全文获取类型
收费全文 | 313篇 |
免费 | 45篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 9篇 |
2012年 | 10篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 4篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2002年 | 4篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 14篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有358条查询结果,搜索用时 31 毫秒
51.
Helge Bruns Marius Petrulionis Daniel Schultze Mohammed Al Saeedi Shibo Lin Kenya Yamanaka Marius Ambrazevičius Kęstutis Strupas Peter Schemmer 《Amino acids》2014,46(4):969-976
Hepatocellular carcinoma (HCC) is a highly vascularized tumor with limited susceptibility to chemotherapy. Modern targeted therapies are aimed at specific properties of this neoplasm. Glycine is a simple non-essential amino acid with potential antiangiogenic effects. In this study, the amino acid’s effect on angiogenic signaling in an in vitro model of HCC was evaluated. HepG2 and Huh7 cells were treated with glycine-free DMEM supplemented with 0, 0.01, 0.1, 1.0, 2.0, 5.0 and 10 mM glycine. The direct effects of glycine on the viability of HCC cells were monitored using MTT assay. To detect angiogenic signaling, mRNA and protein levels of vascular endothelial growth factor (VEGF-A) were measured using RT-PCR and Western Blot assays. To determine whether or not glycine receptors (GlyR) played a significant role, the specific antagonist, strychnine, was used as a direct inhibitor. Western Blotting was performed to show the presence of GlyR. While there was no direct pro- or antiproliferative effect of either glycine or strychnine in both cell lines, glycine was shown to significantly decrease VEGF-A expression on mRNA and protein level up to 63 % in both cell lines. This effect was blunted by the presence of strychnine. GlyR was also identified in both cell lines. Glycine decreases GlyR-dependent, VEGF-A-mediated, angiogenic signaling in human HCC and thus might be a promising additive to chemotherapy treatment strategies for highly vascularized tumors. 相似文献
52.
53.
54.
Apotheker Wilhelm Schultze 《Zoomorphology》1937,32(3):463-491
Ohne ZusammenfassungDie Arbeit wurde von der Philos. Fakultät Greifswald als Dissertation angenommen. 相似文献
55.
L. Schultze Jena 《Ethnos》2013,78(3-4):120-123
Field materials from North Bali are presented to question conventional anthropological conceptions of culture and common practices in its analysis. The author argues that there is a need for anthropology to reshape Us assumptions, particularly in response to recent reßexive and deconstructionist critiques. A revised set of assumptions is presented with regard to cultural meanings, sharing, positioning and function; and its fruitfulness in the analysis of cultural reproduction in Bali is explored. 相似文献
56.
57.
Rhizobium nodM and nodN genes are common nod genes: nodM encodes functions for efficiency of nod signal production and bacteroid maturation.
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
N Baev M Schultze I Barlier D C Ha H Virelizier E Kondorosi A Kondorosi 《Journal of bacteriology》1992,174(23):7555-7565
Earlier, we showed that Rhizobium meliloti nodM codes for glucosamine synthase and that nodM and nodN mutants produce strongly reduced root hair deformation activity and display delayed nodulation of Medicago sativa (Baev et al., Mol. Gen. Genet. 228:113-124, 1991). Here, we demonstrate that nodM and nodN genes from Rhizobium leguminosarum biovar viciae restore the root hair deformation activity of exudates of the corresponding R. meliloti mutant strains. Partial restoration of the nodulation phenotypes of these two strains was also observed. In nodulation assays, galactosamine and N-acetylglucosamine could substitute for glucosamine in the suppression of the R. meliloti nodM mutation, although N-acetylglucosamine was less efficient. We observed that in nodules induced by nodM mutants, the bacteroids did not show complete development or were deteriorated, resulting in decreased nitrogen fixation and, consequently, lower dry weights of the plants. This mutant phenotype could also be suppressed by exogenously supplied glucosamine, N-acetylglucosamine, and galactosamine and to a lesser extent by glucosamine-6-phosphate, indicating that the nodM mutant bacteroids are limited for glucosamine. In addition, by using derivatives of the wild type and a nodM mutant in which the nod genes are expressed at a high constitutive level, it was shown that the nodM mutant produces significantly fewer Nod factors than the wild-type strain but that their chemical structures are unchanged. However, the relative amounts of analogs of the cognate Nod signals were elevated, and this may explain the observed host range effects of the nodM mutation. Our data indicate that both the nodM and nodN genes of the two species have common functions and confirm that NodM is a glucosamine synthase with the biochemical role of providing sufficient amounts of the sugar moiety for the synthesis of the glucosamine oligosaccharide signal molecules. 相似文献
58.
Chimpanzee fetal G gamma and A gamma globin gene nucleotide sequences provide further evidence of gene conversions in hominine evolution 总被引:5,自引:0,他引:5
The fetal globin genes G gamma and A gamma from one chromosome of a
chimpanzee (Pan troglodytes) were sequenced and found to be closely similar
to the corresponding genes of man and the gorilla. These genes contain
identical promoter and termination signals and have exons 1 and 2 separated
by the conserved short intron 1 (122 bp) and exons 2 and 3 separated by the
more rapidly evolving, larger intron 2 (893 bp and 887 bp in chimpanzee G
gamma and A gamma, respectively). Each intron 2 has a stretch of simple
sequence DNA (TG)n serving possibly as a "hot spot" for recombination. The
two chimpanzee genes encode polypeptide chains that differ only at position
136 (glycine in G gamma and alanine in A gamma) and that are identical to
the corresponding human chains, which have aspartic acid at position 73 and
lysine at 104 in contrast to glycine and arginine at these respective
positions of the gorilla A gamma chain. Phylogenetic analysis by the
parsimony method revealed four silent (synonymous) base substitutions in
evolutionary descent of the chimpanzee G gamma and A gamma codons and none
in the human and gorilla codons. These Homininae (Pan, Homo, Gorilla)
coding sequences evolved at one-tenth the average mammalian rate for
nonsynonymous and one-fourth that for synonymous substitutions. Three
sequence regions that were affected by gene conversions between chimpanzee
G gamma and A gamma loci were identified: one extended 3' of the hot spot
with G gamma replaced by the A gamma sequence, another extended 5' of the
hot spot with A gamma replaced by G gamma, and the third conversion
extended from the 5' flanking to the 5' end of intron 2, with G gamma
replaced here by the A gamma sequence. A conversion similar to this third
one has occurred independently in the descent of the gorilla genes. The
four previously identified conversions, labeled C1-C4 (Scott et al. 1984),
were substantiated with the addition of the chimpanzee genes to our
analysis (C1 being shared by all three hominines and C2, C3, and C4 being
found only in humans). Thus, the fetal genes from all three of these
hominine species have been active in gene conversions during the descent of
each species.
相似文献
59.
60.
Two distinct conformational states define the interaction of human RAD51‐ATP with single‐stranded DNA
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Andrea Candelli Edwige B Garcin Mauro Modesti Luca Pellegrini Gijs JL Wuite Erwin JG Peterman 《The EMBO journal》2018,37(7)
An essential mechanism for repairing DNA double‐strand breaks is homologous recombination (HR). One of its core catalysts is human RAD51 (hRAD51), which assembles as a helical nucleoprotein filament on single‐stranded DNA, promoting DNA‐strand exchange. Here, we study the interaction of hRAD51 with single‐stranded DNA using a single‐molecule approach. We show that ATP‐bound hRAD51 filaments can exist in two different states with different contour lengths and with a free‐energy difference of ~4 kBT per hRAD51 monomer. Upon ATP hydrolysis, the filaments convert into a disassembly‐competent ADP‐bound configuration. In agreement with the single‐molecule analysis, we demonstrate the presence of two distinct protomer interfaces in the crystal structure of a hRAD51‐ATP filament, providing a structural basis for the two conformational states of the filament. Together, our findings provide evidence that hRAD51‐ATP filaments can exist in two interconvertible conformational states, which might be functionally relevant for DNA homology recognition and strand exchange. 相似文献