全文获取类型
收费全文 | 3943篇 |
免费 | 103篇 |
国内免费 | 1129篇 |
专业分类
安全科学 | 245篇 |
废物处理 | 229篇 |
环保管理 | 412篇 |
综合类 | 1848篇 |
基础理论 | 725篇 |
环境理论 | 3篇 |
污染及防治 | 1293篇 |
评价与监测 | 153篇 |
社会与环境 | 123篇 |
灾害及防治 | 144篇 |
出版年
2024年 | 1篇 |
2023年 | 56篇 |
2022年 | 170篇 |
2021年 | 135篇 |
2020年 | 97篇 |
2019年 | 100篇 |
2018年 | 132篇 |
2017年 | 178篇 |
2016年 | 180篇 |
2015年 | 186篇 |
2014年 | 321篇 |
2013年 | 368篇 |
2012年 | 288篇 |
2011年 | 338篇 |
2010年 | 253篇 |
2009年 | 248篇 |
2008年 | 328篇 |
2007年 | 239篇 |
2006年 | 219篇 |
2005年 | 154篇 |
2004年 | 99篇 |
2003年 | 121篇 |
2002年 | 106篇 |
2001年 | 95篇 |
2000年 | 86篇 |
1999年 | 80篇 |
1998年 | 96篇 |
1997年 | 84篇 |
1996年 | 72篇 |
1995年 | 66篇 |
1994年 | 37篇 |
1993年 | 50篇 |
1992年 | 37篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有5175条查询结果,搜索用时 15 毫秒
531.
Photoreduction characteristics of divalent inorganic mercury(Hg~(2+)) in the presence of specific algae species are still not well known. Laboratory experiments were conducted in the present study to identify the effects of different concentrations of living/dead algae species, including Aphanizomenon flosaquae(AF) and Microcystis aeruginosa(MA), on the photoreduction rate of Hg~(2+)under various light conditions. The experimental results showed that percentage reduction of Hg~(2+)was significantly influenced by radiation wavelengths, and dramatically decreased with the presence of algae. The highest percentage reduction of Hg~(2+)was induced by UV-A, followed by UV-B, visible light and dark for both living and dead AF, and the order was dark UV-A UV-B visible light for both living and dead MA. There were two aspects, i.e., energy and attenuation rate of light radiation and excrementitious generated from algae metabolisms, were involved in the processes of Hg~(2+)photoreduction with the presence of algae under different light conditions. The percentage reduction of Hg~(2+)decreased from 15% to 11% when living and dead AF concentrations increased by 10 times(from 106 to 105 cells/mL), and decreased from 11% to ~ 9% in the case of living and dead MA increased. Algae can adsorb Hg~(2+)and decrease the concentration of free Hg~(2+), thus inhibiting Hg~(2+)photoreduction, especially under the conditions with high concentrations of algae. No significant differences were found in percentage reduction of Hg~(2+)between living and dead treatments of algae species.The results are of great importance for understanding the role of algae in Hg~(2+)photoreduction. 相似文献
532.
孙冰 《安全.健康和环境》2019,19(2):37-43
微通道内流体流动及标量传递信息的获取一直是研究热点之一。基于CFD模拟技术,研究了微通道中气液两相及气液固三相的流动过程。开发了颗粒孔隙尺度网格处理方法,获得了微通道内气液两相流型随气液流速及气相入口尺寸的变化规律,初步分析了催化剂颗粒缝隙气泡的变形、破碎等情况,为微反应器的合理设计提供了指导。 相似文献
533.
In this paper, the dynamic relationship between global surface temperature (global warming) and global carbon dioxide emission (CO2) is modelled and analyzed by causality and spectral analysis in the time domain and frequency domain, respectively. Historical data of global CO2emission and global surface temperature anomalies over 129 years from 1860–1988 are used in this study. The causal relationship between the two phenomena is first examined using the Sim and Granger causality test in the time domain after the data series are filtered by ARIMA models. The Granger causal relationship is further scrutinized and confirmed by cross-spectral and multichannel spectral analysis in the frequency domain. The evidence found from both analyses proves that there is a positive causal relationship between the two variables. The time domain analysis suggests that Granger causality exists between global surface temperature and global CO2emission. Further, CO2emission causes the change in temperature. The conclusions are further confirmed by the frequency domain analysis, which indicates that the increase in CO2emission causes climate warming because a high coherence exists between the two variables. Furthermore, it is proved that climate changes happen after an increase in CO2emission, which confirms that the increase in CO2emission does cause global warming. 相似文献
534.
While analyzing overall planning and coordinated development of urban-rural areas, this paper shows that overall planning for the development of urban-rural areas is a requirement for the best use of productive forces. It means the setting up of a policy mechanism for coordinated growth. Recognizing this, the government should set up a way to lead and manage a unified program to increase service and decrease controlling administration power, while safeguarding and fulfilling the farmers' ownership to the means of production. 相似文献
535.
The U.S. Environmental Protection Agency (EPA) performed a reservoir diagnosis and developed low-cost recommendations to improve drinking water quality for the city of Nizhnii Tagil, Russia. Despite widespread regional pollution, water quality within the drinking water supply source can be summarized as generally good. Sampling and analysis efforts did not reveal appreciable amounts of hazardous chemicals or metals. The major water quality problem stems from an abundance of blue-green algae during the summer months, causing drinking water taste and odor problems and filter clogging at the water treatment plant. City water treatment officials also frequently experience difficulties with maintaining an effective disinfection residual in the distribution system because it spans more than 30 kilometers in length. Regrowth of microorganisms in the distribution system often causes coliform bacteria counts to exceed standards. The implementation of a watershed protection and management program, and the installation of a new disinfection system, to purify drinking water and to reduce bacterial growth in the distribution system should improve drinking water quality for the city residents. 相似文献
536.
Susan E. Riechert 《Behavioral ecology and sociobiology》1993,32(5):343-348
Summary A population of a desert spider species (Agelenopsis aperta) that is located in an unusually favorable thermal and feeding environment (AZ riparian), fails to exhibit territorial, foraging and antipredatory behaviors that are appropriate to its environment. Study of the behavior of this spider species is extended to another population that occupies a similar environment but where there is not potential gene flow from individuals occupying more arid habitats (TX riparian). The two populations are shown to experience similar prey availabilities and predation pressures when compared to a third more arid population (NM desert grassland). Analyses of the relevant behavior patterns demonstrate that the TX riparian population is well-adjusted to the ameliorated conditions. Thus, phylogenetic constraints do not appear to underlie the observed maladaptive behavior of the AZ riparian population and credibility is given to potential gene flow influences. 相似文献
537.
538.
Noninvasive prenatal diagnosis for Duchenne muscular dystrophy based on the direct haplotype phasing
539.
Ä.P. Lino Grima Susan Horton Shashi Kant 《Environment, Development and Sustainability》2003,5(3-4):297-314
Can development occur without running down natural resources in an unsustainable way? The concept of natural capital offers a way for those with divergent views (ecologists and economists for example) to discuss this difficult question. Four aspects are examined in detail. First, the role of institutions in facilitating sustainable development is discussed, with examples from forestry. Then examples from (eco)tourism illustrate the potential – and limits – of applicability of the concept. Measurement issues for natural capital are then considered in detail. Finally, the concept is applied to agricultural strategy in fragile lands, where the tradeoff between the environment and development is likely to be most severe. Some implications for future research and policy are developed. 相似文献
540.