收费全文 | 21798篇 |
免费 | 965篇 |
国内免费 | 7575篇 |
安全科学 | 1423篇 |
废物处理 | 1340篇 |
环保管理 | 1731篇 |
综合类 | 11796篇 |
基础理论 | 3693篇 |
环境理论 | 2篇 |
污染及防治 | 7778篇 |
评价与监测 | 851篇 |
社会与环境 | 803篇 |
灾害及防治 | 921篇 |
2024年 | 7篇 |
2023年 | 320篇 |
2022年 | 973篇 |
2021年 | 809篇 |
2020年 | 620篇 |
2019年 | 636篇 |
2018年 | 751篇 |
2017年 | 942篇 |
2016年 | 984篇 |
2015年 | 1165篇 |
2014年 | 1616篇 |
2013年 | 2285篇 |
2012年 | 1807篇 |
2011年 | 1917篇 |
2010年 | 1444篇 |
2009年 | 1361篇 |
2008年 | 1510篇 |
2007年 | 1310篇 |
2006年 | 1225篇 |
2005年 | 890篇 |
2004年 | 642篇 |
2003年 | 815篇 |
2002年 | 741篇 |
2001年 | 601篇 |
2000年 | 663篇 |
1999年 | 723篇 |
1998年 | 616篇 |
1997年 | 549篇 |
1996年 | 495篇 |
1995年 | 424篇 |
1994年 | 330篇 |
1993年 | 293篇 |
1992年 | 248篇 |
1991年 | 160篇 |
1990年 | 102篇 |
1989年 | 82篇 |
1988年 | 70篇 |
1987年 | 43篇 |
1986年 | 37篇 |
1985年 | 23篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
Microplastic pollution is occurring in most ecosystem, yet their presence in high altitude clouds and their influence on cloud formation and climate change are poorly known. Here we analyzed microplastics in cloud water sampled at the summits of Japan mountains at 1300–3776 m altitude by attenuated total reflection imaging and micro-Fourier transform infrared spectroscopy. We observed nine microplastics including polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyamide 6, polycarbonate, ethylene–propylene copolymer or polyethylene–polypropylene alloy, polyurethane, and epoxy resin. Microplastic were fragmented, with mean concentrations ranging from 6.7 to 13.9 pieces per liter, and with Feret diameters ranging from 7.1 to 94.6 μm. Microplastics bearing hydrophilic groups such as carbonyl and/or hydroxyl groups were abundant, suggesting that they might have acted as condensation nuclei of cloud ice and water. Overall, our finding suggest that high-altitude microplastics cloud influence cloud formation and, in turn, might modify the climate.
相似文献Food loss and waste is a major issue affecting food security, environmental pollution, producer profitability, consumer prices, and climate change. About 1.3 billion tons of food products are yearly lost globally, with China producing approximately 20 million tons of soybean dregs annually. Here, we review food and agricultural byproducts with emphasis on the strategies to convert this waste into valuable materials. Byproducts can be used for animal and plant nutrition, biogas production, food, extraction of oils and bioactive substances, and production of vinegar, wine, edible coatings and organic fertilizers. For instance, bioactive compounds represent approximately 8–20% of apple pomace, 5–17% of orange peel, 10–25% of grape seeds, 3–15% of pomegranate peel, and 2–13% of date palm seeds. Similarly, the pharmaceutical industry uses approximately 6.5% of the total output of gelatin derived from fish bones and animal skin. Animals fed with pomegranate peel and olive pomace improved the concentration of deoxyribonucleic acid and protein, the litter size, the milk yield, and nest characteristics. Biogas production amounts to 57.1% using soybean residue, 53.7% using papaya peel, and 49.1% using sugarcane bagasse.
相似文献Plastic pollution is a major environmental issue worldwide, calling for advanced methods to recycle waste plastics in the context of the circular economy. Here we review methods and strategies to convert waste plastics into value-added carbon materials, with focus on sources, properties, pretreatment of waste plastics, and on preparation of carbon materials. Pretreatment techniques include mechanical crushing, plastic stabilization and electrospinning. Carbon materials such as carbon nanotubes, graphene, carbon nanosheets, carbon spheres and porous carbon are prepared by oxygen-limited carbonization, catalytic carbonization, the template-based method, and pressure carbonization. We emphasize the conversion of polyethene terephthalate, polyethylene, polypropylene, polystyrene, halogenated plastics, polyurethane and mixed plastics.
相似文献