全文获取类型
收费全文 | 287篇 |
免费 | 16篇 |
国内免费 | 1篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 8篇 |
2012年 | 20篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 17篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 21篇 |
2003年 | 13篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有304条查询结果,搜索用时 864 毫秒
61.
Phototransformation of PR to PFR in a 1,0007,000 x gpelletable fraction (17 KP), which was extracted fromdark-grown pea shoots that had been irradiated by red then far-redlight, was studied by low temperature spectrophotometry. Redlight irradiation of PR in 17 KP at 160°Cinduced an absorption increase at 695696 nm with a concomitant,small decrease of PR absorption at 670 nm. These changes werepartially photoreversed when the sample was irradiated subsequentlywith 700-nm light. At 55°C, red light irradiationof PR resulted mainly in bleaching and consequently in a reductionof the PR peak, accompanied by minor absorbance increases around695 nm. The intermediates formed at 165°C by 660-nmlight irradiation partly reverted back to PR or formed a bleachedintermediate (probably the same bleached intermediate describedabove) in the dark, when the pellets were warmed to 60°C.The bleached intermediate was transformed to PFR in the darkat 10°C or above. These characteristics of PR transformation observed in the pelletablephytochrome were essentially the same as those observed in invivo or soluble phytochrome. (Received December 24, 1982; Accepted July 28, 1983) 相似文献
62.
Prem P. Batra Katsushi Sasa Takuya Ueki Kunio Takeda 《Journal of Protein Chemistry》1989,8(2):221-229
By simulation of the circular dichroic spectra (Greenfield and Fasman (1969)) and using reference spectra of Chen et al. (1974), native ovalbumin was estimated to contain 33% -helix, 5% -structure, and 62% random coil. Ovalbumin resisted conformational changes in solutions of urea and of SDS. However, guanidine induced transition, starting at about 2 M and completing at about 4.5 M. At concentrations exceeding 4.5 M guanidine, ovalbumin existed as 6–7% -helical, 12–13% -structure, and 80–81% random coil. Ovalbumin after denaturation in 6 M guanidine or in 8 M urea (incubated at 4°C for 24 hr) did not recover the native conformation but acquired a new conformation in each case, with a somewhat destabilized helical structure.Abbreviation used CD
circular dichroism
- SDS
sodium dodecyl sulfate 相似文献
63.
64.
Asakawa C Ogawa M Fujinaga M Kumata K Xie L Yamasaki T Yui J Fukumura T Zhang MR 《Bioorganic & medicinal chemistry letters》2012,22(11):3594-3597
N-(2-{3-[3,5-Bis(trifluoromethyl)]phenylureido}ethyl)glycyrrhetinamide (2), an ureido-substituted derivative of glycyrrhetinic acid (1), has been reported to display potent inhibitory activity for proteasome and kinase, which are overexpressed in tumors. In this study, we labeled this unsymmetrical urea 2 using [(11)C]phosgene ([(11)C]COCl(2)) as a labeling agent with the expectation that [(11)C]2 could become a positron emission tomography ligand for the imaging of proteasome and kinase in tumors. The strategy for the radiosynthesis of [(11)C]2 was to react hydrochloride of 3,5-bis(trifluoromethyl)aniline (4·HCl) with [(11)C]COCl(2) to possibly give isocyanate [(11)C]6, followed by the reaction of [(11)C]6 with N-(2-aminoethyl)glycyrrhetinamide (3). 相似文献
65.
Rapid evolution of major histocompatibility complex class I genes in primates generates new disease alleles in humans via hitchhiking diversity 总被引:6,自引:0,他引:6 下载免费PDF全文
Shiina T Ota M Shimizu S Katsuyama Y Hashimoto N Takasu M Anzai T Kulski JK Kikkawa E Naruse T Kimura N Yanagiya K Watanabe A Hosomichi K Kohara S Iwamoto C Umehara Y Meyer A Wanner V Sano K Macquin C Ikeo K Tokunaga K Gojobori T Inoko H Bahram S 《Genetics》2006,173(3):1555-1570
A plausible explanation for many MHC-linked diseases is lacking. Sequencing of the MHC class I region (coding units or full contigs) in several human and nonhuman primate haplotypes allowed an analysis of single nucleotide variations (SNV) across this entire segment. This diversity was not evenly distributed. It was rather concentrated within two gene-rich clusters. These were each centered, but importantly not limited to, the antigen-presenting HLA-A and HLA-B/-C loci. Rapid evolution of MHC-I alleles, as evidenced by an unusually high number of haplotype-specific (hs) and hypervariable (hv) (which could not be traced to a single species or haplotype) SNVs within the classical MHC-I, seems to have not only hitchhiked alleles within nearby genes, but also hitchhiked deleterious mutations in these same unrelated loci. The overrepresentation of a fraction of these hvSNV (hv1SNV) along with hsSNV, as compared to those that appear to have been maintained throughout primate evolution (trans-species diversity; tsSNV; included within hv2SNV) tends to establish that the majority of the MHC polymorphism is de novo (species specific). This is most likely reminiscent of the fact that these hsSNV and hv1SNV have been selected in adaptation to the constantly evolving microbial antigenic repertoire. 相似文献
66.
Ohashi J Naka I Tokunaga K Inaoka T Ataka Y Nakazawa M Matsumura Y Ohtsuka R 《American journal of physical anthropology》2006,130(4):551-556
Archaeological, linguistic, and genetic studies show that Austronesian (AN)-speaking Polynesian ancestors came from Asia/Taiwan to the Bismarck Archipelago in Near Oceania more than 3,600 years ago, and then expanded into Remote Oceania. However, it remains unclear whether they extensively mixed with indigenous Melanesians who had populated the Bismarck Archipelago before their arrival. To examine the extent of admixture between Polynesian ancestors and indigenous Melanesians, mitochondrial DNA (mtDNA) variations in the D-loop region and the cytochrome oxidase and lysine transfer RNA (COII/tRNA(Lys)) intergenic 9-bp deletion were analyzed in the following three Oceanian populations: 1) Balopa Islanders as AN-speaking Melanesians living in the northwestern end of the Bismarck Archipelago, 2) Tongans as AN-speaking Polynesians, and 3) Gidra as non-Austronesian-speaking Melanesians in the southwestern lowlands of Papua New Guinea. Phylogenetic analysis of mtDNA sequences revealed that more than 60% of mtDNA sequences in the Balopa Islanders were very similar to those in Tongans, suggesting an extensive gene flow from Polynesian ancestors to indigenous Melanesians. Furthermore, analysis of pairwise difference distributions for the D-loop sequences with the 9-bp deletion and the Polynesian motif (i.e., T16217C, A16247G, and C16261T) suggested that the expansion of Polynesian ancestors possessing these variations occurred approximately 7,000 years ago. 相似文献
67.
2-Deoxy-D-ribose inhibits hypoxia-induced apoptosis by suppressing the phosphorylation of p38 MAPK 总被引:4,自引:0,他引:4
Ikeda R Che XF Ushiyama M Yamaguchi T Okumura H Nakajima Y Takeda Y Shibayama Y Furukawa T Yamamoto M Haraguchi M Sumizawa T Yamada K Akiyama S 《Biochemical and biophysical research communications》2006,342(1):280-285
An angiogenic factor, platelet-derived endothelial cell growth factor/thymidine phosphorylase (TP), stimulates the chemotaxis of endothelial cells and confers resistance to apoptosis induced by hypoxia. 2-Deoxy-d-ribose, a degradation product of thymidine generated by TP enzymatic activity, partially prevented hypoxia-induced apoptosis. 2-Deoxy-d-ribose inhibited hypoxia-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK) but not c-jun NH(2)-terminal kinase/stress-activated protein kinase in human leukemia HL-60 cells. 2-Deoxy-d-ribose also suppressed the levels of Bax attached to mitochondria under hypoxic conditions. SB203580, a specific inhibitor of the p38 MAPK, suppressed the hypoxia-induced apoptosis of HL-60 cells. These findings suggest that one of the molecular bases for resistance to hypoxia-induced apoptosis conferred by 2-deoxy-d-ribose is the inhibition of the p38 signaling pathway. The expression levels of TP are elevated in many malignant solid tumors and thus the 2-deoxy-d-ribose generated by TP in these tumors may play an important role in tumor progression by preventing hypoxia-induced apoptosis. 相似文献
68.
Kazuhiko Yanamoto Katsushi Kumata Tomoteru Yamasaki Chika Odawara Kazunori Kawamura Joji Yui Akiko Hatori Kazutoshi Suzuki Ming-Rong Zhang 《Bioorganic & medicinal chemistry letters》2009,19(6):1707-1710
[18F]FEAC ([18F]4a) and [18F]FEDAC ([18F]4b) were developed as two novel positron emission tomography (PET) ligands for peripheral-type benzodiazepine receptor (PBR). [18F]4a and [18F]4b were synthesized by fluoroethylation of precursors 8a and 8b with [18F]FCH2CH2Br ([18F]9), respectively. Small-animal PET scan for a neuroinflammatory rat model showed that the two radioligands had high uptakes of radioactivity in the kainic acid-infused striatum, a brain region where PBR density was increased. 相似文献
69.
Long-lasting RNAi activity in mammalian neurons 总被引:11,自引:0,他引:11
The effect of RNA interference (RNAi) induced by synthetic small interfering RNAs (siRNAs) on proliferating mammalian cells appears to last for approximately 3-7 days after its induction. Here we show that the RNAi activity induced by a synthetic 21-nucleotide siRNA duplex in postmitotic neurons, mouse primary hippocampal neurons and neurons that differentiated from mouse embryonal carcinoma P19 cells persists for at least 3 weeks, suggesting long-lasting RNAi activity in mammalian neurons. In addition, we also show that an apoptotic (or antiviral) pathway triggered by long dsRNAs is generated during neuronal differentiation of P19 cells, by which the sequence-specific RNAi activity involving long dsRNA appears to be masked. 相似文献
70.
Bannai M Higuchi K Akesaka T Furukawa M Yamaoka M Sato K Tokunaga K 《Analytical biochemistry》2004,327(2):215-221
Whole-genome amplification (WGA) methods were adopted for single-nucleotide-polymorphism (SNP) typing to minimize the amount of genomic DNA that has to be used in typing for thousands of different SNPs in large-scale studies; 5-10 ng of genomic DNA was amplified by a WGA method (improved primer-extension-preamplification-polymerase chain reaction (I-PEP-PCR), degenerated oligonucleotide primer-PCR (DOP-PCR), or multiple displacement amplification (MDA)). Using 1/100 to 1/500 amounts of the whole-genome-amplified products as templates, subsequent analyses were successfully performed. SNPs were genotyped by the sequence-specific primer (SSP)-PCR method followed by fluorescence correlation spectroscopy (FCS). The typing results were evaluated for four different SNPs on tumor necrosis factor receptor 1 and 2 genes (TNFR1 and TNFR2). The genotypes determined by the SSP-FCS method using the WGA products were 100% in concordance with those determined by nucleotide sequencing using genomic DNAs. We have already carried out typing of more than 300 different SNPs and are currently performing 7,500-10,000 typings per day using WGA samples from patients with several common diseases. WGA coupled with FCS allows specific and high-throughput genotyping of thousands of samples for thousands of different SNPs. 相似文献