全文获取类型
收费全文 | 4716篇 |
免费 | 187篇 |
国内免费 | 1745篇 |
专业分类
安全科学 | 312篇 |
废物处理 | 288篇 |
环保管理 | 351篇 |
综合类 | 2424篇 |
基础理论 | 778篇 |
污染及防治 | 1931篇 |
评价与监测 | 173篇 |
社会与环境 | 186篇 |
灾害及防治 | 205篇 |
出版年
2024年 | 3篇 |
2023年 | 80篇 |
2022年 | 234篇 |
2021年 | 174篇 |
2020年 | 122篇 |
2019年 | 121篇 |
2018年 | 189篇 |
2017年 | 215篇 |
2016年 | 268篇 |
2015年 | 304篇 |
2014年 | 374篇 |
2013年 | 496篇 |
2012年 | 376篇 |
2011年 | 434篇 |
2010年 | 312篇 |
2009年 | 288篇 |
2008年 | 303篇 |
2007年 | 249篇 |
2006年 | 262篇 |
2005年 | 188篇 |
2004年 | 148篇 |
2003年 | 155篇 |
2002年 | 159篇 |
2001年 | 147篇 |
2000年 | 155篇 |
1999年 | 141篇 |
1998年 | 152篇 |
1997年 | 114篇 |
1996年 | 106篇 |
1995年 | 81篇 |
1994年 | 65篇 |
1993年 | 58篇 |
1992年 | 53篇 |
1991年 | 26篇 |
1990年 | 35篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有6648条查询结果,搜索用时 15 毫秒
661.
Wu Peilin & Lu Qi . Shandong University of Technology Zibo Shandong China . Institute of Geographical Sciences Natural Resources Research Chinese Academy of Sciences Beijing China 《中国人口.资源与环境(英文版)》2005,3(1)
1 BACKGROUND OF FLOATING POPULATIONIN CHINAChina's urbanization process was influenced mainly bythe government interventions before the adoption of thesocial and economic reform started in 1978. Since thefoundation of the People's Republic of China, thegovernment had strictly controlled the internal migration,especially from rural to urban areas. The ability of thegovernment to make a strong impact on the migrationand urbanization was realized by the household registrationsyste… 相似文献
662.
吴桂生 《湖南环境生物职业技术学院学报》2002,8(3):224-225
在高职院校如何提高学生的学习兴趣和激发学生的求知欲,是一个在理论上和实践中都值得探讨的问题.本文就怎样培养学生的学习兴趣的途径、方法进行了探讨,并提出了可行的解决办法. 相似文献
663.
基于12个微量元素、10个稀土元素和24个同位素分析结果,作者认为本区钾质火山岩系中超基性岩和极大多数基性岩有接近原生岩浆的成分,岩浆都是地幔岩石低程度部分熔融形成的,其源岩成分为受流体交代的金云母石榴石二辉橄榄岩。综地球化学、地球物理及地质三方面资料分析,论证本区火山活动的构造背景是大陆裂谷。 相似文献
664.
665.
近些年来一些方面进展使得有可能对微量元素在癌变过程中的作用提出新认识,这些新认识可以归纳如下: 1.微量元素具有直接致癌作用。 2.擞量元素具有促癌作用。即: (1)可能促进或加强化学致癌物在体内的活化过程; (2)可能活化肿瘤病病毒; (3)一般认为造成内分沁失调而加速癌变过程; 3.微量元素具抑癌作用。 相似文献
666.
Tsai MY Chen KS Wu CH 《Journal of the Air & Waste Management Association (1995)》2005,55(8):1178-1189
Effects of excess ground and building temperatures on airflow and dispersion of pollutants in an urban street canyon with an aspect ratio of 0.8 and a length-to-width ratio of 3 were investigated numerically. Three-dimensional governing equations of mass, momentum, energy, and species were modeled using the RNG k-epsilon turbulence model and Boussinesq approximation, which were solved using the finite volume method. Vehicle emissions were estimated from the measured traffic flow rates and modeled as banded line sources, with a street length and bandwidths equal to typical vehicle widths. Both measurements and simulations reveal that pollutant concentrations typically follow the traffic flow rate; they decline as the height increases and are higher on the leeward side than on the windward side. Three-dimensional simulations reveal that the vortex line, joining the centers of cross-sectional vortexes of the street canyon, meanders between street buildings and shifts toward the windward side when heating strength is increased. Thermal boundary layers are very thin. Entrainment of outside air increases, and pollutant concentration decreases with increasing heating condition. Also, traffic-produced turbulence enhances the turbulent kinetic energy and the mixing of temperature and admixtures in the canyon. Factors affecting the inaccuracy of the simulations are addressed. 相似文献
667.
The impacts of the aeration and the agitation on the composting process of synthetic food wastes made of dog food were studied in a laboratory-scale reactor. Two major peaks of CO(2) evolution rate were observed. Each peak represented an independent stage of composting associated with the activities of thermophilic bacteria. CO(2) evolutions known to correlate well with microbial activities and reactor temperatures were fitted successfully to a modified Gompertz equation, which incorporated three biokinetic parameters, namely, CO(2) evolution potential, specific CO(2) evolution rate, and lag phase time. No parameters that describe the impact of operating variables are involved. The model is only valid for the specified experimental conditions and may look different with others. The effects of operating parameters such as aeration and agitation were studied statistically with multivariate regression technique. Contour plots were constructed using regression equations for the examination of the dependence of CO(2) evolution potentials on aeration and agitation. In the first stage, a maximum CO(2) evolution potential was found when the aeration rate and the agitation parameter were set at 1.75 l/kg solids-min and 0.35, respectively. In the second stage, a maximum existed when the aeration rate and the agitation parameter were set at 1.8 l/kg solids-min and 0.5, respectively. The methods presented here can also be applied for the optimization of large-scale composting facilities that are operated differently and take longer time. 相似文献
668.
我国小康生活水平的测量尺度与标准 总被引:22,自引:0,他引:22
吴寒光 《中国人口.资源与环境》1995,(2)
本文在分析我国经济、社会发展规划、目标和现代化进程的基础上,借鉴国际上的通用标准,并结合我国国情,提出了我国小康生活水平的测量标准,建立了由20个指标构成的小康生活水平指标体系。 相似文献
669.
PRED问题与地理工程 总被引:1,自引:0,他引:1
本文首先定义了由人口、资源、环境和发展构成的PRED问题的思路,讨论了它的性质;然后提出用地理工程解决PRED问题,并构建了地理工程的理论框架。 相似文献
670.
第四类芳香烃 活性特点: 芳香烃化合物的分子里至少含有6个碳原子,并且含氢的比例较脂肪类化合物少得多,为共轭环状结构,非常稳定. 相似文献