全文获取类型
收费全文 | 3994篇 |
免费 | 427篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 60篇 |
化学工业 | 1148篇 |
金属工艺 | 149篇 |
机械仪表 | 228篇 |
建筑科学 | 73篇 |
能源动力 | 241篇 |
轻工业 | 343篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 747篇 |
一般工业技术 | 936篇 |
冶金工业 | 119篇 |
原子能技术 | 75篇 |
自动化技术 | 298篇 |
出版年
2024年 | 4篇 |
2023年 | 48篇 |
2022年 | 74篇 |
2021年 | 126篇 |
2020年 | 106篇 |
2019年 | 119篇 |
2018年 | 145篇 |
2017年 | 181篇 |
2016年 | 169篇 |
2015年 | 161篇 |
2014年 | 210篇 |
2013年 | 293篇 |
2012年 | 318篇 |
2011年 | 411篇 |
2010年 | 240篇 |
2009年 | 264篇 |
2008年 | 188篇 |
2007年 | 156篇 |
2006年 | 138篇 |
2005年 | 130篇 |
2004年 | 105篇 |
2003年 | 126篇 |
2002年 | 95篇 |
2001年 | 102篇 |
2000年 | 81篇 |
1999年 | 72篇 |
1998年 | 65篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 34篇 |
1994年 | 31篇 |
1993年 | 16篇 |
1992年 | 20篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有4431条查询结果,搜索用时 15 毫秒
181.
Avanish Bharati Prakhyat Hejmady Tom Van der Donck Jin Won Seo Ruth Cardinaels Paula Moldenaers 《应用聚合物科学杂志》2020,137(9):48433
An approach to induce conductivity in immiscible polystyrene/polypropylene (PS/PP) blends is described using a percolated conducting polyaniline/polyamide (PANI/PA) filler combined with a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleic anhydride compatibilizer. The approach is based on the ability of the compatibilizer to concomitantly stabilize the cocontinuous morphology and to improve the state of dispersion of the PANI/PA filler. Selective localization of PANI/PA in the PS phase with improved filler dispersion is achieved with the optimal master batch (MB) preparation technique followed by its optimized sequence addition to the blend components. This results in an increase in the dc conductivity by six decades as compared with that of the neat compatibilized blend at an effective 4.8-wt % PANI concentration. An investigation of the effect of functionality and concentration of the filler and the compatibilizer on the filler connectivity in the blend is performed. The prevailing specific interactions are analyzed by Fourier transform infrared spectroscopy and thermogravimetric analysis of the MBs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48433. 相似文献
182.
Sang Yoon Park Won Jong Choi Chi Hoon Choi Heung Soap Choi 《Journal of Adhesion Science and Technology》2018,32(11):1200-1223
The effects of cure temperatures on the thermal, physical and mechanical characteristics of two types of thermosetting structural epoxy film adhesives were determined in detail. The aim of this paper is to assess the effect of cure temperatures (82–121 °C) on the degree of cure of the two adhesives and the relevant void formations that need to be addressed in bonded part production and repair. Two thermal parameters were used to characterize the advancement of the reaction, such as degree of cure and glass transition temperature. The joint properties with respect to the cure temperatures were characterized by void content and bond-line thickness measurements and lap shear strength tests. Experimental results presented that all lap shear strengths were well within minimum shear strength (29 MPa) required by the specification of the film-type adhesive. However, the lap shear strength testing after aging at 82 °C and 95%R.H for 1000 h showed that the improved durability when the adhesive is cured at 121 °C did not occur for the 82 °C cure. Low curing conversion (75–77% degree of cure) combined with high voids (over 2 areal%) has a catastrophic effect on the bonding qualities at the metal-adhesive interface and due to lack of cohesion in the adhesive. The changes in the interface caused by the low temperature curing may contribute to an increased susceptibility of the bonded joint to moisture and consequent bond-line degradation. 相似文献
183.
Byeong Kon Kim Yong Soo Cho Jung Won Lee Jong Won Lee Jun Kwang Song 《Journal of the American Ceramic Society》2008,91(2):687-689
The compatibility and crystallization of dielectric thick films, consisting of a bismuth borosilicate glass and crystalline cordierite, on a LiZn ferrite substrate were investigated by focusing on phase development and microstructural changes. Significant diffusion of Li and Fe from the substrate to the dielectric was confirmed as unexpected crystalline phases such as Li2 Al2 Si3 O10 and Fe2 O3 were found in the thick films fired at 850°C. The crystallization was believed to be initiated from the film interface and developed further toward the film surface as evidenced from cross-sectional microstructures of the films with additional firings. The degree of crystallization and the relative contents of the observed phases were dependent on the ratio between the glass and cordierite and the number of refirings. 相似文献
184.
Seon Mi Kong Rong Fan Sung Hee Jung Chee Won Chung 《Journal of Industrial and Engineering Chemistry》2013,19(4):1320-1324
Cu(In1?xGax)Se2 (CIGS) thin films were prepared using a single quaternary target by RF magnetron sputtering. The effects of deposition parameters on the structural, compositional and electrical properties of the films were examined in order to develop the deposition process without post-deposition selenization. From X-ray diffraction analysis, as the substrate temperature and Ar pressure increased and RF power decreased, the crystallinity of the films improved. The scanning electron microscopy revealed that the grains became uniform and circular shape with columnar structure with increasing the substrate temperature and Ar pressure, and decreasing the RF power. The carrier concentration of CIGS films deposited at the substrate temperature of 500 °C was 2.1 × 1017 cm?3 and the resistivity was 27 Ω cm. At the substrate temperature above 500 °C, In and Se contents in CIGS films decreased due to the evaporation and it led to the deterioration of crystallinity. It was confirmed that CIGS thin films deposited at optimal condition had similar atomic ratio to the target value even without post-deposition selenization process. 相似文献
185.
The thermal and kinetic effects of O3 on flame propagation were investigated experimentally and numerically by using C3H8/O2/N2 laminar lifted flames. Ozone produced by a dielectric barrier plasma discharge was isolated and measured quantitatively by using absorption spectroscopy. Significant kinetic enhancement by O3 was observed by comparing flame stabilization locations with and without O3 production. Experiments at atmospheric pressures showed an 8% enhancement in the flame propagation speed for 1260 ppm of O3 addition to the O2/N2 oxidizer. Numerical simulations showed that the O3 decomposition and reaction with H early in the pre-heat zone of the flame produced O and OH, respectively, from which the O reacted rapidly with C3H8 and produced additional OH. The subsequent reaction of OH with the fuel and fuel fragments, such as CH2O, provided chemical heat release at lower temperatures to enhance the flame propagation speed. It was shown that the kinetic effect on flame propagation enhancement by O3 reaching the pre-heat zone of the flame for early oxidation of fuel was much greater than that by the thermal effect from the energy contained within O3. For non-premixed laminar lifted flames, the kinetic enhancement by O3 also induced changes to the hydrodynamics at the flame front which provided additional enhancement of the flame propagation speed. The present results will have a direct impact on the development of detailed plasma-flame kinetic mechanisms and provided a foundation for the study of combustion enhancement by O2(a1Δg) in part II of this investigation. 相似文献
186.
The effects of sample size, liquid loading, particle size, column length, and column temperature on retention volumes were
studied and separation factor, column efficiency, partition coefficient, and heat of solution were also obtained by gas-liquid
chromatography. The feed materials were chosen by similar boiling points as diethylether, dimethoxymethane and dichloromethane.
The relations between retention volume and above mentioned various variables were obtained. Separation factor was more affected
by column temperature than other variables, and decreased with the temperature. HETP increased almost linearly with sample
size. From the exponential relationship between partition coefficient and column temperature heat of solution of each material
was calculated. 相似文献
187.
The effects of solution properties and polyelectrolyte on the electrospinning of poly(ethylene oxide) (PEO) solutions were investigated. Ultrafine PEO fibers without beads were electrospun from 3, 4, 7 and 7 wt% PEO solutions in chloroform, ethanol, (dimethylformamide) DMF and water, respectively. At these concentrations, the values of [η]C were ∼10 for all solutions. The average diameters of PEO fibers were ranged from 0.36 to 1.96 μm. The higher the dielectric constant of solvent was, the thinner PEO fiber was. The average diameters of electrospun PEO fibers from PEO/water solutions were decreased and their distributions were narrowed by adding 0.1 wt% poly(allylamine hydrochloride) (PAH) and poly(acrylic acid sodium salt) (PAA) due to the increased charge density in solutions. The addition of PAH and PAA lowered the minimum concentration for electrospinning of a PEO/water solution to 6 wt%. 相似文献
188.
To prepare high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with high yield and high linearity which is a promising precursor for syndiotactic poly (vinyl alcohol) (PVA), vinyl pivalate (VPi) was emulsion polymerized, using 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH) as an initiator and sodium dodecyl sulfate (SDS) as an emulsifier. The effect of the polymerization conditions on the conversion, molecular weight, and degree of branching was investigated. PVA with maximum number‐average degree of polymerization (Pn) of 6200 could be prepared by complete saponification of PVPi, with Pn of 13,300–16,700 obtained at polymerization temperature of 50°C, using SDS and AAPH concentration of 2.0 × 10?3 mol/L of water and 1.0 × 10?3 mol/L of water, respectively, and the maximum conversion was about 90%. From the emulsion polymerization of VPi, spherical PVPi with high yield was effectively prepared, which might be useful for the precursor of syndiotactic PVA micro‐ and nano‐spheres with various surface properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 410–414, 2007 相似文献
189.
Yong S. Chung Sung I. Kang Oh W. Kwon Se G. Lee Yong R. Lee Byung G. Min Sung S. Han Seok K. Noh Won S. Lyoo 《应用聚合物科学杂志》2007,104(5):3240-3244
Biocompatible hydroxyapatite (HA)/poly(vinyl alcohol) (PVA) composites and their transparent films were prepared by the coprecipitation and solvent casting method. The formation of HA in PVA composite powder was confirmed by the characteristic phosphate bands at 1100–1032 and 565 cm?1 at FT‐IR spectra, and the weight ratio of HA to PVA was 50/50 examined by TGA. The crystal melting temperature of HA/PVA decreased compared with that of pure PVA. HA/PVA (50/50) composite powder and pure PVA were dissolved in dimethyl sulfoxide to obtain a film with HA/PVA weight ratio of 10/90. To improve HA particles' dispersity, which is one of the major factors affecting the mechanical properties of composite materials, various contents of citric acid were used for the preparation of HA/PVA films. At a citric acid concentration of 5 wt %, HA/PVA film with good dispersity of HA particles was obtained. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
190.
High thermal conductivity of spark plasma sintered silicon carbide ceramics with yttria and scandia
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yu‐Kwang Seo Young‐Wook Kim Toshiyuki Nishimura Won‐Seon Seo 《Journal of the American Ceramic Society》2017,100(4):1290-1294
A fully dense SiC ceramic with a room‐temperature thermal conductivity of 262 W·(m·K)?1 was obtained via spark plasma sintering β‐SiC powder containing 0.79 vol% Y2O3‐Sc2O3. High‐resolution transmission electron microscopy revealed two different SiC‐SiC boundaries, that is, amorphous and clean boundaries, in addition to a fully crystallized junction phase. A high thermal conductivity was attributed to a low lattice oxygen content and the presence of clean SiC‐SiC boundaries. 相似文献