全文获取类型
收费全文 | 14841篇 |
免费 | 549篇 |
国内免费 | 5805篇 |
专业分类
安全科学 | 923篇 |
废物处理 | 947篇 |
环保管理 | 1174篇 |
综合类 | 8185篇 |
基础理论 | 2620篇 |
环境理论 | 2篇 |
污染及防治 | 5677篇 |
评价与监测 | 549篇 |
社会与环境 | 497篇 |
灾害及防治 | 621篇 |
出版年
2024年 | 4篇 |
2023年 | 230篇 |
2022年 | 690篇 |
2021年 | 556篇 |
2020年 | 420篇 |
2019年 | 436篇 |
2018年 | 537篇 |
2017年 | 667篇 |
2016年 | 815篇 |
2015年 | 1012篇 |
2014年 | 1162篇 |
2013年 | 1622篇 |
2012年 | 1270篇 |
2011年 | 1347篇 |
2010年 | 964篇 |
2009年 | 956篇 |
2008年 | 1016篇 |
2007年 | 924篇 |
2006年 | 826篇 |
2005年 | 603篇 |
2004年 | 420篇 |
2003年 | 549篇 |
2002年 | 483篇 |
2001年 | 410篇 |
2000年 | 432篇 |
1999年 | 473篇 |
1998年 | 422篇 |
1997年 | 352篇 |
1996年 | 333篇 |
1995年 | 285篇 |
1994年 | 235篇 |
1993年 | 188篇 |
1992年 | 152篇 |
1991年 | 89篇 |
1990年 | 70篇 |
1989年 | 54篇 |
1988年 | 47篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
391.
This paper describes the development of a land use model coupling ecosystem processes. For a given land use pattern in a region, a built-in regional ecosystem model (TESim) simulates leaf physiology of plants, carbon and nitrogen dynamics, and hydrological processes including runoff generation and run-on re-absorption, as well as runoff-induced soil erosion and carbon and nitrogen loss from ecosystems. The simulation results for a certain period from 1976 to 1999 were then used to support land use decisions and to assess the impacts of land use changes on environment. In the coupling model, the land use type for a land unit was determined by optimization of a weighted suitability derived from expert knowledge about the ecosystem state and site conditions. The model was applied to the temperate crop-pasture band in northern China (CCPB) to analyze the interactions between land use and major ecosystem processes and functions and to indicate the added value of the feedbacks by comparing simulations with and without the coupling and feedbacks between land use module and ecosystem processes. The results indicated that the current land use in CCPB is neither economical nor ecologically judicious. The scenario with feedbacks increased NPP by 46.78 g C m−2 a−1, or 32.23% of the scenario without feedbacks, also decreased soil erosion by 0.65 kg m−2 a−1, or 23.13%. Without altering the regional land use structure (proportions of each land use type). The system developed in this study potentially benefits both land managers and researchers. 相似文献
392.
Air quality management in China: Issues, challenges, and options 总被引:5,自引:3,他引:5
This article analyzed the control progress and current status of air quality,identified the major air pollution issues and challenges in future,proposed the long-term air pollution control targets,and ... 相似文献
393.
394.
395.
396.
Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Without severe damage to the lumen structures, the kapok fibers were successfully acetylated and the resulting fibers exhibited a better oil sorption capacity than raw fibers for diesel and soybean oil. Compared with high viscosity soybean oil, low viscosity diesel shows a better affinity to the surface of acetylated fibers. Sorption kinetics is fitted well by the pseudo second-order model, and the equilibrium data can be described by the Freundlich isotherm model. The results implied that acetylated kapok fiber can be used as the substitute for non-biodegradable oil sorption materials. 相似文献
397.
Paddy fields in mining areas are usually co-contaminated by a cocktail of mixed toxic heavy metals (e.g., Cd and Pb in Pb/Zn mines). However, previous studies on rice cultivars screened for effective metal exclusion have mostly focused on individual metals, and have been conducted under pot-trial or hydroponic solution conditions. This study identified rice cultivars with both low Cd and Pb accumulation under Cd-and Pb-contaminated field conditions, and the interactions of the toxic elements Cd and Pb with the micronutrient elements Fe, Zn, Mn and Ni were also studied. Among 32 rice cultivars tested, there were significant differences in Cd (0.06-0.59 mg/kg) and Pb (0.25-3.15 mg/kg) levels in their brown rice, and similar results were also found for the micronutrient elements. Significant decreases in concentrations of Fe and Mn were detected with increasing Cd concentrations and a significant elevation in Fe, Mn and Ni with increasing Pb concentrations. A similar result was also shown by Cd and Ni. Three cultivars were identified with a combination of low brown rice Cd and Pb, high micronutrient and grain yield (Wufengyou 2168, Tianyou 196 and Guinongzhan). Present results suggest that it is possible to breed rice cultivars with low mixed toxic element (Cd, Pb) and high micronutrient contents along with high grain yields, thus ensuring food safety and quality. 相似文献
398.
烟台是中国最东部半岛型城市之一,研究应用WRF-CMAQ空气质量模拟系统和排放清单技术,建立以PM2.5质量改善为核心的一次污染物质减排情景和PM2.5浓度下降之间的定量对应关系.分析结果表明,若烟台2020年实现空气质量达标,SO2、NOx、一次PM2.5分别需消减30%、30%和40%以上;一次PM2.5减排控制对PM2.5浓度下降的贡献,是SO2和NOx等常规污染物减排控制效益的8倍左右;如果仅依靠消减SO2和NOx等常规污染物,无法实现PM2.5浓度的大幅度下降. 相似文献
399.
400.
中国页岩气开发过程环境管理现状与对策分析研究 总被引:1,自引:0,他引:1
中国页岩气资源储量丰富,随着页岩气商业勘探开发的不断推进,引发的生态环境问题日益突出.从页岩气开采工艺来看,开发对水、大气、土壤及生态地质环境等都有一定的影响.此外,中国页岩气开发过程中还存在法规标准体系不健全、监管机制缺乏、环境准入机制不明等问题.因此,针对页岩气开发所带来的环境风险,亟需完善法律法规与标准体系、严格监督管理、制定开发环境规划.同时,建设环保示范工程,加大环保科研投入,降低页岩气开发的环境影响,实现页岩气开发的绿色可持续发展. 相似文献