全文获取类型
收费全文 | 1848篇 |
免费 | 65篇 |
国内免费 | 4篇 |
学科分类
工业技术 | 1917篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 9篇 |
2019年 | 23篇 |
2018年 | 36篇 |
2017年 | 25篇 |
2016年 | 38篇 |
2015年 | 27篇 |
2014年 | 54篇 |
2013年 | 86篇 |
2012年 | 82篇 |
2011年 | 130篇 |
2010年 | 91篇 |
2009年 | 89篇 |
2008年 | 104篇 |
2007年 | 103篇 |
2006年 | 99篇 |
2005年 | 72篇 |
2004年 | 58篇 |
2003年 | 61篇 |
2002年 | 62篇 |
2001年 | 40篇 |
2000年 | 37篇 |
1999年 | 40篇 |
1998年 | 76篇 |
1997年 | 60篇 |
1996年 | 53篇 |
1995年 | 39篇 |
1994年 | 35篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 13篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1977年 | 8篇 |
1976年 | 16篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有1917条查询结果,搜索用时 203 毫秒
41.
By having IT address itself instead of the business and its customers, we've seen IT projects emerge that have no business value, creating the public perception of IT as a black hole of funding. This black-hole perception magnifies when the IT department doesn't partner with company stakeholders when addressing actual needs; rather, IT professionals create solutions based on what they want to provide instead of what the business requires. The author describes why it's essential for IT professionals to turn outward rather than inward. 相似文献
42.
A Note on Incorporating Simultaneous Multi‐level Failure Time Data in System Reliability Assessments
下载免费PDF全文
![点击此处可从《Quality and Reliability Engineering International》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Todd L. Graves Michael S. Hamada 《Quality and Reliability Engineering International》2016,32(3):1127-1135
In this article, we present a method how to evaluate the likelihood for simultaneous failure time data when monitoring is stopped when the system fails. Our method is based on the reliability structure of the system, listing all possible events consistent with the simultaneous data and calculating their contributions to the likelihood. The method is simple to understand and is based on standard probabilistic calculations. We also consider the Jackson and Mosleh 5 method, and some results suggest that the two methods are equivalent. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
43.
44.
Lead scandium tantalate (PST) thin films have been deposited on a platinized silicon substrate with and without a buffer layer of MgO at the temperature of 525°C. It was found that PST films on the substrate without a buffer layer were strongly (1 1 1) oriented perovskite, whilst films on the substrate with a buffer layer showed the presence of second-phase pyrochlore, and the films were (1 1 1) and (1 1 0) oriented. These structural differences were believed to result from the structural differences between the platinum layers immediately below the respective PST layers. The lines which divide PST into network of islands were found to be no more than wider grain boundaries, rather than cracks as believed previously. Micro-beam diffraction and energy dispersive X-ray analysis showed that grain boundaries were tantalum-rich and lead-deficient compared to perovskite grain centres. Electrical properties, such as relative permittivity and dielectric loss, for the films were also measured. 相似文献
45.
Li Ding Timothy Lebo John S. Erickson Dominic DiFranzo Gregory Todd Williams Xian Li James Michaelis Alvaro Graves Jin Guang Zheng Zhenning Shangguan Johanna Flores Deborah L. McGuinness James A. Hendler 《Journal of Web Semantics》2011,9(3):325-333
International open government initiatives are releasing an increasing volume of raw government datasets directly to citizens via the Web. The transparency resulting from these releases not only creates new application opportunities but also imposes new burdens inherent to large-scale distributed data integration, collaborative data manipulation and transparent data consumption. The Tetherless World Constellation (TWC) at Rensselaer Polytechnic Institute (RPI) has developed the Semantic Web-based TWC LOGD portal to support the deployment of linked open government data (LOGD). The portal is both an open source infrastructure supporting linked open government data production and consumption and a vibrant community portal that educates and serves the growing international open government community of developers, data curators and end users. This paper motivates and introduces the TWC LOGD Portal and highlights innovative aspects and lessons learned. 相似文献
46.
Multi-spectral fusion for surveillance systems 总被引:1,自引:0,他引:1
Simon Denman Author Vitae Todd Lamb Author Vitae Author Vitae Vinod Chandran Author Vitae Author Vitae 《Computers & Electrical Engineering》2010,36(4):643-663
Surveillance systems such as object tracking and abandoned object detection systems typically rely on a single modality of colour video for their input. These systems work well in controlled conditions but often fail when low lighting, shadowing, smoke, dust or unstable backgrounds are present, or when the objects of interest are a similar colour to the background. Thermal images are not affected by lighting changes or shadowing, and are not overtly affected by smoke, dust or unstable backgrounds. However, thermal images lack colour information which makes distinguishing between different people or objects of interest within the same scene difficult.By using modalities from both the visible and thermal infrared spectra, we are able to obtain more information from a scene and overcome the problems associated with using either modality individually. We evaluate four approaches for fusing visual and thermal images for use in a person tracking system (two early fusion methods, one mid fusion and one late fusion method), in order to determine the most appropriate method for fusing multiple modalities. We also evaluate two of these approaches for use in abandoned object detection, and propose an abandoned object detection routine that utilises multiple modalities. To aid in the tracking and fusion of the modalities we propose a modified condensation filter that can dynamically change the particle count and features used according to the needs of the system.We compare tracking and abandoned object detection performance for the proposed fusion schemes and the visual and thermal domains on their own. Testing is conducted using the OTCBVS database to evaluate object tracking, and data captured in-house to evaluate the abandoned object detection. Our results show that significant improvement can be achieved, and that a middle fusion scheme is most effective. 相似文献
47.
In this paper, a four-terminal piezoresistive sensor commonly known as a van der Pauw (VDP) structure is presented for its
application to MEMS pressure sensing. In a recent study, our team has determined the relation between the biaxial stress state
and the piezoresistive response of a VDP structure by combining the VDP resistance equations with the equations governing
silicon piezoresistivity and has proposed a new piezoresistive pressure sensor. It was observed that the sensitivity of the
VDP sensor is over three times higher than the conventional filament type Wheatstone bridge resistor. To check our theoretical
findings, we fabricated several (100) silicon diaphragms with both the VDP sensors and filament resistor sensors on the same
wafer so both the sensor elements have same doping concentration. Several diaphragms had VDP sensors of different sizes and
orientations to find out their geometric effects on pressure sensitivity. The diaphragms were subjected to known pressures,
and the pressure sensitivities of both types of sensors were measured using an in-house built calibration setup. It was found
that the VDP devices had a linear response to pressure as expected, and were more sensitive than the resistor sensors. Also,
the VDP sensors provided a number of additional advantages, such as its size independent sensitivity and simple fabrication
steps due to its simple geometry. 相似文献
48.
49.
An Architecture for Human‐Guided Autonomy: Team TROOPER at the DARPA Robotics Challenge Finals
下载免费PDF全文
![点击此处可从《野外机器人技术杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Steven Gray Robert Chevalier David Kotfis Benjamin Caimano Kenneth Chaney II Aron Rubin Kingsley Fregene Todd Danko 《野外机器人技术杂志》2017,34(5):852-873
Recent robotics efforts have automated simple, repetitive tasks to increase execution speed and lessen an operator's cognitive load, allowing them to focus on higher‐level objectives. However, an autonomous system will eventually encounter something unexpected, and if this exceeds the tolerance of automated solutions, there must be a way to fall back to teleoperation. Our solution is a largely autonomous system with the ability to determine when it is necessary to ask a human operator for guidance. We call this approach human‐guided autonomy. Our design emphasizes human‐on‐the‐loop control where an operator expresses a desired high‐level goal for which the reasoning component assembles an appropriate chain of subtasks. We introduce our work in the context of the DARPA Robotics Challenge (DRC) Finals. We describe the software architecture Team TROOPER developed and used to control an Atlas humanoid robot. We employ perception, planning, and control automation for execution of subtasks. If subtasks fail, or if changing environmental conditions invalidate the planned subtasks, the system automatically generates a new task chain. The operator is able to intervene at any stage of execution, to provide input and adjustment to any control layer, enabling operator involvement to increase as confidence in automation decreases. We present our performance at the DRC Finals and a discussion about lessons learned. 相似文献
50.
Mapping wildfire and clearcut harvest disturbances in boreal forests with Landsat time series data 总被引:1,自引:0,他引:1
Information regarding the extent, timing and magnitude of forest disturbance are key inputs required for accurate estimation of the terrestrial carbon balance. Equally important for studying carbon dynamics is the ability to distinguish the cause or type of forest disturbance occurring on the landscape. Wildfire and timber harvesting are common disturbances occurring in boreal forests, with each having differing carbon consequences (i.e., biomass removed, recovery rates). Development of methods to not only map, but distinguish these types of disturbance with satellite data will depend upon an improved understanding of their distinctive spectral properties. In this study, we mapped wildfires and clearcut harvests occurring in a Landsat time series (LTS) acquired in the boreal plains of Saskatchewan, Canada. This highly accurate reference map (kappa = 0.91) depicting the year and cause of historical disturbances was used to determine the spectral and temporal properties needed to accurately classify fire and clearcut disturbances. The results showed that spectral data from the short-wave infrared (SWIR; e.g., Landsat band 5) portion of the electromagnetic spectrum was most effective at separating fires and clearcut harvests possibly due to differences in structure, shadowing, and amounts of exposed soil left behind by the two disturbance types. Although SWIR data acquired 1 year after disturbance enabled the most accurate discrimination of fires and clearcut harvests, good separation (e.g., kappa ≥ 0.80) could still be achieved with Landsat band 5 and other SWIR-based indices 3 to 4 years after disturbance. Conversely, minimal disturbance responses in near infrared-based indices associated with green leaf area (e.g., NDVI) led to unreliably low classification accuracies regardless of time since disturbance. In addition to exploring the spectral and temporal manifestation of forest disturbance types, we also demonstrate how Landsat change maps which attribute cause of disturbance can be used to help elucidate the social, ecological and carbon consequences associated with wildfire and clearcut harvesting in Canadian boreal forests. 相似文献