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   8989篇
  免费   745篇
  国内免费   2280篇
安全科学   366篇
废物处理   163篇
环保管理   1756篇
综合类   6497篇
基础理论   1053篇
环境理论   6篇
污染及防治   694篇
评价与监测   1053篇
社会与环境   383篇
灾害及防治   43篇
  2024年   53篇
  2023年   199篇
  2022年   291篇
  2021年   370篇
  2020年   376篇
  2019年   318篇
  2018年   265篇
  2017年   355篇
  2016年   362篇
  2015年   449篇
  2014年   469篇
  2013年   627篇
  2012年   595篇
  2011年   677篇
  2010年   545篇
  2009年   531篇
  2008年   445篇
  2007年   613篇
  2006年   623篇
  2005年   452篇
  2004年   419篇
  2003年   459篇
  2002年   391篇
  2001年   360篇
  2000年   341篇
  1999年   250篇
  1998年   189篇
  1997年   168篇
  1996年   150篇
  1995年   110篇
  1994年   110篇
  1993年   76篇
  1992年   70篇
  1991年   57篇
  1990年   40篇
  1989年   18篇
  1988年   13篇
  1987年   28篇
  1986年   15篇
  1985年   11篇
  1984年   6篇
  1982年   15篇
  1981年   17篇
  1980年   13篇
  1979年   10篇
  1978年   16篇
  1977年   5篇
  1973年   8篇
  1972年   8篇
  1971年   11篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
911.
残酸再利用工艺技术   总被引:1,自引:1,他引:0  
针对油田酸化过程中返排出的残酸处理困难,造成较大污染、浪费等问题,分析了残酸作为调剖剂的价值,研究了利用“残酸”进行调剖的工艺技术,并进行了现场试验,投入产出比为1:28,取得了较好的经济效益和社会效益,为”残酸”的再利用和环境保护找到了一条有效途径。  相似文献   
912.
室内空气中污染物的检测技术   总被引:3,自引:0,他引:3  
室内环境空气污染对人体健康影响很大,文中指出了影响人体健康的致病因子,分析了单个微粒的光通量和粒径之间的关系。鉴于单下颗粒的散射光信号很弱,本文提出一种方法,把激光器的内腔作为颗粒注入区,利用激光器的内腔功率谱密度远大于腔外功率密度的特点,结合先进的激光散控制理论,对空气中的颗粒进行检测。  相似文献   
913.
中国水资源与水工业的可持续发展   总被引:9,自引:1,他引:8  
可持续发展是当今世界发展的一种新模式,已成为全世纪普遍关注的热点。 可持续发展的基本观点。分析了影响我国水工业可持续发展的主要限制因素;(1)水资源写水污染严惩)水工业基础设施薄弱,传统的水工业对污染水处理难以相适应;(3)水工业管理存在多种问题。针对目前我国水资源开发利用和水工业发展2及存在的主要问题,提出了我国水工业面向可持续发展的优化对策与途径;(1)保护水源,防治水污染;(2)开源节流,节  相似文献   
914.
对灾害研究中几个问题的思考   总被引:2,自引:1,他引:1  
单修正 《灾害学》1999,14(4):85-89
对灾害研究中有关的几个问题进行了探讨。认为: 灾害学是最重要的自然社会科学; 人文灾害比自然灾害更具毁灭性; 研究人文灾害中的公路交通事故、核战争问题、人口问题、环境污染问题等具有重要的现实意义和深远的历史意义。  相似文献   
915.
环境资源的量化模型及估算指标体系   总被引:3,自引:0,他引:3  
本文依据区划环境标准,提出了环境资源的成本概念-环境成本。  相似文献   
916.
The aim of this paper was to investigate the effects of nitrogen (N) deposition on tree N cycling and identify potential biomarkers forNdeposition. Between April and October 2002 extensive fieldwork was undertaken at Mardley Heath in Hertfordshire. This woodland, located adjacent to the A1(M) motorway, is exposed to high levels of atmospheric nitrogen oxides from the traffic. Measurements of 15N, in vivo nitrate reductase (NR) activity, tissue, xylem and surface nitrate concentrations as well as N concentration and growth were made along a 700-m transect at 90° to the motorway. The 15N data show that oxidised N from the road traffic is taken up by nearby trees and is incorporated into plant tissues. Our measurements of NR activities suggest elevated rates close to the motorway. However, xylem sap, leaf tissue and leaf surface nitrate concentrations showed no differences between the roadside location and the most distant sampling point from the motorway. Taken together the 15N and nitrate reductase data suggest uptake and assimilation of N through the foliage.We conclude that for this lowland deciduouswoodland, tissue, xylem and surface measurements of nitrate are unreliable biomarkers for N deposition whereas 15N, growth measurements and integrated seasonal NR might be useful. The results also point to the benefit of roadside tree planting to screen pollution from motor vehicles.  相似文献   
917.
Pollution distribution maps of copper (Cu), zinc (Zn) and lead (Pb) for Erzurum province were developed on the basis of chemical analysis of Scots pine (Pinus sylvestris L.) needles collected from randomly selected sampling points during 2 years. The maps show deposition zones for the studied elements and could help in identification of sources and directions of air pollution dispersion. This study indicated that vegetation in Erzurum was greatly endangered by sulphur dioxide (SO(2)), whereas Zn does not pose an immediate threat to vegetation in most of the country's territory. However, in the city center, main and secondary road agglomeration, very high pollution with Pb and Cu could limit growth. Higher levels of SO(2) measured in some areas of Erzurum might be harmful for human and animal health. Results of this study indicated that Scots pine needles were not contaminated by Zn.  相似文献   
918.
The main goal of the present study was to develop an ecological integrity index for littoral wetland management and conservation in semiarid Mediterranean areas that have been highly impacted by agriculture, including the selection of pressure and state indicators at landscape and wetlands scales that reflect the status, condition, and trends of wetlands ecosystems. We used a causality framework based on the relationship between pressure of anthropogenic activities and the ecological state of wetlands and their catchments, integrating environmental, biologic, economic, and social issues. From the application of 51 indicators in 7 littoral wetlands in the southeastern Iberian Peninsula, we selected 12 indicators (5 at catchment scale and 7 at wetland scale) to constitute the ecological integrity index proposed. The potential nitrogen export per area at catchment scale and the potential relative nitrogen export from the area surrounding the wetlands were the best pressure single predictors of state indicators with a causal relationship with environmental meaning. Wetlands in catchments with more agriculture had less ecological integrity than those in less impacted areas. A wide riparian zone in some wetlands acts as a buffer area, diminishing the effects of intensive agriculture. The index of ecological integrity developed here has a number of essential characteristics that make it a useful tool for ecosystem managers and decision-makers. The index can be used to (1) assess and control ecological integrity, (2) diagnose probable causes of ecological impairment, (3) establish criteria for protecting and restoring wetland ecosystems, and (4) integrate catchment management. Published online  相似文献   
919.
ABSTRACT The direction of heated effluents from large thermal power plants into streams and lakes has been a matter of public concern for some time, and the collection of prototype data related to the hydraulic aspects has taken on massive proportions. Unfortunately, most of the data are proprietary and not available for public analysis. The authors have endeavored to collect such data as are available to them for the initiation of steps toward generalization and the discussion of some of the more evident hydraulic considerations. The study is primarily concerned with rivers, including estuaries, with some interest in cooling ponds.  相似文献   
920.
Air pollution has become an actual problem in Balikesir because of rapid urbanisation and increasing of the polluting sources. Air pollutionproblems occur under the unfavorable meteorological conditions which increase in frequency of occurrence in winter due to use of low quality lignite coals for heating. The `Protection of Air Quality' in Turkey dated 1986 is based on the human health criteria. But the critical limit values are lethal for the forest trees as far as SO2 is concerned. The field observations showed that leaves of the trees have yellow spots indicating acid burns in Balikesir. This study aims at determining the relationships between the SO2 concentrationsin the air under selected climatic conditions, and the effects of air pollution on forest trees in Balikesir. Samples of leaves were collected from the City Parks in Balikesir, Deirmenboaz forested area located 10 km far fromBalikesiron the Balikesir-Bursa highway, and from the forestation areas near the Balikesir-Edremit highway. Sulfur contents of the leaves were very high especially in the city (2650–5300 g m-3).Samples from other areas had values lower than this range but above the usual values (850–3612 g m-3). The diameter increments of the trees were found to be lower and these results clearly showed the adverse impacts. Negative correlations were found between these sulfur concentrations and the daily mean temperatures and wind speeds. Positive correlation was seen between these concentrations and pressures, humidities. Emission sources must be controlled in order to safeguard the forests which protects the soil, facilitate water production, assimilate carbon dioxide in air and produce oxygen. It must be considered that the problems are not only regional but have a global identity.  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