全文获取类型
收费全文 | 2688篇 |
免费 | 167篇 |
国内免费 | 162篇 |
专业分类
安全科学 | 253篇 |
废物处理 | 30篇 |
环保管理 | 1013篇 |
综合类 | 756篇 |
基础理论 | 435篇 |
环境理论 | 2篇 |
污染及防治 | 196篇 |
评价与监测 | 197篇 |
社会与环境 | 95篇 |
灾害及防治 | 40篇 |
出版年
2024年 | 6篇 |
2023年 | 36篇 |
2022年 | 37篇 |
2021年 | 70篇 |
2020年 | 104篇 |
2019年 | 59篇 |
2018年 | 43篇 |
2017年 | 84篇 |
2016年 | 100篇 |
2015年 | 96篇 |
2014年 | 116篇 |
2013年 | 121篇 |
2012年 | 105篇 |
2011年 | 168篇 |
2010年 | 99篇 |
2009年 | 203篇 |
2008年 | 133篇 |
2007年 | 141篇 |
2006年 | 124篇 |
2005年 | 115篇 |
2004年 | 94篇 |
2003年 | 119篇 |
2002年 | 109篇 |
2001年 | 77篇 |
2000年 | 102篇 |
1999年 | 87篇 |
1998年 | 65篇 |
1997年 | 38篇 |
1996年 | 50篇 |
1995年 | 46篇 |
1994年 | 27篇 |
1993年 | 36篇 |
1992年 | 26篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1974年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有3017条查询结果,搜索用时 15 毫秒
741.
我国城市生态承载力研究进展 总被引:1,自引:0,他引:1
从生态承载力角度研究区域资源-生态-环境问题,是当今生态学、地理学和经济学等学科研究的热点与前沿领域之一。依据现有研究成果,阐述了承载力的概念和什么是城市生态承载力,并对生态承载力的研究方法、研究趋势及其研究存在的问题和方法途径及提高城市生态承载力的对策建议进行了简述。 相似文献
742.
Medilanski E Chuan L Mosler HJ Schertenleib R Larsen TA 《Environmental management》2007,39(5):648-662
We conducted a study of the institutional barriers to introducing urine source separation in the urban area of Kunming, China.
On the basis of a stakeholder analysis, we constructed stakeholder diagrams showing the relative importance of decision-making
power and (positive) interest in the topic. A hypothetical decision-making process for the urban case was derived based on
a successful pilot project in a periurban area. All our results were evaluated by the stakeholders. We concluded that although
a number of primary stakeholders have a large interest in testing urine source separation also in an urban context, most of
the key stakeholders would be reluctant to this idea. However, the success in the periurban area showed that even a single,
well-received pilot project can trigger the process of broad dissemination of new technologies. Whereas the institutional
setting for such a pilot project is favorable in Kunming, a major challenge will be to adapt the technology to the demands
of an urban population. Methodologically, we developed an approach to corroborate a stakeholder analysis with the perception
of the stakeholders themselves. This is important not only in order to validate the analysis but also to bridge the theoretical
gap between stakeholder analysis and stakeholder involvement. We also show that in disagreement with the assumption of most
policy theories, local stakeholders consider informal decision pathways to be of great importance in actual policy-making. 相似文献
743.
The restoration of degraded systems is essential for maintaining the provision of valuable ecosystem services, including the
maintenance of aesthetic values. However, restoration projects often fail to reach desired goals for a variety of ecologic,
financial, and social reasons. Feasibility studies that evaluate whether a restoration effort should even be attempted can
enhance restoration success by highlighting potential pitfalls and gaps in knowledge before the design phase of a restoration.
Feasibility studies also can bring stakeholders together before a restoration project is designed to discuss potential disagreements.
For these reasons, a feasibility study was conducted to evaluate the efficacy of restoring a tidal freshwater marsh in the
Potomac River near Alexandria, Virginia. The study focused on science rather than engineering questions, and thus differed
in approach from other feasibility studies that are mostly engineering driven. The authors report the framework they used
to conduct a feasibility study to inform other potential restoration projects with similar goals. The seven steps of the framework
encompass (1) initiation of a feasibility study, (2) compilation of existing data, (3) collection of current site information,
(4) examination of case studies, (5) synthesis of information in a handbook, (6) meeting with selected stakeholders, and (7)
evaluation of meeting outcomes. By conducting a feasibility study using the seven-step framework, the authors set the stage
for conducting future compliance studies and enhancing the chance of a successful restoration. 相似文献
744.
黑河流域磷迁移转化过程连续模拟研究 总被引:3,自引:2,他引:1
以西安市的主要供水水源黑河流域为例,在Matlab软件辅助下,使用蓄满产流模型、逆高斯分布汇流模型、水沙关系模型以及澳大利亚学者Viney所提出的营养物迁移转化模型对黑河流域1981~1990年磷的迁移转化过程进行了连续模拟,模拟了磷的输出情况,预测了黑河流域磷污染负荷量.结果表明:模拟结果符合磷素流失的一般规律,年径流量大的年份,从流域输出的磷素也较多,反之,则较小;对磷的连续模拟结果与实测插补延长后总磷年负荷量的相对误差基本上在±30%以内,结果较合理,由此表明该法可用于黑河流域磷素迁移转化的连续模拟.同时,本文模型只是流域非点源污染连续模拟的初步尝试,尚需进行进一步检验、改进和完善. 相似文献
745.
The recently-adopted global Sustainable Development Goals (SDGs) will have significant implications for national development planning in both developed and developing countries in the post-2015 period to 2030. Integrated, nationally-owned SDG strategies will be at the centre of national efforts to implement the new sustainable development agenda. The long-run processes and systems perspective that are inherent in the SDGs present complex analytical problems for policymakers and analysts. Scenario analysis and quantitative modelling will be important analytical tools to support national sustainable development planning, and there is an increasingly sophisticated suite of models available to decision makers. This paper reviews and assesses a broad range of different quantitative models that have the potential to support national development planning for the SDGs. The study develops a typology and inventory of 80 different models, and then reviews the comparative strengths, weaknesses and general utility of different models through an initial screening and subsequent multi-criteria analysis of short-listed models. Current gaps in model capabilities are highlighted in the context of providing analytical support for national development planning for the SDGs. While some existing models are particularly relevant, it is unlikely that an ideal model can analyse all SDG targets and variables of interest within a single modelling framework. Top-down ‘macro framework’ models are likely to be more useful for undertaking system-level or economy-wide scenario analysis driven by the national long-term goals and targets, and for exploring trade-offs and synergies among sectors. Bottom-up sectoral models will be able to support far more detailed option-level impact analysis of concrete interventions, technologies and investments. Combining both approaches within an analytical framework will provide a robust approach for analysis and decision-making. The results highlight a range of potential gaps in current modelling capabilities, and provide some new tools to assist with model selection. 相似文献
746.
747.
Hideo Nakajima Akihiko Hirooka Jiro Takemura Miguel A. Mario 《Journal of the American Water Resources Association》1998,34(6):1415-1425
ABSTRACT: One-dimensional contaminant transport through a saturated soil is modeled using a 1.2-m radius geotechnical centrifuge. Small-scale physical modeling in the centrifuge is achieved in relatively short time, at stress distributions that are similar to those experienced in the prototype (actual site). A 0.05 mol/l of sodium chloride solution is used as a contaminant and conductivity cells measure the concentration of the contaminant throughout the porous medium. Scaling analysis for centrifuge modeling and 1-g modeling are briefly discussed and it is concluded that centrifuge modeling simulates the effect of molecular diffusion; however, scaling of the effect of mechanical dispersion may be violated in the centrifuge if the interstitial fluid velocity is high. Centrifuge test results show good agreement with the predicted relationship between the coefficient of hydrodynamic dispersion and the Peclet number using column tests. Centrifuge modeling can be used as a complement of numerical modeling although the effect of mechanical dispersion may be overestimated in the former. 相似文献
748.
Truck and bus frontal impacts account for a major proportion of pedestrian fatalities in many less motorized countries. To understand this phenomenon, we have collected injury data on pedestrian impacts with buses and trucks and performed computer simulations to identify critical design parameters at 15–45 km/h impact velocities for further investigation. A male dummy which was scaled to fifty percentile Indian dimensions has been used for simulations using MADYMO. Bumper height, bumper offset and grille inclination affect the pelvis and thorax forces and Head Injury Criterion values critically. Bumper width has less effect. Simulations were performed to optimize for the above–mentioned three parameters. Changes in front geometric parameters reduce injury to the upper body and head below safety limits for the existing force–displacement properties but do not affect leg injuries significantly. Hence bumpers need to be made less stiff. Injury data shows that pedestrians also sustain tibia fractures in bus/truck impacts in apparent low velocity impacts. The computer modeling does not offer adequate explanation for this phenomenon. These simulations confirm that it is theoretically possible to make truck/bus fronts safer for pedestrians in impacts up to 35 km/h. 相似文献
749.
Phillip P. Emmerth David R. Bayne 《Journal of the American Water Resources Association》1996,32(1):145-154
ABSTRACT: West Point Lake is a 10,360 ha mainstream impoundment of the Chattahoochee River located 95 kilometers downstream of Atlanta, Georgia. Origins and magnitude of external total phosphorus (TP) and total suspended solids (TSS) loads from the West Point Lake basin were estimated over a one-year period. Partitioning the drainage basin allowed the sources of these loads to be determined. The upper subbasin area, from Franklin, Georgia, to the headwaters of the Chattahoochee River, contributed 96 percent of the discharge and 97 percent of the TP and TSS loads into West Point Lake. The lower subbasin area, from Franklin to West Point Lake dam, only contributed 3 percent of the TP and TSS loads. Ninety-one percent and 87 percent of the TP and TSS loads, respectively, from the upper subbasin originated from the Atlanta area. Point sources discharged 70 percent and 3 percent of the upper subbasin TP and TSS loads, respectively. A large portion (66 percent) of the TP from the upper subbasin was in the bioavailable form. 相似文献
750.
Jonathan B. Butcher 《Journal of the American Water Resources Association》1996,32(2):349-356
ABSTRACT: Kriging methods of geostatistical analysis provide valuable techniques for analysis of sediment contamination problems, including interpolation of concentration maps from point data and estimation of global mean concentrations. Sample collection efforts frequently include preliminary screening data of considerably more extensive coverage than the laboratory analyses on which estimation is usually based. How should these be incorporated in kriging? Screening and laboratory analysis constitute two separate estimates of the same spatial field but of very different characteristics. A modified version of co-kriging is developed to include the imprecise screening information in the analysis of contaminant distribution. Use of the method is demonstrated on a data set of sediment PCB samples from the Upper Hudson River, for which preliminary categorical mass spectrometry screening was used to select a smaller set of samples for gas chromatograph analysis. The method is widely applicable to many situations of contaminant and natural resource estimation. 相似文献