全文获取类型
收费全文 | 1357篇 |
免费 | 180篇 |
国内免费 | 124篇 |
专业分类
安全科学 | 250篇 |
废物处理 | 13篇 |
环保管理 | 320篇 |
综合类 | 565篇 |
基础理论 | 172篇 |
污染及防治 | 32篇 |
评价与监测 | 155篇 |
社会与环境 | 85篇 |
灾害及防治 | 69篇 |
出版年
2024年 | 5篇 |
2023年 | 29篇 |
2022年 | 54篇 |
2021年 | 77篇 |
2020年 | 56篇 |
2019年 | 62篇 |
2018年 | 45篇 |
2017年 | 75篇 |
2016年 | 99篇 |
2015年 | 55篇 |
2014年 | 64篇 |
2013年 | 87篇 |
2012年 | 87篇 |
2011年 | 97篇 |
2010年 | 64篇 |
2009年 | 82篇 |
2008年 | 49篇 |
2007年 | 98篇 |
2006年 | 69篇 |
2005年 | 48篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 40篇 |
2001年 | 27篇 |
2000年 | 34篇 |
1999年 | 17篇 |
1998年 | 18篇 |
1997年 | 23篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1971年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有1661条查询结果,搜索用时 745 毫秒
921.
基于数据包络分析,利用BCC模型和Malmquist模型分别衡量了2003--2009年大连市生产性服务业的综合效率和全要素生产率。研究结果表明,大连市生产性服务业总体呈规模收益递减状态,技术进步是推动大连市生产性服务业发展的主要动力,产业发展呈现较大波动性。 相似文献
922.
When spatial fishing data is fed into systematic conservation planning processes the cost to a fishery could be ensured to be minimal in the zoning of marine protected areas. We used vessel monitoring system (VMS) data to map the distribution of prawn trawling and calculate fishing intensity for 1-ha grid cells, in the Kosterhavet National Park (Sweden). We then used the software Marxan to generate cost-efficient reserve networks that represented every biotope in the Park. We asked what were the potential gains and losses in terms of fishing effort and species conservation of different planning scenarios. Given a conservation target of 10 % representation of each biotope, the fishery need not lose more than 20 % of its fishing grounds to give way to cost-efficient conservation of benthic diversity. No additional reserved area was needed to achieve conservation targets while minimizing fishing costs. We discuss the benefits of using VMS data for conservation planning. 相似文献
923.
Asef MR 《Disasters》2008,32(3):480-498
Earthquakes have probably been the most deadly form of natural disaster in the past century. Diversity of earthquake specifications in terms of magnitude, intensity and frequency at the semi-continental scale has initiated various kinds of disasters at a regional scale. Additionally, diverse characteristics of countries in terms of population size, disaster preparedness, economic strength and building construction development often causes an earthquake of a certain characteristic to have different impacts on the affected region. This research focuses on the appropriate criteria for identifying the severity of major earthquake disasters based on some key observed symptoms. Accordingly, the article presents a methodology for identification and relative quantification of severity of earthquake disasters. This has led to an earthquake disaster vulnerability model at the country scale. Data analysis based on this model suggested a quantitative, comparative and meaning full interpretation of the vulnerability of concerned countries, and successfully explained which countries are more vulnerable to major disasters. 相似文献
924.
Papadopoulos A Malamis S Moustakas K Kiranoudis CT Loizidou M 《Environmental monitoring and assessment》2007,130(1-3):255-270
This work focuses on the development and application of appropriate software tools for recording, assessing and reporting
data related to the operation of the Urban Wastewater Treatment Plants (UWTPs) in Cyprus. An appropriate Internet-Based Management
System was designed, developed and installed at the premises of the UWTPs and of the Cypriot Competent Authority (Water Development
Department — WDD) in order to coordinate and disseminate tasks and related information for monitoring the operation of UWTPs.
In addition, a client Geographical Information System database was compiled to be used for obtaining and analyzing spatial
information. The software tools are based on common procedures and state-of-the-art technology for the recording and transmission
of data and information and they provide an integrated view related to the operation and the efficiency of wastewater treatment
systems. Moreover, continuous control and systematic monitoring of the UWTPs by the operators as well as continuous and direct
supervision of the UWTPs environmental performance is achieved by the personnel of the Competent Authority. Furthermore, direct
and unobstructed provision of data to the Competent Authority of Cyprus is accomplished by the operators of the UWTPs, while
the Competent Authority is supported to compose full and representative reports to the European Commission and other International
Organizations. The developed tools enable the direct recording of data obtained through measurements and analyses, permit
the comparison of data with existing legislation and provide an integrated picture of the operation of the wastewater treatment
plants as well as the option to focus and assess each individual treatment stage. 相似文献
925.
Addressing landscape-level threats to stream fishes such as habitat and hydrological alterations requires adequate watershed-level
species inventories. Where watershed-level ichthyofaunal surveys are prohibitively expensive, existing (historical) data sources
may provide an option for compiling species lists. However, it is critical that managers consider potential biases or limitations
of species lists compiled from existing data. Here we assess the suitability of species lists compiled from existing data
sources for making watershed-level fish management and conservation decisions. For nine Great Lakes watersheds, we developed
existing species lists by compiling all available federal and state agency and museum fish survey data. We then compared the
size and species composition of existing species lists to current species lists compiled from intensive field surveys, conducted
in 2002, of the same watersheds. Species lists compiled from commonly available existing data sources, such as state and federal
agency and museum data, missed many species detected during our 2002 field surveys. In most watersheds, more than 10 species
were missed (range 5–21) on existing lists. Sampling over multiple years and seasons increased the size of both current (field)
and existing species lists. Existing species lists compiled from surveys conducted over multiple years and seasons included
an average of 15 species not captured during the 2002 field surveys. However, such multiyear existing datasets are rare and
not available for many watersheds. In addition, species lists compiled from older existing surveys (e.g., before 1984) did
not accurately represent current species composition of the watersheds and our results indicate several apparent misidentifications
or errors on these lists. Lastly, while most game species were detected on existing lists, migratory species and recently
introduced species were commonly missed on these lists. We conclude with recommendations for using existing data for watershed-level
stream fish management and conservation decisions. 相似文献
926.
927.
Lieven Declerck Geert Molenberghs Marc Aerts Louise Ryan 《Environmental and Ecological Statistics》2000,7(1):57-76
Developmental toxicity experiments are designed to assess potential adverse effects of drugs and other exposures on developing fetuses from pregnant dams. Extrapolation to humans is a very difficult problem. An important issue here is whether risk assessment should be based on the fetus or the litter level. In this paper, fetus and litter-based risks that properly account for cluster size are defined and compared for the beta-binomial model and a conditional model for clustered binary data. It is shown how the hierarchical structure of non-viable implants and viable but malformed offspring can be incorporated. Risks based on a joint model for death/resorption and malformation are contrasted with risks based on an adverse event defined as either death/resorption or malformation. The estimation of safe exposure levels for all risk types is discussed and it is shown how estimation of the cluster size distribution affects variance estimation. The methods are applied to data collected under the National Toxicology Program and in large sample simulations. 相似文献
928.
Preisler Haiganoush K. Haase Sally M. Sackett Stephen S. 《Environmental and Ecological Statistics》2000,7(3):239-254
Prescribed fire is a management tool used by wildland resource management organizations in many ecosystems to reduce hazardous fuels and to achieve a host of other objectives. To study the effects of fire in naturally accumulating fuel conditions, the ambient soil temperature is monitored beneath prescribed burns. In this study we developed a stochastic model for temperature profiles (values at 15 minute intervals) recorded at four depths beneath the soil during a large prescribed burn study. The model was used to assess the temporal fit of the data to particular solutions of the heat equation. We used a random effects model to assess the effects of observed site characteristics on maximum temperatures and to estimate risks of temperatures exceeding critical levels in future similar prescribed fires. Contour plots of estimated risks of temperatures exceeding 60°C for a range of fuel levels and soil depths indicated high risks of occurrence, especially when the moisture levels are low. However, the natural variability among sites seems to be large, even after controlling fuel and moisture levels, resulting in large standard errors of predicted risks. 相似文献
929.
浅议环境监测数据的审核 总被引:1,自引:0,他引:1
叶萍 《中国环境管理干部学院学报》2010,20(2):54-56
环境监测数据的审核工作是整个质量保证体系中最后有效的质量控制手段。针对我国环境监测数据审核现状与存在的问题,将"五性"质量指标贯穿于整个环境监测工作当中,是提升监测数据的审核力度,保证监测数据正确、可靠的有力措施之一。 相似文献
930.
地表水自动监测网数据自动审核的创新与实践 总被引:1,自引:0,他引:1
在地表水质量自动监测网络的质量保证管理中,山东省省、市两级监控中心使用计算机数据审核系统对监测数据进行实时监控和质量控制,创新地实现了对监测数据有效性的自动判别、监测网的运行情况自动评价等自动化质控措施。 相似文献