全文获取类型
收费全文 | 6072篇 |
免费 | 249篇 |
国内免费 | 242篇 |
专业分类
电工技术 | 165篇 |
综合类 | 400篇 |
化学工业 | 118篇 |
金属工艺 | 200篇 |
机械仪表 | 522篇 |
建筑科学 | 303篇 |
矿业工程 | 139篇 |
能源动力 | 56篇 |
轻工业 | 143篇 |
水利工程 | 84篇 |
石油天然气 | 50篇 |
武器工业 | 33篇 |
无线电 | 730篇 |
一般工业技术 | 240篇 |
冶金工业 | 36篇 |
原子能技术 | 18篇 |
自动化技术 | 3326篇 |
出版年
2024年 | 8篇 |
2023年 | 80篇 |
2022年 | 76篇 |
2021年 | 138篇 |
2020年 | 124篇 |
2019年 | 94篇 |
2018年 | 61篇 |
2017年 | 95篇 |
2016年 | 122篇 |
2015年 | 167篇 |
2014年 | 287篇 |
2013年 | 284篇 |
2012年 | 391篇 |
2011年 | 405篇 |
2010年 | 362篇 |
2009年 | 427篇 |
2008年 | 378篇 |
2007年 | 414篇 |
2006年 | 462篇 |
2005年 | 433篇 |
2004年 | 314篇 |
2003年 | 347篇 |
2002年 | 305篇 |
2001年 | 188篇 |
2000年 | 202篇 |
1999年 | 116篇 |
1998年 | 76篇 |
1997年 | 34篇 |
1996年 | 26篇 |
1995年 | 27篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有6563条查询结果,搜索用时 15 毫秒
1.
This paper introduces the design of a hardware efficient reconfigurable pseudorandom number generator (PRNG) using two different feedback controllers based four-dimensional (4D) hyperchaotic systems i.e. Hyperchaotic-1 and -2 to provide confidentiality for digital images. The parameter's value of these two hyperchaotic systems is set to be a specific value to get the benefits i.e. all the multiplications (except a few multiplications) are performed using hardwired shifting operations rather than the binary multiplications, which doesn't utilize any hardware resource. The ordinary differential equations (ODEs) of these two systems have been exploited to build a generic architecture that fits in a single architecture. The proposed architecture provides an opportunity to switch between two different 4D hyperchaotic systems depending on the required behavior. To ensure the security strength, that can be also used in the encryption process in which encrypt the input data up to two times successively, each time using a different PRNG configuration. The proposed reconfigurable PRNG has been designed using Verilog HDL, synthesized on the Xilinx tool using the Virtex-5 (XC5VLX50T) and Zynq (XC7Z045) FPGA, its analysis has been done using Matlab tool. It has been found that the proposed architecture of PRNG has the best hardware performance and good statistical properties as it passes all fifteen NIST statistical benchmark tests while it can operate at 79.101-MHz or 1898.424-Mbps and utilize only 0.036 %, 0.23 %, and 1.77 % from the Zynq (XC7Z045) FPGA's slice registers, slice LUTs, and DSP blocks respectively. Utilizing these PRNGs, we design two 16 × 16 substitution boxes (S-boxes). The proposed S-boxes fulfill the following criteria: Bijective, Balanced, Non-linearity, Dynamic Distance, Strict Avalanche Criterion (SAC) and BIC non-linearity criterion. To demonstrate these PRNGs and S-boxes, a new three different scheme of image encryption algorithms have been developed: a) Encryption using S-box-1, b) Encryption using S-box-2 and, c) Two times encryption using S-box-1 and S-box-2. To demonstrate that the proposed cryptosystem is highly secure, we perform the security analysis (in terms of the correlation coefficient, key space, NPCR, UACI, information entropy and image encryption quantitatively in terms of (MSE, PSNR and SSIM)). 相似文献
2.
This article presents the construction and consumption of hyperjerk system having chaotic nature with the commensurate ordered fractional derivative on rapidly digitalized emerging technologies. The system analyzed analytically using Lipschitz condition and numerically with the help of predictor corrector approaches. Originality of constructed system is confirmed using log error plots which gives satisfactory small values on finite time scale. The dynamical performances of the complex system are termed in multiple phase planes by the mean of their significant nature. Stability and bifurcation analysis around the fractional derivative is also studies for the various parameter of system to check the visibility of chaotic solution. The system is also designed in analog circuit simulator with the aid of operational amplifier, anti-parallel semiconductor diodes for validation of the system. With the help of random number generators (RNGs), binary array generated from the hyperjerk system and plugged in to the NIST 800–22 test suite to measure the randomness. The array having high randomness is used as strong cypher key for the cryptographic execution straightforwardly in both direction encryption and decryption. 相似文献
3.
Saliency4ASD: Challenge,dataset and tools for visual attention modeling for autism spectrum disorder
The recent studies showing that gaze features can be useful in the identification of Autism Spectrum Disorder (ASD), have opened a new domain where Visual Attention (VA) modeling could be of great help. In this sense, this paper presents a report of the Grand Challenge “Saliency4ASD: Visual attention modeling for Autism Spectrum Disorder”, organized at IEEE ICME’19, aiming at supporting the research on VA modeling towards this healthcare societal challenge. In particular, this paper describes the workflow, obtained results, and datasets and tools that were used within this activity, in order to help on the development and evaluation of two types of VA models: (1) to predict saliency maps that fit gaze behavior of people with ASD, and (2) to identify individuals with ASD from typical development. 相似文献
4.
现阶段所采用的跟踪方法对后继帧视频图像目标跟踪存在跟踪效果不理想、跟踪效率较低等问题。提出基于视觉传达的后继帧视频图像目标跟踪方法。利用图像差分方法获取视频图像运动目标可能出现的区域,并对这个区域视频图像目标进行运动估计,采用形态学方法来降低聚类区域的数量,得到后继帧视频图像目标区域;采用均值漂移法估计后继帧视图像核概率密度,对后继帧视频图像进行分割处理,找出后继帧视频图像目标区域最显著的特征,通过迭代运算找到目标位置,实现目标跟踪。实验结果表明,所提算法具有较好的后继帧视频图像跟踪效果、并且跟踪效率较高,具有一定的应用价值。 相似文献
5.
Search results of spatio-temporal data are often displayed on a map, but when the number of matching search results is large, it can be time-consuming to individually examine all results, even when using methods such as filtered search to narrow the content focus. This suggests the need to aggregate results via a clustering method. However, standard unsupervised clustering algorithms like -means (i) ignore relevance scores that can help with the extraction of highly relevant clusters, and (ii) do not necessarily optimize search results for purposes of visual presentation. In this article, we address both deficiencies by framing the clustering problem for search-driven user interfaces in a novel optimization framework that (i) aims to maximize the relevance of aggregated content according to cluster-based extensions of standard information retrieval metrics and (ii) defines clusters via constraints that naturally reflect interface-driven desiderata of spatial, temporal, and keyword coherence that do not require complex ad-hoc distance metric specifications as in -means. After comparatively benchmarking algorithmic variants of our proposed approach – RadiCAL – in offline experiments, we undertake a user study with 24 subjects to evaluate whether RadiCAL improves human performance on visual search tasks in comparison to -means clustering and a filtered search baseline. Our results show that (a) our binary partitioning search (BPS) variant of RadiCAL is fast, near-optimal, and extracts higher-relevance clusters than -means, and (b) clusters optimized via RadiCAL result in faster search task completion with higher accuracy while requiring a minimum workload leading to high effectiveness, efficiency, and user satisfaction among alternatives. 相似文献
6.
Aircraft accident investigation has played a pivotal role in improving the safety of aviation. Advances in recorder technology, specifically Cockpit Voice Recorders (CVRs) and Flight Data Recorders (FDR) have made a huge contribution to the understanding of occurrences for accident investigators. However, even these recorders have limitations such as the evidence they provide about pilots' situation awareness or behaviours. Supplementing audio and data recordings with video has been discussed for many years and whilst there continues to be debate among regulators, operators, manufacturers and pilot unions, the International Civil Aviation Organization (ICAO) has mandated Airborne Image Recorders (AIR) from 2023. The purpose of installing such systems is to provide evidence of crew operational behaviours in terms of both human-human and human-computer interactions (HCI) on the flight deck. Video alone is unlikely to provide sufficient evidence for investigators. This study examines the additional value that eye-tracking technology may provide through the case study of an accident involving an Airbus A330-300 aircraft which experienced a rejected landing. Currently, the investigation of such events, where crew interaction with automation is critical to their situation awareness, relies heavily on interview data. Such data may be unavailable (in the case of serious injury) or unreliable (based on hindsight bias). By integrating eye tracking technology into an AIR, accident investigators will potentially gain a better understanding of pilots’ visual scan patterns across flight deck instrumentation. This has implications for flight deck and procedural design as well as training and simulation. 相似文献
7.
8.
IntroductionThe main purpose of this cross-sectional study was to investigate whether visual discomfort acts as a mediating factor between perceived visual ergonomic working conditions and self-rated visual performance among office workers who carry out administrative tasks and computer-based work at the Swedish Tax Agency.MethodsA questionnaire was sent to 94 office workers addressing: 1) perceived visual quality of the visual display units; 2) prevalence of eye symptoms; and 3) self-rated visual performance. Eighty-six persons (54 women (63%), 31 men (36%), and 1 of unspecified sex) answered the questionnaire. Multiple regression analysis investigated the association between visual ergonomic working conditions and visual performance, both with and without visual discomfort as a mediator.ResultsThe group mean of the Indexed survey questions indicated a reasonably good quality of visual ergonomic working conditions, a relative absence of eye symptoms, and acceptable self-rated visual performance. Results from multiple regression analysis showed a significant association between perceived visual ergonomic working conditions and self-rated visual performance (r2 = 0.30, β = 0.327, p < 0.01). When visual discomfort was used as a mediator, the association between perceived visual ergonomic working conditions and self-rated visual performance remained the same (r2 = 0.32, β = 0.315, p < 0.01).DiscussionIt was remarkable to discover that self-rated visual performance was independent of visual discomfort. Possible explanations include exposure factors not included in the current study, such as dry air and sensory irritation in the eyes, psychosocial stress, time spent performing near work activities, or time exposed to visually deficient working conditions.Relevance to industryThe strong connection between satisfaction with visual ergonomic working conditions and productivity in this study has implications for workplace profitability and staff satisfaction. If productivity is enhanced by better visual ergonomic working conditions, then managers of workplaces may be able to improve work outcomes by optimizing the physical work environment. 相似文献
9.
《Displays》2021
Many studies have shown the benefits of augmented reality (AR) to improve manufacturing and control processes in industry. However, the presentation of AR content through optical see-through head-mounted displays may induce unnatural viewing conditions, which consequences on the user’s visual system have not been investigated yet. This study aimed at assessing whether using AR instructions to guide a manual task, i.e., conditions where the user is forced to repeatedly look at and accommodate in different planes to extract information from both real and virtual environments, could potentially impact the visual system of operators. A before/after design study was carried out, asking 26 participants to perform Lego assemblies for 30 min with either paper or AR instructions. The effects of using AR compared to paper instructions were evaluated both on binocular vision, with classical optometric measurements, and on visual fatigue, with the Virtual Reality Symptoms Questionnaire. No clinically significant differences in optometric measurements (far/near visual acuity, stereoacuity, phoria, convergence, fusional amplitude, accommodation amplitude, accommodative convergence) have been found between AR and paper instructions, and only negligible fatigue symptoms have been seen specifically for AR. Results from both objective and subjective measurements suggest that there is no impact of AR on the oculomotor system and that, in this specific case of use, AR can be safely used for production operators. 相似文献
10.
The visual ability factors of peripheral perception, visual reaction and visual pursuit ability are important for safe driving. Thus, this study explored the influence of driving experience on these visual ability factors. Sixty-five drivers, including novice and experienced drivers, participated in this study. The visual ability levels of the three factors were measured by the Vienna Test System. In addition, driver's awareness of the three factors' importance for safe driving was measured by questionnaire items. Results showed that out of the three factors, drivers' peripheral perception ability was correlated significantly with their driving experience. Experienced drivers had higher peripheral perception ability than that of novice drivers. In addition, compared with novice drivers, experienced drivers believed that peripheral perception was more important whereas visual reaction was less important. It is suggested that higher attention should be paid to peripheral perception in driving training and novice drivers should increase their importance awareness for this factor. 相似文献