全文获取类型
收费全文 | 5451篇 |
免费 | 175篇 |
国内免费 | 30篇 |
专业分类
电工技术 | 82篇 |
综合类 | 14篇 |
化学工业 | 1175篇 |
金属工艺 | 189篇 |
机械仪表 | 164篇 |
建筑科学 | 82篇 |
矿业工程 | 16篇 |
能源动力 | 300篇 |
轻工业 | 260篇 |
水利工程 | 40篇 |
石油天然气 | 13篇 |
无线电 | 840篇 |
一般工业技术 | 1321篇 |
冶金工业 | 492篇 |
原子能技术 | 43篇 |
自动化技术 | 625篇 |
出版年
2024年 | 18篇 |
2023年 | 78篇 |
2022年 | 155篇 |
2021年 | 235篇 |
2020年 | 142篇 |
2019年 | 147篇 |
2018年 | 188篇 |
2017年 | 159篇 |
2016年 | 180篇 |
2015年 | 120篇 |
2014年 | 184篇 |
2013年 | 363篇 |
2012年 | 228篇 |
2011年 | 294篇 |
2010年 | 233篇 |
2009年 | 240篇 |
2008年 | 221篇 |
2007年 | 182篇 |
2006年 | 180篇 |
2005年 | 125篇 |
2004年 | 109篇 |
2003年 | 102篇 |
2002年 | 93篇 |
2001年 | 98篇 |
2000年 | 86篇 |
1999年 | 79篇 |
1998年 | 145篇 |
1997年 | 100篇 |
1996年 | 82篇 |
1995年 | 74篇 |
1994年 | 94篇 |
1993年 | 88篇 |
1992年 | 68篇 |
1991年 | 77篇 |
1990年 | 54篇 |
1989年 | 36篇 |
1988年 | 38篇 |
1987年 | 43篇 |
1986年 | 49篇 |
1985年 | 41篇 |
1984年 | 57篇 |
1983年 | 35篇 |
1982年 | 43篇 |
1981年 | 36篇 |
1980年 | 43篇 |
1979年 | 40篇 |
1978年 | 27篇 |
1977年 | 34篇 |
1976年 | 37篇 |
1973年 | 13篇 |
排序方式: 共有5656条查询结果,搜索用时 15 毫秒
971.
B. K. Prasad 《Journal of Materials Engineering and Performance》2003,12(6):708-714
An attempt has been made in this investigation to assess the wear behavior of a zinc-based alloy in slurry. The influence
of the sand content of the slurry and traversal speed and distance on the wear response of the alloy has been examined. Tests
were also conducted in the liquid-only medium to assess the role played by the suspended sand particles in the medium. Testing
the samples in the liquid-only medium (i.e., without sand particles) caused maximum wear rate. It was also observed that an
intermediate sand concentration in the liquid exists wherein the samples experienced maximum wear rate (although less than
in the liquid-only medium). Further, increasing the speed of rotation of the specimens in the liquid plus sand environments
led to higher wear rate while the trend tended to reverse in the sand-free liquid environment. The alloy initially displayed
increased wear rate with increasing traversal distance. This was followed by the attainment of the maximum, a decrease in
the wear rate and then a steady state value at longer traversal distances. Wear behavior of the alloy under different experimental
conditions was further substantiated through the features of the affected wear surfaces and subsurface regions (perpendicular
below the affected surfaces). 相似文献
972.
Quasi-isotropic. laminates have isotropic elastic properties in all in-plane directions. Therefore, this kind of laminate is widely used for structural elements. The simplest stacking sequence of quasi-isotropic laminates is [0/-60/60]s. When the direction of applied axial load to [0/-60/60]s laminate is inclined at a 30-degree angle, we have the other quasi-isotropic laminate [30/-30/90]s under axial load. The failure mechanisms of these two laminates are, however, entirely different from each other because these two laminates have different distribution of the interlaminar stresses. It was confirmed by tensile fatigue tests that the [0/-60/60]s laminate does not show any visible fatigue damage, but the [30/-30/90]s laminate develops edge-delamination during cyclic loading. The analytical results were in good agreement with the experimental results. 相似文献
973.
Samuel L. Manzello Richard G. Gann Scott R. Kukuck Kuldeep R. Prasad Walter W. Jones 《Fire Technology》2007,43(1):77-89
A glass wall assembly was exposed to an intense real-scale compartment fire. The wall assembly consisted of four glass sections,
two of which were fitted with tempered double-pane glass and the other two sections were fitted with tempered single-pane
glass. At each glass section, temperatures were measured at the exposed face and the unexposed face. Total heat flux gauges
were used to measure both the temporal variation of the energy incident on the glass wall and the transmitted energy rate
detected through two of the glass sections. Visual and infrared cameras were used to image the unexposed face of each wall
assembly during the fire exposure. Results of glass breakage and subsequent glass fall out were compared to studies in the
literature for glass sections exposed to compartment fires. The behavior of the glass wall assembly under a fire load is presented.
相似文献
Samuel L. ManzelloEmail: |
974.
Optimisation of a process for production of pomegranate pulp and flaxseed powder fortified probiotic Greek dahi 下载免费PDF全文
Reeta Sudhir Kumar Prasad Rasane Ramadevi Nimmanapalli 《International Journal of Dairy Technology》2018,71(3):753-763
Fortified probiotic Greek dahi was formulated with pomegranate pulp (PP) and flaxseed powder (FP). The product variables, viz. PP, FP and incubation time, were optimised based on chemical, sensory and textural attributes. The study revealed that PP significantly affected the acidity and antioxidant content, while FP influenced the sensory and textural properties of the product. The optimum conditions were 15% PP, 2% FP and 12‐h incubation time. The developed fortified probiotic Greek dahi is a potential synbiotic food. 相似文献
975.
M. Venkataravanappa R.B. Basavaraj G.P. Darshan B. Daruka Prasad S.C. Sharma P. Hema Prabha S. Ramani H. Nagabhushana 《中国稀土学报(英文版)》2018,36(7):690-702
Latent fingerprints (LFPs) are the major physical evidences for the identification of individuals during crime spot investigation. Till date, numerous methods were followed to visualize LFPs. However, simple, accurate, and cost-effective method has wide scope in advanced forensic field. In our work, Ca2SiO4:Dy3+ nanopowders (NPs) were fabricated via solution combustion route. The optimized sample was employed for the visualization of overlapped LFPs by the cost effective powder dusting method. The obtained results reveals the complete three levels of ridge characteristics with high sensitivity, reproducibility, selectivity, and reliability on various complex surfaces. The photoluminescence (PL) spectra consist of intense peaks at ~ 480 and 574 nm owing to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 4f transitions of Dy3+ ions, respectively. The photometric properties confirm that the samples exhibit intense white emission with high color purity. Therefore, the prepared NPs could be a definitive choice as an advanced luminescent NPs for forensic, solid state lighting and portable FED devices. 相似文献
976.
Kaustubh Krishna Bawane Dheepa Srinivasan Dipankar Banerjee 《Metallurgical and Materials Transactions A》2018,49(9):3793-3811
Microstructures and tensile properties of Direct Metal Laser-Sintered (DMLS) CoCrMo were investigated in the as-printed condition and after heat treatment. A dense (>?99.5 pct) as-printed DMLS CoCrMo was obtained in the as-printed condition eliminating the need for any hot isostatic pressing. Solution heat treatment carried out at 1150 °C revealed complete recrystallization resulting in an equiaxed grain structure with an average grain size of 40 μm. The microstructure after solution heat treatment and aging at 980 °C revealed inter and intragranular precipitations, enriched in Mo and Si. Solution treatment resulted in the decrease of the room-temperature tensile strength from 1378 MPa (as-printed) to 1114 MPa, which was attributed to the increasing grain size from 0.6 to 1 μm (column width) to ~?40 μm (grain size). The decrease in yield strength was accompanied by the increasing ductility from 5.7 to 15 pct. An enhancement in ductility to nearly 25 pct was observed in tensile tests at 925 °C. This paper comprises a detailed microstructural evaluation of DMLS CoCrMo alloy to determine its suitability for high-temperature structural applications involving repair and refurbishment of components, including an evaluation of microstructural and tensile properties after welding the DMLS CoCrMo to cast FSX414. 相似文献
977.
K. Nagendra Prasad Bao Yang Xinhong Dong Guoxiang Jiang Haiyan Zhang Haihui Xie Yueming Jiang 《Innovative Food Science and Emerging Technologies》2009,10(4):627-632
Cinnamomum has long been regarded as a food or medicinal plant. Leaves of five species of Cinnamomum, namely C. burmanni, C. cassia, C. pauciflorum, C. tamala and C. zeylanica, were chosen to investigate their antioxidant activities in this study. C. zeylanica exhibited the highest total phenolic content while C. burmanni had the highest flavonoid content among the five species. These five species were then screened for their antioxidant potentials using various in-vitro models such as total antioxidant capability, 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, reducing power and superoxide anion scavenging activity at various concentrations. C. zeylanica showed the highest DPPH radical scavenging activity, total antioxidant activity and reducing power, while C. tamala exhibited the highest superoxide anion scavenging activity. By the analysis of the high performance liquid chromatography coupled to diode array detector (HPLC-DAD), three flavonoid compounds namely quercetin, kaempferol and quercetrin were identified and quantified. This study suggested that Cinnamomum leaf can be used potentially as a readily accessible source of natural antioxidants.
Industrial relevance
This study was focused to evaluate the antioxidant activities of five species of Cinnamomum leaf which is normally used in medicine and also used in food preparation. This study provided an alternative of utilizing Cinnamomum leaf as a readily accessible source of natural antioxidants in food and pharmaceutical industry. 相似文献978.
Poudel-Tandukar K Nakahara S Ichikawa M Poudel KC Wakai S 《Accident; analysis and prevention》2006,38(6):1058-1063
This study assessed the relationship between pedestrian activity at the time of injury, the type of vehicle involved and resulting activity limitation among school adolescents in the Kathmandu and Lalitpur districts of Nepal. A cross-sectional study of 1557 students in grades 6–8 across 14 schools was conducted using a self-administered questionnaire from August to September 2003. Twenty-three percent of adolescents reported pedestrian injuries, 38% were from urban and 21% from semi-urban areas. Adolescents were commonly injured by motorcycles and motor vehicles while crossing the road; however, while walking and playing, they were commonly injured by bicycles and motorcycles. Bicycles and motor vehicles were less likely to be involved in injury while crossing the roads and playing, respectively (p < 0.001). Activity was more likely to be limited for a longer period of time (>7 days) with injuries endured while crossing the road (p < 0.001). In urban areas, boys and girls were more likely to be injured while crossing the road and walking, respectively (p < 0.05), and both were commonly injured by motorcycles. In semi-urban areas, boys and girls were commonly injured while walking and were more likely to be injured by motorcycles and bicycles, respectively (p < 0.05). In both areas, more boys than girls were injured while playing. These findings have important implications for pedestrian safety interventions in poor countries. 相似文献
979.
Tarun Kumar Khurana B.V.S.S.S. Prasad K. Ramamurthi S. Srinivasa Murthy 《International Journal of Hydrogen Energy》2006,31(15):2299-2309
A significant decrease in the degree of thermal stratification is demonstrated by improvising transverse wall ribs on the inner cylindrical surfaces of large liquid hydrogen storage tanks. The ribbed surfaces are modeled as fins and a conjugate transient heat transfer problem is formulated for predicting flow currents and heat transfer. Turbulent Rayleigh numbers between 1.2×1012 and 6×1016 are considered. A stratification parameter based on the moment of energy is defined to quantify the degree of stratification and this parameter is seen to be about 30% lower for the ribbed tanks. The degree of stratification is not sensitive to changes in the ratio of the rib height to the spacing between the ribs. The transient free convection is shown to be characterized by the parameter Fo×Ra0.15. The process of stratification takes place more slowly in the ribbed tanks than in smooth-walled tanks. The free convective heat transfer coefficient for tanks having ribbed surface is also seen to be significantly lower. Incorporation of ribs over the inner surface of the insulated tanks is demonstrated to offer a simple means of reducing the stratification and boil-off losses. 相似文献
980.
Shi W Zeng H Sahoo Y Ohulchanskyy TY Ding Y Wang ZL Swihart M Prasad PN 《Nano letters》2006,6(4):875-881
We describe and demonstrate a general strategy for engineering binary and ternary hybrid nanoparticles based on spontaneous epitaxial nucleation and growth of a second and third component onto seed nanoparticles in high-temperature organic solutions. Multifunctional hybrid nanoparticles that combine magnetic, plasmonic, and semiconducting properties and that are tunable in size and morphology can be realized, as demonstrated for combinations of Au, Fe3O4 and PbS or PbSe. The properties of each component within the hybrids can be modulated strongly by the conjugating component(s) aided by the coherent interfaces between them. 相似文献