全文获取类型
收费全文 | 23905篇 |
免费 | 2132篇 |
国内免费 | 7100篇 |
专业分类
安全科学 | 3909篇 |
废物处理 | 436篇 |
环保管理 | 3033篇 |
综合类 | 16092篇 |
基础理论 | 3380篇 |
环境理论 | 13篇 |
污染及防治 | 2119篇 |
评价与监测 | 1208篇 |
社会与环境 | 1737篇 |
灾害及防治 | 1210篇 |
出版年
2024年 | 85篇 |
2023年 | 530篇 |
2022年 | 850篇 |
2021年 | 1022篇 |
2020年 | 991篇 |
2019年 | 953篇 |
2018年 | 800篇 |
2017年 | 886篇 |
2016年 | 1046篇 |
2015年 | 1170篇 |
2014年 | 1131篇 |
2013年 | 1733篇 |
2012年 | 1929篇 |
2011年 | 2139篇 |
2010年 | 1494篇 |
2009年 | 1629篇 |
2008年 | 1323篇 |
2007年 | 1789篇 |
2006年 | 1790篇 |
2005年 | 1403篇 |
2004年 | 1165篇 |
2003年 | 1197篇 |
2002年 | 932篇 |
2001年 | 797篇 |
2000年 | 715篇 |
1999年 | 663篇 |
1998年 | 497篇 |
1997年 | 416篇 |
1996年 | 345篇 |
1995年 | 324篇 |
1994年 | 291篇 |
1993年 | 260篇 |
1992年 | 192篇 |
1991年 | 131篇 |
1990年 | 101篇 |
1989年 | 61篇 |
1988年 | 53篇 |
1987年 | 25篇 |
1986年 | 28篇 |
1985年 | 33篇 |
1984年 | 20篇 |
1983年 | 28篇 |
1982年 | 26篇 |
1981年 | 20篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1977年 | 14篇 |
1973年 | 12篇 |
1972年 | 8篇 |
1971年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
821.
Gregory M. Glenn Artur K. Klamczynski Bor-Sen Chiou Delilah Wood William J. Orts Syed H. Imam 《Journal of Polymers and the Environment》2004,12(3):189-196
Starch aquagel-based lightweight concrete has properties similar to those of other lightweight concrete products. However, starch aquagels are unstable in the strongly alkaline conditions typical of Portland Cement-based concrete and may interfere with the setting process. The effect of alkali treatments on the physical, mechanical, and functional properties of starch aquagels and aquagels from starch/polymer blends was investigated. Starch was blended at 100–115°C in a twin-screw extruder with five different polymers to determine whether the blends improved alkaline resistance. Polymer blends containing 5%, 15%, and 30% of the polymer hydrated and formed aquagels when equilibrated in water for 24 h. However, equilibrium moisture content was lower for the blends compared to the starch control. Aquagels equilibrated in 0.15 N NaOH swelled, lost compressive strength and had greater than 90% moisture. The blend of starch and 30% PVOH absorbed less moisture and was more resistant to alkaline dissolution in 1 N NaOH than the other blends tested making it a more suitable material for aquagel-based concrete. The moisture content of starch-based aquagels and mixing time were critical factors in determining setting times. The size of aquagel blends had a minor effect on density and compressive strength. 相似文献
822.
823.
824.
目前生态影响评价研究中的评价对象、内容和方法缺乏统一的模式,本文以攀枝花高耗能园区的开发为例,尝试建立一套系统的工业园区开发生态影响评价方法,该方法以层次分析法为基础,将生态系统分解为经济发展、社会进步、环境保护、景观生态保护四个目标子系统,并在此基础上细化评价因子,通过专家打分和矩阵运算确定其权重,再根据适当的评价标准,运用指数法得出评价结果。结果表明该工业园区在建成前后,其生态综合指数由0.552提高到0.794.其级别由三级提高到二级,说明该园区生态系统总的状态得到改善,该工业园区项目开发可行。 相似文献
825.
新疆中低产田发展人工草地的初步研究 总被引:3,自引:0,他引:3
从新疆天然草地的利用,农业面临的问题出发,说明在绿洲内发展人工草地的必要性。针对全疆中低产田特点,将其分成7种基本类型。按类型总结出相应适生的饲草种类。通过人工种植这些饲草,达到合理利用改良耕地的目的,进而带动整个农业产业结构的调整,建立起适宜新疆农业发展的草地农业模式。 相似文献
826.
景观生态学在公路建设项目环境影响评价中的应用 总被引:5,自引:0,他引:5
景观生态学中的优势度原理在评价开发建设项目对生态系统完整性及其结构与功能稳定性方面具有很好的适用性,但在线型开发建设项目环境影响评价中很少应用。以公路建设为例,探讨了在线型开发建设项目生态环境影响评价中的应用。 相似文献
827.
828.
胡杨林的衰退原因与林地恢复策略 总被引:8,自引:0,他引:8
胡杨广布于地中海沿岸并呈带状东延至中国和蒙古人民共和国。目前,胡杨林已普遍呈不同程度退化,以塔里木盆地为例,垦伐等人为因素使林地总面积迅速减少。现场观测发现,一些林区缺乏胸径20cm以下的立木,而该地从1972年以来断绝洪水来源,显示洪水对幼苗补给可能存在相关,该地断绝洪水多年后,2002年重新出现洪泛过程,洪水退后出现大量的幼苗生长,从而证实洪水过程是胡杨幼林发生的必要条件。本文就此现象提出恢复部分林地的对策。 相似文献
829.
Exploiting Abstract Possibilities: A Critique of the Concept and Practice of Product Patenting 总被引:2,自引:0,他引:2
Hans Radder 《Journal of Agricultural and Environmental Ethics》2004,17(3):275-291
Developments in biotechnology and genomics have moved the issue of patenting scientific and technological inventions toward the center of interest. In particular, the patentability of genes of plants, animals, or humans and of genetically modified (parts of) living organisms has been discussed, and questioned, from various normative perspectives. This paper aims to contribute to this debate. For this purpose, it first explains a number of relevant aspects of the theory and practice of patenting. The focus is on a special and increasingly significant type of patents, namely product patents. The paper provides three general arguments against the concept and practice of product patenting. The first argument briefly considers the claim that patents are legitimate because they promote socially useful innovation. Against this claim, it is argued that product patents may hamper rather than promote such innovation. The second and main argument concludes that product patents are not adequately based on actual technological inventions, as they should be according to the usual criteria of patentability. The principal moral issue is that product patents tend to reward patentees for inventions they have not really made available. The final argument proposes a method for patenting the heat of the sun. Assuming that granting this patent will be generally considered absurd, the argument exposes a further, fundamental problem of the concept and practice of product patenting. 相似文献
830.
Marie-Claire Cordonier Segger 《Natural resources forum》2004,28(1):61-74
This article develops a practical proposal for progress on sustainable development law. It examines the prospects for an international sustainable development law to provide a framework for more effective, coherent governance. Sustainable development law is briefly defined and an analytical framework is provided. Different degrees of integration between economic, social and environmental law are described. Certain principles of international law related to sustainable development are also highlighted. It is argued that these principles may serve to guide law‐makers and jurists where social, economic and environmental law and policy conflict or overlap. Continuing, underlying questions of sustainable development governance are addressed and its global frameworks analysed. The article also focuses on the 2002 World Summit on Sustainable Development, held in Johannesburg in August‐September 2002, and its specific mandate for the United Nations Commission on Sustainable Development (UNCSD) to take related legal developments into account. The article advances a proposal: that governments, economic, social and environmental intergovernmental organizations and other actors establish a ‘network of inquiry’ with members from relevant groups, including legal and academic organizations, and other expert groups, in order to follow, research, analyse and debate legal developments in a balanced way. 相似文献