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761.
Multiple techniques confirm elevational differences in insect size that may influence spider sociality 总被引:1,自引:0,他引:1
Social and subsocial spiders of the genus Anelosimus exhibit an altitudinal pattern in their geographic distribution at tropical latitudes in the Americas. Social species, which capture prey cooperatively, occur primarily in the lowland rain forest and are absent from higher elevations, whereas subsocial species are common at higher elevations but absent from the lowland rain forest. Previous studies have suggested that differences in the size of potential insect prey along altitudinal gradients may explain this pattern as insects were found to be, on average, larger in lowland rain forests than at higher elevations. These studies, however, may have under-sampled the insect size composition of each habitat because only one sampling technique was used. Using a number of collection methods we sampled the insect size composition in the environments of social and subsocial spiders in this genus. We found that the average insect size in lowland rain forest habitats was indeed larger than at high-elevation cloud forests in eastern Ecuador. We also found that, even though the various techniques differed in the size of the insects they captured (visual searching and blacklighting yielding larger insects than beating, sweeping, or malaise trapping), they all caught, on average, larger insects in the lowlands. Overall, spider colonies in the lowlands caught larger prey than did spider colonies at higher elevations, paralleling differences in insect size distribution obtained by the various techniques in their respective environments. 相似文献
762.
Stephen?G.?PerzEmail author Carlos?Aramburú Jason?Bremner 《Environment, Development and Sustainability》2005,7(1):23-49
This paper discusses the linkages between population change, land use, and deforestation in the Amazon regions of Brazil, Bolivia, Colombia, Ecuador, Perú, and Venezuela. We begin with a brief discussion of theories of population–environment linkages, and then focus on the case of deforestation in the PanAmazon. The core of the paper reviews available data on deforestation, population growth, migration and land use in order to see how well land cover change reflects demographic and agricultural change. The data indicate that population dynamics and net migration exhibit to deforestation in some states of the basin but not others. We then discuss other explanatory factors for deforestation, and find a close correspondence between land use and deforestation, which suggests that land use is loosely tied to demographic dynamics and mediates the influence of population on deforestation. We also consider national political economic contexts of Amazon change in the six countries, and find contrasting contexts, which also helps to explain the limited demographic-deforestation correspondence. The paper closes by noting general conclusions based on the data, topics in need of further research and recent policy proposals.Readers should send their comments on this paper to:
BhaskarNath@aol.com within 3 months of publication of this issue 相似文献
763.
Effects of Management on Understory Diversity in the Forest Ecosystems of Northern Spain 总被引:2,自引:0,他引:2
Pine plantations are an alternative to marginal agriculture in many countries, and are often presented as an option that improves biodiversity. However, these plantations can have adverse environmental effects if improperly managed. To evaluate the effect of forest management practices on biodiversity, the diversity, species richness, dominance and frequency of understory woody plant species in different forests of the Basque Country (northern Spain) were compared. Plantations of exotic conifers (Pinus radiata [D.] Don) of different ages were compared with deciduous forests of Quercus robur L. and Fagus sylvatica L. The effects of different types and intensities of management were taken into account. The differences observed were mainly conditioned by the intensity of forestry management, although the response varied according to forest type and age. In unmanaged pine plantations, the diversity and species richness of the understory increased rapidly after planting (while dominance decreased), remained stable in the intermediate age range, and reached a maximum in plantations more than 25 years of age. Management practices resulted in decreased understory diversity and species richness, as well as greater dominance. This was more pronounced in younger than in older stands. Moderate management, however, favored a greater diversity of the understory in deciduous forests. The species composition of the plantations and deciduous forests were different, the latter having a wider range of characteristic species. Knowledge of how forestry practices influence biodiversity (in terms of diversity, richness, dominance, and species composition) may allow predictions to be made about the diversity achievable with different management systems. 相似文献
764.
Anna Korre Ji Quan Shi Claire Imrie Carlos Grattoni Sevket Durucan 《International Journal of Greenhouse Gas Control》2007,1(4):492-501
Laboratory studies and a number of field pilots have demonstrated that CO2 injection into coal seams has the potential to enhance coalbed methane (CBM) recovery with the added advantage that most of the injected CO2 can be stored permanently in coal. The concept of storing CO2 in geologic formations as a safe and effective greenhouse gas mitigation option requires public and regulatory acceptance. In this context it is important to develop a good understanding of the reservoir performance, uncertainties and the risks that are associated with geological storage. The paper presented refers to the sources of uncertainty involved in CO2 storage performance assessment in coalbed methane reservoirs and demonstrates their significance using extensive digital well log data representing the Manville coals in Alberta, Canada. The spatial variability of the reservoir properties was captured through geostatistical analysis, and sequential Gaussian simulations of these provided multiple realisations for the reservoir simulator inputs. A number of CO2 injection scenarios with variable matrix swelling coefficients were evaluated using a 2D reservoir model and spatially distributed realisations of total net thickness and permeability. 相似文献
765.
766.
Pollination is an ecological process that provides important services to humans. Pollination service in agroecosystems depends on several factors, including the land management systems used by farmers. Here we focused on the effects of insect pollinator diversity on coffee fruit production along a gradient of management systems in central Veracruz, Mexico. The gradient ranged from low environmental impact management systems (the native forest is not completely removed) to high environmental impact management systems (the native forest is completely removed). We hypothesized that pollinator diversity should be higher in low-impact systems. Then, if fruit production is positively related to pollinator diversity, plantations with low-impact management systems should display higher fruit production than plantations with high-impact management systems. We used observational and experimental data to test this hypothesis. Our results indicated that low-impact management systems have higher species richness and relative diversity (measured with the Shannon-Wiener diversity index) of pollinators than high-impact management systems. In all cases, fruit production was positively related with species richness and diversity of pollinators. Moreover, fruit production was higher in low-impact than in high-impact management systems. These results suggest that the diversity of insect pollinators can be influenced by the management system applied by farmers, and that such effects may have strong consequences on coffee fruit production. 相似文献
767.
Juan I. Canale Carlos A. Scanferla Federico L. Agnolin Fernando E. Novas 《Die Naturwissenschaften》2009,96(3):409-414
A nearly complete skeleton of the new abelisaurid Skorpiovenator bustingorryi is reported here. The holotype was found in Late Cenomanian–Early Turonian outcrops of NW Patagonia, Argentina. This new
taxon is deeply nested within a new clade of South American abelisaurids, named Brachyrostra. Within brachyrostrans, the skull
shortening and hyperossification of the skull roof appear to be correlated with a progressive enclosure of the orbit, a set
of features possibly related to shock-absorbing capabilities. Moreover, the development of horn-like structures and differential
cranial thickening appear to be convergently acquired within Abelisauridae. Based on the similarities between Skorpiovenator and carcharodontosaurid tooth morphology, we suggest that isolated teeth originally referred as post-Cenomanian Carcharodontosauridae
most probably belong to abelisaurids.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
768.
Carlos Cerdan Cristina Gazulla Marco Raugei Eva Martinez Pere Fullana-i-Palmer 《Journal of Cleaner Production》2009,17(18):1638-1643
Eco-design is a valuable approach in order to reduce the environmental impact associated with a product system, by introducing environmental considerations early on in its design. Different strategies are possible for the implementation of eco-design, depending on the intended goals as well as the characteristics of the products. The present work proposes a series of eco-design indicators and tests to what extent the application of these simple indicators provides a reliable indication of the reduction of environmental impact, as measured by commonly employed Life Cycle Impact Assessment (LCIA) indicators. The product chosen for the case study was a water source heat pump. Two of the newly-developed indicators were applied and compared to LCIA indicators, focussing on design for disassembly and for recycling. A good and robust correlation was found, providing support to the thesis that these simple eco-design indicators can be used as a proxy to quickly and effectively gauge the environmental improvements introduced in a product system at the design stage. 相似文献
769.
Firmat C Gomes Rodrigues H Hutterer R Rando JC Alcover JA Michaux J 《Die Naturwissenschaften》2011,98(1):33-37
Malpaisomys insularis is a mouse-like rodent endemic to the eastern Canary Islands. It became extinct during the fourteenth century. It was a remarkable
species living under hyperarid conditions. A dental microwear analysis was performed in order to determine its former diet.
The elevated number of fine scratches found in Malpaisomys molars suggests that it consumed a significant part of Poaceae, grass consumption leaving the most distinctive features on
dental wear facets. A graminivorous diet with a high amount of abrasive items is in agreement with the broad teeth of Malpaisomys, considered as adapted to grass consumption. However, in the absence of potential competitors over its native range, it is
likely that Malpaisomys also foraged on dicots to meet higher nutrient and energetic requirements. The ecology of Malpaisomys is discussed from these results in the context of the desertic climatic conditions of the eastern Canary Islands and with
a special concern on its small body size in contrast to other large-sized island murine species such as the giant rats of
the central Canary Islands. 相似文献
770.
de Paula FR Ferraz SF Gerhard P Vettorazzi CA Ferreira A 《Environmental management》2011,48(4):750-763
Riparian forests are important for the structure and functioning of stream ecosystems, providing structural components such
as large woody debris (LWD). Changes in these forests will cause modifications in the LWD input to streams, affecting their
structure. In order to assess the influence of riparian forests changes in LWD supply, 15 catchments (third and fourth order)
with riparian forests at different conservation levels were selected for sampling. In each catchment we quantified the abundance,
volume and diameter of LWD in stream channels; the number, area and volume of pools formed by LWD and basal area and tree
diameter of riparian forest. We found that riparian forests were at a secondary successional stage with predominantly young
trees (diameter at breast height <10 cm) in all studied streams. Results showed that basal area and diameter of riparian forest
differed between the stream groups (forested and non-forested), but tree density did not differ between groups. Differences
were also observed in LWD abundance, volume, frequency of LWD pools with subunits and area and volume of LWD pools. LWD diameter,
LWD that form pools diameter and frequency of LWD pools without subunits did not differ between stream groups. Regression
analyses showed that LWD abundance and volume, and frequency of LWD pools (with and without subunits) were positively related
with the proportion of riparian forest. LWD diameter was not correlated to riparian tree diameter. The frequency of LWD pools
was correlated to the abundance and volume of LWD, but characteristics of these pools (area and volume) were not correlated
to the diameter of LWD that formed the pools. These results show that alterations in riparian forest cause modifications in
the LWD abundance and volume in the stream channel, affecting mainly the structural complexity of these ecosystems (reduction
in the number and structural characteristics of LWD pools). Our results also demonstrate that riparian forest conservation
actions must consider not only its extension, but also successional stage to guarantee the quantity and quality of LWD necessary
to enable the structuring of stream channels. 相似文献