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501.
The hilly area of Loess Plateau has some of the highest soil erosion rates in the world, and serious soil erosion causes great
losses of plant nutrients. As the most common land use in Loess Plateau, slope farmland contributed most of the erosion soils.
This study was designed to examine the effects of land use and slope angle of farmland on phosphorus (P) loss in the hilly
area of loess plateau. Farmland (FR), barrenland (BR), and four forest treantment (seabuckthorn+ poplar (SP), immature seabuckthorn
(IS), mature seabuckthorn (MS), immature Chinese pine (ICP)) were the types of land use; 10, 15, 20, 25, 30 degrees were the
slope angles of FR that were compared. The results showed a larger proportion of P loss occurred in erosion soil fraction
of FR, ICP, ICP, and the five slope treatments of FR; in SP, IS, and MS, P loss was primarily through runoff. FR produced
more P loss than SP, IS, ICP, BR, and MS. 20∼30 degrees may be the slope ranges for P loss of FR; FR in this ranges would
loss more P with soil erosion. SP, IS, and MS were reasonable land uses for their less runoff, soil loss, and P loss. Farmlands
over 15 degrees should be abandoned or reforested for it would produce more runoff, soil loss, and P loss. 相似文献
502.
为了解无锡市地下水水质状况,于2010年10—12月对无锡地区145口地下水井进行采样分析。以地理信息系统为技术手段,对不同土地利用类型和地下水类型的水污染物监测结果进行综合评价。结果表明,无锡全市地下水达标率为45.52%,整体水质情况处于"较好"级别;NH3-N、Mn和Fe为无锡市地下水的主要污染物;无锡市农业和建设用地区域地下水的污染程度整体要高于水体和林地区域;承压层的地下水污染较为严重。提出,无锡市管理部门应根据地下水污染现状,对地下水资源进行动态监测(包括水量和水质监测),并采取强有力的保护与治理措施,以实现区域水资源的持续利用。 相似文献
503.
This article examines the utilization characteristics and importance of woody biomass resources in the rural-urban fringe
zones of Botswana. In the literature for Africa, attention has been given to the availability and utilization of biomass in
either urban or rural environments, but the rural-urban fringe has been neglected. Within southern Africa, this neglect is
not justified; the rural-urban fringe, not getting the full benefits available in urban environments in Botswana, has developed
problems in woody biomass availability and utilization that require close attention. In this article, socioeconomic data on
the importance of woody biomass in the Batlokwa Tribal Territory, on the rural-urban fringe of Gaborone, Botswana, were collected
together with ecologic data that reveal the utilization characteristics and potential for regrowth of woody biomass. The analysis
of these results show that local woody biomass is very important in the daily lives of communities in the rural-urban fringe
zones and that there is a high level of harvesting. However, there is no effort in planning land use in the tribal territory
to either conserve this resource or provide alternatives to its utilization. The future of woody biomass resources in Botswana’s
rural-urban fringe is uncertain. The investigators recommend that a comprehensive policy for the development of the rural-urban
fringe consider the importance of this resource. The neglect of this resource will have far-reaching implications on the livelihoods
of residents as well as the environment in this zone. 相似文献
504.
Large lowland river valleys include a variety of floodplain environments that represent opportunities and constraints for
human activities. This study integrates extensive field observations and geomorphic data with analysis of satellite remote
sensing data to examine spatial relations between land use/land cover (LULC) and floodplain environments in the lower Pánuco
basin of eastern Mexico. The floodplain of the lower Pánuco basin was delineated by combining a digital elevation model with
a satellite image of a large flood event. The LULC was classified by combining a hybrid classification strategy with image
stratification, applied to 15-m-resolution ASTER data. A geomorphic classification of floodplain environments was performed
using a dry-stage image (ASTER data) and a 1993 Landsat image acquired during a large flood event. Accuracy assessment was
based on aerial photographs (1:38,000), global positioning satellite ground-truthing, and a Landsat 7ETM+ image from 2000, which resulted in an overall accuracy of 82.9% and a KHAT of 79.8% for the LULC classification. The geomorphic
classification yielded 83.5% overall accuracy, whereas the KHAT was 81.5%. LULC analysis was performed for the entire floodplain
and individually within four valley segments. The analysis indicates that the study area is primarily utilized for grazing
and farming. Agriculture is primarily associated with coarse-grained (sandy/silty) natural levee and point bar units close
to the river channel, whereas cattle grazing occurs in distal and lower-lying reaches dominated by cohesive fine-grained (clayey)
deposits, such as backswamps. In the Pánuco valley, wetlands and lakes occur within backswamp environments, whereas in the
Moctezuma segments, wetlands and lakes are associated with relict channels. This study reveals considerable variation in LULC
related to spatial differences in floodplain environments and illustrates the importance of considering older anthropogenic
influences on the landscape. The research design should be applicable for other large lowland coastal plain river valleys
where agriculture is a major component of the floodplain landscape. 相似文献
505.
In recent years, improvements in point-source depuration technologies have highlighted the problems regarding agricultural
nonpoint (diffuse) sources, and this issue has become highly relevant from the environmental point of view. The considerable
extension of the areas responsible for this kind of pollution, together with the scarcity of funds available to local managers,
make minimizing the impacts of nonpoint sources on a whole basin a virtually impossible task. This article presents the results
of a study intended to pinpoint those agricultural areas, within a basin, that contribute most to water pollution, so that
operations aimed at preventing and/or reducing this kind of pollution can be focused on them. With this aim, an innovative
approach is presented that integrates a field-scale management model, a simple regression model, and a geographic information
system (GIS). The Lake Vico basin, where recent studies highlighted a considerable increase in the trophic state, mainly caused
by phosphorus (P) compounds deriving principally from the intensive cultivation of hazelnut trees in the lake basin, was chosen
as the study site. Using the management model Groundwater Loading Effects of Agricultural Management Systems (GLEAMS), the
consequences, in terms of sediment yield and phosphorus export, of hazelnut tree cultivation were estimated on different areas
of the basin with and without the application of a best management practice (BMP) that consists of growing meadow under the
trees. The GLEAMS results were successively extended to basin scale thanks to the application of a purposely designed regression
model and of a GIS.
The main conclusions can be summarized as follows: The effectiveness of the above-mentioned BMP is always greater for erosion
reduction than for particulate P reduction, whatever the slope value considered; moreover, the effectiveness with reference
to both particulate P and sediment yield production decreases as the slope increases. The proposed approach, being completely
distributed, represents a considerable step ahead compared to the semidistributed or lumped approaches, which are traditionally
employed in research into tools to support the decision-making process for land-use planning aimed at water pollution control. 相似文献
506.
This paper presents a spatially explicit bioeconomic analysis of species conservation in agricultural areas. Wild species in fragmented agricultural landscapes are best approached as metapopulations consisting of a finite number of local populations. Economic analysis of species conservation in fragmented habitat needs to deal with metapopulation theory and its theoretical implications. This paper presents a spatially explicit bioeconomic model consisting of a straightforward economic land use model and an applied metapopulation model. This paper demonstrates that multiple equilibria and multiple local optima in metapopulations might lead to nonconvexities in the production possibilities set of agricultural profits and species conservation. 相似文献
507.
In biologically mega-diverse countries that are undergoing rapid human landscape transformation, it is important to understand and model the patterns of land cover change. This problem is particularly acute in Colombia, where lowland forests are being rapidly cleared for cropping and ranching. We apply a conceptual model with a nested set of a priori predictions to analyse the spatial and temporal patterns of land cover change for six 50-100 km(2) case study areas in lowland ecosystems of Colombia. Our analysis included soil fertility, a cost-distance function, and neighbourhood of forest and secondary vegetation cover as independent variables. Deforestation and forest regrowth are tested using logistic regression analysis and an information criterion approach to rank the models and predictor variables. The results show that: (a) overall the process of deforestation is better predicted by the full model containing all variables, while for regrowth the model containing only the auto-correlated neighbourhood terms is a better predictor; (b) overall consistent patterns emerge, although there are variations across regions and time; and (c) during the transformation process, both the order of importance and significance of the drivers change. Forest cover follows a consistent logistic decline pattern across regions, with introduced pastures being the major replacement land cover type. Forest stabilizes at 2-10% of the original cover, with an average patch size of 15.4 (+/-9.2)ha. We discuss the implications of the observed patterns and rates of land cover change for conservation planning in countries with high rates of deforestation. 相似文献
508.
Ibrahim Yakubu 《The Environmentalist》2008,28(4):376-378
In order to prevent ‘an impending neem failure’, from the incidence of the twin problems of the neem scale insect infestations
and neem dieback, six authenticated provenances (Allahabad, Karnataka, Jodphur, Madinipur, Mukkambu and Annur), from the natural
range of the species in India, were collected and appraised for survival in a degraded land in Kano, Nigeria. Established
in a completely randomised block design with four replications, the trial was conducted with a view to restrengthening and/or
replacing the already weakened Local Land Race of the species in the study area. There was a statistically significant difference
in the survival of the seven provenances. The established differences are between Allahabad 83% (6.40 SEM), Mukkambu 83% (6.40 SEM),
Annur 76% (4.90 SEM), Jodphur 63% (15.09 SEM) and Madinipur 56% (6.73 SEM), on the one hand, and Karnataka 17% (1.91SEM) and
the Local Land Race, with 13% (0.13 SEM), on the other hand. The research recommends Allahabad and Mukkambu 83% (6.40 SEM)
based on this outstanding performance. 相似文献
509.
Differences in rural landscape perceptions and preferences between farmers and naturalists 总被引:2,自引:0,他引:2
A long history of human–nature interactions mediated by agriculture, resulted in high biodiversity in Japanese rural landscapes. This diversity faces drastic decline due to the changes following the socioeconomic circumstances regarding agriculture. Rural conservation will require cooperation among major stakeholders, and knowing how preferences for and perceptions of rural landscapes differ among them can help crafting and implementing effective conservation measures. This study investigated how perceptions of rural landscapes in the Arai-Keinan region, Niigata, Japan differ among people having very different relationships to them. In a photograph-based semantic differential survey, farmers and naturalists, major stakeholders in rural conservation, rated both rice paddy and woodland landscapes. In determining preferences for rice paddy landscapes, perceptions of stewardship and openness were significantly more important for farmers, whereas those of naturalness and biodiversity were significantly more important for naturalists. Such group differences were not found for woodland landscapes. Analysis of perceptions for landscape changes suggested that farmers may have higher normative criteria for rural landscapes than naturalists. Group preferences for intensified rice paddies on sloped topography may conflict, and any rural conservation planning effort should carefully consider that farmers and naturalists consider different aspects of landscapes as important. 相似文献
510.
Effects of grassland conversion to croplands on soil organic carbon in the temperate Inner Mongolia 总被引:1,自引:0,他引:1
This study investigated the effects of grassland conversion to croplands on soil organic carbon (SOC) in a typical grassland-dominated basin of the Inner Mongolia using direct field samplings. The results indicated that SOC contents decreased usually with increasing soil depth, with significant differences between the upper horizons (0-30cm) and the underlying horizons (30-100cm). Also, SOC densities decreased with an increase in the depth of soils. Average SOC densities in the upper horizons were 2.6-3.7 and 6.0-8.3kgCm(-2) for desert grassland-cropland sites (sites 1 and 2) and meadow-cropland sites (sites 3 and 4), respectively, with significant differences between grasslands and croplands (P<0.05). However, the SOC densities in the underlying horizons did not significantly differ between the land uses. The SOC densities up to 100cm depth were much higher in the meadow-cropland sites than in the desert grassland-cropland sites, reaching approximately 16 and 6kgCm(-2), respectively. The SOC: total nitrogen (TN) ratios were approximately 10, with no significant difference among the soil horizons of grasslands and croplands. The conversion of grasslands to croplands induced a slight loss of SOC, with a range of from -4% to 22% for the 0-100cm soil depth over about a 35-year period, in the temperate Inner Mongolia. 相似文献