全文获取类型
收费全文 | 520篇 |
免费 | 42篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 40篇 |
2012年 | 36篇 |
2011年 | 41篇 |
2010年 | 32篇 |
2009年 | 35篇 |
2008年 | 30篇 |
2007年 | 28篇 |
2006年 | 34篇 |
2005年 | 32篇 |
2004年 | 19篇 |
2003年 | 25篇 |
2002年 | 25篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有562条查询结果,搜索用时 62 毫秒
91.
Etsuko Moritsuka Phourin Chhang Shuichiro Tagane Hironori Toyama Heng Sokh Tetsukazu Yahara Hidenori Tachida 《Tree Genetics & Genomes》2017,13(6):115
Dalbergia cochinchinensis Pierre ex Laness. (Fabaceae) is a commercially important tree in Southeast Asia. Although this species is under legal protections, illegal logging and disorderly developments have reduced its populations, and the conservation of this species is currently of much concern. In this study, we determined nucleotide sequences at six chloroplasts and ten nuclear loci in four populations of D. cochinchinensis in Cambodia, followed by population genetic analyses. The average silent nucleotide diversity over the nuclear loci, excluding one with an exceptionally high value, was 0.0057 in the entire population, and the mean F ST across the nuclear loci between each population pair was between 0.135 and 0.467. Thus, the nucleotide diversity in the studied populations was not low compared with that in other tree species, and the level of population differentiation was high. Neutrality test statistics indicated a recent reduction of population size and a subdivision of the population within this species. The divergence times and migration rates were estimated with a likelihood-based method assuming the isolation with migration model. Based on the results, the three populations split 68,000–138,000 years ago, possibly corresponding to the start of the last glacial period, and the level of gene flow among the populations was very low thereafter. Moreover, after the split, population sizes were reduced considerably. Notably, the nucleotide diversity in an insertion sequence in a noncoding region of nuclear C4H was much higher than the mean nucleotide diversity in silent sites across other nuclear genes, indicating that the region was affected by selection. 相似文献
92.
Honda T Tajima H Kaneko Y Ban M Inaba T Takeno Y Okamoto K Aono H 《Bioorganic & medicinal chemistry letters》2008,18(9):2939-2943
We found 4-pyridylmethylthio derivative 1 to be very effective in using antiangiogenesis activity to prevent proliferation of HUVECs (Human Umbilical Vein Endothelial Cells), which was induced by vascular endothelial growth factor (VEGF). Compound 1 was equally effective in inhibiting VEGF receptor2 tyrosine kinase (KDR, IC50 = 26 nM). We deduced that the inhibition was the result of binding the catalytic domain of VEGF receptor2 tyrosine kinase in a similar fashion to both phthalazine derivative PTK787 2 and anthranylamide derivative AAL993 3. In this report, we will describe the conformational analyses, from ab initio MO calculation and X-ray crystallographic analyses, of compound 1 and the analogs, which include non-active 9, all in comparison with 2 and 3. The conformation–activity relationships suggest that a nonbonded intramolecular interaction between the sulfur and the carbonyl oxygen of 1 was very important in inhibiting KDR. 相似文献
93.
We isolated the 5′ flanking region of a gene for phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) from Pinus taeda, PtaPAL. To investigate the tissue-specific expression of the PtaPAL promoter, histochemical assay of GUS activity was performed using the transgenic tobacco expressing the PtaPAL promoter-GUS. The region of −897 to −420 in PtaPAL promoter showed high activities in the secondary xylem and response to bending stress. To characterize the cis-regulatory functions of the promoters for enzymes in phenylpropanoid biosynthesis, we examined the activity of chimeric promoters
of PtaPAL and a 4-coumarate CoA ligase, Pta4CLα. The chimeric promoter showed similar activity as the Pta4CLα promoter. Electrophoretic mobility shift assays implicated −897 to –674 of PtaPAL promoter containing cis-elements of the expression in xylem of Pinus taeda. The results suggested that AC elements of PtaPAL have multiple functions in the expression under the various developmental stages and stress conditions in the transgenic
tobacco.
The nucleotide sequence data reported will appear in the EMBL, GenBank, and DDBJ Nucleotide Sequence Databases under the accession
number AB449103 (PtaPAL promoter sequence). 相似文献
94.
A p-xylene-degrading, sulfate-reducing enrichment culture was characterized by analyzing the response of its members to changes
in the available substrate. The culture was inoculated into media containing other substrates, resulting in the establishment
of benzoate-, acetate-, and lactate-utilizing enrichment cultures. PCR-denaturing gradient gel electrophoresis (DGGE) analysis
of the enriched cultures targeting 16S rRNA genes showed quite simple band patterns. The predominant band from the benzoate-utilizing
enrichment culture was identical to that from the original enrichment culture utilizing p-xylene. A single, dominant DGGE band was observed in common from the acetate- and lactate-utilizing enrichment cultures.
A novel sulfate-reducing bacterium, strain PL12, was isolated from the lactate-utilizing enrichment culture. The 16S rRNA
gene sequence of strain PL12 was identical to that of the dominant DGGE band in the acetate- and lactate-utilizing enrichment
cultures and distinct from the dominant sequences in the original p-xylene-degrading and benzoate-utilizing enrichment cultures. Phylogenetic analysis of the 16S rRNA gene sequences showed
that the isolate belonged to the family Desulfobacteraceae in the class Deltaproteobacteria. The isolated strain PL12 could utilize n-hexane and n-decane as substrates, but could not utilize benzoate, p-xylene and other aromatic hydrocarbons. These results suggest that the p-xylene degradation observed in the original enrichment culture was performed by the dominant bacterium corresponding to DGGE
band pXy-K-13 (Nakagawa et al. 2008). The novel strain PL12 might have been utilizing metabolites of p-xylene. 相似文献
95.
STOP1 Regulates Multiple Genes That Protect Arabidopsis from Proton and Aluminum Toxicities 总被引:1,自引:0,他引:1 下载免费PDF全文
96.
The fibroblast growth factor receptor substrate (FRS)-2 protein family comprises FRS2α, a well-known central mediator for fibroblast growth factor signaling, and FRS2β, whose endogenous expression pattern and function are not yet defined. Immunohistochemical analysis revealed that expression of FRS2β was restricted to neural tissues and it colocalized with Tuj1, a neuronal marker. There are two distinct patterns of FRS2β expression in neural cells: punctate and cup/ring-shaped; moreover, some particles colocalized with lysosomes. Stimulation with brain-derived neurotrophic factor (BDNF) enhanced FRS2β phosphorylation and the cup/ring-shaped pattern. These results suggest a probable role of FRS2β in the intracellular degradation systems of neural cells, which involves lysosomes. 相似文献
97.
Seiji Ueda Sho-ichi Yamagishi Yuriko Matsumoto Yusuke Kaida Ayako Fujimi-Hayashida Kiyomi Koike Hideharu Tanaka Kei Fukami Seiya Okuda 《Life sciences》2009,84(23-24):853-856
AimsAsymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, has been reported to be a novel marker for the progression of chronic kidney disease (CKD). We have recently found that accumulation of ADMA could trigger peritubular capillary loss, thus contributing to tubulointerstitial ischemia and fibrosis in a rat model of CKD. However, effects of ADMA on glomerular capillary loss and sclerosis remain to be elucidated.Main methodsIn this study, we investigated whether lowering of ADMA by overexpression of dimethylarginine dimethylaminohydrolase (DDAH), a main enzyme that degrades ADMA, could ameliorate glomerular capillary loss and sclerosis in a rat model of CKD. Four weeks after 5/6 subtotal nephrectomy (Nx), animals were given tail vein injections with recombinant adenovirus vector encoding DDAH-I (Adv-DDAH) or control vector expressing bacterial β-galactosidase (Adv-LZ), or orally administered with 20 mg/kg/day of hydralazine (Hyz) which served as a blood pressure control model.Key findingsPlasma levels of ADMA were associated with decreased number of glomerular capillaries as well as severity of glomerular sclerosis in Nx-rats. These glomerular changes progressed in Adv-LZ- or Hyz-treated Nx-rats, while they were ameliorated by the treatment with DDAH overexpression.SignificanceOur present data suggest that ADMA may be involved in glomerular capillary loss and sclerosis, thus contributing to the progression of CKD. Substitution of DDAH protein or enhancement of its activity may become a novel therapeutic strategy for the treatment of CKD. 相似文献
98.
Yukio Hirayama Mamiko Yoshimura Yuriko Ozeki Isamu Sugawara Tadashi Udagawa Satoru Mizuno Naoki Itano Koji Kimata Aki Tamaru Hisashi Ogura Kazuo Kobayashi Sohkichi Matsumoto 《PLoS pathogens》2009,5(10)
In spite of the importance of hyaluronan in host protection against infectious organisms in the alveolar spaces, its role in mycobacterial infection is unknown. In a previous study, we found that mycobacteria interact with hyaluronan on lung epithelial cells. Here, we have analyzed the role of hyaluronan after mycobacterial infection was established and found that pathogenic mycobacteria can grow by utilizing hyaluronan as a carbon source. Both mouse and human possess 3 kinds of hyaluronan synthases (HAS), designated HAS1, HAS2, and HAS3. Utilizing individual HAS-transfected cells, we show that HAS1 and HAS3 but not HAS2 support growth of mycobacteria. We found that the major hyaluronan synthase expressed in the lung is HAS1, and that its expression was increased after infection with Mycobacterium tuberculosis. Histochemical analysis demonstrated that hyaluronan profoundly accumulated in the granulomatous legion of the lungs in M. tuberculosis-infected mice and rhesus monkeys that died from tuberculosis. We detected hyaluronidase activity in the lysate of mycobacteria and showed that it was critical for hyaluronan-dependent extracellular growth. Finally, we showed that L-Ascorbic acid 6-hexadecanoate, a hyaluronidase inhibitor, suppressed growth of mycobacteria in vivo. Taken together, our data show that pathogenic mycobacteria exploit an intrinsic host-protective molecule, hyaluronan, to grow in the respiratory tract and demonstrate the potential usefulness of hyaluronidase inhibitors against mycobacterial diseases. 相似文献
99.
Saneyoshi Ueno Yuriko Taguchi Nobuhiro Tomaru Yoshihiko Tsumura 《Conservation Genetics》2009,10(5):1477-1485
Fagus crenata Blume is widely distributed throughout Japanese cool-temperate deciduous broad-leaved forests, but there are two divergent
groups of populations in areas with contrasting winter climates separated by Japan’s Central Mountain Range. To facilitate
investigations of adaptive genetic differentiation of the species using potentially functional genes, we have collected Expressed
Sequence Tags and developed Simple Sequence Repeat markers using a cDNA library constructed from cambium and surrounding tissues.
In total, 270 primer pairs were designed, and 87 of the corresponding loci showed polymorphism in 16 individuals, with 2–21
alleles per locus and expected heterozygosities ranging from 0.06 to 0.97. EST-SSR markers developed in the present study
will be useful for genomic analyses of F. crenata populations. 相似文献
100.