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251.
Brett B. Roper John M. Buffington Eric Archer Chris Moyer Mike Ward 《Journal of the American Water Resources Association》2008,44(2):417-427
Abstract: Consistency in determining Rosgen stream types was evaluated in 12 streams within the John Day Basin, northeastern Oregon. The Rosgen classification system is commonly used in the western United States and is based on the measurement of five stream attributes: entrenchment ratio, width‐to‐depth ratio, sinuosity, slope, and substrate size. Streams were classified from measurements made by three monitoring groups, with each group fielding multiple crews that conducted two to three independent surveys of each stream. In only four streams (33%) did measurements from all crews in all monitoring groups yield the same stream type. Most differences found among field crews and monitoring groups could be attributed to differences in estimates of the entrenchment ratio. Differences in entrenchment ratio were likely due to small discrepancies in determination of maximum bankfull depth, leading to potentially large differences in determination of Rosgen’s flood‐prone width and consequent values of entrenchment. The result was considerable measurement variability among crews within a monitoring group, and because entrenchment ratio is the first discriminator in the Rosgen classification, differences in the assessment of this value often resulted in different determination of primary stream types. In contrast, we found that consistently evaluated attributes, such as channel slope, rarely resulted in any differences in classification. We also found that the Rosgen method can yield nonunique solutions (multiple channel types), with no clear guidance for resolving these situations, and we found that some assigned stream types did not match the appearance of the evaluated stream. Based on these observations we caution the use of Rosgen stream classes for communicating conditions of a single stream or as strata when analyzing many streams due to the reliance of the Rosgen approach on bankfull estimates which are inherently uncertain. 相似文献
253.
Representative Landscapes in the Forested Area of Canada 总被引:1,自引:0,他引:1
Canada is a large nation with forested ecosystems that occupy over 60% of the national land base, and knowledge of the patterns
of Canada’s land cover is important to proper environmental management of this vast resource. To this end, a circa 2000 Landsat-derived
land cover map of the forested ecosystems of Canada has created a new window into understanding the composition and configuration
of land cover patterns in forested Canada. Strategies for summarizing such large expanses of land cover are increasingly important,
as land managers work to study and preserve distinctive areas, as well as to identify representative examples of current land-cover
and land-use assemblages. Meanwhile, the development of extremely efficient clustering algorithms has become increasingly
important in the world of computer science, in which billions of pieces of information on the internet are continually sifted
for meaning for a vast variety of applications. One recently developed clustering algorithm quickly groups large numbers of
items of any type in a given data set while simultaneously selecting a representative—or “exemplar”—from each cluster. In
this context, the availability of both advanced data processing methods and a nationally available set of landscape metrics
presents an opportunity to identify sets of representative landscapes to better understand landscape pattern, variation, and
distribution across the forested area of Canada. In this research, we first identify and provide context for a small, interpretable
set of exemplar landscapes that objectively represent land cover in each of Canada’s ten forested ecozones. Then, we demonstrate
how this approach can be used to identify flagship and satellite long-term study areas inside and outside protected areas
in the province of Ontario. These applications aid our understanding of Canada’s forest while augmenting its management toolbox,
and may signal a broad range of applications for this versatile approach. 相似文献
254.
Mike Barna Brian Lamb Hal Westberg 《Journal of the Air & Waste Management Association (1995)》2013,63(7):1021-1034
ABSTRACT A modeling system consisting of MM5, Calmet, and Calgrid was used to investigate the sensitivity of anthropogenic volatile organic compound (VOC) and oxides of nitrogen (NOx) reductions on ozone formation within the Cascadia airshed of the Pacific Northwest. An ozone episode that occurred on July 11-14, 1996, was evaluated. During this event, high ozone levels were recorded at monitors downwind of Seattle, WA, and Portland, OR, with one monitor exceeding the 1 hr/120 ppb National Ambient Air Quality Standard (at 148 ppb), and six monitors above the proposed 8 hr/80 ppb standard (at 82-130 ppb). For this particular case, significant emissions reductions, between 25 and 75%, would be required to decrease peak ozone concentrations to desired levels. Reductions in VOC emissions alone, or a combination of reduced VOC and NOx emissions, were generally found to be most effective; reducing NOx emissions alone resulted in increased ozone in the Seattle area. When only VOC emissions were curtailed, ozone reductions occurred in the immediate vicinity of densely populated areas, while NOx reductions resulted in more widespread ozone reductions. 相似文献
255.
The Great Lakes Hydrography Dataset: Consistent,Binational Watersheds for the Laurentian Great Lakes Basin 下载免费PDF全文
Danielle K. Forsyth Catherine M. Riseng Kevin E. Wehrly Lacey A. Mason John Gaiot Tom Hollenhorst Craig M. Johnston Conrad Wyrzykowski Gust Annis Chris Castiglione Kent Todd Mike Robertson Dana M. Infante Lizhu Wang James E. McKenna Gary Whelan 《Journal of the American Water Resources Association》2016,52(5):1068-1088
Ecosystem‐based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods, we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km2, or about twice the 247,003 km2 surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great Lakes. 相似文献
256.
Kris Verheyen Margot Vanhellemont Harald Auge Lander Baeten Christopher Baraloto Nadia Barsoum Simon Bilodeau-Gauthier Helge Bruelheide Bastien Castagneyrol Douglas Godbold Josephine Haase Andy Hector Hervé Jactel Julia Koricheva Michel Loreau Simone Mereu Christian Messier Bart Muys Philippe Nolet Alain Paquette John Parker Mike Perring Quentin Ponette Catherine Potvin Peter Reich Andy Smith Martin Weih Michael Scherer-Lorenzen 《Ambio》2016,45(1):29-41
257.
Jia Wen Mike J. McLaughlin Samuel P. Stacey Jason K. Kirby 《Environmental science and pollution research international》2016,23(21):21327-21335
The availability of cadmium (Cd) and zinc (Zn) to sunflower (Helianthus annuus) was investigated in rhamnolipid- and ethylenediaminetetraacetic acid (EDTA)-buffered solutions in order to evaluate the influence of aqueous speciation of the metals on their uptake by the plant, in relation to predictions of uptake by the free ion activity model (FIAM). Free metal ion activity was estimated using the chemical equilibrium program MINTEQ or measured by Donnan dialysis. The uptake of Cd followed the FIAM for the EDTA-buffered solution at EDTA concentrations below 0.4 μM; for the rhamnolipid-buffered solution, the uptake of both metals in roots was not markedly affected by increasing rhamnolipid concentrations in solution. This suggests rhamnolipid enhanced metal accumulation in plant roots (per unit free metal in solution) possibly through formation and uptake of lipophilic complexes. The addition of normal Ca concentrations (low millimetre range) to the rhamnolipid uptake solutions reduced Cd accumulation in shoots by inhibiting Cd translocation, whereas it significantly increased Zn accumulation in shoots. This study confirms that although rhamnolipid could enhance accumulation of Cd in plants roots at low Ca supply, it is not suitable for Cd phytoextraction in contaminated soil environments where Ca concentrations in soil solution are orders of magnitude greater than those of Cd. 相似文献
258.
259.
In December 1997, the United Nations Framework Convention on Climate Change (FCCC) adopted the Kyoto Protocol. This paper
describes a framework that models the climatic implications of this international agreement, using Monte Carlo simulations
and the preliminary Intergovernmental Panel on Climate Change emissions scenarios (SRES). Emissions scenarios (including intervention
scenarios), climate sensitivity, and terrestrial carbon sink are the key sampled model parameters. This framework gives prior
probability distributions to these parameters and, using a simple climate model, posterior distributions of global temperature
change are determined for the future.
Our exercise showed that the Kyoto Protocol's effectiveness will be mostly dependent upon which SRES world evolves. In some
worlds the Protocol decreases the warming considerably but in others it is almost irrelevant. We exemplified this approach
with a current FCCC issue, namely “hot air”. This modelling framework provides a probabilistic assessment of climate policies,
which can be useful for decision-makers involved in global climate change management.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
260.
Brett A. Bryan Stefan Hajkowicz Steve Marvanek Mike D. Young 《Environmental Modeling and Assessment》2009,14(3):375-390
We integrate information from several disparate data sources including agricultural statistics and remote sensing to quantify
and map the distribution and dynamics of agricultural returns to land and water resources from 1996/1997 to 2000/2001 in the
Murray–Darling Basin (MDB), Australia. Total profit to agriculture was estimated at AUD3.86B in 1996/1997 and AUD3.73B in
2000/2001. The mapping reveals a high spatial concentration of economic returns to land and water resources from agriculture.
Dryland agriculture covers over 82% of the study area. Irrigated agriculture covers 1.7% of the land area (2000/2001) but
returns one third of the total profit to agriculture. We found that around 80% of the profit to agriculture comes from just
over 5% of the land area. The results from this regional scale economic mapping can inform regulatory policy and public investments
in natural resource management through targeting industries and regions that provide low marginal returns to the natural resource
base. 相似文献