全文获取类型
收费全文 | 1899篇 |
免费 | 51篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 129篇 |
废物处理 | 82篇 |
环保管理 | 445篇 |
综合类 | 209篇 |
基础理论 | 490篇 |
环境理论 | 2篇 |
污染及防治 | 385篇 |
评价与监测 | 124篇 |
社会与环境 | 72篇 |
灾害及防治 | 32篇 |
出版年
2023年 | 14篇 |
2022年 | 24篇 |
2021年 | 22篇 |
2020年 | 26篇 |
2019年 | 24篇 |
2018年 | 47篇 |
2017年 | 61篇 |
2016年 | 67篇 |
2015年 | 64篇 |
2014年 | 60篇 |
2013年 | 131篇 |
2012年 | 86篇 |
2011年 | 155篇 |
2010年 | 100篇 |
2009年 | 88篇 |
2008年 | 114篇 |
2007年 | 125篇 |
2006年 | 120篇 |
2005年 | 72篇 |
2004年 | 71篇 |
2003年 | 71篇 |
2002年 | 59篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 25篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1969年 | 3篇 |
1937年 | 2篇 |
1936年 | 2篇 |
1935年 | 3篇 |
1926年 | 2篇 |
排序方式: 共有1970条查询结果,搜索用时 187 毫秒
531.
A numerical simulation model of pesticide runoff through vegetative filer strips (PRVFS) was developed as a tool for investigating the effects of pesticide transport mechanisms on VFS design in dormant-sprayed orchard. The PRVFS model was developed applying existing theories such as kinematic wave theory and mixing zone theory for pesticide transport in the bare soil area. For VFS area, the model performs flow routing by simple mass accounting in sequential segments and the pesticide mass balance by considering pesticide washoff and adsorption processes on the leaf, vegetative litter, root zone and soil. Model sensitivity analysis indicated that pesticide transfer from surface soil to overland flow and pesticide washoff from the VFS were important mechanisms affecting diazinon transport. The VFS cover ratio and rainfall intensity can be important design parameters for controlling diazinon runoff using inter-row VFS in orchard. The PRVFS model was validated using micro-ecosystem simulation of diazinon transport for 0, 50 and 100% VFS cover conditions. The PRVFS model is shown to be a beneficial tool for evaluating and analyzing possible best management practices for controlling offsite runoff of dormant-sprayed diazinon in orchards during the rainy season. 相似文献
532.
Arbaugh M Bytnerowicz A Grulke N Fenn M Poth M Temple P Miller P 《Environment international》2003,29(2-3):401-406
Toxic effects of photochemical smog on ponderosa and Jeffrey pines in the San Bernardino Mountains were discovered in the 1950s. It was revealed that ozone is the main cause of foliar injury manifested as chlorotic mottle and premature needle senescence. Various morphological, physiological and biochemical alterations in the affected plants have been reported over a period of about 40 years of multidisciplinary research. Recently, the focus of research has shifted from studying the effects of ozone to multiple pollutant effects. Recent studies have indicated that the combination of ozone and nitrogen may alter biomass allocation in pines towards that of deciduous trees, accelerate litter accumulation, and increase carbon sequestration rates in heavily polluted forests. Further study of the effects of multiple pollutants, and their long-term consequences on the mixed conifer ecosystem, cannot be adequately done using the original San Bernardino Mountains Air Pollution Gradient network. To correct deficiencies in the design, the new site network is being configured for long-term studies on multiple air pollutant concentrations and deposition, physiological and biochemical changes in trees, growth and composition of over-story species, biogeochemical cycling including carbon cycling and sequestration, water quality, and biodiversity of forest ecosystems. Eleven sites have been re-established. A comparison of 1974 stand composition with data from 2000 stand composition indicate that significant changes in species composition have occurred at some sites with less change at other sites. Moist, high-pollution sites have experienced the greatest amount of forest change, while dryer low-pollution sites have experienced the least amount of stand change. In general, ponderosa pine had the lowest basal area increases and the highest mortality across the San Bernardino Mountains. 相似文献
533.
Gerland S Lind B Dowdall M Karcher M Kolstad AK 《Journal of environmental radioactivity》2003,69(1-2):119-127
99Tc levels were measured in seawater samples collected between 2000 and 2002 in the West Spitsbergen Current (WSC) and along the western coast of Svalbard or Spitzbergen and compared with available oceanographic 3-D modelling results for the late 1990s. Additional data from related regions are also presented in order to support the data interpretation. The seawater in the Arctic fjord Kongsfjorden on the western coast of Svalbard is influenced by the WSC, as shown by the 99Tc levels in surface water. By means of the WSC, 99Tc reaches the Eastern Fram Strait, where one branch of the WSC turns west into the East Greenland Current (EGC), and another branch continues northwards into the Arctic Ocean. Surface seawater collected in the central part of the WSC during a cruise on board the R/V "Polarstern" in the summer of 2000, showed higher levels of (99)Tc than samples measured in Kongsfjorden in the spring of 2000. However, all levels measured in surface water are of the same order of magnitude. Data from sampling of deeper water in the WSC and EGC provide information pertaining to the lateral distribution of 99Tc. In all vertical profiling surveys (conducted in spring and summer), the highest levels of 99Tc were found in surface water. Comparison with oceanographic 3-D modelling indicates both significant seasonal variations in the lateral stratification of the WSC and variations with depth over shorter vertical distances. This information can be applied in sampling strategies, environmental monitoring, long-range transport of pollutants and physical oceanography. 相似文献
534.
The US Clean Water Act and habitat replacement: evaluation of mitigation sites in Orange County,California, USA 总被引:2,自引:2,他引:0
Both permit requirements and ecological assessments have been used to evaluate mitigation success. This analysis combines
these two approaches to evaluate mitigation required under Section 404 of the United States Clean Water Act (CWA) and Section
10 of the Rivers and Harbors Act, which allow developers to provide compensatory mitigation for unavoidable impacts to wetlands.
This study reviewed permit files and conducted field assessments of mitigation sites to evaluate the effectiveness of mitigation
required by the US Army Corps of Engineers for all permits issued in Orange County, California from 1979 through 1993. The
535 permit actions approved during this period allowed 157 ha of impacts. Mitigation was required on 70 of these actions,
with 152 ha of enhanced, restored, and created habitat required for 136 ha of impacts. In 15 permit actions, no mitigation
project was constructed, but in only two cases was the originally permitted project built; the two cases resulted in an unmitigated
loss of 1.6 ha. Of the remaining 55 sites, 55% were successful at meeting the permit conditions while 11% failed to do so.
Based on a qualitative assessment of habitat quality, only 16% of the sites could be considered successful and 26% were considered
failures. Thus, of the 126 ha of habitat lost due to the 55 projects, only 26 ha of mitigation was considered successful.
The low success rate was not due to poor enforcement, although nearly half of the projects did not comply with all permit
conditions. Mitigation success could best be improved by requiring mitigation plans to have performance standards based on
habitat functions. 相似文献
535.
Mark A. Hooker Wendy E. Alexander 《Journal of the American Water Resources Association》1998,34(3):497-505
ABSTRACT: This paper computes estimates of the demand for surface irrigation water directly from disaggregated profit functions for fields in the San Joaquin Valley of California. It finds that treating delivered surface water and pumped ground water as separate, imperfectly substitutable inputs to production matters a great deal. We find substantial ranges of inelastic demand for delivered water, and thresholds across which demand then becomes highly elastic. The results imply that moves toward freer water markets could lead to large quantities reallocated from agriculture to urban uses in the Western U.S., but would require large price increases and would induce extensive ground water mining and major changes in cropping patterns. While these results are dependent on our particular model and simplifying assumptions, evidence exists that they may be robust. 相似文献
536.
Mark Uguccioni Chris Zeiss 《Journal of the American Water Resources Association》1997,33(6):1265-1278
ABSTRACT: Existing leachate prediction models over- or underestimate leachate generation by up to three orders of magnitude. Practical experiments show that channeled flow in waste leads to rapid discharge of large leachate volumes and heterogeneous moisture distributions. In order to more accurately predict leachate generation, leachate models must be improved. To predict moisture movement through waste, the one-domain water balance model HELP, and two-domain PREFLO, are tested. Experimental waste and leachate flow values are compared with model predictions. When calibrated with experimental parameters, the HELP model yields reasonable predictions of cumulative leachate flow and PREFLO provides estimates of breakthrough time. In the short term, field capacity has to be reduced to 0.12 and effective storage and hydraulic conductivity of the waste must be increased to 0.2 and 2.2 cm/s respectively. In the long term, a new modeling approach must be developed to adequately describe the moisture movement mechanisms. 相似文献
537.
Color and chemical oxygen demand (COD) in bleach plant effluents are of concern. Acidified flyash can effectively remove both color and COD from caustic bleach plant effluents. Equally effective, but quicker and easier, is to acidify the effluent to approximately pH 1 and use untreated flyash. Based on maximum color removal, the required contact time is short, about 10 min, and the optimum ash dosage is that amount which raises the pH of the final effluent to about 5. Sufficient color removal is obtained to easily meet Maine's color regulations. Preliminary tests on samples of deionized water spiked with two arochlors of PCB showed high removal efficiency.The major cost of implementing and operating the cleanup procedure will be the cost of the required acid. This might be minimized by using some of the acidic (chlorine) effluent to lower the pH of the caustic effluent. This will, however, lead to less color reduction, and an unknown effect on the COD. 相似文献
538.
Mark R. Lehto Associate Professor Dwayne S. James Deputy Director James P. Foley Visiting Professor 《Journal of Safety Research》1994,25(4):197-213
This 2-year longitudinal study of 302 high school students in the state of Indiana examined attitudes toward the use of alcohol in 25 potentially hazardous settings, varying from riding in a car, to swimming, to simply drinking at home. Student ratings indicated that they were capable of rationally evaluating alcohol-related risks. Principal components factor analysis identified three factors underlying student responses: propensity/desirability of the behavior, choice/control of the risk, and fear/consequences/likelihood of the risk. Each of these factors was comparable to factors found to be important in past studies of adult risk perception. The finding that self-reported behavioral propensity and desirability were weakly correlated with the measures of perceived risk is of particular interest. Attempts to reduce the use of alcohol by adolescents have traditionally focused on risk awareness. The implication of this study is that intervention programs might be more successful if they focused on modifying perceived value. 相似文献
539.
Louis A. Heifrich Mark Zimmerman Diana L. Weigmann 《Journal of the American Water Resources Association》1995,31(2):307-316
ABSTRACT: Filtering efficiency of the fathead minnow (Pimephales promelas), gizzard shad (Dorosoma cepedianum), carp (Cyprinus carpio), and a freshwater mussel (Elliptio coinpianata) was measured in field and laboratory trials to assess the ability of each species to control phytoplankton and suspended solid densities. All fish species tested were ineffective filterers and generally increased, rather than suppressed, algal and suspended solid concentrations. Filtering efficiencies of fish varied between -354 and 84 percent, depending on the size, shape, abundance, palatability, composition, and resistance to digestion of the particles. Because of poor filtering abilities, unpredictable feeding habits, and sensitivity to stress, the fish species examined are not effective biological controls in waste lagoons. In contrast, the freshwater mussel Elliptio was a highly effective control organism, averaging 66 percent filtering efficiency over a wide size range of algal and suspended particles. Filtration efficiency was positively correlated with mussel density. Elliptio was efficient at filtering small particles, which are particularly difficult to remove. Mean filtration rates ranged from 53 to 134 ml/mussel/h depending on the algal species consumed and algal densities (range 50–180,000 cells/ml) and 3 mg/L/mussel/h on suspended solids (range 14 to 112 mg/L). Water clarification was facilitated by both direct consumption and pseudofeces deposition. Elliptio and probably other mussel species can effectively control algae and suspended solids in wastewater lagoons and eutrophic lakes, if environmental conditions, especially dissolved oxygen levels, are suitable (>5 mg/L) for their survival. 相似文献
540.
Mark T. Anderson Clifford L. Hawkes 《Journal of the American Water Resources Association》1985,21(3):499-505
The water from 34 strip mine and 9 livestock water impoundments on the Northern Great Plains was analyzed. In all areas the water was classified as slightly brackish or saline. The dominant ion sequence for the study ponds was Na>Ca>Mg>K and SO4HCO3CO3Cl, which differs from most freshwater by the transposition of Na and SO4. Even though mean concentrations of total filterable residue were consistently greater in strip mine ponds, statistically significant differences were not found at the p ≤ 0.05 level between strip ponds and livestock ponds. The macronutrients of nitrogen and phosphorus found in the ponds were neither limiting to primary productivity nor excessive for fresh water. Many ponds contain turbid water. Turbidity restricts light penetration and limits photosynthesis besides making the ponds visually unattractive. The source of water for the pond, whether surface runoff or groundwater, seems to have important bearing on turbidity. The most appropriate use of these strip mine ponds is for waterfowl, warm-water fisheries, and other wildlife associated with prairie wetlands. However, even these uses are jeopardized by detrimental concentrations of trace elements in the water (Anderson and Hawkes, 1984). 相似文献