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571.
PROBLEM: Work on aerial lift platforms exposes workers to fall hazards. The objective of this study was to identify the most common injury scenarios and determine current research gaps for addressing fall incidents associated with aerial lifts. METHODS: Three databases were searched: Census of Fatal Occupational Injuries (CFOI), NIOSH Fatality Assessment and Control Evaluation (FACE) reports, and OSHA Incident Investigation Records. RESULTS: The majority of falls/collapses/tipovers were within the height-category of 10-29 feet. Tipovers comprised 44-46% of boom-lift falls and 56-59% of scissor-lift falls. Constructing and repairing activities were most commonly associated with fall/collapse/tipover incidents. DISCUSSION: CFOI and OSHA/FACE show convergent data, suggesting similar scenarios for aerial lift tipovers. IMPACT ON INDUSTRY: The analysis provides the aerial lift industry information to prioritize their efforts on aerial lift design. 相似文献
572.
Dugatkin LA 《Die Naturwissenschaften》2007,94(8):651-656
Using female mate choice copying as a rudimentary form of cultural transmission, this study provides evidence that social
environment during development has a significant effect on the tendency to use culturally acquired information. Groups of
newborn guppies (Poecilia reticulata) were raised for 35 days in 1 of 5 “developmental environments”. Groups of 15 newborns were raised in pools with no adults
(treatment 1), both adult male and female guppies (treatments 2 and 3), only adult females (treatment 4) or only adult males
(treatment 5). Mature females raised in treatments 1 and 2, but not treatments 3, 4, and 5, copied the mate choice of others.
Treatments 1 and 2 correspond to social structures that guppies experience during their development in the wild. Newborn guppies
swim together in shoals (analogous to treatment 1). As they mature, juveniles join schools of adult males and females (analogous
to treatments 2). At no time during the normal developmental process are juveniles found with males, but only unreceptive
females (as was the case for long periods in treatment 3) or in the presence of adults of only one sex (analogous to treatments
4 and 5). As such, normal developmental environments prime guppies for cultural transmission, while unnatural environments
fail to do so. 相似文献
573.
From 1935 to 2000, the net open water area of Inle Lake in Central Shan State, Myanmar decreased from 69.10 to 46.69 km2, a loss of 32.4% during this 65-year period. Local beliefs are that losses in lake area have been even greater within the
last 100–200 years. Various activities, including timber removal, shifting agriculture in the uplands by various ethnic groups,
and unsustainable cultivation practices on the low- and mid-level hillslopes around the lake, have been blamed for both historical
and ongoing sedimentation. We take issue with attributing loss of lake area to these activities, and propose instead that
ongoing “in-lake” and “near-lake” agricultural practices are the main sources of contemporary sediment and loss of open water
area. About 93% (i.e., 20.84 km2) of the recent loss in open water area of the lake is due to the development of floating garden agriculture, largely along
the west side of the lake. Direct environmental impacts associated with this practice and with other agriculture activities
within the wetlands and margins of the lake include sedimentation, eutrophication, and pollution. Whilst the sustainability
of hillslope agriculture and past forestry practices can indeed be questioned, a more urgent need is to address these "in-lake"
and "near-lake" practices. 相似文献
574.
Caterpillars have many natural enemies and, therefore, have evolved a diversity of antipredator strategies. Most research
focuses on those strategies (crypsis, countershading, and warning coloration) targeting visually guided predators. In contrast,
defensive sounds, although documented for more than a century, have been poorly studied. We report on a novel form of sound
production—chirping—in caterpillars of the common European Great Peacock moth (Saturnia pyri). Chirps are broadband, with dominant peaks ranging between the sonic (3.7 kHz) and ultrasonic (55.1 kHz) and are generated
by a rapid succession of mandibular “tooth strikes.” Chirp trains are induced by simulated predator attacks and precede or
accompany the secretion of a defensive chemical from integumental bristles, supporting our hypothesis that these sounds function
in acoustic aposematism. We propose that these caterpillars generate multimodal warning signals (visual, chemical, and acoustic)
to target the dominant sensory modalities of different predators, including birds, bats, and invertebrates.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
575.
The aboveground net primary productivity (ANPP) of grass communities in grasslands and savannas is primarily determined by precipitation quantity. Recent research, motivated by predictions of changes in the distribution of rainfall events by global climate change models, indicates that ANPP may be affected by rainfall distribution as much as by annual totals. Grazing and community composition are also known to affect grassland ANPP. The manner in which interactions between rainfall distribution, grazing, and community composition affect the relationship between precipitation and ANPP represents a critical knowledge gap. The effects of community composition and grazing on aboveground growth responses to intraseasonal variation in water availability were investigated at seven grassland sites with a nonselective clipping experiment. The aboveground growth of the dominant C4 species at each site was measured at regular intervals for 2-3 growing seasons in the presence or absence of regular defoliation. In the absence of defoliation, there was a general lack of synchrony of intraseasonal growth among co-occurring species. Variation in growth rates was high and was only partially explained by variation in rainfall. Regular defoliation increased growth synchrony at all sites, but changes in growth responses to rainfall varied between sites. These results suggest that community composition will be important in determining ANPP-precipitation relationships under conditions of altered rainfall distribution. However this effect appears to be a result of species responding differently to soil water or other resources rather than to rainfall per se. Grazing may override the effects of community composition by reducing differences in growth patterns between species and has the potential to weaken precipitation controls on ANPP. 相似文献
576.
Geoffrey Caron-Lormier David A. Bohan Cathy Hawes Alan Raybould Alison J. Haughton Roger W. Humphry 《Ecological modelling》2009
Predicting ecosystem effects is of crucial importance in a world at threat from natural and human-mediated change. Here we propose an ecologically defensible representation of an ecosystem that facilitates predictive modelling. The representation has its roots in the early trophic and energetic theory of ecosystem dynamics and more recent functional ecology and network theory. Using the arable ecosystem of the UK as an example, we show that the representation allows simplification from the many interacting plant and invertebrate species, typically present in arable fields, to a more tractable number of trophic-functional types. Our compound hypothesis is that “trophic-functional types of plants and invertebrates can be used to explain the structure, diversity and dynamics of arable ecosystems”. The trophic-functional types act as containers for individuals, within an individual-based model, sharing similar trophic behaviour and traits of biomass transformation. Biomass, or energy, flows between the types and this allows the key ecological properties of individual abundance and body mass, at each trophic height, to be followed through simulations. Our preliminary simulation results suggest that the model shows great promise. The simulation output for simple ecosystems, populated with realistic parameter values, is consistent with current laboratory observations and provides exciting indications that it could reproduce field scale phenomena. The model also produces output that links the individual, population and community scales, and may be analysed and tested using community, network (food web) and population dynamic theory. We show that we can include management effects, as perturbations to parameter values, for modelling the effects of change and indicating management responses to change. This model will require robust analysis, testing and validation, and we discuss how we will achieve this in the future. 相似文献
577.
Andrew M. Reynolds Jennifer L. Swain Alan D. Smith Andrew P. Martin Juliet L. Osborne 《Behavioral ecology and sociobiology》2009,64(1):115-123
The availability of food resources changes over time and space, and foraging animals are constantly faced with choices about
how to respond when a resource becomes depleted. We hypothesise that flying insects like bees discover new food sources using
an optimal Lévy flight searching strategy and odour-mediated anemotaxis, as well as visual cues. To study these searching
patterns, foraging honeybees were trained to a scented feeder which was then removed. Two new unrewarding feeders, or ‘targets’,
were then positioned up- and downwind of the original location of the training feeder. The subsequent flight patterns of the
bees were recorded over several hundred metres using harmonic radar. We show that the flight patterns constitute an optimal
Lévy flight searching strategy for the location of the training feeder, a strategy that is also optimal for the location of
alternative food sources when patchily distributed. Scented targets that were positioned upwind of the original training feeder
were investigated most with the numbers of investigations declining with increasing distance from the original feeder. Scented
targets in downwind locations were rarely investigated and unscented targets were largely ignored, despite having the same
visual appearance as the rewarding training feeder. 相似文献
578.
Ecologists have long debated the relative importance of biotic interactions vs. abiotic forces on the population dynamics of both marine and terrestrial organisms. Investigation of stock size in Dungeness crab (Cancer magister) is a classic example of this debate. We first tested the hypothesis that adult population size was set by larval success. We found that during a five-year sampling period, adult crab population size from Oregon through central California, USA, as measured by the commercial catch, varied directly with the number of terminal-stage larvae (megalopae) returning to Coos Bay, Oregon, four years earlier; adult population size was largely determined (> 90% of the variation) by success during the larval stage. We then tested whether biotic interactions or abiotic forces caused the variation in larval success. Most of the variation (> 90%) in the number of returning megalopae is explained by the timing of the spring transition, a seasonal shift in atmospheric forcing that drives ocean currents along the west coast of the United States. Early spring transitions lead to larger numbers of returning Dungeness megalopae, while in four other crab taxa, species with very different life history characteristics, early-spring transitions lead to lower numbers of returning megalopae. During the past roughly 30 years, the size of the commercial catch of Dungeness crab is significantly and negatively correlated with the date of the spring transition throughout the California Current system. Long-term variation in the date of the spring transition may explain a major crash in the Dungeness crab fishery in central California, which began in the late 1950s. The data suggest that Dungeness crab population size is determined by variation in larval success and that a significant portion of this variation is due to the timing of the spring transition, a large-scale climatic forcer. 相似文献
579.
580.