全文获取类型
收费全文 | 24935篇 |
免费 | 2132篇 |
国内免费 | 3905篇 |
专业分类
安全科学 | 3262篇 |
废物处理 | 451篇 |
环保管理 | 4702篇 |
综合类 | 13957篇 |
基础理论 | 2288篇 |
环境理论 | 9篇 |
污染及防治 | 1603篇 |
评价与监测 | 2347篇 |
社会与环境 | 1385篇 |
灾害及防治 | 968篇 |
出版年
2024年 | 52篇 |
2023年 | 400篇 |
2022年 | 650篇 |
2021年 | 851篇 |
2020年 | 900篇 |
2019年 | 710篇 |
2018年 | 624篇 |
2017年 | 855篇 |
2016年 | 1022篇 |
2015年 | 1086篇 |
2014年 | 1210篇 |
2013年 | 1498篇 |
2012年 | 1707篇 |
2011年 | 1873篇 |
2010年 | 1272篇 |
2009年 | 1423篇 |
2008年 | 1086篇 |
2007年 | 1669篇 |
2006年 | 1677篇 |
2005年 | 1411篇 |
2004年 | 1230篇 |
2003年 | 1216篇 |
2002年 | 1062篇 |
2001年 | 886篇 |
2000年 | 818篇 |
1999年 | 725篇 |
1998年 | 500篇 |
1997年 | 437篇 |
1996年 | 340篇 |
1995年 | 297篇 |
1994年 | 260篇 |
1993年 | 211篇 |
1992年 | 151篇 |
1991年 | 121篇 |
1990年 | 78篇 |
1989年 | 55篇 |
1988年 | 68篇 |
1987年 | 57篇 |
1986年 | 37篇 |
1985年 | 36篇 |
1984年 | 44篇 |
1983年 | 38篇 |
1982年 | 42篇 |
1981年 | 39篇 |
1980年 | 46篇 |
1979年 | 42篇 |
1978年 | 21篇 |
1977年 | 20篇 |
1973年 | 26篇 |
1971年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
992.
993.
In Brazil most Construction and Demolition Waste (C&D waste) is not recycled. This situation is expected to change significantly, since new federal regulations oblige municipalities to create and implement sustainable C&D waste management plans which assign an important role to recycling activities. The recycling organizational network and its flows and components are fundamental to C&D waste recycling feasibility. Organizational networks, flows and components involve reverse logistics. The aim of this work is to introduce the concepts of reverse logistics and reverse distribution channel networks and to study the Brazilian C&D waste case. 相似文献
994.
Amit Kapur Hendrik G. van Oss Gregory Keoleian Stephen E. Kesler Alissa Kendall 《Journal of Material Cycles and Waste Management》2009,11(2):155-165
A country-level stock and flow model for cement, an important construction material, was developed based on a material flow
analysis framework. Using this model, the contemporary cement cycle of the United States was constructed by analyzing production,
import, and export data for different stages of the cement cycle. The United States currently supplies approximately 80% of
its cement consumption through domestic production and the rest is imported. The average annual net addition of in-use new
cement stock over the period 2000–2004 was approximately 83 million metric tons and amounts to 2.3 tons per capita of concrete.
Nonfuel carbon dioxide emissions (42 million metric tons per year) from the calcination phase of cement manufacture account
for 62% of the total 68 million tons per year of cement production residues. The end-of-life cement discards are estimated
to be 33 million metric tons per year, of which between 30% and 80% is recycled. A significant portion of the infrastructure
in the United States is reaching the end of its useful life and will need to be replaced or rehabilitated; this could require
far more cement than might be expected from economic forecasts of demand for cement. 相似文献
995.
水质模型参数的确定是构建水质模型的基础。相对于传统优化方法,现代优化算法的优势日趋明显。本文在基于现代优化算法的水质模型参数确定研究背景下,介绍了具有代表性的遗传算法和模拟退火算法,并对该两种算法的应用现状进行综述,旨在推进该领域的进一步探索。 相似文献
996.
综述了2009年我国机动车污染防治行业的发展环境及市场特点、主要(骨干)企业发展情况,分析了2009年行业发展中存在的主要问题,提出了解决对策和建议,并对行业的发展进行了展望。 相似文献
997.
This work provides an exploratory analysis on the relative importance of various factors controlling the fate and transport of volatile organic contaminants (in this case, TCE) from a DNAPL source zone located below the water table and into the indoor air. The analysis is conducted using the multi-phase compositional model CompFlow Bio, with the base scenario problem geometry reminiscent of a field experiment conducted by Rivett [Rivett, M.O., (1995), Soil–gas signatures from volatile chlorinated solvents: Borden field experiments. Groundwater, 33(1), 84–98.] at the Borden aquifer where groundwater was observed to transport a contaminant plume a substantial distance without vertical mass transport of the contaminant across the capillary fringe and into the vadose zone. Results for the base scenario model indicate that the structure of the permeability field was largely responsible for deflecting the groundwater plume upward towards the capillary fringe, permitting aqueous phase diffusion to transport the TCE into the vadose zone. Alternative permeability realizations, generated as part of a Monte Carlo simulation process, at times deflected the groundwater plume downwards causing the extended thickness of the saturated zone to insulate the vadose zone from exposure to the TCE by upward diffusive transport. Comparison of attenuation coefficients calculated using the CompFlow Bio and Johnson and Ettinger [Johnson, P.C. and Ettinger, R.A., (1991), Heuristic model for predicting the intrusion rate of contaminant vapors into buildings. Environmental Science and Technology, 25, 1445–1452.] heuristic model exhibited fortuitous agreement for the base scenario problem geometry, with this agreement diverging for the alternative permeability realizations as well as when parameters such as the foundation slab fracture aperture, the indoor air pressure drop, the capillary fringe thickness, and the infiltration rate were varied over typical ranges. 相似文献
998.
999.
为了解2种新分离微藻的净化和资源化潜力,研究比较了其生长、氮磷去除和营养特性。结果表明,栅藻和月牙藻的最大生物量(干重)分别为0.78g/L和0.53g/L;最大生物量(干重)增长速率分别为0.05g/(L·d)和0.03g/(L·d)。培养至第23天,栅藻和月牙藻对TN的去除率分别为85.1%和72.5%;对TP的去除率为82.6%和79.7%,但栅藻较月牙藻更易释放较多的No2--N进入藻液。稳定期时,栅藻、月牙藻的粗蛋白质含量和粗蛋白产量(干重)分别为31.8%、19.2%和0.24g/L、0.09g/L;粗脂含量和粗脂产量(干重)分别为7.81%、9.26%和0.06g/L、0.05g/L。综上,与月牙藻相比,栅藻具有明显的生长、氮磷去除和营养优势,在进行水产养殖废水的净化和资源化利用上可作为优选藻种。 相似文献
1000.
Zsuzsanna Horváth Árpád Ambrus László Mészáros Simone Braun 《Journal of environmental science and health. Part. B》2013,48(8):615-625
The characteristic features of distribution of pesticide residues in crop units and single sample increments were studied based on more than 19,000 residue concentrations measured in root vegetables, leafy vegetables, small-, medium- and large-size fruits representing 20 different crops and 46 pesticides. Log-normal, gamma and Weibull distributions were found to provide the best fit for the relative frequency distributions of individual residue data sets. The overall best fit was provided by lognormal distribution. The relative standard deviation of residues (CV) in various crops ranged from 15–170%. The 100–120 residue values being in one data set was too small to identify potential effects of various factors such as the chemical and physical properties of pesticides and the nature of crops. Therefore, the average of CV values, obtained from individual data sets, were calculated and considered to be the best estimate for the likely variability of unit crop residues for treated field (CV = 0.8) and market samples (CV = 1.1), respectively. The larger variation of residues in market samples was attributed to the potential mixing of lots and varying proportion of non-detects. The expectable average variability of residues in composited samples can be calculated from the typical values taking into account the sample size. 相似文献