全文获取类型
收费全文 | 1843篇 |
免费 | 229篇 |
国内免费 | 158篇 |
专业分类
安全科学 | 490篇 |
废物处理 | 38篇 |
环保管理 | 355篇 |
综合类 | 728篇 |
基础理论 | 167篇 |
环境理论 | 3篇 |
污染及防治 | 154篇 |
评价与监测 | 71篇 |
社会与环境 | 87篇 |
灾害及防治 | 137篇 |
出版年
2024年 | 30篇 |
2023年 | 33篇 |
2022年 | 28篇 |
2021年 | 42篇 |
2020年 | 55篇 |
2019年 | 57篇 |
2018年 | 53篇 |
2017年 | 88篇 |
2016年 | 86篇 |
2015年 | 80篇 |
2014年 | 98篇 |
2013年 | 142篇 |
2012年 | 116篇 |
2011年 | 119篇 |
2010年 | 102篇 |
2009年 | 92篇 |
2008年 | 74篇 |
2007年 | 119篇 |
2006年 | 125篇 |
2005年 | 104篇 |
2004年 | 83篇 |
2003年 | 97篇 |
2002年 | 66篇 |
2001年 | 59篇 |
2000年 | 58篇 |
1999年 | 46篇 |
1998年 | 28篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有2230条查询结果,搜索用时 0 毫秒
881.
Animal movement studies have become ubiquitous in animal ecology for the estimation of space use and the analysis of movement behavior. In these studies, animal movement data are primarily collected at regular time intervals. We propose an irregular sampling design that could lead to greater efficiency and information gain in animal movement studies. Our novel sampling design, called lattice and random intermediate point (LARI), combines samples at regular and random time intervals. We compare the LARI sampling design to regular sampling designs in an example with common black carpenter ant location data, an example with guppy location data, and a simulation study of movement with a point of attraction. We modify a general stochastic differential equation model to allow for irregular time intervals and use this framework to compare sampling designs. When parameters are estimated reasonably well, regular sampling results in greater precision and accuracy in prediction of missing data. However, in each of the data and simulation examples explored in this paper, LARI sampling results in more accurate and precise parameter estimation and, thus, better prediction of missing data as well. This result suggests that researchers might gain greater insight into underlying animal movement processes by choosing LARI sampling over regular sampling. 相似文献
882.
随着经济社会快速发展,\"十四五\"时期城市水系统向协同治理、统筹推进转变。针对城市水系统运营管理普遍存在的体系不健全、标准不完善、运营质效低、经验难推广、数据难利用等问题,基于业务场景梳理了业务逻辑,基于数字化特点重构业务流程,探索了城市水系统智慧运营的实施路径,以系统思维构建了基于资产的城市水系统智慧运营管理体系,明确了核心要素和关键环节,研发环保业务和信息技术深度融合的智慧运营平台。通过构建\"信息采集-资产评估-分级维护-精细管理-监测预警-综合调度\"全过程运营管理流程,为实现城市水系统长效运营提供新思路,助力城市水系统标准化、精细化、智慧化运营,创造生态环境长效价值。 相似文献
883.
福州市浦东河水系是典型的城区黑臭水体,一直以来面临着外源污染严重、内源污染累积、生态基流匮乏、生态系统退化等问题。根据水系流域特征,统筹考虑水环境、水生态、水景观,采用以\"控源截污、内源治理、活水提质、生态修复\"为主的技术路线对浦东河水系进行了综合治理,经评估,沿线排口溢流水量、COD和NH3-N入河污染负荷分别削减了49.9%、77.0%和92.2%。根据工程实际运营情况,浦东河水系COD浓度长期稳定在30 mg/L以内,NH3-N浓度稳定在4 mg/L以内,治理效果良好。阐述了治理措施中关键要点的设计经验及注意事项,为类似城区黑臭水体治理工程实施提供借鉴参考。 相似文献
884.
首先推导了摩擦摆支座的水平和竖向恢复力公式,讨论了水平位移对竖向恢复刚度的影响;其次针对目前摩擦摆支座隔震设计、分析中存在的不足,重点讨论了基于规范设计反应谱迭代求解其等效线性化参数的实施流程和需要注意的问题;提出了一种综合隔震周期目标和摩擦力影响粗定等效曲率半径,并根据静轴力分布情况选择摩擦系数大小的摩擦摆支座隔震方案布设方法;最后结合实际工程案例,对比分析了橡胶支座隔震方案和摩擦摆支座隔震方案在不同组合工况下对支座内力、位移的隔震效果及其分布情况。结果表明:两种隔震方案均能达到降度设计的隔震目标,后者由于受三向耦合影响,各支座上的内力分布较前者的离散性更大;摩擦摆支座有可能出现受拉现象,应用中需注意设置抗拉构造措施;摩擦摆支座隔震方案中应重视空间扭转问题和控制支座抬升量。 相似文献
885.
Abhishek Das;Pradyut Kundu;Sunita Adhikari; 《环境质量管理》2024,33(4):73-90
This study was conducted to investigate the combined two-stage biological-treatment-process using consortium of bacteria and microalgae for removal of soluble chemical oxygen demand (SCOD), ammonium-nitrogen (NH4+-N), nitrate-nitrogen (NO3−-N), phosphorus (PO43−-P) from dairy wastewater in suspended-growth batch-reactor (SGBR). The study also investigated the removal of SCOD, NH4+-N, NO3−-N, PO43−-P under different process parameters, like initial SCOD, NH4+-N,NO3−-N, PO43−-P, MLSS, pH and react time using response surface methodology (RSM) with a five-factor-three-level Central Composite Design(CCD). The experimental results were analyzed by ANOVA and second-order polynomial mathematical-models were developed with high correlation efficiency for SCOD, NH4+-N removal, NO3−-N, PO43−-P removal using bacterial and microalgal-consortia respectively in SGBR. Individual and combined effects of process variables on responses were studied using three-dimensional response surface plots. Under the optimum conditions (initial SCOD, NH4+-N, pH, MLSS of 720 mg L−1, 55 mg L−1 as N, 7 and 1500 mg L−1, respectively and react time of 24 h) highest removal efficiencies of SCOD (98.61%) and NH4+-N (97.42%) were obtained using bacterial consortium and in second-phase using micro-algal consortium under optimum conditions highest removal efficiencies of nitrate nitrogen and phosphorus 98.64% and 90.53%, respectively. Optimization of process-parameters by RSM study is supposed to be helpful for the treatment of real life dairy wastewater in effluent treatment plants. 相似文献
886.
O. W. R. Lucas 《Journal of Environmental Planning and Management》1983,26(2):98-104
The value placed by the public on the nation's rural landscapes is emphasised by vociferous criticism of insensitive, large‐scale afforestation. As forestry causes massive changes in the landscape in the short term, with results that last for decades, the opportunity provided to improve and conserve should be positively grasped. There is evidence that concensus exists over a considerable part of landscape and design, and this paper explores some of the major factors in landscape design which are consistently important in forest landscapes. 相似文献
887.
本文主要简述了某军用装备型号设备在可靠性、保障性、维修性设计中注意的几个重要方面,并对设计工作中具体的可靠性要求展开了讨论。 相似文献
888.
Peggy A. Johnson Eric R. Brown 《Journal of the American Water Resources Association》2001,37(5):1225-1236
ABSTRACT: The designs of stream channel naturalization, rehabilitation, and restoration projects are inherently fraught with uncertainty. Although a systematic approach to design can be described, the likelihood of success or failure of the design is unknown due to uncertainties within the design and implementation process. In this paper, a method for incorporating uncertainty in decision‐making during the design phase is presented that uses a decision analysis method known as Failure Modes and Effects Analysis (FMEA). The approach is applied to a channel rehabilitation project in north‐central Pennsylvania. FMEA considers risk in terms of the likelihood of a component failure, the consequences of failure, and the level of difficulty required to detect failure. Ratings developed as part of the FMEA can provide justification for decision making in determining design components that require particular attention to prevent failure of the project and the appropriate compensating actions to be taken. 相似文献
889.
Eugene L. Peck John C. Schaake 《Journal of the American Water Resources Association》1990,26(1):87-99
ABSTRACT: The objective is to develop techniques to evaluate how changes in basic data networks can improve accuracy of water supply forecasts for mountainous areas. The approach used was to first quantify how additional data would improve our knowledge of winter precipitation, and second to estimate how this knowledge translates, quantitatively, into improvement in forecast accuracy. A software system called DATANET was developed to analyze each specific gage network alternative. This system sets up a fine mesh of grid points over the basin. The long-term winter mean precipitation at each grid point is estimated using a simple atmospheric model of the orographic precipitation process. The mean runoff at each grid point is computed from the long-term mean precipitation estimate. The basic runoff model is calibrated to produce the observed long-term runoff. The error analysis is accomplished by comparing the error in forecasts based on the best possible estimate of precipitation using all available data with the error in the forecasts based on the best possible estimate of winter precipitation using only the gaged data. Different data network configurations of gage sites can be compared in terms of forecast errors. 相似文献
890.
Nabil A. Zaghioul Abdel-Rahman M. Al-Shurbaji 《Journal of the American Water Resources Association》1990,26(4):563-575
ABSTRACT: A comprehensive study was conducted to implement the Storm Water Management Model (SWMM) for urban areas in Kuwait. The updated version of the model designed to run on an IBM Personal Computer and compatibles (PCSWMM3.2C) was utilized. The study revealed that urban runoff simulation in arid areas by the SWMM model is a powerful and efficient tool in designing drainage systems and as such, a viable replacement of the commonly used rational method. It was found that only the streets and paved areas that are hydraulically connected to the drainage system contribute to runoff. Fine and coarse discretization approaches were used in the study. The difference between the hydrographs simulated by the two approaches were relatively small. The performance of the existing drainage system and the accuracy of the design method used were tested using a 25-year storm. The result of the simulation revealed that the storm sewers were oversized by factors ranging from 1.2 to 3.6. The SWMM model was used to estimate the storm water runoff volume collected from all urbanized areas in Kuwait City. The annual expected harvested runoff water was found to be significant; however, the quality of runoff water needs to be assessed before a decision is made on its reuse. 相似文献