全文获取类型
收费全文 | 1046篇 |
免费 | 56篇 |
国内免费 | 101篇 |
专业分类
安全科学 | 111篇 |
废物处理 | 65篇 |
环保管理 | 106篇 |
综合类 | 327篇 |
基础理论 | 411篇 |
污染及防治 | 100篇 |
评价与监测 | 47篇 |
社会与环境 | 30篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 24篇 |
2016年 | 31篇 |
2015年 | 22篇 |
2014年 | 27篇 |
2013年 | 53篇 |
2012年 | 61篇 |
2011年 | 60篇 |
2010年 | 72篇 |
2009年 | 65篇 |
2008年 | 84篇 |
2007年 | 100篇 |
2006年 | 111篇 |
2005年 | 69篇 |
2004年 | 55篇 |
2003年 | 48篇 |
2002年 | 28篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 41篇 |
1998年 | 22篇 |
1997年 | 26篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有1203条查询结果,搜索用时 312 毫秒
101.
102.
103.
针对污水处理过程中存在的难降解有机物问题,介绍了芬顿的概念和特点,探讨了均相芬顿氧化在原位产生芬顿试剂的机理及应用.目前均相芬顿氧化技术总体可归纳为超声-芬顿氧化技术、微波-芬顿氧化技术、光-芬顿氧化技术、电-芬顿氧化技术.这些技术的应用能促进有机物的降解,提高芬顿技术的处理效率.通过介绍芬顿氧化技术降解废水中污染物的机理,综述了均相芬顿氧化技术在废水处理中的应用,分析了各种方法的适用范围和优缺点. 相似文献
104.
105.
为使开放避难场所符合公众自行避难的实际情况,借鉴Huff模型量化公众选择行为,构建双阶段选址-分配模型,第1阶段确定开放避难场所位置,第2阶段将溢出容量的灾民二次分配到有剩余容量的避难场所,并利用改进粒子群算法进行求解。研究结果表明:双阶段选址-分配模型能够实现同一需求点灾民前往不同避难场所的过程,管理者干预政策能够使服务人数大幅度增加,避免资源浪费、灾民流离失所且二次分配情况主要依赖于第1阶段的结果。研究结果可为管理部门规划应急避难场所提供参考。 相似文献
106.
土地盐渍化作为一种土壤灾害,严重制约着社会经济与农业的发展。对盐碱地进行实时监测,可为盐碱地的评价改良提供科学依据。由于盐碱地的信息复杂、提取精度不高,因此本文以高分六号(GF-6)卫星遥感影像为数据源,采用分形网络演化算法(fractal net evolution approach,FNEA)进行影像对象的多尺度分割,从面向对象的角度减少高分影像分类结果中的椒盐噪声问题,通过计算图像对象的局部方差和变化率来确定适宜的盐碱地分割尺度。利用基于特征选择的相关性算法(correlations-based feature selection,CFS)与Relief F算法分别对由光谱、纹理、形状、遥感指数构成的初始特征空间进行特征优选,精简特征子集,解决特征数量冗余问题,以此来优化随机森林对盐碱地提取精度。结果表明:CFS约简后的特征子集更小,精度更高,说明在盐碱地提取过程中,筛选特征数目能够减小冗余数据对提取精度的影响。CFS优化后的随机森林对盐碱地的提取效果较好,该方法总体分类精度达到83.7%。 相似文献
107.
108.
R. Stoks 《Behavioral ecology and sociobiology》1999,47(1-2):70-75
Animals commonly choose between microhabitats that differ in foraging return and mortality hazard. I studied the influence
of autotomy, the amputation of a body part, on the way larvae of the damselfly Lestes sponsa deal with the trade-off between foraging or seeking cover. Survival of Lestes larvae when confronted with the odonate predator Aeshna cyanea was higher in a complex than in a simple microhabitat, indicating that this more complex microhabitat was safer. Within the
simple microhabitat, larvae without lamellae had a higher risk for mortality by predation than larvae with lamellae, showing
a long-term cost of autotomy. When varying the foraging value (food present or absent) and predation risk (encaged predator
or no predator) in the simple microhabitat, larvae with and without lamellae responded differentially to the imposed trade-off.
All larvae spent more time in the simple microhabitat when food was present than when food was absent. Larvae without lamellae,
however, only sporadically left the safe microhabitat, irrespective of the presence of the predator. In contrast, larvae with
lamellae shifted more frequently towards the risky microhabitat than those without lamellae, and more often in the absence
than in the presence of the predator. These decisions affected the foraging rates of the animals. I show for the first time
that refuge use is higher after autotomy and that this is associated with the cost of reduced foraging success. The different
microhabitat preferences for larvae with and without lamellae are consistent with their different vulnerabilities to predation
and demonstrate the importance of intrinsic factors in establishing trade-offs.
Received: 4 June 1999 / Received in revised form: 18 August 1999/ Accepted: 18 August 1999 相似文献
109.
ANDREW T. KNIGHT RICHARD M. COWLING MARK DIFFORD BRUCE M. CAMPBELL 《Conservation biology》2010,24(5):1348-1358
Abstract Spatial prioritization techniques are applied in conservation‐planning initiatives to allocate conservation resources. Although typically they are based on ecological data (e.g., species, habitats, ecological processes), increasingly they also include nonecological data, mostly on the vulnerability of valued features and economic costs of implementation. Nevertheless, the effectiveness of conservation actions implemented through conservation‐planning initiatives is a function of the human and social dimensions of social‐ecological systems, such as stakeholders’ willingness and capacity to participate. We assessed human and social factors hypothesized to define opportunities for implementing effective conservation action by individual land managers (those responsible for making day‐to‐day decisions on land use) and mapped these to schedule implementation of a private land conservation program. We surveyed 48 land managers who owned 301 land parcels in the Makana Municipality of the Eastern Cape province in South Africa. Psychometric statistical and cluster analyses were applied to the interview data so as to map human and social factors of conservation opportunity across a landscape of regional conservation importance. Four groups of landowners were identified, in rank order, for a phased implementation process. Furthermore, using psychometric statistical techniques, we reduced the number of interview questions from 165 to 45, which is a preliminary step toward developing surrogates for human and social factors that can be developed rapidly and complemented with measures of conservation value, vulnerability, and economic cost to more‐effectively schedule conservation actions. This work provides conservation and land management professionals direction on where and how implementation of local‐scale conservation should be undertaken to ensure it is feasible. 相似文献
110.
Evolutionary psychology has been proposed as an analytic framework for the behavioral effects of landscapes displayed in advertising. In this study, an evolutionary and environmental psychology approach is used to analyze affective reactions to advertising depicting specific natural environments or urban scenes, both prominent ingredients of contemporary advertising imagery. The experimental field study exposed 750 participants at random to one advert of a set of 13 experimental green energy advertisements, each displaying a different biome. Six basic emotional responses (pleasure, arousal, happiness, freedom, safety, and interest) as well as attitude toward the ad and brand attitude were assessed subsequently. Anova and structural equation analysis were used for data analysis. Results of the study confirm the leading opinion on generalized more positive behavioral effects toward visual stimuli representing nature scenes with biospheric contents as opposed to pictures of urban environments or desert settings. In line with earlier empirical research, further findings do not support the hypothesis on an innate preference for savanna landscapes in adults but confirm preferences for images of lush green landscapes with water and familiar biomes. Overall results give significant support to the application of environmental and evolutionary psychology to advertising. 相似文献