收费全文 | 33652篇 |
免费 | 359篇 |
国内免费 | 506篇 |
安全科学 | 1027篇 |
废物处理 | 1587篇 |
环保管理 | 4121篇 |
综合类 | 5504篇 |
基础理论 | 9027篇 |
环境理论 | 20篇 |
污染及防治 | 8787篇 |
评价与监测 | 2296篇 |
社会与环境 | 1966篇 |
灾害及防治 | 182篇 |
2023年 | 142篇 |
2022年 | 334篇 |
2021年 | 336篇 |
2020年 | 246篇 |
2019年 | 297篇 |
2018年 | 592篇 |
2017年 | 607篇 |
2016年 | 927篇 |
2015年 | 628篇 |
2014年 | 918篇 |
2013年 | 2583篇 |
2012年 | 1444篇 |
2011年 | 1651篇 |
2010年 | 1224篇 |
2009年 | 1268篇 |
2008年 | 1505篇 |
2007年 | 1588篇 |
2006年 | 1368篇 |
2005年 | 1475篇 |
2004年 | 1457篇 |
2003年 | 1448篇 |
2002年 | 1010篇 |
2001年 | 1274篇 |
2000年 | 889篇 |
1999年 | 546篇 |
1998年 | 354篇 |
1997年 | 379篇 |
1996年 | 363篇 |
1995年 | 441篇 |
1994年 | 462篇 |
1993年 | 365篇 |
1992年 | 385篇 |
1991年 | 363篇 |
1990年 | 395篇 |
1989年 | 350篇 |
1988年 | 299篇 |
1987年 | 284篇 |
1986年 | 229篇 |
1985年 | 252篇 |
1984年 | 270篇 |
1983年 | 262篇 |
1982年 | 247篇 |
1981年 | 235篇 |
1980年 | 179篇 |
1979年 | 198篇 |
1978年 | 181篇 |
1975年 | 144篇 |
1974年 | 121篇 |
1972年 | 138篇 |
1971年 | 134篇 |
In tropical areas, pioneer occupation fronts steer the rapid expansion of deforestation, contributing to carbon emissions. Up-to-date carbon emission estimates covering the long-term development of such frontiers depend on the availability of high spatial–temporal resolution data. In this paper, we provide a detailed assessment of carbon losses from deforestation and potential forest degradation from fragmentation for one expanding frontier in the Brazilian Amazon. We focused on one of the Amazonia’s hot-spots of forest loss, the BR-163 highway that connects the high productivity agricultural landscapes in Mato Grosso with the exporting harbors of the Amazon. We used multi-decadal (1984–2012) Landsat-based time series on forested and non-forested area in combination with a carbon book-keeping model. We show a 36% reduction in 1984s biomass carbon stocks, which led to the emission of 611.5 TgCO2 between 1985 and 1998 (43.6 TgCO2 year−1) and 959.8 TgCO2 over 1999–2012 (68.5 TgCO2 year−1). Overall, fragmentation-related carbon losses represented 1.88% of total emissions by 2012, with an increasing relevance since 2004. We compared the Brazilian Space Agency deforestation assessment (PRODES) with our data and found that small deforestation polygons not captured by PRODES had increasing importance on estimated deforestation carbon losses since 2000. The comparative analysis improved the understanding of data-source-related uncertainties on carbon estimates and indicated disagreement areas between datasets that could be subject of future research. Furthermore, spatially explicit, annual deforestation and emission estimates like the ones derived from this study are important for setting regional baselines for REDD+ or similar payment for ecosystem services frameworks.
相似文献The consensus in the literature holds that female-headed households (FHHs) are more vulnerable to social and economic exclusion than male-headed households (MHHs). This paper investigates the socioeconomic determinants of household cooking fuel choices across MHHs and FHHs, using the rich Nigerian Demographic Health Survey data. Using the exogenous switching treatment effect regression (ESTER) technique, the study is able to unravel differences in socioeconomic effects of gender inequality on cooking fuel choices in Nigeria. The results validate the energy ladder hypothesis in the Nigerian case and show that the choices of dirty fuel (biomass) is more prevalent among the de-jure FHH when compared with the de-facto FHH and MHHs. Also, the probability of biomass-use among MHHs would have fallen by 1.3% if MHHs had similar socioeconomic attributes as the FHHs. In the same vain for FHHs, the probability of kerosene-use would have increased by 2%. The study observed no gender gap in kerosene-use. Thus, the established gender gap in biomass- and kerosene-use would have reduced to 6.7% and 2.8%, respectively, if the de-facto FHHs had same socioeconomic attributes as the de-jures. Considering the traditional gendered household division of labor within the households, de-jure FHHs’ energy choices may be due to limited economic opportunities that guarantees cleaner energy options.
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