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   22342篇
  免费   1975篇
  国内免费   4506篇
安全科学   2106篇
废物处理   412篇
环保管理   5133篇
综合类   12532篇
基础理论   2373篇
环境理论   1篇
污染及防治   1624篇
评价与监测   2895篇
社会与环境   1193篇
灾害及防治   554篇
  2024年   62篇
  2023年   394篇
  2022年   569篇
  2021年   617篇
  2020年   713篇
  2019年   603篇
  2018年   530篇
  2017年   778篇
  2016年   993篇
  2015年   1130篇
  2014年   1222篇
  2013年   1647篇
  2012年   1769篇
  2011年   1874篇
  2010年   1331篇
  2009年   1332篇
  2008年   987篇
  2007年   1576篇
  2006年   1443篇
  2005年   1170篇
  2004年   967篇
  2003年   1018篇
  2002年   848篇
  2001年   702篇
  2000年   659篇
  1999年   535篇
  1998年   387篇
  1997年   384篇
  1996年   334篇
  1995年   277篇
  1994年   249篇
  1993年   227篇
  1992年   157篇
  1991年   135篇
  1990年   100篇
  1989年   96篇
  1988年   80篇
  1987年   80篇
  1986年   52篇
  1984年   48篇
  1983年   59篇
  1982年   59篇
  1981年   77篇
  1980年   83篇
  1979年   77篇
  1978年   53篇
  1977年   50篇
  1973年   45篇
  1972年   41篇
  1971年   60篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
南昌市一次降水自动监测结果的综合分析   总被引:1,自引:0,他引:1  
利用降水自动监测仪和空气自动监测系统的同步监测结果,分析了一次34 5mm连续降水中全过程的pH、EC和同期SO2、PM10、NO2的变化情况。降水中pH值为7 23~4 08、EC为488 8~7 6μS cm,pH、EC在降水初期变化较大。pH与EC、SO2呈现负相关趋势,降水过程中PM10、NO2基本保持较低水平,SO2变化较大。  相似文献   
142.
A sub-surface desert water harvester was constructed in the sagebrush steppe habitat of south-central Idaho, U.S.A. The desert water harvester utilizes a buried micro-catchment and three buried storage tanks to augment water for wildlife during the dry season. In this region, mean annual precipitation (MAP) ranges between about 150–250 mm (6″–10″), 70% of which falls during the cold season, November to May. Mid-summer through early autumn, June through October, is the dry portion of the year. During this period, the sub-surface water harvester provides supplemental water for wildlife for 30–90 days, depending upon the precipitation that year. The desert water harvester is constructed with commonly available, “over the counter” materials. The micro-catchment is made of a square-shaped, 20 mL. “PERMALON” polyethylene pond liner (approximately 22.9 m × 22.9 m = 523 m2) buried at a depth of about 60 cm. A PVC pipe connects the harvester with two storage tanks and a drinking trough. The total capacity of the water harvester is about 4777 L (1262 U.S. gallons) which includes three underground storage tanks, a trough and pipes. The drinking trough is refined with an access ramp for birds and small animals. The technology is simple, cheap, and durable and can be adapted to other uses, e.g. drip irrigation, short-term water for small livestock, poultry farming etc. The desert water harvester can be used to concentrate and collect water from precipitation and run-off in semi-arid and arid regions. Water harvested in such a relatively small area will not impact the ground water table but it should help to grow small areas of crops or vegetables to aid villagers in self-sufficiency.  相似文献   
143.
新疆河流洪水水污染分析   总被引:4,自引:0,他引:4  
洪水期间的水污染主要来源于面源。其特点是污染物的浓度高、负荷量大。给工业、渔业和人民生活都会带来不同程度的危害。悬浮物是洪水过程中的主要面污染产物,同时还作为载体吸附和携带大量的有机物、无机盐、重金属类和微生物进入水体,致使河流水质下降。在研究洪水灾害的同时。不应忽略洪水期间的水污染问题。  相似文献   
144.
应急监测案例分析   总被引:3,自引:1,他引:3  
叙述了某突发性不明污染源的应急监测经过,探讨了对此类应急监测应采取的措施,并阐述了相应的意见和看法。  相似文献   
145.
多氯联苯的气相色谱/质谱/质谱(GC/MS/MS)法测定   总被引:17,自引:0,他引:17  
采用气相色谱/质谱/质谱(GC/MS/MS)法测定多氯联苯(PCB),具有良好的灵敏度和选择性,在地表水样品检测时,样品只须进行简单的液液萃取-浓缩,不须任何净化过程即可上机分析,方法检出限低于ng/L级。  相似文献   
146.
环境监测机构体制改革设想   总被引:3,自引:1,他引:3       下载免费PDF全文
指出了环境监测机构存在的问题,提出环境监测机构体制改革应从3方面考虑:机构改革应实行垂直管理,政,事分开,职能改革应体现环境监测站以环境质量监测为基本职能;内部管理改革需建立以聘任制为基础的用人制度,岗位管理和竞争上岗制度,适当的分配激励机制。  相似文献   
147.
水体重金属污染生物监测的研究进展   总被引:11,自引:3,他引:11  
综述了重金属的毒性效应和水体重金属污染的现状,介绍了利用水生藻类、浮游动物群落和底栖动物监测水体重金属污染的研究进展及发展趋势。  相似文献   
148.
Nahanni National Park Reserve is located at southwestern NWT-Yukon border. One of the first UNESCO World Heritage sites, Nahanni lies within Taiga Cordillera and Taiga Shield Ecozones. Base and precious metal mining occurred upstream of Nahanni prior to park establishment. Nahanni waters, sediments, fish, and caribou have naturally elevated metals levels. Baseline water, sediment and fish tissue quality data were collected and analyzed throughout Nahanni during 1988–91 and 1992–97. These two programs characterized how aquatic quality variables are naturally varying in space and time, affected by geology, stream flow, seasonality, and extreme meteorological and geological events. Possible anthropogenic causes of aquatic quality change were examined. Measured values were compared to existing Guidelines and site-specific objectives were established.  相似文献   
149.
Water quality indices (WQIs) have been developed to assess the suitability of water for a variety of uses. These indices reflect the status of water quality in lakes, streams, rivers, and reservoirs. The concept of WQIs is based on a comparison of the concentration of contaminants with the respective environmental standards. The number, frequency, and magnitude by which the environmental standards for specific variables are not met in a given time period are reflected in WQIs. Further, the water quality trend analysis predicts the behavior of the water quality parameters and overall water quality in the time domain. In this paper, the concept of WQI was applied to three selected watersheds of Atlantic region: the Mersey River, the Point Wolfe River, and the Dunk River sites. To have robust study, two different water quality indices are used: Canadian Water Quality Index (CWQI), and British Columbia Water Quality Index (BWQI). The complete study was conducted in two steps. The first step was to organize and process the data into a format compatible with WQI analysis. After processing the input data, the WQI was calculated. The second step outlined in the paper discusses detailed trend analysis using linear and quadratic models for all the three sites. As per the 25 years trend analysis, overall water quality for agriculture use observed an improving trend at all the three sites studied. Water quality for raw water used for drinking (prior to treatment) and aquatic uses has shown improving trend at Point Wolfe River. It is further observed that pH, SO4, and NO3 concentrations are improving at Dunk River, Mersey River, and Point Wolfe River sites. To ascertain the reliability and significance of the trend analysis, a detailed error analysis and parametric significance tests were also conducted It was observed that for most of the sites and water uses quadratic trend models were a better fit than the linear models.  相似文献   
150.
More timely access to data and information on the initiation, evolution and effects of harmful algal blooms can reduce adverse impacts on valued natural resources and human health. To achieve this in the northern Gulf of Mexico, a pilot project was initiated to develop a user-driven, end-to-end (measurements to applications) observing system. A key strategy of the project is to coordinate existing state, federal and academic programs at an unprecedented level of collaboration and partnership. Resource managers charged with protection of public health and aquatic resources require immediate notice of algal events and a forecast of when, where and what adverse effects will likely occur. Further, managers require integrated analyses and interpretations, rather than raw data, to make effective decisions. Consequently, a functional observing system must collect and transform diverse measurements into usable forecasts. Data needed to support development of forecasts will include such properties as sea surface temperature, winds, currents and waves; precipitation and freshwater flows with related discharges of sediment and nutrients; salinity, dissolved oxygen, and chlorophyll concentrations (in vivo fluorescence); and remotely-sensed spatial images of sea surface chlorophyll concentrations. These data will be provided via a mixture of discrete and autonomous in situ sensing with near real-time data telemetry, and remote sensing from space (SeaWiFS), aircraft (hyperspectral imagery) or land (high-frequency radar). With calibration across these platforms, the project will ultimately provide a 4-dimensional visualization of harmful algae events in a time frame suitable to resource managers.  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