全文获取类型
收费全文 | 2801篇 |
免费 | 69篇 |
国内免费 | 25篇 |
专业分类
安全科学 | 107篇 |
废物处理 | 118篇 |
环保管理 | 590篇 |
综合类 | 245篇 |
基础理论 | 847篇 |
环境理论 | 5篇 |
污染及防治 | 614篇 |
评价与监测 | 189篇 |
社会与环境 | 150篇 |
灾害及防治 | 30篇 |
出版年
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 42篇 |
2020年 | 39篇 |
2019年 | 41篇 |
2018年 | 63篇 |
2017年 | 60篇 |
2016年 | 95篇 |
2015年 | 80篇 |
2014年 | 82篇 |
2013年 | 253篇 |
2012年 | 104篇 |
2011年 | 187篇 |
2010年 | 116篇 |
2009年 | 144篇 |
2008年 | 157篇 |
2007年 | 162篇 |
2006年 | 131篇 |
2005年 | 106篇 |
2004年 | 92篇 |
2003年 | 94篇 |
2002年 | 78篇 |
2001年 | 54篇 |
2000年 | 41篇 |
1999年 | 45篇 |
1998年 | 33篇 |
1997年 | 34篇 |
1996年 | 38篇 |
1995年 | 46篇 |
1994年 | 37篇 |
1993年 | 33篇 |
1992年 | 28篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 13篇 |
1984年 | 28篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1975年 | 12篇 |
1974年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有2895条查询结果,搜索用时 858 毫秒
1.
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
2.
Regional Environmental Change - Agro-ecosystem energy profiles reveal energy flows into, within, and out of US Great Plains farm communities across 140 years. This study evaluates external... 相似文献
3.
4.
A new, simple method for directly measuring activated sludge density was developed and applied, and the effects of biomass density on activated sludge settling in full-scale systems were evaluated. The driving force of sedimentation is the physical weight of the biological solids, but the role of biomass density in sedimentation has been largely ignored. Biomass density varied amongst treatment systems and this variability was correlated with settleability. Floc densities were approximately normally distributed within individual samples. Nonsoluble phosphorus content was a major contributor to density, and plants with enhanced biological phosphorus removal (EBPR) configurations generally had higher densities and better settleability than non-EBPR plants with similar filament contents. These results suggest that future work may benefit from consideration of density as a factor affecting activated sludge settling. 相似文献
5.
Henrietta M. Lidiard Joy E. Rae Andrew Parker 《Environmental geochemistry and health》1993,15(2-3):93-104
A number of Mn-oxide minerals in soils from a farm in North Devon have been tentatively identified using a combination of
advanced analytical techniques: scanning electron microscopy (SEM), scanning electron microprobe (SEMP), X-ray diffraction
(XRD) and bulk chemical analysis by wet digestion followed by inductively-coupled plasma spectrometry (ICP). The minerals
lithiophorite and hollandite are thought to occur throughout the study area although there is considerable geographical variation
in the proportions of minerals present. Bimessite, vernadite, romanechite, todorokite and cryptomelane may also be present,
although in smaller amounts.
The use of SEMP, together with a simple sorption experiment, has allowed a study of the extent of uptake of Co and Cu by different
Mn-oxide minerals. Lithiophorite appears to take up Co and Cu more effectively than hollandite within a pH range of 4–6. 相似文献
6.
7.
8.
9.
10.