全文获取类型
收费全文 | 194篇 |
免费 | 15篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2019年 | 3篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 11篇 |
2005年 | 3篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有209条查询结果,搜索用时 20 毫秒
1.
D W Frederiksen 《Biochemistry》1979,18(9):1651-1656
Porcine aortic myosin is a smooth muscle contractile protein similar to its striated muscle counterpart. Electrophoresis in sodium dodecyl sulfate indicates that the molecule consists of three classes of subunits with polypeptide chain molecular weights of 192,000, 19,000, and 15,000. At 277 nm the absorption spectrum gives an extinction coefficient for aortic myosin of 0.558 cm2/mg; the circular dichroism spectrum of the protein indicates that aortic myosin contains about 70% of its residues in the alpha-helical configuration. Amino acid analysis shows that the smooth muscle myosin has significantly more arginine and leucine and significantly less valine and isoleucine than rabbit skeletal muscle myosin. Other studies yielded these data: Vapp = 0.716 mL/g [eta] = 0.213 mL/mg, S20, w = 5.84 x 10(-13)S. Similar studies with rabbit skeletal muscle myosin indicate that Vapp = 0.711 mL/g and S20, w = 6.36 x 10(-13)S. These properties suggest that aortic myosin, like skeletal muscle myosin, behaves hydrodynamically like a rigid rod. 相似文献
2.
3.
Signe Frederiksen 《Nordic Journal of Botany》1994,14(1):3-6
Hybrid plants were obtained in an intergeneric cross between Taenìatherum caputmedusae (2n = 2x = 14) and Triticum aestívum (2n = 6x = 42). The chromosome number was as expected 2n = 28. Morphologically the offspring looked like Triticum aestívum . Analysis of meiotic metaphase I showed an unexpected high number of bi- and trivalents which is ascribed to homoeologous pairing of chromosomes from T. aestivum . It is concluded that the genome of Taeniatherum has effects on the pairing regulation system present in T. aestívum . 相似文献
4.
Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans 总被引:2,自引:0,他引:2
Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and
D. simulans for two common allozyme forms, as well as for several other
less common variants. Parallel latitudinal clines in the frequencies of the
common EST6-F and EST6-S allozymes in these species have previously been
interpreted in terms of a shared amino acid polymorphism that distinguishes
the two variants and is subject to selection. Here we compare the sequences
of four D. simulans Est-6 isolates and show that overall estimates of
nucleotide heterozygosity in both coding and 5' flanking regions are more
than threefold higher than those obtained previously for this gene in D.
melanogaster. Nevertheless, the ratio of replacement to exon silent-site
polymorphism in D. simulans is less than the ratio of replacement to silent
divergence between D. simulans and D. melanogaster, which could be the
result of increased efficiency of selection against replacement
polymorphisms in D. simulans or to divergent selection between the two
species. We also find that the amino acid polymorphisms separating EST6- F
and EST6-S in D. simulans are not the same as those that separate these
allozymes in D. melanogaster, implying that the shared clines do not
reflect shared molecular targets for selection. All comparisons within and
between the two species reveal a remarkable paucity of variation in a
stretch of nearly 400 bp immediately 5' of the gene, indicative of strong
selective constraint to retain essential aspects of Est-6 promoter
function.
相似文献
5.
DNA markers for downy mildew resistance genes in sorghum. 总被引:1,自引:0,他引:1
The random amplified polymorphic DNA technique was used to find markers for a downy mildew resistance gene in sorghum. Of the 674 random primers screened for polymorphism, 2 amplified fragments were linked to a downy mildew resistance gene in sorghum line SC414. Utilization of an existing restriction fragment length polymorphism mapping population (IS3620C x BTx623) also revealed two markers that are linked to a different resistance gene in another sorghum line, BTx623. 相似文献
6.
Summary We have tested the acyl-transferase of penicillin producing strains and penicillin-less mutants of Penicillium chrysogenum for their ability to exchange the d--aminoadipic acid side chain of cephalosporin-C with phenoxyacetic acid. We found the reaction in both types of strains. 相似文献
7.
Abstract. Woody vegetation was studied in 44 sites in Senegal. Species composition and density were analysed with TWINSPAN and Canonical Correspondence Analysis; 16 vegetation types were defined. A supervised, multispectral and multitemporal classification of day and night, dry season NOAA-AVHRR imagery was used to identify their distribution with a classification accuracy ranging from 60–100%. 相似文献
8.
Synthesis of low molecular weight RNA components A, C and D by polymerase II in alpha-amanitin-resistant hamster cells. 总被引:17,自引:7,他引:10 下载免费PDF全文
In an attempt to establish which RNA polymerase catalyzes the synthesis of the low molecular weight RNA components A, C and D, Ama 1 cells (mutant Chinese hamster cells) were used in experiments with addition of alpha-amanitin. Ama 1 cells contain an altered RNA polymerase II which is 800 times more resistant towards inhibition by alpha-amanitin than the wild type enzyme. Alpha-amanitin (up to 200 microgram/ml) added to these cells does not affect the synthesis of the low molecular weight RNAs A, C and D. These data together with our previous data showing that alpha-amanitin (0.5 - 5.0 microgram/ml) preferentially inhibits the synthesis of A, C and D in normal cells indicate that RNA polymerase II catalyzes the synthesis of the low molecular weight RNA components A, C and D. 相似文献
9.
Morten Frederiksen Tycho Anker‐Nilssen Grégory Beaugrand Sarah Wanless 《Global Change Biology》2013,19(2):364-372
The boreal Northeast Atlantic is strongly affected by current climate change, and large shifts in abundance and distribution of many organisms have been observed, including the dominant copepod Calanus finmarchicus, which supports the grazing food web and thus many fish populations. At the same time, large‐scale declines have been observed in many piscivorous seabirds, which depend on abundant small pelagic fish. Here, we combine predictions from a niche model of C. finmarchicus with long‐term data on seabird breeding success to link trophic levels. The niche model shows that environmental suitability for C. finmarchicus has declined in southern areas with large breeding seabird populations (e.g. the North Sea), and predicts that this decline is likely to spread northwards during the 21st century to affect populations in Iceland and the Faroes. In a North Sea colony, breeding success of three common piscivorous seabird species [black‐legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge) and Atlantic puffin (Fratercula arctica)] was strongly positively correlated with local environmental suitability for C. finmarchicus, whereas this was not the case at a more northerly colony in west Norway. Large seabird populations seem only to occur where C. finmarchicus is abundant, and northward distributional shifts of common boreal seabirds are therefore expected over the coming decades. Whether or not population size can be maintained depends on the dispersal ability and inclination of these colonial breeders, and on the carrying capacity of more northerly areas in a warmer climate. 相似文献
10.
Jannie Fries Linnebjerg Jér?me Fort Tim Guilford Anna Reuleaux Anders Mosbech Morten Frederiksen 《PloS one》2013,8(8)
When species competing for the same resources coexist, some segregation in the way they utilize those resources is expected. However, little is known about how closely related sympatric breeding species segregate outside the breeding season. We investigated the annual segregation of three closely related seabirds (razorbill
Alca
torda
, common guillemot
Uria
aalge
and Brünnich’s guillemot
U
. lomvia
) breeding at the same colony in Southwest Greenland. By combining GPS and geolocation (GLS) tracking with dive depth and stable isotope analyses, we compared spatial and dietary resource partitioning. During the breeding season, we found the three species to segregate in diet and/or dive depth, but less in foraging area. During both the post-breeding and pre-breeding periods, the three species had an increased overlap in diet, but were dispersed over a larger spatial scale. Dive depths were similar across the annual cycle, suggesting morphological adaptations fixed by evolution. Prey choice, on the other hand, seemed much more flexible and therefore more likely to be affected by the immediate presence of potential competitors. 相似文献