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411.
Inferring Threat from Scientific Collections 总被引:3,自引:1,他引:3
Exact formulas for the probability of extinction or change in the conservation status of species are described for data based on frequency of sighting. These formulas generalize an expression previously described for the probability of extinction from (binary) sighting data. The formulas will be used in contexts where sightings are recorded as frequencies, such as when observations are aggregated in time. We argue that computing the probability of extinction or change in conservation status will be most useful for setting conservation priorities and in screening large data sets contained in museum and herbarium collections and in biological resource inventories. 相似文献
412.
Manganese oxide coatings on sand particles within filtration beds from a water treatment plant in Grampian, Scotland were
examined to determine their control on metal mobility. This study first sought to characterise the oxides, notably their mineralogy
and metal content, to provide a foundation for studies on the adsorption of dissolved metals from the treated water by the
oxides. The oxides were examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and analysed by flame
atomic absorption spectrophotometry (AAS). These techniques showed the oxide coatings were amorphous but uniformly distributed
over each sand grain. The oxides were selectively removed from the sand grains prior to analysis by AAS using a hydroxylamine
hydrochloride selective leaching method. The compositional range of the extracts was 100–150 mg L−1 Mn; 30–55 mg L−1 Fe; 17–56 mg L−1 Ca; 4.6–7.0 mg L−1 Ni; 4.6–6.8 mg L−1 Zn and 1.3–5.7 mg L−1 Mg. When these results are expressed as mg of metal per mg of Mn, the metal content of the oxides is remarkably uniform:
0.25–0.37 mg Fe; 0.14–0.35 mg Ca; 0.035–0.042 mg Ni; 0.035–0.040 mg Zn; 0.01–0.04 mg Mg. The greatest metal concentrations
were consistently found in the upper 3 cm of the filtration bed, and these decrease with increasing depth. After the beds
are cleaned a more uniform distribution of metals occurs throughout the bed. The metals taken up by the manganese coating
are retained over a wide pH range with the exception of Ca and Mg which desorb to a significant extent. The percentage of
calcium and magnesium lost from the coating ranges from 30–94%, the amount being dependent on the final pH of the solution.
The presence of manganese oxide in the filtration beds appears to be advantageous in terms of removal of transition metals
from the treated water. 相似文献
413.
Summary Seasonal changes in sex ratios during a 4-year study of red-necked phalaropes and a 3-year study of Wilson's phalaropes showed that females preceded males to breeding and/or courtship areas. The degree to which females preceded males may have been constrained by harsh weather, as the arrival of red-necked phalaropes was synchronous in 1983, when spring was unusually late. Neither sex defended territories; females competed vigorously for direct access to males. These findings show that selection for sexually asynchronous arrival need not act through territoriality. We interpret early female arrival as an adaptation for obtaining mates and coclude that sexual selection may be an important determinant of arrival times in mate defense social systems. 相似文献
414.
Arthur Jeffrey L. Hachey Mark Sahr Kevin Huso Manuela Kiester A. R. 《Environmental and Ecological Statistics》1997,4(2):153-165
The problem of selecting nature reserves has received increased attention in the literature during the past decade, and a variety of approaches have been promoted for selecting those sites to include in a reserve network. One set of techniques employs heuristic algorithms and thus provides possibly sub-optimal solutions. Another set of models and accompanying algorithms uses an integer programming formulation of the problem, resulting in an optimization problem known as the Maximal Covering Problem, or MCP. Solution of the MCP provides an optimal solution to the reserve site selection problem, and while various algorithms can be employed for solving the MCP they all suffer from the disadvantage of providing a single optimal solution dictating the selection of areas for conservation. In order to provide complete information to decision makers, the determination of all alternate optimal solutions is necessary. This paper explores two procedures for finding all such solutions. We describe the formulation and motivation of each method. A computational analysis on a data set describing native terrestrial vertebrates in the state of Oregon illustrates the effectiveness of each approach. 相似文献
415.
Detailed empirical models predicting both species occurrence and fitness across a landscape are necessary to understand processes related to population persistence. Failure to consider both occurrence and fitness may result in incorrect assessments of habitat importance leading to inappropriate management strategies. We took a two-stage approach to identifying critical nesting and brood-rearing habitat for the endangered Greater Sage-Grouse (Centrocercus urophasianus) in Alberta at a landscape scale. First, we used logistic regression to develop spatial models predicting the relative probability of use (occurrence) for Sage-Grouse nests and broods. Secondly, we used Cox proportional hazards survival models to identify the most risky habitats across the landscape. We combined these two approaches to identify Sage-Grouse habitats that pose minimal risk of failure (source habitats) and attractive sink habitats that pose increased risk (ecological traps). Our models showed that Sage-Grouse select for heterogeneous patches of moderate sagebrush cover (quadratic relationship) and avoid anthropogenic edge habitat for nesting. Nests were more successful in heterogeneous habitats, but nest success was independent of anthropogenic features. Similarly, broods selected heterogeneous high-productivity habitats with sagebrush while avoiding human developments, cultivated cropland, and high densities of oil wells. Chick mortalities tended to occur in proximity to oil and gas developments and along riparian habitats. For nests and broods, respectively, approximately 10% and 5% of the study area was considered source habitat, whereas 19% and 15% of habitat was attractive sink habitat. Limited source habitats appear to be the main reason for poor nest success (39%) and low chick survival (12%). Our habitat models identify areas of protection priority and areas that require immediate management attention to enhance recruitment to secure the viability of this population. This novel approach to habitat-based population viability modeling has merit for many species of concern. 相似文献
416.
Eldridge S. Adams Lynn Atkinson Mark S. Bulmer 《Behavioral ecology and sociobiology》2007,61(8):1195-1201
Loss of aggression between social groups can have far-reaching effects on the structure of societies and populations. We tested
whether variation in the genetic structure of colonies of the termite Nasutitermes corniger affects the probability of aggression toward non-nestmates and the ability of unrelated colonies to fuse. We determined the
genotypes of workers and soldiers from 120 colonies at seven polymorphic microsatellite loci. Twenty-seven colonies contained
offspring of multiple founding queens or kings, yielding an average within-colony relatedness of 0.33. Genotypes in the remaining
93 colonies were consistent with reproduction by a single queen and king or their progeny, with an average within-colony relatedness
of 0.51. In standardized assays, the probability of aggression between workers and soldiers from different colonies was an
increasing function of within-colony relatedness. The probability of aggression was not affected significantly by the degree
of relatedness between colonies, which was near zero in all cases, or by whether the colonies were neighbors. To test whether
these assays of aggression predict the potential for colony fusion in the field, we transplanted selected nests to new locations.
Workers and soldiers from colonies that were mutually tolerant in laboratory assays joined their nests without fighting, but
workers and soldiers that were mutually aggressive in the assays initiated massive battles. These results suggest that the
presence of multiple unrelated queens or kings promotes recognition errors, which can lead to the formation of more complex
colony structures. 相似文献
417.
Mark E. Hauber 《Behavioral ecology and sociobiology》2002,51(6):503-509
What is the cost of parental care in birds? Previous studies using observational and experimental techniques on nest building and clutch sizes in a small migrant flycatcher, the Eastern Phoebe (Sayornis phoebe), led to contradictory results that did not show a consistent cost of current reproductive effort on residual reproductive output. The data presented here indicate that different elements of parental behaviors are indeed costly because they reduce various aspects of phoebes' subsequent reproductive performance. Experimental removal of old nesting structures at previously used breeding sites reduced but did not eliminate the chance of phoebes' settlement in the subsequent year. Comparing sites at which phoebes did and did not build new nests showed that nest builders completed their first clutches later, had lower probabilities of second breeding attempts, and more often lost their nesting attempt due to fallen nest structures than nest reusers. There was, however, no significant effect of nest building on the clutch sizes and rates of cowbird parasitism of first nesting attempts. Overall, sites with newly built nests had lower seasonal reproductive effort than sites with reused nests. I also examined phoebes' relative residual reproductive output in a separate breeding season when nest building was not experimentally manipulated. When controlled for confounding variables this analysis indicated that in those phoebes that did breed for a second time, the relative decrease of the sizes of first to presumed second clutches was greater at sites where first breeding attempts consisted of more total nestlings. These data are consistent with the hypothesis that parental care is costly in Eastern Phoebes and support predictions of trade-offs between the nest building, brood care, and residual egg-investment components of reproduction. 相似文献
418.
Directing Research to Reduce the Impacts of Nonindigenous Species 总被引:19,自引:0,他引:19
419.
Algal assemblages can be highly responsive to environmental changes in recovering acidified lakes. We compared epilithic algal assemblages in boreal lakes during chemical recovery from atmospheric (Killarney Park, Ontario) and experimental (Lake 302S, Experimental Lakes Area, Ontario) acidification to assess the impact of spatial and temporal scale of severe acidification on taxonomic resilience (i.e. recovery rate). Resilience was measured as the distance traveled by lakes in ordination space during pH recovery based on canonical correspondence analysis. Resilience was relatively negligible in the Killarney lakes, suggesting that eight years of experimental acidification in Lake 302S had less impact on biological recovery than did decades of regional acidification. Increases in dissolved organic carbon, dissolved inorganic carbon, and calcium best explained temporal variance of epilithic species abundances in the recovering acidified lakes. In Lake 302S, contrasting trajectories of taxonomic resilience and resistance, i.e. displacement from reference conditions following a perturbation, indicated that ecological factors affecting epilithon differed at corresponding pH levels during recovery and acidification. Our findings reveal that modeling of ecosystem recovery from severe acidification must account for the spatial and temporal scale of the perturbation, and biological delay responses that result in differences between recovery and acidification trajectories. 相似文献
420.
Erisman JW Vermeulen A Hensen A Flechard C Dämmgen U Fowler D Sutton M Grünhage L Tuovinen JP 《Environmental pollution (Barking, Essex : 1987)》2005,133(3):403-413
Monitoring and modelling of deposition of air pollutants is essential to develop and evaluate policies to abate the effects related to air pollution and to determine the losses of pollutants from the atmosphere. Techniques for monitoring wet deposition fluxes are widely applied. A recent intercomparison experiment, however, showed that the uncertainty in wet deposition is relatively high, up to 40%, apart from the fact that most samplers are biased because of a dry deposition contribution. Wet deposition amounts to about 80% of the total deposition in Europe with a range of 10-90% and uncertainty should therefore be decreased. During recent years the monitoring of dry deposition has become possible. Three sites have been operational for 5 years. The data are useful for model development, but also for model evaluation and monitoring of progress in policy. Data show a decline in SO(2) dry deposition, whereas nitrogen deposition remained constant. Furthermore, surface affinities for pollutants changed leading to changes in deposition. Deposition models have been further developed and tested with dry deposition measurements and total deposition measurements on forests as derived from throughfall data. The comparison is reasonable given the measurement uncertainties. Progress in ozone surface exchange modelling and monitoring shows that stomatal uptake can be quantified with reasonable accuracy, but external surface uptake yields highest uncertainty. 相似文献