全文获取类型
收费全文 | 367篇 |
免费 | 18篇 |
国内免费 | 6篇 |
学科分类
工业技术 | 391篇 |
出版年
2024年 | 4篇 |
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 28篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 17篇 |
2014年 | 25篇 |
2013年 | 35篇 |
2012年 | 12篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 18篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有391条查询结果,搜索用时 31 毫秒
21.
The use of (CPB) material to ameliorate geotechnical stability of underground mine is in nascent stage in India. Rheological properties of CPB change with travelling time as it is transported to underground mine stope through pipeline reticulation. In this paper, rheological properties of CPB based on mill tailings of a carbonate rich mineral processing waste are evaluated for different dosages of polycarboxylate (PC) based (SP). Each CPB sample having 78?wt% solids is mixed separately with 4%, 6% or 8% of binder dosages (ratio of the weight of dry binder to the weight of dry tailings) and, 0%, 0.5%, or 1.0% of SP dosages as weight of dry binder. The paper presents a methodology for determining yield stress, plastic viscosity and thixotropic behaviour of CPB mixture as a function of hydration age, binder and SP dosages. Results from the experimental campaigns indicate that SP content has significant influence on rheological behaviour of CPB and can be suitably exploited to enhance the flow characteristics of the carbonate rich process tailings. The study also develops multivariate linear regression models of yield stress, plastic viscosity and thixotropy of CPB depending on the hydration age, binder and SP dosages. 相似文献
22.
Fabrication and Circuit Modeling of NMOS Inverter Based
on Quantum Dot Gate Field-Effect Transistors
Supriya Karmakar John A. Chandy Mukesh Gogna Faquir C. Jain 《Journal of Electronic Materials》2012,41(8):2184-2192
This paper presents the fabrication of a negative-channel metal–oxide–semiconductor (NMOS) inverter based on quantum dot gate field-effect transistors (QDG-FETs). A QDG-FET produces one intermediate state in its transfer characteristic. NMOS inverters based on a QDG-FET produce three states in their transfer characteristic. The generation of the third state in the inverter characteristic makes this a promising circuit element for multivalued logic implementation. A circuit simulation result based on the Berkley simulation (BSIM) circuit model of the QDG-FET is also presented in this paper, predicting the fabricated device characteristic. 相似文献
23.
Debasis Das Adhikary Goutam Kumar Bose Dipak Kumar Jana Dipankar Bose Souren Mitra 《Quality Engineering》2016,28(3):352-357
This article presents a multi-objective (maximization of availability and minimization of maintenance cost) preventive maintenance (PM) scheduling model for a continuous operating series system (COSS) which do not provide an off-working period for PM. The objective functions are optimized by using a Multi-Objective Genetic Algorithm (MOGA). The effectiveness of the model is demonstrated through a coal-fired boiler-tube. The case study shows that the model can improve the availability along with profound reduction of the maintenance cost, i.e., increases the profit of the plant. 相似文献
24.
Suchetana Chakraborty Sandip Chakraborty Sukumar Nandi Sushanta Karmakar 《International Journal of Wireless Information Networks》2014,21(4):262-279
The lifetime of a sensor network is influenced by the efficient utilization of the resource constrained sensor nodes. The tree-based data gathering offers good quality of service (QoS) for the running applications. However, data gathering at the sink reduces the network lifetime due to a fast failure of highly loaded nodes. Loss of connectivity and sensing coverage affect the performance of the applications that demand critical QoS. In this paper, a data gathering tree management scheme has been proposed to deal with arbitrary node failures in delay-sensitive sensor networks. A load-balanced distributed BFS tree construction procedure has been introduced for an efficient data gathering. Based on the initial tree construction, a tree maintenance scheme and an application message handler have been designed to ensure the reliable delivery of the application messages. The correctness of the proposed scheme has been verified both theoretically and with the help of simulation. The proposed scheme offers low overhead, enhanced network lifetime and good QoS in terms of delay and reliability of the application messages. 相似文献
25.
26.
Upender Gangadharini Atiar Rahaman Molla Anal Tarafder Basudeb Karmakar 《Journal of the American Ceramic Society》2013,96(7):2155-2162
The glass–ceramics containing a rarely achievable nanocrystalline SrIINbIVO3 phase in the 53.75SiO2–18.25K2O–9Bi2O3–9SrO–9Nb2O5–0.5CeO2–0.5Eu2O3 (mol%) glass system were prepared by the melt‐quench technique followed by a two‐stage controlled heat treatment. The unusual oxidation state of Nb in SrIINbIVO3 crystal is 4+ and upon heat treatment of the samples at lower temperature of 500°C for several hours, the glass composition and chemical environment around Nb ions played a key role for the formation of SrIINbIVO3 in the glass–ceramics. The microstructure of the glass–ceramics was studied using TEM and FESEM. The TEM images advocate 10–40 nm crystallite size of SrIINbIVO3. FTIR study confirms that all the samples consist of SiO4, BiO3, BiO6, and NbO6 structural units. The refractive index at different wavelengths was found to vary in the range 1.7105–1.7905 and increase with increase in heat‐treatment time. The luminescence spectra of Eu3+‐doped glass and glass–ceramics were recorded at 465 nm excitation wavelength and the luminescence intensity is found to be increased with heat‐treatment time due to increase in crystallinity. The high intensity ratio of 5D0→7F2 to 5D0→7F1 indicates that the Eu3+‐doped nanocrystalline SrIINbIVO3 glass–ceramics are promising candidate materials as red‐light source. 相似文献
27.
Anal Tarafder Atiar Rahaman Molla Chirantan Dey Basudeb Karmakar 《Journal of the American Ceramic Society》2013,96(8):2424-2431
The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt‐quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–ceramic nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat‐treatment time was examined by X‐ray diffraction (XRD) and field‐emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat‐treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass‐ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–ceramic nanocomposites is enhanced up to 17‐fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–ceramic nanocomposites are expected to find potential applications in solid‐state red lasers, phosphors, and optical display systems. 相似文献
28.
Tapatee Kundu Roy Abhijit Ghosh Debasis Bhowmick Dirtha Sanyal Soumyajit Koley Alok Chakrabarti 《Ceramics International》2011,37(7):2679-2687
The ability of silica (SiO2) in controlling the densification and grain growth behavior of nano crystalline zinc oxide (ZnO) has been systematically studied. It has been observed that SiO2 acts as a sintering inhibitor in the ZnO–SiO2 system up to 4 wt.% limiting value beyond which densification behavior of the system remains almost unchanged, especially above 1100 °C. The addition of SiO2 to ZnO retards grain growth which in turn results a finer ultimate grain size as compared to the undoped ZnO. However, stabilization in grain size occurs at ≥4 wt.% SiO2 addition. It has been observed that SiO2 incorporation changes the grain growth mechanism up to 4 wt.% addition, beyond which no remarkable changes was noticed. The grain growth (n) shows distinctly different slopes as a function of sintering time for the SiO2 doped ZnO systems than undoped ZnO. The different slopes tend to indicate that different diffusion mechanisms and probably the formation of a secondary phase (Zn–Si–O) at the grain boundary control the densification and grain growth. The thermal expansion coefficient of the system has been found to decrease substantially beyond 4 wt.% SiO2 addition to ZnO. 相似文献
29.
Biplab Kumar Paul Dheeraj Mondal Solanky Das Debasis Roy Papiya Nandy Sukhen Das 《Journal of Electronic Materials》2018,47(12):7075-7084
In this communication, the formation mechanism of the electroactive β phase, morphology and the dielectric activities of increasing doping concentration (0–1.2 M.W % of mullite) of Fe2+ ion-doped, mullite-impregnated polyvinylidene fluoride (PVDF) nanocomposite have been investigated. Differential thermal analysis (DTA) confirms the formation of an electroactive β phase, and Fourier transform infrared spectroscopy (FTIR) showed that the β phase increases simultaneously and attains the maximum increment of 2.6 times compared to pristine PVDF. X-ray diffraction (XRD) spectra also agreed well with the β-phase increment behaviour and also confirmed the presence of required mullite phases. Field emission scanning electron microscopy (FESEM) images indicate the strong interaction between the polymer matrix and different concentrations of Fe2+ ion-doped mullite particles, resulting in enhanced electroactive β phase formation and large dielectric constant of the nanocomposite films followed by significant low dielectric loss with high ac conductivity compared to pristine PVDF films at room temperature. This doped polymer composite can be used as a high dielectric separator and, using this separator, we have successfully fabricated a high-charge-storage device. This paper also demonstrates that the loading of conductive Fe2+ ions within the highly insulating mullite matrix has a critical concentration for the enhancement and nucleation of the electroactive β phase of the PVDF polymer. In this critical concentration, the highest formation of a β network and maximum numbers of homogeneously distributed iron-doped mullite (FeM) particles in PVDF matrix improves the effective interfacial polarization by Maxwell–Wagner–Sillar (MWS) polarization effect which is responsible for the enhancement of dielectric constant and ac conductivity followed by significant tangent loss. So, it can be concluded that the incorporation of Fe2+-doped mullite into PVDF matrix is an effective way to fabricate a high dielectric separator of high-charge-storage electronic devices. 相似文献
30.