全文获取类型
收费全文 | 712篇 |
免费 | 74篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 394篇 |
金属工艺 | 5篇 |
机械仪表 | 11篇 |
建筑科学 | 25篇 |
能源动力 | 12篇 |
轻工业 | 137篇 |
石油天然气 | 2篇 |
无线电 | 28篇 |
一般工业技术 | 82篇 |
冶金工业 | 15篇 |
原子能技术 | 1篇 |
自动化技术 | 70篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 125篇 |
2021年 | 104篇 |
2020年 | 26篇 |
2019年 | 24篇 |
2018年 | 41篇 |
2017年 | 26篇 |
2016年 | 37篇 |
2015年 | 40篇 |
2014年 | 44篇 |
2013年 | 45篇 |
2012年 | 37篇 |
2011年 | 42篇 |
2010年 | 33篇 |
2009年 | 31篇 |
2008年 | 27篇 |
2007年 | 11篇 |
2006年 | 15篇 |
2005年 | 23篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有786条查询结果,搜索用时 15 毫秒
651.
Effect of Dietary Components from Antarctic Krill on Atherosclerosis in apoE‐Deficient Mice
下载免费PDF全文
![点击此处可从《Molecular nutrition & food research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
652.
653.
654.
Christoph von Ballmoos Irina Smirnova Federica Poiana Nathalie Gonska Hsin-Yang Chang Robert B. Gennis Peter Brzezinski Pia Ädelroth 《Israel journal of chemistry》2017,57(5):424-436
The ba3 cytochrome c oxidase from Thermus thermophilus is a B-type oxygen-reducing heme-copper oxidase and a proton pump. It uses only one proton pathway for transfer of protons to the catalytic site, the KB pathway. It was previously shown that the ba3 oxidase has an overall similar reaction sequence to that in mitochondrial-like A-type oxidases. However, the timing of loading the pump site, and formation and decay of catalytic intermediates is different in the two types of oxidases. In the present study, we have investigated variants in which two amino acids of the KB proton pathway leading to the catalytic site were exchanged; Tyr-248 (located ∼23 Å below the active site towards the cytoplasm) in subunit I (Y248T) and Glu-15 (∼26 Å below the active site, ∼16 Å from Tyr-248) in subunit II (E15IIQ). Even though the overall catalytic turnover in these two variants is similar and very low (<1 % of wildtype), the substitutions had distinctly different effects on the kinetics of proton transfer to the catalytic site. The results indicate that the Glu-15II is the only essentially crucial residue of the KB pathway, but that the Tyr-248 also plays a distinct role in defining an internal proton donor and controlling the dynamics of proton transfer to the pump site and the catalytic site. 相似文献
655.
Emanuela Pietrantoni Federica Del Chierico Giuliano Rigon Pamela Vernocchi Guglielmo Salvatori Melania Manco Fabrizio Signore Lorenza Putignani 《International journal of molecular sciences》2014,15(5):8024-8036
Polyunsaturated fatty acids (PUFAs) are required to maintain the fluidity, permeability and integrity of cell membranes. Maternal dietary supplementation with ω-3 PUFAs during pregnancy has beneficial effects, including increased gestational length and reduced risk of pregnancy complications. Significant amounts of ω-3 docosahexaenoic acid (DHA) are transferred from maternal to fetal blood, hence ensuring high levels of DHA in the placenta and fetal bloodstream and tissues. Fetal DHA demand increases exponentially with gestational age, especially in the third trimester, due to fetal development. According to the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), a daily intake of DHA is recommended during pregnancy. Omega-3 PUFAs are involved in several anti-inflammatory, pro-resolving and anti-oxidative pathways. Several placental disorders, such as intrauterine growth restriction, premature rupture of membranes (PROM) and preterm-PROM (pPROM), are associated with placental inflammation and oxidative stress. This pilot study reports on a preliminary evaluation of the significance of the daily DHA administration on PROM and pPROM events in healthy pregnant women. Further extensive clinical trials will be necessary to fully elucidate the correlation between DHA administration during pregnancy and PROM/pPROM occurrence, which is related in turn to gestational duration and overall fetal health. 相似文献
656.
657.
Federica Ianni Maura Marinozzi Stefania Scorzoni Benedetto Natalini 《International Journal of Food Properties》2016,19(4):752-759
Onion cultivars with low pungency have been increasing in popularity because they are more attractive for fresh, uncooked use. The pyruvic acid amount is commonly used as a measure of onion pungency. For the first time the validation of a reversed-phase high-performance liquid chromatography method for the quantitative analysis of pyruvic acid in onion extracts was carried out. The established chromatography method based on the use of a 50 mM phosphate buffer (pH 2.5) eluent system provided good precision (RSD% in the range of 1.25–1.29, in the long-period) and accuracy (recovery% in the range of 97.70–111.62, in the long-period) as well as appreciably low limit of detection and limit of quantitation values (11.03 and 33.41 ng/mL, respectively). The validated method proved successful in the analysis of the onion extract from Dorata di Parma cultivar after a preliminary solid-phase extraction step. A significant adherence with results from previous spectrophotometric determinations turned out. 相似文献
658.
Junghyuk Ko Martin B. Jun Gabriele Gilardi Edmund Haslam Edward J. Park 《Mechatronics》2011,21(7):1190-1202
This paper presents biomimetic control of an anthropomorphic artificial finger actuated by three antagonistic shape memory alloy (SMA) muscle pairs that are each configured in a dual spring-biased configuration. This actuation system forms the basis for biomimetic tendon-driven flexion/extension of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of the artificial finger, as well as the abduction/adduction of its MCP joint. This work focuses on the design and experimental verification of a new fuzzy pulse-width-modulated proportional-integral-derivative (i.e. fuzzy PWM-PID) controller that is capable of realizing cocontraction of the SMA muscle pairs, as well as online tuning of the PID gains to deal with system nonlinearities and parameter uncertainties. The main contribution of this paper is the proposed biomimetic cocontraction control strategy, which co-activates the antagonistic muscle pairs as a synergistic functional unit. It emulates a similar strategy in neural control, called “common drive,” employed by the central nervous system (CNS). In order to maintain a desired position of a joint, the corresponding agonistic muscle pairs are cocontracted by the CNS and stiffen the joint. The synthesis and parametric analysis of the proposed controller are carried out via numerical simulations using a dynamic model of the system. The performance advantage of the cocontracting fuzzy PWM-PID controller over the original PWM-PID controller is shown by both numerical and experimental results. A successful application of the new controller to fingertip trajectory tracking tasks using the MCP joint’s flexion/extension and abduction/adduction is also described. 相似文献
659.
Elena Macerata Annalisa Ossola Walter Panzeri Marco Giola Federica Faroldi Dario Alberto Tinonin 《溶剂提取与离子交换》2018,36(1):41-53
Within the actinide and lanthanide co-extraction strategy, three rigidified diglycolamides, namely 2,6-bis (N-dodecyl-carboxamide)-4-oxo-4H-pyran (1), 2,6-bis-[N-(4-tert-butylphenyl)carboxamide]-4-oxo-4H-pyran (2), 2,6-?bis[(N-docecyl-N-methyl)carboxamide]-?4-methoxy-?tetrahydro-pyran (3), were synthesized. Moreover, the effect of structural rigidification on Am(III) and Eu(III) extraction under different conditions was investigated. The carboxamide extractant 3 resembles the extracting behavior of N,N,N′,N′‐tetraoctyl diglycolamide (TODGA) in terms of efficiency and affinity within the lanthanide family, together with fast kinetics and satisfactory cation back-extraction. The presence of 1-octanol in the diluent mixture strongly affects the ligand stability. Moreover, despite the low extraction efficiency showed by 1 and 2, all the three ligands exhibit a higher affinity for Am with respect to TODGA, resulting in a lower lanthanide/Americium separation factor, of around 4 for ligand 3 and close to 1 for ligands 1 and 2. 相似文献
660.
Dr. Paola Rota Dr. Paolo La Rocca Dr. Marco Piccoli Dr. Marco Montefiori Dr. Federica Cirillo Prof. Lars Olsen Prof. Marica Orioli Prof. Pietro Allevi Prof. Luigi Anastasia 《ChemMedChem》2018,13(3):236-240
Neuraminidase activity is essential for the infection and propagation of paramyxoviruses, including human parainfluenza viruses (hPIVs) and the Newcastle disease virus (NDV). Thus, many inhibitors have been developed based on the 2‐deoxy‐2,3‐didehydro‐d ‐N‐acetylneuraminic acid inhibitor (DANA) backbone. Along this line, herein we report a series of neuraminidase inhibitors, having C4 (p‐toluenesulfonamido and azido substituents) and C5 (N‐perfluorinated chains) modifications to the DANA backbone, resulting in compounds with 5‐ to 15‐fold greater potency than the currently most active compound, the N‐trifluoroacetyl derivative of DANA (FANA), toward the NDV hemagglutinin‐neuraminidase (NDV‐HN). Remarkably, these inhibitors were found to be essentially inactive against the human sialidase NEU3, which is present on the outer layer of the cell membrane and is highly affected by the current NDV inhibitor FANA. 相似文献