全文获取类型
收费全文 | 97篇 |
免费 | 9篇 |
出版年
2022年 | 1篇 |
2020年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1968年 | 5篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有106条查询结果,搜索用时 15 毫秒
61.
K Ramamoorthy Subramanian Raghunandhakumar RS Anand A Paramasivam S Kamaraj S Nagaraj Devaraj Ezhilarasan Thangavelu Lakshmi Kamal Dua Dinesh Kumar Chellappan Ashokkumar Veeramuthu 《Bioinformation》2020,16(11):965
Astaxanthin (AXN) is known to have health benefits by epidemiological studies. Therefore, it is of interest to assess the effect of AXN (derived from indigenous unicellular green alga Haematococcus lacustris) to modulate cell cycle arrest, lysosomal acidification and eventually apoptosis using in vitro in A549 lung cancer cells. Natural extracts of astaxanthin were obtained by standardized methods as reported earlier and characterized by standard HPLC and MS. Treatment of A549 cells with AXN (purified fraction) showed significant reduction in cell viability (about 50%) as compared to crude extract at 50µM concentration. Thus, we show the anticancer effects and lysosomal acidification in A549 cells by Astaxanthin from Haematococcus lacustris for further consideration. Together, our results demonstrated the anticancer potential of AXN from Haematococcus lacustris, which is found to be mediated via its ability to induce cell cycle arrest, lysosomal acidification and apoptotic induction. 相似文献
62.
Background
Modeling of transmembrane domains (TMDs) requires correct prediction of interfacial residues for in-silico modeling and membrane insertion studies. This implies the defining of a target sequence long enough to contain interfacial residues. However, too long sequences induce artifactual polymorphism: within tested modeling methods, the longer the target sequence, the more variable the secondary structure, as though the procedure were stopped before the end of the calculation (which may in fact be unreachable). Moreover, delimitation of these TMDs can produce variable results with sequence based two-dimensional prediction methods, especially for sequences showing polymorphism. To solve this problem, we developed a new modeling procedure using the PepLook method. We scanned the sequences by modeling peptides from the target sequence with a window of 19 residues.Results
Using sequences whose NMR-structures are already known (GpA, EphA1 and Erb2-HER2), we first determined that the hydrophobic to hydrophilic accessible surface area ratio (ASAr) was the best criterion for delimiting the TMD sequence. The length of the helical structure and the Impala method further supported the determination of the TMD limits. This method was applied to the IL-2Rβ and IL-2Rγ TMD sequences of Homo sapiens, Rattus norvegicus, Mus musculus and Bos taurus.Conclusions
We succeeded in reducing the variation in the TMD limits to only 2 residues and in gaining structural information. 相似文献63.
Tracy Van Holt Carlos A. Moreno Michael W. Binford Kenneth M. Portier Sandor Mulsow Thomas K. Frazer 《Global Change Biology》2012,18(7):2147-2160
At least half of the world's population resides in the coastal zone and the livelihoods of billions of people are affected either directly or indirectly by the production and sustainability of nearshore fisheries. Landscape change, specifically development of tree plantations, is accelerating worldwide as developing countries integrate into global markets to sell goods, offer climate‐mitigation services (carbon), and/or provide renewable energy. These changes can release excess nutrients into adjacent coastal waters causing eutrophication that alters the structure and function of coastal ecosystems. This study examined the relationship between coastal drainage basin land use/land cover change (LCLUC), specifically development of tree plantations, patterns of chlorophyll‐a in nearshore coastal waters, and the biological condition of commercially important shellfish, Concholepas concholepas (loco) in southern Chile. Locos (N = 1374) were sampled across 13 watersheds (35 853 km2) and 42 fisheries management areas (spanning 250 km of coastline). Locos harvested from management areas influenced by tree plantations had approximately 30% more endobiont (shell‐boring) phoronids, almost twice as many endobiont polychaetes and twice as many epibiont (shell‐attaching) barnacles than locos from areas in close proximity to watersheds dominated by native forests (15–20% of the watershed). Phoronid infested locos from coastal waters adjacent to watersheds with tree plantations were of relatively poor biological condition (smaller and narrower in width) and of reduced market value. Our study suggests that tree plantations result in indirect ecological impacts to coastal fisheries (more nutrients and higher phytoplankton biomass, resulting in smaller, low quality locos), and costs are born by coastal fishers (lower prices for locos). Increases in tree plantations could thus potentially significantly impact coastal fisheries worldwide and such problems should be managed as an interconnected network of land use change, oceanic ecosystems, and economic systems that are considered an integrated socio‐ecological system. 相似文献
64.
Dragovich PS Zhou R Webber SE Prins TJ Kwok AK Okano K Fuhrman SA Zalman LS Maldonado FC Brown EL Meador JW Patick AK Ford CE Brothers MA Binford SL Matthews DA Ferre RA Worland ST 《Bioorganic & medicinal chemistry letters》2000,10(1):45-48
Tripeptide-derived molecules incorporating C-terminal ketone electrophiles were evaluated as reversible inhibitors of the cysteine-containing human rhinovirus 3C protease (3CP). An optimized example of such compounds displayed potent 3CP inhibition activity (K = 0.0045 microM) and in vitro antiviral properties (EC50=0.34 microM) when tested against HRV serotype-14. 相似文献
65.
The performance of fungal xylan-degrading enzyme preparations in elemental chlorine-free bleaching for Eucalyptus pulp 总被引:2,自引:0,他引:2
Medeiros RG Silva FG Salles BC Estelles RS Filho EX 《Journal of industrial microbiology & biotechnology》2002,28(4):204-206
Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed
without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin
was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness
of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping. Journal of Industrial Microbiology & Biotechnology (2002) 28, 204–206 DOI: 10.1038/sj/jim/7000227
Received 27 April 2001/ Accepted in revised form 03 November 2001 相似文献
66.
Michael W. Binford 《Hydrobiologia》1986,143(1):123-128
Paleolimnological study of plant and animal microfossils is based on either relative abundances or net accumulation rates of various taxa. Interpretation of the latter is difficult because ecological factors that influence accumulation rates have been unknown. I use a novel method of 210Pb assay to estimate net accumulation rates of bosminids and chydorids at the sediment-water interface of 15 Florida (U.S.A.) lakes which represent a wide range of trophic state, water chemistry, and morphometry. Thirty-two species of Chydoridae, and two genera of Bosminidae were recovered from the lake sediments. Accumulation rates of 6 of the 11 more abundant chydorid species and both bosminid taxa were positively correlated with trophic state as measured by chlorophyll a concentration. Lake size was positively correlated with accumulation rates of 4 chydorid species and both bosminids. Weedbed area was positively correlated with accumulation rates of 2 chydorids, but neither bosminid. Lakewater pH was positively correlated with only one chydorid species accumulation rate. Multiple regression models explain statistically nearly all of the variance in each of the limnological variables, and can be used as transfer functions for paleolimnological inference. 相似文献
67.
Walter RB; Rolig RL; Kozak KA; McEntire B; Morizot DC; Nairn RS 《Molecular biology and evolution》1993,10(6):1227-1238
Fishes represent the stem vertebrate condition and have maintained several
gene arrangements common to mammalian genomes throughout the 450 Myr of
divergence from a common ancestor. One such syntenic arrangement includes
the GPI-PEPD enzyme association on Xiphophorus linkage group IV and human
chromosome 19. Previously we assigned the Xiphophorus homologue of the
human ERCC2 gene to linkage group U5 in tight association with the CKM
locus. CKM is also tightly linked to the ERCC2 locus on human chromosome
19, leading to speculation that human chromosome 19 may have arisen by
fusion of two ancestral linkage groups which have been maintained in
fishes. To investigate this hypothesis further, we isolated and sequenced
Xiphophorus fish genomic regions exhibiting considerable sequence
similarity to the human DNA ligase 1 amino acid sequence. Comparison of the
fish DNA ligase sequence with those of other species suggests several modes
of amino acid conservation in this gene. A 2.2-kb restriction fragment
containing part of an X. maculatus DNA ligase 1 exon was used in backcross
hybrid mapping with 12 enzyme or RFLP loci. Significant linkage was
observed between the nucleoside phosphorylase (NP2) and the DNA ligase
(LIG1) loci on Xiphophorus linkage group VI. This assignment suggests that
the association of four DNA repair-related genes on human chromosome 19 may
be the result of chance chromosomal rearrangements.
相似文献
68.
NAJA VØRS 《The Journal of eukaryotic microbiology》1993,40(3):272-287
ABSTRACT. Thirty four taxa of heterotrophic protists (amoebae, flagellates and heliozoa) were encountered in cultures established from marine samples from Belize (Central America) and Tenerife (Canary Islands). Most species are flagellates drawn from the choanoflagellates, the cryptophyceans, the euglenids, the kinetoplastids, the bicosoecids, the chromulinids, the pedinellids and a variety of laxa of uncertain affinities (Protista incertae sedis). the identity of the thecate choanoflagellates Salpingoeca ringens Kent, 1880, and S. tuba Kent, 1880, is discussed, and four new species of heterotrophic protists are described: one new species of the amoeba genus Paulinella (Paulinella intermedia n. sp.) and three new species of the incertae sedis genus Luffisphaera Belcher & Swale, 1975 ( Luffisphaera bulbochaete n. sp.; L. longihastis n. sp.; L. turriformis n. sp.). 相似文献
69.
Regier JC; Fang QQ; Mitter C; Peigler RS; Friedlander TP; Solis MA 《Molecular biology and evolution》1998,15(9):1172-1182
Evolution and phylogenetic utility of the period gene are explored through
sequence analysis of a relatively conserved 909-bp fragment in 26
lepidopteran species. Taxa range from tribes to superfamilies, primarily
within the putative clade Macrolepidotera plus near outgroups, and include
both strongly established and problematic groupings. Their divergence dates
probably range from the late Cretaceous through much of the Tertiary.
Comparisons within the same set of closely related species show that amino
acid substitutions in period occur 4.9 and 44 times as frequently as they
do in two other nuclear genes--dopa decarboxylase and elongation factor-1
alpha, respectively. In contrast, rates of observed synonymous substitution
are within 60% of each other for these three genes. Synonymous changes in
period approach saturation by the family level, whereas nonsynonymous and
amino acid divergences across the Macrolepidoptera are less than half the
maximal values reported for this gene. Phylogenetic analyses of period
strongly supported groupings at the family level and below. In contrast to
previous analyses at this level with other nuclear genes, much of the
information lies in nonsynonymous change. Relationships up to the
superfamily level were recovered with decreasing effectiveness, and little,
if any, signal was apparent regarding relationships among superfamilies.
This could reflect rapid radiation of the superfamilies, however, rather
than saturation in the period locus; thus, period, in combination with
other genes, remains a plausible candidate for approaching the difficult
problems of lepidopteran family and superfamily relationships.
相似文献
70.