全文获取类型
收费全文 | 1069篇 |
免费 | 55篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 205篇 |
金属工艺 | 14篇 |
机械仪表 | 38篇 |
建筑科学 | 21篇 |
矿业工程 | 2篇 |
能源动力 | 44篇 |
轻工业 | 103篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
无线电 | 210篇 |
一般工业技术 | 194篇 |
冶金工业 | 71篇 |
原子能技术 | 3篇 |
自动化技术 | 194篇 |
出版年
2024年 | 2篇 |
2023年 | 17篇 |
2022年 | 43篇 |
2021年 | 50篇 |
2020年 | 47篇 |
2019年 | 56篇 |
2018年 | 51篇 |
2017年 | 36篇 |
2016年 | 68篇 |
2015年 | 30篇 |
2014年 | 48篇 |
2013年 | 90篇 |
2012年 | 60篇 |
2011年 | 69篇 |
2010年 | 40篇 |
2009年 | 49篇 |
2008年 | 38篇 |
2007年 | 32篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 22篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有1128条查询结果,搜索用时 62 毫秒
1.
The effect of physical aging on the fracture behavior, crack opening displacement, and plastic deformation zone of unmodified and rubber-modified epoxies was determined at two aging temperatures and different displacement rates. The strain energy release rate decreases to between 40 and 50% (for rubber modified and unmodified samples, respectively) of the unaged values after 35 days aging. Systematic dependence of the decrease in fracture toughness by aging on the rubber content is not apparent. The increased yield stress after physical aging is the main factor contributing to the reduction in fracture toughness, crack opening displacement, and plastic deformation zone. Physical aging suppresses the crack blunting mechanisms in epoxies. 相似文献
2.
Sangmun Shin Nguyen Khoa Viet Truong Byung Rae Cho Sung Hoon Hong 《Computers & Industrial Engineering》2011
Robust design (RD) and tolerance design (TD) have received much attention from researchers and practitioners for more than two decades, and a number of methodologies for modeling and optimizing the RD and TD processes have been studied. However, there is ample room for improvement. Because most existing research considers RD and TD as separate research fields, the primary objective of this paper is to develop a sequential robust–tolerance design method to jointly determine the best factor settings and the closed-form solutions for the optimal specification limits. We then apply the proposed method to a destructive quality characteristic. Finally, a case study and sensitivity analyses are performed for verification purposes, and further studies are discussed. 相似文献
3.
Truong Khang Nguyen Thi Anh Ho Haewook Han Ikmo Park 《Journal of Infrared, Millimeter and Terahertz Waves》2012,33(11):1123-1137
This paper presents a numerical study of self-complementary antennas on substrate lenses made of high-permittivity dielectric material. Bowtie, logarithmically periodic, and logarithmic spiral antennas with the same outer and inner dimensions were selected for study, and their overall performances were compared in the terahertz band at frequencies up to 5.0?THz. The resonance and radiation characteristics of the three antennas were investigated in terms of input impedance, directivity, and radiation efficiency, using a full electromagnetic simulator. This study provides useful guidelines and partially solves the difficult problems of choosing the proper feed and optimizing the lens structure for a THz broadband integrated lens antenna. 相似文献
4.
Jaewoo Choi Nagarajan Balaji Vinh Ai Dao Cheolmin Park Seunghwan Lee Jungmo Kim Minkyu Ju Hoongjoo Lee Youn-Jung Lee Junsin Yi 《Journal of Electronic Materials》2014,43(9):3191-3195
The effect of hydrogen capping of SiN(Si-rich)/SiN(N-rich) stacks for n-type c-Si solar cells was investigated. Use of a passivation layer consisting of Si-rich SiN with a refractive index (n) of 2.7 and N-rich SiN with a refractive index of 2.1 improved the thermal stability. A single SiN passivation layer with a refractive index of 2.05 resulted in an initial lifetime of 200 μs whereas the layer with a refractive index of 2.7 resulted in a high initial lifetime of 2 ms, but the layer degraded rapidly after firing. A stacked passivation layer with refractive indices of 2.1 and 2.7 had a stable lifetime of 1.5 ms with an implied open-circuit voltage (iV oc) of 720 mV after firing. The thermally stable passivation mechanism with changing amounts of Si–N and Si–H bonding was analyzed by Fourier-transform infrared (FTIR) spectroscopy. Incorporation of the SiN x stack layer (2.7 + 2.1) into the passivated rear of n-type Cz silicon screen-printed solar cells resulted in energy conversion efficiency of 19.69%. Improved internal quantum efficiency in the long-wavelength range above 900 nm, with V oc of 630 mV, is mainly because of superior passivation of the rear surface compared with conventional solar cells. 相似文献
5.
Parallel manipulator is a closed-kinematic chain mechanism in which performance of its end effector – moving platform is contributed by its independent actuators. In traditional designs, each elemental actuator has its own controller as well as reference input, and it works independently without gathering information from its neighbors. Consequently, as one of the actuators cannot keep up with the others, the platform performance is easily deteriorated due to the lack of coherence between these actuators. Therefore, the aim of this paper is to design a 3-R planar parallel robot and develop a proper synchronization controller for its tracking control task. Adaptive Network Based Fuzzy Inference System (ANFIS) algorithm was modified and applied as the main strategy of this synchronization controller. The controller is then able to compensate errors between the actuators and enforce them to cooperate harmonically with each other regardless external disturbances caused by the outside environment or geometrical constraints of the closed-loop structure. Simulations and practical experiments on a scaled parallel robot were carried out to evaluate the designed controller. The results showed that by applying the proposed control technique, the working errors of the component actuators converged quickly to zero almost at the same time. As a result, the tracking performance of the common platform was significantly improved in comparison with the performance when applying a non-synchronization controller. The proposed method is effective in controlling systems which require collaborations between the sub-agents. 相似文献
6.
Phan Cong Vinh 《Mobile Networks and Applications》2014,19(2):227-234
Ubiquitous computing for information and service integration is currently at crucial point in its evolution, marked by the increasing developments of agent-based ubiquitous computing systems for the information and service integration. Some major features of ubiquitous computing systems (UCSs) consist of heterogeneity, decentralization, nondeterminism and dynamicity. Hence, agent-based ubiquitous computing (AUC) is a form of distributed computing by which computational processes are executed concurrently by assigning each computational process to one of agents on a UCS. The overarching goal of AUC is to support the seamless integration of information and services. Meeting this grand challenge of AUC requires that agent-orientation not tackled before is necessarily featured. To this end, taking advantage of the categorical structures we establish, in this paper, a firm formal development for featuring agent-orientation of ubiquitous computing. In other words, all of these are to formalize the AUC for information and service integration. 相似文献
7.
Ngoc Kim Pham Do Trung Nguyen Bang Tam Thi Dao Kieu Hanh Thi Ta Vinh Cao Tran Van Hieu Nguyen Sang Sub Kim Shinya Maenosono Thang Bach Phan 《Journal of Electronic Materials》2014,43(7):2747-2753
We have investigated the switching behavior of as-deposited CrO x and post-annealed CrO y films by use of a variety of electrodes (top electrode Ag, Ti; bottom electrode Pt, fluorine tin oxide (FTO)). Resistance switching is highly dependent on electrode material and post-annealing treatment. Among Pt devices, I–V hysteresis was observed for the Ag/CrO x /Pt device only; no resistance switching was observed for Ag/CrO y /Pt, Ti/CrO x /Pt, and Ti/CrO y /Pt devices. Among FTO devices, I–V hysteresis was observed for the Ag/CrO x /FTO device whereas I–V hysteresis with the opposite switching direction was observed for Ag/CrO y /FTO, Ti/CrO x /FTO, and Ti/CrO y /FTO devices. The direction of switching depends not only on electrode material but also on post-annealing treatment, which affects the density of grain boundaries. Thus, the density of grain boundaries determines the type of charge carrier involved in the switching process. For as-deposited CrO x films with a high density of grain boundaries Ag filament paths mediated by electrochemical redox reaction were observed, irrespective of bottom electrode material (Pt or FTO). Post-annealed CrO y films with a low density of grain boundaries suppressed electrochemical redox reaction in the Ag/CrO y /Pt device but promoted short-range movement of O2? ions through the bottom interface, resulting in resistance switching in the Ag/CrO y /FTO device. Electrochemical redox reaction-controlled resistance switching occurred solely in oxides with a high density of grain boundaries or dislocations. 相似文献
8.
A method is described whereby the precursors of 2-trans-nonenal may be estimated in worts and beers. Treatment of malt grist or malt with a variety of polar substances is shown to reduce or eliminate the production of nonenal precursors during mashing. Beers made from worts so treated have enhanced flavour stability over those made conventionally. 相似文献
9.
No-reference image quality assessment using structural activity 总被引:2,自引:0,他引:2
Presuming that human visual perception is highly sensitive to the structural information in a scene, we propose the concept of structural activity (SA) together with a model of SA indicator in a new framework for no-reference (NR) image quality assessment (QA) in this study. The proposed framework estimates image quality based on the quantification of the SA information of different visual significance. We propose some alternative implementations of SA indicator in this paper as examples to demonstrate the effectiveness of the SA-motivated framework. Comprehensive testing demonstrates that the model of SA indicator exhibits satisfactory performance in comparison with subjective quality scores as well as representative full-reference (FR) image quality measures. 相似文献
10.
LCD motion blur reduction: a signal processing approach. 总被引:1,自引:0,他引:1
Liquid crystal displays (LCDs) have shown great promise in the consumer market for their use as both computer and television displays. Despite their many advantages, the inherent sample-and-hold nature of LCD image formation results in a phenomenon known as motion blur. In this work, we develop a method for motion blur reduction using the Richardson-Lucy deconvolution algorithm in concert with motion vector information from the scene. We further refine our approach by introducing a perceptual significance metric that allows us to weight the amount of processing performed on different regions in the image. In addition, we analyze the role of motion vector errors in the quality of our resulting image. Perceptual tests indicate that our algorithm reduces the amount of perceivable motion blur in LCDs. 相似文献