全文获取类型
收费全文 | 95篇 |
免费 | 0篇 |
专业分类
安全科学 | 2篇 |
废物处理 | 7篇 |
环保管理 | 12篇 |
综合类 | 19篇 |
基础理论 | 24篇 |
污染及防治 | 16篇 |
评价与监测 | 8篇 |
社会与环境 | 6篇 |
灾害及防治 | 1篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有95条查询结果,搜索用时 31 毫秒
61.
Neurochemical studies on characterized neurons 总被引:3,自引:0,他引:3
62.
63.
64.
Disturbance and recovery of large floodplain rivers 总被引:7,自引:0,他引:7
Richard E. Sparks Peter B. Bayley Steven L. Kohler Lewis L. Osborne 《Environmental management》1990,14(5):699-709
Disturbance in a river-floodplain system is defined as an unpredictable event that disrupts structure or function at the ecosystem,
community, or population level. Disturbance can result in species replacements or losses, or shifts of ecosystems from one
persistent condition to another. A disturbance can be a discrete event or a graded change in a controlling factor that eventually
exceeds a critical threshold.
The annual flood is the major driving variable that facilitates lateral exchanges of nutrients, organic matter, and organisms.
The annual flood is not normally considered a disturbance unless its timing or magnitude is “atypical.” The record flood of
1973 had little effect on the biota at a long-term study site on the Mississippi River, but the absence of a flood during
the 1976–1977 Midwestern drought caused short- and long-term changes. Body burdens of contaminants increased temporarily in
key species, because of increased concentration resulting from reduced dilution. Reduced runoff and sediment input improved
light penetration and increased the depth at which aquatic macrophytes could grow. Developing plant beds exerted a high degree
of biotic control and were able to persist, despite the resumption of normal floods and turbidity in subsequent years.
In contrast to the discrete event that disturbed the Mississippi River, a major confluent, the Illinois River, has been degraded
by a gradual increase in sediment input and sediment resuspension. From 1958 to 1961 formerly productive backwaters and lakes
along a 320-km reach of the Illinois River changed from clear, vegetated areas to turbid, barren basins. The change to a system
largely controlled by abiotic factors was rapid and the degraded condition persists.
Traditional approaches to experimental design are poorly suited for detecting control mechanisms and for determining the critical
thresholds in large river-floodplains. Large river-floodplain systems cannot be manipulated or sampled as easily as small
streams, and greater use should be made of man-made or natural disturbances and environmental restoration as opportunistic
experiments to measure thresholds and monitor the recovery process.
Coauthors are listed in alphabetical order. 相似文献
65.
Nannochloris atomus was maintained in exponential growth at photon flux densities (PFD) from 400 to 700 nm, ranging from 10 to 200 mol m-2 s-1. Growth was lightsaturated at PFDs in excess of 100 mol m-2 s-1, with a mean light-saturated growth rate at 23 °C of 1.5×10-5s-1 (1.2 d-1). The light-limited growth rates extrapolated to a compensation PFD for growth that was not significantly different from zero, although no changes in cell numbers were observed in a single culture incubated at a PFD of 1.0 mol m-2s-1. Dark-respiration rates were independent of PFD, averaging 1.7×10-6 mol O2 mol-1 C s-1 (0.14 mol O2 mol-1 C d-1). The maximum photon (quantum) efficiency of photosynthesis was also independent of PFD, with a mean value of 0.12 mol O2 mol-1 photon. The chlorophyll a-specific light absorption cross-section ranged from 3 to 6×10-3 m2 mg-1 chl a and was lowest at low PFDs due to intracellular self-shading of pigments associated with high cell-chlorophyll a contents. The C:chl a ratio increased from 10 to 40 mg C mg-1 chl a between PFDs of 14 and 200 mol m-2 s-1. These new observations for N. atomus are compared with our previous observations for the diatom Phaeodactylum tricornutum in terms of an energy budget for microalgal growth. 相似文献
66.
The relationship between in vivo light absorption efficiency of whole cells and in vitro absorption efficiency of algal pigments has been examined experimentally in the marine diatom Thalassiosira sp. In vitro absorption spectra were obtained for cells disrupted by either ultrasonic treatment or high-pressure shearing stress in a
low-temperature (-40°C) pressure cell. A dimensionless measure of the magnitude of the package effect (Q
a
*), calculated from the ratio of whole-cell to disrupted-cell absorption, ranged from about 0.5 at the blue absorption peak
of chlorophyll a (λ=435 nm) to 0.7 at the red chlorophyll a peak (λ=670 nm) to 1.0 at the absorption minimum (λ=600 nm). Cell diameter was found to be an inappropriate measure of size
for assessing the magnitude of the package effect. Instead, the effective optical diameter for calculation of intracellular
self-shading was found to be less than the cell diameter. This observation is consistent with the fact that most algal pigments
are contained within chloroplasts, and that chloroplast volume is necessarily smaller than cell volume. 相似文献
67.
68.
A survey of residents in an area subject to annual toxic cyanobacterial blooms was undertaken to examine potential health effects of cyanobacteria toxins. The survey assessed the health of marine recreational water users in Deception Bay/Bribie Island area in northern Moreton Bay, Queensland, which is exposed to blooms of the nuisance and potentially harmful cyanobacterium Lyngbya majuscula. A postal survey was mailed to 5000 residents with a response rate of 27%. High numbers of people (78%) responding to the survey reported recreational water activity in Moreton Bay. Of those having marine recreational water activity, 34% reported at least one symptom after exposure to marine waters, with skin itching the most reported (23%). Younger participants had greater water exposure and symptoms than older participants. Participants with greater exposures were more likely to have skin and eye symptoms than less exposed groups, suggesting agents in the marine environment may have contributed to these symptoms. Of those entering Moreton Bay waters 29 (2.7%) reported severe skin symptoms, 12 of whom attended a health professional. Six (0.6%) reported the classic symptoms of recreational water exposure to L. majuscula, severe skin symptoms in the inguinal region. Participants with knowledge of L. majuscula were less likely to report less skin, gastrointestinal and fever and headache symptoms. In conclusion, high numbers of participants reported symptoms after exposure to waters subject to L. majuscula blooms but only a small number appeared to be serious in nature suggesting limited exposure to toxins. 相似文献
69.
Shai Markman Naomi Hill Josephine Todrank Giora Heth Leon Blaustein 《Behavioral ecology and sociobiology》2009,63(8):1149-1155
Responding differentially to kin and non-kin is known to be adaptive in many species. One example is the inclusive fitness
benefits of reducing aggression toward closer relatives. Little is known, however, about the ability of animals to assess
differential degrees of genetic relatedness and to respond accordingly with differential levels of aggression. In the present
study, we tested whether aggressiveness between body mass-matched pairs of fire salamander (Salamandra infraimmaculata) larvae covaried with the genetic similarity between them. We quantified aggressiveness at three levels of genetic similarity
by selecting pairs within and across pools from recently genotyped populations. We also assessed aggression between pairs
of siblings. Aggression and associated injuries decreased as genetic similarity increased across the groups. These findings
suggest that cannibalistic salamanders can assess their degree of genetic relatedness to conspecifics and vary their behavioral
responses depending on the degree of similarity between them along a genetic relatedness continuum. 相似文献
70.
Andrew M. Reynolds Jennifer L. Swain Alan D. Smith Andrew P. Martin Juliet L. Osborne 《Behavioral ecology and sociobiology》2009,64(1):115-123
The availability of food resources changes over time and space, and foraging animals are constantly faced with choices about
how to respond when a resource becomes depleted. We hypothesise that flying insects like bees discover new food sources using
an optimal Lévy flight searching strategy and odour-mediated anemotaxis, as well as visual cues. To study these searching
patterns, foraging honeybees were trained to a scented feeder which was then removed. Two new unrewarding feeders, or ‘targets’,
were then positioned up- and downwind of the original location of the training feeder. The subsequent flight patterns of the
bees were recorded over several hundred metres using harmonic radar. We show that the flight patterns constitute an optimal
Lévy flight searching strategy for the location of the training feeder, a strategy that is also optimal for the location of
alternative food sources when patchily distributed. Scented targets that were positioned upwind of the original training feeder
were investigated most with the numbers of investigations declining with increasing distance from the original feeder. Scented
targets in downwind locations were rarely investigated and unscented targets were largely ignored, despite having the same
visual appearance as the rewarding training feeder. 相似文献