全文获取类型
收费全文 | 90960篇 |
免费 | 1463篇 |
国内免费 | 407篇 |
学科分类
工业技术 | 92830篇 |
出版年
2023年 | 114篇 |
2022年 | 66篇 |
2021年 | 166篇 |
2020年 | 131篇 |
2019年 | 129篇 |
2018年 | 14660篇 |
2017年 | 13618篇 |
2016年 | 10220篇 |
2015年 | 836篇 |
2014年 | 538篇 |
2013年 | 769篇 |
2012年 | 3514篇 |
2011年 | 9804篇 |
2010年 | 8612篇 |
2009年 | 5886篇 |
2008年 | 7171篇 |
2007年 | 8146篇 |
2006年 | 400篇 |
2005年 | 1441篇 |
2004年 | 1315篇 |
2003年 | 1371篇 |
2002年 | 707篇 |
2001年 | 260篇 |
2000年 | 308篇 |
1999年 | 163篇 |
1998年 | 155篇 |
1997年 | 134篇 |
1996年 | 137篇 |
1995年 | 62篇 |
1994年 | 77篇 |
1993年 | 61篇 |
1992年 | 50篇 |
1991年 | 69篇 |
1986年 | 43篇 |
1985年 | 100篇 |
1984年 | 64篇 |
1983年 | 48篇 |
1982年 | 46篇 |
1980年 | 45篇 |
1968年 | 56篇 |
1967年 | 42篇 |
1966年 | 50篇 |
1965年 | 45篇 |
1960年 | 38篇 |
1959年 | 40篇 |
1958年 | 43篇 |
1957年 | 44篇 |
1956年 | 43篇 |
1955年 | 69篇 |
1954年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
ABSTRACT The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style. 相似文献
3.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
4.
5.
6.
7.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献
8.
9.
10.
Kurjenniemi Janne Hämäläinen Seppo Ristaniemi Tapani 《Wireless Personal Communications》2003,27(4):337-351
In this article we consider the performance of the 3.84 Mcpstime-division duplex (TDD) mode of UTRA (Universal TerrestrialRadio Access) network. We emphasize two of the radio resourcemanagement algorithms, handover and uplink power control, whoserole in the overall system performance is studied extensively.First, a handover algorithm used in WCDMA (Wideband Code DivisionMultiple Access) standard is considered in a TDD-mode operation.This gives rise to a careful setting of different handoverparameters, and the evaluation of the effects to the systemperformance. Secondly, the specified uplink power controlalgorithm is considered. Since it is based on several user-mademeasurements which may involve both random and systematic errors acareful study about the suitability of the power control scheme iscarried out. 相似文献