全文获取类型
收费全文 | 3242篇 |
免费 | 131篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 53篇 |
综合类 | 59篇 |
化学工业 | 560篇 |
金属工艺 | 109篇 |
机械仪表 | 100篇 |
建筑科学 | 87篇 |
矿业工程 | 10篇 |
能源动力 | 146篇 |
轻工业 | 190篇 |
水利工程 | 15篇 |
石油天然气 | 15篇 |
武器工业 | 2篇 |
无线电 | 474篇 |
一般工业技术 | 708篇 |
冶金工业 | 401篇 |
原子能技术 | 15篇 |
自动化技术 | 464篇 |
出版年
2023年 | 23篇 |
2022年 | 54篇 |
2021年 | 72篇 |
2020年 | 39篇 |
2019年 | 43篇 |
2018年 | 52篇 |
2017年 | 58篇 |
2016年 | 66篇 |
2015年 | 51篇 |
2014年 | 91篇 |
2013年 | 246篇 |
2012年 | 177篇 |
2011年 | 185篇 |
2010年 | 149篇 |
2009年 | 173篇 |
2008年 | 154篇 |
2007年 | 139篇 |
2006年 | 153篇 |
2005年 | 113篇 |
2004年 | 99篇 |
2003年 | 82篇 |
2002年 | 73篇 |
2001年 | 69篇 |
2000年 | 69篇 |
1999年 | 74篇 |
1998年 | 113篇 |
1997年 | 101篇 |
1996年 | 116篇 |
1995年 | 70篇 |
1994年 | 63篇 |
1993年 | 51篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 34篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1977年 | 12篇 |
1976年 | 15篇 |
1975年 | 5篇 |
1972年 | 6篇 |
1970年 | 2篇 |
排序方式: 共有3408条查询结果,搜索用时 15 毫秒
41.
Process simulation and fabrication of advanced multi-step three-dimensional braided preforms 总被引:3,自引:0,他引:3
The fundamentals of multi-step braiding for the fabrication of three-dimensional fibre preforms for composites have been studied. To facilitate the understanding of the complex multi-step braiding processes, a computer simulation algorithm has been developed. The simulation acts as a tool to allow the identification of individual yarn paths, number and location of yarn groups, and braid geometry. It was found that individual control of the rows and columns of yarn carriers on a Cartesian braiding bed allows for the fabrication of advanced multi-step braids; the micro-structural possibilities of three-dimensional braids are thus greatly extended. Some basic relationships of the braiding parameters have been identified. It has been concluded that the traditional four-step and two-step braidings are special cases of multi-step braidings. To verify the feasibility of the structures, experimental investigations have also been carried out. Innovative braid architectures have been designed and fabricated using a prototype multi-step braiding machine. 相似文献
42.
Bo-Cheng Tao Wei Zhang Wen-Chieh Chou Fangyu Wang Yapeng Huang Yanan Li 《Journal of the Society for Information Display》2023,31(10):599-607
In this article, novel n-FFS liquid crystal material from Slichem was used in order to elevate the anti-backlight long aging effect; a trace amount of free radical trap HALS-like additive was added, the principle of which can be expressed via Denisov cycle, confirmed by measuring the temporal VHR changes in test cells; three different resolution (FHD ~ QHD) models paired with N19 and N21 were selected for testing by comparing the actual panel. It is verified that the optimized material greatly improves the image sticking performance of the panel and keeping optical performance. 相似文献
43.
Sodium-ion batteries have received remarkable attention as next-generation high-performance electrochemical energy storage devices because of their cost effectiveness and the broad geographical distribution of sodium. As a critical component of sodium-ion batteries, anode materials, especially nanostructured anodes, have a significant effect on the electrochemical performance of sodium-ion batteries. Recent research indicates that phosphorus and metal phosphides show great promise as anode candidates for sodium-ion batteries because of their low cost and relatively high theoretical gravimetric and volumetric specific capacities. In this review, we systematically summarize recent research progress on state-of-the-art nanostructured phosphorus and phosphides, including the synthetic strategies, Na-storage mechanisms, and the relationship between the nanostructure and electrochemical performance. Moreover, we present an overview of future challenges and opportunities based on current developments. 相似文献
44.
Researchers on organisational ambidexterity have proposed several solutions to address the potential conflicts between exploration activities and exploitation activities. Unlike simultaneous ambidexterity, sequential ambidexterity – defined as temporal switching between exploration and exploitation – has not been examined fully, and the conditions under which this temporal switching can be successful are unclear. This paper proposes the concept of temporal switching capability to better understand the process by which sequential ambidexterity is executed. In addition, we hypothesise that performance effects are contingent upon firm-specific factors: a firm’s business strategy and absorptive capacity. Utilising three sources of data – a secondary database, annual reports and a survey administered to 145 firms in the electronics industry with 10-year observations – we find support for our hypotheses. The results show that the temporal switching capability positively relates to new product performance and that business strategy type and absorptive capacity have moderating effects. The results are meaningful in both theory and practice. 相似文献
45.
An amplitude-sensitive optical heterodyne polarimeter was set up to monitor noninvasively the aqueous glucose concentration in a rabbit's eye. A Zeeman laser in conjunction with a Glan-Thompson analyzer was used to generate an optical heterodyne signal. The amplitude of the heterodyne signal linearly related to the optical rotation angle of the aqueous glucose. The concentration of the aqueous glucose in a rabbit's eyeball was measured in vivo. There was a 30-min time delay between observations of aqueous glucose and blood glucose. The detection capability and the reproducibility of the experiment are demonstrated and discussed. 相似文献
46.
Current multimedia extensions provide a mechanism for general-purpose processors to meet the growing performance demand of multimedia applications. However, the computing performance of these extensions is often limited for the design conceptions of the single data stream. This paper presents an architecture called “multi-streaming SIMD” that enables current multimedia extensions to simultaneously manipulate multiple data streams. To efficiently and flexibly realize the proposed architecture, an operation cell is designed by fusing the logic gates and the storage cells together. Multiple operation cells then are connected to compose a register file with the ability of performing SIMD operations called “Multimedia Operation Storage Unit (MOSU)”. Further, many MOSUs are used to compose a multi-streaming SIMD computing engine that can simultaneously manipulate multiple data streams and exploit the subword parallelisms of the elements in each data stream. This paper also designs three instruction modes (global, coupling, and isolated modes) for programmers to dynamically configure the multi-streaming SIMD computing engine at the instruction level to manipulate different amounts of data streams. Simulation results show that when the multi-streaming SIMD architecture has four 4-register MOSUs, it provides a factor of 3.3×–5.5× performance enhancement for traditional MMX extensions on 12 multimedia kernels. 相似文献
47.
Ya‐Hui Yang Sidney S. Yang Kan‐Sen Chou 《Journal of the Society for Information Display》2010,18(10):745-748
Abstract— This study investigates the effects of subjecting zinc oxide (ZnO) thin films to laser irradiation. The optical, structural, and electrical properties of the as‐deposited and laser‐irradiated films at different laser energies were studied. The transmittances without/with laser irradiation showed a net increase from 85 to 92% (@550 nm) for 250‐nm ZnO films, indicating an improvement in sample crystal linity. In addition, laser treatment decreased the ZnO band gap. Composition structure analysis shows that the crystallinity increased when the laser energy increased. Thin‐film transistors (TFTs) with a ZnO active layer were fabricated. The mobility of as‐deposited ZnO TFT devices (0.19 cm2/V‐sec) increased more than 2.5 times for ZnO of unirradiated laser treatment (0.49 cm2/V‐sec). 相似文献
48.
The automated structural optimization system (ASOS) proposed in the previous work incorporates the image-preprocessing techniques, the image-interpreting technique, and the automated shape-optimization modeling techniques to successfully obtain an autonomously integrated topology and shape optimization. However, the characteristic value-based image-interpreting technique used in ASOS is unable to accurately interpret complicated hole shapes, necessitating the use of the hole shape-adjusting strategy in addition to the hole-expanding strategy and the interference analysis in the automated shape-optimization modeling techniques to obtain a viable initial design and side constraints of design variables. In order to solve the above-mentioned problem in ASOS, this paper proposes the improved automated structural optimization system (IASOS) and uses the polygonal image-interpreting technique to replace the characteristic value-based image-interpreting technique used in ASOS. This alteration significantly increases the accuracy of image interpretation. Moreover, it can simplify the process of automated shape-optimization modeling techniques, reduce the design duration, and produce better results. 相似文献
49.
The field of micro–electro–mechanical systems and microfabrication has produced micro-total-analysis systems, which are widely
used in medicine, diagnostics, and biological and chemical research. For the development of high precision drug delivery systems,
micropumps with a lead zirconate titanate (PZT) actuator, which has a fast response time and high resolution, are most likely
to be applied in implementations. To improve the performance of PZT micropumps utilized in the microfluidics field, suitable
models are required to enable the optimization of the PZT actuator driving circuits. This study proposes a modified Butterworth–Van
Dyke (BVD) model which consists of a BVD model in series with an electrical resistance that describes a PZT actuator driven
by a square pulse with a relatively high voltage and low frequency for micropump applications. Experiments were conducted
to assess parameters of the model at various voltages; they indicate that the electrical resistance is essential for modeling
the PZT actuator of the micropump. The electrical model was verified using a SPICE simulation, whose numerical results were
compared with the experimental data for the current response of the PZT actuator. The results show a close correlation between
the simulation of the electrical model and the measurements of the PZT actuator under real operating conditions. 相似文献
50.
A large number of methods have been proposed for ranking fuzzy numbers in the last few decades. Nevertheless, none of these methods can always guarantee a consistent result for every situation. Some of them are even non-intuitive and not discriminating. Chen proposed a ranking method in 1985 to overcome these limitations and simplify the computational procedure based on the criteria of total utility through maximizing set and minimizing set. However, there were some shortcomings associated with Chen’s ranking method. Therefore, we propose a revised ranking method that can overcome these shortcomings. Instead of considering just a single left and a single right utility in the total utility, the proposed method considers two left and two right utilities. In addition, the proposed method also takes into account the decision maker’s optimistic attitude of fuzzy numbers. Several comparative examples and an application demonstrating the usage, advantages, and applicability of the revised ranking method are presented. It can be concluded that the revised ranking method can effectively resolve the issues with Chen’s ranking method. Moreover, the revised ranking method can be used to differentiate different types of fuzzy numbers. 相似文献