全文获取类型
收费全文 | 3803篇 |
免费 | 149篇 |
国内免费 | 238篇 |
专业分类
安全科学 | 238篇 |
废物处理 | 30篇 |
环保管理 | 1073篇 |
综合类 | 1456篇 |
基础理论 | 241篇 |
环境理论 | 1篇 |
污染及防治 | 306篇 |
评价与监测 | 589篇 |
社会与环境 | 191篇 |
灾害及防治 | 65篇 |
出版年
2023年 | 60篇 |
2022年 | 56篇 |
2021年 | 94篇 |
2020年 | 134篇 |
2019年 | 74篇 |
2018年 | 75篇 |
2017年 | 111篇 |
2016年 | 139篇 |
2015年 | 141篇 |
2014年 | 163篇 |
2013年 | 205篇 |
2012年 | 175篇 |
2011年 | 292篇 |
2010年 | 116篇 |
2009年 | 247篇 |
2008年 | 233篇 |
2007年 | 233篇 |
2006年 | 192篇 |
2005年 | 146篇 |
2004年 | 130篇 |
2003年 | 141篇 |
2002年 | 116篇 |
2001年 | 101篇 |
2000年 | 94篇 |
1999年 | 91篇 |
1998年 | 86篇 |
1997年 | 67篇 |
1996年 | 46篇 |
1995年 | 59篇 |
1994年 | 70篇 |
1993年 | 45篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1976年 | 5篇 |
1973年 | 8篇 |
1972年 | 5篇 |
1971年 | 10篇 |
排序方式: 共有4190条查询结果,搜索用时 15 毫秒
381.
干旱区城市水资源开发与环境保护 总被引:1,自引:0,他引:1
水资源是干旱区生态环境中最活跃的因子,城市是自然系统与人工系统耦合成的大系统,也是地下水高度集中开发的地区。地下水是干旱区城市的主要供水水源。文章从内蒙古自治区城市水资源供需现状出发,阐述了城市水资源开发带来的环境问题,重点探讨了城市地下水超采对周边地区环境的影响。最后提出了城市水资源开发与环境保护对策措施。 相似文献
382.
The transition in Dutch water management 总被引:1,自引:1,他引:1
Over the past decades, the Dutch people have been confronted with severe water-related problems, which are the result of an unsustainable water system, arising from human interventions in the physical infrastructure of the water system and the water management style. The claims of housing, industry, infrastructure and agriculture have resulted in increasing pressure on the water system. The continuous subsidence of soil and climate change has put pressure on the land. Hence, the nature and magnitude of water-related problems have changed. Longitudinal research of relevant national policy documents reveals that the water management regime has changed its water management style over the past 30 years from a technocratic scientific style towards an integral and participatory style. We have investigated if the historical development in Dutch Water management can be characterized as a transition. Based on longitudinal research through an integrated systems analysis, document research and expert interviews, we have reconstructed the historical narrative by using the transition concepts of multi-level and multi-phase. This research indicates that the shift in Dutch Water management can be characterized as a transition. This transition is currently in the take-off stage and near the acceleration stage. This is a crucial stage as long as the considerable gap between the strategic macro-vision and the practical implementation at the micro-level remains. As long as these levels are not compatible (modulation), the transition will not be completed successfully. Transition management as multi-level governance model should therefore be adopted to facilitate the modulation. 相似文献
383.
MPT—AES法测定矿泉水中硅、镁、钙、锶、钾元素 总被引:2,自引:0,他引:2
应用MPT-AES法测定了四种矿泉水中的Si,Mg,Ca,K五种元素,实验证明该方法具有分析速度快,准确度及精密度高等优点。 相似文献
384.
385.
草履虫──针杆藻群落对混合印染废水净化作用的条件实验 总被引:2,自引:0,他引:2
本文对混合印染废水的静态净化过程,进行了生物群落观察和条件实验。发现废水净化初期以大量细菌和草履虫(以 P. Caudatum为主)繁殖为特征,同时伴生着少量浮游藻类。随着净化过程的进行,细菌和草履虫数量下降,以针杆藻(以 S. aucs为主)为建群种的浮游藻类群落占优势。化学分析表明,净化作用与温度、光照条件及废水起始浓度有关。 相似文献
386.
水体重金属污染生物监测的研究进展 总被引:12,自引:3,他引:12
综述了重金属的毒性效应和水体重金属污染的现状,介绍了利用水生藻类、浮游动物群落和底栖动物监测水体重金属污染的研究进展及发展趋势。 相似文献
387.
The long-term water quality monitoring program implemented by the Massachusetts Water Resources Authority in 1992 is extensive
and has provide substantial understanding of the seasonality of the waters in both Boston Harbor and Massachusetts Bay and
the response to improvements in effluent quality and offshore transfer of the effluent in September 2000. The monitoring program
was designed with limited knowledge of spatial and temporal variability and long-term trends within the system. This led to
an extensive spatial and temporal sampling program. The data through 2003 showed high correlation within physical parameters
measured (e.g., salinity, dissolved oxygen) and in biological measures such as chlorophyll fluorescence. To address the potential
sampling redundancies in the measurement program, an assessment of the impact of reduced levels of monitoring on the ability
to make water quality decisions was completed. The optimization was conducted by applying statistical models that took into
account whether there was evidence of a seasonal pattern in the data. The optimization used model survey average readings
to identify temporal fixed effects, model survey-average-corrected individual station readings to identify spatial fixed effects,
corrected the individual station readings for temporal and spatial fixed effects and derived a correlation model for the corrected
data, and applied the correlation model to characterize the correlation of annual average readings from reduced monitoring
programs with true parameter levels. Reductions in the number of sampling stations were found less detrimental to the quality
of the data for annual decision-making than reductions in the number of surveys per year, although there is less of a difference
in this regard for dissolved oxygen than there is for chlorophyll. The analysis led to recommendations for a substantially
lower monitoring effort with minimal loss of information. The recommendation supported an annual budget savings of approximately
$183,000. Most of the savings was from fewer surveys as approximately $21,000 came from the reduction in the number of stations
monitored from 21 to 7 and associated laboratory analytical costs. 相似文献
388.
Bustamante J Pacios F Díaz-Delgado R Aragonés D 《Journal of environmental management》2009,90(7):2219-2225
We have used Landsat-5 TM and Landsat-7 ETM+ images together with simultaneous ground-truth data at sample points in the Doñana marshes to predict water turbidity and depth from band reflectance using Generalized Additive Models. We have point samples for 12 different dates simultaneous with 7 Landsat-5 and 5 Landsat-7 overpasses. The best model for water turbidity in the marsh explained 38% of variance in ground-truth data and included as predictors band 3 (630–690 nm), band 5 (1550–1750 nm) and the ratio between bands 1 (450–520 nm) and 4 (760–900 nm). Water turbidity is easier to predict for water bodies like the Guadalquivir River and artificial ponds that are deep and not affected by bottom soil reflectance and aquatic vegetation. For the latter, a simple model using band 3 reflectance explains 78.6% of the variance. Water depth is easier to predict than turbidity. The best model for water depth in the marsh explains 78% of the variance and includes as predictors band 1, band 5, the ratio between band 2 (520–600 nm) and band 4, and bottom soil reflectance in band 4 in September, when the marsh is dry. The water turbidity and water depth models have been developed in order to reconstruct historical changes in Doñana wetlands during the last 30 years using the Landsat satellite images time series. 相似文献
389.
Kristin Floress Jean C. Mangun Mae A. Davenport Karl W.J. Williard 《Journal of the American Water Resources Association》2009,45(6):1352-1360
Floress, Kristin, Jean C. Mangun, Mae A. Davenport, and Karl W.J. Williard, 2009. Constraints to Watershed Planning: Group Structure and Process. Journal of the American Water Resources Association (JAWRA) 45(6):1352‐1360. Abstract: The roles that agencies and other partners play in collaborative watershed management are not always clearly identified. Key factors contributing to group‐level outcomes in watershed groups include both structural and procedural elements. Structural elements include membership systems, project partners, and funding, while procedural elements include leadership, shared vision, and mission development. The current research reports on a case study conducted with a Midwestern watershed group that received Clean Water Act Section 319 funds to undertake a watershed planning process. Data come from focus groups, interviews, public comments, and meeting observation, and were analyzed using grounded theory. Findings of this study indicate that homogenous skill set, discord over group and partner roles, and failed problem identification contributed to the organizational inertia experienced by the watershed group. Implications of this research for groups receiving 319 funds are provided. 相似文献
390.
综合多学科、多领域,从生物物理、社会经济和人类健康等方面综合考虑,建立了天津市景观河流健康评价指标体系,包括6个因素24个指标。评估了水生态健康程度。寻求人为压力与天津城市河流水生态系统变化之间的联系,识别河流受损原因.验证河流管理措施的有效性,对有效保障水生态安全、科学治水、综合利用水资源等均具有一定的科学指导作用。 相似文献