全文获取类型
收费全文 | 1980篇 |
免费 | 249篇 |
国内免费 | 396篇 |
专业分类
安全科学 | 415篇 |
废物处理 | 44篇 |
环保管理 | 512篇 |
综合类 | 908篇 |
基础理论 | 246篇 |
环境理论 | 4篇 |
污染及防治 | 146篇 |
评价与监测 | 110篇 |
社会与环境 | 131篇 |
灾害及防治 | 109篇 |
出版年
2024年 | 9篇 |
2023年 | 51篇 |
2022年 | 63篇 |
2021年 | 97篇 |
2020年 | 99篇 |
2019年 | 84篇 |
2018年 | 66篇 |
2017年 | 106篇 |
2016年 | 149篇 |
2015年 | 144篇 |
2014年 | 104篇 |
2013年 | 221篇 |
2012年 | 175篇 |
2011年 | 143篇 |
2010年 | 111篇 |
2009年 | 115篇 |
2008年 | 76篇 |
2007年 | 120篇 |
2006年 | 102篇 |
2005年 | 83篇 |
2004年 | 59篇 |
2003年 | 74篇 |
2002年 | 53篇 |
2001年 | 44篇 |
2000年 | 29篇 |
1999年 | 36篇 |
1998年 | 19篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1990年 | 8篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 11篇 |
1970年 | 4篇 |
排序方式: 共有2625条查询结果,搜索用时 797 毫秒
281.
Incorporating the Effects of Socioeconomic Uncertainty into Priority Setting for Conservation Investment 总被引:1,自引:0,他引:1
MARISSA F. McBRIDE † KERRIE A. WILSON† MICHAEL BODE‡ HUGH P. POSSINGHAM† 《Conservation biology》2007,21(6):1463-1474
Abstract: Uncertainty in the implementation and outcomes of conservation actions that is not accounted for leaves conservation plans vulnerable to potential changes in future conditions. We used a decision-theoretic approach to investigate the effects of two types of investment uncertainty on the optimal allocation of global conservation resources for land acquisition in the Mediterranean Basin. We considered uncertainty about (1) whether investment will continue and (2) whether the acquired biodiversity assets are secure, which we termed transaction uncertainty and performance uncertainty, respectively. We also developed and tested the robustness of different rules of thumb for guiding the allocation of conservation resources when these sources of uncertainty exist. In the presence of uncertainty in future investment ability (transaction uncertainty), the optimal strategy was opportunistic, meaning the investment priority should be to act where uncertainty is highest while investment remains possible. When there was a probability that investments would fail (performance uncertainty), the optimal solution became a complex trade-off between the immediate biodiversity benefits of acting in a region and the perceived longevity of the investment. In general, regions were prioritized for investment when they had the greatest performance certainty, even if an alternative region was highly threatened or had higher biodiversity value. The improved performance of rules of thumb when accounting for uncertainty highlights the importance of explicitly incorporating sources of investment uncertainty and evaluating potential conservation investments in the context of their likely long-term success. 相似文献
282.
Abstract: Urban planners acquire open space to protect natural areas and provide public access to recreation opportunities. Because of limited budgets and dynamic land markets, acquisitions take place sequentially depending on available funds and sites. To address these planning features, we formulated a two-period site selection model with two objectives: maximize the expected number of species represented in protected sites and maximize the expected number of people with access to protected sites. These objectives were both maximized subject to an upper bound on area protected over two periods. The trade-off between species representation and public access was generated by the weighting method of multiobjective programming. Uncertainty was represented with a set of probabilistic scenarios of site availability in a linear-integer formulation. We used data for 27 rare species in 31 candidate sites in western Lake County, near the city of Chicago, to illustrate the model. Each trade-off curve had a concave shape in which species representation dropped at an increasing rate as public accessibility increased, with the trade-off being smaller at higher levels of the area budget. Several sites were included in optimal solutions regardless of objective function weights, and these core sites had high species richness and public access per unit area. The area protected in period one depended on current site availability and on the probabilities of sites being undeveloped and available in the second period. Although the numerical results are specific for our study, the methodology is general and applicable elsewhere. 相似文献
283.
城市污水回用于农业的技术经济分析——以以色列农业灌溉为例 总被引:4,自引:0,他引:4
城市污水回用于农业是污水资源化的有效途径。论述了污水灌溉对农业和环境的影响 ,并以以色列为例对污水回用于农业进行了经济效益分析 ,同时介绍了决定用水组成、回用水质以及农作物的组成等的优化模型 相似文献
284.
285.
286.
针对飞机部件周期控制律电加热防除冰的应用,提出基于机器学习以预测电加热防除冰表面温度的变化趋势.依靠大型结冰风洞及其电加热防除冰控制系统完成防除冰试验,获得有效的试验数据,以通、断电周期为分割单元,将试验数据划分成验证集和训练集.根据电热防除冰过程的换热情况,构建样本的特征参数,利用机器学习的有监督学习方式,选择KNN近邻回归算法和局部线性加权回归算法预测温度变化率,再转换为温度,得到的温度变化与测量数据的线性相关性达到80%以上的高相似度结果,表明使用机器学习可快速预测电热防除冰部件的表面温度变化趋势,且不同的回归算法针对模型不同测温点位置的预测效果存在差异. 相似文献
287.
本文提出了一套适合于我国中小城市大气污染总量控制研究的技术路线和模型。通过环境容量规划和污染综合治理规划的有机结合,从而达到以优化的方式协调经济发展与环境保护的矛盾。对镇江市的应用结果表明,本文提出的技术路线和模型是合理可行的。所给出的总量控制方案既能符合经济发展的需要,又能经济有效地控制并改善区域的大气环境质量。 相似文献
288.
289.
Unkasević M Vukmirović Z Tosić I Lazić L 《Environmental science and pollution research international》2003,10(2):89-97
This study has shown theoretical, observed and experimental evidence of pollutants released, transported and deposited during the Kosovo conflict in 1999 and their effects on precipitation in Serbia. The greatest bombardment of the chemical industry, oil refineries and fuel storage in Serbia which occurred during April, resulted in releases of many hazardous, toxic and cancerogenic substances. The number of April's days with precipitation greater or equal to 0.1 mm in 1999 are compared to those in the period from 1961 to 1990 registered at thirty meteorological stations in Serbia and especially at the Belgrade-Observatory station in the period from 1888 to 1995. The maximums of days with precipitation greater or equal to 0.1 mm were at the wider Belgrade area and at the central and southwestern parts of Serbia during April 1999. This is confirmed by using the Eta trajectory analysis. 相似文献
290.
随着温室效应和全球变暖的加剧,煤燃烧所排出的CO2作为引起温室效应的主要气体而引起人们的密切关注.由于燃煤锅炉所排放的尾气中所含的CO2的体积份额低、排放量大,而且处于微负压状态,因此目前控制和分离吸收CO2的方法,包括各类吸收法、吸附法、膜分离法和O2/CO2燃烧技术等,能够经济可行地适用于电力工业燃煤锅炉尾部烟气中CO2分离的方法非常少.与上述各类方法相比,钙基吸收剂CCRs(calcination/carbonation reactions)法是一种新兴的经济可行的分离燃煤锅炉尾部烟气中CO2的方法.对采用该法时,吸收剂的选择、吸收剂在多次CCRs过程中结构特点的变化、提高吸收剂对CO2的吸收容量以及防止吸收剂反应性的衰减等方面进行了详细的阐述. 相似文献