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101.
Eugene B. Welch 《Journal of the American Water Resources Association》1981,17(4):558-564
ABSTRACT: Dilution/flushing has been documented as an effective restoration technique to restore eutrophic Moses and Green Lakes in Washington State. The dilution water added to both lakes was low in nitrogen and phosphorus content relative to the lake or normal input water. Consequently, lake nutrient content dropped predictably. Dilution or flushing rates were about ten times normal during the spring-summer periods in Moses Lake and three times normal on an annual basis in Green Lake. Improvement in quality (nutrients, algae, and transparency) was on the order of 50 percent in Moses Lake and even greater in Green Lake. The facilities for supplying dilution water were largely in place for the cited lakes; thus, costs for water transport were minimal. Available facilities, and therefore, costs, for water transport would usually vary greatly, however. Achieving maximum benefit from the technique may be more limited by availability of low nutrient water rather than facilities costs. Quality improvement may occur from physical effects of algal cell washout and water column instability if only high nutrient water is available. 相似文献
102.
The effectiveness of various forms of caution signs was evaluated using saccadic eye movements and reaction time as the dependent variables. Both dependent measures show that caution signs requiring specific positive actions are processed more slowly and less efficiently than signs requiring avoidance behaviors. Additionally, the data show that changing the order of the “consequences” and “instructions” elements of the caution signs did not influence the number of saccades, the speed, or accuracy of interpretation. The research shows that saccadic eye movement may be an effective method for evaluating the design of caution signs. 相似文献
103.
Lankeswara H. Wijayaratne Eugene Golub 《Journal of the American Water Resources Association》1991,27(3):387-395
ABSTRACT: Previous studies on multiyear droughts have often been limited to the analysis of historic annual flow series. A major disadvantage in this approach can be described as the unavailability of long historic flow records needed to obtain a significant number of drought events for the analysis. To overcome this difficulty, the present study proposes to use synthetically generated annual flow series. A methodology is presented to model annual flows based on an analysis of the harmonic and stochastic properties of the observed flows. Once the model is determined, it can be utilized to generate a flow series of desired length so as to include many hydrologic cycles within the process. The key parameter for a successful drought study is the truncation level used to distinguish low flows from high flows. In this paper, a concept of selecting the truncation level is also presented. The drought simulation procedure is illustrated by a case study of the Pequest watershed in New Jersey. For the above watershed, multiyear droughts were derived from both historic and generated flow series. Three important drought parameters, namely, the duration, severity, and magnitude, were determined for each drought event, and their probability distributions were studied. It was found that gamma and log normal probaility functions produce the best fit for the duration and severity, respectively. The derived probability curves from generated flows can be reliably used to predict the longest drought duration and the largest drought severity within a given return period. 相似文献
104.
Frederick W. Bond Donald L. Chery Eugene S. Simpson 《Journal of the American Water Resources Association》1979,15(6):1640-1652
ABSTRACT: Recent developments in the numerical solution of the governing partial differential equations for overland and channel flow should make possible physically based models which predict runoff from ungaged streams. However, these models, which represent the watershed by sets of intersecting planes, are complex and require much computer time. Parametric models exist that have the advantage of being relatively simple, and once calibrated are inexpensive to use and require limited data input. In this study, a procedure was developed for calibrating a parametric model against a physically based model, utilizing base areas of one acre and one square mile, with the expectation that base areas can be combined to model real watersheds. Simulation experiments with the physically based model showed that, for the one-acre base area, the dominant parameter (cell storage ratio, K) related to the slope and friction of the planes, whereas for one square-mile areas, the dominant parameters (K plus a lag factor, L) relate to channel properties. These parameters decreased exponentially as rainfall intensity increased. 相似文献
105.
106.
Monica G. Turner Eugene P. Odum Robert Costanza Thomas M. Springer 《Environmental management》1988,12(2):209-217
Natural landscapes produce goods and services, such as fish, wildlife, recreation, climate control, that are not adequately incorporated in their market values. Contingent Valuation (CV) and Energy Analysis (EA) approaches were used to estimate the nonmarket value of forests in Georgia. Both methods yielded similar estimates of approximately $200 ha–1, which was 31% of the total market and nonmarket value of forests. Energy analysis was also used to estimate the nonmarket value of the major land uses in Georgia. Relative contributions of nonmarket value to total value ranged from 0.1% for urban areas to approximately 100% for wetlands. For the state as a whole, nonmarket production of natural and developed ecosystems was estimated at $2.6 billion. This value is comparable to annual marketed agricultural ($2.8 billion) and timber ($4.5 billion) production, both very important industries in Georgia. Changing land use patterns in Georgia and elsewhere are likely to be accompanied by shifts in the relative importances of market and non-market values. 相似文献
107.
Louisiana's coastal wetlands represent about 41% of the nation's total and are extensively managed for fish, fur, and waterfowl. Marsh management plans (MMPs) are currently used to avoid potential user conflicts and are believed to be a best management practice for specific management goals. In this article, we define MMPs and examine their variety, history, impacts, and future.A MMP is an organized written plan submitted to state and federal permitting agencies for approval and whose purpose is to regulate wetland habitat quantity and quality (control land loss and enhance productivity). MMPs are usually implemented by making structural modifications in the marsh, primarily by using a variety of water control structures in levees to impound or semi-impound managed areas. It appears that MMPs using impoundments are only marginally successful in achieving and often contradict management goals. Although 20% of coastal Louisiana may be in MMPs by the year 2000, conflict resolution of public and private goals is compromised by a surfeit of opinion and dearth of data and experience. Based on interpretation of these results, we believe the next phase of management should include scientific studies of actual impacts, utilization of post-construction monitoring data, inventory of existing MMPs, development of new techniques, and determination of cumulative impacts. 相似文献
108.
Cadle SH Croes BE Minassian F Natarajan M Tierney EJ Lawson DR 《Journal of the Air & Waste Management Association (1995)》2004,54(1):8-23
The Coordinating Research Council held its thirteenth Vehicle Emissions Workshop in April 2003, when results of the most recent on-road vehicle emissions research were presented. Ongoing work from researchers who are engaged in improving understanding of the contribution of mobile sources to ambient air quality and emission inventories is summarized here. Participants in the workshop discussed efforts to improve mobile source emission models, the role of on-board diagnostic systems in inspection and maintenance programs, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as topics for future research. 相似文献
109.
The inorganic ion concentrations of soils and streams in the three locations (Yorla, Zaakpon and Goi) in Ogoniland,Nigeria affected by crude oil spillage were investigated. In general, inorganic ion concentrations of polluted soilsand streams varied significantly (p = 0.05) from those of unpolluted soils and streams. Anions such as nitrate (NO
3
-
), sulphate (SO
4
2-
) and chloride(Cl-) showed significantly (p = 0.05) higher values inthe polluted soils and steams than in the unpolluted controls. The phosphate (PO
4
3-
) values were lowerin the polluted soils and streams than in the unpolluted controls.PO
4
3-
, NO
3
-
, SO
4
2-
and Cl- concentrations were generally significantly (p = 0.05) higher in soils and streams from Yorla, Zaakpon and their control than in Goi North, Goi South and Goi control.Exchangeable cations and trace metal concentrations weresignificantly (p = 0.05) higher in the polluted soils andstreams than in the unpolluted controls. Yorla and Zaakponpolluted soils and streams had higher concentrations of theexchangeable cations and trace metals compared to valuesfrom Goi, except for Na. Results also showed significantlyhigher values of heavy metals (Pb, Cd, Cr and Ni) in the polluted soils compared to their controls, and values werealso significantly (p = 0.05) higher in Yorla, Zaakpon andtheir control compared to Goi North, Goi South and Goicontrol. Values obtained in polluted streams were higherthan in the unpolluted though not significant at the 5%level (p = 0.05). The anionic and cationic concentrationsof Yorla and Zaakpon soils and streams were generally higherthan those of Goi, indicating that Yorla and Zaakpon areaswere more polluted than Goi.Although the concentrations of most of the anions andcations analysed in the polluted soils and streams werewithin the World Health Organisation's permissible valuesfor the protection of humans and environment, the streams ofYorla, Zaakpon and Goi are in general being polluted withinorganic ions. This may make these soils and streamsunacceptable for domestic and industrial uses if not treated,and soils (farmlands) may also become unsuitable for agricultural purposes. 相似文献
110.
Cadle SH Belian TC Black KN Minassian F Natarajan M Tierney EJ Lawson DR 《Journal of the Air & Waste Management Association (1995)》2005,55(2):130-146
The Coordinating Research Council held its 14th Vehicle Emissions Workshop in March 2004, where results of the most recent on-road vehicle emissions research were presented. We summarize ongoing work from researchers who are engaged in improving our understanding of the contribution of mobile sources to ambient air quality and emission inventories. Participants in the workshop discussed efforts to improve mobile source emission models, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as topics for future research. 相似文献