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831.
Submerged aquatic vegetation (SAV) is considered an important habitat for juvenile and small forage fish species, but many
long-term recruitment surveys do not effectively monitor fish communities in SAV. To better understand the impact of recent
large increases of SAV on the fish community in tidal freshwater reaches of the Potomac River, we compared traditional seine
sampling from shore with drop ring sampling of SAV beds (primarily Hydrilla) in a shallow water (depths, <1.5 m) embayment,
Gunston Cove. To accomplish this, we developed species-specific catch efficiency values for the seine gear and calculated
area-based density in both shoreline and SAV habitats in late summer of three different years (2007, 2008, and 2009). For
the dominant species (Fundulus diaphanus, Lepomis macrochirus, Etheostoma olmstedi, Morone americana, Lepomis gibbosus, and Fundulus heteroclitus), density was nearly always higher in SAV, but overall, species richness was highest in shoreline habitats sampled with seines.
Although historical monitoring of fish in Gunston Cove (and throughout Chesapeake Bay) is based upon seine sampling (and trawl
sampling in deeper areas), the high densities of fish and larger areal extent of SAV indicated that complementary sampling
of SAV habitats would produce more accurate trends in abundances of common species. Because drop ring samples cover much less
area than seines and may miss rare species, a combination of methods that includes seine sampling is needed for biodiversity
assessment. The resurgence of SAV in tidal freshwater signifies improving water quality, and methods we evaluated here support
improved inferences about population trends and fish community structure as indicators of ecosystem condition. 相似文献
832.
Surface water acidification was identified as a major environmental problem in the 1960s. Consequently, a liming program was launched in Sweden in the 1970s. The primary purpose of liming is to restore conditions that existed prior to acidification. To reach this goal, as well as achieve 'good status' (i.e. low levels of distortion resulting from human activity) in European freshwaters until 2016 under the European Union Water Framework Directive, lake data are required to define reference conditions. Here, we compare data from chemical/biological monitoring of 12 limed lakes with results of paleolimnological investigations, to address questions of reference conditions, acidification, and restoration by liming. Using diatom-based lake-water pH inferences, we found clear evidence of acidification in only five of the 12 lakes, which had all originally been classified as acidified according to monitoring data. After liming, measured and diatom-inferred pH agree well in seven lakes. The sediment record of three of the five remaining lakes gave ambiguous results, presumably due to sediment mixing or low sediment accumulation rates. It is difficult to determine whether liming restored the lakes to a good status, especially as some of the lakes were not acidified during the twentieth century. In addition to acid deposition, other factors, such as natural lake and catchment ontogeny or human impact through agricultural activity, influence lake acidity. This study shows that monitoring series are usually too short to define reference conditions for lakes, and that paleolimnological studies are useful to set appropriate goals for restoration and for evaluation of counter measures. 相似文献
833.
Aubail A Dietz R Rigét F Sonne C Wiig Ø Caurant F 《Journal of environmental monitoring : JEM》2012,14(1):56-63
We examined the use of mercury (Hg) and nitrogen and carbon stable isotopes in teeth of polar bear (Ursus maritimus) from Svalbard as biotracers of temporal changes in Hg pollution exposure between 1964 and 2003. Teeth were regarded as a good matrix of the Hg exposure, and in total 87 teeth of polar bears were analysed. Dental Hg levels ranged from 0.6 to 72.3 ng g(-1) dry weight and increased with age during the first 10 years of life. A decreasing time trend in Hg concentrations was observed over the recent four decades while no temporal changes were found in the stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C). This suggests that the decrease of Hg concentrations over time was more likely due to a lower environmental Hg exposure in this region rather than a shift in the feeding habits of Svalbard polar bears. 相似文献
834.
Magnus Lund Christian Stiegler Jakob Abermann Michele Citterio Birger U. Hansen Dirk van As 《Ambio》2017,46(1):81-93
The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt. For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during summer clouds have a cooling effect over tundra and a warming effect over ice, reflecting the spatial variation in albedo. The complex interactions between factors affecting SEB across surface types remain a challenge for understanding current and future conditions. Extended monitoring activities coupled with modelling efforts are essential for assessing the impact of warming in the Arctic. 相似文献
835.
Martin Woerter Spyros Arvanitis Christian Rammer Michael Peneder 《International Journal of Green Energy》2017,14(14):1192-1208
We contribute to the existing research about policy-induced technology adoption in several ways. First, we suggest a new survey design to measure the energy-related policy environment. Second, we simultaneously estimate the policy effects for the adoption propensity and the adoption intensity simultaneously and, third, we compare the policy effects in the three countries, Austria, Germany, and Switzerland. Based on a representative sample of firms for all three countries we find that policies essentially promote the adoption of technologies and they are practically ineffective for the intensity, which poses a great challenge to future policy designs. Voluntary agreements or demand-related factors are among the most important drivers for the adoption propensity of green energy technologies. Given the current institutional framework in the surveyed countries, subsidies are more effective in Austria, taxes are more effective in Germany, and demand-related factors are relatively more effective in Switzerland. 相似文献
836.
Meier HE Müller-Karulis B Andersson HC Dieterich C Eilola K Gustafsson BG Höglund A Hordoir R Kuznetsov I Neumann T Ranjbar Z Savchuk OP Schimanke S 《Ambio》2012,41(6):558-573
Multi-model ensemble simulations using three coupled physical-biogeochemical models were performed to calculate the combined impact of projected future climate change and plausible nutrient load changes on biogeochemical cycles in the Baltic Sea. Climate projections for 1961-2099 were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Helsinki Commission's (HELCOM) Baltic Sea Action Plan (BSAP). The model results suggest that in a future climate, water quality, characterized by ecological quality indicators like winter nutrient, summer bottom oxygen, and annual mean phytoplankton concentrations as well as annual mean Secchi depth (water transparency), will be deteriorated compared to present conditions. In case of nutrient load reductions required by the BSAP, water quality is only slightly improved. Based on the analysis of biogeochemical fluxes, we find that in warmer and more anoxic waters, internal feedbacks could be reinforced. Increased phosphorus fluxes out of the sediments, reduced denitrification efficiency and increased nitrogen fixation may partly counteract nutrient load abatement strategies. 相似文献
837.
Rylander L Björkdahl CM Axmon A Giwercman A Jönsson BA Lindh C Rignell-Hydbom A 《Chemosphere》2012,88(7):828-831
Background and aim
Persistent organochlorine pollutants (POPs) have in epidemiological studies been associated with health hazards. The exposure window might be crucial and it is, accordingly, important to analyze exposure concentrations in samples collected at the window of interest. This makes the use of stored blood samples extremely interesting. However, small blood volumes from stored samples in biobanks means that the researchers in epidemiological studies most often have to select a limited number of biomarkers representing the POP exposure and abstain from analyses of lipid concentrations. This raises the question of the necessity of lipid adjustment. The aim of the present study was to evaluate the correlation between fresh weight and lipid adjusted concentrations.Methods
We included data from studies were we have used the PCB congener 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) as a biomarker for POP exposure and where fresh weight as well as lipid adjusted PCB-153 concentrations are known (n = 1628). The variety of the cohort members in the different studies gave us the possibility to better understand how well these measures correlate.Results
When all individuals were included in the analyses a correlation coefficient of 0.95 between fresh weight and lipid adjusted serum concentrations was obtained. Restricting the analyses to specific subgroups (based on gender, fasting status, age and BMI) gave correlation coefficients between 0.85 and 0.97.Conclusions
This study does strongly support the use of samples from biobanks in epidemiological studies for analyzing PCBs, at least regarding PCB-153, even though it is not possible to lipid adjust the results. 相似文献838.
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
839.
840.
Given that research on sustainable development usually relates to real-world challenges, it requires researchers to align scientific knowledge production with concrete societal problem situations. To empirically explore how researchers frame scientific contributions when designing and planning projects, we conducted a qualitative study on land use–related projects based on the methodology of grounded theory. We identified major influence factors and various types of research design. Among the factors that influence project framing, scientific considerations were found to be more important than expected. Core characteristics of project framings concerned (a) type of scientific contributions envisaged; (b) real-world sustainability challenges addressed, and (c) researchers’ conceptions of how knowledge would reach its addressees. Three different types of project framing were found, suggesting that framing strongly depends on (the researchers’ perception of) how well a real-world problem situation is understood scientifically and how strongly are societal actors aware of the problem and act upon it. The spectrum of how researchers planned that knowledge would reach its addressees comprised communicating results to interactive conceptions allowing for mutual learning throughout the research process. The typology reveals a variety of useful and promising project framings for sustainable development research. The typology may serve to reconcile conceptual ideals and expectations with researchers’ realities. 相似文献