全文获取类型
收费全文 | 2177篇 |
免费 | 118篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 471篇 |
金属工艺 | 83篇 |
机械仪表 | 63篇 |
建筑科学 | 47篇 |
能源动力 | 69篇 |
轻工业 | 103篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 395篇 |
一般工业技术 | 454篇 |
冶金工业 | 228篇 |
原子能技术 | 28篇 |
自动化技术 | 322篇 |
出版年
2023年 | 7篇 |
2022年 | 22篇 |
2021年 | 21篇 |
2020年 | 26篇 |
2019年 | 25篇 |
2018年 | 48篇 |
2017年 | 46篇 |
2016年 | 46篇 |
2015年 | 51篇 |
2014年 | 70篇 |
2013年 | 184篇 |
2012年 | 103篇 |
2011年 | 135篇 |
2010年 | 119篇 |
2009年 | 120篇 |
2008年 | 129篇 |
2007年 | 111篇 |
2006年 | 77篇 |
2005年 | 68篇 |
2004年 | 62篇 |
2003年 | 71篇 |
2002年 | 49篇 |
2001年 | 46篇 |
2000年 | 55篇 |
1999年 | 69篇 |
1998年 | 102篇 |
1997年 | 52篇 |
1996年 | 45篇 |
1995年 | 43篇 |
1994年 | 37篇 |
1993年 | 30篇 |
1992年 | 18篇 |
1991年 | 24篇 |
1990年 | 13篇 |
1989年 | 26篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 6篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有2307条查询结果,搜索用时 15 毫秒
61.
Chao-Chi Shih Chih-Chieh Chen Chih-Chung Chang Sih-Li Chen 《International Communications in Heat and Mass Transfer》2012
This article experimentally develops a dynamic test strategy for efficiently diagnosing a heat pipe cooling module in order to improve the time-consuming conventional steady-state test. The first step is to investigate the performance of a heat pipe by measuring its thermal resistance, and the next step is to examine the influence of the parameters on the temperature response of the heat pipe cooling module. The experimental parameters include the press force, preheating temperature, heating power, and starting time of the fan. The results show that the thermal performance of a heat pipe, the contact condition between the heat pipe and the base plate, and the heat dissipation ability of a heat sink, are diagnosed within 30 seconds. During the dynamic test, both the startup and the ability to reach uniformity of temperature of the heat pipe can be observed. In addition, the temperature response of a heat pipe cooling module based on a lumped model matches the experimental data. 相似文献
62.
W.H. Hsieh J.Y. Wu W.H. Shih W.C. Chiu 《International Journal of Heat and Mass Transfer》2004,47(23):5149-5157
The demand of high speed and miniaturization of electronic components results in increased power dissipation requirement for thermal management. In this work, the effects of porosity (ε), pore density (PPI) and air velocity on the heat-transfer characteristics of aluminum-foam heat sinks are investigated experimentally. The phenomenon of non-local thermal equilibrium (NLTE) is also observed and reported. Results show that the Nu increases as the pore density increases, due to the fact that aluminum foam with a larger pore density has a larger heat-transfer area. The Nusselt number also increases with the increase of porosity due to the same reason. It is noted that temperatures of the solid and gas phases of the aluminum foam decrease as Reynolds number increases, caused by the increased convective heat-transfer rate at higher Reynolds number. The deduced temperature difference between the solid and gas phases clearly indicates the existence of non-local thermal equilibrium condition within the aluminum-foam heat sink. The increase of the porosity and the pore density enhances the phenomenon of non-local thermal equilibrium. The temperature difference increases with the decrease of Reynolds number and the distance away from the heat source. 相似文献
63.
Chao-Fang Shih Bhuvana Krishnaswamy Yubing Jian Raghupathy Sivakumar 《Wireless Networks》2018,24(1):89-112
The ubiquitous adoption of WiFi introduces large diversity in types of application requirements and topological characteristics. Consequently, considerable attention is being devoted to making WiFi networks controllable without compromising their scalability. However, the main MAC protocol of WiFi, distributed coordination function (DCF), is a contention-based protocol using random backoff. Thus, operating under DCF, the access of channel is hard to control and nonpredictable. In order to provide controllability of channel access in WiFi, we propose Rhythm, a MAC protocol that achieves scheduled WiFi efficiently using distributed contention. By achieving scheduled WiFi, channel access can be controlled by manipulating the schedule decision. We evaluate the performance of Rhythm through analysis, experiments, and case-studies. 相似文献
64.
Shih Yeh Lim Mohd Sokhini Abdul Mutalib Sui Kiat Chang 《International Journal of Food Properties》2018,21(1):2428-2451
There is a growing concern over the food safety issue related to increased incidence of cooking oil adulteration with recycled cooking oil (RCO). The objective of this study was to detect fresh palm olein (FPO) adulteration with RCO using fatty acid composition (FAC) and Fourier-transform infrared spectroscopy (FTIR) spectral analyses combined with chemometrics. RCO prepared in the laboratory was mixed with FPO in the proportion ranged from 1% to 50% (v/v) to obtain the adulterated oil samples (AO). FACs for FPO, RCO, and AO were determined using gas chromatography equipped with a flame ionization detector (GC-FID). The compositions of most fatty acids in RCO lied within the normal ranges of Codex standard, except for C8:0, C10:0, C11:0, C15:0, trans C18:1, and polyunsaturated fatty acids (PUFAs), C20:5. PUFAs showed a consistent decreasing trend with increasing magnitude of change with respect to increasing adulteration level and thus might be a good indicator for detecting FPO adulteration with RCO. The evaluation parameters (coefficient of determination, root mean standard error) of the FTIR-partial least square (PLS) model of palm oil adulteration with recycled oil are R2 = 0.995 and 3.25, respectively. For FTIR spectral analysis, the distinct variations in spectral regions and aberrations in characteristic bands between FPO and RCO were observed. The optimized PLS calibration model developed from normal spectral of the combined region at 3602–3398, 3016–2642, and 1845–650 cm?1 overpredict the adulteration level. On the other hand, the discriminant analysis classification model was able to classify the FPO and AO into two distinct groups. Improvement of the principles of combined techniques in authenticating AO from fresh oil is beneficial as a guideline to detect adulteration in cooking oil. 相似文献
65.
Bharat Joshi Huai-Ren Shih Brian Rose 《Journal of Failure Analysis and Prevention》2018,18(3):486-495
Diffuser plates in exhaust system manifolds are designed to provide uniform flow pattern within the manifold for maximum utilization of the catalytic converter substrate during high-temperature applications. In this paper, failure analysis of a diffuser which survived only 20% duration of a manifold crack test and various design optimization studies of the diffuser plate using computer-aided engineering (CAE) analyses are presented. During the manifold crack test, the failure occurred at the inner and outer periphery of the diffuser. Metallurgical failure analysis coupled with CAE thermal fatigue analysis of the component concluded that thermal fatigue was the root cause of the failure. The new recommended robust design showed considerable improvement in the thermal durability of the diffuser plate assembly. 相似文献
66.
Microsystem Technologies - Brushless dc (BLDC) motor provides many advantages such as less power consumption, small volume, good stability, larger torque and simple control. As a result, the... 相似文献
67.
A low temperature process of mixing different sizes of silicon carbide (SiC) particles with a polymer precursor was utilized to synthesize SiC pellets for potential use as inert matrix fuels (IMF) for light water reactors. The lower temperature process is required to prevent the reactions between SiC and the dispersed PuO2 fuel material. The effect of the polymer content and the cold pressing pressure on the packing of SiC particles was investigated. The effect of mixing coarse and fine SiC particles on the density and the pore size distribution was also investigated. It was found that the density and pore size distribution can be tailored by controlling the SiC size compositions, polymer content and pressing pressure at room temperature. A possible mechanism has been proposed to explain the forming of the pores with respect to the geometric arrangement between SiC particles and the polymer precursor. SEM images showed that ceria (cerium oxide) which is a PuO2 surrogate in this study, was well distributed in the pellet. 相似文献
68.
Yun-Ying Chen Yi-Chieh Chang Wei-Ying Hung Hong-Ping Lin Hui-Ya Shih Wen-An Xie Shou-Nan Li Chun-Han Hsu 《国际能源研究杂志》2020,44(12):9748-9756
A simple synthetic method without organic template is proposed for the synthesis of Ni-silicate. The resulting Ni-phyllosilicates are reconstructed by hydrothermal treatment to a porous structure with a high surface area (552 m2 g−1). Notably, the residual filtrate has a Ni2+ ion content of less than 0.1 ppm, and therefore satisfies the effluent standard in Taiwan (<1.0 ppm). As a result, it can be disposed of directly without the need for additional treatment. The effects of the pH value and hydrothermal treatment time on the structure, morphology, and surface area of the Ni-silicate composites have been investigated. When applied to hydrogen production, the mesoporous Ni-silicate shows a high catalytic capability (>99%) toward ammonia decomposition at a temperature of 400°C. Overall, the proposed synthetic method is facile and easily extendable to the production of other metal-silicate materials for hydrogen generation. 相似文献
69.
Tsai Pei-Wei Li Jian-Pan Shih Jia-Shing Chen Yin-Jun Lee Tung-ying Cheng Sheng-Tzong 《Telecommunication Systems》2020,75(2):221-234
Telecommunication Systems - Vehicle-to-vehicle communication and probabilistic broadcast are important means for information dissemination in vehicular ad-hoc networks (VANETs). In contrast to... 相似文献