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51.
Stages in the life cycle of the rhizostome jellyfish Rhizostoma octopus (L.) were reared in the laboratory from planula to young medusa and are described here. Fertilization of eggs was external,
and planulae, 110–150 μm in length, appeared after 2 days. These settled and developed into the scyphistoma stage. Scyphistomae
reached a maximum size of 2.3 mm, bore up to 24 tentacles, and had a large manubrium. Polyps reproduced asexually mainly by
podocysts. Strobilation was induced by temperature change. Each strobila released up to five ephyrae that measured 2.7–5.8 mm
in diameter at liberation. During transformation from newly released ephyra to young medusa, velar lappets appeared and increased
in number, the manubrium developed eight branched oral arms with epaulettes, and a marginal gastric network arose. Only one
cnidocyst type, the “a”-atrichous haploneme, was present in the planula. In addition to these haplonemes, heterotrichous microbasic
euryteles were observed in polyps, ephyrae, and medusae. Statoliths, located in the rhopalia, had a characteristic compact
shape. These sensory structures increased in number and size with the growth of ephyrae and medusae. 相似文献
52.
Henry F. Howe 《Conservation biology》1994,8(3):691-704
Conservation and restoration ecology efforts may conserve or restore a particular image of a community, a variety of plausible images, or maximum biological diversity. The choice is a policy decision that should reflect relevant history and sound science. Here I argue that common methods of conserving and restoring tallgrass prairie have a weak scientific rationale, are not consistent with plausible history, and threaten prairie biodiversity. Dormant-season burns and grazer exclusion are human interventions that may promote artificially consistent dominance of large grasses utilizing the C4 photosynthetic pathway, thereby relegating hundreds of other prairie plants to small populations that are vulnerable to local extinction. I recommend an experimental approach to large remnant conservation and restoration in which varied conditions alter dominance, thereby increasing short-term species richness. I also recommend prescribed burning during the summer, to simulate the timing of lightning fire, and light-to-moderate grazing by different ungulates, to simulate historical grazing history. Both should favor plants that are consistently infrequent or rare in many managed prairies. Varied regimes of burn season, burn interval, and large-mammal grazing should promote greater overall species diversity and should more realistically represent varied conditions under which grassland taxa evolved. 相似文献
53.
Henry R. Balikov 《环境质量管理》1998,8(2):29-34
This article will focus on how a systems approach can be used as a strategic tool for environmental improvement that makes sense from a perspective of bottom-line financial performance. The author will discuss some real-world experience concerning how electric utilities are attempting to align environmental management more closely with business management theory and practice. The ISO 14000 standards have been proposed and, in many instances, finalized as global voluntary standards. How important will they be to the U.S. electric utility sector? ISO 14001, the EMS standard, has been promoted as a necessary “certificate” for those who sell products and/or services overseas. In fact, to be of value to most organizations, the standard must show that it can make a positive financial contribution, whether the service or product is marketed globally, nationally, or locally. © 1998 John Wiley & Sons, Inc. 相似文献
54.
White CM Strazisar BR Granite EJ Hoffman JS Pennline HW;Air & Waste Management Association 《Journal of the Air & Waste Management Association (1995)》2003,53(6):645-715
The topic of global warming as a result of increased atmospheric CO2 concentration is arguably the most important environmental issue that the world faces today. It is a global problem that will need to be solved on a global level. The link between anthropogenic emissions of CO2 with increased atmospheric CO2 levels and, in turn, with increased global temperatures has been well established and accepted by the world. International organizations such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC) have been formed to address this issue. Three options are being explored to stabilize atmospheric levels of greenhouse gases (GHGs) and global temperatures without severely and negatively impacting standard of living: (1) increasing energy efficiency, (2) switching to less carbon-intensive sources of energy, and (3) carbon sequestration. To be successful, all three options must be used in concert. The third option is the subject of this review. Specifically, this review will cover the capture and geologic sequestration of CO2 generated from large point sources, namely fossil-fuel-fired power gasification plants. Sequestration of CO2 in geological formations is necessary to meet the President's Global Climate Change Initiative target of an 18% reduction in GHG intensity by 2012. Further, the best strategy to stabilize the atmospheric concentration of CO2 results from a multifaceted approach where sequestration of CO2 into geological formations is combined with increased efficiency in electric power generation and utilization, increased conservation, increased use of lower carbon-intensity fuels, and increased use of nuclear energy and renewables. This review covers the separation and capture of CO2 from both flue gas and fuel gas using wet scrubbing technologies, dry regenerable sorbents, membranes, cryogenics, pressure and temperature swing adsorption, and other advanced concepts. Existing commercial CO2 capture facilities at electric power-generating stations based on the use of monoethanolamine are described, as is the Rectisol process used by Dakota Gasification to separate and capture CO2 from a coal gasifier. Two technologies for storage of the captured CO2 are reviewed--sequestration in deep unmineable coalbeds with concomitant recovery of CH4 and sequestration in deep saline aquifers. Key issues for both of these techniques include estimating the potential storage capacity, the storage integrity, and the physical and chemical processes that are initiated by injecting CO2 underground. Recent studies using computer modeling as well as laboratory and field experimentation are presented here. In addition, several projects have been initiated in which CO2 is injected into a deep coal seam or saline aquifer. The current status of several such projects is discussed. Included is a commercial-scale project in which a million tons of CO2 are injected annually into an aquifer under the North Sea in Norway. The review makes the case that this can all be accomplished safely with off-the-shelf technologies. However, substantial research and development must be performed to reduce the cost, decrease the risks, and increase the safety of sequestration technologies. This review also includes discussion of possible problems related to deep injection of CO2. There are safety concerns that need to be addressed because of the possibilities of leakage to the surface and induced seismic activity. These issues are presented along with a case study of a similar incident in the past. It is clear that monitoring and verification of storage will be a crucial part of all geological sequestration practices so that such problems may be avoided. Available techniques include direct measurement of CO2 and CH4 surface soil fluxes, the use of chemical tracers, and underground 4-D seismic monitoring. Ten new hypotheses were formulated to describe what happens when CO2 is pumped into a coal seam. These hypotheses provide significant insight into the fundamental chemical, physical, and thermodynamic phenomena that occur during coal seam sequestration of CO2. 相似文献
55.
The phorid fly, Pseudacteon tricuspis Borgmeier, is an introduced parasitoid of imported fire ants, Solenopsis spp., in the USA. Although the assumption that phorid flies use fire ant alarm pheromones for host location is probably true,
we demonstrated in a previous study the possible involvement of other ant semiochemicals in the response of P. tricuspis to fire ants. This study was conducted to determine the glandular sources and identity of the semiochemicals mediating this
interaction. First, we tested the electroantennogram response of P. tricuspis to extracts of key body parts and glands of workers of the red imported fire ant, S. invicta Buren. The results confirm that the poison (venom) gland/sac is the key source of compounds which elicited strong antennal
activity in P. tricuspis. Follow-up studies were conducted by using a combination of bioassay-guided fractionation and behavioral bioassays to test
the hypothesis that attraction of this parasitoid to fire ants is mediated by venom alkaloids. The results confirm the response
of P. tricuspis to physiologically relevant amounts of the two venom alkaloid fractions (cis and trans alkaloid fractions) of S. invicta. Further analysis by coupled gas chromatography–electroantennogram detection revealed nine venom alkaloid components including
two novel 2,6-dialkylpiperideines that elicited significant antennal activity in P. tricuspis. This is the first demonstration of the role of venom alkaloids of ants as attractants for their natural enemies. We propose
a semiochemical-mediated host location mechanism for P. tricuspis involving both alarm pheromones and venom alkaloids. The ecological significance of these findings, including the attraction
of male P. tricuspis to fire ant venom alkaloids, possibly for mate location, is discussed. 相似文献
56.
57.
Encounter rate and task allocation in harvester ants 总被引:7,自引:0,他引:7
As conditions change, social insect colonies adjust the numbers of workers engaged in various tasks, such as foraging and
nest work. This process of task allocation operates without central control; individuals respond to simple, local cues. This
study investigates one such cue, the pattern of an ant's interactions with other workers. We examined how an ant's tendency
to perform midden work, carrying objects to and sorting the refuse pile of the colony, is related to the recent history of
the ant's brief antennal contacts, in laboratory colonies of the red harvester ant, Pogonomyrmex barbatus. The probability that an ant performed midden work was related to its recent interactions in two ways. First, the time an
ant spent performing midden work was positively correlated with the number of midden workers that ant had met while it was
away from the midden. Second, ants engaged in a task other than midden work were more likely to begin to do midden work when
their rate of encounter per minute with midden workers was high. Cues based on interaction rate may enable ants to respond
to changes in worker numbers even though ants cannot count or assess total numbers engaged in a task.
Received: 1 July 1998 / Accepted: 15 November 1998 相似文献
58.
Adeleye Bosede Ngozi Akam Darlington Inuwa Nasiru James Henry Tumba Basila Denis 《Environmental science and pollution research international》2023,30(13):36190-36207
Environmental Science and Pollution Research - The 2030 United Nations Sustainable Development Goal (SDG) 13 agenda hinges on attaining a sustainable environment with the need to “take urgent... 相似文献
59.
Natasha Stoudmann Lena M. Reibelt Aime G. Rakotomalala Olivier Randriamanjakahasina Claude A. Garcia Patrick O. Waeber 《Natural resources forum》2021,45(1):87-102
A growing number of people are entering the artisanal and small‐scale mining (ASM) sector worldwide. In Madagascar, millions of individuals depend on this informal activity. Through a case study in the Alaotra‐Mangoro region of Madagascar, our research aimed to understand the “bottom‐up” dynamics and ripple effects of the sector, by looking at the realities for rural communities where inhabitants are both directly and indirectly affected by ASM. We were interested in community members' and miners' perceptions of the socio‐economic and environmental impacts of ASM, and in identifying the factors attracting people living in one of the country's agricultural hubs to this activity. Our results show a wide diversity of push and pull factors leading people to enter the sector. Although many positive impacts of ASM exist for miners and communities within the vicinity of mines, most miner participants considered themselves worse off since starting to mine, highlighting the high risk and low probability of return of ASM. ASM's potential for local and national development will remain squandered if its negative impacts continue to go unmanaged. Accounting for local contexts and the ripple effects of ASM will be crucial in achieving safety and security for miners, and to tap into the benefits it may offer communities while minimising environmental damage. 相似文献