全文获取类型
收费全文 | 342篇 |
免费 | 47篇 |
国内免费 | 42篇 |
出版年
2023年 | 15篇 |
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 23篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 19篇 |
2013年 | 33篇 |
2012年 | 13篇 |
2011年 | 22篇 |
2010年 | 8篇 |
2009年 | 19篇 |
2008年 | 18篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 22篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有431条查询结果,搜索用时 126 毫秒
51.
52.
Previously, we reported that mitochondria-associated hexokinases are active in controlling programmed cell death in plants
(Plant Cell 18, 2341-2355). Here, we investigated their role under abiotic- and biotic-stress conditions. Expression ofNbHxk1, aNicotiana benthamiana hexokinase gene, was stimulated by treatment with salicylic acid or methyl viologen (MV), and was also up-regulated by pathogen
infection. In response to MV-induced oxidative stress, NbHxk1-silenced plants exhibited increased susceptibility, while the
HXK1— and HXK2-overexpressingArabidopsis plants had enhanced tolerance. Moreover, those overexpressing plants showed greater resistance to the necrotrophic fungal
pathogenAlternaria brassicicola. HXK-over-expression also mildly protected plants against the bacterial pathogenPseudomonas syringae pv.tomato DC3000, a response that was accompanied by increased H2O2 production and elevatedPR1 gene expression. These results demonstrate that higher levels of hexokinase confer improved resistance to MV-induced oxidative
stress and pathogen infection. 相似文献
53.
Brandalise M Maia IG Borecký J Vercesi AE Arruda P 《Journal of bioenergetics and biomembranes》2003,35(3):203-209
An Arabidopsis thaliana cDNA clone encoding a plant uncoupling mitochondrial protein (AtPUMP1) was overexpressed in transgenic tobacco plants. Analysis of the AtPUMP1 mRNA content in the transgenic lines, determined by Northernblot, revealed variable levels of transgene expression. Antibody probing ofWestern blots of mitochondrial proteins from three independent transgenic lines showed significant accumulation of AtPUMP1 in this organelle. Overproduction of AtPUMP1 in transgenic tobacco plants led to a significantincrease in tolerance to oxidative stress promoted by exogenous hydrogen peroxide as compared to wild-type control plants. These results provide thefirst biological evidence for a role of PUMP in protection of plant cells against oxidative stress damage. 相似文献
54.
The N-carbamoyl-
-amino acid amidohydrolase (
-carbamoylase) gene (dcb) from Agrobacterium tumefaciens AM 10 was cloned by polymerase chain reaction in plasmid pET28a and was overexpressed in Escherichia coli JM109 (DE3). However, almost 80% of the enzyme remained trapped in inclusion bodies. To facilitate the expression of the properly folded active enzyme, the chaperones GroEL/ES were coexpressed in plasmid pKY206. This resulted in a 43-fold increase in active enzyme production compared to the wild-type strain. The histidyl-tagged
-carbamoylase was purified by a single step nickel-affinity chromatography to a specific activity of 9.5 U/mg protein. 相似文献
55.
Dissimilatory sulfite reductase (DsrAB) of the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough is an 22 tetramer of 180 kDa, encoded by the dsr operon. In addition to the dsrA and dsrB genes, this operon contains a gene (dsrD) encoding a protein of only 78 amino acids. Although, the function of DsrD is currently unknown, the presence of a dsrD gene has been demonstrated in a variety of sulfate-reducing bacteria and archaea. DsrD was expressed in Escherichia coli at a very high level and purified to homogeneity. Protein blotting experiments, using antisera raised against purified DsrD, demonstrated that it is expressed constitutively in D. vulgaris and does not copurify with DsrAB. Spectroscopic analysis of DsrD indicated that it does not bind either sulfite or sulfide, the substrate and product, respectively of the reaction catalyzed by DsrAB. Thus, although the conservation of this protein and its demonstrated presence in D. vulgaris, suggest an essential function in dissimilatory sulfite reduction, this function remains to be elucidated. 相似文献
56.
Metabolic engineering of plant secondary products 总被引:5,自引:0,他引:5
Craig L. Nessler 《Transgenic research》1994,3(2):109-115
Plants interact with their environment by producing a diverse array of secondary metabolites. Many of these compounds are valued for their medicinal, industrial or agricultural properties. Other secondary products are toxic or otherwise undesirable and can reduce the commercial value of crops. Gene transfer technology offers new opportunities to modify directly plant secondary product synthesis through metabolic engineering. This article reviews some of the strategies which have been used to increase or decrease the synthesis of specific plant metabolites, as well as methods for expanding the biosynthetic capabilities of individual species. 相似文献
57.
Yang J Murthy S Winata T Werner S Abe M Prahalad AK Hock JM 《Biochemical and biophysical research communications》2006,344(1):346-352
The cellular and molecular mechanisms that underlie skeletal abnormalities in defective Recql4-related syndromes are poorly understood. Our objective in this study was to explore the function of Recql4 in osteoblast biology both in vitro and in vivo. Immunohistochemistry on adult mouse bone showed Recql4 protein localization in active osteoblasts around growth plate, but not in fully differentiated osteocytes. Consistent with this finding, Recql4 gene expression was high in proliferating mouse osteoblastic MC3T3.E1 cells and decreased as cells progressively lost their proliferation activity during differentiation. Recql4 overexpression in osteoblastic cells exhibited higher proliferation activity, while its depletion impeded cell growth. In addition, bone marrow stromal cells from male Recql4+/- mice had fewer progenitor cells, including osteoprogenitors, indicated by reduced total fibroblast colony forming units (CFU-f) and alkaline phosphatase-positive CFU-f colonies concomitant with reduced bone mass. These findings provide evidence that Recql4 functions as a regulatory protein during osteoprogenitor proliferation, a critical cellular event during skeleton development. 相似文献
58.
Iwaki T Haranoh K Inoue N Kojima K Satoh R Nishino T Wada S Ihara H Tsuyama S Kobayashi H Wadano A 《Photosynthesis research》2006,88(3):287-297
A reporter gene assay revealed that promoters derived from Synechococcus PCC7942 (S.7942) psbAI and Synechocystis PCC6803 (S.6803) psbAII were suitable for the expression of foreign ribulose-bisphosphate carboxylase (RuBisCO; EC 4.1.1.39) in S.7942 cells. Transformational vectors with a promoter and a foreign RuBisCO gene, cvrbc originated from Allochromatium vinosum, were constructed on a binary vector, pUC303, and introduced to S.7942 cells. When the cvrbc was expressed with the S.7942 psbAI promoter, the total RuBisCO activity increased 2.5- to 4-fold than that of the wild type cell. The S.6803 psbAII promoter increased the activity of the transformant 1.5–2 times of that of wild type cell. There was a significant increase in the rate of photosynthesis depending on the increase of RuBisCO activity. The maximum rate of photosynthesis of the transformant cell was 1.63 times higher than that of the wild type under the illumination of 400 μmol m−2 s−1, at 20 mM bicarbonate and at 30 °C. Although the photosynthesis of the higher plant is limited by the ability of photosystems under high irradiance and the high CO2 concentration, that of the S.7942 cell is limited by the RuBisCO activity, even at high CO2 concentrations and under high irradiance. 相似文献
59.
Overexpression of an alkaline lipase gene from Proteus vulgaris K80 in Escherichia coli BL21/pKLE 总被引:1,自引:0,他引:1
Hong-Weon Lee Sun-Jun Yoon Hyung-Kwoun Kim Kyong-Mun Park Tae-Kwang Oh Joon-Ki Jung 《Biotechnology letters》2000,22(19):1543-1547
Over-expression of Proteus vulgaris K80 lipase gene in Escherichia coli BL21 (DE3)/pKLE was achieved, with the enzyme being produced in an as active soluble form, using the T7 RNA polymerase system in a modified M9 salt or M9ZB medium. d-Lactose (55 mM) was used to induce gene expression and gave twice the lipase activity achieved with 0.4 mM IPTG. The expression of the lipase gene depended on the feeding rate of glucose being optimal at 12 g l–1 h–1. 相似文献
60.
Transgenic tobacco (Nicotiana tabacum L.) plants with decreased and increased transport capacities of the chloroplast triose phosphate/phosphate translocator (TPT)
were used to study the control the TPT exerts on the flux of starch and sucrose biosynthesis, as well as CO2 assimilation, respiration and photosynthetic electron transport. For this purpose, tobacco lines with an antisense repression
of the endogenous TPT (αTPT) and tobacco lines overexpressing a TPT gene from Flaveria trinervia (FtTPT) were used. In ambient CO2, there was no or little effect of altered TPT transport activities on either rates of photosynthetic electron transport and/or
CO2 assimilation. However, in elevated CO2 (1500 μl · l−1) and low O2 (2%) the TPT exerted strong control on the rate of CO2 assimilation (control coefficient for the wild type; CJA
TPT=0.30) in saturating light. Similarly, the incorporation of 14C into starch in high CO2 was increased in tobacco plants with decreased TPT activity, but was reduced in plants overexpressing the TPT from F. trinervia. Thus, the TPT exerted negative control on the rate of starch biosynthesis with a CJStarch
TPT=−0.19 in the wild type estimated from a hyperbolic curve fitted to the data points. This was less than the positive control
strength on the rate of sucrose biosynthesis (CJSuc
TPT=0.35 in the wild type). Theoretically, the positive control exerted on sucrose biosynthesis should be numerically identical
to the negative control on starch biosynthesis unless additional metabolic pathways are affected. The rate of dark respiration
showed some correlation with the TPT activity in that it increased in FtTPT overexpressors, but decreased in αTPT plants with
an apparent control coefficient of CJRes
TPT=0.24. If the control on sucrose biosynthesis is referred to as “gain of carbon” (positive control) and the control on starch
biosynthesis as well as dark respiration as a “loss of carbon” (negative control) for sucrose biosynthesis and subsequent
export, the sum of the control coefficients on dark respiration and starch biosynthesis would be numerically similar to the
control coefficient on the rate of sucrose biosynthesis. There was also some control on the rate of photosynthetic electron
transport, but only at high light and in elevated CO2 combined with low O2. The control coefficient for the rate of photosynthetic electron transport was CJETR
TPT=0.16 in the wild type. Control coefficients were also calculated for plants with elevated and lowered TPT activity. Furthermore,
the extent to which starch degradation/glucose utilisation compensates for the lack of triose phosphate export was assessed.
The TPT also exerted control on metabolite contents in air.
Received: 26 March 1999 / Accepted: 21 August 1999 相似文献