全文获取类型
收费全文 | 2208篇 |
免费 | 187篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 11篇 |
综合类 | 3篇 |
化学工业 | 837篇 |
金属工艺 | 25篇 |
机械仪表 | 42篇 |
建筑科学 | 65篇 |
矿业工程 | 6篇 |
能源动力 | 75篇 |
轻工业 | 482篇 |
水利工程 | 21篇 |
石油天然气 | 5篇 |
无线电 | 114篇 |
一般工业技术 | 320篇 |
冶金工业 | 115篇 |
原子能技术 | 5篇 |
自动化技术 | 270篇 |
出版年
2024年 | 3篇 |
2023年 | 36篇 |
2022年 | 55篇 |
2021年 | 226篇 |
2020年 | 76篇 |
2019年 | 99篇 |
2018年 | 83篇 |
2017年 | 83篇 |
2016年 | 106篇 |
2015年 | 89篇 |
2014年 | 96篇 |
2013年 | 176篇 |
2012年 | 148篇 |
2011年 | 185篇 |
2010年 | 161篇 |
2009年 | 121篇 |
2008年 | 104篇 |
2007年 | 86篇 |
2006年 | 77篇 |
2005年 | 54篇 |
2004年 | 38篇 |
2003年 | 41篇 |
2002年 | 41篇 |
2001年 | 20篇 |
2000年 | 9篇 |
1999年 | 22篇 |
1998年 | 31篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2396条查询结果,搜索用时 31 毫秒
61.
Martins Silvia S.; Mazzotti Guido; Chilcoat Howard D. 《Canadian Metallurgical Quarterly》2005,13(3):244
This study aims to estimate changes in the prevalence of ecstasy use over time, analyze the overlap of ecstasy use and other drug use, and compare other drug use in ecstasy versus marijuana users. The authors hypothesized that ecstasy users early in the "epidemic" would be polydrug users and that associations between ecstasy and other drug use would diminish as the prevalence of ecstasy use increased. Data were drawn from public use data files from the 1995, 1997, 1999, and 2001 National Household Survey on Drug Abuse. Ecstasy use increased in the U.S. population and the prevalence was greater in younger age groups. Ecstasy users were likely to use a variety of other drugs; however, association of ecstasy use with other drug use was strongest early in the "epidemic," diminishing as the number of new users increased. Later, more drug-naive adolescents and young adults began experimenting with ecstasy. These results can orient prevention strategies that target ecstasy users. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
62.
63.
High-quality industrial processes, characterized by a low fraction of non-conforming items, require paying special attention to the statistical control methods employed since traditional Shewhart's control charts are no longer suitable. In this article, CCC-r charts are considered based on the cumulative count of conforming items inspected until r non-conforming items are observed. However, even though these charts have shown to be useful for high-quality processes, they are characterized by a biased average run length (ARL). In order to help engineers interested in this control methodology to select the best option, a computational study of statistical validation was performed to compare the two most outstanding procedures for the cases r = 2, 3, and 4. The performance was evaluated based on the ARL under control. The application of the CCC-r chart to a real process is shown with data from an automobile parts plant. Finally, analysis and discussion of the results are presented. 相似文献
64.
Silvia Knobloch‐Westerwick 《The Journal of communication》2012,62(4):628-642
Right before the 2008 U.S. presidential election, this 2‐session online field study examined consequences of selective exposure to political messages on accessibility of attitudes and of partisanship. In the first session, participants indicated attitudes toward political issues and their partisanship, which allowed measuring accessibility of attitudes and of partisanship. In the second session, participants browsed articles. Four issues were covered by 8 articles, with 2 articles featuring opposing perspectives. Selective exposure was unobtrusively logged. Finally, participants completed measures for attitudes and partisanship again. Selective exposure to attitude‐consistent articles was linked to greater attitude accessibility. The indirect impact of selective exposure on partisanship accessibility through attitude accessibility was significant. 相似文献
65.
David González G. Mario García-Lozano Silvia Ruiz Dong Seop Lee 《Wireless Networks》2014,20(6):1369-1386
The explosive growth of cellular networks makes their deployment and maintenance more and more complex, time consuming, and expensive. Self-Organizing Networks have been recognized as a promising way to alleviate this problem by minimizing human intervention in such processes. This paper introduces a novel multiobjective framework, based on evolutionary optimization, aiming at improving network performance and users Quality of Service. By tuning the transmitted power at each cell, average intercell interference levels are minimized. The design of the proposed scheme is feasible for distributed implementations in Long Term Evolution (LTE) and LTE-Advanced networks and its operation is compatible with current specifications. The framework is able to provide effective network-specific optimization and obtained results show that gains in terms of network capacity and cell edge performance are 5 and 10 %, respectively. Energy savings always accompanied such enhancements with reductions up to 35 %. 相似文献
66.
67.
68.
Joao Sarraipa Catarina Marques-Lucena Silvia Baldiris Ramón Fabregat Silvana Aciar 《Journal of Intelligent Manufacturing》2016,27(1):83-99
Nowadays, it is commonly known that information systems need an agile capability of handling knowledge. To accomplish this, systems have to have a formal knowledge representation ability supported by specific and advanced reasoning features. This research work proposes a knowledge management approach with the purpose to gather, model and consume community knowledge for specific recommendation commitments. Such approach is accomplished by a semantic lexicon alignment between the various community knowledge assets, to facilitate collaborations establishment between people and systems in an interoperable fashion. Thus, a knowledge base supported by a thesaurus able to represent all the metadata needed to represent and characterize the various community stakeholders’ resources is proposed. The thesaurus represents the lexicon in the domain, which in the ALTER-NATIVA systems is mostly used to support the various e-Learning elements (e.g. courses) and users categorization, sustained by synchronization features to facilitate a constant update of its information. A set of services designed to recommend specific resources in relation to a determined profile of user is provided. Additionally, a discussion about how the ALTER-NATIVA knowledge management approach can be applied to industrial environments is presented. 相似文献
69.
Silvia Franco Elena Buratti Valentina Nigro Emanuela Zaccarelli Barbara Ruzicka Roberta Angelini 《International journal of molecular sciences》2021,22(8)
The phase behaviour of soft colloids has attracted great attention due to the large variety of new phenomenologies emerging from their ability to pack at very high volume fractions. Here we report rheological measurements on interpenetrated polymer network microgels composed of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylic acid (PAAc) at fixed PAAc content as a function of weight concentration. We found three different rheological regimes characteristic of three different states: a Newtonian shear-thinning fluid, an attractive glass characterized by a yield stress, and a jamming state. We discuss the possible molecular mechanisms driving the formation of these states. 相似文献
70.
We present a model for anchoring categorical conceptual information which originates from physical perception and the web. The model is an extension of the anchoring framework which is used to create and maintain over time semantically grounded sensor information. Using the augmented anchoring framework that employs complex symbolic knowledge from a commonsense knowledge base, we attempt to ground and integrate symbolic and perceptual data that are available on the web. We introduce conceptual anchors which are representations of general, concrete conceptual terms. We show in an example scenario how conceptual anchors can be coherently integrated with perceptual anchors and commonsense information for the acquisition of novel concepts. 相似文献