全文获取类型
收费全文 | 14957篇 |
免费 | 1288篇 |
国内免费 | 12篇 |
专业分类
16257篇 |
出版年
2023年 | 66篇 |
2022年 | 130篇 |
2021年 | 276篇 |
2020年 | 184篇 |
2019年 | 202篇 |
2018年 | 272篇 |
2017年 | 222篇 |
2016年 | 412篇 |
2015年 | 660篇 |
2014年 | 810篇 |
2013年 | 984篇 |
2012年 | 1232篇 |
2011年 | 1170篇 |
2010年 | 750篇 |
2009年 | 734篇 |
2008年 | 952篇 |
2007年 | 1009篇 |
2006年 | 902篇 |
2005年 | 823篇 |
2004年 | 825篇 |
2003年 | 810篇 |
2002年 | 742篇 |
2001年 | 157篇 |
2000年 | 115篇 |
1999年 | 167篇 |
1998年 | 199篇 |
1997年 | 147篇 |
1996年 | 117篇 |
1995年 | 127篇 |
1994年 | 100篇 |
1993年 | 102篇 |
1992年 | 112篇 |
1991年 | 62篇 |
1990年 | 66篇 |
1989年 | 48篇 |
1988年 | 49篇 |
1987年 | 33篇 |
1986年 | 38篇 |
1985年 | 39篇 |
1984年 | 44篇 |
1983年 | 36篇 |
1982年 | 43篇 |
1981年 | 39篇 |
1980年 | 27篇 |
1979年 | 29篇 |
1978年 | 17篇 |
1977年 | 33篇 |
1976年 | 30篇 |
1975年 | 15篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
Philippe Latour Christel Thauvin-Robinet Pierre Soichot Laurence Faivre Martine Mayençon Emmanuel Broussolle William Camu Robert Rousson 《American journal of human genetics》2010,86(1):77-82
Charcot-Marie-Tooth disease (CMT) is the most common cause of inherited peripheral neuropathy, with an estimated frequency of 1/2500. We studied a large family with 17 patients affected by the axonal form of CMT (CMT2). Analysis of the 15 genes or loci known to date was negative. Genome-wide genotyping identified a CMT2 locus in 16q21-q23 between D16S3050 and D16S3106. The maximum two-point LOD score was 4.77 at θ = 0 for marker D16S3050. Sequencing of candidate genes identified a unique mutation, c.986G>A (p.Arg329His), affecting a totally conserved amino acid in the helical domain of cytoplasmic alanyl-tRNA synthetase (AlaRS). A second family with the same mutation and a different founder was then identified in a cohort of 91 CMT2 families. Although mislocation of mutant Arg329His-AlaRS in axons remains to be evaluated, experimental data point mostly to a quantitative reduction in tRNAAla aminoacylation. Aminoacylation and editing functions closely cooperate in AlaRS, and Arg329His mutation could also lead to qualitative errors participating in neurodegeneration. Our report documents in 18 patients the deleterious impact of a mutation in human cytoplasmic AlaRS and broadens the spectrum of defects found in tRNA synthetases. Patients present with sensory-motor distal degeneration secondary to predominant axonal neuropathy, slight demyelination, and no atypical or additional CNS features. 相似文献
952.
953.
Philippe FX Canart B Laitat M Wavreille J Bartiaux-Thill N Nicks B Cabaraux JF 《Animal : an international journal of animal bioscience》2010,4(10):1716-1724
In the European Union, the group-housed pregnant sows have to have a minimal legal available area of 2.25 m2/sow. However, it has been observed that an increased space allowance reduces agonistic behaviour and consecutive wounds and thus induces better welfare conditions. But, what about the environmental impacts of this greater available area? Therefore, the aim of this study was to quantify pollutant gases emissions (nitrous oxide, N2O, methane, CH4, carbon dioxide, CO2 and ammonia, NH3), according to the space allowance in the raising of gestating sows group-housed on a straw-based deep litter. Four successive batches of 10 gestating sows were each divided into two homogeneous groups and randomly allocated to a treatment: 2.5 v. 3.0 m2/sow. The groups were separately kept in two identical rooms. A restricted conventional cereals based diet was provided once a day in individual feeding stalls available only during the feeding time. Rooms were automatically ventilated. The gas emissions were measured by infra red photoacoustic detection during six consecutive days at the 6th, 9th and 12th weeks of gestation. Sows performance (body weight gain, backfat thickness, number and weight of piglets) was not significantly different according to the space allowance. In the room with 3.0 m2/sow and compared with the room with 2.5 m2/sow, gaseous emissions were significantly greater for NH3 (6.29 v. 5.37 g NH3-N/day per sow; P < 0.01) and significantly lower for N2O (1.78 v. 2.48 g N2O-N/day per sow; P < 0.01), CH4 (10.15 v. 15.21 g/day per sow; P < 0.001), CO2 equivalents (1.11 v. 1.55 kg/day per sow; P < 0.001), CO2 (2.12 v. 2.41 kg/day per sow; P < 0.001) and H2O (3.10 v. 3.68 kg/day per sow; P < 0.001). In conclusion, an increase of the available area for group-housed gestating sow kept on straw-based deep litter seems to be ambiguous on an environmental impacts point of view. Compared with a conventional and legal available area, it favoured NH3 emissions, probably due to an increased emitting surface. However, about greenhouse gases, it decreased N2O, CH4 and CO2 emissions, probably due to reduced anaerobic conditions required for their synthesis, and led to a reduction of CO2 equivalents emissions. 相似文献
954.
955.
Dispersal mood revealed by shifts from routine to direct flights in the meadow brown butterfly Maniola jurtina 总被引:1,自引:0,他引:1
Thomas Delattre Françoise Burel Antoine Humeau Virginie M. Stevens Philippe Vernon Michel Baguette 《Oikos》2010,119(12):1900-1908
A comprehensive mechanistic approach to dispersal requires the translation of the whole mobility register of the target organism into movement rules that could subsequently be used to model its displacements. According to the optimality paradigm, this procedure implies a cost–benefit analysis of mobility patterns taking into account not only movements, but also their external context and the internal state of the moving individuals. Using this framework, we detected a ‘dispersal mood’ in some individuals of the meadow brown butterfly Maniola jurtina. These adopted a direct flight strategy, which was topologically different from the previously documented foray search strategy. Those individuals that used the direct flight strategy moved straighter as soon as they left the habitat and avoided heading back to their patch of origin, which is the best inter‐patch search strategy when dispersal risks and costs are high. The direct flight strategy was conditional to sex: females used it twice as much as males. We suggest that this sex bias was due to female investment in offspring, which is maximized by male avoidance and spatial bet hedging. Inter‐patch dispersal of gravid females is crucial for the persistence of M. jurtina populations in spatially and temporally unpredictable environments. 相似文献
956.
Calvaruso Christophe Turpault Marie-Pierre Uroz Stéphane Leclerc Elisabeth Kies Antoine Frey-Klett Pascale 《Plant and Soil》2010,328(1-2):145-154
The role of ectomycorrhizal fungi on mineral nutrient mobilization and uptake is crucial for tree nutrition and growth in temperate forest ecosystems. By using a “mineral weathering budget” approach, this study aims to quantify the effect of the symbiosis with the ectomycorrhizal model strain Laccaria bicolor S238N on mineral weathering and tree nutrition, carrying out a column experiment with a quartz/biotite substrate. Each column was planted with one Scots pine (Pinus sylvestris L.) non-mycorrhizal or mycorrhizal with L. bicolor, with exception of the abiotic control treatment. The columns were continuously supplied with a nutrient-poor solution. A mineral weathering budget was calculated for K and Mg. The pine shoot growth was significantly increased (73%) when plants were mycorrhizal with L. bicolor. Whatever their mycorrhizal status, pines increased mineral weathering by factors 1.5 to 2.1. No difference between non-mycorrhizal and mycorrhizal pine treatments was revealed, however, mycorrhizal pines assimilated significantly more K and Mg. This suggests that in our experimental conditions, L. bicolor S238N improved shoot growth and K and Mg assimilation in Scots pine mainly by increasing the uptake of dissolved nutrients, linked to a better exploration and exploitation of the soil by the mycorrhizal roots. 相似文献
957.
958.
Raul Herrera Catherine Krier Celine Lalanne ElHadji Maodo Ba Alexia Stokes Franck Salin Thierry Fourcaud Stéphane Claverol Christophe Plomion 《BMC plant biology》2010,10(1):217
Background
Plants are subjected to continuous stimuli from the environment and have evolved an ability to respond through various growth and development processes. Phototropism and gravitropism responses enable the plant to reorient with regard to light and gravity. 相似文献959.
Valeria Mozzetti Franck Grattepanche Déborah Moine Bernard Berger Enea Rezzonico Leo Meile Fabrizio Arigoni Christophe Lacroix 《Microbial cell factories》2010,9(1):60
Background
Oxidative stress can severely compromise viability of bifidobacteria. Exposure of Bifidobacterium cells to oxygen causes accumulation of reactive oxygen species, mainly hydrogen peroxide, leading to cell death. In this study, we tested the suitability of continuous culture under increasing selective pressure combined with immobilized cell technology for the selection of hydrogen peroxide adapted Bifidobacterium cells. Cells of B. longum NCC2705 were immobilized in gellan-xanthan gum gel beads and used to continuously ferment MRS medium containing increasing concentration of H2O2 from 0 to 130 ppm. 相似文献960.
David Navarro Marie Couturier Gabriela Ghizzi Damasceno da Silva Jean-Guy Berrin Xavier Rouau Marcel Asther Christophe Bignon 《Microbial cell factories》2010,9(1):58