首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   12984篇
  免费   2581篇
  国内免费   1870篇
安全科学   986篇
废物处理   259篇
环保管理   2263篇
综合类   8589篇
基础理论   1943篇
环境理论   6篇
污染及防治   1073篇
评价与监测   1348篇
社会与环境   710篇
灾害及防治   258篇
  2024年   339篇
  2023年   459篇
  2022年   538篇
  2021年   619篇
  2020年   592篇
  2019年   532篇
  2018年   455篇
  2017年   591篇
  2016年   620篇
  2015年   649篇
  2014年   651篇
  2013年   898篇
  2012年   943篇
  2011年   979篇
  2010年   759篇
  2009年   725篇
  2008年   603篇
  2007年   816篇
  2006年   800篇
  2005年   587篇
  2004年   510篇
  2003年   549篇
  2002年   454篇
  2001年   422篇
  2000年   401篇
  1999年   298篇
  1998年   222篇
  1997年   204篇
  1996年   290篇
  1995年   163篇
  1994年   156篇
  1993年   107篇
  1992年   89篇
  1991年   94篇
  1990年   53篇
  1989年   25篇
  1988年   21篇
  1987年   33篇
  1986年   18篇
  1985年   12篇
  1984年   10篇
  1982年   20篇
  1981年   23篇
  1980年   17篇
  1979年   11篇
  1978年   17篇
  1977年   7篇
  1973年   10篇
  1972年   9篇
  1971年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Summary Seasonal rainerosivity is important in the structure and dynamics of Mediterranean ecosystems. The present paper contributes to the quantitative assessment of RUSLE's monthly erosion index in a data-scarce Mediterranean region. Therefore, a regionalized relationship for estimating monthly erosion index (EI30-month) from only three rainfall parameters has been obtained. Knowledge of the seasonal and annual distribution of erosivity index, permit soil and water conservationists to make improved designs for erosion control, water harvesting or small hydraulic structures. Although a few long data sets were used in the analysis, validation with established monthly erosivity index values from other Italian locations, suggest that the model presented (r2 = 0.973) is robust. It is recommended to monthly erosivity estimates when experimental data-scarce rainfall become available.  相似文献   
92.
Soil erosion associated with non-point source pollution is viewed as a process of land degradation in many terrestrial environments. Careful monitoring and assessment of land use variations with different temporal and spatial scales would reveal a fluctuating interface, punctuated by changes in rainfall and runoff, movement of people, perturbation from environmental disasters, and shifts in agricultural activities and cropping patterns. The use of multi-temporal remote sensing images in support of environmental modeling analysis in a geographic information system (GIS) environment leading to identification of a variety of long-term interactions between land, resources, and the built environment has been a highly promising approach in recent years. This paper started with a series of supervised land use classifications, using SPOT satellite imagery as a means, in the Kao-Ping River Basin, South Taiwan. Then, it was designed to differentiate the variations of eight land use patterns in the past decade, including orchard, farmland, sugarcane field, forest, grassland, barren, community, and water body. Final accuracy was confirmed based on interpretation of available aerial photographs and global positioning system (GPS) measurements. Finally, a numerical simulation model (General Watershed Loading Function, GWLF) was used to relate soil erosion to non-point source pollution impacts in the coupled land and river water systems. Research findings indicate that while the decadal increase in orchards poses a significant threat to water quality, the continual decrease in forested land exhibits a potential impact on water quality management. Non-point source pollution, contributing to part of the downstream water quality deterioration of the Kao-Ping River system in the last decade, has resulted in an irreversible impact on land integrity from a long-term perspective.  相似文献   
93.
This study examines sources of fecal coliform in Segment 2302 of the Rio Grande, located south of the International Falcon Reservoir in southern Texas. The watershed is unique because the contributing drainage areas lie in Texas and Mexico. Additionally, the watershed is mostly rural, with populated communities known as “colonias.” The colonias lack sewered systems and discharge sanitary water directly to the ground surface, thus posing an increased health hazard from coliform bacteria. Monitoring data confirm that Segment 2302 is not safe for contact recreation due to elevated fecal coliform levels. The goal of the study was to simulate the observed exceedences in Segment 2302 and evaluate potential strategies for their elimination. Fecal coliform contributions from ranching and colonia discharges were modeled using the Hydrologic Simulation Program‐Fortran (HSPF). Model results indicated that the regulatory 30‐day geometric mean fecal coliform concentration of 200 colony forming units (cfu) per 100 milliliters is exceeded approximately three times per year for a total of 30 days. Ongoing initiatives to improve wastewater facilities will reduce this to approximately once per year for 14 days. Best management practices will be necessary to reduce cattle access to streams and eliminate all exceedences. The developed model was limited by the relatively sparse flow and fecal coliform data.  相似文献   
94.
ABSTRACT: The goal of this research was to develop a methodology for modeling a bioinfiltration best management practice (BMP) built in a dormitory area on the campus of Villanova University in Pennsylvania. The objectives were to quantify the behavior of the BMP through the different seasons and rainfall events; better understand the physical processes governing the system's behavior; and develop design criteria. The BMP was constructed in 2001 by excavating within an existing traffic island, backfilling with a sand/soil mixture, and planting with salt tolerant grasses and shrubs native to the Atlantic shore. It receives runoff from the asphalt (0.26 hectare) and turf (0.27 hectare) surfaces of the watershed. Monitoring supported by the hydrologic model shows that the facility infiltrates a significant fraction of the annual precipitation, substantially reducing the delivery of nonpoint source pollution and erosive surges downstream. A hydrologic model was developed using HEC‐HMS to represent the site and the BMP using Green‐Ampt and kinematic wave methods. Instruments allow comparison of the modeled and measured water budget parameters. The model, incorporating seasonally variable parameters, predicts the volumes infiltrated and bypassed by the BMP, confirming the applicability of the selected methods for the analysis of bioinfiltration BMPs.  相似文献   
95.
霍雨  王腊春 《四川环境》2007,26(2):79-83,100
党的十六届五中全会提出了新农村建设的任务,江苏省也于近期举办了新农村建设专题研讨会。本文通过对现存相关指标体系的回顾分析,结合新农村建设“生产发展、生活宽裕、乡风文明、村容整洁、管理民主”的内涵,对江苏省新农村建设指标体系进行了初步探讨,并采用这一体系对大丰市南阳镇新农村建设实现程度进行了评价。结果表明,虽然江苏省农村发展水平已有明显提高,但仍需要进一步加强农村工作,努力达到新农村建设的目标。  相似文献   
96.
用清洁生产的理念防治农业污染的初步探讨   总被引:6,自引:0,他引:6  
农业发展面临的农业污染问题,已成为制约农业可持续发展的"瓶颈".农业污染问题已经成为影响农村经济发展,以及农村社会和谐发展的重要因素之一.在论述农业清洁生产涵义的基础上,探讨了农业清洁生产防治农业污染问题.以新疆绿洲农业为例,论述了农业污染现状及发展农业清洁生产的必要性,分析探讨了发展农业清洁生产存在的问题和障碍,并提出了对策和建议.  相似文献   
97.
通过对国内外石油行业的钻井环境污染源头控制技术的简单综述,分析了钻井工艺可采用小孔径钻井、连续软管工艺、新型固控设施等的技术特点,对选择合适的钻井液以及应用环保型钻井液来减轻污染方面进行了探讨。并展望了我国石油行业钻井环境污染源头控制技术的发展。  相似文献   
98.
目前,巢湖流域非点源污染问题突出。着眼于畜牧业和环境的协调发展,通过对研究区畜牧业生产的实地考查、分析和计算得出结论:畜牧业生产的快速发展、不合理和未加利用的畜牧粪便及畜牧业产品生产加工过程中产生的有机污物是巢湖流域非点源污染的重要原因,来源于畜牧业生产的非点源污染的氮就足以使巢湖水质劣于Ⅲ类标准。最后探讨了解决巢湖富营养化的控制措施。  相似文献   
99.
在学习并借鉴国内有关开发(园)区评价方法的基础上,选择经济总量、经济效率、基础设施和产业质量4方面共计12个指标评估开发区的发展状况,并在评估的基础上把安徽沿江15个开发区划分为重点拓展型开发区、优化提升类开发区、积极培育类开发区,最后针对不同类型的开发区分别提出发展建议。  相似文献   
100.
欠发达城市人居环境评价体系构建及应用   总被引:1,自引:0,他引:1  
在参阅国内城市人居环境评价指标体系研究的基础上,选择安徽省六安市为样区,提出了欠发达城市人居环境评价的原则、指标构成以及评价模式和方法。其中,指标体系共分为目标层、准则层、分类层和指标层4个层次,从居住建设、生态环境和社会经济三大系统构建了39个单项指标,依据六安市2005年的调查统计资料,对其人居环境的建设水平和满意度两方面进行了对比评价,验证结果科学可行,可为同类地区人居环境质量评价提供参考。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号