全文获取类型
收费全文 | 110950篇 |
免费 | 11366篇 |
国内免费 | 5926篇 |
专业分类
电工技术 | 8464篇 |
技术理论 | 3篇 |
综合类 | 9811篇 |
化学工业 | 15211篇 |
金属工艺 | 4583篇 |
机械仪表 | 6842篇 |
建筑科学 | 16506篇 |
矿业工程 | 3393篇 |
能源动力 | 2428篇 |
轻工业 | 10617篇 |
水利工程 | 4010篇 |
石油天然气 | 4900篇 |
武器工业 | 1713篇 |
无线电 | 14674篇 |
一般工业技术 | 11686篇 |
冶金工业 | 3024篇 |
原子能技术 | 997篇 |
自动化技术 | 9380篇 |
出版年
2024年 | 428篇 |
2023年 | 1405篇 |
2022年 | 2742篇 |
2021年 | 3173篇 |
2020年 | 3626篇 |
2019年 | 2932篇 |
2018年 | 2813篇 |
2017年 | 3935篇 |
2016年 | 4084篇 |
2015年 | 4431篇 |
2014年 | 6607篇 |
2013年 | 6454篇 |
2012年 | 8255篇 |
2011年 | 8304篇 |
2010年 | 6388篇 |
2009年 | 6517篇 |
2008年 | 5952篇 |
2007年 | 7574篇 |
2006年 | 7144篇 |
2005年 | 6180篇 |
2004年 | 5081篇 |
2003年 | 4268篇 |
2002年 | 3667篇 |
2001年 | 3192篇 |
2000年 | 2550篇 |
1999年 | 2012篇 |
1998年 | 1582篇 |
1997年 | 1257篇 |
1996年 | 1130篇 |
1995年 | 957篇 |
1994年 | 801篇 |
1993年 | 590篇 |
1992年 | 496篇 |
1991年 | 355篇 |
1990年 | 283篇 |
1989年 | 207篇 |
1988年 | 126篇 |
1987年 | 80篇 |
1986年 | 54篇 |
1985年 | 40篇 |
1984年 | 35篇 |
1981年 | 26篇 |
1980年 | 76篇 |
1979年 | 52篇 |
1965年 | 27篇 |
1964年 | 36篇 |
1960年 | 23篇 |
1959年 | 35篇 |
1956年 | 30篇 |
1955年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
采用优质石灰石取代质量差的白灰 ,进行了单渣电弧炉熔炼。结果表明 ,钢水成本降低 ,钢水质量提高 ,取得了良好的效果。 相似文献
82.
在采用液氮制冷的低气压试验箱的设计中,用常规工程设计方法计算的降温过程冷负荷过大,从而导致真空系统设计容量过大。本文采用分布参数模型对试验箱低气压条件下降温过程的冷负荷进行了精确仿真模拟,以此作为真空系统容量设计的基础,减小了设计规模,取得了良好的效果。 相似文献
83.
Reviews the book, The achievement test desk reference: A guide to learning disability identification, second edition by Dawn P. Flanagan, Samuel O. Ortiz, Vincent C. Alfonso, and Jennifer T. Mascolo (2006). The Second Edition of the Achievement test desk reference comes only four years after its first edition. Its content echoes the first edition, with the chapters now re-organized and updated. However, this edition is also timely; its significant contributions are its theoretical and practical model for defining and assessing learning disabilities (LD) and its update of practical information for interpreting many of the new standardized achievement tests. The goal for this edition was to provide an integrated and systematic framework for achievement testing within the framework of the Cattell-Horn-Carroll (CHC) theory of human cognitive abilities and the Response to Intervention (RTI) movement. Part 1 of provides an update of the theories, definitions, assessment, interpretation, and identification of LD. Part 2 describes and reviews the psychometric, theoretical, and qualitative features of achievement tests published between 1996 and 2006 and normed on people from the United States. Part 3 provides a comprehensive, step-by-step process for assessing learning disabilities under the Individuals with Disabilities Education Improvement Act (IDEA 2004). This volume guides practitioners to choose the best achievement tests to use. It shows how to get the most efficient and effective evaluations of students' academic skills that could account for their difficulties and possible learning disabilities. This book will be essential reference material for effective LD assessments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
本文针对美孚油回收液与兰炼8#油混合利用进行可行性实验研究,经过重度、粘度、可燃性等方面的实验研究,表明美孚油回收液与兰炼8#油混合可以用在电动轮上并且获得良好的效果。 相似文献
85.
Cognitive Operations in the Generation Effect on a Recall Test: Role of Aging and Divided Attention.
Generation effect (generated words are better memorized than read words) of anagrams, rhymes, and associates of target words was examined in young, elderly, and very old subjects. Experiments 1 and 2 showed that only young subjects benefit from the generation effect in a free-recall test when the rule is of a phonological nature. Experiments 3, 4, and 5 showed that the generation effect of rhymes was due to a resources-dependent self-initiated process. Experiments 4 and 5 showed that in a divided-attention situation, generation effect of rhymes is not significant in young subjects, but that the generation effect of semantic associates remains significant for both groups (Experiment 5). The results are discussed within the environmental support framework and the transfer-appropriate processing framework. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
86.
There is a growing trend of research in neuropsychological assessment in Asia: The mean number of published studies increased from 1.8 in the 1980s to 16.0 in 2 recent years. About 40% of the studies reviewed concerned test development or adaptation, with the latter greatly outnumbering the former. To facilitate the test selection for clinical use, 36 clinical measures were evaluated based on some statistical criteria. The results showed that only 8 neuropsychological tests (5 Chinese. 2 Korean, and 1 Japanese) met the criteria. Given that Asian and Western populations differ on certain cognitive processes, future development of neuropsychological assessment measures in Asia should move from the adaptation of Western tests toward the construction of original tests with better ecological validity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
中国光纤通信技术的研究、应用和发展 总被引:1,自引:0,他引:1
主要从光纤光缆、光器件与组件、光传输设备与系统、光网络建设等方面论述光纤通信技术在我国的研究、应用发展历程,并对我国光纤通信技术的未来发展进行展望。 相似文献
88.
89.
光纤接入一直是多年来人们不断追求的梦想和探索的技术方向,但由于成本、技术、需求等方面的障碍,至今还没有得到大规模推广与发展。然而,这种局面最近有了很大的改观,出现可迅速发展的势头。主要是因为一些国家政策的扶持、运营商竞争的需要、对收入的追求,以及设备本身价格的下降,光纤接入技术由于各种原因,至今尚未在全球广泛应用,但在日本、美国、瑞典和意大利等国都获得了较多的应用。在中国,光纤接入也有了良好的开端,将在大城市广泛应用,并逐渐推广到全国。 相似文献
90.
Optical absorption and photoluminescence of Ca3(VO4)2 single crystal grown by a floating-zone technique and containing Nd3+ ions were investigated. High absorption coefficients and broadening of most absorption bands are present at 300 K, while substructures in some of the same bands can be evidenced at 12 K. Most features of measured spectra are characteristic of random occupation of more than a single Ca2+ site by the Nd3+ ion and of distortions provoked by different charge compensation mechanisms involving oxygen vacancies promotion in the crystal lattice. Nd3+ optical properties were studied by using the Judd-Ofelt theory to calculate the spectral parameters relevant for laser applications. 相似文献