全文获取类型
收费全文 | 786篇 |
免费 | 93篇 |
国内免费 | 210篇 |
专业分类
安全科学 | 226篇 |
废物处理 | 26篇 |
环保管理 | 88篇 |
综合类 | 458篇 |
基础理论 | 84篇 |
污染及防治 | 52篇 |
评价与监测 | 26篇 |
社会与环境 | 24篇 |
灾害及防治 | 105篇 |
出版年
2024年 | 5篇 |
2023年 | 13篇 |
2022年 | 36篇 |
2021年 | 58篇 |
2020年 | 28篇 |
2019年 | 31篇 |
2018年 | 19篇 |
2017年 | 43篇 |
2016年 | 43篇 |
2015年 | 57篇 |
2014年 | 43篇 |
2013年 | 39篇 |
2012年 | 80篇 |
2011年 | 65篇 |
2010年 | 42篇 |
2009年 | 57篇 |
2008年 | 45篇 |
2007年 | 50篇 |
2006年 | 51篇 |
2005年 | 62篇 |
2004年 | 37篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 15篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1089条查询结果,搜索用时 343 毫秒
941.
城市污水处理厂的运行稳定性,直接关系到其运行的成本和对环境的影响。然而,如何判断并改进污水厂的运行稳定性,尚缺乏深入的探讨。通过建立计算机辅助决策支持系统,引入统计学方法,探讨了城市污水处理厂运行稳定性的评估方法。污水处理厂运行稳定性的一个重要表征就是污水厂各工艺单元的各项指标和监测数值处于相对平稳的范围,因此,可以借鉴统计学的原理和方法,构建评估的指标和标准体系,对各常规监测指标长时段的监测数据进行统计分析,寻找时间序列的散布特征,判别工艺单元运行的稳定性,从而评估污水处理厂长期运行状况和趋势,为污水处理厂的管理与维护提供指导意见,改进其运行的稳定性。 相似文献
942.
再生水中阴离子表面活性剂对土壤结构与水流运动的影响 总被引:1,自引:0,他引:1
为揭示再生水回灌农田所引入的阴离子表面活性剂对土壤结构性质与水流运动特征的影响,通过室内灌水入渗试验研究了再生水中阴离子表面活性剂浓度(0、0.001、0.01和0.1倍临界胶束浓度)、灌水频率(1d1次、2d1次、3d1次)、再生水-清水交替灌溉模式(纯再生水灌溉、再生水-清水交替灌溉)条件下受灌土壤容重、非毛管孔隙比、团聚体稳定性、土壤斥水性、地表入渗性能和入渗水流运动非均匀特征的变化规律.结果表明,随着再生水中的阴离子表面活性剂浓度的增大和灌溉频率的增大,受灌土壤容重减小、非毛管孔隙比和土壤团聚体稳定性增大、土壤斥水性增强、地表入渗能力降低、优先流运动非均匀程度增大,从而也增大了农田灌水管理难度;当再生水-清水交替灌溉中的清水淋洗频率增大时,受灌土壤容重增大、非毛管孔隙比和土壤团聚体稳定性降低,但却降低了土壤的斥水性、增大了地表入渗能力并降低了土壤优先流运动的非均匀程度,有利于节省灌水时间、提高灌水效率. 相似文献
943.
纳米生物炭的制备方法比较及其特性研究 总被引:3,自引:0,他引:3
本研究以常见农林废弃物—果木枝条、玉米秸秆和花生秸秆为原料,在350~550℃条件下热解制得五种本体生物炭;采用离心法、球磨法、球磨+离心法3种方法提取纳米生物炭,进而对本体生物炭和纳米生物炭的比表面积、元素含量、矿物组成和表面化学性质等进行比较,以探究物料来源、热解温度和制备方法对纳米生物炭性质及稳定性的影响.与本体生物炭相比,球磨法制得的纳米生物炭比表面积增大1.36~6.94倍,但产物未达到纳米颗粒级别,且在水体中稳定性较弱;球磨+离心法制得的纳米生物炭直径为70.06~103.43nm,在水体中稳定性强;离心法制备的纳米生物炭各项指标均不如其他两种方法.纳米生物炭的产率为2.27%~34.80%,且产率随温度的升高而降低.与本体生物炭相比,纳米生物炭含有更多的羟基等含氧官能团和更少的脂肪碳链.与果木枝条制备的纳米生物炭相比,玉米秸秆和花生秸秆来源的纳米生物炭产率高,但水稳性较差,易发生凝聚.果木枝条来源的纳米生物炭碳酸盐等碱性矿物含量丰富,且由于颗粒表面含氧官能团数量多而zeta电位绝对值高,悬液可以稳定分散.不同方法制备得到的纳米生物炭优缺点各异:球磨法制得的纳米生物炭比表面积更大;球磨+离心法制备的玉米和花生秸秆纳米生物炭的产率更高;低温热解果木炭提取的纳米生物炭水稳性更强. 相似文献
944.
Interactions of the three common atmospheric bases, dimethylamine ((CH3)2NH), methylamine (CH3NH2), ammonia (NH3), all considered to be efficient stabilizers of binary clusters in the Earth's atmosphere, with H2SO4, the key atmospheric precursor, and 14 common atmospheric organic acids (COAs) (formic, acetic, oxalic, malonic, succinic, glutaric acid, adipic, benzoic, phenylacetic, pyruvic, maleic acid, malic, tartaric and pinonic acids) have been studied using the density functional theory (DFT) and composite high-accuracy G3MP2 method. The thermodynamic stability of mixed (COA)(H2SO4), (COA)(B1), (COA)(B2) and (COA)(B3) dimers and (COA)(H2SO4)(B1), (COA)(H2SO4)(B2) and (COA)(H2SO4)(B3) trimers, where B1, B2 and B3 refer to (CH3)2NH, CH3NH2 and NH3, respectively, have been investigated and their impacts on the thermodynamic stability of clusters containing H2SO4 have been studied. Our investigation shows that interactions of H2SO4 with COA, (CH3)2NH, CH3NH2 and NH3 lead to the formation of more stable mixed dimers and trimers than (H2SO4)2 and (H2SO4)2(base), respectively, and emphasize the importance of common organic species for early stages of atmospheric nucleation. We also show that although amines are generally confirmed to be more active than NH3 as stabilizers of binary clusters, in some cases mixed trimers containing NH3 are more stable thermodynamically than those containing CH3NH2. This study indicates an important role of COA, which coexist and interact with that H2SO4 and common atmospheric bases in the Earth atmosphere, in formation of stable pre-nucleation clusters and suggests that the impacts of COA on new particle formation (NPF) should be studied in further details. 相似文献
945.
污泥高维填埋可以解决污泥产量剧增与填埋用地紧张的矛盾,但污泥混合高维填埋的边坡稳定性需进一步考证.本文以抗压强度和抗剪强度均较强的含水率60%左右的干污泥为研究对象,采用GEO-SLOPE软件对污泥高维填埋堆体稳定性进行模拟分析,发现填埋放坡坡度越缓,堆体稳定性越强,所允许的最大填埋高度相应越高,库容增加量越大;填埋高度越高,堆体稳定性越差;以上海老港填埋场为例,填埋单元的最佳放坡坡度为1:3.5,相应的最大允许填埋高度为28m,库容增加量为447.2万m3. 相似文献
946.
947.
It is argued that standard environmental economic and 'ecological economics', have the same fundamentals of valuation in terms of money, based on a demand curve derived from utilitymaximization. But this approach leads to three different measuresof value. An invariant measure of value exists only if the consumer has 'homothetic preferences'. In order to obtain a numerical estimate of value, specific functional forms are necessary, but typically these estimates do not converge. This is due to the fact that the underlying economic model is not structurally stable.According to neoclassical economics, any environmental remediation can be justified only in terms of increases in consumer satisfaction, balancing marginal gains against marginal costs. It is not surprising that the optimal policy obtained fromthis approach suggests only small reductions in greenhouse gases.We show that a unidimensional metric of consumer's utility measured in dollar terms can only trivialize the problem of global climate change. 相似文献
948.
Holling proposed a four-phase conceptual model of ecosystem dynamics that includes exploitation, conservation, and destructive and renewal components to explain the failure of many natural resource management schemes. The model is drawn as a sideways figure-eight i.e. . There are two dimensions in this model, connectivity (abscissa) and the amount of capital stored in the system (ordinate). This conceptual model has been suggested as a guide to thinking about the impact of climate change on biodiversity, but the two dimensions are insufficient and the alignment of the figure-eight model is problematic when compared with actual data. Kay has adjusted the dimensions of the figure-eight model and renamed the abscissa as exergy stored and the ordinate as exergy consumed. We realign the original figure-eight model, labeling the abscissa as carbon stored and the ordinate as nutrients, such that the relative values of both axes are in qualitative agreement with data from four different studies. This new alignment is then shown to fit relatively well with Holling's original labels. This revision of the figure-eight model brings Holling's model into agreement with observations and provides insight into the linkages between biodiversity and climate change. 相似文献
949.
950.