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41.
P. A. Hernandez I. Franke S. K. Herzog V. Pacheco L. Paniagua H. L. Quintana A. Soto J. J. Swenson C. Tovar T. H. Valqui J. Vargas B. E. Young 《Biodiversity and Conservation》2008,17(6):1353-1366
Conservationists are increasingly relying on distribution models to predict where species are likely to occur, especially
in poorly-surveyed but biodiverse areas. Modeling is challenging in these cases because locality data necessary for model
formation are often scarce and spatially imprecise. To identify methods best suited to modeling in these conditions, we compared
the success of three algorithms (Maxent, Mahalanobis Typicalities and Random Forests) at predicting distributions of eight
bird and eight mammal species endemic to the eastern slopes of the central Andes. We selected study species to have a range
of locality sample sizes representative of the data available for endemic species of this region and also that vary in their
distribution characteristics. We found that for species that are known from moderate numbers (N = 38–94) of localities, the three methods performed similarly for species with restricted distributions but Maxent and Random
Forests yielded better results for species with wider distributions. For species with small numbers of sample localities (N = 5–21), Maxent produced the most consistently successful results, followed by Random Forests and then Mahalanobis Typicalities.
Because evaluation statistics for models derived from few localities can be suspect due to the poor spatial representation
of the evaluation data, we corroborated these results with review by scientists familiar with the species in the field. Overall,
Maxent appears to be the most capable method for modeling distributions of Andean bird and mammal species because of the consistency
of results in varying conditions, although the other methods have strengths in certain situations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
42.
Time of germination and establishment success after fire of three obligate seeders in a Mediterranean shrubland of central Spain 总被引:3,自引:0,他引:3
José R. Quintana Alberto Cruz Federico Fernández-González José M. Moreno 《Journal of Biogeography》2004,31(2):241-249
Aim Determining how differences in time of germination can affect plant establishment in plant communities that, after a disturbance, must reestablish from seeds under climatic conditions subject to extremes, such as the Mediterranean. Although early germination may be beneficial for survival in summer, when drought is severe, this may expose the seedlings to winter extremes, thus to higher mortality. Understanding how sensitive is the establishment of different species to temporal patterns of germination will help to understand the factors that control species distribution and community stability in disturbance‐prone environments, as well as its sensitivity to changes in weather patterns as climate changes. Methods An experimental fire was made in early fall in an old Cistus–Erica shrubland in Toledo (central Spain). After fire, germination, survival and growth of the three dominant seeder species (Cistus ladanifer, Erica umbellata and Rosmarinus officinalis) were monitored during the first 3 years after fire. Seedlings were tagged to identify their time of emergence, and divided into cohorts according to their month of germination. Differences in survival of the various cohorts were evaluated by means of a Wilcoxon (Gehan) statistic. Height of surviving, tagged plants was compared among cohorts by means of a Kolmogorov–Smirnov test. Results The year following fire was one of the driest on record, while the next one was one of the wettest. Germination was more abundant during the first than during the second year. Establishment was mainly from first‐year germination, as the majority of second‐year germinated seedlings died. Temporal patterns of germination within a year and between years varied between species. Seedling mortality was highest immediately following germination, not in summer. Mortality was related to time of germination: during a given period of time, the mortality of younger seedlings was higher than that of older ones. However, survival was not highest for the first cohorts. In general, the earlier the seedlings germinated the more vigourous they became, more clearly so for Cistus than for Rosmarinus, but differences tended to disappear with time. Overall, time of germination varied between species and affected differently seedling survival and vigour of the various species. Rosmarinus and Cistus had sufficient survivors to reestablish the initial population. Erica, despite abundant germination, suffered a strong population reduction. Main conclusions Mediterranean shrub species differ in their temporal patterns of germination and survival after fire. The effect of time of germination is complex: germinating early is advantageous since old seedlings fared better than younger ones when confronted with the same rigours. However, germinating early might expose the seedlings to greater hazards and the first cohort might not survive best. The temporal window for establishment is narrow and mainly restricted to the first year after fire. Second year seedlings, irrespective of most favourable conditions, survived very little. Missing the window of establishment might virtually lead to a population collapse, despite having very high germination, as found for Erica. 相似文献
43.
Determination of selenium and iodine in human thyroids. 总被引:2,自引:0,他引:2
Miguel Murillo Nereida Carrión Mercedes Quintana Georgia Sanabria Manuel Ríos Leopoldo Duarte Franklin Ablan 《Journal of trace elements in medicine and biology》2005,19(1):23-27
This study focuses on the determination of selenium and iodine in human thyroids. The glands were digested using nitric acid in a microwave oven. Selenium was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using a new sample introduction system consisting of a reduction system coupled to a hydride generation nebulizer (DHGN). Iodine was determined by using the Sandell-Kolthoff procedure. The detections limits were 0.2 ng/mL and 0.3 ng/mL for the determination method of selenium and iodine, respectively. The amount of iodine in the whole gland was 3.44 +/- 1.11 microg/g. The lowest iodine level was 2.34 microg/g and the highest 5.21 microg/g. The lowest selenium concentration for a single sample was 505 +/- 51 ng/g and the highest 1495 +/- 204 ng/g depending on the fraction of the gland selected. 相似文献
44.
Leandro S. Silva Gustavo C. Prado Paula G. Quintana Norton Heise Kildare R. Miranda Eduardo J.L. Torres Pedro M. Persechini Ana Acacia de Sá Pinheiro Julieta Schachter 《Microbes and infection / Institut Pasteur》2018,20(3):205-211
Purine nucleotide synthesis in protozoa takes place exclusively via the purine salvage pathway and S-adenosyl-l-homocysteine hydrolase (SAHH) is an important enzyme in the Plasmodium salvage pathway which is not present in erythrocytes. Here, we describe the antimalarial effect of 2′3′-dialdehyde adenosine or oxidized adenosine (oADO), inhibitor of SAHH, on in vitro infection of human erythrocytes by P. falciparum. Treatment of infected erythrocytes with oADO inhibits parasite development and reinvasion of new cells. Erythrocytes pre-treated with oADO have a reduced susceptibility to invasion. Our results suggest that oADO interferes with one or more parasitic enzymes of the purine salvage pathway. 相似文献
45.
46.
Michael C. Ellis A. H. Hetisimer David A. Ruddy Sherry L. Hansen Gregory S. Kronmal Erin McClelland Leah Quintana D. T. Drayna Michael S. Aldrich E. Mignot 《Immunogenetics》1997,46(5):410-417
A systematic haplotype and sequencing analysis of the HLA-DR and -DQ region in patients with narcolepsy was performed. Five new (CA)n microsatellite markers were generated and positioned on the physical map across the HLA-DQB1-DQA1-DRB1 interval. Haplotypes for these new markers and the three HLA loci were established using somatic cell hybrids generated from patients. A four-marker haplotype surrounding the DQB1
*
0602 gene was found in all narcolepsy patients, and was identical to haplotypes observed on random chromosomes harboring the DQB1
*
0602 allele. Eighty-six kilobases of contiguous genomic sequence across the region did not reveal new genes, and analysis of this
sequence for single nucleotide polymorphisms did not reveal sequence variation among DQB1
*
0602 chromosomes. These results are consistent with other studies, suggesting that the HLA-DQ genes themselves are among the predisposing factors in narcolepsy.
Received: 18 March 1997 / Revised: 23 April 1997 相似文献
47.
A New Fulmarine Petrel (Aves: Procellariiformes) from the Upper Miocene of the Western Mediterranean
Bartomeu Seguí Josep Quintana Joan J. Fornós & Josep Antoni Alcover 《Palaeontology》2001,44(5):933-948
A new sea bird, Pterodromoides minoricensis gen. et sp. nov., similar in size and proportions to species of the modern genus Pterodroma , is described from Late Miocene breccias situated on the north-west coast of Menorca. The cranial osteology is similar to that of fulmarine petrels, but the large orbitonasal opening and characters of the postcranial skeleton justify its classification as a separate genus. At least one other species of procellariid occurs in the accompanying fossil asemblage, suggesting that Late Tertiary ecological conditions favoured sea bird populations in this area of the Mediterranean. 相似文献
48.
Hanna Tuomisto Kalle Ruokolainen Axel Dalberg Poulsen Robbin C. Moran Catalina Quintana Gstavo Cañas Jorge Celi 《Biotropica》2002,34(4):516-533
We documented the floristic composition of pteridophytes (ferns and fern allies) and Melastomataceae in Yasuní National Park, Amazonian Ecuador. Our main questions were: (1) Are the density of individuals, species richness, and/or species diversity (measured with Shannon's H′) of the two plant groups related to edaphic differences? and (2) How many of the pteridophyte and Melastomataceae species are non–randomly distributed in relation to a soil base content gradient within terra firme (non–inundated forest). To answer these questions, we sampled 27 line transects of 500 × 5 m distributed in an area of ca 20 × 25 km. The study area included a permanent 50 ha plot established to monitor forest dynamics; thus, our results also provide information on landscape–scale floristic variability to which results from within the plot can be compared. A total of 45,608 individuals and 140 species of pteridophytes, and 4893 individuals and 89 species of the Melastomataceae, were counted in the transects. Both with pteridophytes and with Melastomataceae, a clear negative correlation was found between the amount of extractable bases in the soil and the number of plant individuals encountered in a transect. With Melastomataceae, species richness and species diversity also were negatively correlated with soil base content, but with pteridophytes they were not. More than 50 percent of the common species of both pteridophytes and Melastomataceae were nonrandomly distributed along the soil cation content gradient within terra firme. We conclude that while the species richness patterns observed in one plant group are not indicative of similar patterns in other plant groups, it seems likely that a substantial (but unknown) proportion of species belonging to other plant groups will be found to show distribution patterns that reflect edaphic preferences within terra firme forests. 相似文献
49.
Epigenetic control of early neurodegenerative events in diabetic retinopathy by the histone deacetylase SIRT6
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Ada Yeste Francisco J. Quintana Debra Toiber Raul Mostoslavsky Dafne M. Silberman 《Journal of neurochemistry》2018,144(2):128-138
50.
Size‐based interactions and trophic transfer efficiency are modified by fish predation and cyanobacteria blooms in Lake Mývatn,Iceland
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Zeynep Ersoy Erik Jeppesen Serena Sgarzi Ignasi Arranz Miguel Cañedo‐Argüelles Xavier D. Quintana Frank Landkildehus Torben L. Lauridsen Mireia Bartrons Sandra Brucet 《Freshwater Biology》2017,62(11):1942-1952