全文获取类型
收费全文 | 229篇 |
免费 | 39篇 |
出版年
2021年 | 2篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 11篇 |
2011年 | 5篇 |
2010年 | 9篇 |
2009年 | 3篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 15 毫秒
51.
Marie-Lise Benot Patrick Saccone Emmanuelle Pautrat Rachel Vicente Marie-Pascale Colace Karl Grigulis Jean-Christophe Clément Sandra Lavorel 《Ecosystems》2014,17(3):458-472
Mowing is known to favor plant diversity and influence ecosystem functioning in semi-natural grasslands. This effect could be influenced by climate variability, especially in regions with harsh climate, such as subalpine zones. In particular, short-term extreme weather fluctuations may induce rapid plant responses, affecting in turn the response to mowing. We tested the effects of concomitant summer weather manipulation and mowing on a subalpine grassland in the Central French Alps for two consecutive years. We addressed two questions: (1) How is a subalpine grassland affected by extreme summer weather? (2) Does extreme summer weather alter mowing effects on the grassland plant diversity and functioning? We used a multi-level, integrative approach assessing the responses of six abundant plant species, as well as effects on plant community structure, biomass production, and litter decomposition rates. Extreme summer weather was simulated by increasing summer temperature by 1.1°C, and decreasing summer rainfall by 80%—resulting in a 30% decrease in total annual precipitation. In addition, a heat-wave event was simulated during the first year of the experiment. This weather manipulation was combined with a late-summer mowing treatment (mown vs. unmown). Extreme summer weather mainly increased leaf senescence and decreased plant vegetative growth. Leaf litter decomposition was slowed, but only for species characterized by the fastest rates of litter decomposition. Mowing increased plant diversity by restricting the dominant grass species, thereby favoring subordinates. In the short term, this subalpine grassland was rather resistant to extreme summer weather, whereas mowing cessation remained the main factor affecting its biodiversity. 相似文献
52.
Facilitation in plant communities: the past, the present, and the future 总被引:24,自引:11,他引:24
Rob W. Brooker Fernando T. Maestre Ragan M. Callaway Christopher L. Lortie Lohengrin A. Cavieres Georges Kunstler Pierre Liancourt Katja Tielbörger Justin M. J. Travis Fabien Anthelme Cristina Armas Lluis Coll Emmanuel Corcket Sylvain Delzon Estelle Forey Zaal Kikvidze Johan Olofsson Francisco Pugnaire Constanza L. Quiroz Patrick Saccone Katja Schiffers Merav Seifan Blaize Touzard Richard Michalet 《Journal of Ecology》2008,96(1):18-34
53.
The mitochondrial genome (mtDNA), due to its peculiar features such as exclusive presence of orthologous genes, uniparental inheritance, lack of recombination, small size and constant gene content, certainly represents a major model system in studies on evolutionary genomics in metazoan. In 800 million years of evolution the gene content of metazoan mitochondrial genomes has remained practically frozen but several evolutionary processes have taken place. These processes, reviewed here, include rearrangements of gene order, changes in base composition and arising of compositional asymmetry between the two strands, variations in the genetic code and evolution of codon usage, lineage-specific nucleotide substitution rates and evolutionary patterns of mtDNA control regions. 相似文献
54.
55.
56.
D Càllari G Blandino V Saccone C D'Amico A Billitteri 《Bollettino della Società italiana di biologia sperimentale》1992,68(12):783-787
The aim of this study was to investigate if the association of both hyperthermic and Retinol treatment of HTC hepatoma cells could be useful in antitumor therapy. Treatment with 5 microM Retinol was carried out before or after hyperthermia (42 degrees C or 44 degrees C, one hour; in the latter case it was performed in cells already thermo-selected. We took into consideration two parameters, i.e. the number of the collected vital cells (evaluated by the trypan blue-exclusion test) and the clonal efficiency of these cells (calculated as number of colonies obtained from 250 cells cultured for 5 days). Thermal treatment alone caused a decrease of the number of the collected vital cells and of their clonal efficiency only in the cell cultures incubated at 44 degrees C. Instead the control thermo-selected cells, both at 42 degrees C and at 44 degrees C, showed both decreased clonal efficiency and yield of the vital cells. Compared with the control cultures treated with 0.1% Ethanol, used as vitamin A solvent, only cell cultures treated with Retinol before hyperthermia showed a decreased number of collected viable cells, nevertheless their clonal efficiency was unchanged. 相似文献
57.
58.
Multisequence comparisons in protein coding genes. Search for functional constraints 总被引:1,自引:0,他引:1
A very powerful method for detecting functional constraints operative in biological macromolecules is presented. This method entails performing a base permanence analysis of protein coding genes at each codon position simultaneously in different species. It calculates the degree of permanence of subregions of the gene by dividing it into segments, c codons long, counting how many sites remain unchanged in each segment among all species compared. By comparing the base permanence among several sequences with the expectations based on a stochastic evolutionary process, gene regions showing different degrees of conservation can be selected. This means that wherever the permanence deviates significantly from the expected value generated by the simulation, the corresponding regions are considered "constrained" or "hypervariable". The constrained regions are of two types: alpha and beta. The alpha regions result from constraints at the amino acid level, whereas the beta regions are those probably involved in "control" processing. The method has been applied to mitochondrial genes coding for subunit 6 of the ATPase and subunit 1 of the cytochrome oxidase in four mammalian species: human, rat, mouse, and cow. In the two mitochondrial genes a few regions that are highly conserved in all codon positions have been identified. Among these regions a sequence, common to both genes, that is complementary to a strongly conserved region of 12S rRNA has been found. This method can also be of great help in studying molecular evolution mechanisms. 相似文献
59.
Marcella Attimonelli Cecilia Lanave Elisabetta Sbisa Giuliano Preparata Cecilia Saccone 《Cell biochemistry and biophysics》1985,7(4):239-250
A very powerful method for detecting functional constraints operative in biological macromolecules is presented. This method
entails performing a base permanence analysis of protein coding genes at each codon position simultaneously in different species.
It calculates the degree of permanence of subregions of the gene by dividing it into segments,c codons long, counting how many sites remain unchanged in each segment among all species compared. By comparing the base permanence
among several sequences with the expectations based on a stochastic evolutionary process, gene regions showing different degrees
of conservation can be selected. This means that wherever the permanence deviates significantly from the expected value generated
by the simulation, the corresponding regions are considered “constrained” or “hypervariable”.
The constrained regions are of two types: α and β. The α regions result from constraints at the amino acid level, whereas
the β regions are those probably involved in “control” processing. The method has been applied to mitochondrial genes coding
for subunit 6 of the ATPase and subunit 1 of the cytochrome oxidase in four mammalian species: human, rat, mouse, and cow.
In the two mitochondrial genes a few regions that are highly conserved in all codon positions have been identified. Among
these regions a sequence, common to both genes, that is complementary to a strongly conserved region of 12S rRNA has been
found. This method can also be of great help in studying molecular evolution mechanisms. 相似文献
60.
Elisabetta Sbisà Graziano Pesole Apollonia Tullo Cecilia Saccone 《Journal of molecular evolution》1996,43(1):46-57
We report a detailed evolutionary study of the RNase P- and RNase MRP- associated RNAs. The analyses were performed on all
the available complete sequences of RNase MRP (vertebrates, yeast, plant), nuclear RNase P (vertebrates, yeast), and mitochondrial
RNase P (yeast) RNAs. For the first time the phylogenetic distance between these sequences and the nucleotide substitution
rates have been quantitatively measured.
The analyses were performed by considering the optimal multiple alignments obtained mostly by maximizing similarity between
primary sequences. RNase P RNA and MRP RNA display evolutionary dynamics following the molecular clock. Both have similar
rates and evolve about one order of magnitude faster than the corresponding small rRNA sequences which have been, so far,
the most common gene markers used for phylogeny. However, small rRNAs evolve too slowly to solve close phylogenetic relationships
such as those between mammals. The quicker rate of RNase P and MRP RNA allowed us to assess phylogenetic relationships between
mammals and other vertebrate species and yeast strains. The phylogenetic data obtained with yeasts perfectly agree with those
obtained by functional assays, thus demonstrating the potential offered by this approach for laboratory experiments.
Correspondence to: E. Sbisà 相似文献