全文获取类型
收费全文 | 135篇 |
免费 | 3篇 |
国内免费 | 3篇 |
出版年
2024年 | 1篇 |
2022年 | 5篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 1篇 |
2011年 | 7篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 156 毫秒
71.
The entire flower of Tulipa gesneriana cv. Murasakizuisho is purple, except the bottom, which is blue. To elucidate the mechanism of the different color development in the same petal, we prepared protoplasts from the purple and blue epidermal regions and measured the flavonoid composition by HPLC, the vacuolar pH by a proton-selective microelectrode, and element contents by the inductively coupled plasma (ICP) method. Chemical analyses revealed that the anthocyanin and flavonol compositions in both purple and blue colored protoplasts were the same; delphinidin 3-O-rutinoside (1) and major three flavonol glycosides, manghaslin (2), rutin (3) and mauritianin (4). The vacuolar pH values of the purple and blue protoplasts were 5.5 and 5.6, respectively, without any significant difference. However, the Fe(3+) content in the blue protoplast was approximately 9.5 mM, which was 25 times higher than that in the purple protoplasts. We could reproduce the purple solution by mixing 1 with two equimolar concentrations of flavonol with lambda(vismax) = 539 nm, which was identical to that of the purple protoplasts. Furthermore, addition of Fe(3+) to the mixture of 1-4 gave the blue solution with lambda(vismax) = 615 nm identical to that of the blue protoplasts. We have established that Fe(3+) is essential for blue color development in the tulip. 相似文献
72.
Ferric chloride flocculation plus carbon adsorption allows to reuse spent culture medium of Arthrospira platensis
下载免费PDF全文
![点击此处可从《Engineering in Life Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ana Lucía Morocho‐Jácome Guilherme Favaro Mascioli Sunao Sato João Carlos Monteiro de Carvalho 《Engineering in Life Science》2015,15(2):208-219
Arthrospira platensis cultivation produces a saline spent medium that must be treated to allow its reuse, thus saving water and avoiding environmental pollution. This study evaluates the association of flocculation followed by adsorption to treat the spent medium by applying different concentrations of granular activated carbon (GAC) and ferric chloride (F), and using different residence times (T). The simultaneous optimization of the independent variables GAC, F, and T was performed using both a 23 central composite design and a response surface methodology. The cells cultivated in the medium obtained after the optimal conditions of treatment (GAC = 54.2 g L?1, F = 10.0 mg L?1, and T = 30.8 min) provided the highest maximum cell concentration, Xm = 3140 ± 77 mg L?1 in 0.5 L Erlenmeyer flasks with the highest protein biomass content (44.9%). The treated medium in such conditions was also used in a 3.5 L tubular photobioreactor (PBR), reaching Xm = 4033 ± 110 mg L?1 and biomass with high contents of both protein (47.3 ± 2.6%) and chlorophyll (9.7 ± 0.3 mg g dry cell?1). Therefore, this study can contribute to diminishing costs of A. platensis production by reusing its culture medium and improving its biomass quality in PBRs. 相似文献
73.
We report here that Vibrio anguillarum possesses a non-inducible active transport system which can efficiently supply iron to the cell from ferric citrate, independently of the siderophore-based mechanisms. The strains tested were able to grow in CM9 medium in iron-restricted conditions when ferric citrate was present in the medium. Moreover, the presence of ferric citrate inhibited the production of siderophores in the strains tested. V. anguillarum cells and isolated membranes could incorporate 55Fe3+ complexed by citrate, without a difference between cells grown in the presence or absence of ferric citrate. The presence of 2,4-dinitrophenol, ferrozine, ferricyanide, trypsin, as well as low temperature produced a marked decrease or total inhibition of 55Fe3+ uptake by the cells. All these results suggest that iron uptake from ferric citrate in V. anguillarum must be an energy-dependent process not induced by the presence of iron or citrate in the medium, mediated by a membrane protein(s), which may require an iron reduction step to function. 相似文献
74.
75.
The potential of Desulfitobacterium frappieri strain G2, which was isolated from subsurface smectite bedding, to participate in iron redox reactions was investigated. Strain G2 can use poorly crystalline Fe(III) oxide, soluble forms of Fe(III) and Fe(III) in the structure of phyllosilicate minerals as electron acceptors. It can also oxidize Fe(II)-NTA or Fe(II) in the structure of phyllosilicate minerals with nitrate as the electron acceptor. These results suggest for the first time that strains of Desulfitobacterium frappieri may play an important role in iron cycling in sedimentary environments. 相似文献
76.
77.
The inorganic salts KCl, NaCl, CaCl2, MgCl2, and FeCl3, and especially the latter, significantly increased xylose monomer and xylotriose degradation in water heated to 180 degrees C with unaccountable losses of xylose amounting to as high as 65% and 78% for xylose and xylotriose, respectively, after 20 min incubation with 0.8% FeCl3. Furthermore, losses of both xylose and xylotriose were well described by first order homogeneous kinetics, and the rate constants for xylose and xylotriose disappearance increased 6- and 49-fold, respectively, when treated with 0.8% FeCl3 solution compared to treatment with just pressurized hot water at the same temperature. Although the addition of these inorganic salts produced a significant drop in pH, the degradation rates with salts were much faster than could be accounted for by a pH change. For example, the rate constants for the disappearance of xylose and xylotriose with 0.8% FeCl3 were 3-fold and 7-fold greater, respectively, than for treatment with very dilute sulfuric acid at the same pH. In addition, xylose losses were greater than could be accounted for by just furfural production, suggesting that other degradation products were also formed, and xylose losses to unidentified compounds increased significantly with the addition of FeCl3. The unidentified compounds could be formed through aqueous furfural resinification and condensation reactions that are accelerated by FeCl3, but the actual mechanisms are still not clear. 相似文献
78.
Expression profiling of the Arabidopsis ferric chelate reductase (FRO) gene family reveals differential regulation by iron and copper 总被引:1,自引:0,他引:1
The Arabidopsis FRO2 gene encodes the iron deficiency-inducible ferric chelate reductase responsible for reduction of iron at the root surface; subsequent transport of iron across the plasma membrane is carried out by a ferrous iron transporter (IRT1). Genome annotation has identified seven additional FRO family members in the Arabidopsis genome. We used real-time RT-PCR to examine the expression of each FRO gene in different tissues and in response to iron and copper limitation. FRO2 and FRO5 are primarily expressed in roots while FRO8 is primarily expressed in shoots. FRO6 and FRO7 show high expression in all the green parts of the plant. FRO3 is expressed at high levels in roots and shoots, and expression of FRO3 is elevated in roots and shoots of iron-deficient plants. Interestingly, when plants are Cu-limited, the expression of FRO6 in shoot tissues is reduced. Expression of FRO3 is induced in roots and shoots by Cu-limitation. While it is known that FRO2 is expressed at high levels in the outer layers of iron-deficient roots, histochemical staining of FRO3-GUS plants revealed that FRO3 is predominantly expressed in the vascular cylinder of roots. Together our results suggest that FRO family members function in metal ion homeostasis in a variety of locations in the plant. 相似文献
79.
Pullakhandam R Nair MK Kasula S Kilari S Thippande TG 《Biochemical and biophysical research communications》2008,374(2):369-372
It is known that the fractional absorption of extrinsic iron from human milk is higher in infants and adults. A low molecular weight milk fraction has been proposed to increase the bioavailability of iron from human milk. Nevertheless, the mechanisms remained elusive. Here in we demonstrate ferric reductase activity (Km 7.73 × 10−6 M) in low molecular weight human milk fraction (10kF, filtrate derived from ultra filtration of milk whey through 10 kDa cutoff membrane), which increased ferric iron solubility and iron uptake in Caco-2 cells. The 10kF fraction was as effective as ascorbic acid (1:20 iron to ascorbic acid) in increasing the ferric iron solubility and uptake in Caco-2 cells. Further, gel filtration chromatography on peptide column led to co-elution of ferric reductase and iron solubilization activities at an apparent molecular mass of <1500 Da. Interestingly, only these fractions containing ferric reductase activity also stimulated the uptake of iron in Caco-2 cells. Thus, it is concluded that human milk possesses ferric reductase activity and is associated with ferric iron solubilization and enhanced absorption. 相似文献
80.
Katherine D. Weaver Jared J. Heymann Arnav Mehta Petra L. Roulhac Damon S. Anderson Andrew J. Nowalk Pratima Adhikari Timothy A. Mietzner Michael C. Fitzgerald Alvin L. Crumbliss 《Journal of biological inorganic chemistry》2008,13(6):887-898
The obligate human pathogens Haemophilus influenzae, Neisseria gonorrhoeae, and N. meningitidis utilize a highly conserved, three-protein ATP-binding cassette transporter (FbpABC) to shuttle free Fe(3+) from the periplasm and across the cytoplasmic membrane. The periplasmic binding protein, ferric binding protein (FbpA), is capable of transporting other trivalent cations, including Ga(3+), which, unlike Fe(3+), is not redox-active. Because of a similar size and charge as Fe(3+), Ga(3+) is widely used as a non-redox-active Fe(3+) substitute for studying metal complexation in proteins and bacterial populations. The investigations reported here elucidate the similarities and differences in FbpA sequestration of Ga(3+) and Fe(3+), focusing on metal selectivity and the resulting transport function. The thermodynamic binding constant for Ga(3+) complexed with FbpA at pH 6.5, in 50 mM 4-morpholineethanesulfonic acid, 200 mM KCl, 5 mM KH(2)PO(4) was determined by UV-difference spectroscopy as [Formula: see text] This represents a 10(5)-fold weaker binding relative to Fe(3+) at identical conditions. The unfolding/refolding behavior of Ga(3+) and Fe(3+) holo-FbpA were also studied using a matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy technique, stability of unpurified proteins from rates of H/D exchange (SUPREX). This analysis indicates significant differences between Fe(3+) and Ga(3+) sequestration with regard to protein folding behavior. A series of kinetic experiments established the lability of the Ga(3+)FbpA-PO(4) assembly, and the similarities/differences of stepwise loading of Fe(3+) into apo- or Ga(3+)-loaded FbpA. These biophysical characterization data are used to interpret FbpA-mediated Ga(3+) transport and toxicity in cell culture studies. 相似文献