全文获取类型
收费全文 | 125篇 |
免费 | 4篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 9篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1895年 | 2篇 |
排序方式: 共有129条查询结果,搜索用时 31 毫秒
81.
Piero Calosi Samuel P. S. Rastrick Chiara Lombardi Heidi J. de Guzman Laura Davidson Marlene Jahnke Adriana Giangrande J?rg D. Hardege Anja Schulze John I. Spicer Maria-Cristina Gambi 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2013,368(1627)
Metabolic rate determines the physiological and life-history performances of ectotherms. Thus, the extent to which such rates are sensitive and plastic to environmental perturbation is central to an organism''s ability to function in a changing environment. Little is known of long-term metabolic plasticity and potential for metabolic adaptation in marine ectotherms exposed to elevated pCO2. Consequently, we carried out a series of in situ transplant experiments using a number of tolerant and sensitive polychaete species living around a natural CO2 vent system. Here, we show that a marine metazoan (i.e. Platynereis dumerilii) was able to adapt to chronic and elevated levels of pCO2. The vent population of P. dumerilii was physiologically and genetically different from nearby populations that experience low pCO2, as well as smaller in body size. By contrast, different populations of Amphiglena mediterranea showed marked physiological plasticity indicating that adaptation or acclimatization are both viable strategies for the successful colonization of elevated pCO2 environments. In addition, sensitive species showed either a reduced or increased metabolism when exposed acutely to elevated pCO2. Our findings may help explain, from a metabolic perspective, the occurrence of past mass extinction, as well as shed light on alternative pathways of resilience in species facing ongoing ocean acidification. 相似文献
82.
Vitaly V. Vostrikov Kaustubh R. Mote Raffaello Verardi Gianluigi Veglia 《Structure (London, England : 1993)》2013,21(12):2119-2130
- Download : Download high-res image (341KB)
- Download : Download full-size image
83.
This study enlarge the knowledge on species composition, distribution and community structure of pelagic polychaetes on the basis of finely stratified spatial sampling representing austral summer conditions in the Strait of Magellan. Zooplankton samples were collected in late austral summer 1995. A total of 56,489 pelagic polychaete specimens were collected. Eight holopelagic polychaete taxa were recorded in addition to Spionidae and Terebellidae larvae and reproductive stolons of Autolytinae. Pelagobia longicirrata (Lopadorhynchidae) was the most abundant species, representing about 96 % (54,092 specimens, 184.6 ind. 100 m?3) of all individuals, followed by Tomopteris planktonis (Tomopteridae) at 3 % (1,725 specimens, 5.9 ind. 100 m?3). The longest measured individuals belonged to T. planktonis, which also showed the largest size range, whereas the smallest individuals belonged to P. longicirrata. Spatial distribution of polychaetes in terms of abundance was not related to bottom depth, but rather the number of taxa was lower in the central part of the Strait. P. longicirrata and T. planktonis were negatively related to chlorophyll a. In addition, the first was negatively related to temperature instead the second was positively affected by salinity. Polychaetes were widely distributed in both epi- and mesopelagic realms, whereas they were almost absent above 80 m depth. Both of the most abundant species were concentrated in the deepest layers sampled (below 100 m) throughout day and night hours without showing any specific migratory behavior. 相似文献
84.
85.
Progressive decrease of heart period variability entropy-based complexity during graded head-up tilt. 总被引:1,自引:0,他引:1
Alberto Porta Tomaso Gnecchi-Ruscone Eleonora Tobaldini Stefano Guzzetti Raffaello Furlan Nicola Montano 《Journal of applied physiology》2007,103(4):1143-1149
Complexity (or its opposite, regularity) of heart period variability has been related to age and disease but never linked to a progressive shift of the sympathovagal balance. We compare several well established estimates of complexity of heart period variability based on entropy rates [i.e., approximate entropy (ApEn), sample entropy (SampEn), and correct conditional entropy (CCE)] during an experimental protocol known to produce a gradual shift of the sympathovagal balance toward sympathetic activation and vagal withdrawal (i.e., the graded head-up tilt test). Complexity analysis was carried out in 17 healthy subjects over short heart period variability series ( approximately 250 cardiac beats) derived from ECG recordings during head-up tilt with table inclination randomly chosen inside the set {0, 15, 30, 45, 60, 75, 90}. We found that 1) ApEn does not change significantly during the protocol; 2) all indices measuring complexity based on entropy rates, including ad hoc corrections of the bias arising from their evaluation over short data sequences (i.e., corrected ApEn, SampEn, CCE), evidence a progressive decrease of complexity as a function of the tilt table inclination, thus indicating that complexity is under control of the autonomic nervous system; 3) corrected ApEn, SampEn, and CCE provide global indices that can be helpful to monitor sympathovagal balance. 相似文献
86.
The basin off the Bellingshausen Sea, in contrast to other better known areas such as the Antarctic Peninsula and the Ross
and Weddell Seas, has been little investigated due to remoteness and the prevalence of ice for most of the year. The present
study focuses on an analysis of polychaetes collected from soft bottoms of this sea and off the west coast of the Antarctic
Peninsula (Gerlache Strait) by means of a box-corer (25 × 25 cm) in two intensive surveys carried out during austral summers
of 2002–2003 and 2005–2006 (BENTART-03 and BENTART-06). Three different polychaete assemblages were determined from the classification
and ordination analyses of sampling stations based on the Bray-Curtis similarity index. One group of stations encompassed
the deep stations from the shelf of the Bellingshausen Sea, the second one the shallower stations from the same area and the
third one those stations located near the coast of Peter I Island and Gerlache Strait, off the Antarctic Peninsula. The environmental
variables involved in segregating these groups were several sedimentary features (redox potential, gravel content) and depth.
The present study provides further support to previous ones that considered the shelf of the Bellingshausen Sea as a differentiated
region within the Southern Ocean, clearly distinct to the adjacent Weddell and Scott Seas and the Antarctic Peninsula. 相似文献
87.
Lei Shi Nathaniel J. Traaseth Raffaello Verardi Alessandro Cembran Jiali Gao Gianluigi Veglia 《Journal of biomolecular NMR》2009,44(4):195-205
To fully describe the fold space and ultimately the biological function of membrane proteins, it is necessary to determine
the specific interactions of the protein with the membrane. This property of membrane proteins that we refer to as structural topology cannot be resolved using X-ray crystallography or solution NMR alone. In this article, we incorporate into XPLOR-NIH a hybrid
objective function for membrane protein structure determination that utilizes solution and solid-state NMR restraints, simultaneously
defining structure, topology, and depth of insertion. Distance and angular restraints obtained from solution NMR of membrane
proteins solubilized in detergent micelles are combined with backbone orientational restraints (chemical shift anisotropy
and dipolar couplings) derived from solid-state NMR in aligned lipid bilayers. In addition, a supplementary knowledge-based
potential, E
z (insertion depth potential), is used to ensure the correct positioning of secondary structural elements with respect to a
virtual membrane. The hybrid objective function is minimized using a simulated annealing protocol implemented into XPLOR-NIH software
for general use.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
88.
Cristina Gambi Silvia Bianchelli Marta Pérez Olga Invers Joan Manuel Ruiz Roberto Danovaro 《Biodiversity and Conservation》2009,18(1):33-54
The effects of induced hypoxic-anoxic conditions on the metazoan meiofaunal assemblages and nematode diversity were investigated
with an in situ experiment in a Posidonia oceanica meadow. The experiment, of the duration of five months, was performed in three experimental sets of plots. Two of them were
enriched with organic matter to induce anoxic conditions (1 set with sucrose and 1 set with sugar plus nutrients, i.e. nitrogen
and phosphorus) whereas the last set of plots was kept undisturbed and used as Control. Metazoan meiofauna displayed a fast
response to the induced anoxic conditions with an immediate reduction of the richness of taxa (only nematodes and copepods
tolerated the hypoxic-anoxic conditions). Nematodes were the most tolerant organisms as their species richness did not change
in hypoxic-anoxic conditions, but their species composition and trophic structure displayed significant changes. Some genera
(Desmoscolex and Bolbolaimus) were replaced by other (Chromadorella, Sabatiera and Polysigma) more tolerant to the extreme conditions. No significant differences were observed in the Control plots, whereas in treated
plots, selective deposit feeders and predators decreased significantly, being replaced by non-selective deposit feeders and
epistrate feeders. These results indicate that, events causing a reduction in oxygen availability, can have an impact on the
nematode beta-diversity and functional diversity with potential important implications on the benthic food web and functioning
of the seagrass systems. 相似文献
89.
Insight into trade-off between wood decay and parasitism from the genome of a fungal forest pathogen
Olson A Aerts A Asiegbu F Belbahri L Bouzid O Broberg A Canbäck B Coutinho PM Cullen D Dalman K Deflorio G van Diepen LT Dunand C Duplessis S Durling M Gonthier P Grimwood J Fossdal CG Hansson D Henrissat B Hietala A Himmelstrand K Hoffmeister D Högberg N James TY Karlsson M Kohler A Kües U Lee YH Lin YC Lind M Lindquist E Lombard V Lucas S Lundén K Morin E Murat C Park J Raffaello T Rouzé P Salamov A Schmutz J Solheim H Ståhlberg J Vélëz H de Vries RP Wiebenga A Woodward S Yakovlev I 《The New phytologist》2012,194(4):1001-1013
90.
Leonardi S Piovani P Scalfi M Piotti A Giannini R Menozzi P 《The Journal of heredity》2012,103(3):408-417
Fragmentation can affect the demographic and genetic structure of populations near the boundary of their biogeographic range. Higher genetic differentiation among populations coupled with lower level of within-population variability is expected as a consequence of reduced population size and isolation. The effects of these 2 factors have been rarely disentangled. Given their high gene flow, anemophilous forest trees should be more affected, in terms of loss of genetic diversity, by small population size rather than geographic isolation alone. We studied the impact of distance from the main range (a measure of isolation) and reduced population size on the within-population and among population components of genetic variability. We assayed 11 isozyme loci in a total of 856 individuals in 27 marginal populations of European beech (Fagus sylvatica L.) in Central Italy. Populations were divided into 3 groups with an increasing level of fragmentation. In the most fragmented group, the within-population genetic variability was slightly smaller and the among population differentiation significantly larger than in the other 2 groups. Isolation-by-distance was lost when only pairs of populations involving at least one from the most fragmented group were considered and maintained in the other groups. These results support the role of random genetic drift having a larger impact on the most fragmented group, whereas gene flow seems to balance genetic drift in the 2 less fragmented ones. Given that average distance from the main range is not different between the intermediate and the most fragmented group, but average population size is smaller, we can conclude that gene flow is effective, even at relatively long distances, in balancing the effect of fragmentation if population size is not too small. 相似文献