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741.
Scott N. Miller D. Phillip Guertin David C. Goodrich 《Journal of the American Water Resources Association》2007,43(4):1065-1075
Abstract: A stochastic, spatially explicit method for assessing the impact of land cover classification error on distributed hydrologic modeling is presented. One‐hundred land cover realizations were created by systematically altering the North American Landscape Characterization land cover data according to the dataset’s misclassification matrix. The matrix indicates the probability of errors of omission in land cover classes and is used to assess the uncertainty in hydrologic runoff simulation resulting from parameter estimation based on land cover. These land cover realizations were used in the GIS‐based Automated Geospatial Watershed Assessment tool in conjunction with topography and soils data to generate input to the physically‐based Kinematic Runoff and Erosion model. Uncertainties in modeled runoff volumes resulting from these land cover realizations were evaluated in the Upper San Pedro River basin for 40 watersheds ranging in size from 10 to 100 km2 under two rainfall events of differing magnitudes and intensities. Simulation results show that model sensitivity to classification error varies directly with respect to watershed scale, inversely to rainfall magnitude and are mitigated or magnified by landscape variability depending on landscape composition. 相似文献
742.
Stephen P. Opsahl Scott E. Chapal David W. Hicks Christopher K. Wheeler 《Journal of the American Water Resources Association》2007,43(5):1132-1141
Abstract: In the karstic lower Flint River Basin, limestone fracturing, jointing, and subsequent dissolution have resulted in the development of extensive secondary permeability and created a system of major conduits that facilitate the exchange of water between the Upper Floridan aquifer and Flint River. Historical streamflow data from U.S. Geological Survey gaging stations located in Albany and Newton, Georgia, were used to quantify ground‐water and surface‐water exchanges within a 55.3 km section of the Flint River. Using data from 2001, we compared estimates of ground‐water flux using a time adjustment method to a water balance equation and found that these independent approaches yielded similar results. The associated error was relatively large during high streamflow when unsteady conditions prevail, but much lower during droughts. Flow reversals were identified by negative streamflow differences and verified with in situ data from temperature sensors placed inside large spring conduits. Long‐term (13 years) analysis showed negative streamflow differentials (i.e., a losing stream condition) coincided with high river stages and indicated that streamflow intrusion into the aquifer could potentially exceed 150 m3/s. Although frequent negative flow differentials were evident, the Flint River was typically a gaining stream and showed a large net increase in flow between the two gages when examined over the period 1989‐2003. Ground‐water contributions to this stream section averaged 2‐42 m3/s with a mean of 13 m3/s. The highest rate of ground‐water discharge to the Flint River occurred during the spring when regional ground‐water levels peaked following heavy winter and spring rains and corresponding rates of evapotranspiration were low. During periods of extreme drought, ground‐water contributions to the Flint River declined. 相似文献
743.
This study proposed and tested relationships pertaining to employee perceptions of psychological contract type over time. Using a longitudinal design, we examined the mediated role that adequacy of social accounts and psychological contract fulfillment play in determining the development of contract perceptions. More specifically, our model posits that perceptions of contract type will influence employee perceptions of the adequacy of social accounts that are offered by the organization and its agents to explain job‐related decisions. These initial perceptions of social accounts at Time 1 were expected to impact perceptions of psychological contract fulfillment at Time 2 (6 months later) and psychological contract fulfillment was proposed to be positively associated with perceptions of a relational psychological contract. Results support the mediating roles of social accounts and psychological contract fulfillment in determining perceptions of contract type over time. Practical implications of these findings and directions for future research are discussed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
744.
Diamond DD True CD Gordon TM Sowa SP Foster WE Jones KB 《Environmental management》2005,35(2):130-137
We used an existing conservation opportunity area (OA) data layer for four contiguous ecological subsections within the Ozark Highlands to quantitatively evaluate the influence of conservation targets and assessment region size on conservation priorities. OAs are natural and seminatural land-cover patches that are away from roads and away from patch edges. To evaluate the influence of targets, we assigned a priority score to each OA polygon for each of five different conservation targets, including land-cover patch size, landform representation, target vertebrate richness, target breeding bird richness, and target land cover. The top-scoring OAs for each target were added to an OA selection set for that target until 50% of the study area was chosen. These five OA selection sets were overlain to quantify overlap in priorities. Only 1.6% of the study area, or 2.1% of all OA polygons, was selected by all five targets. To evaluate the influence of assessment region size, we compared results of priority ranking of OAs relative to the entire study area against a merged set of priority rankings established separately relative to each of the four subsections within the study area. When high-priority OAs were added until 25% of the region was within the selection set for each of the five targets, the sets based on the whole study area versus each subsection evaluated separately overlapped from 45.4% to 81.9%. Thus, perceived priorities of conservation assessments are strongly influenced both by the targets that are evaluated and by the size of the assessment region. 相似文献
745.
An experiment was performed to examine the phytoremediation potential of Rhodes grass (Chloris gayana Kunth cv. ‘Pioneer’). The study sought to determine substrate tolerance, biomass production, and plant uptake of antimony (Sb), arsenic (As), cadmium (Cd), lead (Pb), silver (Ag), and zinc (Zn). The plants were grown on weight percent mixtures (5 percent, 15 percent, 25 percent, 35 percent, 50 percent) of a vertisol soil and base‐metal mine tailings (7–2,040 μg/g As, ≥ 30 μg/g Cd, 30–12,000 μg/g Pb, and 72–4,120 μg/g Zn). The 5 percent and 15 percent amendment of mine tailings increased the biomass production of Rhodes grass (from 0.1 g/plant to ≈ 3.5 g/plant) without appreciably elevating plant concentrations of the elements. Plant growth decreased by greater than 50 percent for the substrate containing greater than 25 percent tailings (3,023 μg/g Pb and 1,084 μg/g Zn). Reduced biomass production coincided with maximal Zn uptake by Rhodes grass (249.8 μg/g), indicating tailings induced phytotoxicity. The total concentrations of metals and metalloids tolerated by Rhodes grass in the plant‐growth medium indicated hypertolerance to elevated As, Pb, and Zn concentrations. Partial extraction of the plant‐growth medium determined that plant‐available Pb was ten times higher than Ag, As, Cd, and Zn availability. However, Rhodes grass accumulated low levels of Pb, in addition to As and Cd, over the experimental range, indicating low fodder toxicity risk to browsing livestock. This study concludes that if there are no invasive species issues associated with conservation land uses, Rhodes grass is well suited to metalliferous mined land revegetation and would therefore be highly effective for such programs in subtropical and tropical Australia. © 2005 Wiley Periodicals, Inc. 相似文献
746.
We made use of land cover maps, and land use change associated with urbanization, to provide estimates of the loss of natural
resource lands (forest, agriculture, and wetland areas) across the 168,000 km2 Chesapeake Bay watershed. We conducted extensive accuracy assessments of the satellite-derived maps, most of which were produced
by us using widely available multitemporal Landsat imagery. The change in urbanization was derived from impervious surface
area maps (the built environment) for 1990 and 2000, from which we estimated the loss of resource lands that occurred during
this decade. Within the watershed, we observed a 61% increase in developed land (from 5,177 to 8,363 km2). Most of this new development (64%) occurred on agricultural and grasslands, whereas 33% occurred on forested land. Some
smaller municipalities lost as much as 17% of their forest lands and 36% of their agricultural lands to development, although
in the outlying counties losses ranged from 0% to 1.4% for forests and 0% to 2.6% for agriculture. Fast-growing urban areas
surrounded by forested land experienced the most loss of forest to impervious surfaces. These estimates could be used for
the monitoring of the impacts of development across the Chesapeake Bay watershed, and the approach has utility for other regions
nationwide. In turn, the results and the approach can help jurisdictions set goals for resource land protection and acquisition
that are consistent with regional restoration goals. 相似文献
747.
In South Africa an intensive reform process to democratize policy, legislation and related institutions in the country commenced after the first democratic elections in 1994. While environmental law reform includes active public participation and equity principles, it is proposed in this paper that ecological modernization dominates current environmental assessment practice. This paper presents a Social Impact Assessment (SIA) of a proposed landfill on the periphery of Durban, where large informal settlements and peri-urban areas exist as a relic of apartheid planning. The methodology of the SIA was explicitly designed within a framework of social justice to include poor and marginalized people, who remain excluded from environmental decision making despite the promise of democratic equality. The study claims to deepen democratic practice by demonstrating that alternative methodologies can be designed to include the interests of ‘invisible stakeholders’ in environmental assessments despite the dominance of ecological modernization in the implementation of environmental law and policy. 相似文献
748.
749.
Scott W. Miller Quentin D. Skinner Katta J. Ready 《Journal of the American Water Resources Association》2004,40(5):1173-1188
ABSTRACT: Responses of the Wyoming Stream Integrity Index (WSII), a regionally calibrated multimetric index, were investigated in relation to background elevational changes in water quality and habitat conditions versus accelerated anthropogenic degradation at the watershed scale. Assessments were conducted for three rivers in southeast Wyoming: the Little Medicine Bow River, the Medicine Bow River, and Rock Creek. Pearson correlation coefficients and regression models related “core metrics” and index scores to elevational gradients of physicochemical variables. Velocity, substrate, and weighted habitat values were positively correlated to index scores, while suspended solids was negatively correlated. The exclusive dependence of index scores on physical variables specifies the type of environmental gradients the WSII is most robust in detecting. The individual “core metrics” Plecoptera taxa, Trichoptera taxa, percent Trichoptera without Hydropsychidae, and percent noninsects appeared most sensitive to physical changes and were thus driving associations between index scores and physical variables. Despite strong correlations with physical variables, anomalies existed where habitat conditions were good, unknown stressors existed, or gradients were naturally occurring despite “Poor” index scores (i.e., degraded stream conditions). Such findings illustrate the influence of regional variability on biotic indices and the importance of identifying sufficient reference and impaired stream reaches used to develop and calibrate multimetric indices relying on reference conditions. 相似文献
750.
Scott A. Smith 《环境质量管理》1997,6(3):43-47
Companies today are continuously improving their efforts to incorporate an environmental management system (EMS) in their everyday operations and work practices, with an emphasis on identifying and reducing risks. Risks may include the cost of enforcement penalties, potential workplace dangers to employees, or cleanup liabilities due to past or present practices. Environmental auditing is an effective tool commonly used to enhance an EMS. Typically, there are two levels of auditing: (1) a review of management systems and (2) a review of compliance with regulatory requirements. There is yet another intermediate level of auditing that is more focused than management systems or compliance audits—compliance delivery systems (CDS) audits. This article examines the elements making up these systems for improving compliance performance and provides a ?ready to use”? checklist of items for managers to begin implementation. 相似文献