全文获取类型
收费全文 | 52018篇 |
免费 | 551篇 |
国内免费 | 627篇 |
专业分类
安全科学 | 1586篇 |
废物处理 | 2122篇 |
环保管理 | 6888篇 |
综合类 | 8489篇 |
基础理论 | 14537篇 |
环境理论 | 38篇 |
污染及防治 | 13278篇 |
评价与监测 | 3292篇 |
社会与环境 | 2620篇 |
灾害及防治 | 346篇 |
出版年
2022年 | 445篇 |
2021年 | 442篇 |
2020年 | 351篇 |
2019年 | 440篇 |
2018年 | 785篇 |
2017年 | 766篇 |
2016年 | 1171篇 |
2015年 | 909篇 |
2014年 | 1313篇 |
2013年 | 3995篇 |
2012年 | 1698篇 |
2011年 | 2303篇 |
2010年 | 1847篇 |
2009年 | 1891篇 |
2008年 | 2263篇 |
2007年 | 2353篇 |
2006年 | 2062篇 |
2005年 | 1907篇 |
2004年 | 1913篇 |
2003年 | 1885篇 |
2002年 | 1583篇 |
2001年 | 2042篇 |
2000年 | 1424篇 |
1999年 | 891篇 |
1998年 | 667篇 |
1997年 | 676篇 |
1996年 | 682篇 |
1995年 | 758篇 |
1994年 | 755篇 |
1993年 | 640篇 |
1992年 | 661篇 |
1991年 | 618篇 |
1990年 | 656篇 |
1989年 | 642篇 |
1988年 | 561篇 |
1987年 | 499篇 |
1986年 | 426篇 |
1985年 | 485篇 |
1984年 | 483篇 |
1983年 | 499篇 |
1982年 | 485篇 |
1981年 | 453篇 |
1980年 | 367篇 |
1979年 | 408篇 |
1978年 | 361篇 |
1977年 | 280篇 |
1976年 | 285篇 |
1975年 | 292篇 |
1974年 | 259篇 |
1972年 | 289篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
11.
12.
Understanding implications of consumer behavior for wildlife farming and sustainable wildlife trade 下载免费PDF全文
A. Nuno J. M. Blumenthal T. J. Austin J. Bothwell G. Ebanks‐Petrie B. J. Godley A. C. Broderick 《Conservation biology》2018,32(2):390-400
Unsustainable wildlife trade affects biodiversity and the livelihoods of communities dependent upon those resources. Wildlife farming has been proposed to promote sustainable trade, but characterizing markets and understanding consumer behavior remain neglected but essential steps in the design and evaluation of such operations. We used sea turtle trade in the Cayman Islands, where turtles have been farm raised for human consumption for almost 50 years, as a case study to explore consumer preferences toward wild‐sourced (illegal) and farmed (legal) products and potential conservation implications. Combining methods innovatively (including indirect questioning and choice experiments), we conducted a nationwide trade assessment through in‐person interviews from September to December 2014. Households were randomly selected using disproportionate stratified sampling, and responses were weighted based on district population size. We approached 597 individuals, of which 37 (6.2%) refused to participate. Although 30% of households had consumed turtle in the previous 12 months, the purchase and consumption of wild products was rare (e.g., 64–742 resident households consumed wild turtle meat [i.e., 0.3–3.5% of households] but represented a large threat to wild turtles in the area due to their reduced populations). Differences among groups of consumers were marked, as identified through choice experiments, and price and source of product played important roles in their decisions. Despite the long‐term practice of farming turtles, 13.5% of consumers showed a strong preference for wild products, which demonstrates the limitations of wildlife farming as a single tool for sustainable wildlife trade. By using a combination of indirect questioning, choice experiments, and sales data to investigate demand for wildlife products, we obtained insights about consumer behavior that can be used to develop conservation‐demand‐focused initiatives. Lack of data from long‐term social–ecological assessments hinders the evaluation of and learning from wildlife farming. This information is key to understanding under which conditions different interventions (e.g., bans, wildlife farming, social marketing) are likely to succeed. 相似文献
13.
Fishing‐gear restrictions and biomass gains for coral reef fishes in marine protected areas 下载免费PDF全文
Stuart J. Campbell Graham J. Edgar Rick D. Stuart‐Smith German Soler Amanda E. Bates 《Conservation biology》2018,32(2):401-410
Considerable empirical evidence supports recovery of reef fish populations with fishery closures. In countries where full exclusion of people from fishing may be perceived as inequitable, fishing‐gear restrictions on nonselective and destructive gears may offer socially relevant management alternatives to build recovery of fish biomass. Even so, few researchers have statistically compared the responses of tropical reef fisheries to alternative management strategies. We tested for the effects of fishery closures and fishing gear restrictions on tropical reef fish biomass at the community and family level. We conducted 1,396 underwater surveys at 617 unique sites across a spatial hierarchy within 22 global marine ecoregions that represented 5 realms. We compared total biomass across local fish assemblages and among 20 families of reef fishes inside marine protected areas (MPAs) with different fishing restrictions: no‐take, hook‐and‐line fishing only, several fishing gears allowed, and sites open to all fishing gears. We included a further category representing remote sites, where fishing pressure is low. As expected, full fishery closures, (i.e., no‐take zones) most benefited community‐ and family‐level fish biomass in comparison with restrictions on fishing gears and openly fished sites. Although biomass responses to fishery closures were highly variable across families, some fishery targets (e.g., Carcharhinidae and Lutjanidae) responded positively to multiple restrictions on fishing gears (i.e., where gears other than hook and line were not permitted). Remoteness also positively affected the response of community‐level fish biomass and many fish families. Our findings provide strong support for the role of fishing restrictions in building recovery of fish biomass and indicate important interactions among fishing‐gear types that affect biomass of a diverse set of reef fish families. 相似文献
14.
M. Kansanga P. Andersen D. Kpienbaareh S. Mason-Renton K. Atuoye Y. Sano 《国际发展与全球生态学杂志》2019,26(1):11-24
Following the renewed effort at achieving a new green revolution for Africa, emphasis has been placed on modernizing smallholder agriculture through the deployment of improved inputs especially mechanized technologies. In Ghana, the government has in the last decade emphasized the provision of subsidized mechanized ploughing services to farmers alongside a rapidly growing private sector tractor service market. While mechanized technology adoption rates have increased rapidly, the deployment of these technologies has been without critical analysis of the impacts on production patterns and local agrarian systems. This paper examines the distributional impacts of agriculture mechanization on cropping patterns and farm sizes of smallholder farmers in northern Ghana using Geographic Information Systems (GIS) techniques, and semi-structured interviews with smallholder farmers (n=60). Specifically, comparative analysis of the field sizes and cropping patterns of participant farmers prior to and after the adoption of mechanized technologies was conducted. In-depth interviews were used to contextualize the experiences of smallholder farmers toward understanding how mechanization may be impacting traditional agriculture. Our findings reveal a mechanization paradox in which farm sizes are expanding, while cropping patterns are shifting away from traditional staple crops (pearl millet and sorghum bicolor) to market-oriented crops (maize, rice and groundnuts). This transition we argue, has adverse implications on the cultural dimension of food security, the organization of social life, and climate change adaptation. We recommend a retooling of the current agricultural policy focus to ensure context sensitivity for a more robust battle against food insecurity. 相似文献
15.
Radi Abeer M. Abdel Azeem Naglaa M. EL-Nahass EL-Shaymaa 《Environmental science and pollution research international》2021,28(5):5158-5167
Environmental Science and Pollution Research - Zinc is an essential nutritional trace mineral required for growth and health. The aim of the current work is to compare the effects of bulk zinc... 相似文献
16.
17.
18.
19.
Francisco M. Baena-Moreno Mónica Rodríguez-Galán Fernando Vega Luis F. Vilches Benito Navarrete 《International Journal of Green Energy》2019,16(5):401-412
Biomethane production through biogas upgrading is a promising renewable energy for some industries which could be part of the equilibrium needed with fossil fuels consumption to achieve a sustainable society. This paper presents a comprehensive list of biogas upgrading technologies focused on carbon dioxide removal as well as recent advances reported by researcher with wide expertise in this topic. Additionally, an extensive costs–performance comparison among the technologies studied is discussed. Among the different alternatives, chemical scrubbing stood out to achieve high biomethane purities while cryogenic technologies proved to be effective against methane losses. Regarding the different costs, water scrubbing and membrane separation seem to be the most affordable techniques. 相似文献
20.