全文获取类型
收费全文 | 1038篇 |
免费 | 82篇 |
国内免费 | 30篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 28篇 |
2020年 | 27篇 |
2019年 | 22篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 26篇 |
2015年 | 37篇 |
2014年 | 27篇 |
2013年 | 59篇 |
2012年 | 26篇 |
2011年 | 32篇 |
2010年 | 17篇 |
2009年 | 60篇 |
2008年 | 76篇 |
2007年 | 73篇 |
2006年 | 51篇 |
2005年 | 44篇 |
2004年 | 28篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 38篇 |
2000年 | 30篇 |
1999年 | 28篇 |
1998年 | 30篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 22篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1150条查询结果,搜索用时 31 毫秒
991.
992.
Clemente Capasso Vincenzo Carginale Marilisa Riggio Rosaria Scudiero Piero Andrea Temussi Francesca Trinchella Elio Parisi 《Reviews in Environmental Science and Biotechnology》2006,5(2-3):253-267
Organisms from yeast to mammals contain cysteine-rich, heavy metal binding proteins termed metallothioneins. The putative roles of these proteins are trace metal homeostasis and detoxification of poisonous heavy metals. The highly conserved chemical composition and the structural constraints led to the conclusion that metallothioneins of different origin must display remarkably similar features. The present review aims at surveying the studies carried out on the metallothioneins of Antarctic Notothenioidei, a dominating fish group endowed of a number of striking adaptive characters, including reduced (or absent) hematocrit and presence of antifreeze glycoproteins. Given the unique peculiarities of the Antarctic environment, a comparative study of the features of notothenioid metallothioneins could provide new insights into the role of these proteins in physiology and toxicology. The results summarized here show that the metallothioneins of this fish group display a number of features at the level of evolution, expression pattern, structure and function remarkably different from those of mammal metallothioneins. 相似文献
993.
Guido di Prisco Cinzia Verde 《Reviews in Environmental Science and Biotechnology》2006,5(2-3):309-321
The recognition of the important role of the polar habitats in global climate changes has awakened great interest in the evolutionary biology of the organisms that live there, as well as the increasing threat of loss of biological diversity and depletion of marine fisheries. These organisms are exposed to strong environmental constraints, and it is important to understand how they have adapted to cope with these challenges and to what extent adaptations may be upset by current climate changes. Adaptations of the dominant group of Antarctic fish, the suborder Notothenioidei, have been thoroughly investigated by several teams. Considering the amount of information available on cold adaptation, the study of fish adapted to the extreme conditions of the polar seas will allow us to gain invaluable clues on the development, impact and consequences of climate and anthropogenic challenges, with powerful implications for the future of the Earth. 相似文献
994.
Klaus Martin Meiners S. Papadimitriou D. N. Thomas L. Norman G. S. Dieckmann 《Polar Biology》2009,32(7):1055-1065
Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western
Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range
−7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg−1) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg−1), dissolved inorganic phosphate (range 0.2–7.0 μmol kg−1) and silicic acid (range 74–285 μmol kg−1) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH4
+ (range 0.3–23.0 μmol kg−1) and dissolved organic carbon (range 140–707 μmol kg−1) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high
algal biomass (4.9–435.5 μg Chl a l−1 brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic
parameters F
v/F
m, α, rETRmax and E
k. The maximum quantum yield of photosystem II, F
v/F
m, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and
bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in
the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic
parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine
channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques. 相似文献
995.
The diet of the Weddell seal Leptonychotes weddellii at the South Orkney Islands was investigated by the analysis of 44 and 26 faecal samples collected from the beaches of Laurie
Island from May 1999 to January 2000 and from October to December 2001, respectively. The diet was diverse and both pelagic
and benthic-demersal organisms were represented in the samples. Fish were the most frequent prey of the samples in both seasons,
and fish and krill were the most numerous prey items. Octopods predominated by mass in 1999, whereas krill constituted the
bulk of the diet in 2001, a fact that was not observed previously. Among fish, Gobionotothen gibberifrons was largely the species that contributed mostly to the diet, whereas pelagic fish could not be identified in the samples.
The results are compared with information from other study areas and discussed in relation to the consumption of krill. 相似文献
996.
Jesús Matallanas 《Polar Biology》2009,32(1):15-19
A new genus and species of zoarcid fish, Gosztonyia antarctica, is described on the basis of four specimens collected from the Bellingshausen Sea, Antarctic Ocean, at a depth of 615 m.
Gosztonyia is placed in the subfamily Lycodinae and can be distinguished from all other zoarcid genera by the following combination
of characters: seven branchiostegal rays, interdigitating ceratohyal–epihyal articulation, palatal arch reduced, posterior
hyomandibular ramus longer than anterior, cranium narrowed, supratemporal commisure and occipital pores absent. A new species,
Gosztonyia antarctica, is described and the relationships of the new genus are discussed. 相似文献
997.
Antarctic birds are not beyond the effects of parasites or pathogens. However, potential ecological consequences of wide-spread
infections for bird populations in Antarctica have received little attention. In this paper, we review the information published
about disease and parasites, and their effects on Antarctic birds. The information on host species, parasites and pathogens,
and geographic regions is incomplete and data on ecological effects on the populations, including how birds respond to pathogens
and parasites, are almost inexistent. We conclude that more research is needed to establish general patterns of spatial and
temporal variation in pathogens and parasites, and to determine how such patterns could influence hosts. This information
is crucial to limit the spread of outbreaks and may aid in the decision-making process should they occur. 相似文献
998.
Azwianewi B. Makhado Mike A. Meÿer Robert J. M. Crawford Les G. Underhill Chris Wilke 《African Journal of Ecology》2009,47(3):335-340
In the 2006/2007 breeding season of Cape gannets Morus capensis at Malgas Island, the removal of 61 Cape fur seals Arctocephalus pusillus pusillus that preyed on gannet fledglings when they left to sea significantly reduced the mortality rate of these fledglings. However, because seals learned to avoid the boat used for their removal, it was not possible to remove all the seals that killed gannet fledglings and some mortality continued. The seals inflicting the mortality were all sub-adult males, with an average age of <5 years. Sustained removal of these animals may reduce this feeding behaviour, which is at present having an adverse impact on several threatened seabirds in the Benguela ecosystem. 相似文献
999.
Susi M. C. Edrén Signe M. Andersen Jonas Teilmann Jacob Carstensen Pernille B. Harders Rune Dietz Lee A. Miller 《Marine Mammal Science》2010,26(3):614-634
This study investigates the effects of the construction and operation of a large Danish offshore wind farm on harbor and gray seal haul-out behavior within a nearby (4 km) seal sanctuary. Time-lapse photography, visual monitoring, and aerial surveys were used to monitor the number of seals on land in daylight hours. Seals were monitored during two preconstruction periods (19 June–31 August 2001 and April–August 2002), a construction period of the wind farm (August 2002–December 2003), and a period of operation of the wind farm (December 2003–December 2004). Monthly aerial surveys were conducted to estimate the proportion of seals in the sanctuary relative to neighboring haul-out sites. From preconstruction to construction and through the first year of operation the number of harbor seals in the sanctuary increased at the same rate as the number of seals at the neighboring haul-out sites. No long-term effects on haul-out behavior were found due to construction and operation of the wind farm. However, a significant short-term decrease was seen in the number of seals present on land during sheet pile driving in or near the wind farm. Acoustic deterrents were utilized simultaneously to avoid hearing damage. 相似文献
1000.
John A.E. Gibson Russell C. Garrick Harry R. Burton Andrew R. McTaggart 《Geomicrobiology journal》2013,30(3-4):179-184
Dimethylsulfide (DMS) concentrations in seawater collected on a regular basis from May 1987 until February 1988 at a site 10 km offshore from Australia's Davis antarctic research station (68°35’ S, 77°52’ E) were measured and found, during a bloom of the unicellular alga Phaeocystis pouchetii, to be higher (up to 290 nM) than any previously reported for the ocean. A correlation was found between DMS levels and cell numbers of P. pouchetii. The amount of DMS present in the water samples per cell of the alga in this study was found to be significantly higher than recorded in two studies in the Northern Hemisphere. The seawater concentrations of dimethylsulfoniopropionate (DMSP), the biological precursor of DMS, was also measured and was found to be present for most of the year at levels above that of DMS. The results suggest that it is possible that the antarctic region contributes significantly to the atmospheric sulfur budget. 相似文献