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791.
Dungan RS Papiernik S Yates SR 《Journal of environmental science and health. Part. B》2005,40(2):355-362
Atmospheric emission of the soil fumigant 1,3-dichloropropene (1,3-D) has been associated with the deterioration of air quality in certain fumigation areas. To minimize the environmental impacts of 1,3-D, feasible and cost-effective control strategies are in need of investigation. One approach to reduce emissions is to enhance the surface layer of a soil to degrade 1,3-D. A field study was conducted to determine the effectiveness of composted steer manure (SM) and composted chicken manure (CKM) to reduce 1,3-D emissions. SM or CKM were applied to the top 5-cm soil layer at a rate of 3.3 or 6.5 kg m(-2). An emulsified formulation of 1,3-D was applied through drip tape at 130.6 kg ha(-1) into raised beds. The drip tape was placed in the center of each bed (102 cm wide) and 15 cm below the surface. Passive flux chambers were used to measure the loss of 1,3-D for 170 h after fumigant application. Results indicated that the cumulative loss of 1,3-D was about 48% and 28% lower in SM- and CKM-amended beds, respectively, than in the unamended beds. Overall, both isomers of 1,3-D behaved similarly in all treatments. The cumulative loss of 1,3-D, however, was not significantly different between the two manure application rates for either SM or CKM. The results of this study demonstrate the feasibility of using composted animal manures to control 1,3-D emissions. 相似文献
792.
Edge Effects and Isolation: Red-Backed Voles on Forest Remnants 总被引:7,自引:0,他引:7
L. Scott Mills 《Conservation biology》1995,9(2):395-403
Negative effects of habitat edge have been advanced as an important proximate cause of extinction, and a growing literature calls attention to the matrix surrounding habitat remnants as a critical factor determining population persistence. I examined spatial distribution of California red-backed voles ( Clethrionomys californicus ) on 13 forest remnants and five control sites in southwestern Oregon. The species was virtually isolated on remnants, making little use of the regenerating clearcuts surrounding the remnants. The effects of the clearcut also impinged on the remnants as edge effects: six times more voles were captured per trap in the interior of remnants than on the edge. Consequently, the density of voles per unit area on remnants increased with remnant size, despite the potential buildup of population density in small isolates due to limited emigration. I explored potential mechanisms of the negative edge effect on voles and found that the biomass of coarse woody debris, per se, did not explain the vole distribution because both number and volume of logs increased from the interior to the edge of remnants. However, the distribution of the vole's primary food item, hypogeous sporocarps of mycorrhizal fungi, did correspond to the vole edge effect 相似文献
793.
Thomas P. Hurst Clifford H. Ryer Jessica M. Ramsey Scott A. Haines 《Marine Biology》2007,151(3):1087-1098
Despite facing similar constraints imposed by the environment, significant variation in life history traits frequently exists
among species generally considered to comprise a single ecological guild. For juvenile flatfishes, constraints on foraging
activity include variation in light and prey availability, as well as predation risk. This paper describes the visual constraints
on, and divergent foraging strategies of three co-occurring north Pacific flatfish species, northern rock sole (Lepidopsetta polyxystra), Pacific halibut (Hippoglossus stenolepis), and English sole (Pleuronectes vetulus). Visual foraging abilities measured in the laboratory decreased rapidly below 10−4 μmol photons·m−2 s−1, and were similar among species. Despite similar sensory constraints, field sampling in August 2004 at a Kodiak Island nursery
site (Holiday Beach, 57o41.2′ N, 152o27.7′ W) identified species differences in diets, diel foraging patterns, and within-nursery depth distributions. Northern
rock sole and English sole fed primarily on bivalve siphons and polychaetes, whereas mysids dominated the diets of Pacific
halibut. Northern rock sole were geographically the most widespread but feeding activity was temporally restricted to the
dusk period. Pacific halibut were rare in shallow depths (<5 m) and fed most intensively prior to dusk. English sole fed throughout
the daylight hours and were abundant only in the shallowest (<5 m) habitats. These differences in diets, foraging times, and
habitat use appear related to previously documented species-specific behavioral characteristics as well as general spatial
(increasing with depth) and temporal (increasing during foraging activity) variations in predation risk. At one extreme, the
conservative behavioral strategy of northern rock sole may permit use of a broader range of foraging habitats, whereas English
sole may be restricted to shallow water by limited behavioral responses to predation threat. These observations demonstrate
that the appearance of habitat partitioning is not due to differences in sensory ability, but reflects multi-faceted, species-specific
responses to the ecological tradeoffs between foraging and predation risks. 相似文献
794.
Scott?A.?MalcolmaEmail author Charles?ReVelle 《Environmental Modeling and Assessment》2005,10(4):341-348
Models for designing habitat reserve networks have focused on minimizing the number of sites necessary to cover each species
one or more times. A solution to this problem is usually one from among a large number of alternative optimal configurations
of sites. This paper develops an iterative method for building reserve networks that produces an optimal solution to the species
set covering problem (SSCP) and also maximizes the number of species covered two or more times, three or more times, and so
on, conditional on the solution to the previous iteration. We refer to this as representational success. Thus, a pareto optimal species set covering is achieved that is preferable to an arbitrary optimal solution to the SSCP. 相似文献
795.
Almost 2700 samples of human renal cortex have been collected from throughout the UK over a 16 year period from 1978 to 1993. The mean Cd concentration was 19 micrograms g-1 and the median 16 micrograms g-1. Smokers were, on average, about 5 micrograms g-1 higher than non-smokers. Cd increased from low concentration in the young to a maximum of 23 micrograms g-1 in middle age followed by a decrease in old age. Subjects who had died of renal disease had lower Cd concentrations. Geographical variations in the UK are small and the concentrations appear to be static over the 16 year period. Some 3.9% of the population had Cd concentrations > 50 micrograms g-1, the critical level at which beta 2-microglobulin appears in urine. 相似文献
796.
An attempt is made to determine the bioavailability of persistent organic pollutants (POP's) in environmental matrices. The approach is based on the use of the Hildebrand Solubility Parameter, and its individual parameters of hydrogen bonding, dispersion and polarity to select weak and strong solvents to extract POP's from soil matrices. The approach has been applied to both spiked soils and certified reference materials. Initial results indicate that it is possible to fractionate POP's from soil matrices based on their ability to be extracted from soil by particular solvents. 相似文献
797.
Scott F. Archer John V. Molenar David L. Dietrich 《Environmental monitoring and assessment》1989,12(1):60-60
The Grand Canyon, located in Northern Arizona, is one of the seven natural wonders of the world, and has been set aside as a National Park to preserve its unique character. Several million visitors from all over the world travel to the Grand Canyon each year to witness its awesome beauty, As a natural preserve, the area protects numerous values such as genetic diversity, solitude, non-mechanized recreation, etc, but the majority of visitors travel to the Grand Canyon for one reason: to view the scenery.There have been reports in the general press (and even in the United States Congressional Hearings) that visual conditions at the Grand Canyon have been seriously degraded by air pollution. Over the past nine years, a vast array of visibility-related research and monitoring has been conducted to determine the extent and probable cause of this visible degradation. Studies have included optical measurements, pollution characterization, source-receptor relationship analysis, and human perception of visual air quality. The resulting data document the visual air quality of the Grand Canyon and provide a basis to qualitatively and quantitatively evaluate significant events and trends. 相似文献
798.
Analysis of Calabash chalk has been done using energy dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction (XRD) and pressurised fluid extraction (PFE) followed by gas chromatography (GC) with mass selective detection (MSD). It was found by XRD that the composition of Calabash chalk was an aluminium silicate hydroxide from the kaolin clay group with the possible formula Al(2)Si(2)O(5)(OH)(4). Multi-elemental analysis by EDXRF was able to quantify 22 elements in Calabash chalk including lead at a mean concentration of approximately 40 mg/kg. A range of persistent organic pollutants were identified and quantified in Calabash chalk including alpha lindane, endrin, endosulphan II and p,p'-DDD using PFE-GC-MSD. 相似文献
799.
800.
Behrentz E Sabin LD Winer AM Fitz DR Pankratz DV Colome SD Fruin SA 《Journal of the Air & Waste Management Association (1995)》2005,55(10):1418-1430
Real-time concentrations of black carbon, particle-bound polycyclic aromatic hydrocarbons, nitrogen dioxide, and fine particulate counts, as well as integrated and real-time fine particulate matter (PM2.5) mass concentrations were measured inside school buses during long commutes on Los Angeles Unified School District bus routes, at bus stops along the routes, at the bus loading/unloading zone in front of the selected school, and at nearby urban "background" sites. Across all of the pollutants, mean concentrations during bus commutes were higher than in any other microenvironment. Mean exposures (mean concentration times time spent in a particular microenvironment) in bus commutes were between 50 and 200 times greater than those for the loading/unloading microenvironment, and 20-40 times higher than those for the bus stops, depending on the pollutant. Although the analyzed school bus commutes represented only 10% of a child's day, on average they contributed one-third of a child's 24-hr overall black carbon exposure during a school day. For species closely related to vehicle exhaust, the within- cabin exposures were generally dominated by the effect of surrounding traffic when windows were open and by the bus's own exhaust when windows were closed. Low-emitting buses generally exhibited high concentrations only when traveling behind a diesel vehicle, whereas high-emitting buses exhibited high concentrations both when following other diesel vehicles and when idling without another diesel vehicle in front of the bus. To reduce school bus commute exposures, we recommend minimizing commute times, avoiding caravanning with other school buses, using the cleanest buses for the longest bus routes, maintaining conventional diesel buses to eliminate visible emissions, and transitioning to cleaner fuels and advanced particulate control technologies as soon as possible. 相似文献