收费全文 | 33902篇 |
免费 | 327篇 |
国内免费 | 397篇 |
安全科学 | 977篇 |
废物处理 | 1404篇 |
环保管理 | 4613篇 |
综合类 | 5995篇 |
基础理论 | 8455篇 |
环境理论 | 15篇 |
污染及防治 | 8885篇 |
评价与监测 | 2257篇 |
社会与环境 | 1823篇 |
灾害及防治 | 202篇 |
2022年 | 294篇 |
2021年 | 301篇 |
2020年 | 193篇 |
2019年 | 263篇 |
2018年 | 487篇 |
2017年 | 488篇 |
2016年 | 766篇 |
2015年 | 550篇 |
2014年 | 822篇 |
2013年 | 2778篇 |
2012年 | 1043篇 |
2011年 | 1381篇 |
2010年 | 1151篇 |
2009年 | 1222篇 |
2008年 | 1389篇 |
2007年 | 1509篇 |
2006年 | 1333篇 |
2005年 | 1058篇 |
2004年 | 1079篇 |
2003年 | 1108篇 |
2002年 | 1006篇 |
2001年 | 1322篇 |
2000年 | 915篇 |
1999年 | 610篇 |
1998年 | 434篇 |
1997年 | 416篇 |
1996年 | 473篇 |
1995年 | 457篇 |
1994年 | 449篇 |
1993年 | 406篇 |
1992年 | 426篇 |
1991年 | 387篇 |
1990年 | 408篇 |
1989年 | 384篇 |
1988年 | 348篇 |
1987年 | 308篇 |
1986年 | 277篇 |
1985年 | 306篇 |
1984年 | 317篇 |
1983年 | 316篇 |
1982年 | 357篇 |
1981年 | 301篇 |
1980年 | 267篇 |
1979年 | 287篇 |
1978年 | 248篇 |
1977年 | 221篇 |
1976年 | 221篇 |
1975年 | 193篇 |
1974年 | 218篇 |
1973年 | 192篇 |
The automobile exhausts are one of the major sources of particulate matter in urban areas and these particles are known to influence the atmospheric chemistry in a variety of ways. Because of this, the oxidation of dissolved sulfur dioxide by oxygen was studied in aqueous suspensions of particulates, obtained by scraping the particles deposited inside a diesel truck exhaust pipe (DEP). A variation in pH showed the rate to increase with increase in pH from 5.22 to about ~6.3 and to decrease thereafter becoming very slow at pH?=?8.2. In acetate-buffered medium, the reaction rate was higher than the rate in unbuffered medium at the same pH. Further, the rate was found to be higher in suspension than in the leachate under otherwise identical conditions. And, the reaction rate in the blank reaction was the slowest. This appears to be due to catalysis by leached metal ions in leachate and due to catalysis by leached metal ions and particulate surface both in suspensions. The kinetics of dissolved SO2 oxidation in acetate-buffered medium as well as in unbuffered medium at pH?=?5.22 were defined by rate law: k obs ?=?k 0?+?k cat [DEP], where k obs and k 0 are observed rate constants in the presence and the absence of DEP and k cat is the rate constant for DEP-catalyzed pathway. At pH?=?8.2, the reaction rate was strongly inhibited by DEP in buffered and unbuffered media. Results suggest that the DEP would have an inhibiting effect in those areas where rainwater pH is 7 or more. These results at high pH are of particular significance to the Indian subcontinent, because of high rainwater pH. Conversely, it indicates the DEP to retard the oxidation of dissolved SO2 and control rainwater acidification.
相似文献The land disposal of waste and wastewater is a major source of N2O emission. This is due to the presence of high concentrations of nitrogen (N) and carbon in the waste. Abattoir wastewater contains 186 mg/L of N and 30.4 mg/L of P. The equivalent of 3 kg of abattoir wastewater-irrigated soil was sieved and taken in a 4-L plastic container. Abattoir wastewater was used for irrigating the plants at the rates of 50 and 100 % field capacity (FC). Four crop species were used with no crop serving as a control. Nitrous oxide emission was monitored using a closed chamber technique. The chamber was placed inside the plastic container, and N2O emission was measured for 7 days after the planting. A syringe and pre-evacuated vial were used for collecting the gas samples; a fresh and clean syringe was used each time to avoid cross-contamination. The collected gas samples were injected into a gas chromatography device immediately after each sampling to analyse the concentration of N2O from different treatments. The overall N2O emission was compared for all the crops under two different abattoir wastewater treatment rates (50 and 100 % FC). Under 100 % FC (wastewater irrigation), among the four species grown in the abattoir wastewater-irrigated soil, Medicago sativa (23 mg/pot), Sinapis alba (21 mg/pot), Zea mays (20 mg/pot) and Helianthus annuus (20 mg/pot) showed higher N2O emission compared to the 50 % treatments—M. sativa (17 mg/pot), S. alba (17 mg/pot), Z. mays (18 mg/pot) and H. annuus (18 mg/pot). Similarly, pots with plants have shown 15 % less emission than the pots without plants. Similar trends of N2O emission flux were observed between the irrigation period (4-week period) for 50 % FC and 100 % FC. Under the 100 % FC loading rate treatments, the highest N2O emission was in the following order: week 1 > week 4 > week 3 > week 2. On the other hand, under the 50 % FC loading rate treatments, the highest N2O emission was recorded in the first few weeks and in the following order: week 1 > week 2 > week 3 > week > 4. Since N2O is a greenhouse gas with high global warming potential, its emission from wastewater irrigation is likely to impact global climate change. Therefore, it is important to examine the effects of abattoir wastewater irrigation on soil for N2O emission potential.
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