全文获取类型
收费全文 | 2339篇 |
免费 | 145篇 |
国内免费 | 120篇 |
专业分类
安全科学 | 391篇 |
废物处理 | 20篇 |
环保管理 | 575篇 |
综合类 | 703篇 |
基础理论 | 347篇 |
环境理论 | 2篇 |
污染及防治 | 81篇 |
评价与监测 | 136篇 |
社会与环境 | 127篇 |
灾害及防治 | 222篇 |
出版年
2024年 | 6篇 |
2023年 | 25篇 |
2022年 | 35篇 |
2021年 | 38篇 |
2020年 | 39篇 |
2019年 | 42篇 |
2018年 | 24篇 |
2017年 | 65篇 |
2016年 | 82篇 |
2015年 | 70篇 |
2014年 | 57篇 |
2013年 | 107篇 |
2012年 | 133篇 |
2011年 | 168篇 |
2010年 | 121篇 |
2009年 | 129篇 |
2008年 | 135篇 |
2007年 | 163篇 |
2006年 | 137篇 |
2005年 | 129篇 |
2004年 | 113篇 |
2003年 | 129篇 |
2002年 | 87篇 |
2001年 | 75篇 |
2000年 | 82篇 |
1999年 | 69篇 |
1998年 | 40篇 |
1997年 | 44篇 |
1996年 | 36篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 30篇 |
1992年 | 24篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1974年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有2604条查询结果,搜索用时 15 毫秒
51.
Ryan C. Schwartz Peter J. Deadman Daniel J. Scott Linda D. Mortsch 《Journal of the American Water Resources Association》2004,40(3):647-662
ABSTRACT: Recent research that couples climate change scenarios based on general circulation models (GCM) with Great Lakes hydrologic models has indicated that average water levels are projected to decline in the future. This paper outlines a methodology to assess the potential impact of declining water levels on Great Lakes waterfront communities, using the Lake Huron shoreline at Goderich, Ontario, as an example. The methodology utilizes a geographic information system (GIS) to combine topographic and bathymetric datasets. A digital elevation surface is used to model projected shoreline change for 2050 using water level scenarios. An arbitrary scenario, based on a 1 m decline from February 2001 lake levels, is also modeled. By creating a series of shoreline scenarios, a range of impact and cost scenarios are generated for the Goderich Harbor and adjacent marinas. Additional harbor and marina dredging could cost as much as CDN $7.6 million. Lake freighters may experience a 30 percent loss in vessel capacity. The methodology is used to provide initial estimates of the potential impacts of climate change that can be readily updated as more robust climate change scenarios become available and is adaptable for use in other Great Lakes coastal communities. 相似文献
52.
利用信息扩散模式对安徽及华东地区地震的风险分析 总被引:8,自引:1,他引:8
本文利用信息扩散模式,分别从年地震频次和年最大震级两个方面对安徽及华东地区的地震风险进行评估.结果显示:安徽地区ML≥3.0地震,年频次4次以上,约两年一遇;年发生ML≥3.9地震,则3年可能遇一次.而华东地区ML≥4.0地震,年频次4次以上,大约3年一遇;年发生ML≥4.9的地震,则可能2年遇一次. 相似文献
53.
自然灾害风险区划图的一个潜在发展方向 总被引:18,自引:7,他引:18
由于自然灾害系统的复杂性及数据资料的不完备性,人们不可能精确估计任何自然灾害发生的概率,"概率值估不准"是现有超越概率风险区划图的致命弱点.简要回顾了针对这一问题已进行的提高估计精度和进行模糊风险计算的有关研究,并将模糊风险研究引入风险区划图的编制,给出了自然灾害软风险区划图的定义和一个初步的样式.讨论了这种风险图在体现风险值估不准方面,以及在为用户提供更多风险信息,为决策者提供调整余地等方面的优点.研究结果表明,软风险区划图是自然灾害风险区划图的一个潜在发展方向.为推进这一研究领域的发展,对今后的工作提出了一些建议. 相似文献
54.
利用信息不对称理论对市场交易中的道德风险和逆向选择进行了解释。对国家同商业银行及中介机构的信息不对称,商业银行同工商企业的信息不对称,国家金融机构信息获取方面存在的困难的原因进行了分析。研究了由于信息不对称利率、汇率、管理及决策在金融行业的风险,以及操作过程中,贷款对象选择,对中小企业贷款的风险。只要充分重视金融风险,采取得当的防范对策,风险是可以防范的。 相似文献
55.
56.
基于GIS技术的海塘防洪减灾信息系统 总被引:2,自引:0,他引:2
海塘工程的规划、设计、建设、维护和管理,对沿海省份经济发展和人民生命财产的安全十分重要,历来受到政府和沿海居民的高度重视.介绍了基于GIS技术的海塘防洪减灾信息系统的主要功能及逻辑结构,分析了海塘数据库的特点,详细讨论了海塘属性和空间数据库的建库内容及方法.最后通过应用实例,验证了系统技术路线的合理性、正确性和实用性. 相似文献
57.
在国民经济中占有主导地位的油气企业同时也是造成环境污染的主体之一。因此,建立油气企业环境会计制度有极其重要的现实意义。文章针对我国油气企业环境会计制度应用现状,运用环境会计基本理论,对企业环境会计核算方法及信息传播模式进行了探讨,以期为油气企业环境会计制度的实施提供一些理论依据和具体方法,推动油气企业环境会计制度的发展。 相似文献
58.
Ross S. Lunetta Richard G. Greene John G. Lyon 《Journal of the American Water Resources Association》2005,41(5):1129-1147
This study quantified nonpoint source nitrogen (NPS‐N) sources and sinks across the 14,582 km2 Neuse River Basin (NRB) located in North Carolina, to provide tabular data summaries and graphic overlay products to support the development of management approaches to best achieve established N reduction goals. First, a remote sensor derived, land cover classification was performed to support modeling needs. Modeling efforts included the development of a mass balance model to quantify potential N sources and sinks, followed by a precipitation event driven hydrologic model to effectively transport excess N across the landscape to individual stream reaches to support subsequent labeling of transported N values corresponding to source origin. Results indicated that agricultural land contributed 55 percent of the total annual NPS‐N loadings, followed by forested land at 23 percent (background), and urban areas at 21 percent. Average annual N source contributions were quantified for agricultural (1.4 kg/ha), urban (1.2 kg/ha), and forested cover types (0.5 kg/ha). Nonpoint source‐N contributions were greatest during the winter (40 percent), followed by spring (32 percent), summer (28 percent), and fall (0.3 percent). Seasonal total N loadings shifted from urban dominated and forest dominated sources during the winter, to agricultural sources in the spring and summer. A quantitative assessment of the significant NRB land use activities indicated that high (greater than 70 percent impervious) and medium (greater than 35 percent impervious) density urban development were the greatest contributors of NPS‐N on a unit area basis (1.9 and 1.6 kg/ha/yr, respectively), followed by row crops and pasture/hay cover types (1.4 kg/ha/yr). 相似文献
59.
BASE FLOW RECESSION RATES,LOW FLOWS,AND HYDROLOGIC FEATURES OF SMALL WATERSHEDS IN PENNSYLVANIA,USA1
David Brandes Justin G. Hoffmann James T. Mangarillo 《Journal of the American Water Resources Association》2005,41(5):1177-1186
This paper examines the relationships between measurable watershed hydrologic features, base flow recession rates, and the Q7,10 low flow statistic (the annual minimum seven‐day average streamflow occurring once every 10 years on average). Base flow recession constants were determined by analyzing hydrograph recession data from 24 small (>130 km2), unregulated watersheds across five major physiographic provinces of Pennsylvania, providing a highly variable dataset. Geomorphic, hydrogeologic, and land use parameters were determined for each watershed. The base flow recession constant was found to be most strongly correlated to drainage density, geologic index, and ruggedness number (watershed slope); however, these three parameters are intercorrelated. Multiple regression models were developed for predicting the recession rate, and it was found that only two parameters, drainage density and hydrologic soil group, were required to obtain good estimates of the recession constant. Equations were also developed to relate the recession rates to Q7,10 per unit area, and to the Q7,10/Q50 ratio. Using these equations, estimates of base flow recession rates, Q7,10, and streamflow reduction under drought conditions can be made for small, ungaged basins across a wide range of physiography. 相似文献
60.
David Brandes Gregory J. Cavallo Michael L. Nilson 《Journal of the American Water Resources Association》2005,41(6):1377-1391
Rapid land development is raising concern regarding the ability of urbanizing watersheds to sustain adequate base flow during periods of drought. Long term streamflow records from unregulated watersheds of the lower to middle Delaware River basin are examined to evaluate the impact of urbanization and imperviousness on base flow. Trends in annual base flow volumes, seven‐day low flows, and runoff ratios are determined for six urbanizing watersheds and four reference watersheds across three distinct physiographic regions. Hydrograph separation is used to determine annual base flow and stormflow volumes, and nonparametric trend tests are conducted on the resulting time series. Of the watersheds examined, the expected effects of declining base flow volumes and seven‐day low flows and increasing stormflows are seen in only one watershed that is approximately 20 percent impervious and has been subject to a net water export over the past 15 years. Both interbasin transfers and hydrologic mechanisms are invoked to explain these results. The results show that increases in impervious area may not result in measurable reductions in base flow at the watershed scale. 相似文献