全文获取类型
收费全文 | 904篇 |
免费 | 60篇 |
出版年
2023年 | 7篇 |
2022年 | 15篇 |
2021年 | 33篇 |
2020年 | 19篇 |
2019年 | 31篇 |
2018年 | 27篇 |
2017年 | 31篇 |
2016年 | 39篇 |
2015年 | 61篇 |
2014年 | 67篇 |
2013年 | 61篇 |
2012年 | 66篇 |
2011年 | 80篇 |
2010年 | 37篇 |
2009年 | 47篇 |
2008年 | 37篇 |
2007年 | 35篇 |
2006年 | 41篇 |
2005年 | 45篇 |
2004年 | 24篇 |
2003年 | 30篇 |
2002年 | 22篇 |
2001年 | 9篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1956年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有964条查询结果,搜索用时 15 毫秒
41.
Ana Pires Ni-Bin Chang Graça Martinho 《The International Journal of Life Cycle Assessment》2011,16(4):316-337
Background, aim, and scope
This paper presents a study related to the application of the reliability-based life cycle assessment (LCA) to assess different alternatives for solid waste management in the Setúbal peninsula, Portugal. The current system includes waste collection, transport, sorting, recycling, and mechanical and biological treatment (MBT) by means of aerobic treatment and landfill. In addition, some future expansion plans are discussed. 相似文献42.
Oscar Godoy José Pires de Lemos-FilhoFernando Valladares 《Environmental and Experimental Botany》2011,71(2):207-214
Thermal tolerance of Photosystem II (PSII) highly influences plant distribution worldwide because it allows for photosynthesis during periods of high temperatures and water stress, which are common in most terrestrial ecosystems and particularly in dry and semi-arid ones. However, there is a lack of information about how this tolerance influences invasiveness of exotic species in ecosystems with seasonal drought. To address this question for Mediterranean-type ecosystems (MTE) of the Iberian Peninsula, we carried out an experiment with fifteen phylogenetically related species (8 invasive and 7 native, Pinus pinaster Ait., Pinus radiata D. Don, Schinus molle Linn., Elaeagnus angustifolia L., Eucalyptus globulus Labill., Acacia melanoxylon R. Br., Gleditsia triacanthos L., Pistacia terebinthus L., Rhamnus alaternus L., Anagyris foetida L., Colutea arborescens L., Oenothera biennis L., Epilobium hirsutum L., Achillea filipendulina Lam. and Achillea millefolium L). Seedlings were grown and maximal photochemical efficiency of PSII (Fv/Fm) was measured at two water availabilities (well-watered and with water stress). PSII thermal tolerance measurements were related to specific leaf area (SLA), which varied significantly across the study species, and to the mean potential evapotranspiration (PET) of the month with the lowest precipitation in the native areas of both groups and in the invaded area of the Iberian Peninsula. Additionally, PSII thermal tolerance measurements under water stress were phylogenetically explored. Invasive and native species neither differed in SLA nor in their thermal tolerance under well-watered conditions. For well-watered plants, SLA was significantly and positively related to PSII thermal tolerance when all species were explored together regardless of their invasive nature. However, this relationship did not persist under water stress and invasive species had higher plastic responses than Mediterranean natives resulting in higher leaf temperatures. Higher PSII thermal tolerance could explain invasiveness because it allows for longer periods of carbon acquisition under water stress. In fact, PSII thermal tolerance was positively related to the PET of the invaded and native areas of the Iberian Peninsula. PSII thermal tolerance was not related to PET at the native range of the invasive species, suggesting that successful invasive species were plastic enough to cope with novel dry conditions of the Iberian Peninsula. Moreover, our phylogenetic results indicate that future scenarios of increased aridity in MTE associated to climate change will filter invasion success by taxonomic identity. This study reveals the importance of studying ecophysiological traits to understand and better predict future biological invasions. 相似文献
43.
Luiz Antonio Dutra Jéssica Frade O. Guanaes Nadine Johmann Maria Elisa Lopes Pires Chung Man Chin Sisi Marcondes Jean Leandro Dos Santos 《Bioorganic & medicinal chemistry letters》2017,27(11):2450-2453
Resveratrol (RVT) is a stilbene with a protective effect on the cardiovascular system; however, drawbacks including low bioavailability and fast metabolism limit its efficacy. In this work we described new resveratrol derivatives with nitric oxide (NO) release properties, ability to inhibit platelet aggregation and in vivo antithrombotic effect. Compounds (4a–f) were able to release NO in vitro, at levels ranging from 24.1% to 27.4%. All compounds (2a–f and 4a–f) have exhibited platelet aggregation inhibition using as agonists ADP, collagen and arachidonic acid. The most active compound (4f) showed reduced bleeding time compared to acetylsalicylic acid (ASA) and protected up to 80% against in vivo thromboembolic events. These findings suggest that hybrid resveratrol-furoxan (4f) is a novel lead compound able to prevent platelet aggregation and thromboembolic events. 相似文献
44.
Liliane Viana Pires Adriana Aparecida Siviero-Miachon Angela Maria Spinola-Castro José Alexandre Coelho Pimentel Luciana Sigueta Nishimura Carla Soraya Costa Maia Silvia Maria Franciscato Cozzolino 《Biological trace element research》2017,176(2):217-224
Studies about selenium status in patients with Turner syndrome (TS) are non-existent in the literature. The aim of this study was to evaluate selenium status in patients with TS, while considering the different ages of the studied population and the relation with body composition. In total, 33 patients with TS were evaluated and grouped according to their developmental stages (children, adolescents, and adults). Selenium concentrations in their plasma, erythrocytes, urine, and nails were determined by using hydride generation atomic absorption spectrometry and erythrocyte glutathione peroxidase activity were measured by using Randox commercial kits. Additionally, height, weight, body fat percentage, waist circumference, and waist-height ratio were measured to characterize the patients. No differences in the selenium concentrations in the plasma, erythrocyte, urine, and nails or in the glutathione peroxidase activity were observed among the age groups (p > 0.05). The evaluated selenium levels were less than the established normal ones. The patients with larger waist circumference, body fat percentage, body mass index, and waist-height ratio showed lower glutathione peroxidase enzyme activity (p = 0.023). The present study shows that most patients with TS are deficient in selenium and that those with a greater accumulation of body fat have a lower GPx activity. 相似文献
45.
Antonio A. Pires Jorge L. Ramirez Pedro M. GalettiJr Waldo P. Troy Patricia D. Freitas 《Genetica》2017,145(3):335-340
The genus Zungaro contains some of the largest catfish in South America. Two valid species are currently recognized: Zungaro jahu, inhabiting the Paraná and Paraguay basins, and Zungaro zungaro, occurring in the Amazonas and Orinoco basins. Analysing Zungaro specimens from the Amazonas, Orinoco, Paraguay and Paraná basins, based on the sequencing of COI and D-loop, we found at least three MOTUs, indicating the existence of hidden diversity within this fish group. Considering the ecological and economic values of this fish, our results are surely welcomed for its conservation, disclosing new findings on its diversity and pointing out the necessity for a detailed taxonomic revision. 相似文献
46.
Transgenic cotton expressing Cry10Aa toxin confers high resistance to the cotton boll weevil 下载免费PDF全文
Thuanne Pires Ribeiro Fabricio Barbosa Monteiro Arraes Isabela Tristan Lourenço‐Tessutti Marilia Santos Silva Maria Eugênia Lisei‐de‐Sá Wagner Alexandre Lucena Leonardo Lima Pepino Macedo Janaina Nascimento Lima Regina Maria Santos Amorim Sinara Artico Márcio Alves‐Ferreira Maria Cristina Mattar Silva Maria Fatima Grossi‐de‐Sa 《Plant biotechnology journal》2017,15(8):997-1009
47.
Valéria Nogueira Machado Stuart C. Willis Aylton S. Teixeira Tomas Hrbek Izeni Pires Farias 《Environmental Biology of Fishes》2017,100(1):1-16
In the present study, sequences of the mtDNA control region (834 bp) were analyzed from 337 specimens of Prochilodus nigricans from sites along the main channel of the Amazonas River and three major tributaries, Madeira, Purus, and Juruá. The results of the analysis of molecular variance revealed that a large part of the genetic variation occurred within the populations analyzed (~85 %). Analysis with SAMOVA and Barriers suggested that the upper Madeira River and Purus Rivers had diverged genetically from the other samples, indicating restricted gene flow among these areas, while sites within the remaining range exhibited relatively little population structure. The high degree of structuring observed in the Madeira River basin population may be attributed to the presence of rapids along its upper course, while the genetic divergence found in the upper Purus River suggests historical connection between the upper Purus and upper Madeira Rivers followed by slow genetic drift due to large effective population sizes. However, given the life history and hypothesized evolutionary strategy of this species, we urge caution in interpreting that this targeted species is not at risk of overexploitation due to contemporary abundance. In order to preserve genetic diversity, we recommend enforcement of management regimes for regional stocks. 相似文献
48.
Ana Sílvia Franco Pinheiro Moreira José Pires de Lemos Filho Gerhard Zotz Rosy Mary dos Santos Isaias 《Flora》2009,204(8):604-611
This study compares photosynthetic and structural features of Dichaea cogniauxiana and Epidendrum secundum leaves and roots. The diurnal titratable acidity fluctuations indicated crassulacean acid metabolism (CAM) in E. secundum leaves, associated with anatomical features like thick cuticle, large and vacuolated cells, and reduced stomata size and frequency. Roots of both species had chloroplasts in their cortical parenchyma. However, neither the roots nor D. cogniauxiana leaves did show tissue sap acidity fluctuations. This indicates C3 metabolism in these organs. This lack of oscillation of organic acids in Epidendrum roots was at odds with a CAM-like 13C ratio, suggesting that in spite of active CO2 fixation in roots during the day, the bulk of carbon is imported from the leaves. Roots of both species showed Fv/Fm, ΔF/Fm′, ETR values similar to reports from other non-foliar photosynthetic organs. Besides reducing root carbon cost, root photosynthesis may also be important by alleviating potential hypoxia, since water-saturated velamen severely impedes the gas exchange between radicular cortex. 相似文献
49.
Reactions of the adduct UCl3·(THF)x (THF = tetrahydrofuran) with compounds of the type K[HnBL4?n], where L = pyrazole or 3,5-dimethylpyrazole, are presented. Based on the results obtained the two compounds UCl2H2BPz2·THF and UCl2HBPz3·THF were isolated. 相似文献
50.