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排序方式: 共有303条查询结果,搜索用时 15 毫秒
301.
José Manuel Borrero-de Acuña Izabook Gutierrez-Urrutia Cristian Hidalgo-Dumont Carla Aravena-Carrasco Matias Orellana-Saez Nestor Palominos-Gonzalez Jozef B. J. H. van Duuren Viktoria Wagner Lars Gläser Judith Becker Michael Kohlstedt Flavia C. Zacconi Christoph Wittmann Ignacio Poblete-Castro 《Microbial biotechnology》2021,14(6):2385-2402
Lignin-based aromatics are attractive raw materials to derive medium-chain length poly(3-hydroxyalkanoates) (mcl-PHAs), biodegradable polymers of commercial value. So far, this conversion has exclusively used the ortho-cleavage route of Pseudomonas putida KT2440, which results in the secretion of toxic intermediates and limited performance. Pseudomonas putida H exhibits the ortho- and the meta-cleavage pathways where the latter appears promising because it stoichiometrically yields higher levels of acetyl-CoA. Here, we created a double-mutant H-ΔcatAΔA2 that utilizes the meta route exclusively and synthesized 30% more PHA on benzoate than the parental strain but suffered from catechol accumulation. The single deletion of the catA2 gene in the H strain provoked a slight attenuation on the enzymatic capacity of the ortho route (25%) and activation of the meta route by nearly 8-fold, producing twice as much mcl-PHAs compared to the wild type. Inline, the mutant H-ΔcatA2 showed a 2-fold increase in the intracellular malonyl-CoA abundance – the main precursor for mcl-PHAs synthesis. As inferred from flux simulation and enzyme activity assays, the superior performance of H-ΔcatA2 benefited from reduced flux through the TCA cycle and malic enzyme and diminished by-product formation. In a benzoate-based fed-batch, P. putida H-ΔcatA2 achieved a PHA titre of 6.1 g l–1 and a volumetric productivity of 1.8 g l–1 day–1. Using Kraft lignin hydrolysate as feedstock, the engineered strain formed 1.4 g l- 1 PHA. The balancing of carbon flux between the parallel catechol-degrading routes emerges as an important strategy to prevent intermediate accumulation and elevate mcl-PHA production in P. putida H and, as shown here, sets the next level to derive this sustainable biopolymer from lignin hydrolysates and aromatics. 相似文献
302.
Lara Clemens Mikhail Kutuzov Kristina Viktoria Bayer Jesse Goyette Jun Allard Omer Dushek 《Biophysical journal》2021,120(10):2054-2066
Immune receptors signal by recruiting (or tethering) enzymes to their cytoplasmic tails to catalyze reactions on substrates within reach. This is the case for the phosphatase SHP-1, which, upon tethering to inhibitory receptors, dephosphorylates diverse substrates to control T cell activation. Precisely how tethering regulates SHP-1 activity is incompletely understood. Here, we measure binding, catalysis, and molecular reach for tethered SHP-1 reactions. We determine the molecular reach of SHP-1 to be 13.0 nm, which is longer than the estimate from the allosterically active structure (5.3 nm), suggesting that SHP-1 can achieve a longer reach by exploring multiple active conformations. Using modeling, we show that when uniformly distributed, receptor-SHP-1 complexes can only reach 15% of substrates, but this increases to 90% when they are coclustered. When within reach, we show that membrane recruitment increases the activity of SHP-1 by a 1000-fold increase in local concentration. The work highlights how molecular reach regulates the activity of membrane-recruited SHP-1 with insights applicable to other membrane-tethered reactions. 相似文献
303.
Viktoria Takacs Piotr Zduniak Marek Panek Piotr Tryjanowski 《Central European Journal of Biology》2009,4(3):427-433
Winter body mass of the European hare Lepus europaeus Pallas 1778 was analyzed with a special focus on changes induced by handling. Data were obtained from large scale translocation
(net catchments) during 1960–1980 in Poland. The influence of handling was compared using the mass of first-time captured
and repeatedly-captured hares, and, in case of repeated capture, individuals’ mass changes were investigated. The average
body mass ranged from 2.1 kg to 5.0 kg. Generally, fewer factors influenced the hare’s body mass than expected. Body mass
was related to age and winter precipitation, while the date of catching, sex and temperature did not have an effect. Body
mass of first-captured hares were significantly higher than the re-captured ones (3.99±0.42 vs. 3.88±0.48, mean ±SD). Body
mass change between captures was related to the date of the first capture, and the duration between the first capture and
re-capture. Following the initial capture, a slight (2.8±2.6), but significant decrease in body weight occurred. Thus, the
handling of hares should be used with caution during studies or management of the species. 相似文献