全文获取类型
收费全文 | 139篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 11篇 |
地球物理 | 33篇 |
地质学 | 44篇 |
海洋学 | 15篇 |
天文学 | 27篇 |
综合类 | 3篇 |
自然地理 | 21篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 12篇 |
2011年 | 13篇 |
2010年 | 7篇 |
2009年 | 12篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有157条查询结果,搜索用时 15 毫秒
31.
Macrobenthic infaunal communities associated with deep‐sea hydrocarbon seeps in the northern Gulf of Mexico 下载免费PDF全文
There are thousands of seeps in the deep ocean worldwide; however, many questions remain about their contributions to global biodiversity and the surrounding deep‐sea environment. In addition to being globally distributed, seeps provide several benefits to humans such as unique habitats, organisms with novel genes, and carbon regulation. The purpose of this study is to determine whether there are unique seep macrobenthic assemblages, by comparing seep and nonseep environments, different seep habitats, and seeps at different depths and locations. Infaunal community composition, diversity, and abundance were examined between seep and nonseep background environments and among three seep habitats (i.e., microbial mats, tubeworms, and soft‐bottom seeps). Abundances were higher at seep sites compared to background areas. Abundance and diversity also differed among microbial mat, tubeworm, and soft‐bottom seep habitats. Although seeps contained different macrobenthic assemblages than nonseep areas, infaunal communities were also generally unique for each seep. Variability was 75% greater within communities near seeps compared to communities in background areas. Thus, high variability in community structure characterized seep communities rather than specific taxa. The lack of similarity among seep sites supports the idea that there are no specific infauna that can be used as indicators of seepage throughout the northern Gulf of Mexico, at least at higher taxonomic levels. 相似文献
32.
Brian N. Tissot Barbara A. Best Eric H. Borneman Andrew W. Bruckner Cara H. Cooper Heather D’Agnes Timothy P. Fitzgerald Amanda Leland Susan Lieberman Amy Mathews Amos Rashid Sumaila Teresa M. Telecky Frazer McGilvray Brian J. Plankis Andrew L. Rhyne Glynnis G. Roberts Benjamin Starkhouse Todd C. Stevenson 《Marine Policy》2010
As the world’s largest importer of marine ornamental species for the aquaria, curio, home décor, and jewelry industries, the United States has an opportunity to leverage its considerable market power to promote more sustainable trade and reduce the effects of ornamental trade stress on coral reefs worldwide. Evidence indicates that collection of some coral reef animals for these trades has caused virtual elimination of local populations, major changes in age structure, and promotion of collection practices that destroy reef habitats. Management and enforcement of collection activities in major source countries such as Indonesia and the Philippines remain weak. Strengthening US trade laws and enforcement capabilities combined with increasing consumer and industry demand for responsible conservation can create strong incentives for improving management in source countries. This is particularly important in light of the March 2010 failure of the parties to the Convention on International Trade in Endangered Species (CITES) to take action on key groups of corals. 相似文献
33.
Stakeholder consultation is being adopted as standard practice in the planning and management of natural resource management programs. While the utility of stakeholder participation has been investigated for the evaluation and implementation phases of natural resource management programs, few studies have examined the utility of stakeholder consultation during the initial phases of developing such programs. This paper presents a case study from a project developing a marine and coastal monitoring program for the Pilbara and Kimberley region of northern Western Australia. Via a series of workshops held in the region, stakeholders were asked to prioritise future research needs using several voting procedures. During the analyses of the results from the different voting procedures, it became apparent that there were high levels of inconsistency, poor correlation, and contradiction, between participants’ responses. Despite the rigour of the selection process used to identify ‘suitable’ stakeholders for the workshops, these results show that stakeholders did not have the technical or broader contextual knowledge about marine ecosystems to effectively and objectively contribute to the research prioritisation and planning process. Based on the outcomes of this study, we argue that project designers need to be clear about why they are involving stakeholders in a project, particularly in light of the costs involved (financial, time, resources, costs to the stakeholder) in stakeholder consultation. Stakeholder involvement may be appropriate in later stages of developing natural resource management programs (implementation and management), however, stakeholder involvement is not appropriate in the initial phases of such programs, where scientific expertise is essential in formulating scientific concepts and frameworks. 相似文献
34.
Systematic marine conservation planning in data-poor regions: Socioeconomic data is essential 总被引:1,自引:0,他引:1
Natalie C. Ban Gretchen J.A. Hansen Michael Jones Amanda C.J. Vincent 《Marine Policy》2009,33(5):794-800
Systematic planning for conservation is highly regarded but relies on spatially explicit data that are lacking in many areas of conservation concern. The decision support tool Marxan is applied to a reef system in the central Philippines where 30 marine protected areas (MPAs) have been established in communities without much use of biophysical data. The intent was to explore how Marxan might assist with the legally required expansion to protect 15% of marine waters, and how existing MPAs might affect that process. Results show that biophysical information alone did not provide much guidance in identifying patterns of conservation importance in areas where the data are poor. Socioeconomic data were needed to distinguish among possible areas for protection; but here, as elsewhere in marine environments, the availability of such data was very limited. In the final analysis, local knowledge and integrated understanding of socioeconomic realities may offer the best spatially explicit information. The 30 existing MPAs, which encompassed a small proportion of the reef system, did not limit future options in developing a suite of MPAs on a broader scale. Rather, they appeared to generate the support for MPAs that is obligatory for any larger zoning effort. In summary, establishing MPAs based on community-driven criteria has biological and social value, but efforts should be made to collect ecological and socioeconomic data to guide the continued creation of MPAs. 相似文献
35.
36.
The designation of Texas as a “hotspot” for fish mortalities relative to the other 22 coastal US states is of serious concern
for scientists, resource managers, and the public alike. We investigated the major sources and causes of fish kills in coastal
Texas from 1951 to 2006. During this 55-year period, more than 383 million fish were killed, 72% of which were Gulf menhaden
(Brevoortia spp.). We examined the relationships between climate and the physical features of Texas bays and estuaries as well as the consequences
of high-density industrialization and urbanization along several coastal centers on fish kills, including the impact of eutrophication,
algal blooms (toxic and nontoxic), and hypoxia. Galveston and Matagorda Bays had the highest number of fish kill events and
total number of fish killed. The largest number of fish kill events and the highest number of fish killed occurred during
the warmest months, particularly in August. The leading cause of fish kills was found to be low dissolved oxygen concentrations
caused by both physical and biological factors. From 1958 to 1997, about two thirds of the mortalities from low oxygen concentrations
were caused by human activities. With the population predicted to double in Texas by 2050, mostly along the coastal areas,
natural resources will require additional protection. Further increases in nutrient loading are expected in areas unable to
keep up with construction of sewage treatment facilities. Defining the sources and causes of fish kill events in Texas will
allow better management and conservation efforts. 相似文献
37.
Amanda W. J. Demopoulos Nicole Cormier Katherine C. Ewel Brian Fry 《Estuaries and Coasts》2008,31(2):371-381
The mangrove or mud crab, Scylla serrata, is an important component of mangrove fisheries throughout the Indo-Pacific. Understanding crab diets and habitat use should
assist in managing these fisheries and could provide additional justification for conservation of the mangrove ecosystem itself.
We used multiple chemical tracers to test whether crab movements were restricted to local mangrove forests, or extended to
include adjacent seagrass beds and reef flats. We sampled three mangrove forests on the island of Kosrae in the Federated
States of Micronesia at Lelu Harbor, Okat River, and Utwe tidal channel. Samples of S. serrata and likely food sources were analyzed for stable carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) isotopes. Scylla serrata tissues also were analyzed for phosphorus (P), cations (K, Ca, Mg, Na), and trace elements (Mn, Fe, Cu, Zn, and B). Discriminant
analysis indicated that at least 87% of the crabs remain in each site as distinct populations. Crab stable isotope values
indicated potential differences in habitat use within estuaries. Values for δ13C and δ34S in crabs from Okat and Utwe were low and similar to values expected from animals feeding within mangrove forests, e.g.,
feeding on infauna that had average δ13C values near −26.5‰. In contrast, crabs from Lelu had higher δ13C and δ34S values, with average values of −21.8 and 7.8‰, respectively. These higher isotope values are consistent with increased crab
foraging on reef flats and seagrasses. Given that S. serrata have been observed feeding on adjacent reef and seagrass environments on Kosrae, it is likely that they move in and out of
the mangroves for feeding. Isotope mixing model results support these conclusions, with the greatest mangrove ecosystem contribution
to S. serrata diet occurring in the largest mangrove forests. Conserving larger island mangrove forests (> 1 km deep) appears to support
crab foraging activities. 相似文献
38.
Amanda R. Lusas Brenda L. Hall Thomas V. Lowell Meredith A. Kelly Ole Bennike Laura B. Levy William Honsaker 《Journal of Paleolimnology》2017,57(4):321-341
Prediction of future Arctic climate and environmental changes, as well as associated ice-sheet behavior, requires placing present-day warming and reduced ice extent into a long-term context. Here we present a record of Holocene climate and glacier fluctuations inferred from the paleolimnology of small lakes near Istorvet ice cap in East Greenland. Calibrated radiocarbon dates of organic remains indicate deglaciation of the region before ~10,500 years BP, after which time the ice cap receded rapidly to a position similar to or less extensive than present, and lake sediments shifted from glacio-lacustrine clay to relatively organic-rich gyttja. The lack of glacio-lacustrine sediments throughout most of the record suggests that the ice cap was similar to or smaller than present throughout most of the Holocene. This restricted ice extent suggests that climate was similar to or warmer than present, in keeping with other records from Greenland that indicate a warm early and middle Holocene. Middle Holocene magnetic susceptibility oscillations, with a ~200-year frequency in one of the lakes, may relate to solar influence on local catchment processes. Following thousands of years of restricted extent, Istorvet ice cap advanced to within 365 m of its late Holocene limit at ~AD 1150. Variability in the timing of glacial and climate fluctuations, as well as of sediment organic content changes among East Greenland lacustrine records, may be a consequence of local factors, such as elevation, continentality, water depth, turbidity, and seabirds, and highlights the need for a detailed spatial array of datasets to address questions about Holocene climate change. 相似文献
39.
DNA-based methods in paleolimnology: new opportunities for investigating long-term dynamics of lacustrine biodiversity 总被引:1,自引:0,他引:1
Isabelle Domaizon Amanda Winegardner Eric Capo Joanna Gauthier Irene Gregory-Eaves 《Journal of Paleolimnology》2017,57(1):1-18
We reconstructed 150 years of ecological change in a shallow boreal lake located on the east shore of the Baltic Sea by integrating different types of environmental evidence: paleolimnological records (XRF-measured elements, fossil pigments and Cladocera assemblages), information from historical limnological surveys and archival maps. We assessed the role of biomanipulation by liming and fish-removal in the disappearance of submerged macrophytes, such as Lobelia dortmanna L., and their replacement by persistent cyanobacterial blooms. The combination of different strands of evidence revealed that the shift from macrophyte to cyanobacterial dominance was part of a long-term ecological response to eutrophication and increased sediment load from catchment disturbances. The findings demonstrate that a gradual loss of wetlands and increase of ditches in a catchment had a more significant effect on the lake ecosystem, compared to the direct, but short-term impact of biomanipulation. The study highlights the importance of catchment land-use and disturbance by ditches in changing the ecology of boreal water bodies. Also, it illustrates that a thorough understanding of the long-term ecosystem dynamics and differentiation among responses to multiple anthropogenic impacts are essential preconditions for addressing the deterioration of habitats and change in aquatic environments. 相似文献
40.
Both statistical and dynamical downscaling methods are well established techniques to bridge the gap between the coarse information produced by global circulation models and the regional-to-local scales required by the climate change Impacts, Adaptation, and Vulnerability (IAV) communities. A number of studies have analyzed the relative merits of each technique by inter-comparing their performance in reproducing the observed climate, as given by a number of climatic indices (e.g. mean values, percentiles, spells). However, in this paper we stress that fair comparisons should be based on indices that are not affected by the calibration towards the observed climate used for some of the methods. We focus on precipitation (over continental Spain) and consider the output of eight Regional Climate Models (RCMs) from the EURO-CORDEX initiative at 0.44° resolution and five Statistical Downscaling Methods (SDMs) —analog resampling, weather typing and generalized linear models— trained using the Spain044 observational gridded dataset on exactly the same RCM grid. The performance of these models is inter-compared in terms of several standard indices —mean precipitation, 90th percentile on wet days, maximum precipitation amount and maximum number of consecutive dry days— taking into account the parameters involved in the SDM training phase. It is shown, that not only the directly affected indices should be carefully analyzed, but also those indirectly influenced (e.g. percentile-based indices for precipitation) which are more difficult to identify. We also analyze how simple transformations (e.g. linear scaling) could be applied to the outputs of the uncalibrated methods in order to put SDMs and RCMs on equal footing, and thus perform a fairer comparison. 相似文献