全文获取类型
收费全文 | 14821篇 |
免费 | 1214篇 |
国内免费 | 5662篇 |
专业分类
安全科学 | 995篇 |
废物处理 | 1355篇 |
环保管理 | 1956篇 |
综合类 | 11624篇 |
基础理论 | 1383篇 |
环境理论 | 2篇 |
污染及防治 | 3560篇 |
评价与监测 | 459篇 |
社会与环境 | 323篇 |
灾害及防治 | 40篇 |
出版年
2024年 | 20篇 |
2023年 | 116篇 |
2022年 | 277篇 |
2021年 | 392篇 |
2020年 | 413篇 |
2019年 | 398篇 |
2018年 | 401篇 |
2017年 | 429篇 |
2016年 | 583篇 |
2015年 | 755篇 |
2014年 | 1018篇 |
2013年 | 1216篇 |
2012年 | 1452篇 |
2011年 | 1410篇 |
2010年 | 1102篇 |
2009年 | 1193篇 |
2008年 | 934篇 |
2007年 | 1347篇 |
2006年 | 1484篇 |
2005年 | 1057篇 |
2004年 | 846篇 |
2003年 | 887篇 |
2002年 | 709篇 |
2001年 | 590篇 |
2000年 | 531篇 |
1999年 | 469篇 |
1998年 | 352篇 |
1997年 | 286篇 |
1996年 | 235篇 |
1995年 | 191篇 |
1994年 | 169篇 |
1993年 | 146篇 |
1992年 | 99篇 |
1991年 | 59篇 |
1990年 | 32篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A sequencing batch reactor was modeled using multi-layer perceptron and radial basis function artificial neural networks (MLPANN and RBFANN). Then, the effects of influent concentration (IC), filling time (FT), reaction time (RT), aeration intensity (AI), SRT and MLVSS concentration were examined on the effluent concentrations of TSS, TP, COD and NH4+-N. The results showed that the optimal removal efficiencies would be obtained at FT of 1 h, RT of 6 h, aeration intensity of 0.88 m3/min and SRT of 30 days. In addition, COD and TSS removal efficiencies decreased and TP and NH4+-N removal efficiencies did not change significantly with increases of influent concentration. The TSS, TP, COD and NH4+-N removal efficiencies were 86%, 79%, 94% and 93%, respectively. The training procedures of all contaminants were highly collaborated for both RBFANN and MLPANN models. The results of training and testing data sets showed an almost perfect match between the experimental and the simulated effluent of TSS, TP, COD and NH4+-N. The results indicated that with low experimental values of input data to train ANNs the MLPANN models compared to RBFANN models are more precise due to their higher coefficient of determination (R2) and lower root mean squared errors (RMSE) values. 相似文献
2.
面对人口老龄化对经济发展的影响.应以养老和健康保障为先导.逐步加大对社会保障基金的投入.充实基本养老保险和医疗保险基金.建立和完善与生产力发展水平相适应的社会保障制度.继续推进社会保障社会化和产业结构调整的力度.建议政府应大力发展老龄产业。政府必须从实际出发.坚持科学发展观.逐步建立和完善老年社会养老制度和福利制度.根据老年消费市场状况.规范、引导投资.调整、优化产业结构用产业化、市场化、社会化的新运行机制.推进安老、养老产业的发展.根据老年人的不同需求,有计划的发展老龄产业、开发老年用品.增设老年服务项目.满足老年人在物质和文化方面的发展需要.以促使人口老龄化与经济的协调发展。 相似文献
3.
重点开发长江是90年代中国经济重大战略布署。将长江产业带建设成具有强大经济实力的国家一级经济轴线,宜采用分层次推进与中心辐射相结合的发展战略,以浦东开发和三峡建设为契机,加强基础产业,发展新兴产业和第三产业,优化产业结构,以能源和交通建设先行,改善基础设施。同时,要协调产业带建设与浦东开发、三峡工程建设的关系。 相似文献
4.
阐述了开展工业区群环境影响评价的意义,比较了单个工业园区和工业区群环评的异同,以广州番禺区工业区群环评项目为例,简述了该环评的主要内容和特点,并提出了建议。 相似文献
5.
G. D. Kataev 《Russian Journal of Ecology》2005,36(6):421-426
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact. 相似文献
6.
Russian Journal of Ecology - 相似文献
7.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown. 相似文献
8.
Methodological Basis of Ecological Safety Standards for the Technogenic Impact of Mineral Resource Exploitation 总被引:1,自引:0,他引:1
A new methodological approach to the development of biological and technological safety standards for the impact of underground mining on the natural biota is proposed. 相似文献
9.
With China's rapid economic growth, ecological construction and environmental protection become increasingly important. The regenerated resources industry is an effective way to solve problems, such as resources depletion, energy shortage, and pollution, and it also has strategic importance for the construction of a resource-conserving and environment-friendly society. The regenerated resources industry has been established in Miluo for long time, which includes a recycling system, a processing and utilization system, and a refuse decontamination system. An industrial cluster is in its early stage of development. In order to solve current problems, such as short industrial chain, low processing rate, and low added value, the industrial cluster should be dynamically upgraded by means of technology innovation, chain nucleus creation, and chain extension. We think the industrial cluster of regenerated resources will become a local brand for Miluo, from which other regions or cities will gain valuable experiences and inspirations. 相似文献
10.
Xiong Huibing & Sun Nengli . Huazhong Agricultural University Wuhan Hubei China . Shandong Normal University Jinan Shandong China 《中国人口.资源与环境(英文版)》2005,3(1)
1 DEVELOPMENT OF SCIENCE PARKSThe concept of science park originated in the US. Manyterms are used to describe science parks, such as researchpark, technology park, science centre, research centre,innovation centre, and with various combination of these(MacDonald, 1987). The first science park in the worldis Stanford Industrial Park established in 1951. In 1955,only seven companies were located in the park. By 1980there were ninety companies including Hewlett PackardCompany, whic… 相似文献