological modelling》2009,220(22):3113
We developed a framework to use ecological network analysis for functional assessment of large aquatic ecosystems in the context of ecosystem-based management. We established a reference domain for the Neuse River Estuary, North Carolina, USA, from changes over time. Four reference network models of the trophic structure of the estuary during early and late summers of 1997 and 1998 were constructed and analyzed. The estuary has experienced various symptoms of eutrophication during the past 20 years, including summer-time hypoxia and fish kills. The networks were used to quantify indices of nominal trophic dynamics and their variation. The ratio of biomass of nekton to that of macrobenthos, derived from network construction, was used to index severity of eutrophication and to promote accessibility of ecological network analysis to environmental management. The ratio increased from early to late summer, and network metrics demonstrated a variety of responses in association with that change. Some variables from network analysis, especially related to consumers, reflected some but not all of this change. Others reflected the most severe increase in the ratio in late summer 1997 when hypoxia was most extensive. We evaluated uncertainty and the modulating effects of hierarchy by comparing variation of input biomasses with integrative response variables. Relative variation in input variables was generally greater than that of the integrative response variables as predicted by hierarchy theory. Ecological network analysis has previously served as support for ecosystem-based management of large aquatic systems with some success. However, its use can be enhanced by making it more accessible to environmental managers and policy makers. Ways to do this include promoting simple metrics from network construction and explicitly associating network analysis to concepts familiar to the management community, such as functional assessment and reference. 相似文献
687.
Stavins Robert; Carraro Carlo; Kolstad Charles 《Rev Environmental Economics and Policy》2009,3(1):1-3
Welcome to the fifth issue of the Review of Environmental Economicsand Policy, which once again includes articles, a symposium,and a set of features. In the first of two articles in this issue, Geoffrey Heal reviewswhat we have learned about the economics of global climate changeand related public policy from the extensive literature thathas emerged in response to the controversial Stern Review ofthe Economics of Climate Change. Heal provides his own perspectiveon the Stern Review (which was the focus of a symposium in ourWinter 2008 issue) as well as his views on how the recent debateaffects the economic case for action on 相似文献
688.
Jeffrey Burton Marliave Kim W. Conway Donna M. Gibbs Andy Lamb Charles Gibbs 《Marine Biology》2009,156(11):2247-2254
In the Strait of Georgia and Howe Sound, British Columbia, colonies of individual cloud sponges, growing on rock (known as
sponge gardens) receive resource subsidies from the high biodiversity of epifauna on adjacent rock habitats. Bioherms are
reefs of glass sponges living on layers of dead sponges. In the same area as the sponge gardens, newly discovered bioherms
in Howe Sound, BC (49.34.67 N, 123.16.26 W) at depths of 28- to 35-m are constructed exclusively by Aphrocallistes vastus, the cloud sponge. The sponge gardens had much higher taxon richness than the bioherms. The sponge garden had 106 species from 10 phyla, whereas
the bioherm had only 15 species from 5 phyla. For recruiting juvenile rockfish (quillback, Sebastes maliger), the food subsidy of sponge gardens appears to be missing on bioherms of cloud sponge, where biodiversity is relatively
low. While adult and subadult rockfishes (S. maliger, S. ruberrimus, S. proriger, and S. elongatus) were present on bioherms, no evidence for nursery recruitment of inshore rockfishes to bioherms was observed, whereas the
sponge gardens supported high densities of newly recruited S. maliger, perhaps owing to the combination of both refuge and feeding opportunities. These results indicate that sponge gardens form
a habitat for early stages of inshore S. maliger, whereas A. vastus bioherms are associated only with older juvenile and adult rockfishes. 相似文献
689.
The U.S. Postal Service faces a range of environmental challenges as broad as those encountered by many large industries. The Postal Service's Northeast Area has responded with a carefully crafted, far-reaching approach to environmental management that relies on several key components—chief among which is a comprehensive Environmental Compliance Master Plan.© 1999 John Wiley & Sons, Inc. 相似文献
690.
Charles R. Kratzer 《Journal of the American Water Resources Association》1999,35(2):379-395
ABSTRACT: Most of the application of the organophosphate insecticide diazinon in the San Joaquin River Basin occurs in winter to control wood-boring insects in dormant almond orchards. A federalstate collaborative study found that diazinon accounted for most of the observed toxicity of San Joaquin River water in February 1993. Previous studies focused mainly on west-side inputs to the San Joaquin River. In this 1994 study, the three major east-side tributaries to the San Joaquin River - the Merced, Tuolumne, and Stanislaus rivers - and a downstream site on the San Joaquin River were sampled throughout the hydrographs of a late January and an early February storm. In both storms, the Tuolumne River had the highest concentrations of diazinon and transported the largest load of the three tributaries. The Stanislaus River was a small source in both storms. On the basis of previous storm sampling and estimated travel times, ephemeral west-side creeks probably were the main diazinon source early in the storms, whereas the Tuolumne and Merced rivers and east-side drainages directly to the San Joaquin River were the main sources later. Although 74 percent of diazinon transport in the San Joaquin River during 1991–1993 occurred in January and February, transport during each of the two 1994 storms was only 0.05 percent of the amount applied during preceding dry periods. Nevertheless, some of the diazinon concentrations in the San Joaquin River during the January storm exceeded 0.35 μ/L, a concentration shown to be acutely toxic to water fleas. On the basis of this study and previous studies, diazinon concentrations and streamflow are highly variable during January and February storms, and frequent sampling is required to evaluate transport in the San Joaquin River Basin. 相似文献