全文获取类型
收费全文 | 53892篇 |
免费 | 5405篇 |
国内免费 | 2528篇 |
专业分类
电工技术 | 3507篇 |
技术理论 | 1篇 |
综合类 | 4176篇 |
化学工业 | 8259篇 |
金属工艺 | 2057篇 |
机械仪表 | 3485篇 |
建筑科学 | 8001篇 |
矿业工程 | 1098篇 |
能源动力 | 3597篇 |
轻工业 | 5721篇 |
水利工程 | 698篇 |
石油天然气 | 2825篇 |
武器工业 | 692篇 |
无线电 | 3343篇 |
一般工业技术 | 5249篇 |
冶金工业 | 2469篇 |
原子能技术 | 345篇 |
自动化技术 | 6302篇 |
出版年
2024年 | 371篇 |
2023年 | 1078篇 |
2022年 | 2038篇 |
2021年 | 2427篇 |
2020年 | 2409篇 |
2019年 | 2007篇 |
2018年 | 1923篇 |
2017年 | 2165篇 |
2016年 | 2314篇 |
2015年 | 2323篇 |
2014年 | 3539篇 |
2013年 | 3404篇 |
2012年 | 4016篇 |
2011年 | 4051篇 |
2010年 | 3004篇 |
2009年 | 3078篇 |
2008年 | 2658篇 |
2007年 | 3392篇 |
2006年 | 2853篇 |
2005年 | 2434篇 |
2004年 | 1953篇 |
2003年 | 1644篇 |
2002年 | 1318篇 |
2001年 | 1124篇 |
2000年 | 851篇 |
1999年 | 670篇 |
1998年 | 455篇 |
1997年 | 373篇 |
1996年 | 364篇 |
1995年 | 252篇 |
1994年 | 198篇 |
1993年 | 152篇 |
1992年 | 121篇 |
1991年 | 111篇 |
1990年 | 80篇 |
1989年 | 67篇 |
1988年 | 48篇 |
1987年 | 44篇 |
1986年 | 20篇 |
1985年 | 35篇 |
1984年 | 46篇 |
1983年 | 31篇 |
1982年 | 27篇 |
1980年 | 47篇 |
1965年 | 19篇 |
1964年 | 28篇 |
1963年 | 26篇 |
1961年 | 22篇 |
1956年 | 18篇 |
1955年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Michael E. Becker 《Journal of the Society for Information Display》2006,14(11):1003-1017
Abstract— In this paper, methods and instruments for measurement and evaluation of reflection characteristics are reviewed as needed for research and development of electronic displays and for material and surface modeling with ray‐tracing and rendering software packages. Contrast under ambient illumination and recognizability under daylight illumination are prime development targets in the electronic‐display field, while computation and synthesis of realistic scenes and objects are pushing the need for physical data in computer graphics applications. Three categories of instruments are available for detailed reflection analysis. They are based on (1) gonioscopic (mechanical) and conoscopic (optical) directional scanning, (2) imaging approaches, and (3) on arrangements with variable source or receiver aperture. The capabilities, advantages, and limitations of these methods are introduced and discussed in order to facilitate appropriate selection of methods and instruments. For illustration purposes we present typical results obtained from commercial electronic display screens. A basis for continued widespread implementation and standardization of reflection metrology as required for objective rating and comparison of electronic‐display screen performance under ambient illumination is provided. 相似文献
82.
添加剂组成对通用内燃机油性能的影响 总被引:1,自引:0,他引:1
通过相关模拟试验,分析研究了添加剂组成对通用内燃机油的抗磨性能,抗氧化性能以及清净分散性能的影响。 相似文献
83.
84.
The physical gestures that operate music instruments are responsible for the qualities of the sound being produced in a performance.
Gestural information is thereby crucial for a model of music performance, paired with a model of sound synthesis where this
information is applied. The highly constrained nature of performers gestures makes this task suitable to be modeled via a
constraint-based approach, coupled with a strategy aimed at maximizing the gestural comfort of performers. We illustrate the
problem representation, the search strategy and a validation of the model against human performance. 相似文献
85.
86.
本文提出一种与现有以太网兼容的综合话音/数据协议.描述了协议模型及实现方法.并用PASCAL语言在IBM-PC机上模拟研究了该协议的性能.模拟结果表明,该协议能满足话音的实时要求,性能良好,且数据传输性能没有明显下降.协议克服了以太网传输话音延迟不确定的缺点. 相似文献
87.
目前采用的视频流调度算法,没有充分利用补丁流满足服务率高而占用系统资源少的优势,系统效率较低.为了提高效率,提出了一种基于MFQ的补丁优先算法,并给出了该算法的系统流程。通过对实验结果的比较,该算法在用户请求撤销率、节目调度不公平性和用户等待时间方面有明显的优越性. 相似文献
88.
介绍了PHS网呼入成功率和短消息流程,依据短消息模型和性能统计结果分析了群发短信对PHS网呼入成功率的影响,并建议选择合理的时间进行短消息群发以减少对网络负荷的影响。 相似文献
89.
Stereotype threat research has demonstrated that stereotypes can harm student performance in the face of public evaluation by peers or an experimenter. The current study examined whether stereotypes can also threaten in private settings. Female students completed a math test in 3-person groups, which consisted of either 2 other women (same gender) or 2 men (minority). In addition, students either believed their performance would be broadcasted to their peers (public) or not (private). Results revealed that minority students performed worse than same-gender students in both public and private environments. This finding supports the concept of threatening intellectual environments and shows how far reaching the effects of stereotypes can be. The authors discuss these findings in relation to research on tokenism and to stereotype threat and its educational implications. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
90.
Injun Lee Taeseong Jung Junggi Kim Suho Ro Chulsu Kim Yeji Lee Youngmi Kim Juhyun Lee Misook Kang 《Journal of Industrial and Engineering Chemistry》2008,14(6):869-873
This study focuses on the relationship between photo-catalytic performance and optical property over Si-incorporated TiO2. The Si-incorporated TiO2 particles exhibited a pure structure of anatase having a particle size of less than 20 nm and surface area of more than 190 m2/g. The absorbance did not shift to a higher wavelength in spite of the incorporation of the Si ions, but the intensity of the photoluminescence (PL) curve was the smallest in the case of the 2.0 mol% Si-TiO2, which was related to the recombination between the excited electrons and holes. Based on these results, the photodecomposition of methyl orange in the liquid reaction was enhanced over the 2.0 mol% Si-incorporated TiO2 compared with that over pure TiO2: Methyl orange at 10.0 ppm was completely decomposed after 100 min when 1.0 g of the 2.0 mol% Si-incorporated TiO2 was used. 相似文献