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排序方式: 共有176条查询结果,搜索用时 15 毫秒
61.
Sors TG Ellis DR Na GN Lahner B Lee S Leustek T Pickering IJ Salt DE 《The Plant journal : for cell and molecular biology》2005,42(6):785-797
Several Astragalus species have the ability to hyperaccumulate selenium (Se) when growing in their native habitat. Given that the biochemical properties of Se parallel those of sulfur (S), we examined the activity of key S assimilatory enzymes ATP sulfurylase (ATPS), APS reductase (APR), and serine acetyltransferase (SAT), as well as selenocysteine methyltransferase (SMT), in eight Astragalus species with varying abilities to accumulate Se. Se hyperaccumulation was found to positively correlate with shoot accumulation of S-methylcysteine (MeCys) and Se-methylselenocysteine (MeSeCys), in addition to the level of SMT enzymatic activity. However, no correlation was observed between Se hyperaccumulation and ATPS, APR, and SAT activities in shoot tissue. Transgenic Arabidopsis thaliana overexpressing both ATPS and APR had a significant enhancement of selenate reduction as a proportion of total Se, whereas SAT overexpression resulted in only a slight increase in selenate reduction to organic forms. In general, total Se accumulation in shoots was lower in the transgenic plants overexpressing ATPS, PaAPR, and SAT. Root growth was adversely affected by selenate treatment in both ATPS and SAT overexpressors and less so in the PaAPR transgenic plants. Such observations support our conclusions that ATPS and APR are major contributors of selenate reduction in planta. However, Se hyperaccumulation in Astragalus is not driven by an overall increase in the capacity of these enzymes, but rather by either an increased Se flux through the S assimilatory pathway, generated by the biosynthesis of the sink metabolites MeCys or MeSeCys, or through an as yet unidentified Se assimilation pathway. 相似文献
62.
Indian mustard (Brassica
juncea) plants exposed to Pb and EDTA in hydroponic solution
were able to accumulate up to 55 mmol kg−1 Pb in dry shoot
tissue (1.1% [w/w]). This represents a 75-fold concentration of Pb
in shoot tissue over that in solution. A threshold concentration of
EDTA (0.25 mm) was found to be required to stimulate this
dramatic accumulation of both Pb and EDTA in shoots. Below this
threshold concentration, EDTA also accumulated in shoots but at a
reduced rate. Direct measurement of a complex of Pb and EDTA (Pb-EDTA)
in xylem exudate of Indian mustard confirmed that the majority of Pb in
these plants is transported in coordination with EDTA. The accumulation
of EDTA in shoot tissue was also observed to be directly correlated
with the accumulation of Pb. Exposure of Indian mustard to high
concentrations of Pb and EDTA caused reductions in both the
transpiration rate and the shoot water content. The onset of these
symptoms was correlated with the presence of free protonated EDTA
(H-EDTA) in the hydroponic solution, suggesting that free H-EDTA is
more phytotoxic than Pb-EDTA. These studies clearly demonstrate that
coordination of Pb transport by EDTA enhances the mobility within the
plants of this otherwise insoluble metal ion, allowing plants to
accumulate high concentrations of Pb in shoots. The finding that both
H-EDTA and Pb-EDTA are mobile within plants also has important
implications for the use of metal chelates in plant nutritional
research.The synthetic chelate EDTA forms a soluble complex with many
metals, including Pb (Kroschwitz, 1995), and can solubilize Pb from
soil particles (Means and Crerar, 1978). Recently, application of EDTA
to Pb-contaminated soils has been shown to induce the uptake of Pb by
plants (Jøgensen, 1993; Huang and Cunningham, 1996; Blaylock et al.,
1997; Huang et al., 1997), causing Pb to accumulate to more than 1%
(w/w) of shoot dry biomass (Huang and Cunningham, 1996; Blaylock et
al., 1997; Huang et al., 1997). For the in situ remediation of
Pb-contaminated soils it appears that this chelate-assisted
phytoextraction strategy (Salt et al., 1998) may be more effective than
a strategy based on the natural ability of certain wild plant species
for metal hyperaccumulation (Chaney, 1983; Baker et al., 1988).For more than 40 years, synthetic chelates have been used to supply
plants with micronutrients in both soil and hydroponics. Yet the
mechanisms by which chelates enhance metal accumulation are still not
well characterized (Wallace and Wallace, 1992), and what is known
appears contradictory. For example, some evidence suggests that the
Fe-chelate EDTA can be absorbed by plants and translocated to shoots
(Weinstein et al., 1954; Hill-Cottingham and Llyod-Jones, 1961, 1965).
However, Tiffin et al. (1960) concluded that Fe-chelates are excluded
from root tissue, and this was supported by Chaney et al. (1972), who
demonstrated that Fe is taken up by plants only after first being split
from the Fe-chelate complex by the action of a specific plasma
membrane-bound Fe-chelate reductase.To optimize the process of chelate-assisted phytoextraction, it is
important to understand the biological mechanisms responsible for this
process. Because of the stimulatory role of chelate application in the
uptake of Pb and other metals by plants, we have investigated the role
of EDTA in Pb accumulation in plants. In this study we have
demonstrated that the previously described EDTA-enhanced Pb
accumulation in Indian mustard (Brassica juncea) is based on
the ability of EDTA to chelate and transport Pb from soil into shoot
tissue. 相似文献
63.
Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: II. Cloning and expression in Escherichia coli 总被引:7,自引:0,他引:7
Crawford IP; Wilde A; Yelverton EM; Figurski D; Hedges RW 《Molecular biology and evolution》1986,3(5):449-458
The genes for the large and small subunits of anthranilate synthase (trpE
and trpG, respectively) have been cloned from Pseudomonas aeruginosa PAC174
into E. coli by R-prime formation with the broad-host- range plasmid
R68.44. Sequential subcloning into plasmid vectors reduced the active
Pseudomonas DNA fragment to a length of 3.1 kb. We obtained evidence that
this region contains the promoter for its own expression and retains a
vestigial regulatory response to tryptophan scarcity or excess.
相似文献
64.
Alun M. Salt 《PloS one》2009,4(11)
Despite its appearing to be a simple question to answer, there has been no consensus as to whether or not the alignments of ancient Greek temples reflect astronomical intentions. Here I present the results of a survey of archaic and classical Greek temples in Sicily and compare them with temples in Greece. Using a binomial test I show strong evidence that there is a preference for solar orientations. I then speculate that differences in alignment patterns between Sicily and Greece reflect differing pressures in the expression of ethnic identity. 相似文献
65.
ANSON V. KOEHLER JOHN M. PEARCE PAUL L. FLINT J. CHRISTIAN FRANSON HON S. IP 《Molecular ecology》2008,17(21):4754-4762
The role of migratory birds in the movement of the highly pathogenic (HP) avian influenza H5N1 remains a subject of debate. Testing hypotheses regarding intercontinental movement of low pathogenic avian influenza (LPAI) viruses will help evaluate the potential that wild birds could carry Asian-origin strains of HP avian influenza to North America during migration. Previous North American assessments of LPAI genetic variation have found few Asian reassortment events. Here, we present results from whole-genome analyses of LPAI isolates collected in Alaska from the northern pintail (Anas acuta), a species that migrates between North America and Asia. Phylogenetic analyses confirmed the genetic divergence between Asian and North American strains of LPAI, but also suggested inter-continental virus exchange and at a higher frequency than previously documented. In 38 isolates from Alaska, nearly half (44.7%) had at least one gene segment more closely related to Asian than to North American strains of LPAI. Additionally, sequences of several Asian LPAI isolates from GenBank clustered more closely with North American northern pintail isolates than with other Asian origin viruses. Our data support the role of wild birds in the intercontinental transfer of influenza viruses, and reveal a higher degree of transfer in Alaska than elsewhere in North America. 相似文献
66.
67.
Mapping and validation of quantitative trait loci associated with concentrations of 16 elements in unmilled rice grain 总被引:2,自引:0,他引:2
Min Zhang Shannon R. M. Pinson Lee Tarpley Xin-Yuan Huang Brett Lahner Elena Yakubova Ivan Baxter Mary Lou Guerinot David E. Salt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2014,127(1):137-165
Key Message
QTLs controlling the concentrations elements in rice grain were identified in two mapping populations. The QTLs were clustered such that most genomic regions were associated with more than one element.Abstract
In this study, quantitative trait loci (QTLs) affecting the concentrations of 16 elements in whole, unmilled rice (Oryza sativa L.) grain were identified. Two rice mapping populations, the ‘Lemont’ × ‘TeQing’ recombinant inbred lines (LT-RILs), and the TeQing-into-Lemont backcross introgression lines (TILs) were used. To increase opportunity to detect and characterize QTLs, the TILs were grown under two contrasting field conditions, flooded and irrigated-but-unflooded. Correlations between the individual elements and between each element with grain shape, plant height, and time of heading were also studied. Transgressive segregation was observed among the LT-RILs for all elements. The 134 QTLs identified as associated with the grain concentrations of individual elements were found clustered into 39 genomic regions, 34 of which were found associated with grain element concentration in more than one population and/or flooding treatment. More QTLs were found significant among flooded TILs (92) than among unflooded TILs (47) or among flooded LT-RILs (40). Twenty-seven of the 40 QTLs identified among the LT-RILs were associated with the same element among the TILs. At least one QTL per element was validated in two or more population/environments. Nearly all of the grain element loci were linked to QTLs affecting additional elements, supporting the concept of element networks within plants. Several of the grain element QTLs co-located with QTLs for grain shape, plant height, and days to heading; but did not always differ for grain elemental concentration as predicted by those traits alone. A number of interesting patterns were found, including a strong Mg–P–K complex. 相似文献68.
69.
70.