全文获取类型
收费全文 | 12807篇 |
免费 | 393篇 |
国内免费 | 58篇 |
专业分类
电工技术 | 260篇 |
综合类 | 16篇 |
化学工业 | 2274篇 |
金属工艺 | 367篇 |
机械仪表 | 361篇 |
建筑科学 | 219篇 |
矿业工程 | 73篇 |
能源动力 | 703篇 |
轻工业 | 1171篇 |
水利工程 | 190篇 |
石油天然气 | 82篇 |
无线电 | 1623篇 |
一般工业技术 | 2771篇 |
冶金工业 | 1544篇 |
原子能技术 | 198篇 |
自动化技术 | 1406篇 |
出版年
2024年 | 39篇 |
2023年 | 177篇 |
2022年 | 505篇 |
2021年 | 504篇 |
2020年 | 409篇 |
2019年 | 407篇 |
2018年 | 553篇 |
2017年 | 512篇 |
2016年 | 483篇 |
2015年 | 280篇 |
2014年 | 446篇 |
2013年 | 886篇 |
2012年 | 518篇 |
2011年 | 676篇 |
2010年 | 540篇 |
2009年 | 531篇 |
2008年 | 476篇 |
2007年 | 389篇 |
2006年 | 331篇 |
2005年 | 263篇 |
2004年 | 244篇 |
2003年 | 219篇 |
2002年 | 180篇 |
2001年 | 143篇 |
2000年 | 147篇 |
1999年 | 156篇 |
1998年 | 355篇 |
1997年 | 231篇 |
1996年 | 251篇 |
1995年 | 219篇 |
1994年 | 182篇 |
1993年 | 171篇 |
1992年 | 143篇 |
1991年 | 151篇 |
1990年 | 114篇 |
1989年 | 108篇 |
1988年 | 130篇 |
1987年 | 109篇 |
1986年 | 89篇 |
1985年 | 115篇 |
1984年 | 94篇 |
1983年 | 107篇 |
1982年 | 99篇 |
1981年 | 88篇 |
1980年 | 78篇 |
1979年 | 54篇 |
1978年 | 46篇 |
1977年 | 56篇 |
1976年 | 76篇 |
1975年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
Harmesh Kumar Rajesh Choudhary Shankar Singh 《Journal of Materials Engineering and Performance》2014,23(4):1489-1497
In this study, a special experimental setup of EDSG using EDM and surface grinding machine has been developed in the laboratory to investigate the effect of seven input parameters namely tool polarity, peak current, pulse on-time, pulse off-time, rotational speed, abrasive particle size, and abrasive particle concentration on material removal rate (MRR) as performance measure of the process. The novelty of the present research work is that successful efforts have been made to machine the 6061Al/Al2O3p 10% metal matrix composites (MMC) by composite tool itself. The copper-based composite tool electrodes were fabricated by powder metallurgy route with different sizes of abrasives of silicon carbide, while 6061Al/Al2O3p 10% MMC were fabricated through stir-casting process. The research outcome will identify the important parameters and their effect on MRR of 6061Al/Al2O3p 10% composite in EDSG. The experimental results reveal that tool polarity, peak current, and rotational speed are the most influential parameters that affect MRR in EDSG process. The micro-structural and morphological analysis of machined surfaces has also been carried out to analyze the surface topography. It has been concluded that the abrasive particles substantially improves the MRR after removing the resolidified layer from the machined surface. 相似文献
983.
Chin Yung Lai Choke Fei Cheong Jit Singh Mandeep Huda Binti Abdullah Nowshad Amin Khin Wee Lai 《Journal of Materials Engineering and Performance》2014,23(10):3541-3550
The synthesis of silver nanoparticles for silver ink formation has attracted broad interest in the electronic part printing and semiconductor chip industry due to the extraordinary electrical and mechanical properties of these materials. The preparation of silver nanoparticles through a physical or chemical reduction process is the most common methodology applied to obtain nanoparticles with the required size, shape and surface morphology. The chemical solution or solvent carrier applied for silver ink formulation must be applied simultaneously with the direct writing technique to produce the desired adherence, viscosity, and reliable performance. This review paper discusses the details concerning the past and recent advancement of the synthesis and characterization of silver nanoparticles and silver ink formation. A review on the advantages of various sintering techniques, which aim to achieve the electrical and mechanical properties of the required printed structure, is also included. A brief summary concerning the recent challenges and improvement approaches is presented at the end of this review. 相似文献
984.
Deepa Mudgal Sanjeet Kumar Surendra Singh Satya Prakash 《Journal of Materials Engineering and Performance》2014,23(11):3805-3818
Cr3C2-25(NiCr) and Cr3C2-25(NiCr)+0.4%CeO2 coatings were deposited on nickel-based superalloy Superni 600 by Detonation-gun technique. Studies were conducted on bare and coated alloys in molten salt environment (Na2SO4-25%NaCl) at 900 °C under cyclic condition. Characterization of the corrosion product was done using field emission scanning electron microscopy/energy dispersive spectroscopy and x-ray diffraction techniques. The bare Superni 600 shows penetration of corrosion beneath the metal layer thereby indicating internal oxidation. The coating of Cr3C2-25(NiCr) with 0.4%CeO2 leads to the formation of adherent scale. 相似文献
985.
P. K. Rai Vaibhav Pandey K. Chattopadhyay L. K. Singhal V. Singh 《Journal of Materials Engineering and Performance》2014,23(11):4055-4064
The effect of ultrasonic shot peening (USSP) was studied on microstructural modification and mechanical properties such as microhardness, yield strength, tensile strength, and low cycle fatigue (LCF) life of a nitrogen stabilized austenitic stainless steel, at room temperature. There was grain refinement up to nano scale in surface region of the shot peened specimens and the microhardness was increased markedly up to the depth of approximately 100 µm. There was insignificant increase in yield and tensile strength, but drastic reduction in LCF life, particularly at low strain amplitude, from USSP. The nominal increase in yield and tensile strength was due to grain refinement in the surface region and drastic fall in LCF life was due to surface cracking resulting from USSP. 相似文献
986.
V. Singh J. S. Kachhawaha V. B. Tare 《Journal of Materials Engineering and Performance》2014,23(9):3285-3298
Corrosion behavior of annealed 9Cr-1Mo steel was studied in SO2 environment at 1173 K, at flow rates from 8.33 × 10?7 to 33.33 × 10?7 m3/s, and parabolic rate law was followed. The rate constants were found to be independent of flow rate, within the range of flow rate investigated. Corrosion at temperatures from 973 to 1173 K, at a constant flow rate of 16.66 × 10?7 m3/s, at 1 atmospheric pressure, for 6 h also exhibited parabolic law, however, the rate constants were observed to increase significantly with rise in temperature. The outer layer of the scale formed at 973 K was essentially of iron oxide, with small amount of chromium oxide whereas the inner layer was predominantly of chromium sulphide and chromium oxide. The scale formed at 1173 K was multilayered, in contrast to double layered formed at 973 K and 1073 K. The outer thick layer of the scale formed at 1173 K, consisted of iron oxide followed by thin substrate of chromium sulphide, iron sulphide/iron oxide, and chromium sulphide/chromium oxide toward the substrate. A model is proposed for the process of corrosion of 9Cr-1Mo steel in SO2 environment, based on the present investigation. 相似文献
987.
Cellulose is the main building block of plant's cell wall that provides structural stability. This idea inspired us to use modified cellulose (Networked cellulose) to provide thermal and mechanical stability to a polymer electrolyte system. The system composed of polyethylene glycol (PEG) (or tetraethylene glycol dimethyl ether (TEGDME)), polyethylene oxide (PEO), networked cellulose (NC) and LiClO4 as a salt. The PEG (or TEGDME) was used as a high mobility phase for lithium ions, PEO acted as a binder and NC provided structural support for the quasi-solid polymer electrolytes. A high conductivity of the order of 10−4 S cm−1 was obtained at room temperature. Dynamic mechanical analysis of PEG (or TEGDME):PEO:NC (70:20:10 wt%) showed an improvement of storage modulus as compared to the pristine PEO in the 60–120 °C temperature range. Differential scanning calorimetry (DSC)/Thermal gravimetry analysis (TGA) revealed that the developed ternary polymer electrolyte is thermally stable in the lithium-ion battery operational temperature range. 相似文献
988.
To enhance the production of biohydrogen from biomass, various pretreatment methods play important role. In this study, effect of microwave irradiation on the culture was studied on biohydrogen production from Benincasa hispida (Petha) solid waste at different powers for a fixed interval of time. The highest power studied was 800 W with a frequency of 2450 MHz. The amount of soluble sugars found in the waste was 13.9 mg/L having the chemical oxygen demand (COD) of 3000 mg/L. Studies have been performed in batch reactors using mixed consortia and results were also compared with the reactor operated at the normal conditions i.e. without any inoculum pretreatment. Maximum hydrogen produced was 14 mmol H2 per mol of soluble sugar consumed in the reactor in which the inoculum was exposed to 320 W of microwave for 5 min. SEM analysis of this microwave pretreated culture was done. 相似文献
989.
Ying Ma Manish Singh Xiaodi Wang Fan Yang Qiuan Huang Bin Zhu 《International Journal of Hydrogen Energy》2014
Development of low-temperature solid oxide fuel cells (LTSOFC) is now becoming a mainstream research direction worldwide. The advancement in the effective electrolyte materials has been one of the major challenges for LTSOFC development. To further improve the performance of electrolyte, composite approaches are considered as common strategies. The enhancement on ionic conductivity or sintering behavior ceria-based electrolyte can either be done by adding a carbonate phase to facilitate the utilization of the ionic-conducting interfaces, or by addition of alumina as insulator to reduce the electronic conduction of ceria. Thus the present report aims to design a composite electrolyte materials by combining the above two composite approaches, in order to enhance the ionic conductivity and to improve the long-term stability simultaneously. Here we report the preparation and investigation of GDC-KAlZn materials with composition of Gd doped ceria, K2CO3, ZnO and Al2O3. The structure and morphology of the samples were characterized by XRD, SEM, etc. The ionic conductivity of GDC-KAlZn sample was determined by impedance spectroscopy. The composite samples with various weight ratio of GDC and KAlZn were used as electrolyte material to fabricate and evaluate fuel cells as well as investigate the composition dependent properties. The good ionic conductivity and notable fuel cell performance of 480 mW cm−2 at 550 °C has demonstrated that GDC-KAlZn composite electrolyte can be regarded as a potential electrolyte material for LTSOFCs. 相似文献
990.
The photopolymerization of styrene with a well‐defined molecular architecture and a low polydispersity index and with methyl and phenylseleno (? SePh) groups at α‐ and ω‐chain ends, respectively, was performed via a controlled/living radical polymerization with a new initiating system, 1‐(phenylseleno)ethyl benzene/tert‐butyl diphenyl (phenylseleno) silane, through the absorption of visible light at room temperature. A novel initiating living radical polymerization was examined. The yield and number‐average molecular weight (Mn) of the resulting polymer increased with the reaction time. Furthermore, a linear relationship was found in a plot of Mn versus the polymer yield. These results indicated that this polymerization proceeded through a living radical mechanism. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 348–355, 2004 相似文献