全文获取类型
收费全文 | 516篇 |
免费 | 30篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 149篇 |
金属工艺 | 2篇 |
机械仪表 | 2篇 |
建筑科学 | 20篇 |
能源动力 | 12篇 |
轻工业 | 187篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 14篇 |
一般工业技术 | 49篇 |
冶金工业 | 43篇 |
自动化技术 | 59篇 |
出版年
2024年 | 6篇 |
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 21篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 34篇 |
2012年 | 36篇 |
2011年 | 43篇 |
2010年 | 31篇 |
2009年 | 28篇 |
2008年 | 35篇 |
2007年 | 31篇 |
2006年 | 20篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有546条查询结果,搜索用时 15 毫秒
41.
42.
In this paper we study Galois embedding problems given by central extensions with cyclic kernel. We find a new expression for the obstruction to the solvability of these embedding problems in terms of Galois symbols. We also give a method to construct the solutions when these problems are solvable. We find a solution from a coordinate of the norm of an adequate element in a generalized Clifford algebra. 相似文献
43.
Bruno Almeida Dr. Jesús Joglar María Jesús Luque Rojas Juan Manuel Decara Francisco Javier Bermúdez‐Silva Dr. Manuel Macias‐González Dr. Montserrat Fitó Miguel Romero‐Cuevas Dr. Magí Farré Dr. María Isabel Covas Dr. Fernando Rodríguez de Fonseca Dr. Rafael de la Torre 《ChemMedChem》2010,5(10):1781-1787
A series of fatty acid amides of 3,4‐methylenedioxymethamphetamine (MDMA) catechol metabolites were synthesized in order to evaluate their biological activities. Upon administration, all synthesized compounds resulted in negative modulation of food intake in rats. The most active compounds have affinity for the CB1 receptor and/or PPAR‐α; part of their biological activity may be caused by these double interactions. 相似文献
44.
Rivia D. A. Amaral Benedito C. Benedetti Montserrat Pujolà Isabel Achaerandio Mara L. B. Bachelli 《Food and Bioprocess Technology》2016,9(10):1794-1801
The effect of ultrasound (US) (40 kHz, 200 W, 3 min), blanching (85 °C, 3.5 min), and the combination of both methods was evaluated on the quality of vacuum-packaged potato strips stored at 3 ± 1 °C for up to 10 days. For this study, two cultivars of potatoes were assessed. For blanched Agata samples, the lightness (L*) decreased over 12 % (p < 0.05). Moreover, their hue increased up to 100, obtaining lesser yellow potato strips. In contrast, US did not affect the hue values. The losses of firmness of blanched potato strips were notable (35 % for Agata and 51 % for Agria), whereas US did not change this property (p < 0.05). Nevertheless, no significant differences were found in the total starch content at 10 days. Agata and Agria showed different metabolic behaviors of sucrose in the refrigerated storage. Therefore, Agria cultivar retained better color after frying. These results suggest that US had less impact on color and improve the firmness in vacuum-packaged potato strips with no added chemicals. 相似文献
45.
Lessening polygalacturonase activity in a commercial enzyme preparation by exposure to pulsed electric fields 总被引:1,自引:0,他引:1
Joaquín?Giner Vicente?Gimeno Montserrat?Palomes Gustavo?V.?Barbosa-Cánovas Olga?MartínEmail author 《European Food Research and Technology》2003,217(1):43-48
The effect of high-intensity pulsed electric field (HIPEF) treatments on polygalacturonase (PG) activity in an aqueous solution of a commercial enzyme preparation was evaluated. HIPEF treatments reduced PG activity notably. Exponentially decaying pulses of 40 and 160 µs generated by a laboratory scale device were applied in a batch processing and bipolar mode. Electric fields ranged from 5.18 to 19.39 kV/cm. The number of pulses ranged up to 400. Temperature was always below 25 °C. Maximum inactivation of PG activity (98%) required 32.4 ms HIPEF treatment at 10.28 kV/cm. PG activity depleted exponentially because of HIPEF treatments. The first order rate constants ranged from 32 to 590 µs -1 and increased exponentially with electric field intensity. PG activity decreased exponentially with input electric energy density. 相似文献
46.
Peter VialAuthor Vitae Beata WysockiAuthor VitaeTadeusz WysockiAuthor Vitae Montserrat RosAuthor VitaeDavid StirlingAuthor Vitae 《Computers & Electrical Engineering》2012,38(4):994-1009
This study investigates the effect of multiple sources using STS across a Time-Hopping-PPM Modulation that is over an UWB Saleh-Valenzuela channel with each source using two transmit antennas. We model and analyze this system, showing that the presence of such MAI results in a significant degradation in BER performance. Simulation results show that for strong signal strength of interfering MAI signals degradation in BER performance is observed for the cases where we have five and 10 distinct MAI sources present when using Walsh-Hadamard thirty two chip spreading sequences. Using simulation, we investigate the use of other sets of orthogonal spreading sequences with improved cross correlation properties and find that for some sequences a significant improvement is seen compared to Walsh-Hadamard sequences when they are similarly misaligned. We show that MAI degrades the BER performance of such systems and that selection of improved cross correlation spreading code sequence sets improves BER. 相似文献
47.
Montserrat López‐Martínez Marco Carminati Ismael Díez‐Pérez Fausto Sanz Pau Gorostiza 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(36)
Electron transfer in proteins is essential in crucial biological processes. Although the fundamental aspects of biological electron transfer are well characterized, currently there are no experimental tools to determine the atomic‐scale electronic pathways in redox proteins, and thus to fully understand their outstanding efficiency and environmental adaptability. This knowledge is also required to design and optimize biomolecular electronic devices. In order to measure the local conductance of an electrode surface immersed in an electrolyte, this study builds upon the current–potential spectroscopic capacity of electrochemical scanning tunneling microscopy, by adding an alternating current modulation technique. With this setup, spatially resolved, differential electrochemical conductance images under bipotentiostatic control are recorded. Differential electrochemical conductance imaging allows visualizing the reversible oxidation of an iron electrode in borate buffer and individual azurin proteins immobilized on atomically flat gold surfaces. In particular, this method reveals submolecular regions with high conductance within the protein. The direct observation of nanoscale conduction pathways in redox proteins and complexes enables important advances in biochemistry and bionanotechnology. 相似文献
48.
Relaxation processes at temperatures above 20 °C in semicrystalline polyethylene-terephthalate have been studied using thermally stimulated depolarization currents (TSDC). The discharge curve shows three relaxation peaks (c, c and *) whose positions and intensities depend on the polarization conditions and the crystallinity. Relaxations c and c are heteropolar, while * may be homopolar or heteropolar according to the polarization temperature used. The effect of the crystallinity on these relaxations has been analysed by the thermal steps stimulation (TSS) method applied to an amorphous sample. Results show that c is fundamentally a dipolar relaxation associated with the amorphous interlamellar zone. The relaxation c is associated with the release of a free charge trapped in the amorphous regions, and * is a Maxwell–Wagner–Sillars relaxation associated with crystalline – amorphous interphases. For polarization temperatures above 150 °C, two relaxations are observed only as a consequence of overlapping C and * relaxations. © 1998 Chapman & Hall 相似文献
49.
Francisco Hernndez-Beltrn Juan Carlos Moreno-Mayorga María de Lourdes Guzmn-Castillo Juan Navarrete-Bolaos Montserrat Gonzlez-Gonzlez Brent E. Handy 《Applied Catalysis A: General》2003,240(1-2):41-51
The evolution of the properties of a REUSY zeolite contained in a fluid cracking catalyst was investigated under laboratory steam deactivation procedures and in age fractions of the corresponding equilibrium catalyst (Ecat). The aging pattern, defined by the evolution of the zeolite surface area (ZSA) related to the decrease of the unit cell size (UCS), was similar between lab-steamed zeolites and Ecat fractions. A sharp drop in ZSA occurred at ca. 2.430 nm UCS. A study done by FT-IR spectroscopy suggested that zeolite dealumination initially took place more extensively on the sodalite cages and double six-member rings (D6R) of the structure and that the final collapse of the zeolite framework occurred through destruction of the 12-member rings (12M). This can be explained by a crystal fracture and break down process and disassembling of the sodalite cages in the faujasite structure. NH3 microcalorimetry showed that strong acid sites in faujasites are destroyed by steam aging, but this effect does not lead to a reduction in the cracking activity of the Ecat form. The microactivity test (MAT) showed that the specific activity declined sharply at 2.430 nm UCS. Differences in product selectivity were related to the extent of damage of the zeolite, extra-framework alumina and mesoporosity. While further aging canceled the effect attributed to extra-framework alumina differences attributed to mesoporosity increased. 相似文献
50.
Mireia Casanovas Irene Reyes-Resina Alejandro Lillo Jaume Lillo Raul Lpez-Arnau Jorge Camarasa Elena Escubedo Gemma Navarro Rafael Franco 《International journal of molecular sciences》2021,22(5)
Methamphetamine is, worldwide, one of the most consumed drugs of abuse. One important side effect is neurodegeneration leading to a decrease in life expectancy. The aim of this paper was to check whether the drug affects one of the receptors involved in neurodegeneration/neuroprotection events, namely the adenosine A2A receptor (A2AR). First, we noticed that methamphetamine does not affect A2A functionality if the receptor is expressed in a heterologous system. However, A2AR becomes sensitive to the drug upon complexes formation with the cannabinoid CB1 receptor (CB1R) and the sigma 1 receptor (σ1R). Signaling via both adenosine A2AR and cannabinoid CB1R was affected by methamphetamine in cells co-expressing the two receptors. In striatal primary cultures, the A2AR–CB1R heteromer complex was detected and methamphetamine not only altered its expression but completely blocked the A2AR- and the CB1R-mediated activation of the mitogen activated protein kinase (MAPK) pathway. In conclusion, methamphetamine, with the participation of σ1R, alters the expression and function of two interacting receptors, A2AR, which is a therapeutic target for neuroprotection, and CB1R, which is the most abundant G protein-coupled receptor (GPCR) in the brain. 相似文献