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831.
Time-lapse videography of limpets mounted with light-emitting diodes was used to monitor the movements of a population of the non-homing Cellana grata on a vertical gully wall in Hong Kong. Animals were monitored for >7 days to examine spatial and temporal variation in their behaviour as the tides transited from a semi-diurnal to an almost diurnal pattern. Movement was synchronised with the tides, irrespective of the day–night cycles. Limpets rested low on the shore and were stimulated to move by the rising tide. Individuals moved up shore with the flooding tide, maintaining themselves in the awash zone, and then down shore on the ebbing tide, until they reached a resting height when the tide then fell beneath them, exhibiting ‘zonal shuttling’. A tight coupling of limpet position to tide height persisted through the changing tidal pattern, and almost all animals displayed the same organisation of activity over all tides. Initiation of activity and maximum height reached were probably controlled by the tides, but the cessation of activity may have been controlled by an internal clock. The pattern observed is consistent with the threat of attack from aquatic predators coupled with the need to minimise physical stresses while exposed. It is also consistent with the avoidance of grazing lower on the shore where interspecific competition may be more intense. Limpets showed two peaks of activity per tide, corresponding to when the rate of change of tide height was the greatest, except when tides became much reduced during the transit to a diurnal pattern. Movement was triphasic: an initial rapid phase, followed by a slower phase in the high shore and then a rapid phase before the limpets stopped moving. This structure is common in limpets and in this case is likely to be a consequence of animals maintaining themselves within the awash zone. Tide height appears to determine foraging activity, but with modifications in the behaviour in response to factors operating at more local temporal and spatial scales. 相似文献
832.
Lewis W. Oring J. Michael Reed Mark A. Colwell David B. Lank Stephen J. Maxson 《Behavioral ecology and sociobiology》2004,28(6):433-442
Summary We investigated factors affecting annual mating success (MS) and reproductive success (RS) of spotted sandpipers (Actitis macularia) from 13 years of a 17-year study at Little Pelican Island, Leech Lake, Minnesota. Analyses were restricted to ages 1–3. Mean annual female MS varied from 1.3 to 2.7 mates, and the MS pattern was indistinguishable from random. However, female MS increased with age and was affected by arrival date, territory size, and beach size. Female RS also increased with age, and number of mates and year effects were the most significant explanatory variables in each age. Older female RS was increased by priority on a territory and presence of a previous mate. Territory size and beach size varied with population density and did not predictably affect RS. The strong year affect on RS was associated with annual variation in sex ratio and predation. Males produce only one successful clutch per year, so MS greater than one is a result of nest loss and does not increase RS. Neither male MS nor RS changed with age. Male reproductive failure rate varied by year. Given that a male produced young, the degree of RS was affected by year, arrival date, priority on a territory, territory size, and beach size. In years with early-season predation, late arrivals had higher RS; territory and beach size effects varied by year. Neither the presence, nor degree, of female care was associated with male RS. Male RS was more subject to annual environmental variability than was female RS, probably because of relatively low annual potential RS among males.Offprint requests to: L.W. Oring at the current address 相似文献
833.
Status of Piping Plovers in the Great Plains of North America: A Demographic Simulation Model 总被引:1,自引:0,他引:1
A stochastic population growth model using empirical demographic data confirmed that the Piping Plover population of the Great Plains of North America is declining by more than 7% annually. Unchecked, this decline would result in extirpation in approximately 80 years. When recent adult (0.66) and immature (0.60) survival rates were held constant, a 31% increase—from 0.86 to 1.13 chicks fledged per pair—was needed to stabilize the population. Annual population increases of 1% and 2% required 1.16 and 1.19 chicks per pair, respectively. Such growth would result in the Great Plains population reaching the level—(2550 pairs)—needed for delisting from the U.S. Endangered Species Act protection in 53 and 30 years, respectively. One- and five-year delays in the initiation of 1% population growth caused 13 and 67 year delays respectively in reaching recovery. 相似文献
834.
Availability and Extraction of Forest Products in Managed and Primary Forest around a Dayak Village in West Kalimantan, Indonesia 总被引:1,自引:0,他引:1
We examined the density and abundance of marketable products in managed forest (rubber gardens, fruit gardens, and dry rice fallows) and in primary forest surrounding the Dayak village of Kembera, near Gunung Palung National Park, West Kalimantan, Indonesia. We calculated the proportion of trees that were marketable and useful for local consumption by counting and identifying trees in each managed forest type, and we documented extraction of products through interviews. Villagers harvested four marketable tree products: tengkawang seeds ( Shorea stenoptera ), durian fruits (various Durio spp.), rubber ( Hevea brasiliensis ), and timber, especially Bornean ironwood ( Eusideroxylon zwageri ). We inventoried trees at least 20 cm diameter at breast height (dbh) of marketed species from 0.4-ha plots in primary forest ( n = 8) and from 0.1-ha plots in each managed forest type ( n = 10–11). With the exception of timber, the density of trees producing a marketable product was significantly higher in the forest type managed for that product than the density of the marketed species, or of similar wild species, in primary forest. Total abundance (product of density and available area) of durian and tengkawang was greater in primary forest; however, villagers gathered these products only from managed forest. We infer from this choice a greater efficiency of harvesting from trees in dense stands near the village. Historically, this choice resulted in deliberate development of fruit gardens in preference or in addition to gathering from the more distant, primary forest. Because of low product density in primary forest, extractive forest reserves or buffer zones designed to encourage the production of fruits such as tengkawang or durian may not provide a sufficient incentive for the protection of primary forest around Kembera and other Dayak villages near Gunung Palung National Park. 相似文献
835.
Nest or roost temperature (T
roost) is thought to impact reproductive fitness in many endotherms but few studies have directly tested the hypothesis that naturally
occurring variability in nest or roost microclimate is large enough to affect reproductive success. We conducted a field experiment
to test whether roost selection by cavity-dwelling, reproductive female big brown bats (Eptesicus fuscus) is more strongly influenced by roost microclimate or a physical characteristic of roosts that facilitates social thermoregulation
(i.e., cavity volume). We quantified spatial variability in T
roost within different-sized, unoccupied cavities and also recorded T
roost in occupied vs unoccupied roost trees. We used equations relating energy use and ambient temperature for big brown bats to
calculate values of daily energy expenditure from T
roost data because energy is a currency that likely affects reproductive fitness. We found no difference between maximum and minimum
T
roost, spatial variability in T
roost, or predicted energy expenditure in more-preferred vs less-preferred roosts. However, there was a significant difference
between T
roost and predicted energy expenditure when we compared occupied vs unoccupied roosts. The presence of bats increased T
roost by as much as 7°C, and there was a significant positive correlation between the number of bats occupying a roost, maximum
daily T
roost, and energy savings. We calculate that, on average, a normothermic individual would save about 6.5 kJ/day (roughly 9% of
the daily energy budget) by roosting in an occupied cavity relative to roosting alone and that savings may increase to 40 kJ/day
(about 53% of the energy budget) for an individual roosting in a group of 45 bats. Our findings suggest that variability in
microclimate among potential roost or nest sites may be less important to some cavity-dwelling endotherms than has been suggested
in previous studies. Our results reinforce the importance of sociality and social thermoregulation to the roosting ecology
of forest-living bats and socially roosting or nesting endotherms in general. 相似文献
836.
The distribution and diet of juvenile (<750 mm) Patagonian toothfish are described from four annual trawl surveys (2003–2006)
around the island of South Georgia in the Atlantic sector of the Southern Ocean. Recruitment of toothfish varies inter-annually,
and a single large cohort dominated during the four years surveyed. Most juveniles were caught on the Shag Rocks shelf to
the NW of South Georgia, with fish subsequently dispersing to deeper water around both the South Georgia and Shag Rocks shelves.
Mean size of juvenile toothfish increased with depth of capture. Stomach contents analysis was conducted on 795 fish that
contained food remains and revealed that juvenile toothfish are essentially piscivorous, with the diet dominated by notothenid
fish. The yellow-finned notothen, Patagonotothen guntheri, was the dominant prey at Shag Rocks whilst at South Georgia, where P. guntheri is absent, the dominant prey were Antarctic krill and notothenid fish. The diet changed with size, with an increase in myctophid
fish and krill as toothfish grow and disperse. The size of prey also increased with fish size, with a greater range of prey
sizes consumed by larger fish. 相似文献
837.
Principal Biogeochemical Factors Affecting the Speciation And Transport of Mercury through the terrestrial environment 总被引:2,自引:0,他引:2
It is increasingly becoming known that mercury transport and speciation in the terrestrial environment play major roles in methyl-mercury bioaccumulation potential in surface water. This review discusses the principal biogeochemical reactions affecting the transport and speciation of mercury in the terrestrial watershed. The issues presented are mercury-ligand formation, mercury adsorption/desorption, and elemental mercury reduction and volatilization. In terrestrial environments, OH–, Cl– and S– ions have the largest influence on ligand formation. Under oxidized surface soil conditions Hg(OH)2, HgCl2, HgOH+, HgS, and Hg0 are the predominant inorganic mercury forms. In reduced environments, common mercury forms are HgSH+, HgOHSH, and HgClSH. Many of these mercury forms are further bound to organic and inorganic ligands. Mercury adsorption to mineral and organic surfaces is mainly dictated by two factors: pH and dissolved ions. An increase in Cl– concentration and a decrease in pH can, together or separately, decrease mercury adsorption. Clay and organic soils have the highest capability of adsorbing mercury. Important parameters that increase abiotic inorganic mercury reduction are availability of electron donors, low redox potential, and sunlight intensity. Primary factors that increase volatilization are soil permeability and temperature. A decrease in mercury adsorption and an increase in soil moisture will also increase volatilization. The effect of climate on biogeochemical reactions in the terrestrial watershed indicates mercury speciation and transport to receiving water will vary on a regional basis. 相似文献
838.
Mark R. Antell 《Environment international》1979,2(3):157-166
A model of rural smogs and urban plumes introduced into rural smog is developed. The single day variation of level of reactive species including ozone in rural smog in the eastern United States is simulated by mathematical modelling. Rural air masses are modelled as though they were outdoor smog chamber systems of low inital contaminant concentration to which small additional injections of contaminants, representing rural emissions, are made throughout the day. Rural smogs containing urban plumes are modelled as though they were outdoor inflatable smog chambers to which relatively large amounts of pollution material are added in the early minutes after sunrise and which are continuously diluted with material from chambers simulating rural smog. The urban plume model is specifically intended to simulate the photochemistry of parcels of air which sweep over relatively isolated cities in the eastern United States.The model runs suggest that the observed lack of urban plumes downwind of small cities is due to dilution. Additionally, the model suggests that the concentrations of both ozone and ozone precursors in rural smog have a significant effect on ozone production in urban plumes. 相似文献
839.
Alexandra Volokitina Mark Sofronov Tatiana Sofronova 《Mitigation and Adaptation Strategies for Global Change》2008,13(7):661-674
Problem of wildfires has not been resolved anywhere in the world. Mere increase of technical power does not lead to desirable
results. Forests of developed countries burn as actively as those in Africa or in Russia. The main reasons of wildfire problem
are as follows: (1) Constant wandering of dry seasons over the planet causing outbreaks of wildfires. (2) Unpredicted self-development
of ordinary wildfires into awful fire disasters. (3) Difficulties in delivery and use of heavy machines on hardly accessible
territories. (4) Absence of a perfect technique for economic evaluation of how effectively the wildfire control system works.
(5) Absence of the system of payments encouraging wildfire fighters. To solve the problem of wildfires in Russia it is necessary
to: (1) Create the Russian wildfire behaviour and fire effects prediction system on the basis of the developed classification
of vegetation fuels and methods of their mapping as well as maximum utilization of forest inventory information and Geographic
Information System (GIS). (2) Elaborate a technique of proper wildfire monitoring including estimation of vegetation damage.
(3) Improve daily rating of regional fire danger. (4) Improve fire-preventive arrangement of the territory covered by vegetation,
the main goal being creation of favourable conditions for active fire management. (5) Choose the main direction in elaboration
of fire-fighting means and methods taking into account their universality, simplicity, reliability, etc. (6) Elaborate an
improved technique for estimation of economic effectiveness of the wildfire control system. (7) Develop international cooperation
of scientists and professionals in fire management. 相似文献
840.
Eggshell colour does not predict measures of maternal investment in eggs of <Emphasis Type="Italic">Turdus</Emphasis> thrushes 总被引:1,自引:0,他引:1
Cassey P Ewen JG Blackburn TM Hauber ME Vorobyev M Marshall NJ 《Die Naturwissenschaften》2008,95(8):713-721
The striking diversity of avian eggshell colour has long fascinated biologists. Recently, it has been proposed that the blue-green colour of some eggs may function as a post-mating sexually selected signal of female phenotypic quality to their mates to induce higher allocation of paternal care. It has been suggested that maternally deposited yolk carotenoids may be the specific aspect of reproductive quality that the female is signalling via eggshell colour. We use the known properties of the thrush visual system (Turdus sp.) to calculate photon capture for the four single cone photoreceptors, and the principal member of the double cone class for eggs in clutches of two introduced European thrush species (Turdus merula and Turdus philomelos) in New Zealand. We show that differences in the avian-perceived colours of individual eggs are not consistently correlated with different measures of maternal investment in the egg. Given the growing extent of the knowledge between maternal quality, parental investment and eggshell pigmentation across avian taxa, we encourage the use of avian perceptual modelling for testing alternative non-signalling explanations for the structural and physiological basis of these relationships. 相似文献