全文获取类型
收费全文 | 397篇 |
免费 | 46篇 |
出版年
2015年 | 7篇 |
2013年 | 8篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2005年 | 4篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1960年 | 4篇 |
1959年 | 10篇 |
1958年 | 22篇 |
1957年 | 19篇 |
1956年 | 19篇 |
1955年 | 16篇 |
1954年 | 17篇 |
1953年 | 15篇 |
1952年 | 14篇 |
1951年 | 11篇 |
1950年 | 11篇 |
1949年 | 9篇 |
1948年 | 8篇 |
排序方式: 共有443条查询结果,搜索用时 31 毫秒
61.
62.
SUMMARY: Forty-six strains of Acetobacter , representing twenty species, have been compared on the basis of their respective abilities to proliferate in two defined inorganic media, in which either glucose or ethanol was the sole source of carbon and energy. Twenty-three strains, representing eleven species, grew in either inorganic medium when glucose was present and nine of these strains, representing five species, could grow also in either inorganic medium when ethanol was present. The remaining twenty-three strains, representing eleven species, failed to grow in either medium with either glucose or ethanol. Three organisms grew better with ethanol than with glucose and three were inhibited by ethanol in the presence of glucose. 相似文献
63.
64.
Character Displacement and Acoustic Insects 总被引:2,自引:0,他引:2
Crickets, katydids, grasshoppers, and cicadas should be idealfor illustrating character displacement. Their species-specificcalling songs are of direct importance to reproductive success,and species with similar songs and overlapping ranges shoulddevelop greater differences in their songs in areas of sympatry.Although many pairs of species have suitably similar songs andoverlapping ranges and the data concerning songs are extensivefor crickets and katydids, no convincing example of characterdisplacement has been found in acoustic insects. Lack of suchexamples can be attributed to false premises, to divergencecompleted in allopatry. to elimination of geographical variationin song by gene flow between the zone of sympatry and the zonesof allopatry, and to the scanty sample that has been intensivelystudied. 相似文献
65.
66.
67.
VLJ Whitehall TD Dumenil DM McKeone CE Bond ML Bettington RL Buttenshaw L Bowdler GW Montgomery LF Wockner BA Leggett 《Epigenetics》2014,9(11):1454-1460
The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features. 相似文献
68.
69.
70.