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21.
Small-scale habitat complexity, including that caused by biological structures, is an important factor in structuring benthic communities and also sometimes in increasing biodiversity. The aim of this study was to determine if hydroid colonies have an effect on the composition of benthic communities in the Irish Sea, and if so, which components of the fauna are affected. Forty-six seabed core samples were taken by divers from two sites off Port Erin, Isle of Man, Irish Sea. Half of these were centred on hydroid colonies, half were not. All taxa retained by a 63-m sieve from the cores were identified and counted. Community composition and diversity were compared between hydroid and non-hydroid cores using multivariate and univariate methods. Benthic communities were significantly different between the two sample groups. This was almost entirely due to the presence of sessile and mobile epifaunal taxa in the hydroid cores. The tube-building amphipod, Ericthonius punctatus, was particularly abundant attached to the hydroid stems. Infauna was not significantly different between the two groups. Upright sessile epifauna may play a particularly important role in the Irish Sea as a settlement substrate for juvenile scallops (Pecten maximus and Aequipecten opercularis), which are an important fishery resource in this area. The 11-year closure of an area to dredging has not only enhanced scallop stocks but has had the added benefit of enhancing habitat complexity and biodiversity.Communicated by J.P. Thorpe, Port Erin 相似文献
22.
Mysids are important components of the zooplankton biomass of estuaries and coastal regions. Twelve species were identified from the Bristol Channel and Severn Estuary (British Isles). The most abundant species wasSchistomysis spiritus (Norman), the majority of which occurred in the Channel within a salinity range of 27 to 34 S. The seasonal distribution and numerical abundance of this species are described over the period November 1973 to February 1975. The peak of abundance ofS. spiritus occurred in the Inner Channel in September (mean of 14 individuals m-3, ca. 250 individuals m-2 for this sub-region) when it represented 76% of the omnivore biomass (g C m-3); for the 364 d from 4 November 1973, the species contributed 43% of the total integrated omnivore standing stock. This peak of biomass was the product of the development of the juveniles from the reproductive period in the spring. Correlation analyses were carried out betweenS. spiritus biomass and 10 physical and biotic variables for 2 mo, November 1973 and September 1974. Temperature and salinity, which are simple indices of seasonal change, exhibited significant correlations with the mysid's abundance in both months. These correlations do not necessarily imply causal relationships or mechanisms between the distribution and abundance of the species and these variables. Clearly, in such a complex environment as an estuarine ecosystem a single variable is unlikely to control the abundance of a species, it is more the result of the combined influence of a number of variables acting in concert. 相似文献
23.
Zooplankton of the Bristol Channel and Severn Estuary. The distribution of four copepods in relation to salinity 总被引:3,自引:0,他引:3
The seasonal variations in distribution and abundance of the common zooplankton species in the Bristol Channel and Severn Estuary were related to the salinity regimes observed over the period November 1973 to February 1975. The dominant constituents in all regions were the calanoid copepods, which reached maximum densities in July: approximately 100 times their winter levels. Four zooplankton assemblages were recognised using an objective classification program which computed similarity coefficients and used group-average sorting. The assemblages existed along the salinity gradient observed from the Severn Estuary to the Celtic Sea. The assemblages were classified as true estuarine, estuarine and marine, euryhaline marine and stenohaline marine and were characterized by the copepods Eurytemora affinis (Poppe) (<30S), Acartia bifilosa var. inermis (rose) (27 to 33.5S), Centropages hamatus (Lilljeborg) (31 to 35S) and Calanus helgolandicus (Claus) (>33S), respectively. 相似文献
24.
Enrico Cappellini M. Thomas P. Gilbert Filippo Geuna Girolamo Fiorentino Allan Hall Jane Thomas-Oates Peter D. Ashton David A. Ashford Paul Arthur Paula F. Campos Johan Kool Eske Willerslev Matthew J. Collins 《Die Naturwissenschaften》2010,97(2):205-217
We report here the first integrated investigation of both ancient DNA and proteins in archaeobotanical samples: medieval grape (Vitis vinifera L.) seeds, preserved by anoxic waterlogging, from an early medieval (seventh–eighth century A.D.) Byzantine rural settlement in the Salento area (Lecce, Italy) and a late (fourteenth–fifteenth century A.D.) medieval site in York (England). Pyrolysis gas chromatography mass spectrometry documented good carbohydrate preservation, whilst amino acid analysis revealed approximately 90% loss of the original protein content. In the York sample, mass spectrometry-based sequencing identified several degraded ancient peptides. Nuclear microsatellite locus (VVS2, VVMD5, VVMD7, ZAG62 and ZAG79) analysis permitted a tentative comparison of the genetic profiles of both the ancient samples with the modern varieties. The ability to recover microsatellite DNA has potential to improve biomolecular analysis on ancient grape seeds from archaeological contexts. Although the investigation of five microsatellite loci cannot assign the ancient samples to any geographic region or modern cultivar, the results allow speculation that the material from York was not grown locally, whilst the remains from Supersano could represent a trace of contacts with the eastern Mediterranean. 相似文献
25.
Jonathan Pearson G. Punzo M. Mayfield G. Brighty A. Parsons P. Collins S. Jeavons A. Tagg 《The Environmentalist》2018,38(3):318-329
Flood resilience has been rising up the political, economic and social agendas. Taking an integrated systems approach, using the right design guidance and tools and ensuring that education is in place for all stakeholders are three themes which are intrinsically linked to delivering flood resilience. This paper reviews these themes across the academic research, policy landscape and practitioner approaches, drawing conclusions on the way forward to increase our societies resilience to floods. The term ‘flood resilience’ is being increasingly used, however, it remains to be clearly defined and implemented. The UK, USA and Australia are leading the way in considering what flood resilience really means, but our review has found few examples of action underpinned by an understanding of systems and complexity. This review investigates how performance objectives & indicators are currently interpreted in guidance documents. It provides an in-depth exploration of the methods, that although developed through European and US expertise, can be used for worldwide application. Our analysis highlights that resilience is often embedded in engineering education and frequently linked to risk. This may however, mask the importance of resilience and where it differs from risk. With £2.6 billion to be spent in the UK over the next 6 years on strengthening the country’s flood and coastal defences, this is the opportunity to rethink resilience from a systems approach, and embed that learning into education and professional development of engineers. Our conclusions indicate how consolidating flood resilience knowledge between and within critical infrastructure sectors is the way forward to deliver flood resilience engineering. 相似文献
26.
Inês Carvalho Jacqueline Loo Timothy Collins Jaco Barendse Cristina Pomilla Matthew S. Leslie Solange Ngouessono Peter B. Best Howard C. Rosenbaum 《Marine Biology》2014,161(4):805-819
Humpback whales (Megaptera novaeangliae) in the Southeastern Atlantic Ocean (International Whaling Commission ‘Breeding Stock B’—BSB) are distributed from the Gulf of Guinea to Western South Africa. Genetic data suggest that this stock may be sub-structured, but it remains unknown if this is due to reproductive segregation. This paper evaluates the spatial and temporal population structure of BSB humpback whales using a combination of maternally and bi-parentally inherited markers. The genetic differentiation that we identify in this study could be due to a combination of (1) spatial and/or temporal segregation on breeding grounds in the greater Gulf of Guinea, (2) the possibility of maternally inherited site fidelity to specific feeding grounds and (3) the use of two generalized but exclusive migratory routes (coastal and offshore) between feeding and breeding areas. Further, photo-identification and genetic sampling efforts in other areas of the Sub-Saharan Western Africa winter range and targeted deployment of satellite tags would help to clarify some of the apparent complexity in the population structure of animals biopsied in this region. 相似文献
27.
28.
Groundwater overdraft is a resource management issue that poses a threat for the security of communities. Impacts of groundwater overdraft are influenced by the biophysical and social contexts of water management. This paper presents a method for assessing vulnerability to water scarcity in spatial terms using biophysical and social indicators. A geographic information system was used to establish areas of vulnerability based upon hydrologic variability in water resource availability within a groundwater basin, three types of water management systems, and 10 sociodemographic characteristics. Our study area is in the rapidly urbanizing Arizona Central Highlands, located ~150km north of the Phoenix metropolitan region, USA. Results indicate that the most biophysically vulnerable places do not necessarily intersect with the most vulnerable populations and that local differences in vulnerability are interrelated, rather than independent, outcomes in a process of socioenvironmental transformation. Vulnerability is influenced by laws that deny access to local surface waters and lead to dependence on fossil groundwater, and by economic reliance on urbanization. Localities attempt to reduce vulnerability through the development of community water systems and the expansion of water frontiers. While such strategies may reduce local vulnerability, they are not sustainable solutions because they transfer risks to other places, and thus contribute to vulnerability elsewhere. 相似文献
29.
Claire M. Waluda Martin A. Collins Andrew D. Black Iain J. Staniland Philip N. Trathan 《Marine Biology》2010,157(1):99-112
Antarctic fur seals Arctocephalus gazella and macaroni penguins Eudyptes chrysolophus are the two main land-based krill Euphausia superba consumers in the northern Scotia Sea. Using a combination of concurrent at-sea (predator observations, net hauls and multi-frequency
acoustics), and land-based (animal tracking and diet analysis) techniques, we examined variability in the foraging ecology
of these sympatric top predators during the austral summer and autumn of 2004. Krill availability derived from acoustic surveys
was low during summer, increasing in autumn. During the breeding season, krill occurred in 80% of fur seal diet samples, with
fish remains in 37% of samples. Penguin diets contained the highest proportion of fish in over 20 years of routine monitoring
(46% by mass; particularly the myctophid Electrona antarctica), with krill (33%) and amphipods (Themisto gaudichaudii; 21%) also occurring. When constrained by the need to return and feed their offspring both predator species foraged to the
northwest of South Georgia, consistent with an area of high macrozooplankton biomass, but fur seals were apparently more successful
at exploiting krill. When unconstrained by chick-rearing (during March) penguins foraged close to the Shag Rocks shelf-break,
probably exploiting the high daytime biomass of fish in this area. Penguins and seals are able to respond differently to periods
of reduced krill abundance (in terms of variability in diet and foraging behaviour), without detriment to the breeding success
of either species. This highlights the importance of myctophid fish as an alternative trophic pathway for land-based predators
in the Scotia Sea ecosystem. 相似文献
30.
Rarefaction estimates how many species are expected in a random sample of individuals from a larger collection and allows
meaningful comparisons among collections of different sizes. It assumes random spatial dispersion. However, two common dispersion
patterns, within-species clumping and segregation among species, can cause rarefaction to overestimate the species richness
of a smaller continuous area. We use field studies and computer simulations to determine (1) how robust rarefaction is to
nonrandom spatial dispersion and (2) whether simple measures of spatial autocorrelation can predict the bias in rarefaction
estimates. Rarefaction does not estimate species richness accurately for many communities, especially at small sample sizes.
Measures of spatial autocorrelation of the more abundant species do not reliably predict amount of bias. Survey sites should
be standardized to equal-sized areas before sampling. When sites are of equal area but differ in number of individuals sampled,
rarefaction can standardize collections. When communities are sampled from different-sized areas, the mean and confidence
intervals of species accumulation curves allow more meaningful comparisons among sites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Daniel SimberloffEmail: |