全文获取类型
收费全文 | 13753篇 |
免费 | 1374篇 |
国内免费 | 2057篇 |
专业分类
17184篇 |
出版年
2024年 | 69篇 |
2023年 | 278篇 |
2022年 | 560篇 |
2021年 | 793篇 |
2020年 | 605篇 |
2019年 | 797篇 |
2018年 | 645篇 |
2017年 | 516篇 |
2016年 | 721篇 |
2015年 | 952篇 |
2014年 | 1108篇 |
2013年 | 1143篇 |
2012年 | 1347篇 |
2011年 | 1206篇 |
2010年 | 758篇 |
2009年 | 698篇 |
2008年 | 761篇 |
2007年 | 630篇 |
2006年 | 594篇 |
2005年 | 440篇 |
2004年 | 473篇 |
2003年 | 410篇 |
2002年 | 334篇 |
2001年 | 237篇 |
2000年 | 191篇 |
1999年 | 155篇 |
1998年 | 114篇 |
1997年 | 79篇 |
1996年 | 110篇 |
1995年 | 83篇 |
1994年 | 66篇 |
1993年 | 36篇 |
1992年 | 55篇 |
1991年 | 42篇 |
1990年 | 40篇 |
1989年 | 27篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 20篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Yang Su-Rong Sun Huan-Xin Hu Zhen-Zhen Wang Si-Heng Sun Hui Xue Yin-Jia Ye Chen-Bo 《Sleep and biological rhythms》2017,15(1):57-65
Sleep and Biological Rhythms - Chronic sleep deprivation (SD) is an overwhelming problem in young students. Firstly, we investigated whether different levels of pre-training SD had effects on... 相似文献
3.
To clarify the mechanisms of Nosema ceranae parasitism, we deep-sequenced both honey bee host and parasite mRNAs throughout a complete 6-day infection cycle. By time-series analysis, 1122 parasite genes were significantly differently expressed during the reproduction cycle, clustering into 4 expression patterns. We found reactive mitochondrial oxygen species modulator 1 of the host to be significantly down regulated during the entire infection period. Our data support the hypothesis that apoptosis of honey bee cells was suppressed during infection. We further analyzed genome-wide genetic diversity of this parasite by comparing samples collected from the same site in 2007 and 2013. The number of SNP positions per gene and the proportion of non-synonymous substitutions per gene were significantly reduced over this time period, suggesting purifying selection on the parasite genome and supporting the hypothesis that a subset of N. ceranae strains might be dominating infection. 相似文献
4.
5.
6.
7.
Genome‐wide detection of CNVs associated with beak deformity in chickens using high‐density 600K SNP arrays 下载免费PDF全文
H. Bai Y. Sun N. Liu Y. Liu F. Xue Y. Li S. Xu A. Ni J. Ye Y. Chen J. Chen 《Animal genetics》2018,49(3):226-236
Beak deformity (crossed beaks) is found in several indigenous chicken breeds including Beijing‐You studied here. Birds with deformed beaks have reduced feed intake and poor production performance. Recently, copy number variation (CNV) has been examined in many species and is recognized as a source of genetic variation, especially for disease phenotypes. In this study, to unravel the genetic mechanisms underlying beak deformity, we performed genome‐wide CNV detection using Affymetrix chicken high‐density 600K data on 48 deformed‐beak and 48 normal birds using penncnv . As a result, two and eight CNV regions (CNVRs) covering 0.32 and 2.45 Mb respectively on autosomes were identified in deformed‐beak and normal birds respectively. Further RT‐qPCR studies validated nine of the 10 CNVRs. The ratios of six CNVRs were significantly different between deformed‐beak and normal birds (P < 0.01). Within these six regions, three and 21 known genes were identified in deformed‐beak and normal birds respectively. Bioinformatics analysis showed that these genes were enriched in six GO terms and one KEGG pathway. Five candidate genes in the CNVRs were further validated using RT‐qPCR. The expression of LRIG2 (leucine rich repeats and immunoglobulin like domains 2) was lower in birds with deformed beaks (P < 0.01). Therefore, the LRIG2 gene could be considered a key factor in view of its known functions and its potential roles in beak deformity. Overall, our results will be helpful for future investigations of the genomic structural variations underlying beak deformity in chickens. 相似文献
8.
Social responsibility links personal behavior with societal expectations and plays a key role in affecting an agent’s emotional state following a decision. However, the neural basis of responsibility attribution remains unclear. In two previous event-related brain potential (ERP) studies we found that personal responsibility modulated outcome evaluation in gambling tasks. Here we conducted a functional magnetic resonance imaging (fMRI) study to identify particular brain regions that mediate responsibility attribution. In a context involving team cooperation, participants completed a task with their teammates and on each trial received feedback about team success and individual success sequentially. We found that brain activity differed between conditions involving team success vs. team failure. Further, different brain regions were associated with reinforcement of behavior by social praise vs. monetary reward. Specifically, right temporoparietal junction (RTPJ) was associated with social pride whereas dorsal striatum and dorsal anterior cingulate cortex (ACC) were related to reinforcement of behaviors leading to personal gain. The present study provides evidence that the RTPJ is an important region for determining whether self-generated behaviors are deserving of praise in a social context. 相似文献
9.
Oat leaf base: tissue with an efficient regeneration capacity 总被引:1,自引:1,他引:0
Summary An efficient short term regeneration system using seedling derived oat (Avena sativa) leaf tissue has been developed. Callus derived from the leaf base showed a higher response of plant regeneration than callus initiated from mesocotyls and more mature parts of the leaves. A correlation between the nuclear DNA content of the donor material, as analysed with flow cytometry, and its ability to form callus was observed. Somatic embryogenesis was histologically recognised from callus derived from tissue close to the apical meristem. Plant regeneration media with various concentrations of auxin were tested. Callus from three different cultivars had a similar regeneration potential with an optimal regeneration frequency of 60%. About 2 months after inoculation regenerated plantlets could be moved to a greenhouse for cultivation.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- DAPI
6-diamidino-2-phenylindole
- IAA
indole-3-acetic acid
- KT
kinetin
- MS
Murashige and Skoog's medium
- NAA
naphthalene acetic acid 相似文献
10.