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991.
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
992.
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
993.
Examining the potential impacts of sea level rise on coastal wetlands in north-eastern NSW,Australia
Clement Elumpe Akumu Sumith Pathirana Serwan Baban Daniel Bucher 《Journal of Coastal Conservation》2011,15(1):15-22
The coastal wetlands of north-eastern New South Wales (NSW) Australia are increasingly being affected by anthropogenic factors
such as urbanisation, residential development and agricultural development. However, little is known about their vulnerability
to sea level rise as a result of climate change. The aim of this research is to predict the potential impact of sea level
rise (SLR) on the coastal wetland communities. Sea Level Affecting Marshes Model (SLAMM) was used to predict the potential
impacts of sea level rise. Geographic Information System (GIS) was used for mapping and analysis. It was found that a meter
rise in sea level could decrease coastal wetlands such as Inland fresh marshes from about 225.67 km2 in February 2009 to about 168.04 km2 by the end of the century in north-eastern NSW, Australia. The outcomes from this research can contribute to enhancing wetland
conservation and management in NSW. 相似文献
994.
Jorge A. Achcar Eliane R. Rodrigues Guadalupe Tzintzun 《Environmental and Ecological Statistics》2011,18(2):271-290
In this paper we make use of some stochastic volatility models to analyse the behaviour of a weekly ozone average measurements
series. The models considered here have been used previously in problems related to financial time series. Two models are
considered and their parameters are estimated using a Bayesian approach based on Markov chain Monte Carlo (MCMC) methods.
Both models are applied to the data provided by the monitoring network of the Metropolitan Area of Mexico City. The selection
of the best model for that specific data set is performed using the Deviance Information Criterion and the Conditional Predictive
Ordinate method. 相似文献
995.
Modelling volatility of growth rate in atmospheric carbon dioxide concentrations in a Bayesian approach 总被引:1,自引:1,他引:0
Esmail Amiri 《Environmental and Ecological Statistics》2011,18(4):735-755
Atmospheric gases, such as carbon dioxide, ozone, methane, nitrous oxide, and etc., create a natural greenhouse effect and
cause climate change. Therefore, modelling behavior of these gases could help policy makers to control greenhouse effects.
In a Bayesian framework, we analyse and model conditional variance of growth rate in atmospheric carbon dioxide concentrations
(ACDC) using monthly data from a subset of the well known Mauna Loa atmosphere carbon dioxide record. The conditional variance
of ACDC monthly growth rate is modelled using the autoregressive conditional heteroscedasticity (ARCH), generalized ARCH model
(GARCH) and a few variants of stochastic volatility (SV) models. Smooth transition ARCH and GARCH models are shown to be able
to capture the dynamics in the conditional variance in ACDC level growth rate and to improve the forecast performance of ACDC
growth rate. 相似文献
996.
This paper introduces a flexible skewed link function for modeling ordinal response data with covariates based on the generalized
extreme value (GEV) distribution. Commonly used probit, logit and complementary log-log links are prone to link misspecification
because of their fixed skewness. The GEV link is flexible in fitting the skewness in the response curve with a free shape
parameter. Using Bayesian methodology, it automatically detects the skewness in the response curve along with the model fitting.
The flexibility of the proposed model is illustrated by its application to an ecological survey data about the coverage of
Berberis thunbergii in New England. We employ the latent variable approach by Albert and Chib (J Am Stat Assoc 88:669–679, (1993) to develop
computational schemes. For model selection, we employ the Deviance Information Criterion (DIC). 相似文献
997.
Graphical models provide an important tool for facilitating communication between scientists, decision-makers, and statisticians—many
complicated ecological processes can be described in terms of “box-and-arrow” conceptual diagrams (e.g., Shipley in Cause
and correlation in biology: a user’s guide to path analysis, structural equations and causal inferences, Cambridge Universtiy
Press, Cambridge, 2000; Clark and Gelfand TRENDS in Ecology and Evolution 21:375–380, 2006). In particular, problems in landscape
ecology often involve modeling relationships among multiple physical and/or biological variables that may operate on differing
spatial scales (e.g., Rossi et al. in Ecol Monographs 62:277–314, 1992; Legendre et al. in Ecography 25:601–615, 2002; Overmars
et al. in Ecol Model 164:257–270, 2003; Brown and Spector in J Appl Ecol 45:1639–1648, 2008; Koniak and Noy-Meir in Ecol Model
220:1148–1158, 2008). These problems are inherently multivariate, though researchers commonly rely on univariate methods,
such as spatial regression models, to address them. In this paper, we introduce a multivariate method—graphical spatial models—that
extends path analysis to incorporate spatial autocorrelation in one or more variables in a directed graph. We show how both
exogenous and endogenous ecological processes as defined by Legendre et al. (Ecography 25:601–615, 2002) and Lichstein et al.
(Ecol Monographs 72:445–463, 2002) can be represented in a graph. Most importantly, we show how to translate graphs representing
these ecological processes into statistically estimable models. We motivate our theoretical results using an example of stream
health data from the Willamette Valley, Oregon. For these data we are interested in the spatial pattern within both riparian
land use and an index of stream health, and whether there is an association between land use and stream health, after accounting
for these spatial patterns. We use a graphical spatial model to address these ecological questions simultaneously. We find
that the health of a stream decreases as the percent of developed land within a 120-m riparian buffer increases; interestingly,
there is only evidence of spatial pattern within land use. 相似文献
998.
We review a range of lack-of-fit tests suitable for assessing the appropriateness of the mean function in dose-response models.
The review encompasses both well-known tests and new tests based on recent developments in statistics, which we have extended
to the dose-response case. We argue that the classical methods are inadequate in certain situations, where the new tests may
be applied. Power comparisons are carried out by means of extensive simulation studies, covering both designs with and without
replicates at small and large sample sizes. Three datasets from dose-response applications illustrate differences and similarities
between the tests. The results suggest that the new tests perform better and exhibit a wider applicability. 相似文献
999.
With growing population and fast urbanization in Australia, it is a challenging task to maintain our water quality. It is
essential to develop an appropriate statistical methodology in analyzing water quality data in order to draw valid conclusions
and hence provide useful advices in water management. This paper is to develop robust rank-based procedures for analyzing
nonnormally distributed data collected over time at different sites. To take account of temporal correlations of the observations
within sites, we consider the optimally combined estimating functions proposed by Wang and Zhu (Biometrika, 93:459–464, 2006) which leads to more efficient parameter estimation. Furthermore, we apply the induced smoothing method to reduce the computational
burden. Smoothing leads to easy calculation of the parameter estimates and their variance-covariance matrix. Analysis of water
quality data from Total Iron and Total Cyanophytes shows the differences between the traditional generalized linear mixed
models and rank regression models. Our analysis also demonstrates the advantages of the rank regression models for analyzing
nonnormal data. 相似文献
1000.
José S. Antunes do Carmo Mechteld ten Voorde Maria G. Neves 《Journal of Coastal Conservation》2011,15(4):531-546
Surfing has becoming more and more attractive in the past few decades, constituting nowadays an important source of revenue
for many countries with extensive coastlines. For this purpose and also for environmental reasons, the conventional ways of
protecting a coastline appear to entail some disadvantages. An innovative and interesting way of improving surfing capacities
and contributing to protect a local coastal zone is by means of multifunctional artificial reefs. A multifunctional artificial
reef (MFAR) is a submerged structure that serves several purposes; in particular, it may enhance the surfing possibilities
and the environmental value of the local area. This structure has some promising new aspects, too: first, it provides an unimpaired
visual amenity; second, it offers tourist and economic benefits by improving the surfing conditions; third, it can enhance
the environmental value of the area where it is built, and fourth, if designed properly, the down drift erosion can be minimal.
An appropriate reef design in terms of ‘surfability’, i.e. the possibility to surf a wave, for the Leirosa beach, located
to the south of Figueira da Foz, midway along Portugal’s West Atlantic coast, has been investigated. In order to achieve the
best design several steps were conducted. First, the performance of the Boussinesq-type COULWAVE model is tested with experimental
data. Next, this numerical model is used to define the best values for three design parameters: reef angle; geometry of the
reef (without or with a platform), and horizontal dimensions for the appropriate geometry. A preliminary design was achieved
step by step, making use of the theory and of the state of the art of multifunctional reefs. This reef geometry is used in
the numerical study. In terms of ‘surfability’ and for the conditions of the local coastline of Leirosa, the following values
were found for the main parameters: a reef angle of 66°; a structure height of 3.20 m; a reef geometry composed of a delta
without a platform; a reef submergence of 1.50 m, and a structure seaward slope of 1:10. 相似文献