全文获取类型
收费全文 | 66124篇 |
免费 | 6689篇 |
国内免费 | 3879篇 |
专业分类
电工技术 | 6646篇 |
技术理论 | 4篇 |
综合类 | 6010篇 |
化学工业 | 4699篇 |
金属工艺 | 2953篇 |
机械仪表 | 5737篇 |
建筑科学 | 12304篇 |
矿业工程 | 2641篇 |
能源动力 | 1915篇 |
轻工业 | 3098篇 |
水利工程 | 3461篇 |
石油天然气 | 4378篇 |
武器工业 | 1524篇 |
无线电 | 5036篇 |
一般工业技术 | 5605篇 |
冶金工业 | 2357篇 |
原子能技术 | 759篇 |
自动化技术 | 7565篇 |
出版年
2024年 | 236篇 |
2023年 | 739篇 |
2022年 | 1575篇 |
2021年 | 1891篇 |
2020年 | 2236篇 |
2019年 | 1691篇 |
2018年 | 1615篇 |
2017年 | 2214篇 |
2016年 | 2429篇 |
2015年 | 2641篇 |
2014年 | 4206篇 |
2013年 | 3796篇 |
2012年 | 5106篇 |
2011年 | 5325篇 |
2010年 | 3976篇 |
2009年 | 3990篇 |
2008年 | 3650篇 |
2007年 | 4548篇 |
2006年 | 4093篇 |
2005年 | 3634篇 |
2004年 | 3026篇 |
2003年 | 2468篇 |
2002年 | 2106篇 |
2001年 | 1794篇 |
2000年 | 1447篇 |
1999年 | 1158篇 |
1998年 | 913篇 |
1997年 | 706篇 |
1996年 | 717篇 |
1995年 | 576篇 |
1994年 | 431篇 |
1993年 | 317篇 |
1992年 | 266篇 |
1991年 | 167篇 |
1990年 | 160篇 |
1989年 | 121篇 |
1988年 | 78篇 |
1987年 | 56篇 |
1986年 | 45篇 |
1985年 | 25篇 |
1984年 | 24篇 |
1980年 | 64篇 |
1979年 | 48篇 |
1965年 | 26篇 |
1964年 | 34篇 |
1959年 | 32篇 |
1958年 | 23篇 |
1957年 | 24篇 |
1956年 | 32篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
171.
合成2,4-二叔丁基苯酚工业试验 总被引:2,自引:0,他引:2
以离子交换树脂为催化剂,苯酚和甲基叔丁基醚为原料合成2,4-二叔丁基苯酚(简称2,4酚),合成产物经过滤再经间歇真空精馏精制提纯,得到高纯度的2,4酚成品。成品精馏后釜中残液在酸性白土催化剂的作用下通过歧化反应生成对叔丁基苯酚,再经精馏提纯得到成品对叔丁基苯酚。通过工艺优化,使2,4酚、对叔丁基苯酚形成联产生产工艺,降低了生产原料消耗和成本。 相似文献
172.
为电机主绝缘VPI工艺选择合适的粉云母带,对几种真空压力浸渍(VPI)用云母带进行了试验研究,分析了选型原则,同时对比了几种粉云母带的性能。将它们应用于模拟线棒中,线棒的试验数据表明:选出的两种云母带的配合可获得优异的性能,达到优等品标准水平。再将少胶云母带应用于电机整机试验,试验结果表明达到了减薄绝缘、降低温升、延缓绝缘老化、提高电机使用寿命的目的。 相似文献
173.
陈训浩 《冶金标准化与质量》2003,41(1):5-8
从碳素结构钢热轧钢带各向异性的事实出发 ,阐述不同试样位向导致同一钢带不同的拉伸性能 ,因而影响钢带合格与否的判定。在全面考虑钢带和焊管标准的基础上 ,提出解决钢带判定的两种方法。同时 ,还对标准中存在的缺点作了说明 ,提出改进意见 ,供标准修订时参考。 相似文献
174.
The aim of this study was to examine the reliability and validity of a French version of the Revised Children's Manifest Anxiety Scale (RCMAS). A sample of 2,666 school-age French-Canadian children completed the questionnaire. With regard to factor structure, the 5-factor model found in U.S. normative samples was confirmed. The internal consistency of the 5 scales and of the 2 global scales was good to excellent. Test-retest reliabilities after a 6-month period were also similar to those of the original version. Finally, the concurrent validity, assessed by a correlation with the State-Trait Anxiety Inventory for Children, was also found to be good. Results of the present study show that the French version of the RCMAS is a good instrument to assess anxiety in children. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
175.
This article reports research intended to assess and extend a recent theory of peer responses to low-performing team members (J. A. LePine & L. Van Dyne, 2001a). An instrument that assesses 4 types of peer responses to low performers (compensating for, training, motivating, and rejecting) was developed and then cross-validated in a subsequent study. Results of the study supported the validity of the peer responses measure and were generally consistent with the attributional theory of peer responses. Low-performer characteristics influenced the peer responses. These effects were mediated in part by peer attributions, affect, and cognitions, which explained variance in the peer responses over and above the variance explained by respondents' personality characteristics (i.e., The Big Five). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
176.
2-巯基苯并噻唑衍生物摩擦学性能的研究 总被引:4,自引:0,他引:4
合成了S—(1—(2—苯并噻唑基巯基)—2—羟基)—丙基N,N—二烷基二硫代氨基甲酸酯和S—(1—(2—苯并噻唑基巯基)—2—乙酰基)—丙基N,N—二烷基二硫代氨基甲酸酯两种化合物。运用IR、MS、HNMR和元素分析等分析方法对其结构进行表征。用四球试验、HQ—l环块试验分别考察了其对润滑油的极压承载能力及抗磨减摩性能的影响。结果表明:在350SN中性油中添加所合成的化合物后可以显著降低四球长磨后磨斑直径、有效地降低摩擦副之间的摩擦系数,拥有优良的摩擦学性能。 相似文献
177.
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
178.
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
179.
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
180.
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