全文获取类型
收费全文 | 296篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 20篇 |
废物处理 | 4篇 |
环保管理 | 63篇 |
综合类 | 33篇 |
基础理论 | 91篇 |
环境理论 | 1篇 |
污染及防治 | 53篇 |
评价与监测 | 18篇 |
社会与环境 | 9篇 |
灾害及防治 | 12篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 19篇 |
2013年 | 26篇 |
2012年 | 11篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 7篇 |
2004年 | 16篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有304条查询结果,搜索用时 218 毫秒
101.
Long-term studies have revealed that the structure and dynamics of many tropical forests are changing, but the causes and consequences of these changes remain debated. To learn more about the forces driving changes within tropical forests, we investigated shifts in tree species composition over the past 25 years within the 50-ha Forest Dynamics Plot on Barro Colorado Island (BCI), Panama, and examined how observed patterns relate to predictions of (1) random population fluctuations, (2) carbon fertilization, (3) succession from past disturbance, (4) recovery from an extreme El Ni?o drought at the start of the study period, and (5) long-term climate change. We found that there have been consistent and directional changes in the tree species composition. These shifts have led to increased relative representations of drought-tolerant species as determined by the species' occurrence both across a gradient of soil moisture within BCI and across a wider precipitation gradient from a dry forest near the Pacific coast of Panama to a wet forest near its Caribbean coast. These nonrandom changes cannot be explained by stochastic fluctuations or carbon fertilization. They may be the legacy of the El Ni?o drought, or alternatively, potentially reflect increased aridity due to long-term climate change. By investigating compositional changes, we increased not only our understanding of the ecology of tropical forests and their responses to large-scale disturbances, but also our ability to predict how future global change will impact some of the critical services provided by these important ecosystems. 相似文献
102.
Robin?F.?A.?MoritzEmail author H.?Michael?G.?Lattorff Kendall?L.?Crous Randall?H.?Hepburn 《Behavioral ecology and sociobiology》2011,65(4):735-740
Workers of a queenless honeybee colony can requeen the colony by raising a new queen from a young worker brood laid by the
old queen. If this process fails, the colony becomes hopelessly queenless and workers activate their ovaries to lay eggs themselves.
Laying Cape honeybee workers (Apis mellifera capensis) produce female offspring as an additional pathway for requeening. We tested the frequency of successful requeening in ten
hopelessly queenless colonies. DNA genotyping revealed that only 8% of all queens reared in hopelessly queenless colonies
were the offspring of native laying worker offspring. The vast majority of queens resulted from parasitic takeovers by foreign
queens (27%) and invading parasitic workers (19%). This shows that hopelessly queenless colonies typically die due to parasitic
takeovers and that the parasitic laying workers are an important life history strategy more frequently used than in providing
a native queen to rescue the colony. Parasitism by foreign queens, which might enter colonies alone or accompanied by only
a small worker force is much more frequent than previously considered and constitutes an additional life history strategy
in Cape honeybees. 相似文献
103.
Robin M. Reich Raymond L. Czaplewski William A. Bechtold 《Environmental and Ecological Statistics》1994,1(3):201-217
In this study a cross-correlation statistic is used to analyse the spatial relationship among stand characteristics of natural, undisturbed shortleaf pine stands sampled during 1961–72 and 1972–82 in northern Georgia. Stand characteristics included stand age, site index, tree density, hardwood competition, and mortality. In each time period, the spatial cross-correlation statistic was used to construct cross-correlograms and cumulative cross-correlograms for all significant pairwise combination of stand characteristics. Both the cross-correlograms and cumulative cross-correlograms identified small-scale clustering and weak directional gradients for different stand characteristics in each time period. The cumulative cross-correlograms, which are based on inverse distance weighting were more sensitive in detecting small-scale clustering than the cross-correlograms based on a 0–1 weighting. Further analysis suggested that the significant cross-correlation observed among basal area growth and other stand characteristics were due, in a large part, on a subset of sample plots located in the northern part of the state, rather than regional or broad-scale variation as first thought. The ability to analyse the spatial relationship between two or more response surfaces should provide valuable insight in the development of ecosystem level models and assist decision makers in formulating pertinent policy on intelligent multiresource management. 相似文献
104.
105.
106.
James H. Fullard Hannah M. ter Hofstede John M. Ratcliffe Gerald S. Pollack Gian S. Brigidi Robin M. Tinghitella Marlene Zuk 《Die Naturwissenschaften》2010,97(1):53-61
The auditory thresholds of the AN2 interneuron and the behavioural thresholds of the anti-bat flight-steering responses that
this cell evokes are less sensitive in female Pacific field crickets that live where bats have never existed (Moorea) compared
with individuals subjected to intense levels of bat predation (Australia). In contrast, the sensitivity of the auditory interneuron,
ON1 which participates in the processing of both social signals and bat calls, and the thresholds for flight orientation to
a model of the calling song of male crickets show few differences between the two populations. Genetic analyses confirm that
the two populations are significantly distinct, and we conclude that the absence of bats has caused partial regression in
the nervous control of a defensive behaviour in this insect. This study represents the first examination of natural evolutionary
regression in the neural basis of a behaviour along a selection gradient within a single species. 相似文献
107.
Norris Lam Marcus Nathanson Niclas Lundgren Robin Rehnström Steve W. Lyon 《Journal of the American Water Resources Association》2015,51(5):1211-1220
This brief pilot study implements a camera‐based laser scanning system that potentially offers a viable, cost‐effective alternative to traditional terrestrial laser scanning (TLS) and LiDAR equipment. We adapted a low‐cost laser ranging system (SICK LSM111) to acquire area scans of the channel and bed for a temporarily diverted stream. The 5 m × 2 m study area was scanned at a 4 mm point spacing which resulted in a point cloud density of 5,600 points/m2. A local maxima search algorithm was applied to the point cloud and a grain size distribution of the stream bed was extracted. The 84th and 90th percentiles of this distribution, which are commonly used to characterize channel roughness, were 90 mm and 109 mm, respectively. Our example shows the system can resolve both large‐scale geometry (e.g., bed slope and channel width) and small‐scale roughness elements (e.g., grain sizes between about 30 and 255 mm) in an exposed stream channel thereby providing a resolution adequate for the estimation of ecohydraulic roughness parameters such as Manning's n. While more work is necessary to refine our specific field‐deployable system's design, these initial results are promising in particular for those working on a limited or fixed budget. This opens up a realm of laser scanning applications and monitoring strategies for water resources that may not have been possible previously due to cost limitations associated with traditional TLS systems. 相似文献
108.
Robin Elahi Charles Birkeland Kenneth P. Sebens Kevin R. Turner Timothy R. Dwyer 《Marine Biology》2013,160(12):3209-3219
A unique archive of photographs from 1969 to 1974 permitted a test of the hypothesis that the diversity and composition of contemporary epilithic communities on subtidal rock walls in the San Juan Islands, WA, USA, has changed over 40 years. Notably, the richness and diversity of sessile taxa was significantly higher in 2008–2011. Furthermore, the multivariate community structure of sessile and mobile taxa differed between the historic and modern eras. Historic communities were characterized by a high percent cover of bare rock and non-calcified algal crusts, consistent with the effects of grazing by chitons and urchins. The rate of sessile community turnover, an index less susceptible to spatial sampling artifacts than richness or diversity, was not significantly different between the two eras. Together with the naturally high spatial variability in these epilithic communities, and the limited replication of historic quadrats, we interpret cautiously the data as evidence of limited change despite a clear shift in temperature and predator (fish) guild composition. The lack of substantial change in rock wall communities may be due in part to their vertical topography, which limits physical disturbance and the preemption of space by weedy algae, two processes that are often associated with “phase-shifts” in other marine ecosystems. 相似文献
109.
Industrial discharges of Al are increasingly common. In this study, the activities of three antioxidases, malondialdehyde (MDA) content and changes in coelomocytes were investigated in earthworms (Eisenia andrei) exposed to different concentrations of aluminium chloride (range 0–200 mg Al kg?1 dry soil) in artificial soils for 32 days. Within the first 16 days of Al exposure, catalase activity was elevated in most treatments, while the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were inhibited in all treatments. After 16 days exposure, SOD and GSH-Px activities returned to normal at lower Al concentrations, but were still inhibited at higher concentrations, hence the inhibition of SOD and GSH-Px showed some exposure-level dependence during the late exposure phase. MDA content was significantly elevated from 16 days after initial exposure. Neutral Red retention time of coelomocytes decreased at the highest exposure concentrations after 32 days, and an increased proportion of cells showing membrane damage was also observed at this time using flow cytometry. We conclude that excessive Al in soils can cause oxidative stress and cell damage in earthworms. Hence, Al accumulation in the environment may present an ecological hazard through suppression of the important functions of earthworms in soil ecosystems. 相似文献
110.
Bogdan I. Gherman Andreas Denner Otilia Bobiş Daniel S. Dezmirean Liviu A. Mărghitaş Helge Schlüns Robin F. A. Moritz Silvio Erler 《Behavioral ecology and sociobiology》2014,68(11):1777-1784
Honeybees, Apis mellifera, have several prophylactic disease defense strategies, including the foraging of antibiotic, antifungal, and antiviral compounds of plant products. Hence, honey and pollen contain many compounds that prevent fungal and bacterial growth and inhibit viral replication. Since these compounds are also fed to the larvae by nurse bees, they play a central role for colony health inside the hive. Here, we show that honeybee nurse bees, infected with the microsporidian gut parasite Nosema ceranae, show different preferences for various types of honeys in a simultaneous choice test. Infected workers preferred honeys with a higher antibiotic activity that reduced the microsporidian infection after the consumption of the honey. Since nurse bees feed not only the larvae but also other colony members, this behavior might be a highly adaptive form of therapeutic medication at both the individual and the colony level. 相似文献