全文获取类型
收费全文 | 1112篇 |
免费 | 71篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 438篇 |
金属工艺 | 6篇 |
机械仪表 | 25篇 |
建筑科学 | 37篇 |
矿业工程 | 1篇 |
能源动力 | 38篇 |
轻工业 | 302篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 46篇 |
一般工业技术 | 168篇 |
冶金工业 | 11篇 |
原子能技术 | 2篇 |
自动化技术 | 98篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 89篇 |
2021年 | 98篇 |
2020年 | 33篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 39篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 52篇 |
2013年 | 75篇 |
2012年 | 70篇 |
2011年 | 77篇 |
2010年 | 79篇 |
2009年 | 62篇 |
2008年 | 57篇 |
2007年 | 44篇 |
2006年 | 40篇 |
2005年 | 27篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 28篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有1183条查询结果,搜索用时 15 毫秒
51.
Alberto Ballesteros Ester Laguna-Gutierrez Paula Cimavilla-Roman Maria Luisa Puertas Antonio Esteban-Cubillo Julio Santaren Miguel Angel Rodriguez-Perez 《应用聚合物科学杂志》2021,138(46):51373
In the present work blends of polystyrene (PS) with sepiolites have been produced using a melt extrusion process. The dispersion degree of the sepiolites in the PS has been analyzed by dynamic shear rheology and X-ray micro-computed tomography. Sepiolites treated with quaternary ammonium salts (O-QASEP) are better dispersed in the PS matrix than natural sepiolites (N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A percolated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEP and 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processes have a negative effect on the polymer architecture. They produce a reduction in the length of the polymeric chains, and they do not lead to a better dispersion of the particles in the polymer matrix. Foams have been produced using a gas dissolution foaming process, where a strong effect of the dispersion degree on the cellular structure of the different foams was found. The effects on the cellular structure obtained by using different types of sepiolites, different contents of sepiolites and different extrusion conditions have been analyzed. The foams produced with the formulations containing O-QASEP present the lowest cell size and the most homogeneous cellular structures. 相似文献
52.
Fernando de la Peña Moreno Gracia Patricia Blanch Gema Flores María Luisa Ruiz del Castillo 《Journal of the science of food and agriculture》2010,90(6):989-994
BACKGROUND: Although strawberry aroma is very complex, certain compounds have been described as main contributors, i.e. furanones, aldehydes, alcohols, sulfur compounds and particularly methyl and ethyl esters. In addition, strawberries possess potent antioxidant activity because of their high content of phenolic compounds. Among them, flavonols are highlighted as important antioxidant compounds in strawberry. The objective of this study was to assess the effect of methyl jasmonate (MJ) on the composition of the major contributors to aroma and on the content of certain flavonols in strawberry fruits. RESULTS: The levels of all studied volatile compounds were significantly affected by MJ treatment, though the individual effect differed according to the specific compound considered. Most of them increased significantly (P < 0.05), except methyl butanoate, which always showed higher levels in untreated strawberries. In contrast to aroma compounds, the change in the concentration of flavonols (i.e. myricetin, quercetin and kaempferol) was not significant in MJ‐treated strawberries. Considering the health‐promoting activity of these compounds, further investigations on the experimental conditions related to the treatment are required to control flavonol bioformation by means of MJ. CONCLUSION: The exogenous application of MJ vapour to strawberry enhances, in general, the production of the most relevant aroma‐active compounds. On the contrary, MJ treatment does not appear to influence the levels of myricetin, quercetin and kaempferol. Thus postharvest MJ treatment is proposed as an approach to obtain improved strawberry fruits in terms of sensory quality and health‐promoting properties. Copyright © 2010 Society of Chemical Industry 相似文献
53.
The biofilm-forming ability of 21 Listeria monocytogenes isolates, previously pulsotyped and corresponding to 16 strains, from different origins was evaluated using the Calgary Biofilm Device, at 37 °C. Biofilms of 4 selected strains were also produced either on pure cultures or on co-cultures with Pseudomonas aeruginosa (PAO1), at 12 °C and at 37 °C. For these biofilms, the minimum biofilm eradication concentrations (MBECs) of 4 commercial dairy sanitizers (1 alkyl amine acetate based--T99, 2 chlorine based--T66 and DD, and 1 phosphoric acid based--BP) were determined. Listeria monocytogenes biofilms grown, either at 37 °C or 12 °C, were able to achieve similar cell densities by using different incubation periods (24 h and 7 d, respectively). In co-culture biofilms, P. aeruginosa was the dominant species, either at 37 °C or at 12 °C, representing 99% of a total biofilm population of 6 to 7 log CFU/peg. Co-culture biofilms were generally less susceptible than L. monocytogenes pure cultures. More interestingly, the biofilms produced at 12 °C were usually less susceptible to the sanitizers than when produced at 37 °C. Single or co-culture biofilms of L. monocytogenes and PAO1, particularly produced at 12 °C, retrieved MBEC values for agents T99 and BP that were, at times, above the maximum in-use recommended concentrations for these agents. The results presented here reinforce the importance of the temperature used for biofilm formation, when susceptibility to sanitizers is being assessed. PRACTICAL APPLICATION: Since most food plants have cold wet growth niches in production and storage areas, susceptibility testing should be performed on biofilms produced at refrigeration temperatures. Moreover, the efficiency of the sanitizers used in food industries should be performed on mixed culture biofilms, since in field conditions these will predominate. The results presented here highlight the importance of the temperature used for biofilm formation, when susceptibility to disinfectants is being assessed, as biofilms produced at lower temperature were less susceptible to sanitizers. 相似文献
54.
Thermophiles as Potential Source of Novel Endotoxin Antagonists: the Full Structure and Bioactivity of theLipo‐oligosaccharide from Thermomonas hydrothermalis 下载免费PDF全文
Dr. Flaviana Di Lorenzo Dr. Ida Paciello Dr. Luigi Lembo Fazio Dr. Luciana Albuquerque Dr. Luisa Sturiale Prof. Milton S. da Costa Prof. Rosa Lanzetta Prof. Michelangelo Parrilli Prof. Domenico Garozzo Prof. Maria Lina Bernardini Dott. Alba Silipo Prof. Antonio Molinaro 《Chembiochem : a European journal of chemical biology》2014,15(14):2146-2155
Thermomonas hydrothermalis is a Gram‐negative thermophilic bacterium that is able to live at 50 °C. This ability is attributed to chemical modifications, involving those to bacterial cell‐wall components, such as proteins and (glyco)lipids. As the main component of the outer membrane of Gram‐negative bacteria, lipopolysaccharides (LPSs) are exposed to the environment, thus they can undergo structural chemical changes to allow thermophilic bacteria to live at their optimal growth temperature. Furthermore, as one of the major target of the eukaryotic innate immune system, LPS elicits host immune response in a structure‐dependent mode; thus the uncommon chemical features of thermophilic bacterial LPSs might exert a different biological action on the innate immune system—an antagonistic effect, as shown in studies of LPS structure–activity relationship in the ongoing research into antagonist LPS candidates. Here, we report the complete structural and biological activity analysis of the lipo‐oligosaccharide isolated from Thermomonas hydrothermalis, achieved by a multidisciplinary approach (chemical analysis, NMR, MALDI MS and cellular immunology). We demonstrate a tricky and interesting structure combined with a very interesting effect on human innate immunity. 相似文献
55.
Lydia Saidi Dr. Djenisa H. A. Rocha Dr. Oualid Talhi Dr. Yamina Bentarzi Prof. Dr. Bellara Nedjar-Kolli Dr. Khaldoun Bachari Dr. Filipe A. Almeida Paz Dr. Luisa A. Helguero Prof. Dr. Artur M. S. Silva 《ChemMedChem》2019,14(10):1041-1048
Breast and prostate cancers are frequently treated with chemotherapy. Several novel chemicals are being reported for this purpose, particularly synthetic and natural benzophenones. This work reports the synthesis of substituted 2-hydroxybenzophenones through 1,4-conjugate addition/intramolecular cycloaddition/dehydration of nitromethane on key intermediate chromones. Structures were extensively studied by means of 2D NMR spectroscopy and single-crystal XRD. Their cytotoxicity was evaluated in vitro in two breast cancer cell lines (MDA-MB-231 and T47-D) and one prostate cancer cell line (PC3). The most potent compound exhibited good cytotoxic effects against the three cancer cell lines (IC50 values ranging from 12.09 to 26.49 μm ) and induced cell-cycle retardation only on prostate cancer cells, which suggested that it might exert cell-type-specific effects. 相似文献
56.
Novel Tacrine‐Grafted Ugi Adducts as Multipotent Anti‐Alzheimer Drugs: A Synthetic Renewal in Tacrine–Ferulic Acid Hybrids 下载免费PDF全文
Mohamed Benchekroun Dr. Manuela Bartolini Dr. Javier Egea Dr. Alejandro Romero Dr. Elena Soriano Dr. Marc Pudlo Vincent Luzet Prof. Vincenza Andrisano Dr. María‐Luisa Jimeno Dr. Manuela G. López Sarah Wehle Prof. Tijani Gharbi Prof. Bernard Refouvelet Lucía de Andrés Clara Herrera‐Arozamena Prof. Barbara Monti Prof. Maria Laura Bolognesi Prof. María Isabel Rodríguez‐Franco Prof. Dr. Michael Decker Prof. José Marco‐Contelles Dr. Lhassane Ismaili 《ChemMedChem》2015,10(3):523-539
Herein we describe the design, multicomponent synthesis, and biological, molecular modeling and ADMET studies, as well as in vitro PAMPA‐blood–brain barrier (BBB) analysis of new tacrine–ferulic acid hybrids (TFAHs). We identified (E)‐3‐(hydroxy‐3‐methoxyphenyl)‐N‐{8[(7‐methoxy‐1,2,3,4‐tetrahydroacridin‐9‐yl)amino]octyl}‐N‐[2‐(naphthalen‐2‐ylamino)2‐oxoethyl]acrylamide (TFAH 10 n ) as a particularly interesting multipotent compound that shows moderate and completely selective inhibition of human butyrylcholinesterase (IC50=68.2 nM ), strong antioxidant activity (4.29 equiv trolox in an oxygen radical absorbance capacity (ORAC) assay), and good β‐amyloid (Aβ) anti‐aggregation properties (65.6 % at 1:1 ratio); moreover, it is able to permeate central nervous system (CNS) tissues, as determined by PAMPA‐BBB assay. Notably, even when tested at very high concentrations, TFAH 10 n easily surpasses the other TFAHs in hepatotoxicity profiling (59.4 % cell viability at 1000 μM ), affording good neuroprotection against toxic insults such as Aβ1–40, Aβ1–42, H2O2, and oligomycin A/rotenone on SH‐SY5Y cells, at 1 μM . The results reported herein support the development of new multipotent TFAH derivatives as potential drugs for the treatment of Alzheimer′s disease. 相似文献
57.
Targeting Serotonin 2A and Adrenergic α1 Receptors for Ocular Antihypertensive Agents: Discovery of 3,4‐Dihydropyrazino[1,2‐b]indazol‐1(2H)‐one Derivatives 下载免费PDF全文
Dr. Guido Furlotti Dr. Maria Alessandra Alisi Dr. Nicola Cazzolla Dr. Francesca Ceccacci Dr. Beatrice Garrone Dr. Tecla Gasperi Dr. Angela La Bella Prof. Dr. Francesca Leonelli Prof. Dr. Maria Antonietta Loreto Dr. Gabriele Magarò Giorgina Mangano Prof. Dr. Rinaldo Marini Bettolo Dr. Emanuela Masini Dr. Martina Miceli Dr. Luisa Maria Migneco Dr. Marco Vitiello 《ChemMedChem》2018,13(15):1597-1607
Glaucoma affects millions of people worldwide and causes optic nerve damage and blindness. The elevation of the intraocular pressure (IOP) is the main risk factor associated with this pathology, and decreasing IOP is the key therapeutic target of current pharmacological treatments. As potential ocular hypotensive agents, we studied compounds that act on two receptors (serotonin 2A and adrenergic α1) linked to the regulation of aqueous humour dynamics. Herein we describe the design, synthesis, and pharmacological profiling of a series of novel bicyclic and tricyclic N2‐alkyl‐indazole‐amide derivatives. This study identified a 3,4‐dihydropyrazino[1,2‐b]indazol‐1(2H)‐one derivative with potent serotonin 2A receptor antagonism, >100‐fold selectivity over other serotonin subtype receptors, and high affinity for the α1 receptor. Moreover, upon local administration, this compound showed superior ocular hypotensive action in vivo relative to the clinically used reference compound timolol. 相似文献
58.
Infinite dilution activity and diffusion coefficients of several solvents in polystyrene have been measured by inverse gas chromatographic on a capillary column for temperatures between 110 and 170°C. Chromatographic data have been treated according to Khan's model, evaluating the contribution to the peak broadening due to radial and axial molecular diffusion in the mobile phase, radial diffusion in the stationary phase, and interfacial mass transfer resistance. Four capillary columns have been prepared with coating thickness ranging from 0.5 to 3.3 microns in order to determine the minimum thickness necessary to obtain reliable measurements of the diffusion coefficient of the solvent in the polymer in every possible experimental condition. Our experimental data are in considerable agreement with the data already available in the literature, obtained by static and chromatographic methods. © 1994 John Wiley & Sons, Inc. 相似文献
59.
Flora A. Vega Emma F. Covelo Beatriz Cerqueira María Luisa Andrade 《Journal of hazardous materials》2009,170(2-3):1056-1063
The impact of waste disposal on marsh soils was assessed in topsoil samples collected at eight randomly selected points in the salt marsh in Ramallosa (Pontevedra, Spain) at 4-month intervals for 2 years. Polluted soil samples were characterized in physico-chemical terms and their heavy metal contents determined by comparison with control, unpolluted samples. The results revealed a marked effect of waste discharges on the soils in the area, which have low contents in heavy metals under normal environmental conditions. In fact, the studied soils were found to contain substantial amounts of total and DTPA-extractable Cd, Cu, Pb and Zn. Based on the relationship of the redox potential with the DTPA-extractable Cd, Cu, Pb, and Zn contents of the soils, strongly reductive conditions raised the total contents in these elements by effect of their remaining in the soils as precipitated sulphides. Such contents, however, decreased as oxidative conditions gradually prevailed. The contents in DTPA-extractable metals increased with increasing Eh through the release of the metals in ionic form to the soil solution under oxidative conditions. The contents in heavy metals concentrating in the polluted soils were several times higher than those in the control soils (viz. 2 vs. 6 for Cd, 4 vs. 6 for Cu, 4 vs. 20 for Pb, and 2 vs. 15 for Zn, all in mg kg−1). This can be expected to influence the amounts of available heavy metals present in the soils, and hence the environmental quality of the area, in the near future. Based on its geoaccumulation index (Class ≥3 for Cd and Cu, and 1–4 for Pb and Zn), the Ramallosa marsh is highly polluted with Cd and moderately to highly polluted with Cu, Pb and Zn. The enrichment factors obtained confirm that the salt marsh is highly polluted (especially with Cd) as the primary result of anthropic activity. 相似文献
60.
Sartori Luisa; Becchio Cristina; Bulgheroni Maria; Castiello Umberto 《Canadian Metallurgical Quarterly》2009,35(5):1490
Four experiments investigated the influence of a sudden social request on the kinematics of a preplanned action. In Experiment 1, participants were requested to grasp an object and then locate it within a container (unperturbed trials). On 20% of trials, a human agent seated nearby the participant unexpectedly stretched out her arm and unfolded her hand as if to ask for the object (perturbed trials). In the remaining 3 experiments, similar procedures were adopted except that (a) the human was replaced by a robotic agent, (b) the gesture performed by the human agent did not imply a social request, and (c) the gaze of the human agent was not available. Only when the perturbation was characterized by a social request involving a human agent were there kinematic changes to the action directed toward the target. Conversely, no effects on kinematics were evident when the perturbation was caused by the robotic agent or by a human agent performing a nonsocial gesture. These findings are discussed in the light of current theories proposed to explain the effects of social context on the control of action. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献