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281.
The goal of the regional haze mitigation program in the United States is to attain "natural conditions" in national parks and wilderness areas by 2064. Results of research investigations on background concentrations of sea salt and biogenic organic matter, of episodic Saharan and Asian dust, and of carbon from natural fires were reviewed to provide a basis for making site-specific estimates of what the concentrations of atmospheric fine particulate matter components might be under natural conditions in the Southeastern United States. Based on this review, rough estimates were made of potential contributions of these aerosol components to natural background visibility. Natural organic particles were the dominant influence on the rate of visibility improvement required to reach natural conditions at an inland, mountainous location, and organic particles and sea salt were the dominant influences on the rate at a coastal location. African dust also had a large episodic effect, but the current regulatory approach is not designed to address episodic background variations. Insufficient data exist to quantify the contributions of wildfires with any detail, although global air pollution modeling provides insight, and their emissions can be locally dominant. Conservative regional refinements to the default natural background estimates do not greatly alter the region-wide rates of reduction of ambient particulate matter concentrations that will be needed to accomplish the first phase of the regional haze program. However, refinements at specific Class I areas may have considerable influence on defining the nature (magnitude and spatial and temporal distribution) of local emission reduction efforts there. 相似文献
282.
Huang V Sakata JT Rhen T Coomber P Simmonds S Crews D 《Die Naturwissenschaften》2008,95(12):1137-1142
Kratochvil et al. (Naturwissenschaften 95:209–215, 2008) reported recently that in the leopard gecko (Eublepharis macularius) of the family Eublepharidae with temperature-dependent sex determination (TSD), clutches in which eggs were incubated at
the same temperature produce only same-sex siblings. Interpreting this result in light of studies of sex steroid hormone involvement
in sex determination, they suggested that maternally derived yolk steroid hormones could constrain sex-determining mechanisms
in TSD reptiles. We have worked extensively with this species and have routinely incubated clutches at constant temperatures.
To test the consistency of high frequency same-sex clutches across different incubation temperatures, we examined our records
of clutches at the University of Texas at Austin from 1992 to 2001. We observed that clutches in which eggs were incubated
at the same incubation temperature produced mixed-sex clutches as well as same-sex clutches. Furthermore, cases in which eggs
within a clutch were separated and incubated at different temperatures produced the expected number of mixed-sex clutches.
These results suggest that maternal influences on sex determination are secondary relative to incubation temperature effects. 相似文献
283.
D. K. Brockman Patricia L. Whitten Alison F. Richard Benjamin Benander 《Behavioral ecology and sociobiology》2001,49(2-3):117-127
Previous research suggests that although reproduction and testicular function in wild sifaka (Propithecus verreauxi) are highly seasonal, birth season elevations in fecal testosterone (T) in transferring males indicate that social factors
may be as important as climatic factors in regulating reproductive function in sifaka. This paper examines the relationship
of male dispersal and social status to the patterning of birth season aggression and testicular function in P. verreauxi at Beza Mahafaly Special Reserve, Madagascar. Behavioral and hormonal data were collected from a total of 38 adult males,
15 residing in seven stable groups and 23 living in eight unstable groups, yielding 186 fecal samples and 493 focal animal
hours of observation. The results suggest that birth season elevations in fecal testosterone are the consequence of social
disruption resulting from male movements between groups and the particular responses of individual males to dispersal events.
Hormonal responses to dispersal events appear to precede behavioral responses and occasionally register reactions not concomitantly
evident in the behavioral response, and may be predictive of future events. Hormonal reactions occurred primarily in resident
alpha males, suggesting that they differ in their assessment of destabilizing influences, perhaps due to different reproductive
opportunities and/or investment. These findings are important for the new insights they provide into the role of androgens
in mediating male dispersal, life history, and reproductive strategies, and suggest that investigations of androgen-behavior
interactions in free-ranging populations can be a powerful new tool for assessing the contextual and motivational basis of
social behavior.
Received: 22 November 1999 / Revised: 27 April 2000 / Accepted: 15 October 2000 相似文献
284.
285.
Encarnación Rodriguez-Gonzalo 《环境化学》2008,27(1):131-133
来自野生动物和实验室的证据表明,一些化学物质可能对内分泌系统有干扰作用.内分泌干扰物(EDCs)包括农药、多氯联苯(PCBs)、二噁英、呋喃、烷基酚以及甾醇类雌激素(天然生成及人工合成).由于甾醇类雌激素对人体潜在的干扰性,人们对其特别关注. 相似文献
286.
Mirimin Luca Westgate Andrew Rogan Emer Rosel Patricia Read Andrew Coughlan Jamie Cross Tom 《Marine Biology》2009,156(5):821-834
The understanding of population structure and gene flow of marine pelagic species is paramount to monitoring, management and
conservation studies. Such studies are often hampered by the potentially high dispersal behavior of the species, the lack
of obvious geographical barriers in the marine environment and the scarce sample availability. Short-beaked common dolphins
(Delphinus delphis) are widespread in coastal and open-ocean habitats of the North Atlantic Ocean, nevertheless population structure and migratory
patterns are poorly understood. Furthermore, concern has been raised about the status of the species because large numbers
of dolphins have been taken incidentally in several fisheries throughout the North Atlantic in the past decades. In the present
study, a large number of individual samples were obtained from seasonal and spatial aggregations of common dolphins from western
(wNA) and eastern North Atlantic (eNA) regions, mostly using opportunistic sampling (i.e. from incidental entanglement in
fishing gear or beach-cast carcasses). Genetic variability was investigated using nuclear (14 microsatellite loci) and mitochondrial
(360 bp of the control region) genetic markers. Levels of genetic diversity were relatively high in all sampled areas and
no evidence of recent reduction of effective population size (i.e. bottleneck) was detected at the nuclear loci. Significant
population structure was detected between the two main regions (wNA and eNA) where it appeared to be more pronounced at mitochondrial
(F
ST = 0.018, P < 0.001) than nuclear markers (F
ST = 0.005, P < 0.05), indicating the presence of at least two genetically distinct populations of common dolphins in the North Atlantic
Ocean. In contrast, no significant genetic structure was detected between temporal aggregations of dolphins from within the
same region, suggesting possible seasonal movement patterns at a regional scale. The observed levels of genetic differentiation
between classes of markers are discussed here as a possible consequence of migratory patterns or recent population subdivision.
An erratum to this article can be found at 相似文献
287.
Tracey N. Johnson Patricia L. KennedyTim DelCurto Robert V. Taylor 《Agriculture, ecosystems & environment》2011,144(1):338-346
In 2006-2010, effects of four different cattle stocking rates (0, 14.4, 28.8, and 43.2 animal unit months) were compared, representing 0%, 20%, 32%, and 46% utilization of vegetation by domestic livestock, on vegetation structure (as indexed by visual obstruction), and songbird population and apparent nest density, community composition, and diversity in a Pacific Northwest bunchgrass prairie in northeastern Oregon, USA. Overall paddock-level visual obstruction decreased and structural heterogeneity increased with increasing stocking rates, and those effects carried over 1 year after grazing had ceased. Most species were able to locate nesting sites regardless of differences in visual obstruction, except western meadowlark and vesper sparrow, for which obstruction was lower in paddocks with higher stocking rates. Apparent nest density for grasshopper sparrows was negatively affected by higher stocking rates. Grazing effects on absolute songbird population density were restricted to negative effects of higher stocking rates on savannah sparrows, but this relationship was not observed until 1 year after grazing had ceased. Songbird community composition differed between control and heavily-grazed paddocks, driven by an increase in the proportion of horned larks and a decrease in the proportion of savannah sparrows in heavily-grazed paddocks from pre-treatment to post-treatment years. Bird diversity indices were unaffected by stocking rate. Negative effects of high stocking rates on densities of two species and the absence of any clear positive effect for the other three species suggest high stocking rates as applied in this experiment may not provide suitable habitat for all grassland songbirds. The absence of negative responses of density to low and moderate stocking rates suggests these grazing regimes generally provided suitable habitat for all species. 相似文献
288.
Introduction: The aims of this study were to provide further evidence of validity and reliability for the Driving Anger Expression Inventory (DAX) French adaptation (Villieux & Delhomme, 2008, Le Travail Humain, 71(4), 359-384) and to investigate the relationships between driving anger, how people express their anger while driving, and traffic violations among young drivers in France. Method: The French adaptations of the DAX, of the Driving Anger Scale (DAS), and of the Extended Violations Scale were administered to a sample of 314 drivers. Results: Confirmatory factor analysis of the French DAX items yielded a three factors solution with 11 items, which obtained better goodness-of-fit to the data. Cronbach α reliabilities for DAX factors ranged from .71 to .79. Aggressive forms of anger expression correlated positively with driving anger and traffic violations whereas the 'Adaptive/Constructive Expression' factor correlated negatively with these variables. Discussion: Globally, our results replicated earlier findings and showed that DAX factors are useful predictors of self reported violations and complement established measures like the DAS. Impact on Industry: Implications for driver education and interventions were examined. 相似文献
289.
290.