全文获取类型
收费全文 | 3170篇 |
免费 | 97篇 |
国内免费 | 258篇 |
专业分类
安全科学 | 143篇 |
废物处理 | 22篇 |
环保管理 | 751篇 |
综合类 | 1360篇 |
基础理论 | 224篇 |
污染及防治 | 291篇 |
评价与监测 | 587篇 |
社会与环境 | 112篇 |
灾害及防治 | 35篇 |
出版年
2024年 | 6篇 |
2023年 | 42篇 |
2022年 | 52篇 |
2021年 | 72篇 |
2020年 | 94篇 |
2019年 | 52篇 |
2018年 | 54篇 |
2017年 | 91篇 |
2016年 | 112篇 |
2015年 | 131篇 |
2014年 | 151篇 |
2013年 | 160篇 |
2012年 | 133篇 |
2011年 | 250篇 |
2010年 | 91篇 |
2009年 | 244篇 |
2008年 | 200篇 |
2007年 | 207篇 |
2006年 | 157篇 |
2005年 | 130篇 |
2004年 | 119篇 |
2003年 | 119篇 |
2002年 | 100篇 |
2001年 | 92篇 |
2000年 | 85篇 |
1999年 | 82篇 |
1998年 | 78篇 |
1997年 | 63篇 |
1996年 | 44篇 |
1995年 | 54篇 |
1994年 | 65篇 |
1993年 | 40篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1969年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有3525条查询结果,搜索用时 187 毫秒
231.
In many European countries, accommodating water has become the dominant paradigm in river management. In the Netherlands, extensive river restoration projects are being implemented, many of which draw serious opposition from the public. To investigate the causes of such opposition, a comprehensive study of public attitudes towards river restoration was conducted in three floodplains, both before and after river restoration. The study combined quantitative questionnaires (N = 562) with open interviews (N = 29). This paper describes how local residents perceive the effects of river restoration on landscape quality and how residents and protest groups use landscape quality in combination with other arguments to strategically frame river management policies. Results show that measurement of the perceived outcomes of nature restoration needs to be complemented by a more dynamic type of research, focusing on the social processes of the framing of restoration plans. Theoretically, the paper aims to contribute to the development of a rigorous research strategy to study framing processes in environmental management, using a mixed-methods approach. 相似文献
232.
Benjamin M. Jones Christopher D. Arp Kenneth M. Hinkel Richard A. Beck Joel A. Schmutz Barry Winston 《Environmental management》2009,43(6):1071-1084
Lakes are dominant landforms in the National Petroleum Reserve Alaska (NPRA) as well as important social and ecological resources.
Of recent importance is the management of these freshwater ecosystems because lakes deeper than maximum ice thickness provide
an important and often sole source of liquid water for aquatic biota, villages, and industry during winter. To better understand
seasonal and annual hydrodynamics in the context of lake morphometry, we analyzed lakes in two adjacent areas where winter
water use is expected to increase in the near future because of industrial expansion. Landsat Thematic Mapper and Enhanced
Thematic Mapper Plus imagery acquired between 1985 and 2007 were analyzed and compared with climate data to understand interannual
variability. Measured changes in lake area extent varied by 0.6% and were significantly correlated to total precipitation
in the preceding 12 months (p < 0.05). Using this relation, the modeled lake area extent from 1985 to 2007 showed no long-term trends. In addition, high-resolution
aerial photography, bathymetric surveys, water-level monitoring, and lake-ice thickness measurements and growth models were
used to better understand seasonal hydrodynamics, surface area-to-volume relations, winter water availability, and more permanent
changes related to geomorphic change. Together, these results describe how lakes vary seasonally and annually in two critical
areas of the NPRA and provide simple models to help better predict variation in lake-water supply. Our findings suggest that
both overestimation and underestimation of actual available winter water volume may occur regularly, and this understanding
may help better inform management strategies as future resource use expands in the NPRA. 相似文献
233.
An Interval-Parameter Waste-Load-Allocation Model for River Water Quality Management Under Uncertainty 总被引:1,自引:0,他引:1
A simulation-based interval quadratic waste load allocation (IQWLA) model was developed for supporting river water quality
management. A multi-segment simulation model was developed to generate water-quality transformation matrices and vectors under
steady-state river flow conditions. The established matrices and vectors were then used to establish the water-quality constraints
that were included in a water quality management model. Uncertainties associated with water quality parameters, cost functions,
and environmental guidelines were described as intervals. The cost functions of wastewater treatment units were expressed
in quadratic forms. A water-quality planning problem in the Changsha section of Xiangjiang River in China was used as a study
case to demonstrate applicability of the proposed method. The study results demonstrated that IQWLA model could effectively
communicate the interval-format uncertainties into optimization process, and generate inexact solutions that contain a spectrum
of potential wastewater treatment options. Decision alternatives can be generated by adjusting different combinations of the
decision variables within their solution intervals. The results are valuable for supporting local decision makers in generating
cost-effective water quality management strategies. 相似文献
234.
The Effect of Water Harvesting Techniques on Runoff,Sedimentation, and Soil Properties 总被引:1,自引:0,他引:1
This study addressed the hydrological processes of runoff and sedimentation, soil moisture content, and properties under the
effect of different water harvesting techniques (treatments). The study was conducted at three sites, representing environmental
condition gradients, located in the southern part of the West Bank. For each treatment, the study evaluated soil chemical
and physical properties, soil moisture at 30 cm depth, surface runoff and sedimentation at each site. Results showed that
runoff is reduced by 65–85% and sedimentation by 58–69% in stone terraces and semi-circle bunds compared to the control at
the semi-humid site. In addition, stone terraces and contour ridges significantly reduced the amount of total runoff by 80%
and 73%, respectively, at the arid site. Soil moisture content was significantly increased by water harvesting techniques
compared to the control in all treatments at the three study sites. In addition, the difference between the control and the
water harvesting structures were higher in the arid and semi-arid areas than in the semi-humid area. Soil and water conservation,
via utilization of water harvesting structures, is an effective principle for reducing the negative impact of high runoff
intensity and subsequently increasing soil moisture storage from rainfall. Jessour systems in the valley and stone terraces
were effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the
amount of supplemental irrigation required for growing fruit trees. 相似文献
235.
The fate and transport processes of a toxic chemical such as atrazine, an herbicide, in a reservoir are significantly influenced
by hydrodynamic regimes of the reservoir. The two-dimensional (2D) laterally-integrated hydrodynamics and mass transport model,
CE-QUAL-W2, was enhanced by incorporating a submodel for toxic contaminants and applied to Saylorville Reservoir, Iowa. The
submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions
of a toxic chemical. The simulation results from the enhanced 2D reservoir model were validated by measured temperatures and
atrazine concentrations in the reservoir. Although a strong thermal stratification was not identified from both observed and
predicted water temperatures, the spatial variation of atrazine concentrations was largely affected by seasonal flow circulation
patterns in the reservoir. In particular, the results showed the effect of flow circulation on spatial distribution of atrazine
during summer months as the river flow formed an underflow within the reservoir and resulted in greater concentrations near
the surface of the reservoir. Atrazine concentrations in the reservoir peaked around the end of May and early June. A good
agreement between predicted and observed times and magnitudes of peak concentrations was obtained. The use of time-variable
decay rates of atrazine led to more accurate prediction of atrazine concentrations, while the use of a constant half-life
(60 days) over the entire period resulted in a 40% overestimation of peak concentrations. The results provide a better understanding
of the fate and transport of atrazine in the reservoir and information useful in the development of reservoir operation strategies
with respect to timing, amount, and depth of withdrawal. 相似文献
236.
237.
238.
Bing Du Xiaoyi Ji R. Daren Harmel Larry M. Hauck 《Journal of the American Water Resources Association》2009,45(2):475-484
Abstract: The Soil and Water Assessment Tool (SWAT) model was evaluated for estimation of continuous daily flow based on limited flow measurements in the Upper Oyster Creek (UOC) watershed. SWAT was calibrated against limited measured flow data and then validated. The Nash‐Sutcliffe model Efficiency (NSE) and mean relative error values of daily flow estimations were 0.66 and 15% for calibration, and 0.56 and 4% for validation, respectively. Also, further evaluation of the model’s estimation of flow at multiple locations was conducted with parametric paired t‐test and nonparametric sign test at a 95% confidence level. Among the five main stem stations, four stations were statistically shown to have good agreement between predicted and measured flows. SWAT underestimated the flow of the fifth main stem station possibly because of the existence of complex flood control measures near to the station. SWAT estimated the daily flow at one tributary station well, but with relatively large errors for the other two tributaries. The spatial pattern of predicted flows matched the measured ones well. Overall, it was concluded from the graphical comparisons and statistical analyses of the model results that SWAT was capable of reproducing continuous daily flows based on limited flow data as is the case in the UOC watershed. 相似文献
239.
Kristin Floress Jean C. Mangun Mae A. Davenport Karl W.J. Williard 《Journal of the American Water Resources Association》2009,45(6):1352-1360
Floress, Kristin, Jean C. Mangun, Mae A. Davenport, and Karl W.J. Williard, 2009. Constraints to Watershed Planning: Group Structure and Process. Journal of the American Water Resources Association (JAWRA) 45(6):1352‐1360. Abstract: The roles that agencies and other partners play in collaborative watershed management are not always clearly identified. Key factors contributing to group‐level outcomes in watershed groups include both structural and procedural elements. Structural elements include membership systems, project partners, and funding, while procedural elements include leadership, shared vision, and mission development. The current research reports on a case study conducted with a Midwestern watershed group that received Clean Water Act Section 319 funds to undertake a watershed planning process. Data come from focus groups, interviews, public comments, and meeting observation, and were analyzed using grounded theory. Findings of this study indicate that homogenous skill set, discord over group and partner roles, and failed problem identification contributed to the organizational inertia experienced by the watershed group. Implications of this research for groups receiving 319 funds are provided. 相似文献
240.
自动喷水灭火系统喷水强度概率分布特性及其控火性能研究 总被引:1,自引:0,他引:1
喷水强度是体现自动喷水灭火系统控火能力的重要参数,具有不均匀性和不确定性.传统的喷水强度设计主要考虑喷头的流量和保护面积,没有考虑其分布特性,对系统控火性能的影响.因此本文将喷水强度分布特性引入自动喷水灭火系统的控火性能研究.以公称口径为15 mm的传统下垂型玻璃球洒水喷头的喷水强度分布实验为基础,建立了包含径向距离和喷头工作压力等参数的喷水强度分布模型,采用蒙特卡罗方法获得了喷水强度的概率分布特性.参照不同危险等级场控火所需的喷水强度参数和不同喷头开启个数下的有效控火百分比,分析了喷水强度概率分布特性对控火性能的影响.研究结果表明,喷水强度概率分布特性对控火性能有重要影响,随径向距离的增加,喷水强度出现较小值的概率增大,控火性能下降,在某些危险较大的场所不能达到控火作用.对于同一危险等级场所,控火性能随着喷头安装间距减小而增强.研究方法可为合理评估喷头适用范围、优化喷头布置提供参考. 相似文献