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761.
Adult sea lampreys (Petromyzon marinus) migrating upstream to spawn follow a pheromone released by instream larvae. The size (i.e. flow) of a tributary dilutes the concentration of this pheromone, such that the downstream propagation pattern of larval pheromone must be influenced by patterns in the relative sizes and numbers of confluent tributaries. We developed an individual-based model to explicitly test the resulting hypothesis that river network structure influences the migration decisions of adult lampreys following the larval pheromone, and in turn the distribution of larvae. First, we initialized the model using randomly generated river networks, and found a strong positive relationship between network diameter and larval aggregation. Larvae aggregated over time, and the degree and rate of this aggregation depended on network diameter. Second, we initialized the model using a river network based on the Muskegon River, Michigan, and compared model-generated larval distribution to available field survey data. We found a significant correlation between model-generated larval abundance and field-measured larval densities (r2 = 0.54; p < 0.0001). We also found an inverse relationship between subwatershed area and the degree to which path-dependent effects influenced larval abundance in that subwatershed. Our results overall suggest that larval distribution across a watershed results from a system of context-dependent interannual feedbacks shaped by network structure and the past migratory and spawning behavior of adults. 相似文献
762.
Traditional economic and policy analysis theory has emphasized the implementation of private or public property rights regimes in order to sustainably manage natural resources. More recent work has challenged this approach by examining the strengths and weakness of common property governance of such resources. This paper contributes to this literature by analyzing the acequia irrigation communities in northern New Mexico. Through statistical analysis, we find that the acequias’ ability to maintain collective-action as estimated by a critical performance function, crop production, is aided by water sharing agreements and access to groundwater, and that it is hampered by property rights fragmentation and urbanization. 相似文献
763.
764.
Most migratory species migrate at night, and the benefits associated with nocturnal migration have been well reviewed; however, less attention has been paid to the benefits associated with diurnal migration. There are two theories for diurnal migration: (1) diurnal migration allows for the use of thermals and therefore reduces energy loss, and (2) the fly-and-forage hypothesis, which suggests that diurnal migrants can search for prey and forage as they migrate. We investigated whether American crows (Corvus brachyrhynchos) engage in the fly-and-forage strategy of diurnal migration as they migrated north in the spring. We tracked eight radio-tagged crows as they migrated hundreds of kilometers in the spring to determine if they were diurnal migrants, whether they migrated with conspecifics, whether they stopped to forage, and if they did stop, whether they forage with conspecifics. All crows migrated during the day, and while on several occasions crows were seen migrating in close association with conspecifics, all crows were also observed migrating alone. On average, crows migrated approximately 300 km the day they left their wintering grounds, and over the course of this day, they stopped twice and foraged at these locations for 35 min. On all but one occasion, the stops made during migration were to forage with groups of conspecifics. While the fly-and-forage hypothesis for diurnal migration has primary been applied to raptors, many diurnal migrants forage socially, and the presence of foraging conspecifics and/or heterospecifics may be a significant benefit in locating food resources and ultimately migrating during the day. 相似文献
765.
Foragers can improve search efficiency, and ultimately fitness, by using social information: cues and signals produced by
other animals that indicate food location or quality. Social information use has been well studied in predator–prey systems,
but its functioning within a trophic level remains poorly understood. Eavesdropping, use of signals by unintended recipients,
is of particular interest because eavesdroppers may exert selective pressure on signaling systems. We provide the most complete
study to date of eavesdropping between two competing social insect species by determining the glandular source and composition
of a recruitment pheromone, and by examining reciprocal heterospecific responses to this signal. We tested eavesdropping between
Trigona hyalinata and Trigona spinipes, two stingless bee species that compete for floral resources, exhibit a clear dominance hierarchy and recruit nestmates to
high-quality food sources via pheromone trails. Gas chromatography–mass spectrometry of T. hyalinata recruitment pheromone revealed six carboxylic esters, the most common of which is octyl octanoate, the major component of
T. spinipes recruitment pheromone. We demonstrate heterospecific detection of recruitment pheromones, which can influence heterospecific
and conspecific scout orientation. Unexpectedly, the dominant T. hyalinata avoided T. spinipes pheromone in preference tests, while the subordinate T. spinipes showed neither attraction to nor avoidance of T. hyalinata pheromone. We suggest that stingless bees may seek to avoid conflict through their eavesdropping behavior, incorporating
expected costs associated with a choice into the decision-making process. 相似文献
766.
767.
James C. Coleman II Michael C. Miller Frank L. Mink 《Environmental monitoring and assessment》2011,172(1-4):663-687
The impact of urbanization on stream ecosystems is linked by land cover changes to the alteration of the natural hydrology and subsequent physical disruption of stream biota and habitat. Seasonal floods are part of the natural disturbance regime of many streams, but urbanization increases their frequency and magnitude. This study evaluated the impact of hydrologic disturbance on fish and aquatic macroinvertebrates in 81 (56 urban/25 reference) Ohio streams. Hydrologic variables included annual and monthly 24-h rainfall maxima and computed annual peak discharge, with computation supported by GIS-based drainage area delineation and land cover characterization. Ohio biological criteria for fish and macroinvertebrates measured during the late spring and summer were negatively impacted by annual peak discharge in urban streams as compared to reference streams. Results support the application of stormwater best management practices as part of stream restoration efforts to mitigate urbanization impacts to fish and macroinvertebrates. 相似文献
768.
Friedhelm Taube Michael Krawinkel Andreas Susenbeth Werner Theobald 《Environmental Sciences Europe》2011,23(1):1-1
In December 2009 the German Research Foundation published the booklet "Grüne Gentechnik" (Genetically modified crops) claiming to give a scientifically well balanced information about GMO's in agriculture. In this paper we analyse this approach resulting in a critical review regarding the intention of the booklet. We conclude that the evaluation of GMO's in agriculture primarily from a crop breeding perspective is lacking crucial positions in terms of ecology, socio-economy, agronomy, nutritional sciences and finally ethics in life science. 相似文献
769.
Polycyclic aromatic hydrocarbons in effluents from wastewater treatment plants and receiving streams in Tianjin, China 总被引:1,自引:0,他引:1
Weixiao Qi Huijuan Liu Jiuhui Qu Chengzhi Hu Huachun Lan Michael Berg Huimin Ren Wei Xu 《Environmental monitoring and assessment》2011,177(1-4):467-480
Surface water, suspended particulate matter, pore water, and sediment samples were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) in Yongding New River, South Drainage Canal and North Drainage Canal, which receive most of wastewater from industrial city of Tianjin. PAH concentrations in effluent samples of wastewater treatment plants (WTP) discharging into the South Drainage Canal and North Drainage Canal were quantified for the first time. The results showed that the discharge of the WTPs recently only contributed to the PAH contamination in the canals near the outlets of the WTPs. PAH levels in sediments of the streams were greatly higher than those in soils by riverbank probably due to receiving large amounts of untreated wastewater. Unusually high benz[a] anthracene concentration strongly influenced the seasonal and spatial variation of total PAH concentrations in South Drainage Canal. Paired samples t test of ??Nap, Fl, Phe, Fluo and ??Nap, Phe, Fluo, Chry concentrations, which were dominant components in the air samples from non-heating and heating season, respectively, in the suspended particulate matters from the streams showed that PAH source from air deposition was more important for Yongding New River than that for South Drainage Canal and North Drainage Canal. Source apportionment based on PAH profiles indicated that coal combustion was the major PAH contamination source, and coke oven sources and wood combustion also contributed to the PAH contamination of the streams. This was further indicated by organic petrography analysis. 相似文献
770.
Cena LG Keren N Li W Carriquiry AL Pawlovich MD Freeman SA 《Journal of Safety Research》2011,42(4):241-252