全文获取类型
收费全文 | 1096篇 |
免费 | 51篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 239篇 |
金属工艺 | 28篇 |
机械仪表 | 35篇 |
建筑科学 | 32篇 |
矿业工程 | 2篇 |
能源动力 | 64篇 |
轻工业 | 110篇 |
水利工程 | 21篇 |
石油天然气 | 6篇 |
无线电 | 109篇 |
一般工业技术 | 278篇 |
冶金工业 | 90篇 |
原子能技术 | 20篇 |
自动化技术 | 104篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 51篇 |
2021年 | 37篇 |
2020年 | 44篇 |
2019年 | 45篇 |
2018年 | 58篇 |
2017年 | 52篇 |
2016年 | 58篇 |
2015年 | 34篇 |
2014年 | 44篇 |
2013年 | 84篇 |
2012年 | 57篇 |
2011年 | 69篇 |
2010年 | 56篇 |
2009年 | 44篇 |
2008年 | 30篇 |
2007年 | 34篇 |
2006年 | 27篇 |
2005年 | 22篇 |
2004年 | 21篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1971年 | 5篇 |
1970年 | 2篇 |
排序方式: 共有1156条查询结果,搜索用时 109 毫秒
101.
Cross-sectional transmission electron microscopy is used to determine the structure of Au-, Ge- and Ni-based ohmic contacts at the interface with AlGaAs/GaAs modulation-doped field-effect-transistor material. Significant lateral diffusion (?0.12?m) is found to occur at the edge of the contact during alloying. The observed contact structure places a limit on minimum geometries and must be taken into account if accurate device modelling is to be carried out. 相似文献
102.
Kumud Ranjan Jha Manish Rai 《AEUE-International Journal of Electronics and Communications》2010,64(2):177-185
This paper presents a new slow wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of different kind of coupling in this structure is demonstrated. Two and four resonator band pass filters at center frequency 2.15 and 2.30 GHz with different bandwidth are designed. The simulated results are verified with the help of two different software packages (IE3D and Sonnet Lite). 相似文献
103.
Anurag Jyoti Poornima Vajpayee Premendra D. Dwivedi Rishi Shanker 《The Science of the total environment》2010,408(6):1256-9002
Low numbers (15-100 CFU) of Salmonella in food or water may pose a public health risk. The management of infections caused by Salmonella spp. during outbreaks or forecasting of contamination of aquatic resources largely depends on rapid, sensitive and accurate diagnostic in few hours. In this study, a real-time PCR assay in Molecular-Beacon format was developed and culture-independent quantitative enumeration of Salmonella spp. in surface and potable water is being reported for the first time from northern part of India. Molecular Beacon was designed in highly conserved region of invA gene (present in wide range of Salmonella serotypes including all subspecies) encoding an essential component of the invasion associated specialized type Ø protein secretion apparatus for detection of Salmonella spp. in water. The assay could detect directly 10 and 1 genomic equivalent of Salmonella typhimurium ATCC 14028 per PCR with detection probability of 100 and 20%, respectively. Further, the assay could detect 10 CFU/PCR or more of reference strain (S. typhimurium ATCC 14028) without any enrichment in the presence of 108 CFU ml− 1 of non-pathogenic E. coli (E. coli DH5α) with 100% detection probability. The assay could enumerate Salmonella spp. in surface (n = 40) and potable waters (n = 10) directly (without enrichment). Results indicate that northern India is at high risk of developing Salmonella borne infections. Further, real-time PCR assay in Molecular Beacon format can be used for identification of critical contamination points in natural water resources and potable water distribution systems, necessary to implement vaccination plan timely for prevention of waterborne outbreaks caused by Salmonella spp. 相似文献
104.
Three samples of vinyl ester resins (VERs) were synthesized using bisphenol‐A‐based epoxy resins of varying epoxide equivalent weights (EEW) and acrylic acid in presence of triphenylphosphine as a catalyst at 80 ± 2°C. The cresyl glycidyl ether was used as reactive diluent during the synthesis of VERs. A suitable reaction mechanism was proposed and discussed for the reactions involving epoxide group and acid groups. This was further confirmed by infrared spectroscopic analysis. The maximum peak temperature from DSC were at 106.05°C, 114.20°C, and 128.86°C for benzoyl peroxide initiated VERs viz. samples V1CV, V2CV, and V3CV, respectively, increased with the increase of EEW of the parent epoxy resin. It has also been found that the films of VER having highest EEW of bisphenol‐A epoxy resin showed best chemical resistance amongst all other VERs in this study. The mechanical properties such as hardness and flexibility also showed a similar trend. The thermal stability was found to decrease with the increase of EEW of bisphenol‐A epoxy resin in the VERs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
105.
Savita Kaul Jyoti Porwal M. O. Garg 《Journal of the American Oil Chemists' Society》2010,87(8):903-908
The purpose of the present study was to reduce the cost and increase the efficiency of biodiesel production by reactive extraction
(in situ) of Jatropha seeds. Oil from the seeds was extracted and reacted in a single step. Experimental studies have been
carried out to maximize the yield of biodiesel by varying the reaction parameters viz. seed size (<0.85 mm to >2.46 mm), seed/solvent
ratio (w/w) (1:2.6–1:7.8) and catalyst concentration (0.05–0.1 M). Under the optimized conditions: seed size (>2.46 mm), seed/solvent
ratio (w/w) (1:7.8), catalyst concentration (0.1 M) and reaction time 1 h, approximately 98% conversion to biodiesel was achieved
meeting International (ASTM) as well as National (BIS) specifications. The results were supported by HPLC analysis. 相似文献
106.
107.
Identification of yeast strains isolated from marcha in Sikkim, a microbial starter for amylolytic fermentation 总被引:1,自引:0,他引:1
Tsuyoshi N Fudou R Yamanaka S Kozaki M Tamang N Thapa S Tamang JP 《International journal of food microbiology》2005,99(2):135-146
Marcha or murcha is a traditional amylolytic starter used to produce sweet-sour alcoholic drinks, commonly called jaanr in the Himalayan regions of India, Nepal, Bhutan, and Tibet (China). The aim of this study was to examine the microflora of marcha collected from Sikkim in India, focusing on yeast flora and their roles. Twenty yeast strains were isolated from six samples of marcha and identified by genetic and phenotypic methods. They were first classified into four groups (Group I, II, III, and IV) based on physiological features using an API test. Phylogenetic, morphological, and physiological characterization identified the isolates as Saccharomyces bayanus (Group I); Candida glabrata (Group II); Pichia anomala (Group III); and Saccharomycopsis fibuligera, Saccharomycopsis capsularis, and Pichia burtonii (Group IV). Among them, the Group I, II, and III strains produced ethanol. The isolates of Group IV had high amylolytic activity. Because all marcha samples tested contained both starch degraders and ethanol producers, it was hypothesized that all four groups of yeast (Group I, II, III, and IV) contribute to starch-based alcohol fermentation. 相似文献
108.
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
109.
Pt–Ru catalysts supported on mesoporous carbon nitride (MCN), multiwall carbon nano tubes (MWCNTs), treated MWCNTs (t-MWCNTS) and Vulcan-XC were prepared using co-impregnation reduction method for the oxidation of ethanol in direct ethanol fuel cell (DEFC) to study the effect of support material. The MCN support was prepared using SBA-15 as template and t-MWCNTs were prepared by refluxing in HNO3 and H2SO4 mixture (1:3) using MWCNTs. XRD shows the formation of Pt–Ru bi-metallic catalyst with size ranges from 7 to 17 nm using different supports. The catalyst and its supports were characterized by physically and electrochemically. Linear sweep voltammetry, cyclic voltammetry and chrono amperometry studies of the above systems reveal that MCN supported Pt–Ru catalyst shows higher electro-catalytic activity towards ethanol oxidation compared to Pt–Ru in treated t-MWCNTs, MWCNts and Vulcan-XC supports. The performance of DEFC based on maximum power density is found to be in the order Pt–Ru/MCN > Pt–Ru/t-MWCNTs > Pt–Ru/MWCNTs > Pt–Ru/Vulcan-XC. The Pt–Ru/MCN shows highest power density of 61.1 mW cm−2 at 100 °C, 1 bar pressure with catalyst loading of 2 mg cm−2 using 2 M ethanol feed. 相似文献