全文获取类型
收费全文 | 34492篇 |
免费 | 2593篇 |
国内免费 | 7934篇 |
专业分类
安全科学 | 3571篇 |
废物处理 | 695篇 |
环保管理 | 6918篇 |
综合类 | 20897篇 |
基础理论 | 4812篇 |
环境理论 | 10篇 |
污染及防治 | 2712篇 |
评价与监测 | 2191篇 |
社会与环境 | 1971篇 |
灾害及防治 | 1242篇 |
出版年
2024年 | 150篇 |
2023年 | 577篇 |
2022年 | 981篇 |
2021年 | 1170篇 |
2020年 | 1230篇 |
2019年 | 1024篇 |
2018年 | 935篇 |
2017年 | 1212篇 |
2016年 | 1525篇 |
2015年 | 1617篇 |
2014年 | 1769篇 |
2013年 | 2418篇 |
2012年 | 2509篇 |
2011年 | 2686篇 |
2010年 | 1968篇 |
2009年 | 2063篇 |
2008年 | 1574篇 |
2007年 | 2415篇 |
2006年 | 2351篇 |
2005年 | 1922篇 |
2004年 | 1716篇 |
2003年 | 1656篇 |
2002年 | 1388篇 |
2001年 | 1202篇 |
2000年 | 1106篇 |
1999年 | 966篇 |
1998年 | 675篇 |
1997年 | 607篇 |
1996年 | 493篇 |
1995年 | 470篇 |
1994年 | 394篇 |
1993年 | 355篇 |
1992年 | 244篇 |
1991年 | 195篇 |
1990年 | 157篇 |
1989年 | 122篇 |
1988年 | 117篇 |
1987年 | 98篇 |
1986年 | 63篇 |
1985年 | 43篇 |
1984年 | 72篇 |
1983年 | 77篇 |
1982年 | 73篇 |
1981年 | 83篇 |
1980年 | 94篇 |
1979年 | 86篇 |
1978年 | 57篇 |
1977年 | 49篇 |
1973年 | 49篇 |
1971年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
David L. Peterson 《Environmental monitoring and assessment》2000,64(1):81-91
A quantitatively robust yet parsimonious air-quality monitoring network in mountainous regions requires special attention to relevant spatial and temporal scales of measurement and inference. The design of monitoring networks should focus on the objectives required by public agencies, namely: 1) determine if some threshold has been exceeded (e.g., for regulatory purposes), and 2) identify spatial patterns and temporal trends (e.g., to protect natural resources). A short-term, multi-scale assessment to quantify spatial variability in air quality is a valuable asset in designing a network, in conjunction with an evaluation of existing data and simulation-model output. A recent assessment in Washington state (USA) quantified spatial variability in tropospheric ozone distribution ranging from a single watershed to the western third of the state. Spatial and temporal coherence in ozone exposure modified by predictable elevational relationships ( 1.3 ppbv ozone per 100 m elevation gain) extends from urban areas to the crest of the Cascade Range. This suggests that a sparse network of permanent analyzers is sufficient at all spatial scales, with the option of periodic intensive measurements to validate network design. It is imperative that agencies cooperate in the design of monitoring networks in mountainous regions to optimize data collection and financial efficiencies. 相似文献
132.
Several theoretical, analytical, and institutional difficulties have impeded the development and application of the assessment of cumulative environmental impacts. Watershed development on coastal wetlands offers an ideal context for evaluating the land disturbance target approach to cumulative impact assessment. A model land use planning system involving a time series approach was developed for Elkhorn Slough in California. The approach included four major components: evaluation of erosion susceptibility, measurement of land disturbance, establishment of a land disturbance target, and a comparison of existing and target land disturbance values. Further research is needed to test the transferability of the approach in a wide range of coastal watersheds and to verify the applicability of the methods to other cumulative impact problems. 相似文献
133.
红壤丘陵区典型流域地表水水环境特征研究——以浏阳河流域为例 总被引:2,自引:1,他引:2
选取浏阳河流域为例,根据近十年河流断面监测数据,采用改进的综合污染指数法来评价水质污染程度,研究了该红壤丘陵区典型河流水质的时空变化特征,并结合土地利用和土壤特征等分析地表水质变化原因。结果表明,改进的综合污染指数法有较好的适用性;从时间特征上看,由于面源污染加剧,使得浏阳河近十年的水质污染呈增长趋势;从空间特征上看,浏阳河从上游到下游,河流污染呈增长趋势,上游水质较好,中游表现为重金属铅和汞的污染较大,而下游则是氨氮污染加剧。 相似文献
134.
Chris J. Matthews David B. Newton Roger D. Braddock Bofu Yu 《Environmental Modeling and Assessment》2007,12(1):27-41
Recently, the New Morris Method has been presented as an effective sensitivity analysis tool for mathematical models. The
New Morris Method estimates the sensitivity of an output parameter to a given set of input parameters (first-order effects)
and the extent these parameters interact with each other (second-order effects). This method requires the specification of
two parameters (runs and resolution) that control the sampling of the output parameter to determine its sensitivity to various
inputs. The criteria for these parameters have been set on the analysis of a well-behaved analytical function (see Cropp and
Braddock, Reliab. Eng. Syst. Saf. 78:77–83, 2002), which may not be applicable to other physical models that describe complex
processes. This paper will investigate the appropriateness of the criteria from (Cropp and Braddock, 2002) and hence the effectiveness
of the New Morris Method to determine the sensitivity behaviour of two hydrologic models: the Soil Erosion and Deposition
System and Griffith University Representation of Urban Hydrology. In the first case, this paper will separately analyse the
sensitivity of an output parameter on a set of input parameters (first- and second-order effects) for each model and discuss
the physical meaning of these sensitivities. This will be followed by an investigation into the sampling criteria by exploring
the convergence of the sensitivity behaviour for each model as the sampling of the parameter space is increased. By comparing
these trends to the convergence behaviour from Cropp and Braddock (2002), we will determine how well the New Morris Method
estimates the sensitivity for each model and whether the sampling criteria are appropriate for these models. It will be shown
that the New Morris Method can provide additional insight into the functioning of these models, and that, under a different
metric, the sensitivity behaviour of these models does converge confirming the sampling criteria set by Cropp and Braddock. 相似文献
135.
环境样品中 PCBs 的测定 总被引:9,自引:0,他引:9
通过碱解、酸洗、萃取、净化、浓缩、脱硫等步骤处理实际样品,利用毛细管柱GC/ECD进行PCBs的定性和定量.方法定性准确,定量良好,具有较高的回收率.各同系物的方法检出限,水样为0.01~0.08ng/L;土壤样为0.003~0.03μg/kg,可以应用于土壤、沉积物、水样、油样等环境样品中PCBs的测定 相似文献
136.
石墨炉原子吸收光谱法测定海河下游水中痕量镉 总被引:2,自引:0,他引:2
原子吸收光谱法直接测定高盐水中痕量镉时,有很大背景吸收和误差。本文采用络合—萃取技术使共存元素与待测元素分离,既消除了基体干扰,又达到了富集作用,使测定结果准确可靠。 相似文献
137.
高灵敏XRF测定废水中痕量砷 总被引:2,自引:0,他引:2
本文提出了在硫酸介质中,以锌粒还原产生氢化物,溴化铜溶液吸收,微孔滤膜过滤制成薄样,X射线荧光测定水中痕量砷的分析方法。 相似文献
138.
139.
土壤石油类(红外法)标样制作方法的研究 总被引:4,自引:0,他引:4
对我国环境监测用于土壤矿物油污染监测所必备的标准样品制作方法作了探索,尤其对该类标样的液-固态吸附饱和及其浓度平衡关系作了探讨,从理论上保证标样的均匀性和稳定性,为标样最后的定值分析提供依据. 相似文献
140.
离子色谱分析中的几个问题探讨 总被引:7,自引:0,他引:7
在掌握离子色谱技术最新发展动态的基础上,对离子色谱的新进展、前处理新技术、常用的改善分离度方法、若干注意事项、常遇到的问题等进行了分析探讨,以期用离子色谱技术更多更好地解决实际问题. 相似文献