全文获取类型
收费全文 | 20340篇 |
免费 | 156篇 |
国内免费 | 123篇 |
专业分类
安全科学 | 410篇 |
废物处理 | 951篇 |
环保管理 | 2444篇 |
综合类 | 2544篇 |
基础理论 | 5697篇 |
环境理论 | 5篇 |
污染及防治 | 4768篇 |
评价与监测 | 1518篇 |
社会与环境 | 2206篇 |
灾害及防治 | 76篇 |
出版年
2022年 | 159篇 |
2021年 | 154篇 |
2020年 | 102篇 |
2019年 | 120篇 |
2018年 | 737篇 |
2017年 | 713篇 |
2016年 | 768篇 |
2015年 | 310篇 |
2014年 | 435篇 |
2013年 | 1232篇 |
2012年 | 688篇 |
2011年 | 1368篇 |
2010年 | 928篇 |
2009年 | 1019篇 |
2008年 | 1285篇 |
2007年 | 1523篇 |
2006年 | 674篇 |
2005年 | 648篇 |
2004年 | 564篇 |
2003年 | 665篇 |
2002年 | 647篇 |
2001年 | 739篇 |
2000年 | 516篇 |
1999年 | 277篇 |
1998年 | 212篇 |
1997年 | 199篇 |
1996年 | 192篇 |
1995年 | 238篇 |
1994年 | 181篇 |
1993年 | 152篇 |
1992年 | 173篇 |
1991年 | 168篇 |
1990年 | 195篇 |
1989年 | 178篇 |
1988年 | 135篇 |
1987年 | 123篇 |
1986年 | 104篇 |
1985年 | 133篇 |
1984年 | 147篇 |
1983年 | 120篇 |
1982年 | 123篇 |
1981年 | 106篇 |
1980年 | 104篇 |
1979年 | 110篇 |
1977年 | 82篇 |
1976年 | 73篇 |
1975年 | 79篇 |
1974年 | 77篇 |
1973年 | 84篇 |
1972年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
1.
2.
3.
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
4.
Carly E. Federman Durelle T. Scott Erich T. Hester 《Journal of the American Water Resources Association》2023,59(1):29-48
River flooding impacts human life and infrastructure, yet provides habitat and ecosystem services. Traditional flood control (e.g., levees, dams) reduces habitat and ecosystem services, and exacerbates flooding elsewhere. Floodplain restoration (i.e., bankfull floodplain reconnection and Stage 0) can also provide flood management, but has not been sufficiently evaluated for small frequent storms. We used 1D unsteady Hydrologic Engineering Center's River Analysis System to simulate small storms in a 5 km-long, second-order generic stream from the Chesapeake Bay watershed, and varied % channel restored (starting at the upstream end), restoration location, restoration bank height (distinguishes bankfull from Stage 0 restoration), and floodplain width/Manning's n. Stream restoration decreased (attenuated) peak flow up to 37% and increased floodplain exchange by up to 46%. Floodplain width and % channel restored had the largest impact on flood attenuation. The incremental effects of new restoration projects on flood attenuation were greatest when little prior restoration had occurred. By contrast, incremental effects on floodplain exchange were greatest in the presence of substantial prior restoration, setting up a tradeoff. A similar tradeoff was revealed between attenuation and exchange for project location, but not bank height or floodplain width. In particular, attenuation and exchange were always greater for Stage 0 than for bankfull floodplain restoration. Stage 0 thus may counteract human impacts such as urbanization. 相似文献
5.
6.
7.
8.
Quantitative methods have been applied to the study of floristic structure and diversity in Samarskaya Luka. The results show that Samarskaya Luka is a floristically heterogeneous area in which six elementary floras can be distinguished. This area has been assessed as a floristically autonomous formation, and its floristic representativeness was estimated. 相似文献
9.
10.