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891.
Rosenbom AE Ernstsen V Flühler H Jensen KH Refsgaard JC Wydler H 《Journal of environmental quality》2008,37(2):448-458
The study of mechanisms controlling preferential flow and transport in variably saturated fractured clayey till is often hindered by insufficient spatial resolution or unknown measuring volume. With the objective to study these mechanisms while circumventing the obstacles, tracer experiments with two fluorescent tracers Acid Yellow 7 (AY7) and Sulforhodamine B (SB) were performed at three different rain events for a fall and a summer season. Irrigated areas were excavated down to depths of 2.8 m and the movement of both tracers in the exposed profiles was delineated simultaneously by high spatial resolution apparent concentration maps (pixel approximately 1 mm(2)) obtained with an imaging device. The device consists of a light source and a CCD camera, both equipped with tracer-specific-filters for fluorescent light. The fluorescence images were corrected for nonuniform lighting, changing surface roughness, and varying optical properties of the soil profile. The resulting two-dimensional apparent concentration distribution profiles of the tracers showed that: (i) relative low water content in the upper 10 cm of the irrigated till in summer had a pronounced retardation effect on the AY7-migration and no effect on the SB-migration; (ii) the dead-end biopores were not activated in the fall season; (iii) only 3D fracture-plans connected to hydraulically active 1D-biopores contributed to the leaching; (iv) the tracer migration primary followed macropores during both seasons, though AY7 also followed a topsoil piston transport in summer; (v) the highest tracer pixel apparent concentrations were often found in macropores and most pronounced in the summer season; and (vi) 3D-dilution in fractures seems to play a dominating role in AY7-migration in the fall season. 相似文献
892.
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
893.
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
894.
Maria H. G. Canteri Agnes P. Scheer Gilvan Wosiacki Christian Ginies Marise Reich Catherine M. C. G. Renard 《Journal of Polymers and the Environment》2010,18(4):593-599
Brazil is the world’s main producer of passion fruit. Previous reports show that passion fruit rinds, an industrial waste,
contain large amounts of pectin. Pectin is a dietary fiber that is widely used in the food industry as a gelling agent and
stabilizer. In this study, the quality and characteristics of pectin extracted from yellow passion fruit rind flour was investigated.
Pectin was extracted from both commercially available and prepared passion fruit peels using nitric acid. Once extracted,
the pectin was evaluated for its molecular characteristics and chemical composition as well as for the apparent and reduced
viscosity of the gel. Prepared (blanched) rind flour yielded 203.4 g kg−1 of pectin, which contained a uronic acid content of 681 mg g−1, a degree of esterification of 80, a degree of methylation of 80, a reduced viscosity of 6.8 dL g−1 and an apparent viscosity of 13.4 cP. The results suggest a clear influence of the raw material on it’s the resultant characteristics
of the pectin. In addition, our results show that therheological properties and molar characteristics of pectin were negatively
affected when the rind flours were subjected to high temperatures. Pectin methyl esterase activity was detected in the freeze-dried,
unblanched raw material. Extensive efforts have been directed towards minimizing waste and the reported results show that
high quality pectin can be obtained from passion fruit rinds, an industrial waste product of passion fruit processing. 相似文献
895.
Christian Brodhag 《Natural resources forum》2010,34(1):63-70
The importance of sustainable consumption and production in the international agenda has been growing, both because of unsustainable patterns of consumption and production in industrialized countries and because it appears to be a means for meeting the essential needs of developing countries. Adapting Fernand Braudel's model of the three layers of the economy (everyday life, market economy and global capitalism) to the current situation, this paper advocates for differentiated policies, which cannot be limited to those based on the dominant model of a rational legal system dealing with rational consumers. The cultural and collective dimensions of consumption, the social role of conspicuous consumption, the consumption of ecological services outside formal markets, the diversity of approaches to knowledge and rationality, all plead for an overarching approach and diversified policy tools. The paper underlines the need for global regulation processes which involve all stakeholders by focusing on two examples: the international task force on sustainable tourism, and the ISO 26000 standard on social responsibility. 相似文献
896.
Kati Berninger Wiktor Adamowicz Daniel Kneeshaw Christian Messier 《Environmental management》2010,46(1):117-133
The challenge of sustainable forest management is to integrate diverse and sometimes conflicting management objectives. In
order to achieve this goal, we need a better understanding of the aspects influencing the preferences of diverse groups and
how these groups make trade-offs between different attributes of SFM. We compare the SFM preferences of interest groups in
regions with different forest use histories based on the reasoning that the condition of the forest reflects the forest use
history of the area. The condition of the forest also shapes an individual’s forest values and attitudes. These held values
and attitudes are thought to influence SFM preferences. We tested whether the SFM preferences vary amongst the different interest
groups within and across regions. We collected data from 252 persons using a choice experiment approach, where participants
chose multiple times among different options described by a combination of attributes that are assigned different levels.
The novelty of our approach was the use of choice experiments in the assessment of regional preference differences. Given
the complexity of inter-regional comparison and the small sample size, this was an exploratory study based on a purposive
rather than random sample. Nevertheless, our results suggest that the aggregation of preferences of all individuals within
a region does not reveal all information necessary for forest management planning since opposing viewpoints could cancel each
other out and lead to an interpretation that does not reflect possibly polarised views. Although based on a small sample size,
the preferences of interest groups within a region are generally statistically significantly different from each other; however
preferences of interest groups across regions are also significantly different. This illustrates the potential importance
of assessing heterogeneity by region and by group. 相似文献
897.
A new species has recently invaded coastal dune ecosystems in North West Europe. The native and expansive inland grass, Deschampsia flexuosa, progressively dominating inland heaths, has recently invaded coastal dunes in Denmark, occasionally even as a dominant species.
A total of 222 coastal locations with 5,000 random sample plots have been investigated. These findings are in contrast to
historical records, and D. flexuosa has never been considered belonging to coastal dune ecosystems. The occurrence of the typical inland grass in the coastal
dunes is a strong indication of increase in nutrient level and that human influences may cause a native species to be invasive
in new ecosystems. This could be a radical example of change in species composition due to a long lasting exceedance of critical
load of nitrogen. The investigation also showed a general increase in cover of the most dominant species. 相似文献
898.
Stream Condition in Piedmont Streams with Restored Riparian Buffers in the Chesapeake Bay Watershed1
Leslie L. Orzetti R. Christian Jones Robert F. Murphy 《Journal of the American Water Resources Association》2010,46(3):473-485
Orzetti, Leslie L., R. Christian Jones, and Robert F. Murphy, 2010. Stream Condition in Piedmont Streams with Restored Riparian Buffers in the Chesapeake Bay Watershed. Journal of the American Water Resources Association (JAWRA) 46(3):473-485. DOI: 10.1111/j.1752-1688.2009.00414.x Abstract: This study tested the efficacy of restored forest riparian buffers along streams in the Chesapeake Bay watershed by examining habitat, selected water quality variables, and benthic macroinvertebrate community metrics in 30 streams with buffers ranging from zero to greater than 50 years of age. To assess water quality we measured in situ parameters (temperature, dissolved oxygen, and conductivity) and laboratory-analyzed grab samples (soluble reactive phosphorus, total phosphorus, nitrate, ammonium, and total suspended solids). Habitat conditions were scored using the Environmental Protection Agency Rapid Bioassessment Protocols for high gradient streams. Benthic macroinvertebrates were quantified using pooled riffle/run kick samples. Results showed that habitat, water quality, and benthic macroinvertebrate metrics generally improved with age of restored buffer. Habitat scores appeared to stabilize between 10 and 15 years of age and were driven mostly by epifaunal substrate availability, sinuosity, embeddedness, and velocity depth regime. Benthic invertebrate taxa richness, percent Ephemeroptera, Plecoptera, Trichoptera minus hydropsychids (%EPT minus H), % Ephemeroptera, and the Family Biotic Index were among the metrics which improved with age of buffer zone. Results are consistent with the hypothesis that forest riparian buffers enhance instream habitat, water quality, and resulting benthic macroinvertebrate communities with noticeable improvements occurring within 5-10 years postrestoration, leading to conditions approaching those of long established buffers within 10-15 years of restoration. 相似文献
899.
Christian Vogel Camille Rivard Verena Wilken Andreas Muskolus Christian Adam 《Ambio》2018,47(1):62-72
A pot experiment was carried out with maize to determine the phosphorus (P) plant-availability of different secondary P-fertilizers derived from wastewater. We analyzed the respective soils by P K-edge X-ray absorption near-edge structure (XANES) spectroscopy to determine the P chemical forms that were present and determine the transformation processes. Macro- and micro-XANES spectroscopy were used to determine the chemical state of the overall soil P and identify P compounds in P-rich spots. Mainly organic P and/or P adsorbed on organic matter or other substrates were detected in unfertilized and fertilized soils. In addition, there were indications for the formation of ammonium phosphates in some fertilized soils. However, this effect was not seen in the maize yield of all P-fertilizers. The observed reactions between phosphate from secondary P-fertilizers and co-fertilized nitrogen compounds should be further investigated. Formation of highly plant-available compounds such as ammonium phosphates could make secondary P-fertilizers more competitive to commercial phosphate rock-based fertilizers with positive effects on resources conservation. 相似文献
900.
Christian P. Andersen Wilma Ritter Rainer Matyssek 《Environmental pollution (Barking, Essex : 1987)》2010,158(8):2604-2609
Canopies of adult European beech (Fagus sylvatica) and Norway spruce (Picea abies) were labeled with CO2 depleted in 13C to evaluate carbon allocation belowground. One-half the trees were exposed to elevated O3 for 6 yrs prior to and during the experiment. Soil-gas sampling wells were placed at 8 and 15 cm and soil CO2 was sampled during labeling in mid-late August, 2006. In beech, δ13CO2 at both depths decreased approximately 50 h after labeling, reflecting rapid translocation of fixed C to roots and release through respiration. In spruce, label was detected in fine-root tissue, but there was no evidence of label in δ13CO2. The results show that C fixed in the canopy rapidly reaches respiratory pools in beech roots, and suggest that spruce may allocate very little of recently-fixed carbon into root respiration during late summer. A change in carbon allocation belowground due to long-term O3 exposure was not observed. 相似文献