全文获取类型
收费全文 | 2336篇 |
免费 | 147篇 |
国内免费 | 119篇 |
专业分类
安全科学 | 391篇 |
废物处理 | 20篇 |
环保管理 | 574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 | 135篇 |
社会与环境 | 127篇 |
灾害及防治 | 222篇 |
出版年
2024年 | 4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2602条查询结果,搜索用时 265 毫秒
61.
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
62.
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
63.
地理信息系统(GIS)技术现已广泛应用于环境领域。简要介绍了该技术的功能特点,并从大气、水、土壤、噪声四个方面探讨了GIS在环境保护中的应用。研究结果表明,GIS是研究环境子系统协同效应的实用技术。 相似文献
64.
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
65.
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
66.
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
67.
本文根据采油厂生产过程风险特点,以生产单元为对象,通过建立全员参与的HSE监督检查体系,实现对采油厂HSE监督检查标准的统一规范,利用开发的HSE监督检查信息集成平台,创建完成采油厂HSE监督检查管理系统。在大庆油田第五采油厂的应用实践显示,其能为采油厂带来巨大的风险管理效益,是全面落实直线与属地HSE责任的有效载体。对于采油厂有效实施HSE监督检查具有重大意义,是HSE管理制度的一种创新。 相似文献
68.
KEN LONGENECKER YVONNE L. CHAN ROBERT J. TOONEN DAVID B. CARLON TERRY L. HUNT ALAN M. FRIEDLANDER EDWARD E. DEMARTINI 《Conservation biology》2014,28(5):1322-1330
Reef‐fish management and conservation is hindered by a lack of information on fish populations prior to large‐scale contemporary human impacts. As a result, relatively pristine sites are often used as conservation baselines for populations near sites affected by humans. This space‐for‐time approach can only be validated by sampling assemblages through time. We used archaeological remains to evaluate whether the remote, uninhabited Northwestern Hawaiian Islands (NWHI) might provide a reasonable proxy for a lightly exploited baseline in the Main Hawaiian Islands (MHI). We used molecular and morphological techniques to describe the taxonomic and size composition of the scarine parrotfish catches present in 2 archaeological assemblages from the MHI, compared metrics of these catches with modern estimates of reproductive parameters to evaluate whether catches represented by the archaeological material were consistent with sustainable fishing, and evaluated overlap between size structures represented by the archaeological material and modern survey data from the MHI and the NWHI to assess whether a space‐for‐time substitution is reasonable. The parrotfish catches represented by archaeological remains were consistent with sustainable fishing because they were dominated by large, mature individuals whose average size remained stable from prehistoric (AD approximately 1400–1700) through historic (AD 1700–1960) periods. The ancient catches were unlike populations in the MHI today. Overlap between the size structure of ancient MHI catches and modern survey data from the NWHI or the MHI was an order of magnitude greater for the NWHI comparison, a result that supports the validity of using the NWHI parrotfish data as a proxy for the MHI before accelerated, heavy human impacts in modern times. Evidencia Arqueológica de la Validez de Poblaciones de Peces en Arrecifes Sin Explotar como Objetivos de Apoderamiento para Poblaciones Actuales 相似文献
69.
ABSTRACTThe present study was carried out to investigate the effect of three organic matters (stalk powder, microbial fertilizer, and manure) on Leymus chinensis germination, growth, and urease activity and available nitrogen (N) in coastal saline soil. The study was conducted in a completely randomized design with eight treatments: J0V0Y0, J1V0Y0, J0V1Y0, J0V0Y1, J1V1Y0, J1V0Y1, J0V1Y1, J1V1Y1. The notations were based on the quantities of each agent added to 1 kg of coastal saline soil: J0 – no straw powder, J1 – 0.2 kg straw powder, Y0 – no manure, Y1 – 0.3 kg manure, V0 – no microbial fertilizer, V1 – 0.2 L microbial fertilizer, each in quantic repeat. L. chinensis was sown as 50 seeds per pot. Results indicated that addition of organic agents exerted a significantly enhanced germination, increase in fresh weight and elevated soil urease activity. Soil available N levels were significantly positively correlated with soil urease activity and fresh weight, but not with germination rate. It is noteworthy that the halophyte L. chinensis showed improved characteristics when grown in coastal saline soil with addition of organic amendments. 相似文献
70.
Prioritizing sites for conservation based on similarity to historical baselines and feasibility of protection 下载免费PDF全文
Traci Popejoy Charles R. Randklev Thomas M. Neeson Caryn C. Vaughn 《Conservation biology》2018,32(5):1118-1127
The concept of shifting baselines in conservation science implies advocacy for the use of historical knowledge to inform these baselines but does not address the feasibility of restoring sites to those baselines. In many regions, conservation feasibility varies among sites due to differences in resource availability, statutory power, and land‐owner participation. We used zooarchaeological records to identify a historical baseline of the freshwater mussel community's composition before Euro‐American influence at a river‐reach scale (i.e., a kilometer stretch of river that is abiotically similar) in the Leon River of central Texas (U.S.A.). We evaluated how the community reference position and the feasibility of conservation might enable identification of sites where conservation actions would preserve historically representative communities and be likely to succeed. We devised a conceptual model that incorporated community information and landscape factors to link the best conservation areas to potential cost and conservation benefits. Using fuzzy ordination, we identified modern mussel beds that were most like the historical baseline. We then quantified housing density and land use near each river reach identified to estimate feasibility of habitat restoration. Using our conceptual framework, we identified reaches of high conservation value (i.e., contain the best mussel beds) and where restoration actions would be most likely to succeed. Reaches above Lake Belton were most similar in species composition and relative abundance to zooarchaeological sites. A subset of these mussel beds occurred in locations where conservation actions appeared most feasible. Our results show how to use zooarchaeological data (biodiversity data often readily available) and estimates of conservation feasibility to inform conservation priorities at a local spatial scale. 相似文献