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排序方式: 共有307条查询结果,搜索用时 31 毫秒
61.
Point‐of‐Care Diagnostics: Host Cell Mimic Polymersomes for Rapid Detection of Highly Pathogenic Influenza Virus via a Viral Fusion and Cell Entry Mechanism (Adv. Funct. Mater. 34/2018) 下载免费PDF全文
62.
Young?-Sang?NaEmail author Jong?-Taek?Yeom Nho?-Kwang?Park Jai?-Young?Lee 《Metals and Materials International》2003,9(1):15-19
The mechanical properties of the Ni−Fe-based Alloy 718 depend very much on grain size, as well as the strengthening phases,
γ’ and γ. The grain structure of the superalloy components is mainly controlled during thermo-mechanical processes by the
dynamic, meta-dynamic recrystallization and grain growth. In this investigation, the evolution of the grain structure in the
process of two-step blade forging was experimentally and numerically dealt with. The evolution of the grain structure in Alloy
718 during blade forging was predicted using a 2-DFE simulator with implemented constitutive models on dynamic recrystallization
and grain growth. The comparison of the simulated microstructure with the actual grain structure of the forged parts validated
the prediction of the grain structure evolution. The effect of dynamic recrystallization on the evolution of grain structure
is highlighted in this article. 相似文献
63.
Solution Shearing: Inorganic Polymer Micropillar‐Based Solution Shearing of Large‐Area Organic Semiconductor Thin Films with Pillar‐Size‐Dependent Crystal Size (Adv. Mater. 29/2018) 下载免费PDF全文
64.
High‐Performance 2D Rhenium Disulfide (ReS2) Transistors and Photodetectors by Oxygen Plasma Treatment 下载免费PDF全文
65.
Thin‐Film Transistors: High‐Performance 2D Rhenium Disulfide (ReS2) Transistors and Photodetectors by Oxygen Plasma Treatment (Adv. Mater. 32/2016) 下载免费PDF全文
66.
Homogeneous charge compression ignition of LPG and gasoline using variable valve timing in an engine
Kitae Yeom 《Fuel》2007,86(4):494-503
The combustion characteristics and exhaust emissions in an engine were investigated under homogeneous charge compression ignition (HCCI) operation fueled with liquefied petroleum gas (LPG) and gasoline with regard to variable valve timing (VVT) and the addition of di-methyl ether (DME). LPG is a low carbon, high octane number fuel. These two features lead to lower carbon dioxide (CO2) emission and later combustion in an LPG HCCI engine as compared to a gasoline HCCI engine. To investigate the advantages and disadvantages of the LPG HCCI engine, experimental results for the LPG HCCI engine are compared with those for the gasoline HCCI engine. LPG was injected at an intake port as the main fuel in a liquid phase using a liquefied injection system, while a small amount of DME was also injected directly into the cylinder during the intake stroke as an ignition promoter. Different intake valve timings and fuel injection amount were tested in order to identify their effects on exhaust emissions and combustion characteristics. Combustion pressure, heat release rate, and indicated mean effective pressure (IMEP) were investigated to characterize the combustion performance. The optimal intake valve open (IVO) timing for the maximum IMEP was retarded as the λTOTAL was decreased. The start of combustion was affected by the IVO timing and the mixture strength (λTOTAL) due to the volumetric efficiency and latent heat of vaporization. At rich operating conditions, the θ90-20 of the LPG HCCI engine was longer than that of the gasoline HCCI engine. Hydrocarbon (HC) and carbon monoxide (CO) emissions were increased as the IVO timing was retarded. However, CO2 was decreased as the IVO timing was retarded. CO2 emission of the LPG HCCI engine was lower than that of the gasoline HCCI engine. However, CO and HC emissions of the LPG HCCI engine were higher than those of the gasoline HCCI engine. 相似文献
67.
With the explosion of multimedia content, Internet bandwidth is wasted by repeated downloads of popular content. Recently, Content-Centric Networking (CCN), or the so-called Information-Centric Networking (ICN), has been proposed for efficient content delivery. In this paper, we investigate the performance of in-network caching for Named Data Networking (NDN), which is a promising CCN proposal. First, we examine the inefficiency of LRU (Least Recently Used) which is a basic cache replacement policy in NDN. Then we formulate the optimal content assignment for two in-network caching policies. One is Single-Path Caching, which allows a request to be served from routers only along the path between a requester and a content source. The other is Network-Wide Caching, which enables a request to be served from any router holding the requested content in a network. For both policies, we use a Mixed Integer Program to optimize the content assignment models by considering the link cost, cache size, and content popularity. We also consider the impact of link capacity and routing issues on the optimal content assignment. Our evaluation and analysis present the performance bounds of in-network caching on NDN in terms of the practical constraints, such as the link cost, link capacity, and cache size. 相似文献
68.
Myung-Jun?LeeEmail author Jong-Youl?Kim Jong-Sang?Park Jeong-Kuk?Yeom Sung-Sik?Chung 《Journal of Mechanical Science and Technology》2004,18(9):1623-1629
The objective of this study is the rapid bulk combustion of mixture in a constant volume chamber with a tiny sub-chamber.
Some narrow passage holes were arranged to induce simultaneous multi-point ignition in the main chamber by jet of burned and
unburned gases including radicals from the sub-chamber, and the equivalence ratios of pre-mixture in the main chamber and
the sub-chamber were the same. The principal factors of the Radical Induced Auto-Ignition (RIAl) method are the diameter of
the passage holes and the volume of sub-chamber. The relationship between the sub-chamber and diameter of passage hole was
represented by the ratios of sub-chamber volume to passage hole volume. The ratios are non-dimensional coefficients for sub-chamber
characteristics. As a result, the RIAI method reduced the combustion period, which expanded the lean limit in comparison with
SI method. 相似文献
69.
Jeongkuk Yeom Jongsang Park Sungsik Chung 《Journal of Mechanical Science and Technology》2005,19(12):2281-2288
Because an injected spray development process consists of impinging and free spray in the diesel engine, it is needed to analyze
the impinging spray and free spray, simultaneously, in order to study the diesel spray behavior. To dominate combustion characteristics
in diesel engine is interaction between injected fuel and ambient gas, that is, process of mixture formation. Also it is very
important to analyze liquid and vapor phases of injected fuel on the investigation of mixing process, respectively and simultaneously.
Therefore, in this study, the behavior characteristics of the liquid phase and the vapor phase of diesel spray was studied
by using exciplex fluorescence method in high temperature and injection pressure field. Finally, it can be confirmed that
the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection
pressure. 相似文献
70.
Jeongkuk Yeom Jongsang Park Sipom Kim Jongyul Ha Sungsik Chung Joongsoon Lee 《Journal of Mechanical Science and Technology》2007,21(7):1120-1128
The purpose of this study was to analyze the structure and to clarify the mixture formation process within evaporative diesel
spray. Liquid fuel was injected from a single-hole nozzle (l/d=1.0mm/0.2mm) into a constant-volume vessel under high pressure
and temperature in order to visualize the spray phenomena. An exciplex fluorescence method was applied to the evaporative
fuel spray to measure and investigate both the liquid and the vapor phase of the injected spray. The region of interest in
this experiment was downstream towards the end of the spray. For accurate investigation, images of the liquid and vapor phase
regions were recorded with a 35mm still camera and CCD camera, respectively. For the case of the evaporative fuel spray, the
images showed that within the region of liquid phase very small droplets could be found outside of the spray and larger droplets
at the spray’s tip. This can be explained through the droplet classification defined byStokes number (stk) (Chung et al., 1990). From the 2-dimensional analysis results of the heterogeneous distribution of the inner spray, a 3-dimensional
analysis was attempted by using the offset incidence of the laser beam from the spray’s center axis. Finally, in order to
quantify the mixture’s state change within the vapor phase region of the injected spray, images analysis were carried out
based on the entropy of statistical thermodynamics. 相似文献