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1.
Changes in land-use practices have affected the integrity and quality of water resources worldwide. In Patagonia there is a strong concern about the ecological status of surface waters because these changes are rapidly occurring in the region. To test the hypothesis that greater intensity of land-use will have negative effects on water quality, stream habitat and biodiversity we assessed benthic macroinvertebrates, riparian/littoral invertebrates, fish and birds from the riparian corridor and environmental variables of 15 rivers (Patagonia) subjected to a gradient of land-use practices (non-managed native forest, managed native forest, pine plantations, pasture, urbanization). A total of 158 macroinvertebrate taxa, 105 riparian/littoral invertebrate taxa, 5 fish species, 34 bird species, and 15 aquatic plant species, were recorded considering all sites. Urban land-use produced the most significant changes in streams including physical features, conductivity, nutrients, habitat condition, riparian quality and invertebrate metrics. Pasture and managed native forest sites appeared in an intermediate situation. The highest values of fish and bird abundance and diversity were observed at disturbed sites; this might be explained by the opportunistic behavior displayed by these communities which let them take advantage of increased trophic resources in these environments. As expected, non-managed native forest sites showed the highest integrity of ecological conditions and also great biodiversity of benthic communities. Macroinvertebrate metrics that reflected good water quality were positively related to forest land cover and negatively related to urban and pasture land cover. However, by offering stream edge areas, pasture sites still supported rich communities of riparian/littoral invertebrates, increasing overall biodiversity. Macroinvertebrates were good indicators of land-use impact and water quality conditions and resulted useful tools to early alert of disturbances in streams. Fish and birds having a greater ability of dispersion and capacity to move quickly from disturbances would reflect changes at a higher scale.  相似文献
2.
Effects of golf courses on local biodiversity   总被引:4,自引:2,他引:2  
R. A.  A. C.   《Landscape and urban planning》2005,71(2-4):137-146
There are approximately 2600 golf courses in the UK, occupying 0.7% of the total land cover. However, it is unknown whether these represent a significant resource, in terms of biodiversity conservation, or if they are significantly less diverse than the surrounding habitats.The diversity of vegetation (tree and herbaceous species) and three indicator taxa (birds, ground beetles (Coleoptera, Carabidae) and bumblebees (Hymenoptera, Apidae)) was studied on nine golf courses and nine adjacent habitats (from which the golf course had been created) in Surrey, UK. Two main objectives were addressed: (1) to determine if golf courses support a higher diversity of organisms than the farmland they frequently replace; (2) to examine whether biodiversity increases with the age of the golf course.Birds and both insect taxa showed higher species richness and higher abundance on the golf course habitat than in nearby farmland. While there was no difference in the diversity of herbaceous plant species, courses supported a greater diversity of tree species. Furthermore, bird diversity showed a positive relation with tree diversity for each habitat type. It was found that introduced tree species were more abundant on the older golf courses, showing that attitudes to nature conservation on courses have changed over time. Although the courses studied differed in age by up to 90 years, the age of the course had no effect on diversity, abundance or species richness for any of the animal taxa sampled. We conclude that golf courses of any age can enhance the local biodiversity of an area by providing a greater variety of habitats than intensively managed agricultural areas.  相似文献
3.
Growth of urban centres world-wide has been so dramatic over the past 100–200 years that many natural habitats have been much altered around large cities. A threatened coastal plant community, Moonah Melaleuca lanceolata woodlands, has been largely destroyed and degraded over a long period by the growth of suburbs into the desirable coastal areas on the fringes of the two main cities of Vic., Australia (Melbourne and Geelong). Here, we describe the avifaunas of 19 remnants of coastal Moonah woodland. The largest remnant is about 50 ha and this was used as a site for positioning ‘virtual’ remnants against which we could compare the avifaunas of the more common size-range of real remnants (≤10 ha). Although remnant habitat structure differed consistently between virtual and real remnants, these differences were not sufficient to alter the native avifaunas in constitution or bird densities. However, species richness was higher in 10 ha and in 2 ha remnants than in 1 ha remnants. Of seven landscape-context variables, only one influenced the avifauna: species richness declined as the degree of urbanization increased (measured by roof-counts). Exotic bird species have not colonized the remnants to a great degree (four species [of 38 in total], 8% of total records).  相似文献
4.
Assessment and management of risk to wildlife from cadmium   总被引:3,自引:0,他引:3  
Cadmium, a nonessential heavy metal that comes from natural and anthropogenic sources, is a teratogen, carcinogen, and a possible mutagen. Assessment of potential risk from cadmium requires understanding environmental exposure, mainly from ingestion, although there is some local exposure through inhalation. Chronic exposure is more problematic than acute exposure for wildlife. There is evidence for bioaccumulation, particularly in freshwater organisms, but evidence for biomagnification up the food chain is inconsistent; in some bird studies, cadmium levels were higher in species that are higher on the food chain than those that are lower. Some freshwater and marine invertebrates are more adversely affected by cadmium exposure than are birds and mammals. There is very little experimental laboratory research on the effects of cadmium in amphibians, birds and reptiles, and almost no data from studies of wildlife in nature. Managing the risk from cadmium to wildlife involves assessment (including ecological risk assessment), biomonitoring, setting benchmarks of effects, regulations and enforcement, and source reduction.  相似文献
5.
鸟巢形网架的构形、受力特性和简化计算方法   总被引:3,自引:0,他引:3  
鸟巢形国家体育场是 2 0 0 8年北京奥运会的中标方案 ,其屋盖主体结构实际上是由两向不规则斜交的平面桁架系组成的椭圆平面网架结构 ,每榀桁架与内环相切或接近相切 ,不妨称其为鸟巢形网架。通过研究和分析圆形平面的鸟巢形网架 ,其结构构形可简化成由统一的一类平面桁架系组成。对于周边简支的圆形鸟巢形网架 ,提出了简化计算法和相应的计算公式 ,可以方便地计算网架各杆件的内力和节点挠度。对于特定参数的鸟巢形网架 ,还给出了内力计算用表 ,以利工程利用。  相似文献
6.
Biodiversity concepts and urban ecosystems   总被引:3,自引:0,他引:3  
The association of biodiversity and urban ecosystems has usually concerned the impact of urbanization on biodiversity. However, biodiversity concepts can easily be applied to the urban ecosystem itself. As more and more people live in cities, restoration, preservation and enhancement of biodiversity in urban areas become important. Concepts related to biodiversity management such as scale, hierarchy, species identity, species values, fragmentation, global approaches can be used to manage urban biodiversity. Application of these concepts in such artificial ecosystems may yield important insights for the management of natural ecosystems. Birds are highly visible and quite sensitive to changes in habitat structure and composition. Bird species richness in urban ecosystems is influenced both by local and landscape characteristics and a multi-scale approach is essential to its proper management. People–wildlife conflicts are an integral component of wildlife management in urban ecosystems and must be addressed. Enhancement of biodiversity in urban ecosystems can have a positive impact on the quality of life and education of urban dwellers and thus facilitate the preservation of biodiversity in natural ecosystems.  相似文献
7.
雁形板的强度与刚度分析   总被引:3,自引:1,他引:2  
用有限元三维结构分析程序计算了跨度为45m的雁形板,所得结果与该计算模型足尺(原型)试验结果一致,由此验证了用比拟梁法对雁形板进行强度和刚度计算的正确性。此外,还对雁形板的设计提出了一些建议。  相似文献
8.
Distribution and habitat selection of wintering birds in urban environments   总被引:3,自引:0,他引:3  
Habitat selection of wintering land-birds was studied in 31 human settlements in Finland. A total of 26 wintering bird species representing 5155 individuals were observed. Between-year variation (CVB%) and short-term fluctuation within one winter (CVW%) in species richness (CVB=10% CVW=15%) were low, as were total numbers of birds (CVB=22% CVW=24%) and populations of the most common bird species (CVB=20–40% CVW=15–47%). The most abundant bird species (e.g., Passer domesticus, Parus major and Pica pica) occurred in most of the study sites. The total densities of omnivorous birds, sedentary birds and bird species that commonly use feeding tables were higher in a heavily urbanized areas than in moderately or less urbanized areas. According to the Canonical Correspondence Analysis, three corvid species populations, P. domesticus and Columba livia domestica were positively related to human population density. Corvus corone cornix and P. domesticus populations correlated positively with the proportion of the built-up areas in the study plots. The omnivorous diet of these species was a possible reason for their success in urban environments. Dendrocopus major, Parus montanus, Parus cristatus, Parus ater and Certhia familiaris were negatively related to the urbanization axis. These species live mainly in coniferous forest habitats and are probably unable to use deciduous-dominated urban parks in winter time. To attract these species, coniferous trees and shrubs should also be used in park management and planning in northern latitudes. Many species, like Pic. pica, Carduelis chloris and Parus caeruleus, were located at an intermediate place on an urban–forest gradient axis. We suppose that these species are the most probable candidates for colonizing or increasing their abundances in European towns and cities in near the future. All of these species use feeding tables, which help them to adapt to urban environments.  相似文献
9.
Samples of two marine bird species, European shag (Phalacrocorax aristotelis) and common eider (Somateria mollissima) sampled at a remote coastal site in Norway were analysed for POPs and PFCs. Additionally samples of common eider were analysed from two other locations in Norway, representing a gradient from “densely populated” to “remote”. The variety, concentration and distribution of lipophilic POPs in comparison to PFCs were investigated. PCBs were the dominating group of contaminants in the analysed egg samples. Shag eggs had median sumPCBs levels of 4580 ng/g l.w. in 2004. Six different PBDE congeners could be detected in the shag eggs. BDE 47 and 100 were the main contributors with 24 and 27 ng/g l.w. respectively, sumPBDEs was 90 ng/g l.w. Relatively high concentrations of chlordanes were found with a total sum of 903 ng/g l.w. Of other OCs, toxaphene 26 and 52 together (sum 657 ng/g l.w.) and HCB (165 ng/g l.w.) were contributing majorly to the egg burden. Sum HCHs were low; only 54 ng/g l.w. PFOS was the main PFC in egg, plasma and liver samples. Similar median levels of 29, 32 and 27 ng/g w.w. were observed. PFOSA, PFHxS, and PFDcA were observed additionally in all shag samples at minor concentrations with the exception of elevated levels observed in liver for PFOSA and PFDcA with median levels of 7.6 and 7.9 ng/g w.w., respectively. In common eider eggs, the POP concentrations decreased up to 1/8th along the sampled spatial gradient from suburban to remote. Of the 9 detected PFCs, PFOS dominated all samples by one order of magnitude, followed by PFOA. SumPFC concentrations were twice as high at the two fjord sites compared to the remote site. Shorter chained PFCAs like PFOA and PFNA could be detected in the eider eggs whilst being absent in shag eggs.  相似文献
10.
Cities represent an important threat to biodiversity at different scales. Nevertheless, little is known on the processes underlying such effects. In this paper we describe bird diversity, structure, and composition patterns in different urban land-use categories. For this, we surveyed resident bird communities in four representative land-use categories of southwestern Mexico City. Our results show that bird communities vary greatly along the different studied urban land-uses, which represent an urbanization development gradient. Bird communities were highly dominated by few generalist species in areas with commercial components, while showed to have higher evenness values in green areas. Bird species richness decreased and bird abundances increased with urbanization intensity. Also, our results indicate that bird species richness and abundance values are sensible to site-specific habitat characteristics. Although we did not find a clear pattern of taxonomic homogenization related to urbanization, our results show that urbanization development entails the functional homogenization of bird communities. Thus, based on our results, we suggest three urban planning and management activities: (1) regulate land-use change related to urbanization; (2) increase the number of green areas within the city; (3) establish bird monitoring programs to identify focal areas that need management and assist with ecological data for urban planning.  相似文献
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