全文获取类型
收费全文 | 622篇 |
免费 | 15篇 |
国内免费 | 14篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 16篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 18篇 |
2013年 | 21篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 24篇 |
2008年 | 29篇 |
2007年 | 29篇 |
2006年 | 33篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 21篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有651条查询结果,搜索用时 31 毫秒
131.
We isolated the gene encoding lysine-ketoglutarate reductase (LKR, EC 1.5.1.8) and saccharopine dehydrogenase (SDH, ED 1.5.1.9) from an Arabidopsis thaliana genomic DNA library based on the homology between the yeast biosynthetic genes encoding SDH (lysine-forming) or SDH (glutamate-forming) and Arabidopsis expressed sequence tags. A corresponding cDNA was isolated from total Arabidopsis RNA using RT-PCR and 5 and 3 Race. DNA sequencing revealed that the gene encodes a bifunctional protein with an amino domain homologous to SDH (lysine-forming), thus corresponding to LKR, and a carboxy domain homologous to SDH (glutamate-forming). Sequence comparison between the plant gene product and the yeast lysine-forming and glutamate-forming SDHs showed 25% and 37% sequence identity, respectively. No intracellular targeting sequence was found at the N-terminal or C-terminal of the protein. The gene is interrupted by 24 introns ranging in size from 68 to 352 bp and is present in Arabidopsis in a single copy. 5 sequence analysis revealed several conserved promoter sequence motifs, but did not reveal sequence homologies to either an Opaque 2 binding site or a Sph box. The 3-flanking region does not contain a polyadenylation signal resembling the consensus sequence AATAAA. The plant SDH was expressed in Escherichia coli and exhibited similar biochemical characteristics to those reported for the purified enzyme from maize. This is the first report of the molecular cloning of a plant LKR-SDH genomic and cDNA sequence. 相似文献
132.
Royston Goodacre Eadaoin M. Timmins Paul J. Rooney Jem J. Rowland Douglas B. Kell 《FEMS microbiology letters》1996,140(2-3):233-239
133.
Tanim Jabid Hossain Hiroto Hirayama Yoichiro Harada 《Bioscience, biotechnology, and biochemistry》2016,80(1):152-157
In the cytosol of Saccharomyces cerevisiae, most of the free N-glycans (FNGs) are generated from misfolded glycoproteins by the action of the cytoplasmic peptide: N-glycanase (Png1). A cytosol/vacuole α-mannosidase, Ams1, then trims the FNGs to eventually form a trisaccharide composed of Manβ1,4GlcNAc β1,4GlcNAc (Man1GlcNAc2). Whether or not the resulting Man1GlcNAc2 is enzymatically degraded further, however, is currently unknown. The objective of this study was to unveil the fate of Man1GlcNAc2 in S. cerevisiae. Quantitative analyses of the FNGs revealed a steady increase in the amount of Man1GlcNAc2 produced in the post-diauxic and stationary phases, suggesting that this trisaccharide is not catabolized during this period. Inoculation of the stationary phase cells into fresh medium resulted in a reduction in the levels of Man1GlcNAc2. However, this reduction was caused by its dilution due to cell division in the fresh medium. Our results thus indicate that Man1GlcNAc2 is not enzymatically catabolized in S. cerevisiae. 相似文献
134.
Katsumi Shibata Marika Yamazaki Yukiyo Matsuyama 《Bioscience, biotechnology, and biochemistry》2016,80(11):2208-2216
The present study was conducted to survey functional biomarkers for evaluation of niacin nutritional status. Over 500 enzymes require niacin as a coenzyme. Of these, we chose the tryptophan degradation pathway. To create niacin-deficient animals, quinolinic acid phosphoribosyltransferase-knock out mice were used in the present study because wild type mice can synthesize nicotinamide from tryptophan. When the mice were made niacin-deficient, the urinary excretion of xanthurenic acid (XA) was extremely low compared with control mice; however, it increased according to the recovery of niacin nutritional status. The urinary excretion of kynurenic acid (KA) was the reverse of XA. Kynurenine 3-monooxygenase, which needs NADPH, was thought to be suppressed by niacin deficiency. Thus, we calculated the urinary excretion ratio of XA:KA as a functional biomarker of niacin nutrition. The ratio increased according to recovering niacin nutritional status. Low values equate with low niacin nutritional status. 相似文献
135.
Joseph R. Koke Ling Min Fu Dandan Sun Donna M. Vaughan Neville Bittar 《Molecular and cellular biochemistry》1989,86(2):107-113
Summary The effects of inhibitors of adenosine catabolism on contractile function and metabolites were assessed during 15 minutes of ischemia followed by 30 minutes of reperfusion in the open-chest dog heart. As compared to sham treatment, pretreatment with erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and dipyridamole (DP) protected contractile function during ischemia, and improved recovery of high energy phosphate content and contractile fucntion during reperfusion following ischemia. Testing EHNA and DP in a free-radical generating system indicated both compounds have some scavenging ability, suggesting the effect of EHNA + DP may not be on adenosine nucleotide metabolism alone. Comparison of end diastolic segment lengths to contractile function indicated the results were not affected by changes in preload resulting from peripheral vasodilation.With the technical assistance of Dennis Dahmen. 相似文献
136.
A general method for the transfer of cloned genes to plant cells 总被引:8,自引:0,他引:8
137.
Genetic analysis of mannityl opine catabolism in octopine-type Agrobacterium tumefaciens strain 15955 总被引:11,自引:0,他引:11
Yves Dessaux Jacques Tempé Stephen K. Farrand 《Molecular & general genetics : MGG》1987,208(1-2):301-308
Summary The genetic organization of functions responsible for mannityl opine catabolism of the Ti plasmid of Agrobacterium tumefaciens strain 15955 was investigated. A partial HindIII digest of pTi15955 was cloned into a broad host range cosmid and the clones obtained were tested for ability to confer mannityl opine degradation upon Agrobacterium. Inserts containing genes for catabolism of mannopinic acid, mannopine, agropine, and agropinic acid were obtained, spanning a segment of 43 kb on the Ti plasmid. Two clones conferring upon Agrobacterium the ability to catabolize the mannityl opines were mobilized to several Rhizobium sp., to Pseudomonas putida and P. fluorescens and to Escherichia coli. The catabolic functions were phenotypically expressed in all Rhizobium sp. tested, and in P. fluorescens, but not in P. putida or in E. coli. 相似文献
138.
139.
Oxindole-3-acetic acid (OxIAA) has been identified in germinating seeds of Scots pine (Pinus sylvestris) using gas chromatography-mass spectrometry. Seeds germinated for 5 d contained 2.7 ng OxIAA·g-1 (dry weight) whereas ungerminated seeds contained 0.2 ng·g-1. Isotopically labelled OxIAA was formed in seeds incubated with [1-14C]-, [2-14C]- or [2H5]indole-3-acetic acid.Abbreviations DDC
sodium diethyldithiocarbamate
- GC
gas chromatography
- HPLC
high-performance liquid chromatography
- IAA
indole-3-acetic acid
- MS
mass spectrometry
- OxIAA
oxindole-3-acetic acid
- PVP
polyvinylpyrrolidone
- TMS
trimethylsilyl 相似文献
140.
Abstract: The mesolimbic system of the brain has been shown to be involved in the reward properties of a number of agents. It is possible that release of monoamines by nicotine in this brain area could be related to the pleasurable aspects related to cigarette smoking. In this investigation, the effect of nicotine on the release of [3 H]dopamine in the nucleus accumbens of the rat was studied. It was shown that nicotine produced a concentration-dependent increase in [3 H]dopamine release at concentrations of 0.1 μ M and above. The increase in release was found to be almost completely calcium dependent. The nicotine-induced release was only partially blocked by the nicotinic antagonists hexamethonium and d -tubocurarine. A number of cholinergic agonists, as well as other compounds, were tested for their capacity to mimic the effect of nicotine. At equimolar concentrations there was, at most, only 50% of the activity of nicotine. The results of this study demonstrate that nicotine stimulates the release of dopamine in the nucleus accumbens at concentrations similar to those in the blood of cigarette smokers. This suggests that the release of mono-amines in specific nuclei of the mesolimbic system may be an important determinant of the desire to smoke cigarettes. 相似文献