全文获取类型
收费全文 | 503868篇 |
免费 | 47443篇 |
国内免费 | 1173篇 |
专业分类
552484篇 |
出版年
2018年 | 14262篇 |
2017年 | 13010篇 |
2016年 | 11204篇 |
2015年 | 6495篇 |
2014年 | 7208篇 |
2013年 | 10256篇 |
2012年 | 15591篇 |
2011年 | 23871篇 |
2010年 | 18988篇 |
2009年 | 14770篇 |
2008年 | 19497篇 |
2007年 | 21454篇 |
2006年 | 10496篇 |
2005年 | 10313篇 |
2004年 | 10602篇 |
2003年 | 10140篇 |
2002年 | 9903篇 |
2001年 | 18938篇 |
2000年 | 19462篇 |
1999年 | 15199篇 |
1998年 | 5116篇 |
1997年 | 5308篇 |
1996年 | 4990篇 |
1995年 | 4767篇 |
1994年 | 4687篇 |
1993年 | 4711篇 |
1992年 | 12207篇 |
1991年 | 11797篇 |
1990年 | 11429篇 |
1989年 | 11078篇 |
1988年 | 10475篇 |
1987年 | 9993篇 |
1986年 | 9472篇 |
1985年 | 9585篇 |
1984年 | 7943篇 |
1983年 | 6867篇 |
1982年 | 5493篇 |
1981年 | 5109篇 |
1980年 | 4618篇 |
1979年 | 7727篇 |
1978年 | 6236篇 |
1977年 | 5738篇 |
1976年 | 5401篇 |
1975年 | 6071篇 |
1974年 | 6693篇 |
1973年 | 6630篇 |
1972年 | 6359篇 |
1971年 | 5819篇 |
1970年 | 4798篇 |
1969年 | 4753篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies
by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related
cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published
work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord.
Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement
by non-notochordal cells. 相似文献
992.
993.
994.
Phagocytosis of microspheres in V79 Chinese hamster lung cells was investigated by flow cytometry. Fluorescent microspheres (1.8 micron diameter) were used as the ingesta. Change in the number of V79 cells containing fluorescent microspheres was measured as an index of phagocytic activity. With time there was a sigmoidal increase in cells containing microspheres. The phagocytosis of microspheres is partially explained by two parameters introduced to describe the sigmoidal curves. 相似文献
995.
996.
The role of introns in evolution 总被引:6,自引:0,他引:6
J H Rogers 《FEBS letters》1990,268(2):339-343
What are the roles of 'classical' introns in the evolution of nuclear genes, and what was the origin of these introns? Exon shuffling has been important in the evolution of cell surface and extracellular proteins, but the evidence for it in respect of intracellular proteins is weak. Intron distributions imply that some introns have been removed while others have been inserted in the course of evolution: ancestral patterns of introns may thus have been obscured. Recent evidence on the self-splicing and reverse-splicing abilities of Group II introns supports the hypothesis that these could have been the ancestors of classical introns. 相似文献
997.
998.
999.
Kevin B. Potts 《Journal of Mammalian Evolution》2010,17(3):221-222
1000.
Frank H. Gleason Steve K. Schmidt Agostina V. Marano 《Extremophiles : life under extreme conditions》2010,14(5):417-425
Zoosporic true fungi are thought to be ubiquitous in many ecosystems, especially in cool, moist soils and freshwater habitats
which are rich in organic matter. However, some of the habitats where these fungi are found may periodically experience extreme
conditions, such as soils in extremely dry, hot and cold climates, acidic and alkaline soils, polluted rivers, anaerobic soil
and water, saline soil and water, periglacial soils, oligotrophic soils, tree canopies and hydrothermal vents. It is clear
that many ecotypes of zoosporic true fungi have indeed adapted to extreme or stressful environmental conditions. This conclusion
is supported by studies in both the field and in the laboratory. Therefore, in our opinion, at least some true zoosporic fungi
can be considered to be extremophiles. 相似文献