全文获取类型
收费全文 | 2766篇 |
免费 | 610篇 |
国内免费 | 483篇 |
专业分类
安全科学 | 1261篇 |
废物处理 | 58篇 |
环保管理 | 509篇 |
综合类 | 1305篇 |
基础理论 | 195篇 |
污染及防治 | 188篇 |
评价与监测 | 67篇 |
社会与环境 | 96篇 |
灾害及防治 | 180篇 |
出版年
2024年 | 16篇 |
2023年 | 77篇 |
2022年 | 142篇 |
2021年 | 165篇 |
2020年 | 155篇 |
2019年 | 168篇 |
2018年 | 127篇 |
2017年 | 153篇 |
2016年 | 201篇 |
2015年 | 208篇 |
2014年 | 145篇 |
2013年 | 166篇 |
2012年 | 265篇 |
2011年 | 217篇 |
2010年 | 176篇 |
2009年 | 169篇 |
2008年 | 122篇 |
2007年 | 193篇 |
2006年 | 160篇 |
2005年 | 108篇 |
2004年 | 85篇 |
2003年 | 84篇 |
2002年 | 76篇 |
2001年 | 67篇 |
2000年 | 56篇 |
1999年 | 35篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 25篇 |
1995年 | 30篇 |
1994年 | 31篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 11篇 |
1971年 | 9篇 |
1970年 | 6篇 |
排序方式: 共有3859条查询结果,搜索用时 46 毫秒
961.
活性危害的评估由理论筛选,热稳定性的实验筛选,动力学参数的检测装置,紧急排放系统的设计、筛选和放大,过程设计和优化等几个部分组成. 相似文献
962.
Groundwater remediation technologies, such as pump-and-treat (PTS) and funnel-and-gate systems (FGS), aim at reducing locally appearing contaminations. Therefore, these methodologies are basically evaluated with respect to their capability to yield local improvements of an environmental situation, commonly neglecting that their application is also associated with secondary impacts. Life cycle assessment (LCA) represents a widely accepted method of assessing the environmental aspects and potential impacts related to a product, process or service. This study presents the set-up of a LCA framework in order to compare the secondary impacts caused by two conceptually different technologies at the site of a former manufactured gas plant in the city of Karlsruhe, Germany. As a FGS is already operating at this site, a hypothetical PTS of the same functionality is adopted. During the LCA, the remediation systems are evaluated by focusing on the main technical elements and their significance with respect to resource depletion and potential adverse effects on ecological quality, as well as on human health. Seven impact categories are distinguished to address a broad spectrum of possible environmental loads. A main point of discussion is the reliability of technical assumptions and performance predictions for the future. It is obvious that a high uncertainty exists when estimating impact specific indicator values over operation times of decades. An uncertainty analysis is conducted to include the imprecision of the underlying emission and consumption data and a scenario analysis is utilised to contrast various possible technological variants. Though the results of the study are highly site-specific, a generalised relative evaluation of potential impacts and their main sources is the principle objective rather than a discussion of the calculated absolute impacts. A crucial finding that can be applied to any other site is the central role of steel, which particularly derogates the valuation of FGS due to the associated emissions that are harmful to human health. In view of that, environmental credits can be achieved by selecting a mineral-based wall instead of sheet piles for the funnel construction and by minimising the steel consumption for the gate construction. Granular activated carbon (GAC) is exclusively considered as the treatment material, both in-situ and on-site. Here it is identified as an additional main determinant of the relative assessment of the technologies since it is continuously consumed. 相似文献
963.
针对煤层开采后常出现矿压显现剧烈、煤岩透气性增大和地表下沉等问题,利用二维相似模拟试验研究综放工作面覆岩破坏特征并通过分形理论表征裂隙演化规律.试验结果表明:煤层基本顶初次来压步距为78 m,周期来压步距为24 m;煤层采动裂隙发育,距煤层顶板超过35 m;煤层开采后形成的覆岩裂隙具有分形特征,其分形维数随工作面的推进... 相似文献
964.
Zeng Weihua Zhong Xiaohong Xue Pengli . State Key Laboratory of Water Environment Simulation School of Environment Beijing Normal University Beijing China . China’s Academy of Environmental Planning State Environmental Protection Administration Beijing 《中国人口.资源与环境(英文版)》2008,6(3):63-72
Intergenerational conflict coordination is the fundamental requirement and core of sustainable development. In this paper, through the analysis of the future generations-oriented management mechanisms for intergenerational conflict, the idea of mechanisms and institution building for the coordination and management of intergenerational conflict is put forward. Furthermore, the future generations-oriented virtual negotiation support system (NSS) for intergenerational conflict is developed, built on the analysis of the process simulation of intergenerational wealth transfer, intergenerational equilibrium allocation of resources, and strategies for the mitigation and avoidance of intergenerational conflict, through the application of advanced IT technology. The virtual NSS for intergenerational conflict is helpful to the practical application of the sustainable development theory; on the other hand, it can be applied directly to the intergenerational equilibrium allocation of resources, national economic accounting, formulation of sustainable development strategies and other urgent national economic and social development issues. Finally, the sustainable development theory can be enriched and extended. Therefore, the development of the future generations-oriented virtual NSS for intergenerational conflict has certain theoretical and practical effects on the theory of sustainable development. 相似文献
965.
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
966.
967.
Stephan J. Nix S. Rocky. Durrans 《Journal of the American Water Resources Association》1996,32(6):1329-1340
ABSTRACT: This paper looks at the use of off-line detention systems as a means of stormwater management. Conventional detention basins are typically designed and built as in-line systems in which all runoff is directed to the basin. Off-line systems are designed so that only a portion of the runoff is directed to the basin. Several simulation experiments were run to examine the behavior of in-line and off-line systems designed to reduce the peak flow from a developed area to the pre-development level. The results demonstrate that off-line systems require considerably less storage than in-line systems to achieve the same management goal. The results also show that off-line and in-line systems have significantly different flow-duration characteristics with the off-line system generally producing lower flows over longer periods. Unfortunately, off-line systems may exacerbate downstream flooding problems, especially when used in the upper portions of a watershed. Nevertheless, an off-line system can be an alternative to in-line detention in many cases. 相似文献
968.
Naoufel Benrachi Mohamed Ouzzane Arezki Smaili Louis Lamarche Messaoud Badache Wahid Maref 《International Journal of Green Energy》2020,17(2):115-126
ABSTRACTThermal potential for cooling and heating can be achieved by new configuration of earth–air heat exchanger (EAHE). This paper presents a numerical investigation of thermal performance of a spiral-shaped configuration of EAHE intended for the summer cooling in hot and arid regions of Algeria. A commercial finite volume software (ANSYS FLUENT) has been used to carry out the transient three-dimensional simulations and the obtained results have been validated using the experimental and numerical data obtained from the literature. The agreement between our simulation results and those from literature is very satisfactory. A parametric analysis of the new geometry of (EAHE) has been performed to investigate the effect of pitch, depth, pipe length and of the flow velocity on the outlet air temperature and the EAHE’s mean efficiency as well as its coefficient of performance (COP). It has been shown that when the pitch space varies between 0.2 and 2 m the difference of outlet air temperature increases by 6 °C. When the air velocity increases from 2 to 5 m/s the mean efficiency decreases from 60 % to 33 % and the COP of the EAHE decreases from 2.84 to 0.46. 相似文献
969.
William E. Sopper L. A. V. Hiemstra 《Journal of the American Water Resources Association》1970,6(5):754-766
A mathematical model was developed to simulate the hydrologic behavior of five small watersheds in central Pennsylvania. Continuous hydrographs for the 6-month period, April to September 1964, were simulated. Synthesized rainfall cycles consisting of increasing rainfall by 10, 20, and 30 percent to simulate the effects of cloud seeding were processed through the watershed model to determine the effects on low flow augmentation. Other rainfall cycles used consisted of increasing every third storm by 30 percent and of developing a rainfall cycle by processing daily radiosonde data through a mathematical cumulus cloud model to obtain a prediction of rainfall following seeding. A comparison of actual and predicted hydrographs indicated that simulated cloud seeding resulted in significant monthly and seasonal water yields. In general, the results of the study appear to indicate that on a theoretical basis cloud seeding would be a feasible method of augmenting low stream-flow during the summer months on watersheds in the northern Appalachian region. 相似文献
970.
Water quality must be considered in the development and planning aspects of water resource management. To accomplish this, the decision-maker needs to have at his disposal a systematized procedure for simulating water quality changes in both time and space. The simulation model should be capable of representing changes in several parameters of water quality as they are influenced by natural and human factors impinging on the hydrologic system. The objective of this work is two-fold. The first goal is to demonstrate the feasibility of developing and utilizing a water quality simulation model in conjunction with a hydrologic simulation model. The model represents water quality changes in both time and space in response to changing atmospheric and hydrologic conditions and time-varying waste discharges at various points in the system. This model has been developed from and verified with actual field data from a prototype system selected for this purpose. The second aim is to set forth procedural guidelines to assist in the development of water quality simulation models as tools for use in the quality-quantity management of a hydrologic unit. 相似文献