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171.
In 1990 the Dutch government decided to stop any further long-term landward retreat of the coastline. This policy choice for
a ‘dynamic preservation’ is primarily aimed at safety against flooding and at sustainable preservation of the values and interests
concerning the dunes and beaches. Five years later, a first overview of the benefits and bottlenecks of the new coastal defence
policy could be presented, which was published in the second governmental coastal report ‘Kustbalans 1995’ (coastal balance
1995). This consists of three elements: (1) evaluation of the implementation of ‘dynamic preservation’, (2) the consequences
of several natural and anthropogenic developments in the coastal zone and (3) integrated coastal zone management. The present
report describes experiences of Dutch coastline management and summarizes the main conclusions of the second governmental
report.
The overall conclusion of the evaluation study is that the 1990 choice for ‘dynamic preservation’ was right. Sand supply is
an effective method of coastline maintenance, which also serves functional uses in the beach and dune area. However, nearly
a doubling of the supply volume is necessary to compensate for sand losses in the coastal zone. A more integrated management
of the coastal zone is necessary to find an equilibrium between the interests of socio-economic development and the maintenance
of a natural, dynamic system. 相似文献
172.
Coral reefs are highly dynamic and productive marine ecosystems, providing habitat and refuge for an enormous number of species
including fish, invertebrates and algae. With increased anthropogenic pressures and global climate change, many coral reefs
are rapidly declining. Currently, there is limited knowledge on condition and community assemblage composition of shallow
fringing coral reefs along the south-eastern coast of Queensland, Australia. With increased demand to determine existence
of coastal fringing reefs by National Regional Management groups, a rapid cost effective method to determine reef composition
and condition was required. The aim of this study was to determine the benthic structure and extent of two small coastal fringing
reefs (Hummock Hill Reef and Stringers Reef) along the Southern Great Barrier Reef. Reef substrate assessments were carried
out using a rapid assessment technique and a Point Intercept Method (PIM). The data were analysed and classified using a Geographic
Information System (GIS). Percent substrate cover was calculated using a visual basic image analysis program. The Point intercept
method showed higher accuracy over the rapid assessment technique (up to 15–40% difference) and was thus deemed a more suitable
classification tool for reefs with high structural complexity and heterogeneity. This study focused on piloting a rapid, cost
effective Point Intercept Technique using random point count methodology to document coral benthic habitat and extent over
a commonly used rapid assessment method as a tool for reef coastal management and conservation. The two techniques were compared
and substrate classification success, limitations and errors were discussed. 相似文献
173.
R. E. Randall 《Journal of Coastal Conservation》2004,10(1):159-168
Coastal vegetated shingle is a rare and declining resource worldwide but is found extensively around the UK coastline. Shingle
sediments b-axes range between 2 mm and 200 mm and occur as fringing beaches, bars, spits, barrier islands and forelands.
Sediment patterns are dependent upon accretion or erosion. With sea-level rise, shingle features tend to move inland. Larger
features may support reservoirs of fresh water but risk becoming saline with sea-level rise. Ranker soils may develop but
are naturally fragile. Vegetated shingle communities are dependent upon substrate stability, moisture and nutrient availability.
Only specialized and some ruderal plants can persist in patterns dependent upon geomorphic history. Coastal defence, agriculture,
public access and control of alien species are important factors in habitat management. Because of its dynamic and unusual
nature coastal vegetated shingle is an important habitat for environmental education. 相似文献
174.
Some organisms use morphological structures obtained by behavioural processes to lower mortality by predation. We test whether
larvae of the limnephilid caddisfly Potamophylax latipennis (Curtis) vary their responses to the presence of different predators (dragonfly naiads, fire salamander larvae or brown trout)
by choosing organic or mineral cases. We offered both case types to larvae, and simulated differences in predation risk using
water conditioned with chemicals from the different predators. Our results show that Potamophylax larvae detect and discriminate predators using water-borne chemical cues and alter their choice of case type according to
the perceived predation risk. Moreover, the distribution of larvae bearing cases of different anti-predator value matches
the spatial variation in predation risk in the field. 相似文献
175.
Summary. The plant apparency hypothesis predicts that apparent plants invest in broadly effective defences such as tannins while unapparent
plants invest in specific toxins such as alkaloids. The stress hypothesis states that plants invest in cheaper defences if
they have evolved in habitats that impose abiotic limitations to plant fitness. We tested these hypotheses by determining
the concentrations of alkaloids and tannins in a representative sample of the vascular plants of continental Chile (with exclusion
of Pteridophyta, Cactaceae, and Poaceae) consisting of 396 species. In a subsample of 166 species which contained both alkaloids
and tannins, we constructed the A/T index (A/T = [alkaloids]/ [tannins]). We discarded the presumed effect of phylogeny (as
estimated by taxonomy) on the variation observed in the data because no correlation of A/T with taxonomic relationships among
species either at family or genus levels was found in a nested ANOVA with genera nested in families. Concentration of alkaloids
was negatively correlated with that of tannins. We compared the value of A/T among species differing in life form (herbs,
shrubs or trees), herb longevity (annual or perennial), leaf-shedding manner of woody plants (deciduous or evergreen), latitudinal
range, and level of water stress typical in their natural habitat. Unapparent plants (herbs, annual) exhibited higher mean
A/T index than apparent plants (shrubs and trees, perennial). A/T did not correlate with latitudinal range. Mean A/T values
decreased from deserts to deciduous forests. The comparisons were not always significant due to the inevitable unbalance of
the data set which lowers the power of the statistical tests employed. The results suggest that chemical defences are indeed
distributed in a non-random manner among plants, and that to a large extent the predictions derived from the apparency and
stress hypotheses are sustained. 相似文献
176.
Analyses have been undertaken to examine shoreline positions established from remote sensing data along the northwestern part
of the Nile delta from the Abu Qir Bay to Gamasa embayment (∼143 km length). The image data used (MSS, TM and ETM+ sensors)
are acquired at unequal intervals between 1972 and 2006, i.e., covering a time span of 34 years. Automated waterline positions
extracted from Landsat satellite images during this period of time were computer generated. A digital shoreline analysis software
was used to calculate the annual rate of beach changes at 1,432 cross-shore transects prior to (1972–1990) and after protection
(1993–2006). On comparison, rates estimated from three statistical approaches (the end point rate, the Jackknife and a weighted
linear regression) at corresponding positions are successfully validated with those measured from ground survey. Before protection,
results reveal longshore patterns wherein erosion along a coastal stretch gives way to accretion in an adjacent stretch, refining
the sub-cells previously identified within the littoral system of the delta. Maximum shoreline retreat occurs along the Rosetta
promontory (−138.52 m/year) and along the central bulge of the delta at Burullus headland (−6.07 m/year). In contrast areas
of shoreline accretion exist within saddles or embayments between the promontories at west Abu Qir Bay (20.04 m/year), Abu
Khashaba saddle (16.17 m/year) and Gamasa embayment (20.68 m/year). These rates of changes have been significantly altered
by the construction of intensive shoreline protective structures built from 1990 to combat areas of rapid erosion at both
the Rosetta promontory and Burullus–Baltim headland, ∼15-km length in total. 相似文献
177.
A GIS-based vulnerability assessment of coastal natural hazards,state of Pará, Brazil 总被引:1,自引:0,他引:1
Studies carried out in the NE coastal zone of the State of Pará (Brazil) have recorded, in the last 25 years, numerous evidence
of natural impacts of the flood and erosion processes. As a consequence, diverse strategies and measures of population adaptation
have been implemented but with limited success. Therefore, in order to subsidize the Coastal Zone Management Program of Pará,
this paper aims to identify, assess and classify natural and socio-economic vulnerabilities of this coastal zone by means
of a Geographical Information Systems (GIS)-based composite coastal vulnerability index (CVI). In spite of the data problems
and shortcomings, using ESRI’s Arcview 3.2 program, the CVI score, to classify, weight and combine a number of 16 separate
natural and socio-economic variables to create a single indicator provides a reliable measure of differences (5 classes) among
regions and communities that are exposed to similar ranges of hazards. The results are presented in three maps referred to
as Natural, Socioeconomic and Total Vulnerability. The confidence associated with the results obtained, the need to utilize
another variables, and to frequently update the ones used already were analyzed and discussed. 相似文献
178.
A short outline is given of the floristic composition, structure and distribution of coastal dune vegetation found at Malindi
Bay, Kenya. The area was studied by air photo interpretation and field sampling to determine the relationship of plants to
aeolian features. TWINSPAN classification was used to distinguish geomorphological units on the basis of their species composition.
In this paper, an inventory and first quantitative analysis of vegetation distribution is presented. We identified 174 plant
species from 62 families in the sand dunes and several plant communities are distinguished based on the species content and
the connection with morphological units.Papilionaceae with 18 species andPoaceae with 17 species were the most represented families. A distinct zonal distribution of the plant communities was found.
The most important plant species are the pioneer vegetation consisting ofHalopyrum mucronatum, Ipomoea pescaprae andScaevola plumieri. The woody shrub species which have colonized the established primary dunes and hummock dunes areCordia somaliensis, Pluchea discoridis, Tephrosia purpurea (dunensis). Succulent herbs were identified in the dune slacks and salt marsh that are moist and damp environments. 相似文献
179.
Baseline resource information in an easily accessible form is a vital starting point for developing coastal zone management.
On behalf of a wide-ranging group of organizations involved in the management of the U.K. maritime zone, the Joint Nature
Conservation Committee (JNCC) is compiling a series of 16 regional volumes. The volumes contain multidisciplinary coastal
zone resource information arranged in ten chapters under the general title ‘Coasts and Seas of the UK’. These volumes form
part of a series of paper and electronic publications of coastal information being produced by JNCC's Coastal Directories
Project and are designed to meet the needs of planners and all others involved in decision-making and management of the coast. 相似文献
180.
The role of human actions in evolution and management of foredunes in The Netherlands and New Jersey, USA 总被引:1,自引:0,他引:1
The rationale and methods of construction of foredunes in The Netherlands and New Jersey, USA are identified and used to explain
their genesis, locations, mobility, internal and external characteristics and temporal scales of evolution. Dunes are then
ranked according to the degree they are modified by human processes. The lower level of protection required of foredunes in
New Jersey and the greater amount of modification by municipal managers and shorefront residents results in smaller dunes
and greater variety of sizes, shapes, methods of construction and alterations. As a result, humans are considered intrinsic
agents in evolution of dune landforms and landscapes. Higher, wider, better vegetated foredunes occur in The Netherlands due
to greater frequency of onshore winds and greater emphasis on sea defence at the national level. Natural processes play a
greater role in the evolution of landforms. Human actions are considered extrinsic at this scale but intrinsic at the scale
of landscapes. The change in foredunes from natural features to artifacts reveals the significance of humans in the modification
of coastal landforms and reflects the changing perception of the role of these landforms in the coastal landscape. 相似文献