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Forage fish—small, low trophic level, pelagic fish such as herrings, sardines, and anchovies—are important prey species in marine ecosystems and also support large commercial fisheries. In many parts of the world, forage fish fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage fish catch to safeguard their fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage fish abundance on the population growth rates of 45 marine predator populations representing 32 fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the abundance of their forage fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations. 相似文献
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Numerical simulation of reactive processes in an experiment with partially saturated bentonite 总被引:2,自引:0,他引:2
Bentonites are preferred materials for use as engineered barriers for high-level nuclear waste repositories. Simulation of geochemical processes in bentonite is therefore important for long-term safety assessment of those repositories. In this work, the porewater chemistry of a bentonite sample subject to simultaneous heating and hydration, as studied by Cuevas et al. [Cuevas, J., Villar, M., Fernández, A., Gómez, P., Martín, P., 1997. Porewaters extracted from compacted bentonite subjected to simultaneous heating and hydration. Applied Geochemistry 12, 473-481.], was assessed with a non-isothermal reactive transport model by coupling the geochemical software PHREEQC2 with the object-oriented FEM simulator GeoSys/RockFlow. Reactive transport modelling includes heat transport, two-phase flow, multicomponent transport and geochemical reactions in the liquid phase, i.e. ion exchange, mineral dissolution/precipitation and equilibrium reactions. Simulations show that the easily soluble minerals in bentonite determine the porewater chemistry. Temperature affects both two-phase flow and geochemical reactions. Porosity change due to dissolution/precipitation is low during the experiment. However, changes of the effective porosity caused by bentonite swelling can be very large. The simulated results agree well with the experimental data. 相似文献
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Paul Patterson Hari Iyer James Sisler William C. Malm 《Journal of the Air & Waste Management Association (1995)》2013,63(5):790-801
ABSTRACT An apparent increasing trend in the summer concentrations of particulate sulfur at Shenandoah (for the time period 1982-1995) and at Great Smoky Mountains (for the time period 1984-1995) has been pointed out by some researchers. Others have suggested that these increasing trends may be an analytical artifact resulting from the switch from the Stacked Filter Units (SFU) measurement system to the IMPROVE (Interagency Monitoring of Protected Visual Environments) measurement system that occurred during the winter of 1987. To obtain a better understanding of the effect of the protocol change, we investigate the changes in the seasonal averages of sulfur concentrations for successive pairs of years for the period 1980-1996 for about 20 national park sites in the United States. For the period 1980-1987, we use sulfur data from the old (SFU) database and for the period 1988-1996, we use the IMPROVE database. Changes from one year to the next similar to that between 1987 and 1988 occurred during other years and seasons suggesting that chance causes alone could perhaps explain it, the degree to which chance could have caused the changes was measured using the permutation test for matched. At the very least, additional information such as side by side readings using SFU and IMPROVE measurement methods, may be needed to better understand any systematic effect in the sulfur measurements that may be ascribable to the protocol change. 相似文献
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In order for soil resources to be sustainably managed, it is necessary to have reliable, valid data on the spatial distribution of their environmental impact. However, in practice, one often has to cope with spatial interpolation achieved from few data that show a skewed distribution and uncertain information about soil contamination. We present a case study with 76 soil samples taken from a site of 15 square km in order to assess the usability of information gleaned from sparse data. The soil was contaminated with cadmium predominantly as a result of airborne emissions from a metal smelter. The spatial interpolation applies lognormal anisotropic kriging and conditional simulation for log-transformed data. The uncertainty of cadmium concentration acquired through data sampling, sample preparation, analytical measurement, and interpolation is factor 2 within 68.3 % confidence. Uncertainty predominantly results from the spatial interpolation necessitated by low sampling density and spatial heterogeneity. The interpolation data are shown in maps presenting likelihoods of exceeding threshold values as a result of a lognormal probability distribution. Although the results are not deterministic, this procedure yields a quantified and transparent estimation of the contamination, which can be used to delineate areas for soil improvement, remediation, or restricted area use, based on the decision-makers probability safety requirement. 相似文献
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Although conceptually simple and often idealized, disentangling crop–livestock interactions typically proves more complex in practice. Part of the complexity arises from their changing nature along agricultural intensification gradients. Such interactions increase in scope when extensive systems intensify, but decline in importance as already intermediate systems intensify further. This changing nature of crop–livestock interactions in relation to the system’s developmental stage implies that these exchanges can both contribute but also undermine system sustainability. We examine crop–livestock interactions in the Indo-Gangetic Plains as an empirical case, drawing from village surveys to explore and illustrate these relations and implications along the agro-ecological gradient of this vast and important eco-region. Such an understanding is increasingly needed as adapting crop residue management practices is recognized as the key to address sustainability concerns in the prevailing rice–wheat systems and as a stepping stone towards conservation agriculture. The agricultural R&D community needs to incorporate this understanding more proactively into its R&D agenda if it is to succeed in sustaining productivity gains, improving rural livelihoods equitably, and securing environmental sustainability. 相似文献
48.
Robert A. Cudney Eric G. Walther William C. Malm 《Journal of the Air & Waste Management Association (1995)》2013,63(5):468-470
The Environmental Protection Agency is responsible for establishing, reviewing, and revising standards of performance for new stationary sources of air pollution. Since this federal program was authorized in 1970, standards of performance (commonly referred to as new source performance standards or NSPS) have been developed for 34 categories of stationary sources. These regulations have focused primarily on large new sources of particulate matter, NO x , and SO2 emissions. Recently, work has begun on NSPS for a number of source categories that emit volatile organic compounds. Environmental professionals in these industries and in many regulatory agencies have little direct experience with the NSPS program and are unaware of the detailed engineering, cost, and economic information available with each proposed rulemaking. This article, therefore, reviews the purposes, procedures, and benefits of the NSPS program. A summary of the NSPS that have been promulgated through February 1983 are presented in tabular form. 相似文献
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Christopher E. Johnson William C. Malm Gerald Persha John V. Molenar James R. Hein 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1261-1265
An automated scanning densitometer system developed to estimate visibility-related parameters from photographic slides was tested in comparison to similar teleradiometric measurements. Parameters such as target-sky contrast, visual range, atmospheric light extinction coefficient, and plume and layered contrast can be estimated using this system; however, only target-sky radiance ratios and standard visual ranges were compared. More than 1600 concurrent densitometer and teleradiometer data pairs from eight National Park Service air quality and visibility monitoring locations in the western United States were analyzed using the techniques of correlation, linear regression, average bias and difference calculation, and cumulative frequency distribution generation. Correlation coefficients were good, especially with middle-range camera vistas around 50 km distant. Regression slopes approached unity with intercepts near zero. Average bias introduced into the determination of radiance ratios from slides ranged from near zero to 6 percent, depending on target distance. Standard visual range data distributions compared favorably at the low end with some minor differences at the high end. 相似文献