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161.
162.
Jelle S. van Zweden Christoph Grüter Sam M. Jones Francis L.W. Ratnieks 《Behavioral ecology and sociobiology》2011,65(6):1277-1282
Social insects need to defend their nest against robbery, parasitism and predation. The stingless bee Tetragonisca angustula is unique in that it has guards that hover near the nest entrance in addition to guards that stand at the entrance. We tested
both the general hypothesis that hovering guards increase the effectiveness with which flying intruders are detected and the
specific hypothesis that hovering guards improve the detection of workers of the obligate robber bee, Lestrimellita limao. In an intraspecific study comparing colonies, we found a strong positive relationship between the number of hovering guards
and the distance at which a dummy robber bee or L. limao worker, experimentally moved towards the nest entrance, was detected. These results were mirrored in an interspecific study
showing that four species of stingless bees with similar population colonies but which lacked hovering guards, detected L. limao only at the nest entrance, in contrast to T. angustula. In addition, we found that a greater number of attacks by guards occurred when dummies were impregnated with citral, a major
component of L. limao mandibular gland odour. Our results support the hypothesis that T. angustula hovering guards increase the detection perimeter for flying intruders, especially L. limao. 相似文献
163.
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
164.
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
165.
166.
Lin C Solera Garcia MA Timmis R Jones KC 《Journal of environmental monitoring : JEM》2011,13(3):753-761
A new type of directional passive air sampler (DPAS) is described for collecting particulate matter (PM) in ambient air. The prototype sampler has a non-rotating circular sampling tray that is divided into covered angular channels, whose ends are open to winds from sectors covering the surrounding 360°. Wind-blown PM from different directions enters relevant wind-facing channels, and is retained there in collecting pools containing various sampling media. Information on source direction and type can be obtained by examining the distribution of PM between channels. Wind tunnel tests show that external wind velocities are at least halved over an extended area of the collecting pools, encouraging PM to settle from the air stream. Internal and external wind velocities are well-correlated over an external velocity range of 2.0-10.0 m s?1, which suggests it may be possible to relate collected amounts of PM simply to ambient concentrations and wind velocities. Measurements of internal wind velocities in different channels show that velocities decrease from the upwind channel round to the downwind channel, so that the sampler effectively resolves wind directions. Computational fluid dynamics (CFD) analyses were performed on a computer-generated model of the sampler for a range of external wind velocities; the results of these analyses were consistent with those from the wind tunnel. Further wind tunnel tests were undertaken using different artificial particulates in order to assess the collection performance of the sampler in practice. These tests confirmed that the sampler can resolve the directions of sources, by collecting particulates preferentially in source-facing channels. 相似文献
167.
Hazel A. Jackson Lawrence Percival-Alwyn Camilla Ryan Mohammed F. Albeshr Luca Venturi Hernán E. Morales Thomas C. Mathers Jonathan Cocker Samuel A. Speak Gonzalo G. Accinelli Tom Barker Darren Heavens Faye Willman Deborah Dawson Lauren Ward Vikash Tatayah Nicholas Zuël Richard Young Lianne Concannon Harriet Whitford Bernardo Clavijo Nancy Bunbury Kevin M. Tyler Kevin Ruhomaun Molly K. Grace Michael W. Bruford Carl G. Jones Simon Tollington Diana J. Bell Jim J. Groombridge Matt Clark Cock Van Oosterhout 《Conservation biology》2022,36(4):e13918
The pink pigeon (Nesoenas mayeri) is an endemic species of Mauritius that has made a remarkable recovery after a severe population bottleneck in the 1970s to early 1990s. Prior to this bottleneck, an ex situ population was established from which captive-bred individuals were released into free-living subpopulations to increase population size and genetic variation. This conservation rescue led to rapid population recovery to 400–480 individuals, and the species was twice downlisted on the International Union for the Conservation of Nature (IUCN) Red List. We analyzed the impacts of the bottleneck and genetic rescue on neutral genetic variation during and after population recovery (1993–2008) with restriction site-associated sequencing, microsatellite analyses, and quantitative genetic analysis of studbook data of 1112 birds from zoos in Europe and the United States. We used computer simulations to study the predicted changes in genetic variation and population viability from the past into the future. Genetic variation declined rapidly, despite the population rebound, and the effective population size was approximately an order of magnitude smaller than census size. The species carried a high genetic load of circa 15 lethal equivalents for longevity. Our computer simulations predicted continued inbreeding will likely result in increased expression of deleterious mutations (i.e., a high realized load) and severe inbreeding depression. Without continued conservation actions, it is likely that the pink pigeon will go extinct in the wild within 100 years. Conservation rescue of the pink pigeon has been instrumental in the recovery of the free-living population. However, further genetic rescue with captive-bred birds from zoos is required to recover lost variation, reduce expression of harmful deleterious variation, and prevent extinction. The use of genomics and modeling data can inform IUCN assessments of the viability and extinction risk of species, and it helps in assessments of the conservation dependency of populations. 相似文献
168.
Monica?R.?LaraEmail author David?L.?Jones Zhongxing?Chen John?T.?Lamkin Cynthia?M.?Jones 《Marine Biology》2008,153(3):235-248
Juvenile gray snapper, Lutjanus griseus, are believed to use bays and estuaries in southern Florida as nurseries before moving out to the adjoining reef tract as
adults. Using high-resolution sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS), the elemental chemistry
of the otoliths of juveniles from five nursery regions was resolved by establishing elemental “signatures” for each region.
In this study we simultaneously analyzed 32 elements including a suite of rare earth elements. A stepwise variable selection
procedure retained a subset of eight elements that contributed substantially to separating otolith samples, including two
rare earth elements; this is one of the first studies in which rare earth elements in otoliths have contributed to separation
of fish stocks. The classification success rate in assigning fishes to the correct region of origin was 82%. Resolution of
sites less than 10 km apart suggested high site fidelity in juvenile gray snapper and little mixing of water masses between
sites. The juvenile nursery signatures will be used to determine the relative contribution of different nurseries to the adult
population on an adjoining reef tract. 相似文献
169.
Brigitte M. Manship Anthony J. Walker Lucy A. Jones Angela J. Davies 《Marine Biology》2008,153(3):473-482
Juveniles of Paragnathia formica Hesse (Isopoda; Gnathiidae) are haematophagous ectoparasites, feeding on fish blood which supplies the nutrients for their
development through growth and moulting, and the subsequent survival and reproduction of the free-living adults. Little is
known of the mechanisms of digestion in juvenile gnathiids, and biochemical studies on the digestive tract of these interesting
estuarine isopods have not been undertaken previously. Here, functionally active cathepsin-like cysteine proteinases are identified
in the digestive system of juvenile praniza (fed) and zuphea (unfed) forms. The physiological pH of the digestive tract and
the optimum proteolytic activities detected in praniza 3 homogenates using the cathepsin B/L, cathepsin B, and cathepsin H
fluorogenic substrates, N-Carbobenzoxy-Phe-Arg-4-methoxy-2-naphthylamine (Z-phe-arg-MNA), N-Carbobenzoxy-Arg-Arg-4-methoxy-2-naphthylamine (Z-arg-arg-MNA) and Arg-4-methoxy-2-naphthylamine (H-arg-MNA), respectively, are in the acidic range (pH 5.8–6.7). Inhibition profiles against Z-phe-arg-MNA and Z-arg-arg-MNA using the cathepsin B inactivator urea, and cysteine proteinase inhibitors, support the presence of cathepsin
L- and B-like enzymes. These proteolytic activities are 10–50 times higher in homogenates of praniza 3 compared with zuphea
3 forms. Histochemistry of praniza 3 sections reveals that the predominant enzyme activity towards Z-phe-arg-MNA is limited to the digestive glands during early and mid stages of digestion; later, this activity appears in
the lining of the anterior hindgut. Moreover, activity towards Z-arg-arg-MNA is generally restricted to the digestive glands, and only occasionally present in the anterior hindgut. In conclusion,
the digestive glands are the main site of cathepsin-like cysteine proteinase activities in P. formica juveniles; these enzymes appear to be important to the digestion of host fish blood enabling development through to the free-living
adult. 相似文献
170.
Species richness and evenness are components of biological diversity that may or may not be correlated with one another and with patterns of species abundance. We compared these attributes among flowering plants, grasshoppers, butterflies, lizards, summer birds, winter birds, and rodents across 48 plots in the grasslands and mesquite-oak savannas of southeastern Arizona. Species richness and evenness were uncorrelated or weakly negatively correlated for each taxonomic group, supporting the conclusion that richness alone is an incomplete measure of diversity. In each case, richness was positively correlated with one or more measures of abundance. By contrast, evenness usually was negatively correlated with the abundance variables, reflecting the fact that plots with high evenness generally were those where all species present were about equally uncommon. Therefore richness, but not evenness, usually was a positive predictor of places of conservation value, if these are defined as places where species of interest are especially abundant. Species diversity was more positively correlated with evenness than with richness among grasshoppers and flowering plants, in contrast to the other taxonomic groups, and the positive correlations between richness and abundance were comparatively weak for grasshoppers and plants as well. Both of these differences can be attributed to the fact that assemblages of plants and grasshoppers were numerically dominated by small subsets of common species (grasses and certain spur-throated grasshoppers) whose abundances differed greatly among plots in ways unrelated to species richness of the groups as a whole. 相似文献