全文获取类型
收费全文 | 386篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 162篇 |
金属工艺 | 5篇 |
机械仪表 | 12篇 |
建筑科学 | 9篇 |
矿业工程 | 1篇 |
能源动力 | 9篇 |
轻工业 | 83篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 13篇 |
一般工业技术 | 45篇 |
冶金工业 | 39篇 |
自动化技术 | 25篇 |
出版年
2023年 | 6篇 |
2022年 | 23篇 |
2021年 | 23篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 20篇 |
2013年 | 28篇 |
2012年 | 27篇 |
2011年 | 32篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 4篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1960年 | 2篇 |
排序方式: 共有409条查询结果,搜索用时 11 毫秒
21.
Tara B. Richardson Mirna A. Mosiewicki Cihan Uzunpinar Norma E. Marcovich Mirta I. Aranguren Fatma Kilinc‐Balci Roy M. Broughton Maria L. Auad 《Polymer Composites》2011,32(3):455-463
Multi‐walled carbon nanotubes (CNTs) and cellulose nanofibers (CNFs) reinforced shape memory polyurethane (PU) composite fibers and films have been fabricated via extrusion and casting methods. Cellulose nanofibers were obtained through acid hydrolysis of microcrystalline cellulose. This treatment aided in achieving stable suspensions of cellulose crystals in dimethylformamide (DMF), for subsequent incorporation into the shape memory matrix. CNTs were covalent functionalized with carboxyl groups (CNT‐COOH) and 4,4′‐methylenebis (phenylisocyanate) (MDI) (CNT‐MDI) to improve the dispersion efficiency between the CNT and the polyurethane. Significant improvement in tensile modulus and strength were achieved by incorporating both fillers up to 1 wt% without sacrificing the elongation at break. Electron microscopy was used to investigate the degree of dispersion and fracture surfaces of the composite fibers and films. The effects of the filler (type and concentration) on the degree of crystallinity and thermal properties of the hard and soft segments that form the PU sample were studied by calorimetry. Overall, results indicated that the homogeneous dispersion of nanotubes and cellulose throughout the PU matrix and the strong interfacial adhesion between nanotubes and/or cellulose and the matrix are responsible for the enhancement of mechanical and shape memory properties of the composites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers 相似文献
22.
María L Auad Tara Richardson William J Orts Eliton S Medeiros Luiz HC Mattoso Mirna A Mosiewicki Norma E Marcovich Mirta I Aranguren 《Polymer International》2011,60(5):743-750
Segmented polyurethanes exhibiting shape memory properties were modified by the addition of polyaniline (PANI)‐coated cellulose nanofibrils (CNFs). The two‐phase structure of the polymer is responsible for the material's ability to ‘remember’ and autonomously recover its original shape after being deformed in response to an external thermal stimulus. PANI was grown on the surface of the CNFs via in situ polymerization. Modified nanocrystals were added to the segmented polyurethane in concentrations ranging from 0 to 15 wt%. The changes in the material properties associated with the percolation of the coated fibrils appear at higher concentrations than previously observed for non‐modified CNFs, which suggests that fibril agglomeration is occurring due to the PANI coating. The shape memory behavior of the composites is maintained at about the same level as that of the unfilled polyurethane only up to 4 wt% of fibrils. At higher concentrations, the rigidity of the nanofibrils as well as their interaction with the hard‐segment phase and the increasing difficulty of dispersing them in the polymer collaborate to produce early breakage of the specimens when stretched at temperatures above the melting point of the soft segments. Copyright © 2010 Society of Chemical Industry 相似文献
23.
24.
Rogério A. Saraiva Edinardo F. F. Matias Henrique D. M. Coutinho José G. M. Costa Heloísa Helena F. Souza Cícera Norma Fernandes João B. T. Rocha Irwin R. A. Menezes 《European Journal of Lipid Science and Technology》2011,113(8):967-972
The oil obtained from the Caryocar coriaceum Wittm. (pequi) fruit pulp (C. coriaceum fixed oil – CCFO), rich in fatty acids, has been secularly employed by traditional medicine in the treatment of respiratory affections, skin inflammation, and wounds. These observations encouraged us to investigate the antimicrobial activity of CCFO and to investigate its effect in combination with aminoglycosides. The minimum inhibitory concentration (MIC) of CCFO alone and associated with aminoglycosides against Escherichia coli and Staphylococcus aureus strains were determined using microdilution assay. CCFO alone had a MIC of 512 µg/mL against E. coli and S. aureus resistant strains. Combining the CCFO with aminoglycosides reduced the MIC of aminoglycosides against the resistant strains of E. coli and S. aureus. The results obtained indicate that CCFO displays a significant synergistic antibiotic effect when combined with aminoglycosides, demonstrating that the oil constituents (fatty acids) may act as potentiators of the antibiotic activity of aminoglycosides. These properties make CCFO oil an interesting alternative as a remedy or nutraceutical against multiresistant bacteria, preventing the development of resistance by these microorganisms. Practical applications: This article demonstrates the capacity of the C. coriaceum oil to enhance the antibiotic activity of aminoglycosides. This activity could represent a new way to combat the growing bacterial resistance to antibiotics, an important problem of public health. 相似文献
25.
Dense semicrystalline membranes of polyhydroxyalkanoates with medium change length (PHASCL), polyhydroxybutyrate (PHB) and poly β (hydroxybutyrate-co-hydroxyvalerate) [P(βHB-co-XβHV)] were characterized using wide-angle X-ray (WAXS) and scanning electron microscopy. PHB membranes showed a more rugged surface than those of copolymers (0-22%HV). Properties such as swelling capacity, vapor permeability and selectivity were investigated. Swelling percentage in water-ethanol mixtures was 34% for PHB as compared to 14% for copolymers membranes. The ethanol/water selectivity (αs) of PHB was 5.8 which shows that it is more selective than copolymers.The water vapor and ethanol vapor permeability were determined by a gravimetric technique at different temperatures by static and dynamic methods. PHB permeability was 69.5 Barrer at 30 °C and a discreet increment was observed at temperatures (30-50 °C). The difference in permeability between PHB and [P(βHB-co-X%βHV)] could be interpreted in terms of the crystallization rate, crystallite size and distribution which impact to transport properties of amorphous phase. 相似文献
26.
We show herein that the photoelectrochemical behavior of a given semiconductor nanodot (p-CuSCN or n-TiO2) in an alumina template matrix, is remarkably different than that of its macro-sized counterpart. Three separate examples of this distinct difference in behavior are presented. It is shown how the photoresponse (e.g. photocurrent) may be amplified (from a low level typical of the signal emanating from a ∼10−11 cm2 region corresponding to a semiconductor nanodot) by using a large number of electrically inter-connected Au nanowires to support the overlying semiconductor nanodots. The anomalous photoresponse of p-CuSCN nanodots in the template matrix was also numerically simulated by a simple parallel equivalent circuit consisting of a semiconductor and a photocapacitor. Possible practical application scenarios are finally presented for these nanostructures. 相似文献
27.
A series of composites based on polydimethylsiloxane‐α,ω‐diol (PDMS) as polymeric matrix, silica aerogel as reinforcing filler, and the lignin powder—a biomass derivative, as bulking filler, have been prepared. Different weight ratios between components were used. The composites were investigated by scanning electron microscopy, dynamic mechanical analysis, tensile strength tests, X‐ray diffraction analysis, thermogravimetric analysis, and differential scanning calorimetry. The results were compared with those obtained on a reference sample prepared by using a classical material—diatomite and a pure crosslinked PDMS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
28.
Norma Sterin-Speziale Verónica L. Kahane Clara P. Setton Emir H. Speziale 《Lipids》1989,24(2):146-150
The effect of bradykinin on the mobilization of arachidonic acid was analyzed separately by acylation and degradation.
Acylating activity was determined by the incorporation of [14C]arachidonic acid into the phospholipids at different times. Different concentrations of bradykinin had no effect on the
phospholipid acylating activities.
The degradation of the phospholipids was performed on renal medullary slices prelabeled with [14C]arachidonic acid. Treatment with bradykinin produced an initial degradation of phosphatidylcholine, phosphatidylethanolamine
and phosphatidylinositol, with a concomitant increase in lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylinositol
within 5 min of incubation. Phosphatidylcholine-, phosphatidylethanolamine-and phosphatidylinositol-labeling increased thereafter
and reached the control values after 10 min of incubation.
After 30 min, incubation of prelabeled slices with bradykinin produced a significant concentration-dependent increase in the
phospholipid-labeling by reutilization of [14C]arachidonic acid.
The effect of bradykinin on the phospholipid-labeling was blocked by preincubation with increasing concentrations of dBc AMP.
Mepacrine also blocked the bradykinin stimulation in phosphatidylcholine and phosphatidylethanolamine, but had no effect on
bradykinin-induced changes in the phosphatidylinositol arachidonic acid moiety. 相似文献
29.
The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young’s modulus and thus a tool for Design Practice for repair applications. 相似文献
30.
Paolo Bergamo Giovanna Trinchese Chiara De Filippo Giorgio Gifuni Marcello Gaita Angelica Pignalosa Immacolata Donizzetti Rosalba Putti Rossella Di Palo Antonio Barletta Maria Pina Mollica 《Molecular nutrition & food research》2012,56(10):1596-1600
Dietary PUFA, mainly those of the n‐3 family, are known to play essential roles in the maintenance of energy balance and in the reduction of body fat deposition through the upregulation of mitochondrial uncoupling that is the main source of reactive oxygen species. We hypothesized that rat supplementation with raw donkey's milk (DM), characterized by low‐fat content and higher n3:n6 ratio, may affect energy balance, lipid metabolism, and prooxidant status as compared to animals treated with cow's milk. In the present study, the effects of drinking raw DM (for 4 weeks) on energy balance, lipid metabolism, antiinflammatory, and antioxidant/detoxifying defences was compared to that produced by rat intake of an iso‐energetic amount of raw cow's milk. The hypolipidemic effect produced by DM paralleled with the enhanced mitochondrial activity/proton leakage and with the increased activity or expression of mitochondrial markers namely, carnitine palmitoyl transferase and uncoupling protein 2. The association of decreased energy efficiency with reduced proinflammatory signs (TNF‐α and LPS levels) with the significant increase antioxidant (total thiols) and detoxifying enzyme activities (glutathione‐S‐transferase NADH quinone oxidoreductase) in DM‐treated animals, indicated that beneficial effects were attributable, at least in part, to the activation of nuclear factor 2 erythroid‐related factor 2 pathway. 相似文献