全文获取类型
收费全文 | 5729篇 |
免费 | 571篇 |
国内免费 | 315篇 |
出版年
2023年 | 48篇 |
2022年 | 39篇 |
2021年 | 149篇 |
2020年 | 192篇 |
2019年 | 177篇 |
2018年 | 138篇 |
2017年 | 173篇 |
2016年 | 189篇 |
2015年 | 339篇 |
2014年 | 337篇 |
2013年 | 427篇 |
2012年 | 362篇 |
2011年 | 274篇 |
2010年 | 243篇 |
2009年 | 406篇 |
2008年 | 391篇 |
2007年 | 392篇 |
2006年 | 340篇 |
2005年 | 281篇 |
2004年 | 268篇 |
2003年 | 225篇 |
2002年 | 180篇 |
2001年 | 177篇 |
2000年 | 160篇 |
1999年 | 139篇 |
1998年 | 131篇 |
1997年 | 115篇 |
1996年 | 74篇 |
1995年 | 50篇 |
1994年 | 51篇 |
1993年 | 50篇 |
1992年 | 29篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 2篇 |
排序方式: 共有6615条查询结果,搜索用时 24 毫秒
81.
82.
Tomoo Suzuki Yoshihiro Ichihara Masaru Yamada Kenzo Tonomura 《Bioscience, biotechnology, and biochemistry》2013,77(4):747-756
Pseudomonas 0–3 strain which was isolated from soil can grow on polyvinyl alcohol (PVA) as a sole carbon source. When 0.5 per cent of PVA (500, 1500 or 2000) was employed as the carbon source in the culture medium, PVA was almost completely lost from the culture fluid after a week and the concentration of total organic carbon measured by a TOC analyzer decreased from the initial value of about 2700 ppm to 250~300 ppm after 7~10 days culture. This bacterium was found to produce and secrete an inducible enzyme which degrade PVA. The way by which this enzyme degrades PVA was examined and the results were obtained which suggested that PVA was broken down oxidatively in a way of endowise splitting. However, the mechanism of PVA degradation has not been clarified yet. The optimum pH and temperature for enzyme activity were examined and they were 7.5~8.5 and 35~45°C, respectively. Morphological and biological characteristics of this bacterium were examined and it was similar to a strain of Pseudomonas boreopolis. 相似文献
83.
Conversion of the Extracellular Dextransucrase Isoenzymes from Leuconostoc mesenteroides NRRL B-1299
Effect of oxygen tension on l-lysine, l-threonine and l-isoleucine accumulation was investigated. Sufficient supply of oxygen to satisfy the cell’s oxygen demand was essential for the maximum production in each fermentation. The dissolved oxygen level must be controlled at greater than 0.01 atm in every fermentation, and the optimum redox potentials of culture media were above ?170 mV in l-lysine and l-threonine and above ?180 mV in l-isoleucine fermentations. The maximum concentrations of the products were 45.5 mg/ml for l-lysine, 10.3 mg/ml for l-threonine and 15.1 mg/ml for l-isoleucine. The degree of the inhibition due to oxygen limitation was slight in the fermentative production of l-lysine, l-threonine and l-isoleucine, whose biosynthesis is initiated with l-aspartic acid, in contrast to the accumulation of l-proline, l-glutamine and l-arginine, which is biosynthesized by way of l-glutamic acid. 相似文献
84.
Emilie Widemann Laurence Miesch Rapha?l Lugan Emilie Holder Clément Heinrich Yann Aubert Michel Miesch Franck Pinot Thierry Heitz 《The Journal of biological chemistry》2013,288(44):31701-31714
Jasmonates (JAs) are a class of signaling compounds that mediate complex developmental and adaptative responses in plants. JAs derive from jasmonic acid (JA) through various enzymatic modifications, including conjugation to amino acids or oxidation, yielding an array of derivatives. The main hormonal signal, jasmonoyl-l-isoleucine (JA-Ile), has been found recently to undergo catabolic inactivation by cytochrome P450-mediated oxidation. We characterize here two amidohydrolases, IAR3 and ILL6, that define a second pathway for JA-Ile turnover during the wound response in Arabidopsis leaves. Biochemical and genetic evidence indicates that these two enzymes cleave the JA-Ile signal, but act also on the 12OH-JA-Ile conjugate. We also show that unexpectedly, the abundant accumulation of tuberonic acid (12OH-JA) after wounding originates partly through a sequential pathway involving (i) conjugation of JA to Ile, (ii) oxidation of the JA-Ile conjugate, and (iii) cleavage under the action of the amidohydrolases. The coordinated actions of oxidative and hydrolytic branches in the jasmonate pathway highlight novel mechanisms of JA-Ile hormone turnover and redefine the dynamic metabolic grid of jasmonate conversion in the wound response. 相似文献
85.
Debarati Basu Yan Liang Xiao Liu Klaus Himmeldirk Ahmed Faik Marcia Kieliszewski Michael Held Allan M. Showalter 《The Journal of biological chemistry》2013,288(14):10132-10143
Although plants contain substantial amounts of arabinogalactan proteins (AGPs), the enzymes responsible for AGP glycosylation are largely unknown. Bioinformatics indicated that AGP galactosyltransferases (GALTs) are members of the carbohydrate-active enzyme glycosyltransferase (GT) 31 family (CAZy GT31) involved in N- and O-glycosylation. Six Arabidopsis GT31 members were expressed in Pichia pastoris and tested for enzyme activity. The At4g21060 gene (named AtGALT2) was found to encode activity for adding galactose (Gal) to hydroxyproline (Hyp) in AGP protein backbones. AtGALT2 specifically catalyzed incorporation of [14C]Gal from UDP-[14C]Gal to Hyp of model substrate acceptors having AGP peptide sequences, consisting of non-contiguous Hyp residues, such as (Ala-Hyp) repetitive units exemplified by chemically synthesized (AO)7 and anhydrous hydrogen fluoride-deglycosylated d(AO)51. Microsomal preparations from Pichia cells expressing AtGALT2 incorporated [14C]Gal to (AO)7, and the resulting product co-eluted with (AO)7 by reverse-phase HPLC. Acid hydrolysis of the [14C]Gal-(AO)7 product released 14C-radiolabel as Gal only. Base hydrolysis of the [14C]Gal-(AO)7 product released a 14C-radiolabeled fragment that co-eluted with a Hyp-Gal standard after high performance anion-exchange chromatography fractionation. AtGALT2 is specific for AGPs because substrates lacking AGP peptide sequences did not act as acceptors. Moreover, AtGALT2 uses only UDP-Gal as the substrate donor and requires Mg2+ or Mn2+ for high activity. Additional support that AtGALT2 encodes an AGP GALT was provided by two allelic AtGALT2 knock-out mutants, which demonstrated lower GALT activities and reductions in β-Yariv-precipitated AGPs compared with wild type plants. Confocal microscopic analysis of fluorescently tagged AtGALT2 in tobacco epidermal cells indicated that AtGALT2 is probably localized in the endomembrane system consistent with its function. 相似文献
86.
The jasmonic acid signaling pathway is linked to auxin homeostasis through the modulation of YUCCA8 and YUCCA9 gene expression 总被引:1,自引:0,他引:1
87.
88.
89.
Stephen Mosher Heike Seybold Patricia Rodriguez Mark Stahl Kelli A. Davies Sajeewani Dayaratne Santiago A. Morillo Michael Wierzba Bruno Favery Harald Keller Frans E. Tax Birgit Kemmerling 《The Plant journal : for cell and molecular biology》2013,73(3):469-482
The tyrosine‐sulfated peptides PSKα and PSY1 bind to specific leucine‐rich repeat surface receptor kinases and control cell proliferation in plants. In a reverse genetic screen, we identified the phytosulfokine (PSK) receptor PSKR1 as an important component of plant defense. Multiple independent loss‐of‐function mutants in PSKR1 are more resistant to biotrophic bacteria, show enhanced pathogen‐associated molecular pattern responses and less lesion formation after infection with the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. By contrast, pskr1 mutants are more susceptible to necrotrophic fungal infection with Alternaria brassicicola, show more lesion formation and fungal growth which is not observed on wild‐type plants. The antagonistic effect on biotrophic and necrotrophic pathogen resistance is reflected by enhanced salicylate and reduced jasmonate responses in the mutants, suggesting that PSKR1 suppresses salicylate‐dependent defense responses. Detailed analysis of single and multiple mutations in the three paralogous genes PSKR1, ‐2 and PSY1‐receptor (PSY1R) determined that PSKR1 and PSY1R, but not PSKR2, have a partially redundant effect on plant immunity. In animals and plants, peptide sulfation is catalyzed by a tyrosylprotein sulfotransferase (TPST). Mutants lacking TPST show increased resistance to bacterial infection and increased susceptibility to fungal infection, mimicking the triple receptor mutant phenotypes. Feeding experiments with PSKα in tpst‐1 mutants partially restore the defense‐related phenotypes, indicating that perception of the PSKα peptide has a direct effect on plant defense. These results suggest that the PSKR subfamily integrates growth‐promoting and defense signals mediated by sulfated peptides and modulates cellular plasticity to allow flexible adjustment to environmental changes. 相似文献