全文获取类型
收费全文 | 10151篇 |
免费 | 1311篇 |
国内免费 | 5527篇 |
专业分类
安全科学 | 1980篇 |
废物处理 | 288篇 |
环保管理 | 1018篇 |
综合类 | 9104篇 |
基础理论 | 2016篇 |
环境理论 | 4篇 |
污染及防治 | 1402篇 |
评价与监测 | 481篇 |
社会与环境 | 392篇 |
灾害及防治 | 304篇 |
出版年
2024年 | 55篇 |
2023年 | 432篇 |
2022年 | 597篇 |
2021年 | 670篇 |
2020年 | 672篇 |
2019年 | 672篇 |
2018年 | 542篇 |
2017年 | 510篇 |
2016年 | 590篇 |
2015年 | 682篇 |
2014年 | 581篇 |
2013年 | 1048篇 |
2012年 | 1057篇 |
2011年 | 1130篇 |
2010年 | 770篇 |
2009年 | 907篇 |
2008年 | 735篇 |
2007年 | 878篇 |
2006年 | 857篇 |
2005年 | 623篇 |
2004年 | 525篇 |
2003年 | 436篇 |
2002年 | 324篇 |
2001年 | 277篇 |
2000年 | 250篇 |
1999年 | 203篇 |
1998年 | 148篇 |
1997年 | 144篇 |
1996年 | 112篇 |
1995年 | 122篇 |
1994年 | 84篇 |
1993年 | 74篇 |
1992年 | 51篇 |
1991年 | 23篇 |
1990年 | 27篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 5篇 |
1986年 | 13篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
301.
302.
从区域可持续发展的角度出发,提出了区域资源环境经济(REE)系统的概念,初步对区域REE系统的研究对象、系统结构进行了探讨,建立了区域REE系统可持续运行的评价指标体系,并通过实例研究论证了它对区域可持续发展的基础性和指导作用,以及评价指标体系的可用性. 相似文献
303.
304.
Nugraha E. Suyatma Alain Copinet Lan Tighzert Veronique Coma 《Journal of Polymers and the Environment》2004,12(1):1-6
Biodegradable film blends of chitosan with poly(lactic acid) (PLA) were prepared by solution mixing and film casting. The main goal of these blends is to improve the water vapor barrier of chitosan by blending it with a hydrophobic biodegradable polymer from renewable resources. Mechanical properties of obtained films were assessed by tensile test. Thermal properties, water barrier properties, and water sensitivity were studied by differential scanning calorimeter analysis, water vapor permeability measurements, and surface-angle contact tests, respectively. The incorporation of PLA to chitosan improved the water barrier properties and decreased the water sensitivity of chitosan film. However, the tensile strength and elastic modulus of chitosan decreased with the addition of PLA. Mechanical and thermal properties revealed that chitosan and PLA blends are incompatible, consistent with the results of Fourier transform infrared (FTIR) analysis that showed the absence of specific interaction between chitosan and PLA. 相似文献
305.
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
306.
307.
308.
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
309.
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
310.
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