全文获取类型
收费全文 | 3169篇 |
免费 | 171篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 83篇 |
综合类 | 10篇 |
化学工业 | 618篇 |
金属工艺 | 30篇 |
机械仪表 | 88篇 |
建筑科学 | 87篇 |
矿业工程 | 12篇 |
能源动力 | 91篇 |
轻工业 | 196篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
武器工业 | 3篇 |
无线电 | 608篇 |
一般工业技术 | 626篇 |
冶金工业 | 319篇 |
原子能技术 | 25篇 |
自动化技术 | 543篇 |
出版年
2024年 | 4篇 |
2023年 | 15篇 |
2022年 | 43篇 |
2021年 | 79篇 |
2020年 | 56篇 |
2019年 | 45篇 |
2018年 | 62篇 |
2017年 | 72篇 |
2016年 | 81篇 |
2015年 | 76篇 |
2014年 | 92篇 |
2013年 | 203篇 |
2012年 | 160篇 |
2011年 | 194篇 |
2010年 | 162篇 |
2009年 | 200篇 |
2008年 | 181篇 |
2007年 | 175篇 |
2006年 | 107篇 |
2005年 | 110篇 |
2004年 | 109篇 |
2003年 | 88篇 |
2002年 | 78篇 |
2001年 | 71篇 |
2000年 | 60篇 |
1999年 | 66篇 |
1998年 | 125篇 |
1997年 | 106篇 |
1996年 | 70篇 |
1995年 | 60篇 |
1994年 | 43篇 |
1993年 | 42篇 |
1992年 | 31篇 |
1991年 | 32篇 |
1990年 | 40篇 |
1989年 | 27篇 |
1988年 | 39篇 |
1987年 | 25篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有3357条查询结果,搜索用时 15 毫秒
51.
The effect of hygrothermal aging on a particle‐filled, epoxy‐based adhesive was studied using a gravimetric sorption technique. This study has explored moisture sorption characteristics as well as the associated behaviors of swelling and the depression of the glass transition temperature (Tg). We observed that the diffusion of water in this adhesive has a non‐Fickian behavior, and the depression of Tg proceeds to a definite value that is independent of the final equilibrium water content of the system. Our observations suggest that water diffuses into the polymer in a dual‐sorption mode, in which water resides in two populations. In one population, water is considered to occupy apparent free volume of the adhesive, and the second population water infiltrates polymer structure and forms hydrogen‐bonded clusters. Our results show that hygrothermal aging temperature and swelling do not alter the apparent free volume of this adhesive. We conclude that the constant value of Tg depression at saturation implies that only water in the apparent free volume is responsible for the Tg depression, whereas the swelling proceeds through the formation of hydrogen bonds in the adhesive. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1436–1444, 2003 相似文献
52.
To help make a good polymer blend by melt blending, the properties of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) systems with various compositions have been investigated. As ABS is blended into PC to form a binary system, Brabender torque is reduced, a phenomenon that results in Improved processability of PC. With increasing ABS content, the mechanical properties of the blends such as tensile strength, modulus, hardness, and shrinkage decrease. However, with the variation of composition, Izod impact strength shows a maximum, while elongation at break exhibits a minimum. These phenomena are discussed with dynamic viscoelasticities and scanning electron microscopic morphological results. The value of ΔTg(TgβPC ? TgβABS) is at its smallest when the ratio of PC to ABS is 90:10, However, the value rises with an increase in ABS because the butadiene content of the ABS hinders compatibility in the binary system. At the 90:10 composition, the damping height is optimal. In addition, the dispersed phase of the ABS is most ideal, absorbing the impact force and showing high impact strength. Composition ratios other than 90:10 present high damping as well as undesirable phase separation because of poor adhesion between two phases. As a result, the mechanical properties are reduced. 相似文献
53.
Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system 总被引:1,自引:0,他引:1
Nano-titania (TiO2) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO2 hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N2 and Ar/O2) were also applied in this study to improve the adhesion strength. The Ar/N2 plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO2-1 wt% hybrid film with Ar/N2 plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O2 plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO2 hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO2 on the adhesion strength between PI/TiO2 hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO2 hybrid film and copper was proposed in this study. 相似文献
54.
A new kind of terpolymer membrane was employed to separate a permselective water–alcohol mixture. This membrane was prepared via the copolymerization of acrylonitrile, sodium salt styrene sulfonic acid (SStSA), and hydroxyethyl methacrylate in dimethylsulfoxide with azobisisobutyronitrile as an initiator. The reaction mechanism, resultant structure, and polymer composition were confirmed by IR and elemental analysis. The effects of the feed composition on the polymer composition, mechanical properties, thermal properties, and degree of swelling were investigated. It was found that water permeated through the membrane preferentially in a water/alcohol system. The flux increased with the increase of SStSA, but the separation factor decreased drastically with higher SStSA. For a 50 wt % water–ethanol mixture, a flux of 0.65 kg/m2 h and a separation factor of 212 were obtained at 30°C when the membrane containing the highest SStSA content was used. The capacities of the metal ions absorbed by the membranes were investigated in the study. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 244–250, 2003 相似文献
55.
Khaksar Pour Amin Chaw Seng Woo Palaiahnakote Shivakumara Tahaei Hamid Anuar Nor Badrul 《Multimedia Tools and Applications》2021,80(16):24121-24145
Multimedia Tools and Applications - Rating a video based on its content is one of the most important solutions to classify videos for audience age groups. In this regard, Film content rating and TV... 相似文献
56.
Shi Xiaoying Lv Fanshun Seng Dewen Zhang Jiaming Chen Jing Xing Baixi 《Multimedia Tools and Applications》2021,80(6):8355-8375
Multimedia Tools and Applications - The graph convolutional network (GCN), which can handle graph-structured data, is enjoying great interest in recent years. However, while GCN achieved remarkable... 相似文献
57.
A microstrip‐fed conventional annular ring slot (ARS) antenna with linear polarization (LP) is initially studied. To generate two orthogonal degenerate modes for circular polarization (CP) radiations, two identical meandering perturbation slots (MPS) are symmetrically loaded into the ARS. By further incorporating a PIN diode switch across each MPS, the proposed antenna can switch between left‐hand CP (LHCP), right‐hand CP (RHCP), and LP. All three polarizations have shown good impedance bandwidth and broad CP bandwidth that can satisfy the wireless local area network (WLAN) 2.4‐GHz operating band (2400–2480 MHz). Furthermore, desirable gains of 1.8–2.0 dBi and 2.40–2.84 dBic are also exhibited at LP and LHCP/RHCP, respectively. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:110–120, 2016. 相似文献
58.
Hua-Pei Chiang Chin-Feng Lai Ying-Hsun Lai Yueh-Min Huang 《Multimedia Tools and Applications》2016,75(22):14125-14141
Motion sensing has now become one of the crucial parts of modern life. The tech products for entertainment create huge competition in the modern market, with the front runners such as game and handset manufacturers. Users can use their own bodies to control the systems without Conversational User Interfaces (CUIs) and Graph User Interfaces (GUIs). With many benefits, the technologies of NUI is getting more and more important, which also are usually accompanied by the sensor developments. Hence, system designers uses the sensors on the embedded platforms used to develop the system devices for different body movement control interfaces, such as using the gravitational sensor to control the systems or using touchscreen detection. However most of the body movement is restricted to the hand portion for the system platform, making it not as dynamic as the traditional monitor consoles. Thus, this restriction decreases the multitude and availability of controlling modes in system devices. In this study, a sensor-based gait recognition was proposed, in order to provide a novel natural user interface for control systems except the operating modes of gesture. 相似文献
59.
60.
Chun-Wei Tsai Shih-Pang Tseng Chu-Sing Yang Ming-Chao Chiang 《Applied Soft Computing》2013,13(6):3008-3020
This paper presents an effective and efficient method for speeding up ant colony optimization (ACO) in solving the codebook generation problem. The proposed method is inspired by the fact that many computations during the convergence process of ant-based algorithms are essentially redundant and thus can be eliminated to boost their convergence speed, especially for large and complex problems. To evaluate the performance of the proposed method, we compare it with several state-of-the-art metaheuristic algorithms. Our simulation results indicate that the proposed method can significantly reduce the computation time of ACO-based algorithms evaluated in this paper while at the same time providing results that match or outperform those ACO by itself can provide. 相似文献