全文获取类型
收费全文 | 355篇 |
免费 | 23篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 35篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 21篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1974年 | 1篇 |
排序方式: 共有378条查询结果,搜索用时 15 毫秒
41.
42.
Kevin Lambeets Frederik Hendrickx Stijn Vanacker Kris Van Looy Jean-Pierre Maelfait Dries Bonte 《Biodiversity and Conservation》2008,17(13):3133-3148
We assessed the composition of spider and carabid beetle assemblages along river banks from the Common Meuse (Belgium) to
determine their relationships with local topographical and landscape-related characteristics. Data were gathered with pitfall
traps in 1998 and explored by ordination and grouping methods. Our analysis revealed that the presence of xerothermic spider
species was limited to scarcely covered, less dynamic gravel banks. Riparian spider species were found on frequently flooded
as well as on rather elevated and high gravel banks, while riparian carabid beetles were dominant on all sampled banks. The
level of flooding disturbance, the vegetation density and the presence of silt appeared to be the most important environmental
determinants of spider and carabid beetle assemblage structure. Consequently, local environmental factors influence species
occurrence patterns in a similar way for the two investigated arthropod groups. Nevertheless, distinct ecological groups are
differently ordered along the prime environmental gradients. Nature management should therefore consider the conservation,
restoration and connectivity of both dynamic and more elevated banks in order to obtain a high degree of local and regional
heterogeneity throughout the river system. 相似文献
43.
Characterization of an Autotrophic Nitrogen-Removing Biofilm from a Highly Loaded Lab-Scale Rotating Biological Contactor 总被引:7,自引:2,他引:5
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kris Pynaert Barth F. Smets Stijn Wyffels Daan Beheydt Steven D. Siciliano Willy Verstraete 《Applied microbiology》2003,69(6):3626-3635
In this study, a lab-scale rotating biological contactor (RBC) treating a synthetic NH4+ wastewater devoid of organic carbon and showing high N losses was examined for several important physiological and microbial characteristics. The RBC biofilm removed 89% ± 5% of the influent N at the highest surface load of approximately 8.3 g of N m−2 day−1, with N2 as the main end product. In batch tests, the RBC biomass showed good aerobic and anoxic ammonium oxidation (147.8 ± 7.6 and 76.5 ± 6.4 mg of NH4+-N g of volatile suspended solids [VSS]−1 day−1, respectively) and almost no nitrite oxidation (< 1 mg of N g of VSS−1 day−1). The diversity of aerobic ammonia-oxidizing bacteria (AAOB) and planctomycetes in the biofilm was characterized by cloning and sequencing of PCR-amplified partial 16S rRNA genes. Phylogenetic analysis of the clones revealed that the AAOB community was fairly homogeneous and was dominated by Nitrosomonas-like species. Close relatives of the known anaerobic ammonia-oxidizing bacterium (AnAOB) Kuenenia stuttgartiensis dominated the planctomycete community and were most probably responsible for anoxic ammonium oxidation in the RBC. Use of a less specific planctomycete primer set, not amplifying the AnAOB, showed a high diversity among other planctomycetes, with representatives of all known groups present in the biofilm. The spatial organization of the biofilm was characterized using fluorescence in situ hybridization (FISH) with confocal scanning laser microscopy (CSLM). The latter showed that AAOB occurred side by side with putative AnAOB (cells hybridizing with probe PLA46 and AMX820/KST1275) throughout the biofilm, while other planctomycetes hybridizing with probe PLA886 (not detecting the known AnAOB) were present as very conspicuous spherical structures. This study reveals that long-term operation of a lab-scale RBC on a synthetic NH4+ wastewater devoid of organic carbon yields a stable biofilm in which two bacterial groups, thought to be jointly responsible for the high autotrophic N removal, occur side by side throughout the biofilm. 相似文献
44.
45.
46.
47.
Effects of habitat fragmentation on provisioning rates, diet and breeding success in two species of tit (great tit and blue tit) 总被引:2,自引:0,他引:2
Nadia Nour David Currie Erik Matthysen Raoul Van Damme André A. Dhondt 《Oecologia》1998,114(4):522-530
The aim of this study was to examine the effects of forest fragmentation on the ability of parent birds to provide their
young with an adequate food supply. To examine whether prey population densities of the great tit (Parus major L.) and the blue tit (P. caeruleus L.) vary between study areas in different forest size classes we compared provisioning rates and chick diet and related these
parameters to breeding success. We filmed 217 nests over two breeding seasons and collected data on frass fall as a general
estimate of caterpillar availability. Nests which were attended by none or one parent only during filming (n = 46) were excluded from the analyses. In both years and for both species feeding rates were highest in the smallest fragments
and lowest in the large forest. There was also a suggestion that differences in feeding rates between areas vary between years.
We found no consistent tendency for prey size to change with forest size, although both species brought slightly smaller prey
items to the nest in the smallest forest fragments and feeding rates correlated negatively with prey size. Caterpillars were
the main item fed to nestlings, in both species. We found no evidence to suggest that either frass fall or the proportion
of caterpillars in the diet varied with forest size. There was also no correlation between mean frass fall and the total number
of caterpillars brought to the nests, in either species. Breeding success, as measured by clutch size, brood size, fledging
weight and fledging success, did not differ between the small fragments and the large forest, in either species. There was
also no relationship between provisioning rate (as concerns volume of prey fed to nestlings and the quality of chick diet)
and breeding success parameters. In conclusion, this study does not suggest suboptimal foraging or breeding conditions in
small fragments compared to a nearby large forest, for either species.
Received: 23 June 1997 / Accepted: 29 December 1997 相似文献
48.
49.
50.
Stijn Vanderzande Diego Micheletti Michela Troggio Mark W. Davey Johan Keulemans 《Tree Genetics & Genomes》2017,13(6):125
The identification of molecular markers associated with economic and quality traits will help improve breeding for new apple (Malus × domestica Borkh.) cultivars. Tools such as the 8K apple SNP array developed by the RosBREED consortium allow for high-throughput genotyping of SNP polymorphisms within collections. However, genetic characterization and the identification of population stratification and kinship within germplasm collections is a fundamental prerequisite for identifying robust marker–trait associations. In this study, a collection of apple germplasm originally developed for plant architectural studies and consisting of both non-commercial/local and elite accessions was genotyped using the 8K apple SNP array to identify cryptic relationships between accessions, to analyze population structure and to calculate the linkage disequilibrium (LD). A total of nine pairs of synonyms and several triploids accessions were identified within the 130 accessions genotyped. In addition, most of the known parent-child relations were confirmed, and several putative, previously unknown parent-child relations were identified among the local accessions. No clear subgroups could be identified although some separation between local and elite accessions was evident. The study of LD showed a rapid decay in our collection, indicating that a larger number of SNPs is necessary to perform whole genome association mapping. Finally, an association mapping effort for architectural traits was carried out on a small number of accessions to estimate the feasibility of this approach. 相似文献