全文获取类型
收费全文 | 19366篇 |
免费 | 2571篇 |
国内免费 | 1611篇 |
专业分类
电工技术 | 1573篇 |
技术理论 | 1篇 |
综合类 | 2590篇 |
化学工业 | 667篇 |
金属工艺 | 420篇 |
机械仪表 | 2103篇 |
建筑科学 | 3582篇 |
矿业工程 | 1288篇 |
能源动力 | 470篇 |
轻工业 | 394篇 |
水利工程 | 698篇 |
石油天然气 | 405篇 |
武器工业 | 383篇 |
无线电 | 2365篇 |
一般工业技术 | 1463篇 |
冶金工业 | 467篇 |
原子能技术 | 140篇 |
自动化技术 | 4539篇 |
出版年
2024年 | 79篇 |
2023年 | 279篇 |
2022年 | 455篇 |
2021年 | 542篇 |
2020年 | 632篇 |
2019年 | 492篇 |
2018年 | 507篇 |
2017年 | 584篇 |
2016年 | 722篇 |
2015年 | 818篇 |
2014年 | 1313篇 |
2013年 | 1141篇 |
2012年 | 1641篇 |
2011年 | 1549篇 |
2010年 | 1276篇 |
2009年 | 1267篇 |
2008年 | 1260篇 |
2007年 | 1454篇 |
2006年 | 1193篇 |
2005年 | 1145篇 |
2004年 | 901篇 |
2003年 | 746篇 |
2002年 | 600篇 |
2001年 | 539篇 |
2000年 | 496篇 |
1999年 | 394篇 |
1998年 | 276篇 |
1997年 | 256篇 |
1996年 | 177篇 |
1995年 | 155篇 |
1994年 | 181篇 |
1993年 | 100篇 |
1992年 | 72篇 |
1991年 | 61篇 |
1990年 | 41篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1962年 | 3篇 |
1959年 | 5篇 |
1956年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Highly accurate real‐time localization is of fundamental importance for the safety and efficiency of planetary rovers exploring the surface of Mars. Mars rover operations rely on vision‐based systems to avoid hazards as well as plan safe routes. However, vision‐based systems operate on the assumption that sufficient visual texture is visible in the scene. This poses a challenge for vision‐based navigation on Mars where regions lacking visual texture are prevalent. To overcome this, we make use of the ability of the rover to actively steer the visual sensor to improve fault tolerance and maximize the perception performance. This paper answers the question of where and when to look by presenting a method for predicting the sensor trajectory that maximizes the localization performance of the rover. This is accomplished by an online assessment of possible trajectories using synthetic, future camera views created from previous observations of the scene. The proposed trajectories are quantified and chosen based on the expected localization performance. In this study, we validate the proposed method in field experiments at the Jet Propulsion Laboratory (JPL) Mars Yard. Furthermore, multiple performance metrics are identified and evaluated for reducing the overall runtime of the algorithm. We show how actively steering the perception system increases the localization accuracy compared with traditional fixed‐sensor configurations. 相似文献
2.
3.
This paper proposes a novel optimization algorithm inspired by the ions motion in nature. In fact, the proposed algorithm mimics the attraction and repulsion of anions and cations to perform optimization. The proposed algorithm is designed in such a way to have the least tuning parameters, low computational complexity, fast convergence, and high local optima avoidance. The performance of this algorithm is benchmarked on 10 standard test functions and compared to four well-known algorithms in the literature. The results demonstrate that the proposed algorithm is able to show very competitive results and has merits in solving challenging optimization problems. 相似文献
4.
基于传统AI-EBG结构,提出了一种小尺寸的增强型电磁带隙结构,实现了从0.5~9.4 GHz的宽频带-40 dB噪声抑制深度,且下截止频率减少到数百MHz,可有效抑制多层PCB板间地弹噪声。文中同时研究了EBG结构在高速电路应用时的信号完整性问题,使用差分信号方案可改善信号完整性。 相似文献
5.
Differences between oculomotor and perceptual artifacts for temporally limited head mounted displays
Alexander Goettker Kevin J. MacKenzie T. Scott Murdison 《Journal of the Society for Information Display》2020,28(6):509-519
We used perceptual and oculomotor measures to understand the negative impacts of low (phantom array) and high (motion blur) duty cycles with a high‐speed, AR‐likehead‐mounted display prototype. We observed large intersubject variability for the detection of phantom array artifacts but a highly consistent and systematic effect on saccadic eye movement targeting during low duty cycle presentations. This adverse effect on saccade endpoints was also related to an increased error rate in a perceptual discrimination task, showing a direct effect of display duty cycle on the perceptual quality. For high duty cycles, the probability of detecting motion blur increased during head movements, and this effect was elevated at lower refresh rates. We did not find an impact of the temporal display characteristics on compensatory eye movements during head motion (e.g., VOR). Together, our results allow us to quantify the tradeoff of different negative spatiotemporal impacts of user movements and make subsequent recommendations for optimized temporal HMD parameters. 相似文献
6.
7.
8.
The scale along the coordinate axes in the equations of motion hitherto used for an H-maser (in relative units) is shown to depend on Q as the quality factor for an H-maser. This hinders both analysis of the operation of the H-maser and optimization of its parameters. The modified equations of motion proposed here do not have that shortcoming. We determine the atomic flux into the bulb that gives the H-maser the best metrological characteristics. 相似文献
9.
S V Bhat 《Bulletin of Materials Science》1994,17(7):1271-1285
When examined using continuous wave electron paramagnetic resonance and nuclear magnetic resonance spectrometers, the highT
c superconductors give rise to intense, low field, ‘non-resonant’ absorption signals in the superconducting state. This phenomenon
can be used as a highly sensitive, contactless technique for the detection and characterization of superconductivity even
in samples containing only minute amounts of the superconducting phase. Further, it can also be applied to the determination
of material parameters of interest such asJ
c andH
c2 in addition to being a powerful way of distinguishing between weak-link superconductivity and bulk superconductivity. The
details of these aspects are discussed. 相似文献
10.
Estimating the state of a nonlinear stochastic system (observed through a nonlinear noisy measurement channel) has been the goal of considerable research to solve both filtering and control problems. In this paper, an original approach to the solution of the optimal state estimation problem by means of neural networks is proposed, which consists in constraining the state estimator to take on the structure of a multilayer feedforward network. Both non-recursive and recursive estimation schemes are considered, which enable one to reduce the original functional problem to a nonlinear programming one. As this reduction entails approximations for the optimal estimation strategy, quantitative results on the accuracy of such approximations are reported. Simulation results confirm the effectiveness of the proposed method. 相似文献