全文获取类型
收费全文 | 1073篇 |
免费 | 39篇 |
国内免费 | 82篇 |
专业分类
安全科学 | 158篇 |
废物处理 | 12篇 |
环保管理 | 407篇 |
综合类 | 200篇 |
基础理论 | 184篇 |
环境理论 | 3篇 |
污染及防治 | 73篇 |
评价与监测 | 45篇 |
社会与环境 | 57篇 |
灾害及防治 | 55篇 |
出版年
2023年 | 7篇 |
2022年 | 21篇 |
2021年 | 28篇 |
2020年 | 34篇 |
2019年 | 29篇 |
2018年 | 24篇 |
2017年 | 30篇 |
2016年 | 49篇 |
2015年 | 40篇 |
2014年 | 40篇 |
2013年 | 90篇 |
2012年 | 37篇 |
2011年 | 64篇 |
2010年 | 30篇 |
2009年 | 56篇 |
2008年 | 45篇 |
2007年 | 59篇 |
2006年 | 48篇 |
2005年 | 40篇 |
2004年 | 39篇 |
2003年 | 46篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 31篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 17篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1984年 | 4篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 10篇 |
1971年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有1194条查询结果,搜索用时 31 毫秒
921.
Michael J. Mason Jeremy Mennis J. Douglas Coatsworth Thomas Valente Frank Lawrence Patricia Pate 《Journal of environmental psychology》2009
Geographic and substance use data were collected from 301 urban adolescents to compare the perceived and observed risk and safety associated with their home and activity space locations (routine locations). The geographic characteristics of the neighborhood surrounding each location was summarized according to features theorized to be risky, such as criminal activity and alcohol sales, and features theorized to be safe, such as recreation centers and churches. Data on socioeconomic status, derived from U.S. Bureau of the Census data, were also used to characterize locations. Adolescents' homes were typically perceived as safe despite observed measures of risk such as density of crimes and proximity to alcohol outlets. This held for both substance users and non-users. Differences in geographic characteristics for safe and risky activity spaces were observed for both substance users and non-users, with non-users appearing to be more sensitive to the presence of risky characteristics in the environment than substance users. Results highlight the need and provide a methodology to collect fine-grained activity space data instead of relying only on home residence when attempting to represent place and health behaviors with urban youth. 相似文献
922.
Kirstin Dow Richard L. Murphy Gregory J. Carbone 《Journal of the American Water Resources Association》2009,45(1):187-197
Abstract: The increasing availability of web mapping tools creates new opportunities to bridge decision‐makers’ climate information needs with technical capabilities. These new tools, however, raise familiar, unresolved issues related to cartographic representation. Using an on‐line drought mapping tool, this study seeks to understand which spatial unit best meets the desire drought managers have for “local” information, their comprehension of uncertainties introduced in mapping information at local scales, and their willingness to trade off accuracy for information at a desired unit. We found that the most useful local map information includes regional context and boundaries which present their local area of interest. Even among this experienced, well‐educated, professional group, those who had not taken a GIS or cartography class did not fully recognize the role of interpolation in creating and introducing uncertainty to some drought maps. Those who did recognize the uncertainty introduced by interpolation still strongly favored maps that provided estimated values for all areas vs. station point accuracy. Mapping poses a unique set of challenges to communicating risk and uncertainty. As more decision‐support efforts incorporate web mapping, greater attention is needed to assure that users understand the tradeoffs between accuracy and precision in creating local information, the imprecision of boundaries, as well as the limits of forecasts. Clearly conveying spatial accuracy and uncertainty is a challenge that merits greater attention in using maps to communicate drought and other environmental risk information. 相似文献
923.
A Conceptual Model for Defining and Assessing Land Management Units Using a Fuzzy Modeling Approach in GIS Environment 总被引:5,自引:0,他引:5
Appropriate land management decisions are important for current and future use of the land to ensure its sustainability. This
requires that land management units (LMUs) be specified to enable the identification of specific parameters employed in decision
making processes. This paper presents the development of a conceptual model, within geographic information systems (GIS),
for defining and assessing LMUs from available biophysical information. The model consists of two main components (sub-models):
land quality-based suitability analysis and soil erosion estimation. Using a fuzzy set methodology, the first sub-model was
constructed to derive a land suitability index (LSI) for a cropping land utilization type. The LSI thus highlights the suitability
grades of every pixel in the study area on a continuous basis. A sub-model of soil erosion was established based on the Revised
Universal Soil Loss Equation (RUSLE) utilising the same spatial data bases employed for structuring the LSI. Using a soil
loss tolerance principle, a fuzzy membership function of average annual soil loss (called soil loss index, SLI) was established,
leading to compatibility between LSI and SLI for data integration. LMUs were then derived from various combinations of LSI
and SLI. The methodology developed shows the significance of the model for refining available land suitability evaluation
systems, which take no account of expected land degradation (from erosion) due to a nominated land use. It also provides a
valuable guideline for cost-effective GIS applications in the identification and assessment of homogeneous land units, using
available spatial information sets, at a finer scale. 相似文献
924.
以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站内1990年设立的长期免耕试验田为研究对象,采用静态暗箱/气相色谱法,对传统的冬水田平作(CT)及由其改良而成的水旱轮作(CTR)、厢作免耕(NTP)和垄作免耕(NTR)等农田生态系统CH4和N2O的排放进行了连续1 a的田间原位观测研究.结果表明,传统的CT处理中,CH4和N2O主要排放时期为水稻种植季,该时期的持续时间仅占全年的27.1%,但2种温室气体的总排放量分别占全年的77.6%和55.0%;耕作制度改良后,CH4排放降低而N2O排放增加.不同耕作方式下CH4的年平均排放通量[以CH4计,mg.(m2.h)-1]为CT(2.96±0.04)〉NTR(1.83±0.21)〉NTP(1.42±0.01)〉CTR(0.96±0.09),CT处理的CH4排放极显著高于CTR和NTP处理(P〈0.01),显著高于NTR处理(P〈0.05);N2O的年平均排放通量[以N2O计,μg.(m2.h)-1]依次为CTR(123.6±47.1)〉NTR(115.2±22.1)〉NTP(100.5±25.8)〉CT(81.3±13.5),CTR处理N2O的排放显著高于CT(P〈0.05).通过对不同时间尺度(20、100及500 a)2种温室气体综合全球增温潜势(global warming potential,GWP)的计算,可以发现,改良后的3种耕作方式对CH4和N2O的综合GWP有一定的减排作用,无论时间尺度长短,4种耕作处理全年所排放的CH4和N2O所产生的综合GWP均为CT〉NTR〉NTP〉CTR.因此,耕作方式的改良对紫色水稻土农田生态系统中CH4和N2O综合GWP减排有着明显的效果. 相似文献
925.
Spatial information in the form of geographical information system coverages and remotely sensed imagery is increasingly used in ecological modeling. Examples include maps of land cover type from which ecologically relevant properties, such as biomass or leaf area index, are derived. Spatial information, however, is not error-free: acquisition and processing errors, as well as the complexity of the physical processes involved, make remotely sensed data imperfect measurements of ecological attributes. It is therefore important to first assess the accuracy of the spatial information being used and then evaluate the impact of such inaccurate information on ecological model predictions. In this paper, the role of geostatistics for mapping thematic classification accuracy through integration of abundant image-derived (soft) and sparse higher accuracy (hard) class labels is presented. Such assessment leads to local indices of map quality, which can be used for guiding additional ground surveys. Stochastic simulation is proposed for generating multiple alternative realizations (maps) of the spatial distribution of the higher accuracy class labels over the study area. All simulated realizations are consistent with the available pieces of information (hard and soft labels) up to their validated level of accuracy. The simulated alternative class label representations can be used for assessing joint spatial accuracy, i.e., classification accuracy regarding entire spatial features read from the thematic map. Such realizations can also serve as input parameters to spatially explicit ecological models; the resulting distribution of ecological responses provides a model of uncertainty regarding the ecological model prediction. A case study illustrates the generation of alternative land cover maps for a Landsat Thematic Mapper (TM) subscene, and the subsequent construction of local map quality indices. Simulated land cover maps are then input into a biogeochemical model for assessing uncertainty regarding net primary production (NPP). 相似文献
926.
浅谈加强环境现场监测规范化建设 总被引:2,自引:0,他引:2
尹卫萍 《环境监测管理与技术》2013,25(2):1-3
分析了环境现场监测存在的质控体系不够完善,监测人员不够专业,监测技术相对落后,管理制度不够健全等问题.提出实现环境现场监测规范化建设,应从完善现场监测质量控制体系入手,加强监测队伍、监测装备、现场监测管理制度建设,改进和提高现场监测技术,以此满足和适应环保新形势对环境现场监测工作的要求. 相似文献
927.
E. P. Gus'kov T. V. Varduni T. P. Shkurat N. P. Milyutina A. V. Mirzoyan 《Russian Journal of Ecology》2000,31(4):245-250
A new method for estimating the genotoxicity of the urban environment is proposed. The method is based on the analysis of
the lipid peroxidation (LPO) rate in leaves of woody plants. The mutagenicity of the urban environment was estimated using
standard test systems, including plant root meristem (kidney beans germinated in water with suspended particles collected
at different points along the Temernik River) and the Ames test (silt samples were tested). Sensitivities of elm, willow,
and poplar leaf meristem cells to unidentified environmental mutagenes were compared. Frequencies of chromosome aberrations
(CAs) in leaves of woody plants growing at different points along the Temernik River within the Rostov-on-Don city districts
differed from those in the control zone. The frequency of CAs was found to correlate with the concentration of LPO products.
This allows a biochemical estimation of the malonic dialdehyde (MDA) concentration in woody plants to be used as an express
test for the mutagenicity of environmental factors. An advantage of the proposed test is the possibility of monitoring the
level of unidentified environmental mutagens over many years, independently of its sporadic temporal variations. 相似文献
928.
929.
利用2013年佛山市8个国控大气自动监测站点ρ(PM_(2.5))监测数据,分析佛山市PM_(2.5)污染的时空分布特征,并诊断诱发PM_(2.5)高污染过程的关键天气类型。结果表明,佛山市2013年PM_(2.5)年均值为53μg/m3,高于国家二级标准,污染主要集中在三水区中部、南海区中部和禅城区北部。佛山市ρ(PM_(2.5))表现出明显的季节变化和日变化特征,秋、冬季是PM_(2.5)的高污染季节,其值夜间略高于白天,呈典型的双峰型分布,08:00—09:00短暂出现一个浓度的小峰值,推测与上班交通高峰有关。对PM_(2.5)持续高污染发生的地面天气形势分析表明,高压出海是诱发佛山市PM_(2.5)高污染事件最主要的天气类型。 相似文献
930.
Real-world fuel consumption of light-duty passenger vehicles using on-board diagnostic (OBD) systems
Xuan Zheng Sheng Lu Liuhanzi Yang Min Yan Guangyi Xu Xiaomeng Wu Lixin Fu Ye Wu 《Frontiers of Environmental Science & Engineering》2020,14(2):33