全文获取类型
收费全文 | 2454篇 |
免费 | 11篇 |
国内免费 | 7篇 |
专业分类
安全科学 | 42篇 |
废物处理 | 87篇 |
环保管理 | 146篇 |
综合类 | 758篇 |
基础理论 | 437篇 |
环境理论 | 7篇 |
污染及防治 | 749篇 |
评价与监测 | 136篇 |
社会与环境 | 104篇 |
灾害及防治 | 6篇 |
出版年
2022年 | 36篇 |
2021年 | 33篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 55篇 |
2017年 | 57篇 |
2016年 | 78篇 |
2015年 | 43篇 |
2014年 | 90篇 |
2013年 | 145篇 |
2012年 | 66篇 |
2011年 | 127篇 |
2010年 | 78篇 |
2009年 | 84篇 |
2008年 | 122篇 |
2007年 | 112篇 |
2006年 | 92篇 |
2005年 | 88篇 |
2004年 | 64篇 |
2003年 | 58篇 |
2002年 | 61篇 |
2001年 | 63篇 |
2000年 | 41篇 |
1999年 | 34篇 |
1998年 | 20篇 |
1997年 | 23篇 |
1996年 | 19篇 |
1995年 | 21篇 |
1994年 | 34篇 |
1993年 | 15篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1986年 | 13篇 |
1984年 | 14篇 |
1981年 | 17篇 |
1969年 | 14篇 |
1968年 | 13篇 |
1967年 | 16篇 |
1966年 | 24篇 |
1965年 | 29篇 |
1964年 | 18篇 |
1963年 | 26篇 |
1962年 | 23篇 |
1961年 | 31篇 |
1960年 | 21篇 |
1959年 | 21篇 |
1958年 | 14篇 |
1957年 | 25篇 |
1956年 | 16篇 |
1955年 | 16篇 |
排序方式: 共有2472条查询结果,搜索用时 15 毫秒
811.
W. Schäfer 《Die Naturwissenschaften》1937,25(14):218-219
812.
Relation between extinction and assisted colonization of plants in the arctic‐alpine and boreal regions 下载免费PDF全文
Juha Pykälä 《Conservation biology》2017,31(3):524-530
Assisted colonization of vascular plants is considered by many ecologists an important tool to preserve biodiversity threatened by climate change. I argue that assisted colonization may have negative consequences in arctic‐alpine and boreal regions. The observed slow movement of plants toward the north has been an argument for assisted colonization. However, these range shifts may be slow because for many plants microclimatic warming (ignored by advocates of assisted colonization) has been smaller than macroclimatic warming. Arctic‐alpine and boreal plants may have limited possibilities to disperse farther north or to higher elevations. I suggest that arctic‐alpine species are more likely to be driven to extinction because of competitive exclusion by southern species than by increasing temperatures. If so, the future existence of arctic‐alpine and boreal flora may depend on delaying or preventing the migration of plants toward the north to allow northern species to evolve to survive in a warmer climate. In the arctic‐alpine region, preventing the dispersal of trees and shrubs may be the most important method to mitigate the negative effects of climate change. The purported conservation benefits of assisted colonization should not be used to promote the migration of invasive species by forestry. 相似文献
813.
814.
Katja Kangas Anne Tolvanen Tarja Kälkäjä Pirkko Siikamäki 《Environmental management》2009,44(3):408-419
Outdoor recreation and nature-based tourism represent an increasingly intensive form of land use that has considerable impacts
on native ecosystems. The aim of this paper is to investigate how revegetation and management of ski runs influence soil nutrients,
vegetation characteristics, and the possible invasion of nonnative plant species used in revegetation into native ecosystems.
A soil and vegetation survey at ski runs and nearby forests, and a factorial experiment simulating ski run construction and
management (factors: soil removal, fertilization, and seed sowing) were conducted at Ruka ski resort, in northern Finland,
during 2003–2008. According to the survey, management practices had caused considerable changes in the vegetation structure
and increased soil nutrient concentrations, pH, and conductivity on the ski runs relative to nearby forests. Seed mixture
species sown during the revegetation of ski runs had not spread to adjacent forests. The experimental study showed that the
germination of seed mixture species was favored by treatments simulating the management of ski runs, but none of them could
eventually establish in the study forest. As nutrient leaching causes both environmental deterioration and changes in vegetation
structure, it may eventually pose a greater environmental risk than the spread of seed mixture species alone. Machine grading
and fertilization, which have the most drastic effects on soils and vegetation, should, therefore, be minimized when constructing
and managing ski runs. 相似文献
815.
The concentration of dissolved reactive phosphorus (DRP) in rivers can change intermittently within minutes depending on the weather and water discharge (Q), or activities in the watershed. Accordingly, accurate estimation of the annual DRP load requires frequent sampling or even continuous monitoring, which is laborious and cost-intensive. We present the design and laboratory evaluation of a new, robust, low-cost, low-tech device based on passive samplers (P-traps). The traps use Fe-(oxy)hydroxide coated quartz sand as an adsorbent enclosed in a vertical grid of individual cells separated from the river water by filter membranes. They are inexpensive, easy to handle, resistant to repeated desiccation and immersion and exposable for several months. They permit estimation of discharge dependent time weighted average DRP concentrations (C-Q relationships) and annual P loads of rivers characterized by highly variable DRP concentrations with a relative accuracy of +/- 3%. 相似文献
816.
Human-induced eutrophication, resulting in algal blooms and increased water turbidity, is an alarming problem in aquatic systems.
Here, we experimentally tested the impact of algal turbidity on parental care, egg fanning, and time in the nest, in the sand
goby, Pomatoschistus minutus, a fish with uniparental male care. We allowed males to care for their eggs in either clear water or water made turbid by
planktonic algae. In the early brood cycle, males fanned their eggs less in turbid than in clear water, but this difference
disappeared later. Despite decreased care, egg survival was higher in turbid conditions, indicating that early fanning may
partly be redundant for egg survival and perhaps used more as courtship. Males also spent more time out of their nest in turbid
water, perhaps as a means to encounter additional females under conditions of low visibility. 相似文献
817.
818.
The recent growth in the size of dairy cattle farms and the concentration of farms into smaller areas in Finland may increase local water pollution due to increased manure production and slurry application to grass. Therefore, a field study was conducted to monitor losses of total phosphorus (TP), dissolved reactive phosphorus (DRP), and fecal microorganisms in surface runoff from a perennial ley. Cattle slurry was added once a year in June 1996-1997 (Study I) and biannually in June and October 1998-2000 (Study II). The slurry was surface broadcast or injected into the clay soil. The field had a slope of 0.9 to 1.7%. Mineral fertilizer was applied on control plots. Biannual slurry broadcasting increased DRP (p < 0.001) and TP losses (p < 0.001) and numbers of fecal microorganisms in surface runoff waters. The highest losses of TP (2.7 kg ha(-1) yr(-1)) and DRP (2.2 kg ha(-1) yr(-1)) and the highest numbers of fecal coliforms (880 colony-forming units [CFU] per 100 mL) and somatic coliphages (2700 plaque-forming units [PFU] per 100 mL) were measured after broadcasting slurry to wet soil followed by rainfall in fall 1998. Injection reduced the TP and DRP losses in surface runoff by 79 and 86%, respectively, compared with broadcasting (17 Oct. 1998-27 Oct. 1999). Corresponding numbers for fecal coliforms were 350 CFU (100 mL)(-1) and for somatic coliphages were 110 PFU (100 mL)(-1) in surface runoff after injection in October 1998. Slurry injection should be favored when spreading slurry amendments to grassland to avoid losses of P and fecal microorganisms in runoff to surface waters. 相似文献
819.
820.
Mathilde Stomp Maël Leroux Marjorie Cellier Séverine Henry Martine Hausberger Alban Lemasson 《Die Naturwissenschaften》2018,105(9-10):57
While the vocal coding of human and animal internal states has been widely studied, the possible acoustic expression of “positive” emotions remains poorly known. Recent studies suggest that snorts (non-vocal sounds produced by the air expiration through the nostrils) appear to be reliable indicators of positive internal states in several ungulate species. Here, we hypothesised in horses that the acoustic structure of the snort could vary with the subjects’ current emotional state. Indeed, a preliminary sound analysis of snorts let us suggest structure variations related to the presence of pulsations. We recorded snorts from 20 horses living in a riding center. Auditory playbacks run with 20 humans first confirmed the existence of two snort subtypes, i.e. one pulsed and one non-pulsed. Observations were then conducted to compare the distribution of these two subtypes according to the location (stall/pasture) of the signaller as a contextual determinant of its internal state and to its ears’ position as a reflection of its emotional state. We found that both subtypes were preferentially observed in positive contexts, but that pulsed snorts were even more associated with highly appreciated situations (in pasture and with ears forward). This study is a step further in the identification of indicators of positive emotions in horses and more generally in the understanding of the acoustic emotions’ coding. 相似文献