全文获取类型
收费全文 | 1603篇 |
免费 | 75篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 17篇 |
综合类 | 4篇 |
化学工业 | 554篇 |
金属工艺 | 98篇 |
机械仪表 | 24篇 |
建筑科学 | 33篇 |
矿业工程 | 2篇 |
能源动力 | 63篇 |
轻工业 | 217篇 |
水利工程 | 5篇 |
石油天然气 | 35篇 |
无线电 | 144篇 |
一般工业技术 | 282篇 |
冶金工业 | 33篇 |
原子能技术 | 11篇 |
自动化技术 | 167篇 |
出版年
2023年 | 20篇 |
2022年 | 58篇 |
2021年 | 84篇 |
2020年 | 64篇 |
2019年 | 79篇 |
2018年 | 102篇 |
2017年 | 65篇 |
2016年 | 68篇 |
2015年 | 55篇 |
2014年 | 85篇 |
2013年 | 136篇 |
2012年 | 75篇 |
2011年 | 105篇 |
2010年 | 72篇 |
2009年 | 62篇 |
2008年 | 50篇 |
2007年 | 34篇 |
2006年 | 34篇 |
2005年 | 20篇 |
2004年 | 33篇 |
2003年 | 27篇 |
2002年 | 25篇 |
2001年 | 11篇 |
2000年 | 16篇 |
1999年 | 21篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 12篇 |
1995年 | 19篇 |
1994年 | 15篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 6篇 |
排序方式: 共有1689条查询结果,搜索用时 15 毫秒
101.
Structural Control of NiO–YSZ/LSCF–YSZ Dual‐Layer Hollow Fiber Membrane for Potential Syngas Production
下载免费PDF全文
![点击此处可从《International Journal of Applied Ceramic Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mohd Hilmi Mohamed Mohd Hafiz Dzarfan Othman Muhazri Abd Mutalib Mukhlis Rahman Juhana Jaafar Ahmad Fauzi Ismail Mohd Irfan Hatim Mohamed Dzahir 《International Journal of Applied Ceramic Technology》2016,13(5):799-809
The objective of this study was to fabricate dual‐layer hollow fiber as a microreactor for potential syngas production via phase inversion‐based co‐extrusion/cosintering process. As the main challenge of phase inversion is the difficulty to obtain defect‐free fiber, this work focuses on the effect of the fabrication parameters, that is, nonsolvent content, sintering temperature and outer‐layer extrusion rate, on the macrostructure of the produced hollow fiber. SEM images confirm that the addition of nonsolvent has successfully minimized the finger‐like formation. At high sintering temperature, more dense hollow fiber was formed while outer‐layer extrusion rate affects the outer layer thickness. 相似文献
102.
Abdul Latif Ahmad Choe Peng Leo Syamsul Rizal Abd. Shukor 《Journal of Porous Materials》2009,16(1):33-40
Porous γ-alumina with well arranged secondary mesopores has been contrived using nanosized templating units. The pore size
of templated mesopores is precisely controlled as the pore shrinkage is insignificant. The primary pore diameter is ca. 4 nm
and the secondary pore diameter is ca. 50 nm. The porous material was characterized using N2 adsorption/desorption, TEM, XRD and FT-IR. γ-alumina with bimodal pore size distribution shows improved intra-particle diffusion
compared to γ-alumina with unimodal pore size distribution in a simple dye adsorption test. γ-alumina with different porous
structures were then impregnated with vanadium oxide for catalytic effect comparison. It was perceived that secondary pores
improve the styrene oxidation rate after the conversion of styrene reaches 30%. 相似文献
103.
The protection of some poly(methyl methacrylate) (PMMA) samples against γ rays was investigated in the absence and presence of poly(p‐sulfanilamide). Pure PMMA (without additives) and PMMA–poly(p‐sulfanilamide) blend samples were irradiated with γ rays for different exposure doses (5, 15, 25, 35, 50, 75, and 100 kGy). The viscosity‐average molecular weights were determined and thin‐layer chromatography measurements were carried out after each irradiation dose. The maximum protection against γ rays was found when 1% poly(p‐sulfanilamide) was used. The radiation chemical yield for main scission (Gs) was calculated and had lower values in the case of 1% poly(p‐sulfanilamide). The energy absorption per scission was maximum for 1% poly(p‐sulfanilamide), and this confirmed the obtained Gs data. From thin‐layer chromatography studies, it was observed that both the retention factor (Rf) values and polydispersity of the PMMA samples increased with an increasing exposure dose. The effect of γ irradiation on PMMA films doped with 1% poly(p‐sulfanilamide) was investigated with UV spectroscopy after the extraction of the additives. A change in the intensity of the absorption bands with an increasing irradiation dose was recorded. It is suggested that PMMA films doped with this type of polymer can be used as dosimeters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
104.
Abd-Elnaiem Alaa M. Abd El-Baki Randa F. Alsaaq Faisal Orzechowska Sylwia Hamad D. 《Journal of Inorganic and Organometallic Polymers and Materials》2022,32(4):1191-1205
Journal of Inorganic and Organometallic Polymers and Materials - The fabrication of graphene/graphene oxide bounded metal nanostructures, to form hybrid composites, and their utilization for the... 相似文献
105.
E. E. Abd El Aal W. Zakria A. Diab S. M. Abd El Haleem 《Journal of Materials Engineering and Performance》2003,12(2):172-178
The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The
reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel
slope equal to 120 ± 10 mV · decade−1 was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and
increasing temperature. The activation energy, ΔH, for the anodic dissolution process was found to be 12 kcal · mol−1. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its
derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These
compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of
such inhibitors could not interfere with the mechanism of metal dissolution. 相似文献
106.
Asmaa M. Abu El-Soad Giuseppe Lazzara Mahmoud O. Abd El-Magied Giuseppe Cavallaro Jamelah S. Al-Otaibi M. I. Sayyed Elena G. Kovaleva 《International journal of molecular sciences》2022,23(4)
The modification of chitosan represents a challenging task in obtaining biopolymeric materials with enhanced removal capacity for heavy metals. In the present work, the adsorption characteristics of chitosan modified with carboxyl groups (CTS-CAA) towards copper (II) and zinc (II) ions have been tested. The efficacy of the synthesis of CTS-CAA has been evaluated by studying various properties of the modified chitosan. Specifically, the functionalized chitosan has been characterized by using several techniques, including thermal analyses (differential scanning calorimetry and thermogravimetry), spectroscopies (FT-IR, XRD), elemental analysis, and scanning electron microscopy. The kinetics and the adsorption isotherms of CTS-CAA towards both Cu (II) and Zn (II) have been determined in the aqueous solvent under variable pH. The obtained results have been analyzed by using different adsorption models. In addition, the experiments have been conducted at variable temperatures to explore the thermodynamics of the adsorption process. The regeneration of CTS-CAA has been investigated by studying the desorption process using different eluents. This paper reports an efficient protocol to synthesize chitosan-based material perspective as regenerative adsorbents for heavy metals. 相似文献
107.
Modification of starch with urea was carried out at 165 °C according to solid state, paste and film techniques. With the solid state and paste techniques the extent of the reaction, expressed as % N, increased by increasing the time of treatment. Samples prepared by the film technique showed, during the first 15 min reaction time, significantly higher nitrogen content which, however, decreased by prolongation of the treatment. Infra-red spectrum of the reaction products indicated involvement of both starch and urea in a chemical reaction. Examination of the swelling properties of the products revealed that these properties are dependent upon the technique used for preparation rather than the extent of the reaction. Samples prepared by the paste and film techniques acquired higher apparent viscosity than those prepared by the solid state technique irrespective of the rate of shear. For a given rate of shear, the apparent viscosity increases by increasing the temperature. 相似文献
108.
Emad A. Elaty Mohammed Abd-Elnaby Saied M. Abd El-atty Sami A. El-Dolil Moawad I. Dessouky Fathi E. Abd El-Samie 《Wireless Personal Communications》2018,99(2):597-617
Overcoming periodic blockage of the received signal and the carrier frequency fluctuations caused by rotor blades and Doppler shift, respectively, are considered the most challenging issues in helicopter-satellite communication systems. In this study, we propose an automatic frequency control method based on an adaptive modulation scheme. We employ a hybrid modulation not only depending on quadrature phase shift keying, but also based on binary phase shift keying for accurate cancellation of periodic blockage. On the other hand, we apply a chaotic interleaving scheme with a hybrid modulation scheme in order to achieve a better Bit Error Rate (BER) performance in LOS and NLOS environments. Finally, we validate the mathematical analysis of the proposed scheme through simulations. We evaluated the performance of the proposed scheme and performed a comparison with conventional schemes. Our results show that the proposed scheme is significantly capable of reducing the acquisition time and working with various velocities of helicopter blades in addition to providing a better BER performance in shadow fading environments. 相似文献
109.
Graphite is a bulk-layered material that can be separated into sheets which exhibit folds and pleat-like structures. Graphene sheets are easily obtained via an exfoliation process using graphite in organic solvent. Spin-coated graphene:poly(3-hexylthiophene) (P3HT) blend films are characterized by absorption and photoluminescence spectroscopy measurements. Doping of 2.5% graphene into P3HT induces better light absorption and photoluminescence quenching in the blend film. This finding indicates that graphene is a potential alternative material in various applications such as an acceptor material in organic solar cells. 相似文献
110.
Abdüsselam Altunkaynak 《Advances in Engineering Software》2009,40(9):928-934
Accurate sediment load prediction is very important in planning, designing, operating and maintenance of water resources structures. Various models have been developed so far to identify the relation between discharge and sediment load. Most of the models based on regression method (RM) have some restrictive assumptions. This method is able to provide only one solution point for estimation of sediment amount. On the other hand, genetic algorithms (GAs) can produce more than one solution points providing optimal relation between discharge and sediment loads. Sediment load can be successfully predicted from discharge measurements by using GAs. Graphical and numerical data are presented to compare GAs with RM. GA methodology is applied to discharge and sediment load data obtained from Mississippi river at Missouri, St. Louis. It is found that GAs outperform RM in terms of mean relative error (MRE). 相似文献