全文获取类型
收费全文 | 198篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
化学工业 | 41篇 |
金属工艺 | 5篇 |
机械仪表 | 4篇 |
建筑科学 | 5篇 |
能源动力 | 11篇 |
轻工业 | 21篇 |
水利工程 | 1篇 |
无线电 | 8篇 |
一般工业技术 | 53篇 |
冶金工业 | 29篇 |
原子能技术 | 4篇 |
自动化技术 | 34篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 4篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1968年 | 2篇 |
1962年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有216条查询结果,搜索用时 0 毫秒
81.
Corrosion of low-alloyed steels in liquid ammonia Corrosion behaviour and stress corrosion cracking of the base material, the welding and the heat affected zone in liquid ammonia at room temperature of the low-alloyed steels 13 Cr Mo 4 4 (W. Nr. 1.7335) and 15 Mo 3 (W. Nr. 1.5415), as well as the un-alloyed steel StE 460 (W. Nr. 1.8905) for comparison were investigated. According to polarization curves, the corrosion current density in the passive state usually was lower for the welding than for the base steel. In the active state the welding of the low-alloyed steel corroded faster than the weldings of the unalloyed steel. In the region between the welding and the heat affected zone of the base steel corrosion was nonuniform. CERT-experiments revealed susceptibility to stress corrosion cracking in the orders StE 460 < 15 Mo 3 < 13 Cr Mo 4 4, and base steel < welding < transition zone. The highest susceptibility was observed at electrode potentials in the middle of the passive region. Additions of water exceeding about 100 ppm favoured stress corrosion cracking. The susceptibility decreased again at concentrations ≥ 1000 ppm. Oxygen increased the susceptibility to stress corrosion cracking only at high concentrations not occurring in practice. The presently investigated low-alloyed steels are not superior to the unalloyed steel from the viewpoint of stress corrosion cracking. 相似文献
82.
Huerta RH Esparza-Romero J Urquidez R Pacheco BI Valencia ME Alemán-Mateo H 《Archivos latinoamericanos de nutrición》2007,57(4):357-365
A prediction equation to estimate body fat mass from skinfold thickness for healthy elderly was developed using a four compartmental (4C) model as criterion method. This study included 202 subjects = 60 y old. The measurements of total body water, bone mineral content and body density were included in the 4C model equation. Total sample was randomly partitioned. Sub-sample one was used to design the equations, which were applied in sub-sample two. Its accuracy and precision was evaluated by lineal regression analysis and the bias by Bland and Altman analysis and simple lineal regression. The best model included body mass, sex and the calf and triceps skinfolds thicknesses, with an R2, standard error of the estimate and Cp of 0.85, 3.2 and 3.2, respectively. When the equation was applied in sub-sample two, it was accurate and precise, it showed no significant deviation from the line of identity (the intercept was no significantly different from zero, P>0.05), and slope was different from cero (or similar to 1) (P<0.05). Fat mass by the equation accounted for 86% of the variability of the mean fat mass estimated by the 4C model, having a low standard error of the estimate (3.2 kg) and low pure error (3.1 kg). The new equation was accurate and precise as well as free of significant bias in men and women together and for separately. This equation can be a good option to estimate fat mass in elderly men and women with similar physical characteristics to subjects of this study, and it can be used in clinical and epidemiological studies in this growing group. 相似文献
83.
Guadalupe Del C. Pizarro Oscar G. Marambio Manuel Jeria‐Orell Margarita R. Huerta Oscar O. Rodríguez Bernabé L. Rivas Kurt E. Geckeler 《应用聚合物科学杂志》2007,105(5):2893-2902
This article reports the synthesis of poly(N‐maleoylglycine‐co‐itaconic acid) by radical copolymerization under different feed mole ratios and its properties to remove various metal ions, such as Cu(II), Cr(III), Co(II), Zn(II), Ni(II), Pb(II), Cd(II), and Fe(III), in aqueous phase with the liquid‐phase polymer‐based retention(LPR) technique. The interactions of inorganic ions with the hydrophilic water‐soluble polymer were determined as a function of pH and filtration factor. Metal ion retention was found to strongly depend on the pH. Metal ion retention increased as pH and MG content units in the macromolecular backbone increased. The copolymers were characterized by elemental analysis, FTIR, 1H‐NMR, and 13C‐NMR spectroscopy. Additionally, intrinsic viscosity, molecular weight, and polydispersity have been determined for the copolymers. Copolymer and polymer–metal complex thermal behavior was studied using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques under nitrogen atmosphere. The thermal decomposition temperatures (TDT) were influenced by the copolymer composition. The copolymers present lower TDT than the polymer–metal complex with the same copolymer composition. All copolymers present a single Tg, indicating the formation of random copolymers. A slight deviation of the Tg for the copolymers and its complexes can be observed. The copolymer Tg is higher than the Tg value for the polymer–metal complexes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
84.
Ernesto Rivera María del Pilar Carreón-Castro Gloria Huerta Leticia Rivera 《Polymer》2007,48(12):3420-3428
Novel grafted azo-polymers were prepared from commercial low density polyethylene plates (PE). First, precursor polymers were synthesized by reacting PE in the presence of acryloyl chloride using gamma radiation. Further esterification of the resulting grafted polymers with four new amino-nitro substituted azobenzene derivatives bearing oligo(ethylene glycol) segments: N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(5-hydroxy-3-oxapentas-1-yl)amine (RED-PEG-2), N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(8-hydroxy-3,6-dioxaoctas-1-yl)amine (RED-PEG-3), N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(11-hydroxy-3,6,9-trioxaundecas-1-yl)amine (RED-PEG-4) and N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(17-hydroxy-3,6,9,12,15-pentaoxaheptadecas-1-yl)amine (RED-PEG-6) led to the formation of branched azo-polymers. These polymers were characterized and their thermal and optical properties were studied. Besides, the influence of the irradiation dose, irradiation time and the structure of the dyes on the properties of the obtained polymers are discussed. 相似文献
85.
Summary New polymers containing pyrrole units in the main chain were obtained by chemical modification of diacetylene-containing polymers,
which were prepared by oxidative coupling of terminal diacetylenes or superelectrophilic polycondensation of diphenoxydiacetylene
with isatin. Diacetylenic fragments in the polymers thus obtained reacted with aromatic amines in the presence of copper chloride
to yield the corresponding pyrroles. The reaction between diacetylenic compounds and amines was studied to determine the proper
reaction conditions for introduction of pyrrole groups into the polymer backbone. The new polymers and their model compounds
were fully characterized by NMR, IR and thermal analysis. 相似文献
86.
E. Ramírez‐Vargas D. Navarro‐Rodríguez B. M. Huerta‐Martínez F. J. Medellín‐rodríguez J. S. Lin 《Polymer Engineering and Science》2000,40(10):2241-2250
Morphological and mechanical properties of polypropylene [PP]/poly(ethylene vinyl acetate) [EVA] blends have been studied. Infrared results using thin films first indicated a transition toward compatibility between both components at concentrations above 40% EVA. The transition was verified with different experimental techniques and it was associated to morphological changes and mechanical properties. The PP/EVA blends were mechanically evaluated in terms of impact and tensile strength to determine the influence of blending on the performance properties of these materials. Agreement was found between the transition and the enhancement of both elongation at break and impact strength. 相似文献
87.
Concepcion Santacruz Marisela Linares Yonathan Garfias Luisa M. Loustaunau Lenin Pavon Sonia Mayra Perez-Tapia Maria C. Jimenez-Martinez 《International journal of molecular sciences》2015,16(3):4850-4864
Corneal infections are frequent and potentially vision-threatening diseases, and despite the significance of the immunological response in animal models of microbial keratitis (MK), it remains unclear in humans. The aim of this study was to describe the cytokine profile of tears in patients with MK. Characteristics of ocular lesions such as size of the epithelial defect, stromal infiltration, and hypopyon were analyzed. Immunological evaluation included determination of interleukine (IL)-1β, IL-6, IL-8, IL-10, IL-12 and tumor necrosis factor (TNF)-α in tear samples obtained from infected eyes of 28 patients with MK and compared with their contralateral non-infected eyes. Additionally, frequency of CD4+, CD8+, CD19+ and CD3−CD56+ cells was also determined in peripheral blood mononuclear cells in patients with MK, and compared with 48 healthy controls. Non-significant differences were observed in the size of the epithelial defect, stromal infiltration, and hypopyon. Nevertheless, we found an immunological profile apparently related to MK etiology. IL-8 > IL-6 in patients with bacterial keratitis; IL-8 > IL-6 > IL-1β and increased frequency of circulating CD3−CD56+ NK cells in patients with gram-negative keratitis; and IL-8 = IL-6 > IL-1β in patients with fungal keratitis. Characterization of tear cytokines from patients with MK could aid our understanding of the immune pathophysiological mechanisms underlying corneal damage in humans. 相似文献
88.
Silvia T. Huerta Marcial Gabriel Landázuri Emma R. Macías-Balleza Luis C. Rosales-Rivera Juan M. Ruso Jorge E. Puig J. F. Armando Soltero 《Journal of surfactants and detergents》2017,20(3):659-671
The aim of this work was to determine the detailed phase behavior of the sodium dodecyl sulfate/aniline hydrochloride/water system as a function of concentration of sodium dodecyl sulfate (SDS), aniline hydrochloride (AHC) to sodium dodecyl sulfate molar ratio (R = [AHC]/[SDS]) and temperature. Phase behavior information was obtained via polarizing microscopy, differential scanning calorimetry (DSC), cryo-scanning electron microscopy (Cryo-SEM) and oscillatory linear rheological measurements with good agreement among these techniques. It is well known that SDS in water forms spherical micelles at concentrations lower than 40 wt% and temperatures above its Krafft temperature (T k = 16–21 °C). In this region, the SDS/water system exhibits Newtonian rheological behavior, which is characteristic of spherical micellar solutions. The addition of the hydrotrope, aniline hydrochloride, to SDS aqueous solutions produces a viscosity increase in this system as R augments, and a maximum of about five orders of magnitude was found at R = 0.47 for 5 wt% SDS at 20 °C. Moreover, the system shows a transition from viscous to strong viscoelastic behavior. These changes in the rheological behavior are produced by the transitions from sphere to rodlike micelles, which are induced by the hydrophobicity of AHC causing it to be absorbed into the core and the hydrophilic interface of the micelles, which screens the repulsions between the charged head groups. 相似文献
89.
M.D. Starostenkov E. V.Kozlov O. V. Andruhova N. V. Lomskikh N.M. Gurova A. V. Borissov ) General Physics Department ASTU Lenin St. Barnaul Russia ) Physics Department TSABU Solyanaya Sq. Tomsk Russia 《金属学报(英文版)》2000,13(2):551-556
1.IntroductionTheinvestigationofinternalboundaries(antiphaseandinterphaseboundaries,grainboundariesandothers)inhomophaseandheterophasematerialsistheactualproblemofphaseorder--disordertransitionkinetics.TherearesomeexpermentaldatashowingtheirimportantroleinprocessesofmaterialstructuretransformationundervariousexternalfaCtorsll--4](temperature,pressure,stressandothers).Forexample,differentstructuralfeaturesarelocalizedonantiphasedomainboundarieswithtemperaturegrowth[2,3].Antiphaseboundariesbeha… 相似文献
90.
AbstractObjectives: The aim of the study was to deliver effective doses of quercetin (Que) to the lower region of hair follicles (HFs) using the transfollicular route through dipalmotylphosphatidylcholine (DPPC)-reinforced poly lactide-co- glycolide nanoparticles (DPPC-PLGA hybrid NPs) for the treatment of alopecia.Method: PLGA and DPPC-PLGA hybrid NPs were prepared by double-emulsification solvent evaporation method. NPs were characterized for size, shape, zeta potential entrapment and drug release. Drug-polymer interactions were determined by infrared spectroscopy (Fourier transform infrared spectroscopy, FTIR) and differential scanning calorimetry (DSC). Follicular uptake of fluorescent marker tagged NPs was assessed on isolated rat skin by fluorescent microscopy. Potential of hybrid NPs to induce hair regrowth was tested on testosterone-induced alopecia in rat models by visual inspection, hair follicular density measurement (no./mm), and histological skin tissue section studies.Key findings: Hybrid NPs had mean vesicles size 339?±?1.6, zeta potential –32.6?±?0.51, and entrapment efficiency 78?±?5.5. Cumulative drug release after 12?h was found to be 47.27?±?0.79%. FTIR and DSC confirmed that drug was independently dispersed in the amorphous form in the polymer. Data from fluorescence microscopy suggested that NPs were actively taken up by HFs. In-vivo studies on alopecia-induced rat models showed that hybrid NPs improved hair regrowth potential of Que and accumulation of NPs at HFs end region inhibit HFs cells apoptosis.Conclusion: This study concludes that phospholipid–polymer hybrid NPs could be the promising transfollicular delivery system for Que in the treatment of androgenic alopecia management. 相似文献