全文获取类型
收费全文 | 1767篇 |
免费 | 175篇 |
国内免费 | 329篇 |
专业分类
安全科学 | 723篇 |
废物处理 | 32篇 |
环保管理 | 139篇 |
综合类 | 890篇 |
基础理论 | 131篇 |
污染及防治 | 94篇 |
评价与监测 | 63篇 |
社会与环境 | 87篇 |
灾害及防治 | 112篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 37篇 |
2021年 | 80篇 |
2020年 | 81篇 |
2019年 | 68篇 |
2018年 | 49篇 |
2017年 | 71篇 |
2016年 | 97篇 |
2015年 | 123篇 |
2014年 | 109篇 |
2013年 | 118篇 |
2012年 | 188篇 |
2011年 | 191篇 |
2010年 | 155篇 |
2009年 | 132篇 |
2008年 | 86篇 |
2007年 | 132篇 |
2006年 | 109篇 |
2005年 | 82篇 |
2004年 | 62篇 |
2003年 | 39篇 |
2002年 | 33篇 |
2001年 | 40篇 |
2000年 | 25篇 |
1999年 | 26篇 |
1998年 | 15篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2271条查询结果,搜索用时 343 毫秒
171.
William W-G. Yeh Chuching Wang 《Journal of the American Water Resources Association》1987,23(4):569-580
ABSTRACT: This paper presents a method for estimating aquifer dispersivities in solute transport models. Sensitivity equations are derived for the calculation of sensitivity coefficients. A modified Gauss-Newton algorithm is used to perform the least-squares minimization. A statistical procedure is outlined to assess reliability of the estimated parameters. The solute transport model is solved by the upstream weighted, multiple cell balance method which combines the concepts of local mass balance and finite element approximations. A one-dimensional solute transport problem in a vertical column system is first used to illustrate the inverse technique. A second example considers the parameter identification problem for three-dimensional solute transport with a unidirectional steady and uniform flow field. The third example solves the parameter identification problem in a three-dimensional, stream-aquifer, solute transport system with steady state flow. Numerical experiments are conducted to study data requirements for parameter identification. 相似文献
172.
The objective of the project was to identify all hazardous waste sites in Burlington County, New Jersey that could be detected on existing, medium-scale aerial photographs of the county. The complete set of over 1000 black- and-white stereopairs at a scale of 1:12,000 was carefully examined for initial identification of possible sites. All suspicious sites were examined again on color transparencies of the county at the same 1:12,000 scale. Out of the 1094 black- and-white photos, 250 required further checking on color transparencies using a zoom stereoscope. This examination resulted in a final identification of 67 sites, the locations of which were delineated on 1:24,000 USGS maps. The use of air photo interpretation techniques provided an effective procedure for identifying waste sites quickly as well as providing a useful demonstration program for county and state officials. 相似文献
173.
It is common to use the results of various solid-phase and aqueous-fraction toxicity tests as part of the decision-making
process for selecting disposal options for dredged sediments. The mere presence of toxicity, however, does not provide a logical
basis for selecting economical, environmentally protective disposal techniques. To achieve this, it is necessary to be able
to identify specific compounds responsible for sediment toxicity. Toxicity identification evaluation (TIE) procedures, originally
developed for complex effluents, represent a useful approach for identifying acutely toxic compounds in dredged materials.
Herein we present a conceptual overview for TIE use in part of the decision-making framework for selecting dredged material
disposal options; included are discussions concerning appropriate test fractions and species for TIE analyses, and specific
TIE manipulations useful for ascertaining whether toxicity is due to any of a number of common sediment contaminants including
ammonia, hydrogen sulfide, metals, or nonpolar organics. 相似文献
174.
根据毕节地区16个主要造林树种的生态生物学特性,结合本区气候和土壤生态条件,运用 Fuzzy 二级评价模型,对各土类水土保持树种的适宜程度进行了综合评价。 相似文献
175.
DEVELOPMENT OF WATERSIIED MODELS FOR TWO SIERRA NEVADA BASINS USING A GEOGRAPHIC INFORMATION SYSTEM1
Anne E. Jeton J. LaRue. Smith 《Journal of the American Water Resources Association》1993,29(6):923-932
ABSTRACT: Techniques were developed using vector and raster data in a geographic information system (GIS) to define the spatial variability of watershed characteristics in the north-central Sierra Nevada of California and Nevada and to assist in computing model input parameters. The U.S. Geological Survey's Precipitation-Runoff Modeling System, a physically based, distributed-parameter watershed model, simulates runoff for a basin by partitioning a watershed into areas that each have a homogeneous hydrologic response to precipitation or snowmelt. These land units, known as hydrologic-response units (HRU's), are characterized according to physical properties, such as altitude, slope, aspect, land cover, soils, and geology, and climate patterns. Digital data were used to develop a GIS data base and HRIJ classification for the American River and Carson River basins. The following criteria are used in delineating HRU's: (1) Data layers are hydrologically significant and have a resolution appropriate to the watershed's natural spatial variability, (2) the technique for delineating HRU's accommodates different classification criteria and is reproducible, and (3) HRU's are not limited by hydrographic-subbasin boundaries. HRU's so defined are spatially noncontiguous. The result is an objective, efficient methodology for characterizing a watershed and for delineating HRU's. Also, digital data can be analyzed and transformed to assist in defining parameters and in calibrating the model. 相似文献
176.
邓民宪 《防灾减灾工程学报》1999,(2)
根据震害调查分析和试验研究结果,建立了由环境因素和管道结构参数组成的,对架空管道震害预测进行二级多因素模糊综合评判的方法。文中给出了计算、评价构成二级评判因素地震烈度、场地类型、工作状态和结构种类各档次正态模糊数范数ak的参数和对实际情况如何确定的方法。本文为面广量大的已建架空管道的震害预测工作提供了一套科学性强,方便实用的计算方法。 相似文献
177.
178.
This paper describes a fuzzy hierarchical analytic approach to determine the weighting of subjective judgments. In addition,
it presents a nonadditive fuzzy integral technique to evaluate a green engineering industry case as a fuzzy multicriteria
decision-making (FMCDM) problem. When the investment strategies are evaluated from various aspects, such as economic effectiveness,
technical feasibility, and environmental regulation, it can be regarded as an FMCDM problem. Since stakeholders cannot clearly
estimate each considered criterion in terms of numerical values for the anticipated alternatives/strategies, fuzziness is
considered to be applicable. Consequently, this paper uses triangular fuzzy numbers to establish weights and anticipated achievement
values. By ranking fuzzy weights and fuzzy synthetic utility values, we can determine the relative importance of criteria
and decide the best strategies. This paper applies what is called a λ fuzzy measure and nonadditive fuzzy integral technique
to evaluate the synthetic performance of green engineering strategies for aquatic products processors in Taiwan. In addition,
we demonstrate that the nonadditive fuzzy integral is an effective evaluation and appears to be appropriate, especially when
the criteria are not independent. 相似文献
179.
岷江流域地表水水质的模糊综合评价 总被引:1,自引:1,他引:1
岷江是长江上游的一个重要支流,其水质安全对维持成都平原正常的生产生活起着至关重要的作用。采用模糊综合评价的方法,对岷江流域14个地表水监测断面的水质状况进行了综合评价。结果表明:在14个监测断面中,处于清洁和未污染程度的断面占50%,主要位于岷江流域的上游和下游,其水质状况较好;处于重污染的断面占29%,主要位于岷江流域的中游,水质状况较差。因此,需要加强流域综合治理尤其是对岷江中游的治理,以确保岷江流域的水质安全。 相似文献
180.
在实地调查和与专家访谈的基础上设计函调问卷,通过对函调问卷的综合分析,构建模糊评价模型,对西递旅游与社区经济互动持续发展水平做出评判。结果表明,西递旅游与社区经济处在基本可持续发展阶段,但也存在着一些制约旅游与社区经济互动持续发展的因素。在此基础上,提出促进西递旅游与社区经济互动持续发展的建议和措施。 相似文献