全文获取类型
收费全文 | 627篇 |
免费 | 13篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 27篇 |
废物处理 | 27篇 |
环保管理 | 146篇 |
综合类 | 52篇 |
基础理论 | 151篇 |
环境理论 | 1篇 |
污染及防治 | 138篇 |
评价与监测 | 66篇 |
社会与环境 | 25篇 |
灾害及防治 | 15篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 27篇 |
2013年 | 42篇 |
2012年 | 26篇 |
2011年 | 35篇 |
2010年 | 35篇 |
2009年 | 26篇 |
2008年 | 39篇 |
2007年 | 33篇 |
2006年 | 38篇 |
2005年 | 27篇 |
2004年 | 17篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有648条查询结果,搜索用时 31 毫秒
331.
The Gunnison River in the Black Canyon of the Gunnison National Park (BCNP) near Montrose, Colorado is a mixed gravel and
bedrock river with ephemeral side tributaries. Flow rates are controlled immediately upstream by a diversion tunnel and three
reservoirs. The management of the hydraulic control structures has decreased low-frequency, high-stage flows, which are the
dominant geomorphic force in bedrock channel systems. We developed a simple model to estimate the extent of sediment mobilization
at a given flow in the BCNP and to evaluate changes in the extent and frequency of sediment mobilization for flow regimes
before and after flow regulation in 1966. Our methodology provides a screening process for identifying and prioritizing areas
in terms of sediment mobility criteria when more precise systematic field data are unavailable. The model uses the ratio between
reach-averaged bed shear stress and critical shear stress to estimate when a particular grain size is mobilized for a given
reach. We used aerial photography from 1992, digital elevation models, and field surveys to identify individual reaches and
estimate reach-averaged hydraulic geometry. Pebble counts of talus and debris fan deposits were used to estimate regional
colluvial grain-size distributions. Our results show that the frequency of flows mobilizing river bank sediment along a majority
of the Gunnison River in the BCNP has significantly declined since 1966. The model results correspond well to those obtained
from more detailed, site-specific field studies carried out by other investigators. Decreases in the frequency of significant
sediment-mobilizing flows were more pronounced for regions within the BCNP where the channel gradient is lower. Implications
of these results for management include increased risk of encroachment of vegetation on the active channel and long-term channel
narrowing by colluvial deposits. It must be recognized that our methodology represents a screening of regional differences
in sediment mobility. More precise estimates of hydraulic and sediment parameters would likely be required for dictating quantitative
management objectives within the context of sediment mobility and sensitivity to changes in the flow regime. 相似文献
332.
Rebecca M. Ford Kathryn J. H. Williams Ian D. Bishop John E. Hickey 《Environmental management》2009,44(6):1149-1162
The effects of viewing different types of information were investigated in people judging the social acceptability of alternative
forest harvest systems. Approximately 500 Tasmanians were shown still-simulated images of four harvest systems (a clearfell
system, two aggregated retention systems, and a selective system) and were asked to judge their acceptability. Individual
interviews were conducted with 12 of the participants. It was anticipated that people holding different beliefs about the
consequences of harvesting would have different responses to information. Cluster analysis was used to group participants
according to these beliefs. Responses to still images were compared with responses to two other types of information: information
about consequences of the harvest systems in the form of indicator symbols, and information about regeneration over time,
presented as visual animations. The effects of information differed across both harvest system and belief cluster groups of
participants. The largest effects of information occurred in people who held a mix of beliefs about consequences. Within this
group, participants who viewed the indicators rated a 30% aggregated retention system higher and selective harvesting lower,
than those who did not view the indicators. Viewing animated sequences led to slightly higher ratings of the more intensive
harvest systems and significantly lower ratings of the selective harvest system than those based on the still images. The
interview data provided examples of interviewees viewing information critically against their own values and beliefs. Only
some interviewees appeared to use it in judging social acceptability 相似文献
333.
334.
User behaviour, best practice and the risks of non-target exposure associated with anticoagulant rodenticide use 总被引:1,自引:0,他引:1
Tosh DG Shore RF Jess S Withers A Bearhop S Ian Montgomery W McDonald RA 《Journal of environmental management》2011,92(6):1503-1508
Usage of anticoagulant rodenticides (ARs) is an integral component of modern agriculture and is essential for the control of commensal rodent populations. However, the extensive deployment of ARs has led to widespread exposure of a range of non-target predatory birds and mammals to some compounds, in particular the second-generation anticoagulant rodenticides (SGARs). As a result, there has been considerable effort placed into devising voluntary best practice guidelines that increase the efficacy of rodent control and reduce the risk of non-target exposure. Currently, there is limited published information on actual practice amongst users or implementation of best practice. We assessed the behaviour of a typical group of users using an on-farm questionnaire survey. Most baited for rodents every year using SGARs. Most respondents were apparently aware of the risks of non-target exposure and adhered to some of the best practice recommendations but total compliance was rare. Our questionnaire revealed that users of first generation anticoagulant rodenticides rarely protected or checked bait stations, and so took little effort to prevent primary exposure of non-targets. Users almost never searched for and removed poisoned carcasses and many baited for prolonged periods or permanently. These factors are all likely to enhance the likelihood of primary and secondary exposure of non-target species. 相似文献
335.
Ohlberger J Langangen Ø Edeline E Claessen D Winfield IJ Stenseth NC Vøllestad LA 《Ecology》2011,92(12):2175-2182
Recently developed theoretical models of stage-structured consumer-resource systems have shown that stage-specific biomass overcompensation can arise in response to increased mortality rates. We parameterized a stage-structured population model to simulate the effects of increased adult mortality caused by a pathogen outbreak in the perch (Perca fluviatilis) population of Windermere (UK) in 1976. The model predicts biomass overcompensation by juveniles in response to increased adult mortality due to a shift in food-dependent growth and reproduction rates. Considering cannibalism between life stages in the model reinforces this compensatory response due to the release from predation on juveniles at high mortality rates. These model predictions are matched by our analysis of a 60-year time series of scientific monitoring of Windermere perch, which shows that the pathogen outbreak induced a strong decrease in adult biomass and a corresponding increase in juvenile biomass. Age-specific adult fecundity and size at age were higher after than before the disease outbreak, suggesting that the pathogen-induced mortality released adult perch from competition, thereby increasing somatic and reproductive growth. Higher juvenile survival after the pathogen outbreak due to a release from cannibalism likely contributed to the observed biomass overcompensation. Our findings have general implications for predicting population- and community-level responses to increased size-selective mortality caused by exploitation or disease outbreaks. 相似文献
336.
Increasing concerns about the ecological impacts of ongoing and possibly worsening blooms of the toxic, carcinogenic cyanobacteria
Lyngbya majuscula in Moreton Bay, Australia, led us to assess differences in meiofaunal prey assemblages between bloom and non-bloom substrates
and the potential dietary impacts of dense L. majuscula blooms on the omnivorous benthivore, the Eastern Long-finned Goby, Favonigobius lentiginosus and the obligate meiobenthivorous juveniles of Trumpeter Whiting, Sillago maculata. Marked differences in invertebrate communities were found between sandy and L. majuscula bloom foraging substrates, with copepods significantly more abundant (18.49% vs. 70.44% numerical abundance) and nematodes
significantly less abundant (55.91% vs. 1.21% numerical abundance) within bloom material. Gut analyses showed that bentho-planktivorous
fishes exposed to L. majuscula in captivity had consumed a significantly greater quantity of prey by both total number (P < 0.0019) and volume (P < 0.0006) than fish exposed to sand treatments. Thus, it is likely for such fishes that L. majuscula blooms increase rates of prey encounter and consumption, with consequent changes in trophic relationships through shifts
in predator–prey interactions between small benthivorous fishes and their meiofaunal prey. 相似文献
337.
Policy shocks affect the rent distribution in long-term contracts, which can lead to such contracts being renegotiated. We seek an understanding of what aspects of contract design, in the face of a substantial policy shock, affect the propensity to renegotiate. We test our hypotheses using data on U.S. coal contracts after the policy shock of the 1990 Clean Air Act Amendments. Contracts are divided into two categories, those that were renegotiated following the shock and those that were not. Characteristics of the contract are used to explain whether or not the contract was ultimately renegotiated. Results provide guidance on rent re-distribution and contract renegotiation more generally and are applicable to contemporary policy issues such as climate change legislation. 相似文献
338.
Measurement of environmental pollutants using passive sampling devices--a commentary on the current state of the art 总被引:1,自引:0,他引:1
Mills GA Greenwood R Vrana B Allan IJ Ocelka T 《Journal of environmental monitoring : JEM》2011,13(11):2979-2982
Passive sampling devices have been used since the 1970s to measure time-weighted average (TWA) or equilibrium concentrations of pollutants in various environmental matrices (e.g. air, soils and sediments and water). In recent years the popularity of using such samplers has increased and the technology in now well established for the measurement of atmospheric pollutants. This sector has a long experience of using passive samplers in the short- and long-term assessment of air quality in the local environment and on a global scale (e.g. within the United Nations Stockholm Convention on the trans-boundary movement of persistent organic pollutants (POPs) where large networks of samplers on a continental scale have been established). In comparison, the use of passive samplers for monitoring the aquatic environment has been slower to take off. There has, however, been a recent research drive to develop devices for measuring the wide range of pollutants that can be found in environmental waters (e.g. ground, surface, and marine). It is now being recognised that passive samplers can play a valuable role in monitoring water quality within a legislative framework such as the European Union's Water Framework Directive (WFD). The data from these devices can be used alongside the results obtained from conventional spot or bottle sampling to improve risk assessments and to inform decisions on undertaking potentially expensive remedial actions. Such monitoring techniques may have uses within the European Registration, Evaluation, Authorisation & restriction of CHemicals (REACH) Directive and the forthcoming European Marine Strategy Directive. It is expected that the aquatic monitoring sector will follow a transition similar to that which occurred in air monitoring where data obtained from passive samplers can use used within a legal framework. There has also been increased interest in extending the role of passive samplers to both the measurement of equilibrium concentrations and investigating the movement and release of the dissolved fraction of various pollutants in the pore water of sediments and soils. 相似文献
339.
340.
Host-plant-mediated competition via induced resistance: interactions between pest herbivores on potatoes. 总被引:1,自引:0,他引:1
Margaret E Lynch Ian Kaplan Galen P Dively Robert F Denno 《Ecological applications》2006,16(3):855-864
Plant-mediated competition among insect herbivores occurs when one species induces changes in plant chemistry, nutrition, or morphology that render plants resistant to attack by others. We explored plant-mediated interspecific interactions between the potato leafhopper (Empoasca fabae) and the Colorado potato beetle (Leptinotarsa decemlineata), two important pests on potatoes. Leafhoppers colonize fields in advance of beetles, and thus the possibility exists that previous feeding by leafhoppers induces changes in potato plants that have adverse consequences for beetles. The consequences of leafhopper-induced resistance for beetle performance were studied in the greenhouse, field cages, and in large open-field plots. Potato plants were exposed to four densities of leafhoppers (none, low, moderate, and high), and visible feeding symptoms were measured as percentage leaf curling, chlorosis, and necrosis. The oviposition preference, performance, and survivorship of Colorado potato beetles were then measured on the four categories of induced plants in field-cage and greenhouse settings. In open field plots, survival on the four categories of induced plants was determined by placing cohorts of beetle adults onto plants and measuring the densities of resulting eggs, larvae, and emerging Fl adults. Leafhopper-induced symptoms on potato plants were density dependent, with the percentage of curled, chlorotic, and necrotic leaves increasing with leafhopper density. Previous feeding by leafhoppers adversely affected oviposition and larval performance of beetles. Fewer egg masses were deposited on plants that incurred high levels of leafhopper feeding. Similarly, larval development was delayed and emerging adult beetles weighed less when fed induced foliage from the high leafhopper-density treatment. Beetles survived less well in the field on plants experiencing moderate and high levels of leafhopper feeding as evidenced by lower densities of eggs, larvae, and emerging F1 adults. Overall, leafhoppers and beetles competed through feeding-induced changes in plant quality. Notably, the asymmetric interaction took place at a large spatial scale in open field plots and had negative consequences that persisted to the next beetle generation. Ultimately, to establish an effective management strategy for crop pests such as leafhoppers, it is essential to consider the positive indirect effects of induced resistance along with the negative direct effects on crop yield. 相似文献