全文获取类型
收费全文 | 2303篇 |
免费 | 171篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 30篇 |
2021年 | 59篇 |
2020年 | 31篇 |
2019年 | 53篇 |
2018年 | 78篇 |
2017年 | 52篇 |
2016年 | 92篇 |
2015年 | 117篇 |
2014年 | 156篇 |
2013年 | 169篇 |
2012年 | 222篇 |
2011年 | 213篇 |
2010年 | 141篇 |
2009年 | 99篇 |
2008年 | 153篇 |
2007年 | 151篇 |
2006年 | 116篇 |
2005年 | 111篇 |
2004年 | 107篇 |
2003年 | 75篇 |
2002年 | 69篇 |
2001年 | 7篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 17篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有2474条查询结果,搜索用时 15 毫秒
141.
Angela Chambery Valeria Severino Antimo Di Maro Antimo D’Aniello Menotti Ruvo Augusto Parente 《Amino acids》2010,38(4):1031-1041
Thyrotropin-releasing hormone (TRH) is involved in a wide range of biological responses. It has a central role in the endocrine
system and regulates several neurobiological activities. In the present study, a rapid, sensitive and selective liquid chromatography–mass
spectrometry method for the identification and quantification of TRH has been developed. The methodology takes advantage of
the specificity of the selected-ion monitoring acquisition mode with a limit of detection of 1 fmol. Furthermore, the MS/MS
fragmentation pattern of TRH has been investigated to develop a selected reaction monitoring (SRM) method that allows the
detection of a specific b2 product ion at m/z 249.1, corresponding to the N-terminus dipeptide pyroglutamic acid–histidine. The method has been tested on rat hypothalami to evaluate its suitability
for the detection within very complex biological samples. 相似文献
142.
Over the last two decades, the importance of conserving genetic resources has received increasing attention. In this context
the role of home gardens as repositories of biological diversity has been acknowledged but still a comprehensive, interdisciplinary
investigation of their agro-biodiversity is lacking. Home gardens, whether found in rural or urban areas, are characterized
by a structural complexity and multifunctionality which enables the provision of different benefits to ecosystems and people.
Studies carried out in various countries demonstrate that high levels of inter- and intra-specific plant genetic diversity,
especially in terms of traditional crop varieties and landraces, are preserved in home gardens. Families engage in food production
for subsistence or small-scale marketing and the variety of crops and wild plants provides nutritional benefits. At the same
time, home gardens are important social and cultural spaces where knowledge related to agricultural practices is transmitted
and through which households may improve their income and livelihoods. The present article summarizes available literature
on the biological and cultural significance of agro-biodiversity in home gardens. It discusses future constraints and opportunities
in home garden research, in the prospect of defining and promoting their role in conservation of agricultural biodiversity
and cultural heritage. 相似文献
143.
New single-cell recordings show that humans do have mirror neurons, and in more brain regions than previously suspected. Some action-execution neurons were seen to be inhibited during observation, possibly preventing imitation and helping self/other discrimination. 相似文献
144.
145.
146.
Valeria Mozzetti Franck Grattepanche Déborah Moine Bernard Berger Enea Rezzonico Leo Meile Fabrizio Arigoni Christophe Lacroix 《Microbial cell factories》2010,9(1):60
Background
Oxidative stress can severely compromise viability of bifidobacteria. Exposure of Bifidobacterium cells to oxygen causes accumulation of reactive oxygen species, mainly hydrogen peroxide, leading to cell death. In this study, we tested the suitability of continuous culture under increasing selective pressure combined with immobilized cell technology for the selection of hydrogen peroxide adapted Bifidobacterium cells. Cells of B. longum NCC2705 were immobilized in gellan-xanthan gum gel beads and used to continuously ferment MRS medium containing increasing concentration of H2O2 from 0 to 130 ppm. 相似文献147.
Boeris V Farruggia B Nerli B Romanini D Picó G 《International journal of biological macromolecules》2007,41(3):286-294
Complexes formation between two model proteins (catalase and chymotrypsin) and polyelectrolytes (polyvinyl sulphonate and polyacrilic acid) and a non-charged flexible chain polymer (PCF) as polyethylene propylene oxide (molecular mass 8400) was studied by a spectroscopy technique combination: UV absorption, fluorescence emission and circular dichroism. All the polymers increase the protein surface hydrophobicity (S(0)) parameter value as a proof of the modification of the protein surface exposed to the solvent. Chymotrypsin showed an increase in its biological activity in polymer presence, which suggests a change in the superficial microenvironment. The decrease in the biological activity of catalase might be due to a competition between the polymer and the substrate. This result agrees with the polymer effect on the catalase superficial hydrophobic area. It was found that, when flexible chain polymers increase protein stability and the enzymatic activity they could be used to isolate this enzyme without inducing loss of protein enzymatic activity. Our findings suggest that the interactions are dependent on the protein physico-chemical parameters such as: isoelectric pH, hydrophobic surface area, etc. 相似文献
148.
149.
A novel pathway of HMGB1-mediated inflammatory cell recruitment that requires Mac-1-integrin 总被引:3,自引:0,他引:3
Orlova VV Choi EY Xie C Chavakis E Bierhaus A Ihanus E Ballantyne CM Gahmberg CG Bianchi ME Nawroth PP Chavakis T 《The EMBO journal》2007,26(4):1129-1139
High-mobility group box 1 (HMGB1) is released extracellularly upon cell necrosis acting as a mediator in tissue injury and inflammation. However, the molecular mechanisms for the proinflammatory effect of HMGB1 are poorly understood. Here, we define a novel function of HMGB1 in promoting Mac-1-dependent neutrophil recruitment. HMGB1 administration induced rapid neutrophil recruitment in vivo. HMGB1-mediated recruitment was prevented in mice deficient in the beta2-integrin Mac-1 but not in those deficient in LFA-1. As observed by bone marrow chimera experiments, Mac-1-dependent neutrophil recruitment induced by HMGB1 required the presence of receptor for advanced glycation end products (RAGE) on neutrophils but not on endothelial cells. In vitro, HMGB1 enhanced the interaction between Mac-1 and RAGE. Consistently, HMGB1 activated Mac-1 as well as Mac-1-mediated adhesive and migratory functions of neutrophils in a RAGE-dependent manner. Moreover, HMGB1-induced activation of nuclear factor-kappaB in neutrophils required both Mac-1 and RAGE. Together, a novel HMGB1-dependent pathway for inflammatory cell recruitment and activation that requires the functional interplay between Mac-1 and RAGE is described here. 相似文献
150.
Genetic Modification of the Penicillin G Acylase Surface To Improve Its Reversible Immobilization on Ionic Exchangers 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tamara Montes Valeria Grazú Fernando Lpez-Gallego Juan A. Hermoso Jose L. García Isabel Manso Beatriz Galn Ramn Gonzlez Roberto Fernndez-Lafuente Jos M. Guisn 《Applied microbiology》2007,73(1):312-319
A new mutant of the industrial enzyme penicillin G acylase (PGA) from Escherichia coli has been designed to improve its reversible immobilization on anionic exchangers (DEAE- or polyethyleneimine [PEI]-coated agarose) by assembling eight new glutamic residues distributed homogeneously through the enzyme surface via site-directed mutagenesis. The mutant PGA is produced and processed in vivo as is the native enzyme. Moreover, it has a similar specific activity to and shows the same pH activity profile as native PGA; however, its isoelectric point decreased from 6.4 to 4.3. Although the new enzyme is adsorbed on both supports, the adsorption was even stronger when supports were coated with PEI, allowing us to improve the enzyme stability in organic cosolvents. The use of restrictive conditions during the enzyme adsorption on anionic exchangers (pH 5 and high ionic strength) permitted us to still further increase the strength of adsorption and the enzyme stability in the presence of organic solvents, suggesting that these conditions allow the penetration of the enzyme inside the polymeric beds, thus becoming fully covered with the polymer. After the enzyme inactivation, it can be desorbed to reuse the support. The possibility to improve the immobilization properties on an enzyme by site-directed mutagenesis of its surface opens a promising new scenario for enzyme engineering. 相似文献