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1.
Despite a rapidly improving fossil record, the reproductive biology of Mesozoic birds remains poorly known: only a handful of undisputed, isolated Cretaceous eggs (some containing embryonic remains) are known. We report here the first fossil evidence for a breeding colony of Mesozoic birds, preserved at the Late Cretaceous (Maastrichtian) Oarda de Jos (Od) site in the Sebe? area of Transylvania, Romania. A lens of calcareous mudstone with minimum dimensions of 80?cm length, 50?cm width and 20?cm depth contains thousands of tightly packed, morphologically homogenous eggshell fragments, seven near-complete eggs and neonatal and adult avialan skeletal elements. Eggshell forms 70–80?% of the matrix, and other fossils are entirely absent. The bones exhibit clear characters of the Cretaceous avialan clade Enantiornithes, and the eggshell morphology is also consistent with this identification. Both taphonomy and lithology show that the components of this lens were deposited in a single flood event, and we conclude that it represents the drowned remains of a larger enantiornithine breeding colony, swamped by rising water, washed a short distance and deposited in a shallow, low-energy pond. The same fate often befalls modern bird colonies. Such a large concentration of breeding birds suggests aquatic feeding in this species, augments our understanding of enantiornithine biology and shows that colonial nesting was not unique to crown birds.  相似文献   
2.
One would hypothesize that the Common Fisheries Policy, as the umbrella framework for fisheries management in the EU would have the greatest impact on fishers’ communities across Europe. There are, however, biological, economic, social, and political factors, which vary among fishing communities that can affect how these communities react to changes. This paper explores the links between institutional arrangements and ecological dynamics in two European inshore fisheries socio-ecological systems, using a resilience framework. The Mediterranean small-scale fishers do not seem to have been particularly affected by the Common Fisheries Policy regulations but appear affected by competition with the politically strong recreational fishers and the invasion of the rabbit fish population. The inshore fishers along the East coast of Scotland believe that their interests are not as sufficiently protected as the interests of their offshore counterpart. Decisions and initiatives at global, EU, and sometimes national level, tend to take into account those fisheries sectors which have a national economic importance. A socio-ecological analysis can shift the focus from biological and economic aspects to more sustainable long-term delivery of environmental benefits linked to human wellbeing.  相似文献   
3.
At the beginning of the federal program in 1955, air pollution was viewed as a technical challenge. While technical problems remain, emphasis is shifting toward the social challenge. The degree of federal assistance now available to states and municipalities, under the Clean Air Act, is of broadened scope and higher order of magnitude; it is not confined to technical considerations, but has been expanded to take cognizance of political and economic obstacles that often block the path toward better air pollution control.  相似文献   
4.
The paper describes the results of a study of the impact of the National Energy on the trend towards increased utilization of coal and lignite in Texas with forecasts of increased coal and lignite utilization for the electric utility and industrial sectors. Environmental impacts of this increased coal and lignite use are projected in terms of increased air pollutant emissions and air quality impacts. Economic costs of compliance with alternative source emission regulations are also projected for the electric utility industry.Lignite consumption in Texas under the National Energy Plan is projected to increase from the present 13 million metric tons in 1976 to 57 million metric tons annually by 1985. Sub-bituminous coal consumption in Texas is projected to increase from 1 million metric per year in 1976 to 49 million metric tons per year in 1985. Bituminous coal consumption in Texas is expected to increase from less than one million metric tons per year in 1976 to about 3 million metric tons per year in 1985.Major increases in sulfur oxides emissions from coal and lignite combustion in Texas can be expected by 1985 of up to 1.5 × 109 kg per year without controls and 0.2 × 109 kg per year with controls. Increases in acid precipitation formation will result in north-east Texas from extensive lignite usage for electric power generation as a detriment to agriculture. The photochemical air pollution problem in the Houston area will probably worsen primarily because of increased nitrogen oxides and sulfur oxides emissions because of industrial coal combustion. Capital costs of air pollution controls in Texas for coal-fired utility boilers are estimated as up to U.S. $3.9 billion by 1985, with total operating costs of up to U.S. $1.2 billion per year.  相似文献   
5.
M. Kaiser  F. Spence 《Marine Biology》2002,141(2):321-331
A survey was undertaken of the benthic communities found at ten stations that were sampled by Norman Holme in the 1950s. These stations were selected because Holme recorded the presence of large bivalve species (Glycymeris glycymeris and Paphia rhomboides). Fauna with large body-size are known to be most susceptible to disturbance by human activity, so the presence or absence of these organisms might indicate whether such disturbance has increased at these sites since the 1950s. As expected, differences were detected in the community composition between sites that were located in deeper or shallower water. These differences were consistent for the communities sampled in the present study and for those sampled by Holme. The brittlestar Ophiothrix fragilis was highly abundant at only one site. Nevertheless, long-lived bivalve species still occurred at most of the sites sampled in 1998. G. glycymeris was absent from two sites sampled in 1998 and P. rhomboides was absent from only one site in 1998. Holme suggested that his reported decline in the abundance of O. fragilis might be attributed to the increase in bottom fishing in the English Channel. However, the continued presence of long-lived bivalves at most sites would suggest that other factors could be responsible. A comparison of bivalve and echinoderm species that occurred in the 1950s and in 1998 indicated the occurrence of relatively large temporal changes, as might be expected over a period of more than 40 years. However, this occurred at eight of the ten sites. At two sites, the spatial variation was quantitatively similar to the temporal variation. This suggests that areas of the sea bed exist that have a similar community composition to those found prior to the general increase in bottom-fishing disturbance.  相似文献   
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