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501.
Ian?F.?Dennis Thomas?A.?ClairEmail author Bernard?J.?Cosby 《Environmental Modeling and Assessment》2005,10(4):303-314
Accurate predictions of acid precipitation effects on water resources are important in order to allow a better understanding
of various pollution control strategy outcomes. Dynamic geochemical models have been developed to address this need, but have
to be tested under a variety of environmental conditions to provide confidence in their predictions. The most commonly used
aquatic acidification model in North America and Europe is the model of acidification of groundwater in catchments (MAGIC).
Though extensively used, MAGIC has never been tested in catchments with extremely low ionic strength water and high in natural
organic acids (NOAs) from wetlands, two conditions which are common in large parts of Canada. We calibrated the model for
two catchments located in Nova Scotia, Canada, which had some of the most dilute freshwaters reported in the literature and
very high NOA. We also evaluated the variability inherent in calibration data sets by using five separate data sets collected
over a 15-year period at the same sites. We show good model simulations for the main cations and anions in catchment waters.
However, modeling pH is more difficult in the highly organic waters and requires modification to the acid dissociation constants.
Calculated acid neutralization capacity can also be more difficult to model due to the low ion content making small errors
more important. In theory, multiple calibrations of a model at a same site should produce identical hindcasts and predictions.
In reality, the multiple calibrations produced a series of similar, but not identical outcomes which give a probable range
of past values and future outcomes. We feel that this practical approach to validation is a useful addition to the arsenal
of model testing tools. 相似文献
502.
The Panulirus ornatus stock in a 25 000 km2 area of Torres Strait was estimated by making visual counts of the number of lobsters in strip transects. Pilot studies in 1988 to assess the feasibility of a full-scale survey and optimize the sampling design showed that: 4×500 m transects were the most cost-effective of the different sizes trialled; two transects per location comprised the most optimal allocation of replication; and 300 locations were necessary to achieve a 95% confidence interval of ±10% of the mean density found in the pilot study. Satellite imagery was used to map habitats in Torres Strait, and areas likely to be inhabited by lobsters were classified broadly into three strata: windward reef slope, submerged reef, and deep areas. The 300 locations were allocated to each stratum in proportion to its area and the estimated variance of lobster abundance within it; once allocated, the locations were positioned at random within each stratum. The main survey was undertaken over a period of 7 wk in May–June 1989, and the resulting estimate of lobster abundance was 14 million with a 95% confidence interval of ±21%. The surveyed population was sampled concurrently to determine its size structure: the pre-fishery year-class comprised 43% of the population; lobsters greater than legal-size comprised 57% and their average tail weight was 346 g. Thus, the estimate of stock size for the study area was 2200 to 3350 t tail weight, which is roughly ten-fold greater than the annual catch of about 250 t. The current catch is approaching the lower estimates of potential yield, calculated using simple maximal sustainable yield estimators, which suggests that the fishery is unlikely to be under threat at present and may support greater effort. 相似文献
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506.
Dennis J. Lye 《Journal of the American Water Resources Association》2002,38(5):1301-1306
ABSTRACT: Rainwater harvesting is receiving increased attention worldwide as an alternative source of drinking water. Although collected rainwater is typically consumed without any type of disinfection, the microbial quality of this type of water source can be poor. Around the world, consumers of collected and stored rainwater may be at considerable risk to a variety of infectious diseases. This review presents studies attributing specific risks of diseases to the consumption of contaminated rainwater. Diseases attributed to the consumption of untreated rainwater include bacterial diarrheas due to Salmonella and Campylobacter, bacterial pneumonia due to Legionella, botulism due to Clostridium, tissue helminths, and protozoal diarrheas from Giardia and Cryptosporidium. Simple indicator systems such as fecal coliform measurements may prove to be inadequate for determining microbial risks associated with consumption of water from rainwater catchment systems. 相似文献
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Woldetsadik Desta Simon Marcel Pierre Knuth Dennis Hailu Hillette Gebresilassie Araya Dejen Asmare Düring Rolf-Alexander 《Environmental geochemistry and health》2021,43(9):3597-3613
Environmental Geochemistry and Health - Khat (Catha edulis) chewing is widespread in the region of East Africa. Even low levels of organochlorine pesticides (OCPs) in khat could induce public... 相似文献
509.
Paul C. Cross Tyler G. Creech Michael R. Ebinger Dennis M. Heisey Kathryn M. Irvine Scott Creel 《Behavioral ecology and sociobiology》2012,66(10):1437-1447
Recent technological advances, such as proximity loggers, allow researchers to collect complete interaction histories, day and night, among sampled individuals over several months to years. Social network analyses are an obvious approach to analyzing interaction data because of their flexibility for fitting many different social structures as well as the ability to assess both direct contacts and indirect associations via intermediaries. For many network properties, however, it is not clear whether estimates based upon a sample of the network are reflective of the entire network. In wildlife applications, networks may be poorly sampled and boundary effects will be common. We present an alternative approach that utilizes a hierarchical modeling framework to assess the individual, dyadic, and environmental factors contributing to variation in the interaction rates and allows us to estimate the underlying process variation in each. In a disease control context, this approach will allow managers to focus efforts on those types of individuals and environments that contribute the most toward super-spreading events. We account for the sampling distribution of proximity loggers and the non-independence of contacts among groups by only using contact data within a group during days when the group membership of proximity loggers was known. This allows us to separate the two mechanisms responsible for a pair not contacting one another: they were not in the same group or they were in the same group but did not come within the specified contact distance. We illustrate our approach with an example dataset of female elk from northwestern Wyoming and conclude with a number of important future research directions. 相似文献
510.
Gerald Schernewski Arunas Balciunas Dennis Gräwe Ulf Gräwe Kristina Klesse Marcus Schulz Sylvie Wesnigk David Fleet Mirco Haseler Nils Möllman Stefanie Werner 《Journal of Coastal Conservation》2018,22(1):5-25
Major objectives were to provide a comprehensive dataset on beach macro-litter for parts of the southern Baltic Sea and to analyse if the methodology is fully applicable and a suitable monitoring method in the Baltic. We carried out a regular macro litter beach monitoring (OSPAR methodology, 4 time a year) on 35 beaches along the German and Lithuanian Baltic coast over 2–5 years. Additional experiments addressed the subjectivity of the field surveys and spatio-temporal variability on different scales. We observed no seasonality of the data and a monthly compared to a 3-monthly sampling resulted in 3 times higher annual item numbers. Along the Lithuanian coast, the average number of items per survey varied between 138 and 340 and along the German Baltic coast between 7 and 404, with a median value of 47. All data showed a very high spatio-temporal variability. Using the Matrix Scoring Technique we assessed beach litter sources. With 50% tourism and recreation was the most important source. 3D–transport simulations helped to explain the minor role of shipping as a source and, compared to the North Sea, the low numbers of items on German Baltic beaches. Floating litter had a short duration time in the western Baltic Sea and offshore drift dominated. Further, the common regular beach cleanings reduced the potential for local litter accumulation and translocation. We suggest a monitoring system on 14 Baltic beaches in Germany and 2 in Lithuania and provide cost calculations. The analysis of macro-litter in cormorant nesting material and the search for beached dead animals did not show any result. We can conclude that the macro-litter beach monitoring method is less suitable for Baltic beaches and should only serve as a complementary method in combination with others. 相似文献