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111.
Maria Clara P. Amorim José Miguel Simões Vitor C. Almada Paulo J. Fonseca 《Behavioral ecology and sociobiology》2011,65(4):707-716
Signal attributes should show different degrees of variability depending on the information to be conveyed. Species identity
is usually associated with stereotyped features of a signal, whereas other types of information such as individual quality
and motivation are associated with signal plasticity. Lusitanian toadfish males form aggregations during the breeding season
and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle
can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study
how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement
signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian
toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male
signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could
still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among
males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide
on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest
that inter-individual differences in call characteristics and call plasticity may mediate both male–male assessment and mate
choice. 相似文献
112.
This paper describes the application of coastal hydro-informatic modelling (using the TELEMAC Modelling System) to address
management issues arising from projected hydrodynamical and morphological changes within a shallow, sandy estuarine environment.
The model incorporates the complex interaction of ocean, terrestrial and atmospheric processes. The case study of the Dyfi
Estuary, on the west coast of Wales, is highlighted here. As sea levels have risen locally and are predicted to rise further,
a National Nature Reserve (Borth Bog), which has been reclaimed from tidal waters by embankments, will be at increasing risk
from flooding episodes due to overtopping of these embankments at high tide. Present and predicted future tidal-fluvial scenarios
have been modelled in the Dyfi Estuary in order to estimate the potential for flooding. In addition, areas of greatest velocity
change and potential for sediment erosion/accretion have been identified. A further process that has been investigated is
how salt marsh migration is affected by sea-level rise. This case study exemplifies some fundamental and complex physical
processes inherent to estuaries, and shows how different management options can be assessed, before their implementation,
through a modelling approach. 相似文献
113.
Sam Provoost M. Laurence M. Jones Sally E. Edmondson 《Journal of Coastal Conservation》2011,15(1):207-226
In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape
and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated
with geomorphological stability. The historical development of dune woodland during these stable phases has been documented
for sites all over Europe. Vegetation reconstructions of historical open dune habitats however is very difficult due to limited
preservation of fossil remains. People have drastically altered coastal dune landscapes through centuries of exploitation
and more recently development of the coast. Historical land use has generally pushed vegetation back into a semi-natural state.
During roughly the past century a tendency of increasing fixation and succession is observed on coastal dunes throughout northwest
Europe. Six causes of change are discussed. 1) Changes in land use, mainly abandonment of agricultural practices, have led
to the development of late successional stages such as scrub and woodland. 2) Crashing rabbit populations due to myxomatosis
in the 1950s caused vigorous grass growth and probably stimulated scrub development. 3) A general tendency of landscape fixation
is observed due to both natural and anthropogenic factors. 4) Eutrophication, mainly due to atmospheric nitrogen deposition
is clearly linked to grass encroachment on acidic but also on some calcareous dunes. 5) The impact of climate change on vegetation
is still unclear but probably lengthening of growing season and maybe enhanced CO2 concentrations have led to an acceleration of succession. 6) A general anthropogenisation of the landscape occurs with rapid
spread of non-native species as an important consequence. The reconstruction of a natural reference landscape is considered
largely unattainable because of irreversible changes and the long tradition of human impact, in many cases since the development
of the dunes. Two contradictory elements need reconciliation. First, the general acceleration of succession and scrub and
woodland development in particular is partly caused by a decreased anthropogenic interference in the landscape and deserves
more appreciation. Second, most biodiversity values are largely linked to open, early succession dune habitats and are threatened
by the same tendency. Apart from internal nature management, in which grazing plays an important part, re-mobilisation of
stable, senescent dunes is an important challenge for dune management. 相似文献
114.
The Turks and Caicos Islands are currently in the midst of an economic revolution from a marine-based provisional economy to a tourism economy. East Bay, South Caicos, is currently under construction with plans for a 160-unit condominium complex. Included in the project plan is removal of seagrass beds in front of the development to make a sandy beach for tourists. The aims of this study were to (i) describe the bathymetry and benthic habitat coverage of East Bay before dredging takes place and (ii) perform an economic valuation on the turtle grass beds that will be dredged using ecosystem valuation and emergy analysis techniques. The bathymetry survey revealed shallow waters (<1.5 m) until the reef drop off (~650 m offshore). Benthic habitat exhibits zonation following the general progression: sand plain, algal plain, seagrass, coral rubble and seagrass, rock and turf algae, and reef flat. Ecosystem services valued the proposed dredging area at USD $28,807 per year, compared to emergy analysis, which valued the proposed dredging site at USD $32,060 per year. The baselines presented in the study may facilitate a quantitative assessment of dredging impacts on turtle grass once dredging is complete and an economical cost-benefit-analysis of the dredging project to see whether the economic gains outweigh the ecological costs of dredging in front of the East Bay development. 相似文献
115.
Danuta Baralkiewicz Hanka Gramowska Ryszard Gołdyn Wiesław Wasiak Katarzyna Kowalczewska-Madura 《Chemistry and Ecology》2013,29(2):93-103
Sediment samples were analysed for mercury and methylmercury content in different parts of the bottom sediment of Swarz ?dzkie Lake, which were influenced by different external pollution sources. The results of determination with two methods of mineralization using two separate media (HNO3/H2O2 and HF) were compared. The accuracy of the studied methods was analysed using certified reference material IAEA 405 of river sediment. The recovery of mercury was satisfactory and ranged from 97.5 to 98.8%. Methylmercury compounds in the studied sediments were found in limited concentrations. Their concentrations ranged from 0.26 to 58.1 μg kg?1, i.e. 1.0–7.4% of the total mercury content. The depth profile displayed high values of both total and methylmercury content at a depth of 10–20 cm, related to the heavy pollution of the lake in the 1980s. Canonical analysis displayed the relationship of both total mercury and methylmercury concentrations with organic matter and phosphorus content in bottom sediments. 相似文献
116.
In this study, selective methods were developed for isolation, purification, separation and determination of 4-nonylphenol (4NP) in biological samples. Several methods such as high-performance liquid chromatography (HPLC) with fluorescence and diode array detection and gas chromatography coupled to mass spectromotry (GC-MS) are described for the simultaneous determination of 4NP. The nonylphenols in the plasma of fish were extracted through solid phase process by using octadecyl, polymeric and octadecyl endcapping sorbents. The average recoveries in plasma samples spiked with 4NP of levels 1?µg?mL?1 were between 80–95% using added surrogate standards. The aim of this study was to determine whether trace amounts of 4NP in fish plasma samples could be detected by solid phase extraction and chromatographic methods (HPLC, GC-MS). This technique of monitoring the levels of endocrine-disruptors in plasma samples is consistent, reliable as well as inexpensive. 相似文献
117.
Krystyna A. Skibniewska Janusz Guziur Zbigniew Marzec Stanisław Zaręba Mirosław Grzybowski Józef Szarek 《毒物与环境化学》2013,95(4):773-778
Excessive intake of nickel (Ni) is known to produce adverse health effects in humans, including carcinogenicity and allergenicity. The main route of exposure for humans is diet, including fish. There is, however, little information concerning Ni content in freshwater fish in Poland. The aim of the study was to determine the concentrations of Ni in meat tissues of three fish species from north eastern Poland and assess toxic potential to healthy and susceptible sub-groups of individuals. The settings for the study lakes span a range of anthropogenic influence from protected areas to a basin with a town and several villages and another one influenced by a pesticide tomb leakage. Fish were netted and kept frozen until analysis. After defrosting, the fish were filleted and minced. The ashed samples were dissolved in nitric acid and analyzed for Ni by flame atomic absorption spectrometry. Roach meat contained 6.6–23 µg kg?1 Ni, bream 9.5–178 µg kg?1, and carp 16.5–139 µg kg?1. These concentrations are low, indicating that the fish were not excessively contaminated with the metal. Consuming a 250 g portion of fish would result in an average nickel intake of 4 µg for roach, <10 µg for bream, and <20 µg for carp. These values represent only 0.4–2% of the maximum level that is likely to pose a risk of adverse effects as established in the USA. Consumption of fish from the study region need not necessarily pose a health threat. 相似文献
118.
Catecholamines and their metabolites affect children's nervous system. Dopamine is an important neurotransmitter in the brain. In the routine analysis for diagnostics of diseases, the dopamine metabolite homovanillic acid (HVA) is determined. Mercury is a neurotoxic agent and can cause different undesirable effects on the brain. In the present work a putative correlation between HVA, the main metabolite of dopamine, and mercury in urine of healthy and autistic children was studied. The level of HVA was higher in the urine of autistic children (14.5 ± 8.3 mg L?1) compared to generally healthy children (4.4 ± 0.5 mg L?1). The level of mercury in the urine of autistic children was lower (0.36 ± 0.24 µg L?1) than in the urine of healthy children (2.1 ± 1.0 µg L?1) showing that there is no correlation between HVA and mercury. 相似文献
119.
Daniela Marques Ana I. Esteves Marise Almeida Joana Xavier Madalena Humanes 《Marine Biology》2008,153(5):807-813
The aim of this work is to investigate the activity of the antioxidant enzyme superoxide dismutase in the cosmopolitan sponge
Cliona celata (Grant, 1826), since this enzyme has been described as a useful biomarker for marine pollution in other marine invertebrates.
The quantification of the catalytic activity for superoxide dismutase is quite complex because its substrate is an unstable
free radical. Several methods have been developed for this enzymatic activity determination; most of them are based on inhibition
of a redox reaction involving the superoxide radical. In this work, two methods are compared, for crude sponge extracts, as
far as repeatability, reproducibility and sensibility are concerned. The adrenaline oxidation method seems to be the most
adequate for these determinations. Statistical treatment of the data indicates that the reference value for the specific superoxide
dismutase activity in C. celata should be in the interval [0–535.5] U/mg of total protein in wet tissues, for normal populations. 相似文献
120.
Many South African populations of the brown mussel Perna perna have been depleted through over-exploitation by subsistence harvesters. This is problematic because recovery after disturbance
is very slow, partly because recruits are largely associated with adult mussels. However, unlike large recruits of 3.5–10 mm
that exhibit spatial structure related to that of adults, a very high proportion of settlers and small recruits (0–3.5 mm)
occur on foliose algae. We tested the hypothesis that recruits on algae move to adult mussel beds after a period of growth,
with the null hypothesis that they die at a certain size. We conducted an indirect field study comparing the ratios of large
to small recruits in 100% cover mussel patches at locations with high and low algal cover. A second laboratory experiment
analysed whether the size of recruits on algae affects their active movement behaviour in response to nearby mussel patches.
Large/small recruit ratios were slightly, but not significantly greater in high than low algal cover locations. Both small
(2–2.5 mm) and medium (4.5–5.5 mm) recruits remained on algae and moved very short distances throughout the laboratory experiment,
while larger recruits (9–10 mm) moved significantly further distances and more often into mussel patches. The results suggest
that very large recruits are able to migrate actively to nearby mussel patches, indicating ontogenetic shifts in this behaviour.
However, the absence of a significant difference in ratios between field locations with high and low algal cover suggests
many large recruits are accidentally dislodged from the algae and presumably die. Thus settlement of P. perna onto algae is likely to be wasted, with consequences for sustainable management of the mussel resource. 相似文献