全文获取类型
收费全文 | 10653篇 |
免费 | 1334篇 |
国内免费 | 4115篇 |
出版年
2024年 | 66篇 |
2023年 | 257篇 |
2022年 | 435篇 |
2021年 | 644篇 |
2020年 | 541篇 |
2019年 | 614篇 |
2018年 | 494篇 |
2017年 | 476篇 |
2016年 | 530篇 |
2015年 | 721篇 |
2014年 | 893篇 |
2013年 | 865篇 |
2012年 | 1155篇 |
2011年 | 1088篇 |
2010年 | 796篇 |
2009年 | 804篇 |
2008年 | 851篇 |
2007年 | 730篇 |
2006年 | 694篇 |
2005年 | 627篇 |
2004年 | 526篇 |
2003年 | 454篇 |
2002年 | 418篇 |
2001年 | 301篇 |
2000年 | 286篇 |
1999年 | 199篇 |
1998年 | 119篇 |
1997年 | 60篇 |
1996年 | 70篇 |
1995年 | 59篇 |
1994年 | 49篇 |
1993年 | 31篇 |
1992年 | 43篇 |
1991年 | 33篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1950年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
4.
5.
6.
7.
8.
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
9.
Abstract All ants (Hymenoptera, Formicidae) are highly eusocial insects that are characterized by reproductive division of labor with sterile castes (worker and soldier) helping fertile castes (queen and male) to reproduce.
Ant societies, like other complex animal societies, have developed a sophisticated communication system, in which recognition behaviors are frequently involved Recognition abilities allow individuals to orient and modulate their behaviors effectively and appropriately in response to the characteristics andlor signals expressed by other organisms. Among recognition behaviors, nestmate recognition and kin recognition mechanisms have attracted great attention of sociobiologists, ecologists, insect physiologists and biochemists since 1970's. This is parallel with the popularization of Hamilton's kin selection theory. The present paper aims at reviewing the current understanding on nestmate/kin recognition in ants. This review consists of three parts. The first part concerns the diversity of recognition behaviors and their ecological implications with emphasis on nestmatelkin recognition; in the second part, the current understandings on the mechanism of nestmatelkin recognition are outlined; and in the third part, we discuss the ontogenetic development of nestmate recognition behavior and naturally mixed colonies. The study of the integration mechanism of social parasite may provide heuristic clues to the understanding of kin/nestmate recognition system. 相似文献
Ant societies, like other complex animal societies, have developed a sophisticated communication system, in which recognition behaviors are frequently involved Recognition abilities allow individuals to orient and modulate their behaviors effectively and appropriately in response to the characteristics andlor signals expressed by other organisms. Among recognition behaviors, nestmate recognition and kin recognition mechanisms have attracted great attention of sociobiologists, ecologists, insect physiologists and biochemists since 1970's. This is parallel with the popularization of Hamilton's kin selection theory. The present paper aims at reviewing the current understanding on nestmate/kin recognition in ants. This review consists of three parts. The first part concerns the diversity of recognition behaviors and their ecological implications with emphasis on nestmatelkin recognition; in the second part, the current understandings on the mechanism of nestmatelkin recognition are outlined; and in the third part, we discuss the ontogenetic development of nestmate recognition behavior and naturally mixed colonies. The study of the integration mechanism of social parasite may provide heuristic clues to the understanding of kin/nestmate recognition system. 相似文献
10.