全文获取类型
收费全文 | 609篇 |
免费 | 26篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 18篇 |
废物处理 | 17篇 |
环保管理 | 130篇 |
综合类 | 116篇 |
基础理论 | 175篇 |
环境理论 | 3篇 |
污染及防治 | 116篇 |
评价与监测 | 37篇 |
社会与环境 | 24篇 |
灾害及防治 | 7篇 |
出版年
2023年 | 10篇 |
2022年 | 11篇 |
2021年 | 21篇 |
2020年 | 28篇 |
2019年 | 27篇 |
2018年 | 29篇 |
2017年 | 29篇 |
2016年 | 32篇 |
2015年 | 35篇 |
2014年 | 25篇 |
2013年 | 49篇 |
2012年 | 40篇 |
2011年 | 57篇 |
2010年 | 31篇 |
2009年 | 23篇 |
2008年 | 30篇 |
2007年 | 33篇 |
2006年 | 31篇 |
2005年 | 20篇 |
2004年 | 11篇 |
2003年 | 17篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有643条查询结果,搜索用时 640 毫秒
131.
Sarah S. Tzilkowski Anthony R. Buda Elizabeth W. Boyer Ray B. Bryant Peter J.A. Kleinman Casey D. Kennedy Arthur L. Allen Gordon J. Folmar Eric B. May 《Journal of the American Water Resources Association》2019,55(1):228-246
Urea‐N is a component of bioavailable dissolved organic nitrogen (DON) that contributes to coastal eutrophication. In this study, we assessed urea‐N in baseflow across land cover gradients and seasons in the Manokin River Basin on the Delmarva Peninsula. From March 2010 to June 2011, we conducted monthly sampling of 11 streams (4 tidal and 7 nontidal), 2 wastewater treatment plants, an agricultural drainage ditch, and groundwater underlying a cropped field. At each site, we measured urea‐N, DON, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), NO3?‐N, and NH4+‐N. In general, urea‐N comprised between 1% and 6% of TDN, with the highest urea‐N levels in drainage ditches (0.054 mg N/L) and wetland‐dominated streams (0.035–0.045 mg N/L). While urea‐N did not vary seasonally in tidal rivers, nontidal streams saw distinct urea‐N peaks in summer (0.038 mg N/L) that occurred several months after cropland fertilization in spring. Notably, the proportion of wetlands explained 78% of the variance in baseflow urea‐N levels across the Manokin watershed. In wetland‐dominated basins, we found urea‐N was positively related to water temperature and negatively related to DOC:DON ratios, indicating short‐term urea‐N dynamics at baseflow were more likely influenced by instream and wetland‐driven processes than by recent agricultural urea‐N inputs. Findings demonstrate important controls of wetlands on baseflow urea‐N concentrations in mixed land‐use basins. 相似文献
132.
Sarah A. Baker Andrew W. Wood Balaji Rajagopalan 《Journal of the American Water Resources Association》2019,55(4):1024-1037
We describe a new effort to enhance climate forecast relevance and usability through the development of a system for evaluating and displaying real‐time subseasonal to seasonal (S2S) climate forecasts on a watershed scale. Water managers may not use climate forecasts to their full potential due to perceived low skill, mismatched spatial and temporal resolutions, or lack of knowledge or tools to ingest data. Most forecasts are disseminated as large‐domain maps or gridded datasets and may be systematically biased relative to watershed climatologies. Forecasts presented on a watershed scale allow water managers to view forecasts for their specific basins, thereby increasing the usability and relevance of climate forecasts. This paper describes the formulation of S2S climate forecast products based on the Climate Forecast System version 2 (CFSv2) and the North American Multi‐Model Ensemble (NMME). Forecast products include bi‐weekly CFSv2 forecasts, and monthly and seasonal NMME forecasts. Precipitation and temperature forecasts are aggregated spatially to a United States Geological Survey (USGS) hydrologic unit code 4 (HUC‐4) watershed scale. Forecast verification reveals appreciable skill in the first two bi‐weekly periods (Weeks 1–2 and 2–3) from CFSv2, and usable skill in NMME Month 1 forecast with varying skills at longer lead times dependent on the season. Application of a bias‐correction technique (quantile mapping) eliminates forecast bias in the CFSv2 reforecasts, without adding significantly to correlation skill. 相似文献
133.
Sarah A. Ohrnberger Katharina Brinkmann Rupert Palme Teresa G. Valencak 《Die Naturwissenschaften》2018,105(1-2):13
Breeding of golden hamsters is classically performed at thermal conditions ranging from 20 to 24 °C. However, growing evidence suggests that lactating females suffer from heat stress. We hypothesised that shaving females dorsally to maximise heat dissipation may reduce stress during reproduction. We thus compared faecal cortisol metabolites (FCM) from shaved golden hamster mothers with those from unshaved controls. We observed significantly lower FCM levels in the shaved mothers (F1,22?=?8.69, p?=?0.0075) pointing to lower stress due to ameliorated heat dissipation over the body surface. In addition, we observed 0.4 °C lower mean subcutaneous body temperatures in the shaved females, although this effect did not reach significance (F1,22?=?1.86, p?=?0.18). Our results suggest that golden hamsters having body masses being more than four times that of laboratory mice provide a very interesting model to study aspects of lactation and heat production at the same time. 相似文献
134.
Levine Jordan Isaeva Aiganysh Eddy Ian Foggin Marc Gergel Sarah Hagerman Shannon Zerriffi Hisham 《Regional Environmental Change》2017,17(3):941-947
Regional Environmental Change - Despite internationally recognized definitions, there remains debate over what constitutes ‘actual’ degradation in various agro-pastoral contexts. This... 相似文献
135.
136.
137.
138.
139.
Cátia Canteiro Laísa Barcelos Fabiana Filardi Rafaela Forzza Laura Green João Lanna Paula Leitman William Milliken Marli Pires Morim Kristina Patmore Sarah Phillips Barnaby Walker Marie-Hélène Weech Eimear Nic Lughadha 《Conservation biology》2019,33(3):523-533
Herbarium specimens are increasingly recognized as an important resource for conservation science and virtual herbaria are making specimens freely available to a wider range of users than ever before. Few virtual herbaria are designed with conservation use as a primary driver. Exceptionally, Brazil's Reflora Virtual Herbarium (RVH) was created to increase knowledge and conservation of the Brazilian flora. The RVH is closely integrated with the Flora of Brazil 2020 platform on which Brazil's new national Flora is under construction. Both resources are accessible via the Reflora home page and thousands of users move seamlessly between these Reflora resources. To understand how the Reflora resources are currently used and their impact on conservation science, we conducted a literature review and an online survey. We searched for publications of studies in which Reflora resources were used and publications resulting from Brazilian researchers who were part of Reflora's research and mobility program. The survey contained multiple choice questions and questions that required a written response. We targeted Reflora webpage visitors with the survey to capture a wider range of Reflora users than the literature review. Reflora resources were used for a variety of conservation-relevant purposes. Half the 806 scientific publications in which Reflora was cited and 81% of the 1069 survey respondents accessing Reflora resources mentioned conservation-relevant research outputs. Most conservation-relevant uses of the Reflora resources in scientific publications were research rather than implementation focused. The survey of Reflora users showed conservation uses and impacts of virtual herbaria were more numerous and diverse than the uses captured in the literature review. Virtual herbaria are vital resources for conservation science, but they must document use and impacts more comprehensively to ensure sustainability. 相似文献
140.
Nicole L. Michel Sarah P. Saunders Timothy D. Meehan Chad B. Wilsey 《Conservation biology》2021,35(5):1484-1495
Evaluation of protected area effectiveness is critical for conservation of biodiversity. Protected areas that prioritize biodiversity conservation are, optimally, located and managed in ways that support relatively large and stable or increasing wildlife populations. Yet evaluating conservation efficacy remains a challenging endeavor. We used an extensive community science data set, eBird, to evaluate the efficacy of protected areas for birds across the Gulf of Mexico and Atlantic coasts of the United States. We modeled trends (2007–2018) for 12 vulnerable waterbirds that use coastal areas during breeding or wintering. We compared two types of protected areas—sites where conservation organizations implemented active stewardship or management or both to reduce human disturbance (hereafter stewardship sites) and local, state, federal, and private protected areas managed to maintain natural land cover (hereafter protected areas)—as well as unprotected areas. We evaluated differences in trends between stewardship, protected, and unprotected areas across the Gulf and Atlantic coasts as a whole. Similar to a background sample, stewardship was known to occur at stewardship sites, but unknown at protected and unprotected areas. Four of 12 target species—Black Skimmer (Rynchops niger), Brown Pelican (Pelecanus occidentalis), Least Tern (Sternula antillarum), and Piping Plover (Charadrius melodus)—had more positive trends (two to 34 times greater) at stewardship sites than protected areas. Furthermore, five target species showed more positive trends at sites with stewardship programs than unprotected sites during at least one season, whereas seven species showed more positive trends at protected than unprotected areas. No species had more negative trends at stewardship sites than unprotected areas, and two species had more negative trends at protected than unprotected areas. Anthropogenic disturbance is a serious threat to coastal birds, and our findings demonstrate that stewardship to reduce its negative impacts helps ensure conservation of vulnerable waterbirds. 相似文献