全文获取类型
收费全文 | 2855篇 |
免费 | 271篇 |
国内免费 | 589篇 |
专业分类
安全科学 | 448篇 |
废物处理 | 101篇 |
环保管理 | 539篇 |
综合类 | 1358篇 |
基础理论 | 301篇 |
污染及防治 | 397篇 |
评价与监测 | 228篇 |
社会与环境 | 106篇 |
灾害及防治 | 237篇 |
出版年
2024年 | 12篇 |
2023年 | 31篇 |
2022年 | 77篇 |
2021年 | 95篇 |
2020年 | 107篇 |
2019年 | 77篇 |
2018年 | 73篇 |
2017年 | 110篇 |
2016年 | 133篇 |
2015年 | 150篇 |
2014年 | 164篇 |
2013年 | 226篇 |
2012年 | 212篇 |
2011年 | 217篇 |
2010年 | 169篇 |
2009年 | 168篇 |
2008年 | 135篇 |
2007年 | 190篇 |
2006年 | 178篇 |
2005年 | 170篇 |
2004年 | 134篇 |
2003年 | 116篇 |
2002年 | 113篇 |
2001年 | 100篇 |
2000年 | 101篇 |
1999年 | 65篇 |
1998年 | 35篇 |
1997年 | 55篇 |
1996年 | 30篇 |
1995年 | 43篇 |
1994年 | 25篇 |
1993年 | 29篇 |
1992年 | 21篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1973年 | 3篇 |
1972年 | 7篇 |
1971年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有3715条查询结果,搜索用时 15 毫秒
51.
52.
Soil and water loss in the Lancang River-Mekong River watershed (in Yunnan section, China) and its control measures 总被引:1,自引:0,他引:1
MekongRiverisoriginatedinthenorthernrangeofTibetQinghaiPlateauofChina,flowingthroughsixcountries,theyareChina(YunnanProvince),M?.. 相似文献
53.
54.
55.
就目前电厂循环流化床锅炉运行中存在的床温波动问题,讨论了导致床温波动的因素,并针对性地提出了控制床温的一些措施。 相似文献
56.
Keith E. Schilling Robert D. Libra 《Journal of the American Water Resources Association》2003,39(4):851-860
ABSTRACT: Historical trends in annual discharge characteristics were evaluated for 11 gauging stations located throughout Iowa. Discharge records from nine eight‐digit hydrologic unit code (HUC‐8) watersheds were examined for the period 1940 to 2000, whereas data for two larger river systems (Cedar and Des Moines Rivers) were examined for a longer period of record (1903 to 2000). In nearly all watersheds evaluated, annual base flow, annual minimum flow, and the annual base flow percentage significantly increased over time. Some rivers also exhibited increasing trends in total annual discharge, whereas only the Maquoketa River had significantly decreased annual maximum flows. Regression of stream discharge versus precipitation indicated that more precipitation is being routed into streams as base flow than as storm flow in the second half of the 20th Century. Reasons for the observed stream flow trends are hypothesized to include improved conservation practices, greater artificial drainage, increasing row crop production, and channel incision. Each of these reasons is consistent with the observed trends, and all are likely responsible to some degree in most watersheds. 相似文献
57.
Occurence and Distribution of Polycyclic Aromatic Hydrocarbons in Ankara Precipitation 总被引:1,自引:0,他引:1
Urban atmospheric environment contains many trace organic pollutants that are related to the incomplete fuel combustion in domestic heating, industrial plants and automobile traffic. Removal of these pollutants from the atmosphere takes place through wet and dry deposition as well as chemical transformations. In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) in wet deposition samples were determined at an urban site of Turkey. Wet and dry deposition samples were collected using Andersen Rain Sampler. The sampler was modified accordingly for the collection of organic pollutants. Collected samples were preconcentrated by using solid phase extraction (SPE) disks and consecutively analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Among the 13 compounds quantified in this study, anthracene, fluoranthene, and pyrene were found more frequently and at elevated concentrations (202, 271 and 260 ng L-1 mean concentrations, respectively).Concentrations of PAHs were found to be high in winter period. 相似文献
58.
Frank A. Ward James F. Booker 《Journal of the American Water Resources Association》2003,39(2):427-440
ABSTRACT: The U.S. Endangered Species Act (ESA) restricts federal agencies from carrying out actions that jeopardize the continued existence of any endangered species. The U.S. Supreme Court has emphasized that the language of the ESA and its amendments permits few exceptions to the requirement to give endangered species the highest priority. This paper estimates economic costs associated with one measure for increasing instream flows to meet critical habitat requirements of the endangered Rio Grande silvery minnow. Impacts are derived from an integrated regional model of the hydrology, economics, and institutions of the upper Rio Grande Basin in Colorado, New Mexico, Texas, and Mexico. One proposal for providing minimum streamflows to protect the silvery minnow from extinction would provide guaranteed year round streamflows of at least 50 cubic feet per second in the San Acacia reach of the upper Rio Grande. These added flows can be accomplished through reduced surface diversions by New Mexico water users in dry years when flows would otherwise be reduced below the critical level required by the minnow. Based on a 44‐year simulation of future inflows to the basin, we find that some agricultural users suffer damages, but New Mexico water users as a whole do not incur damages from a policy that reduces stream depletions sufficiently to provide habitat for the minnow. The same policy actually benefits downstream users, producing average annual benefits of over $200,000 per year for west Texas agriculture, and over $1 million for El Paso municipal and industrial water users, respectively. Economic impacts of instream flow deliveries for the minnow are highest in drought years. 相似文献
59.
泥石流输沙对小江中下游河床演变的影响 总被引:4,自引:1,他引:4
对小江中下游近90km河床及两岸泥石流进行了调查研究。得到:泥石流输沙年际和季节变化大;泥石流高强度的输沙造成小江河床特殊的平面和剖面特征;泥石流堵塞小江河道,对纵比降有再造作用;泥沙使小江河床以年均20cm~50cm速度抬升。 相似文献
60.
黄河断流成因及人文思考 总被引:2,自引:0,他引:2
日益严峻的黄河断流现象严重地影响了黄河流域经济和社会的可持续发展,也制约了西部大开发战略的实施。在分析了黄河断流的危害、成因的基础上,提出了在工程措施之外,要从人口、法律制度、产业结构等人文因素方面入手缓解黄河断流。 相似文献