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101.
Changes in Forest Area Along Stream Networks in an Agricultural Catchment of the Great Barrier Reef Lagoon 总被引:2,自引:1,他引:1
Scenes from the series of multispectral sensors on the Landsat satellites were used to map recent changes (between 1972 and 2004) in forest cover within and adjacent to stream networks of an intensively farmed region of the southern Great Barrier Reef catchment (Australia). Unsupervised ISODATA classifications of Tasseled-Cap transformed data (at 57 m ground resolution) mapped forest and cleared areas within 150 m of Pisoneer catchment waterways with 72.2% overall accuracy (K(hat) = 0.469), when adjusted for the size of each class. Although the user's accuracy was higher for the forest class (82.1 +/- 8.4% at alpha = 0.05), large errors of commission (34.2 +/- 8.3%) substantially affected map accuracy for the cleared class. The main reasons for misclassification include: (1) failure to discriminate narrowly vegetated riparian strips; (2) misregistration of scenes; and (3) spectral similarity of ground cover. Error matrix probabilities were used to adjust the mapped area of classes, resulting in a decline of forest cover by 12.3% and increase of clearing by 18.5% (22.4 km(2) change; 95% confidence interval: 14.3-29.6 km(2)) between 1972 and 2004. Despite the mapping errors, Landsat data were able to identify broad patterns of land cover change that were verified from aerial photography. Most of the forest losses occurred in open forest to woodland habitat dominated by Eucalyptus, Corymbia, and Lophostemon species, which were largely replaced by sugarcane cropping. Melaleuca communities were similarly affected, though they have a much smaller distribution in the catchment. 相似文献
102.
The extent of pollution with organotin compounds and Cd, Pb, Ni, Cu, Zn, Cr, Mn, V, Co and Al was investigated in sediments
and mussels (Mytilus galloprovincialis) from the Slovenian costal area of the Northern Adriatic Sea. Sampling was performed in Marina Portorož, Dockyard Izola,
non exposed area of the Bay of Mesečev zaliv and in Mariculture Sečovlje. Mussels were taken in the summer and winter time,
while sediments were collected during the winter sampling. Organotin compounds were determined by gas chromatography—mass
spectrometry and metals by flame or electrothermal atomic absorption spectrometry. The accuracies of the analytical procedures
were checked by the analysis of standard reference materials CRM 477 mussel tissue and PACS 2 marine sediment (organotin compounds)
and SRM 2976 mussel tissue and CRM 320 river sediment (metals). Good agreements between certified and determined values were
obtained. Normalization procedure to Al was applied to estimate the anthropogenic inputs of metals in sediments. The analyses
of sediments demonstrated moderate pollution with organotin compounds in Marina Portorož and in Dockyard Izola. Concentrations
of tributyltin species were higher than those of dibutyltin and monobutyltin. In mussels substantial contamination with tributyltin
was observed in Marina Porotrož and Dockyard Izola. The extent of pollution was higher in the winter time. The analysis of
metals in sediments exhibited elevated concentrations in Marina Portorož and Dockyard Izola. Data from the normalization procedure
indicated the anthropogenic inputs of Cu, Zn and Cr in Marina Portorož and Mn in Bay of Mesečev zaliv and Dockyard Izola.
Mussels, as accumulators of pollutants, in general contained higher metal concentrations during winter time in Dockyard Izola. 相似文献
103.
Mercury concentrations are usually significant in historic Hg mining districts all over the world, so the atmospheric environment is potentially affected. In Asturias, northern Spain, past mining operations have left a legacy of ruins and Hg-rich wastes, soils and sediments in abandoned sites. Total Hg concentrations in the ambient air of these abandoned mine sites have been investigated to evaluate the impact of the Hg emissions. This paper presents the synthesis of current knowledge about atmospheric Hg contents in the area of the abandoned Hg mining and smelting works at ‘La Peña–El Terronal’ and La Soterraña, located in Mieres and Pola de Lena districts, respectively, both within the Caudal River basin. It was found that average atmospheric Hg concentrations are higher than the background level in the area (0.1 μg Nm?3), reaching up to 203.7 μg Nm?3 at 0.2 m above the ground level, close to the old smelting chimney at El Terronal mine site. Data suggest that past Hg mining activities have big influences on the increased Hg concentrations around abandoned sites and that atmospheric transfer is a major pathway for Hg cycling in these environments. 相似文献
104.
F. Richard Hauer Jack A. Stanford Mark S. Lorang 《Journal of the American Water Resources Association》2007,43(1):104-117
Abstract: The Crown of the Continent is one of the premiere ecosystems in North America containing Waterton‐Glacier International Peace Park, the Bob Marshall‐Great Bear‐Scapegoat Wilderness Complex in Montana, various Provincial Parks in British Columbia and Alberta, several national and state forest lands in the USA, and Crown Lands in Canada. The region is also the headwater source for three of the continent’s great rivers: Columbia, Missouri and Saskatchewan that flow to the Pacific, Atlantic and Arctic Oceans, respectively. Headwaters originate in high elevation alpine environs characterized by high snow accumulations in winter and rainstorms in summer. Most headwaters of the region contain high quality waters with few ions in solution and extremely low nutrient concentrations. Alpine streams have few species of aquatic organisms; however, they often possess rare species and have hydrogeomorphic features that make them vulnerable to climatic change. Subalpine and valley bottom streams of the Crown of the Continent Ecosystem (CCE) flow through well forested watersheds. Along the elevation gradient, the streams and rivers of the CCE flow through series of confining and nonconfining valleys resulting in distinct canyon and floodplain reaches. The alluvial floodplains are characterized by high species diversity and bioproduction maintained by the hydrologic linkages of habitats. The streams and rivers of the CCE have low nutrient concentrations, but may be significantly affected by wildfire, various resource extraction activities, such as logging or mining and exurban encroachment. Wildfire has been shown to increase nutrient loading in streams, both during a fire and then following the fire for as much as 5 years. Logging practices increase nutrient loading and the algal productivity of stream periphyton. Logging and associated roads are also known to increase sediment transport into Crown of the Continent streams directly affecting spawning success of native trout. The CCE is one of the fastest growing regions in the USA because of the many recreational amenities of the region. And, while the region has many remarkably pristine headwater streams and receiving rivers, there are many pending threats to water quality and quantity. One of the most urgent threats comes from the coal and gas fields in the northern part of the Crown of the Continent, where coal deposits are proposed for mountain‐top removal and open‐pit mining operations. This will have significant effects on the waters of the region, its native plants and animals and quality of life of the people. 相似文献
105.
Dore MH 《Environment international》2005,31(8):1167-1181
The objective of this paper is to synthesize the large literature recording changing patterns of precipitation in the observed data, thus indicating that climate change is already a reality. Such a synthesis is required not only for environmental researchers but also for policy makers. The key question is the broad picture at major regional and continental levels. Some interesting conclusions for this survey are emerging. For example, the review shows increased variance of precipitation everywhere. Consistent with this finding, we observe that wet areas become wetter, and dry and arid areas become more so. In addition, the following general changing pattern is emerging: (a) increased precipitation in high latitudes (Northern Hemisphere); (b) reductions in precipitation in China, Australia and the Small Island States in the Pacific; and (c) increased variance in equatorial regions. The changes in the major ocean currents also appear to be affecting precipitation patterns. For example, increased intensity and frequency of El Ni?o and ENSO seem associated with evidence of an observed "dipole" pattern affecting Africa and Asia, although this time series is too short so far. But the changing pattern calls for renewed efforts at adaptation to climate change, as the changing precipitation pattern will also affect the regional availability of food supply. 相似文献
106.
Philip A. Meyers 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):453-463
The isotopic and molecular compositions of organic matter buried in lake sediments provide information that helps to reconstruct
past environmental conditions and to assess impacts of humans on local ecosystems. This overview of sedimentary records from
the North American Great Lakes region describes examples of applications of organic geochemistry to paleolimnological reconstructions.
These lakes experienced a succession of human-induced environmental changes that started after completion of the Erie Canal
in 1825. Agricultural deforestation in the mid-nineteenth century released soil nutrients that increased algal productivity
and caused an associated increase in algal biomarkers in sediment records. Eutrophication that accompanied magnified delivery
of municipal nutrients to the lakes in the 1960s and 1970s created excursions to less negative δ13C values in sediment organic matter. Increased organic carbon mass accumulation rates mirror the isotopic evidence of eutrophication
in the Great Lakes. 相似文献
107.
Russian olive (Elaeagnus angustifolia L.) was introduced in 1950 onto one site on the Milk River floodplain, northern Montana, 10 km downstream from the Canada/United States border. To analyze dispersal of Russian olive from the point source between 1950 and 1999, we compared distribution, numbers, size structure, and mortality of Russian olive and plains cottonwood (Populus deltoides Marsh:) on an unregulated reach of the Milk River floodplain in southeastern Alberta and north-central Montana. Within 50 years, Russian olive in this reach has moved upriver into Alberta and downriver to the Fresno Reservoir. It is now present on 69 of the 74 meander lobes sampled, comprising 34%, 62%, and 61% of all Russian olive and plains cottonwood seedlings, saplings, and trees, respectively. On some meander lobes, Russian olive has colonized similar elevations on the floodplain as plains cottonwood and is oriented in rows paralleling the river channel, suggesting that recruitment may be related to river processes. Breakup ice had killed 400 Russian olive saplings and trees and damaged >1000 others on 30 of the meander lobes in 1996. Nevertheless, Russian olive now outnumbers cottonwood on many sites on the Milk River floodplain because its seeds can be dispersed by wildlife (particularly birds) and probably by flood water and ice rafts; seeds are viable for up to 3 years and germination can take place on bare and well-vegetated soils; and saplings and trees are less palatable to livestock and beaver than plains cottonwood. Without control, Russian olive could be locally dominant on the Milk River floodplain in all age classes within 10 years and replace plains cottonwood within this century. 相似文献
108.
109.
西部大开发中的四川猕猴桃资源优势 总被引:4,自引:0,他引:4
通过对四川省猕猴桃资源现状的分析,阐述了四川猕猴桃的资源优势及其人工栽培现状,提出了在西部大开发中发展四川猕猴桃产业化的道路。 相似文献
110.