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排序方式: 共有119条查询结果,搜索用时 15 毫秒
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The properties of bacterial isolates from polluted environments which are characterized by increased levels of oxidative stress do not reflect only the level of contaminants, but also arise as a consequence of many permanently changed conditions. The survival rate of Comamonas terrigena N3H isolates from an environment with elevated levels of H(2)O(2) is correlated with stimulation of catalase. The response of bacterial catalase to the effect of phenol in exogenous conditions was affected by the presence of an additional contaminant, Cd(2+). An isolate of Aspergillus niger selected from river sediment containing 363?mg/kg As, 93?mg/kg Sb at pH 5.2-4.8 grew on Czapek-Dox agar ~1.6 times faster than an isolate of the same species from coal dust sediment with approximately the same level of pollution (400?mg/kg As) but somewhat lower pH (3.3-2.8). It also exhibited differences in the microscopic characteristics of its mycelial structures. Both isolates exhibited a higher tolerance to the exogenic toxic effects of metals (As(5+), Cd(2+), and Cu(2+) at 5, 25, or 50?mg/L) than a control culture, but the differences in tolerance between them were only slight. These laboratory results suggest that there are complicated relationships which may exist in the "in situ" environment. 相似文献
64.
Replication-Dependent Recruitment of the β-Subunit of DNA Polymerase III from Cytosolic Spaces to Replication Forks in Escherichia coli 下载免费PDF全文
Toshinari Onogi Katsufumi Ohsumi Tsutomu Katayama Sota Hiraga 《Journal of bacteriology》2002,184(3):867-870
The beta-subunit of DNA polymerase III is located as one or two condensed clusters within the nucleoid-occupied space in exponentially growing cells of Escherichia coli. When chromosome replication is terminated after incubation at nonpermissive temperature in a temperature-sensitive dnaC mutant, the beta-subunit is located in the cytosolic spaces of the cell poles. 相似文献
65.
Yu Tabayashi Toshiyuki Godo Masumi Yamamuro Hiroshi Kamiya 《Landscape and Ecological Engineering》2017,13(1):119-129
This study aimed to evaluate the loading of nutrients of agricultural origin. We investigated monthly nutrient concentrations at 11 stations located in the Hii River, Japan. The nitrogen and oxygen stable isotope ratios in nitrate were applied to distinguish the origin of nitrogen, i.e., from fertilizers applied to paddy fields or from sewage. Although total nitrogen (TN), presumably from transboundary air pollution, was mainly loaded during the cooler season, nitrate originating from fertilizers applied to paddy fields became the main source of nitrogen in the river water during the warmer season. Phosphorus was mainly added in particulate form, and showed increased loading at the upstream stations in the warmer season, but not in the cooler season. Potassium and magnesium—components of fertilizers—showed an increasing trend in the downstream section of the paddy fields. Our results suggest that controlled application of fertilizers is necessary to decrease the nitrogen loads originating from farmlands, particularly from paddy fields. Since the nitrogen isotope of TN in fertilizer showed significantly lower values (mean value ?4.6 ‰) than that in river water (mean value 1.8 ‰) or treated water (mean value 21.9 ‰), we could use these values to determine the contribution of TN from fertilizers to river water quality, and can use them to monitor fertilization levels in watersheds. 相似文献
66.
Granule-bound starch synthase I is responsible for biosynthesis of extra-long unit chains of amylopectin in rice 总被引:1,自引:0,他引:1
Hanashiro I Itoh K Kuratomi Y Yamazaki M Igarashi T Matsugasako J Takeda Y 《Plant & cell physiology》2008,49(6):925-933
A rice Wx gene encoding a granule-bound starch synthase I (GBSSI) was introduced into the null-mutant waxy (wx) rice, and its effect on endosperm starches was examined. The apparent amylose content was increased from undetectable amounts for the non-transgenic wx cultivars to 21.6-22.2% of starch weight for the transgenic lines. The increase was in part due to a significant amount of extra-long unit chains (ELCs) of amylopectin (7.5-8.4% of amylopectin weight), that were absent in the non-transgenic wx cultivars. Thus, actual amylose content was calculated to be 14.9-16.0% for the transgenic lines. Only slight differences were found in chain-length distribution for the chains other than ELCs, indicating that the major effect of the Wx transgene on amylopectin structure was ELC formation. ELCs isolated from debranched amylopectin exhibited structures distinct from amylose. Structures of amylose from the transgenic lines were slightly different from those of cv. Labelle (Wx(a)) in terms of a higher degree of branching and size distribution. The amylose and ELC content of starches of the transgenic lines resulted in the elevation of pasting temperature, a 50% decrease in peak viscosity, a large decrease in breakdown and an increase in setback. As yet undetermined factors other than the GBSSI activity are thought to be involved in the control of formation and/or the amount of ELCs. Structural analysis of the Wx gene suggested that the presence of a tyrosine residue at position 224 of GBSSI correlates with the formation of large amounts of ELCs in cultivars carrying Wx(a). 相似文献
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68.
To utilize fermentative bacteria for producing the alternative fuel hydrogen, we performed successive rounds of P1 transduction
from the Keio Escherichia coli K-12 library to introduce multiple, stable mutations into a single bacterium to direct the metabolic flux toward hydrogen
production. E. coli cells convert glucose to various organic acids (such as succinate, pyruvate, lactate, formate, and acetate) to synthesize
energy and hydrogen from formate by the formate hydrogen-lyase (FHL) system that consists of hydrogenase 3 and formate dehydrogenase-H.
We altered the regulation of FHL by inactivating the repressor encoded by hycA and by overexpressing the activator encoded by fhlA, removed hydrogen uptake activity by deleting hyaB (hydrogenase 1) and hybC (hydrogenase 2), redirected glucose metabolism to formate by using the fdnG, fdoG, narG, focA, focB, poxB, and aceE mutations, and inactivated the succinate and lactate synthesis pathways by deleting frdC and ldhA, respectively. The best of the metabolically engineered strains, BW25113 hyaB hybC hycA fdoG frdC ldhA aceE, increased hydrogen production 4.6-fold from glucose and increased the hydrogen yield twofold from 0.65 to 1.3 mol H2/mol glucose (maximum, 2 mol H2/mol glucose). 相似文献
69.
Yoshiharu Matahira Atsushi Tashiro Toshinari Sato Hirokazu Kawagishi Taichi Usui 《Glycoconjugate journal》1995,12(5):664-671
N-acetylhexosaminidase fromNocardia orientalis catalysed the synthesis of lacto-N-triose II glycoside (-d-GlcNAc-(1-3)--d-Gal-(1-4)--d-Glc-OMe,3) with its isomers -d-GlcNAc-(1-6)--d-Gal-(1-4)--d-Glc-OMe (4) and -d-Gal-(1-4)-[-d-GlcNAc-(1-6)]--d-Glc-OMe (5) throughN-acetylglucosaminyl transfer fromN,N-diacetylchitobiose (GlcNAc2) to methyl -lactoside. The enzyme formed the mixture of trisac-charides3, 4 and5 in 17% overall yield based on GlcNAc2, in a ratio of 20:21:59. Withp-nitrophenyl -lactoside as an acceptor, the enzyme also producedp-nitrophenyl -lacto-N-trioside II (-d-GlcNAc-(1-3)--d-Gal-(1-4)--d-Glc-OC6H4NO2-p,6) with its isomers -d-GlcNAc-(1-6)--d-Gal-(1-4)--d-Glc-OC6H4NO2-p (7) and -d-Gal-(1-4)-[-d-GlcNAc-(1-6)]--d-Glc-OC6H4NO2-p (8). In this case, when an inclusion complex ofp-nitrophenyl lactoside acceptor with -cyclodextrin was used, the regioselectivity of glycosidase-catalysed formation of trisaccharide glycoside was substantially changed. It resulted not only in a significant increase of the overall yield of transfer products, but also in the proportion of the desired compound6.Abbreviations GlcNAc2
2-acetamido-2-deoxy--d-glucopyranosyl-(1-4)-2-acetamido-2-deoxy-d-glucose
- NAHase
N-acetylhexosaminidase
- -CD
-cyclodextrin 相似文献
70.
Ando H Yanagihara H Sugimoto K Hayashi Y Tsuruoka S Takamura T Kaneko S Fujimura A 《Chronobiology international》2005,22(4):655-665
Recent studies have shown the gene expression of several transporters to be circadian rhythmic. However, it remains to be elucidated whether the expression of P-glycoprotein, which is involved in the transport of many medications, undergoes 24 h rhythmicity. To address this issue, we investigated daily profiles of P-glycoprotein mRNA and protein levels in peripheral mouse tissues. In the liver and intestine, but not in the kidney, Abcb1a mRNA expression showed clear 24 h rhythmicity. On the other hand, Abcb1b and Abcb4, the other P-glycoprotein genes, did not exhibit significant rhythmic expression in the studied tissues. In the intestine, levels of whole P-glycoprotein also exhibited a daily rhythm, with a peak occurring in the latter half of the light phase and a trough at the onset of the light phase. Consistent with the day-night change of P-glycoprotein level, the ex vivo accumulation of digoxin, an Abcb1a P-glycoprotein substrate, into the intestinal segments at the onset of dark phase was significantly lower than it was at the onset of the light phase. Thus, Abcb1a P-glycoprotein expression, and apparently its function, are 24 h rhythmic at least in mouse intestine tissue. This circadian variation might be involved in various chronopharmacological phenomena. 相似文献