全文获取类型
收费全文 | 2112篇 |
免费 | 115篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 41篇 |
综合类 | 12篇 |
化学工业 | 528篇 |
金属工艺 | 67篇 |
机械仪表 | 92篇 |
建筑科学 | 55篇 |
矿业工程 | 5篇 |
能源动力 | 169篇 |
轻工业 | 178篇 |
水利工程 | 37篇 |
石油天然气 | 23篇 |
无线电 | 173篇 |
一般工业技术 | 411篇 |
冶金工业 | 112篇 |
原子能技术 | 26篇 |
自动化技术 | 320篇 |
出版年
2024年 | 9篇 |
2023年 | 40篇 |
2022年 | 68篇 |
2021年 | 148篇 |
2020年 | 104篇 |
2019年 | 138篇 |
2018年 | 152篇 |
2017年 | 146篇 |
2016年 | 129篇 |
2015年 | 99篇 |
2014年 | 101篇 |
2013年 | 205篇 |
2012年 | 143篇 |
2011年 | 162篇 |
2010年 | 94篇 |
2009年 | 76篇 |
2008年 | 73篇 |
2007年 | 56篇 |
2006年 | 34篇 |
2005年 | 23篇 |
2004年 | 19篇 |
2003年 | 8篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 27篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有2249条查询结果,搜索用时 26 毫秒
81.
Merzouk SA Saker M Reguig KB Soulimane N Merzouk H Guermouche B Berrouiguet AY Hichami A Narce M Khan NA 《Lipids》2008,43(6):485-497
In this work, we assessed the in-vitro effects of eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) (final concentration, 15 microM) on T cell blastogenesis, interleukin-2 and -4 (IL-2, IL-4) secretion, fatty acid composition and intracellular oxidative status in type I diabetic patients with or without complications. Con A stimulated lymphocyte proliferation, glucose uptake, intracellular reduced glutathione levels and catalase activity were lower in diabetics as compared to controls, regardless to the presence of complications. EPA and DHA diminished T-lymphocyte proliferation and IL-2 production but enhanced IL-4 secretion in both diabetic and control groups. No changes in the levels of reduced glutathione and in the activities of catalase and SOD were observed in control T cells cultured in the presence of EPA and DHA. However, in diabetic patients, addition of n-3 PUFA to culture induced an increase in T cell levels of reduced glutathione and hydroperoxide, and in activities of catalase and SOD. Low levels of arachidonic acid (C20:4n-6) were found in plasma membrane phospholipids of lymphocytes from diabetic patients compared to controls. Incubation of lymphocytes with EPA and DHA was associated with an incorporation of these fatty acids in membrane phospholipids. In conclusion, the beneficial effects of n-3 PUFA on T cell functions in type I diabetes could be attributed to their suppressive action and modulation of cytokine secretion, and to the improvement of intracellular oxidative status. 相似文献
82.
Structural, rheological, and mechanical properties of ternary blends of a liquid crystalline copolyester (LCP) composed of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, poly(ehtylene naphthalate)(PEN), and poly(ethylene terephtalate) (PET) were investigated using capillary rheometry, tensile testing, scanning electron microscopy, and X-ray diffraction. Viscosity-shear rate behavior of the ternary blends is very similar to that of pure polymers and their binary blends. The activation energy of flows of the ternary blends was smaller than those of PEN and PET. Tensile modulus and strength of extruded strands of the blends increased with increasing LCP content. The extruded strands of the blends consist of a crystalline and oriented LCP phase and an amorphous and unoriented PEN/PET blended phase. Tensile mechanical properties and structures of the ternary blends were discussed. 相似文献
83.
Railway Engineering Science - Congestion pricing is seen as an effective policy to address traffic congestion. In such policies where money, people and authorities are involved, the success... 相似文献
84.
Majid Moghadam Valiollah Mirkhani Shahram Tangestaninejad Iraj Mohammadpoor-Baltork Maedeh Moshref Javadi 《Inorganic chemistry communications》2010,13(2):244-249
The hybrid complex consist of molybdenylacetylacetonate complex covalently linked to a lacunary Keggin-type polyoxometalate, K8[SiW11O39] (POM), was synthesized and characterized by elemental analysis, SEM, XRD, diffuse reflectance UV–Vis and FT-IR spectroscopic methods. The hybrid complex, [MoO2(acac)–POM] (1), was used for alkene epoxidation with tert-BuOOH in 1,2-dichloroethane as solvent. The complex (1) can catalyze epoxidation of various olefins including non-activated terminal olefins. The effect of reaction parameters such as oxidant, solvent, and temperature on the epoxidation of cyclooctene was also investigated. This heterogeneous catalyst was reused several times in the oxidation of cyclooctene. 相似文献
85.
Attempts have been made to use different amount of ground tire rubber (GTR) powder as a partial substitute for natural rubber (NR) in thermoplastic elastomer based on linear low‐density polyethylene (LLDPE, 60 wt%) and NR (40wt%). Maleic anhydride (MA) and dicumyl peroxide (DCP) were used, during melt mixing of the compound, to modify GTR and vulcanize the rubber phases of the blends. Morphology of the blends was studied by scanning electron microscopy and rheological behavior investigated through rheomechanical spectroscopy. Mechanical properties of the blends were also measured, and the effect of GTR concentration on properties was evaluated. Obtained results showed that modification of GTR with MA and using DCP in the blends containing GTR improves the bonding between GTR and matrix. This leads to a distinctive rheological behavior and enhances tensile strength and elongation at break compared to its corresponding simple blend. It can be said that using of MA and DCP during melt mixing of thermoplastic elastomers based on LLDPE/NR containing GTR, concludes to a better dispersion of GTR and formation of morphology similar to that of a dynamic vulcanized thermoplastic elastomer, which improves interfacial bonding between phases and causes a dramatically increase in mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
86.
Roozbeh Javad Kalbasi Majid Kolahdoozan Keinaz ShahabianFarzad Zamani 《Catalysis communications》2010,11(14):1109-1115
This work is concerned about the preparation and characterization of MnO4− supported poly (4-methyl vinylpyridinium)/SBA-15 which was effectively employed as a heterogeneous oxidant for oxidation of aromatic alcohols. P4MVPMnO4/SBA-15 exhibited excellent activity and selectivity under mild and solvent-less conditions. 相似文献
87.
Solubility analysis of clozapine and lamotrigine in supercritical carbon dioxide using static system
The experimental techniques used to obtain the solubilities of clozapine and lamotrigine in supercritical carbon dioxide include a simple static technique. The solubility measurements were performed at temperatures between 318 and 348 K and pressures between 121.6 and 354.0 bar. These chemicals have solubilities with values ranging from 3.6 × 10−6 to 4.2 × 10−5 (clozapine) and 1 × 10−6 to 6 × 10−5 (lamotrigine) mole fraction. The solubility data were correlated using four semi-empirical density-based models (Chrastil, Bartle, K-J and M-T models). Correlation of the results shows good self-consistency of the data obtained with the Bartle model for clozapine with an overall average absolute relative deviation (AARD%) of 11.21. The calculated results with each four models show satisfactory agreement with the experimental data for lamotrigine with an overall AARD% 11.72, 8.99, 2.75, 3.86 for Chrastil, K-J, Bartle, M-T models, respectively. Using the correlation results, the heat of drug-CO2 solvation and that of drug vaporization were approximated. 相似文献
88.
Majid Alizadeh Moghadam Reza Mohammadi Ehsan Sadeghi Mohammad Amin Mohammadifar Mohammad Nejatian Maryam Fallah Milad Rouhi 《应用聚合物科学杂志》2021,138(28):50672
The effects of gum tragacanth obtained from two species of Astragalus Gossypinus (GT-G) and A. Parrowianus (GT-P) at two levels of 10% and 30% combined with cellulose nanofibers (CNF; 5%) on the physico-mechanical and structural properties of polyvinyl alcohol (PVA) nanocomposite film were investigated in this study. The water solubility and water vapor permeability of the films decreased with increasing the content of both gums, especially in the film containing 30% GT-P. The highest values of the tensile strength (39.3 MPa) and elongation at break (445%) belonged to the treatment containing 10% GT-P (90/10P/0). The FTIR and DSC analyses confirmed good interactions between GT and PVA in the 90/10P/0 treatment. SEM images indicated the dense structure of this film as the optimum treatment. Although the presence of CNF in the films containing GT-G improved some properties, especially the Young modulus, it impaired all the functional properties of nanocomposite GT-P film. 相似文献
89.
M. Aamir I. Bibi S. Ata K. Jilani F. Majid S. Kamal N. Alwadai M.A.S. Raza M. Bashir S. Iqbal M. Aadil M. Iqbal 《Ceramics International》2021,47(12):16696-16707
In the present investigation, La1-xCoxCr1-yFeyO3 (x,y = 0.0, 0.12, 0.36, 0.60) perovskite was fabricated via a facile micro-emulsion route. The synthesized perovskites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques to examine the effect of Co and Fe ions on the physico-chemical properties. The ferroelectric, dielectric, and magnetic properties of La1-xCoxCr1-yFeyO3 were changed significantly as a function of dopants contents (Co and Fe ions). Outcomes revealed that the dielectric, ferroelectric and magnetic properties of LaCrO3 perovskite can be tuned significantly via Co and Fe doping and La0.40Co0.60Cr0.40Fe0.60O3 have potential for photocatalytic dye removal under (visible) light expoure. The photocatalytic activity (PCA) of the pristine LaCrO3 and La0.40Co0.60Cr0.40Fe0.60O3 photocatalyst was evaluated under (visible) light irradiation for crystal violet (CV) dye. Experimental results revealed that La0.40Co0.60Cr0.40Fe0.60O3 photocatalyst degrdae almost 77.21% CV dye with the rate constant value of 0.01475 min?1. In the presence of isopropyl alcohol (IPA) scavenger, the PCA of the La0.40Co0.60Cr0.40Fe0.60O3 photocatalyst and rate constant value of the photocatalytic reaction decreased to 32.5% and 0.00491 min?1, suggesting the superoxide as main active specie. Results revealed that Co and Fe doping doped material is efficient for photocatalytic presentations under solar light expoure. 相似文献
90.
Muhammad Khurram Tufail Niaz Ahmad Le Yang Lei Zhou Muhammad Adnan Naseer Renjie Chen Wen Yang 《中国化学工程学报》2021,39(11):16-36
The development of an inorganic electrochemical stable solid-state electrolyte is essentially responsible for future state-of-the-art all-solid-state lithium batteries (ASSLBs). Because of their advantages in safety, working temperature, high energy density, and packaging, ASSLBs can develop an ideal energy storage system for modern electric vehicles (EVs). A solid electrolyte (SE) model must have an economical synthesis approach, exhibit electrochemical and chemical stability, high ionic conductivity, and low interfacial resistance. Owing to its highest conductivity of 17 mS·cm-1, and deformability, the sulfide-based Li7P3S11 solid electrolyte is a promising contender for the high-performance bulk type of ASSLBs. Herein, we present a current glimpse of the progress of synthetic procedures, structural aspects, and ionic conductivity improvement strategies. Structural elucidation and mechanistic approaches have been extensively discussed by using various characterization techniques. The chemical stability of Li7P3S11 could be enhanced via oxide doping, and hard and soft acid/base (HSAB) concepts are also discussed. The issues to be undertaken for designing the ideal solid electrolytes, interfacial challenges, and high energy density have been discoursed. This review aims to provide a bird's eye view of the recent development of Li7P3S11-based solid-state electrolyte applications and explore the strategies for designing new solid electrolytes with a target-oriented approach to enhance the efficiency of high energy density all-solid-state lithium batteries. 相似文献