全文获取类型
收费全文 | 1684篇 |
免费 | 154篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 43篇 |
2020年 | 21篇 |
2019年 | 40篇 |
2018年 | 49篇 |
2017年 | 35篇 |
2016年 | 52篇 |
2015年 | 93篇 |
2014年 | 89篇 |
2013年 | 106篇 |
2012年 | 151篇 |
2011年 | 122篇 |
2010年 | 85篇 |
2009年 | 76篇 |
2008年 | 101篇 |
2007年 | 77篇 |
2006年 | 93篇 |
2005年 | 71篇 |
2004年 | 84篇 |
2003年 | 61篇 |
2002年 | 65篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1972年 | 5篇 |
排序方式: 共有1839条查询结果,搜索用时 15 毫秒
61.
62.
63.
Kvin Cilleros Alice Valentini Luc Allard Tony Dejean Roselyne Etienne Gaël Grenouillet Amaia Iribar Pierre Taberlet Rgis Vigouroux Sbastien Brosse 《Molecular ecology resources》2019,19(1):27-46
Determining the species compositions of local assemblages is a prerequisite to understanding how anthropogenic disturbances affect biodiversity. However, biodiversity measurements often remain incomplete due to the limited efficiency of sampling methods. This is particularly true in freshwater tropical environments that host rich fish assemblages, for which assessments are uncertain and often rely on destructive methods. Developing an efficient and nondestructive method to assess biodiversity in tropical freshwaters is highly important. In this study, we tested the efficiency of environmental DNA (eDNA) metabarcoding to assess the fish diversity of 39 Guianese sites. We compared the diversity and composition of assemblages obtained using traditional and metabarcoding methods. More than 7,000 individual fish belonging to 203 Guianese fish species were collected by traditional sampling methods, and ~17 million reads were produced by metabarcoding, among which ~8 million reads were assigned to 148 fish taxonomic units, including 132 fish species. The two methods detected a similar number of species at each site, but the species identities partially matched. The assemblage compositions from the different drainage basins were better discriminated using metabarcoding, revealing that while traditional methods provide a more complete but spatially limited inventory of fish assemblages, metabarcoding provides a more partial but spatially extensive inventory. eDNA metabarcoding can therefore be used for rapid and large‐scale biodiversity assessments, while at a local scale, the two approaches are complementary and enable an understanding of realistic fish biodiversity. 相似文献
64.
Félix-Faure Jim Gaillard Jérémie Descloux Stéphane Chanudet Vincent Poirel Alain Baudoin Jean-Marc Avrillier Jean-Noël Millery Annie Dambrine Etienne 《Ecosystems》2019,22(2):312-330
Ecosystems - When a water reservoir is created, the pre-existing soils and vegetation are flooded. Here, we took advantage of the complete emptying of the Sarrans Reservoir, which was flooded... 相似文献
65.
66.
Sbastien Bontemps‐Gallo Marion Fernandez Amlie Dewitte Etienne Raphaël Frank C. Gherardini Pradel Elizabeth Lionel Koch Fabrice Biot Angline Reboul Florent Sebbane 《Molecular microbiology》2019,112(5):1471-1482
The flea’s lumen gut is a poorly documented environment where the agent of flea‐borne plague, Yersinia pestis, must replicate to produce a transmissible infection. Here, we report that both the acidic pH and osmolarity of the lumen’s contents display simple harmonic oscillations with different periods. Since an acidic pH and osmolarity are two of three known stimuli of the OmpR‐EnvZ two‐component system in bacteria, we investigated the role and function of this Y. pestis system in fleas. By monitoring the in vivo expression pattern of three OmpR‐EnvZ‐regulated genes, we concluded that the flea gut environment triggers OmpR‐EnvZ. This activation was not, however, correlated with changes in pH and osmolarity but matched the pattern of nutrient depletion (the third known stimulus for OmpR‐EnvZ). Lastly, we found that the OmpR‐EnvZ and the OmpF porin are needed to produce the biofilm that ultimately obstructs the flea’s gut and thus hastens the flea‐borne transmission of plague. Taken as a whole, our data suggest that the flea gut is a complex, fluctuating environment in which Y. pestis senses nutrient depletion via OmpR‐EnvZ. Once activated, the latter triggers a molecular program (including at least OmpF) that produces the biofilm required for efficient plague transmission. 相似文献
67.
Valérian Meline Wesley Delage Chrystelle Brin Camille Li-Marchetti Daniel Sochard Matthieu Arlat Céline Rousseau Armelle Darrasse Martial Briand Guillaume Lebreton Perrine Portier Marion Fischer-Le Saux Karine Durand Marie-Agnès Jacques Etienne Belin Tristan Boureau 《Molecular Plant Pathology》2019,20(1):33-50
Cases of emergence of novel plant-pathogenic strains are regularly reported that reduce the yields of crops and trees. However, the molecular mechanisms underlying such emergence are still poorly understood. The acquisition by environmental non-pathogenic strains of novel virulence genes by horizontal gene transfer has been suggested as a driver for the emergence of novel pathogenic strains. In this study, we tested such an hypothesis by transferring a plasmid encoding the type 3 secretion system (T3SS) and four associated type 3 secreted proteins (T3SPs) to the non-pathogenic strains of Xanthomonas CFBP 7698 and CFBP 7700, which lack genes encoding T3SS and any previously known T3SPs. The resulting strains were phenotyped on Nicotiana benthamiana using chlorophyll fluorescence imaging and image analysis. Wild-type, non-pathogenic strains induced a hypersensitive response (HR)-like necrosis, whereas strains complemented with T3SS and T3SPs suppressed this response. Such suppression depends on a functional T3SS. Amongst the T3SPs encoded on the plasmid, Hpa2, Hpa1 and, to a lesser extent, XopF1 collectively participate in suppression. Monitoring of the population sizes in planta showed that the sole acquisition of a functional T3SS by non-pathogenic strains impairs growth inside leaf tissues. These results provide functional evidence that the acquisition via horizontal gene transfer of a T3SS and four T3SPs by environmental non-pathogenic strains is not sufficient to make strains pathogenic. In the absence of a canonical effector, the sole acquisition of a T3SS seems to be counter-selective, and further acquisition of type 3 effectors is probably needed to allow the emergence of novel pathogenic strains. 相似文献
68.
Habitat turnover concomitantly causes destruction and creation of habitat patches. Following such a perturbation, metapopulations harbor either an extinction debt or an immigration credit, that is the future decrease or increase in population numbers due to this disturbance. Extinction debt and immigration credit are rarely considered simultaneously and disentangled from the relaxation time (time to new equilibrium). In this contribution, we test the relative importance of two potential drivers of time-delayed metapopulation dynamics: the spatial configuration of the habitat turnover and species dispersal ability. We provide a simulation-based investigation projecting metapopulation dynamics following habitat turnover in virtual landscapes. We consider two virtual species (a short-distance and a long-distance disperser) and five scenarios of habitat turnover depending on net habitat loss or gain and habitat aggregation. Our analyses reveal that (a) the main determinant of the magnitude of the extinction debt or immigration credit is the net change in total habitat area, followed by species dispersal distance and finally by the post-turnover habitat aggregation; (b) relaxation time weakly depends on the magnitude of the immigration credit or of the extinction debt; (c) the main determinant of relaxation time is dispersal distance followed by the net change in total habitat area and finally by the post-turnover habitat aggregation. These results shed light on the relative importance of dispersal ability and habitat turnover spatial structure on the components of time-delayed metapopulation dynamics. 相似文献
69.
Etienne X. Keller Vincent de Coninck Marie Audouin Steeve Doizi Dominique Bazin Michel Daudon Olivier Traxer 《Journal of biophotonics》2019,12(4)
Urinary stones can be readily disintegrated by Holmium:YAG laser (Holmium laser lithotripsy), resulting in a mixture of small stone dust particles, which will spontaneously evacuate with urine and larger residual fragments (RF) requiring mechanical retrieval. Differences between fragments and dust have not been well characterized. Also, it remains unknown how the recently introduced “Moses technology” may alter stone disintegration products. Three complementary analytical techniques have been used in this study to offer an in‐depth characterization of disintegration products after in vitro Holmium laser lithotripsy: stereoscopic microscopy, scanning electron microscopy and Fourier‐transform infrared spectroscopy. Dust was separated from fragments based on its floating ability in saline irrigation. Depending on initial crystalline constituents, stone dust either conserved attributes found in larger RFs or showed changes in crystalline organization. These included conversion of calcium oxalate dihydrate towards calcium oxalate monohydrate, changes in carbapatite spectra towards an amorphous phase, changes of magnesium ammonium phosphate towards a differing amorphous and crystalline phase and the appearance of hydroxyapatite on brushite fragments. Comparatively, “Moses technology” produced more pronounced changes. These findings provide new insights suggesting a photothermal effect occurring in Holmium laser lithotripsy. Figure: Appearance of hydroxyapatite hexagons on stone dust collected after Holmium laser lithotripsy of a brushite stone using “Moses technology.” 相似文献
70.