全文获取类型
收费全文 | 98542篇 |
免费 | 2200篇 |
国内免费 | 538篇 |
专业分类
电工技术 | 1077篇 |
综合类 | 2382篇 |
化学工业 | 15484篇 |
金属工艺 | 5058篇 |
机械仪表 | 3581篇 |
建筑科学 | 2738篇 |
矿业工程 | 584篇 |
能源动力 | 2162篇 |
轻工业 | 5181篇 |
水利工程 | 1477篇 |
石油天然气 | 591篇 |
武器工业 | 5篇 |
无线电 | 10674篇 |
一般工业技术 | 18793篇 |
冶金工业 | 3122篇 |
原子能技术 | 395篇 |
自动化技术 | 27976篇 |
出版年
2024年 | 66篇 |
2023年 | 346篇 |
2022年 | 689篇 |
2021年 | 1050篇 |
2020年 | 866篇 |
2019年 | 1030篇 |
2018年 | 15298篇 |
2017年 | 14141篇 |
2016年 | 10798篇 |
2015年 | 1261篇 |
2014年 | 1256篇 |
2013年 | 1851篇 |
2012年 | 4071篇 |
2011年 | 10450篇 |
2010年 | 8966篇 |
2009年 | 6218篇 |
2008年 | 7239篇 |
2007年 | 8105篇 |
2006年 | 457篇 |
2005年 | 1432篇 |
2004年 | 1324篇 |
2003年 | 1336篇 |
2002年 | 674篇 |
2001年 | 186篇 |
2000年 | 268篇 |
1999年 | 130篇 |
1998年 | 150篇 |
1997年 | 87篇 |
1996年 | 117篇 |
1995年 | 70篇 |
1994年 | 57篇 |
1993年 | 67篇 |
1992年 | 56篇 |
1991年 | 71篇 |
1990年 | 48篇 |
1989年 | 32篇 |
1988年 | 53篇 |
1987年 | 38篇 |
1984年 | 41篇 |
1983年 | 34篇 |
1968年 | 43篇 |
1967年 | 36篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1959年 | 35篇 |
1958年 | 39篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts. 相似文献
43.
Research funding has been seen as one of the most important resource in the reward system of science. And usage of publications denotes an interesting perspective of user behavior in scientific communication. This study aims to address the relationship between funding and Usage Count, which is a new metrics item established on the platform of Web of Science. Full records of 300,010 articles published in 2013 were downloaded in October 2015, and divided into six disciplines, including information science library science, education educational research, economics, computer science, materials science, and chemistry. Seven indicators were proposed to measure the impact, including Funding rate, Citation per paper, Usage rate, Usage per paper, Citation difference, Usage difference, and Conversion rate. It concluded funding has impact on usage and citation, and funded papers attract more usage, but varying in different disciplines. Usage Count can be used in the extension of citation metrics but with limits. This study originally engages with usage metrics and detected that there is positive correlation between usage and funding. 相似文献
44.
In this paper, the presence of source stack and heterogeneous gate dielectric material in the structure of an n-channel tunnel FET (TFET) is investigated. 相似文献
45.
Recent increase in the number of digital photos in the content sharing and social networking websites has created an endless demand for techniques to analyze, navigate, and summarize these images. In this paper, we focus on image collection summarization. Earlier methods in image collection summarization consider representativeness and diversity criteria while recent ones also consider other criteria such as image quality, aesthetic or appeal. In this paper, we propose a multi-criteria context-sensitive approach for social image collection summarization. In the proposed method, two different sets of features are combined while each one looks at different criteria for image collection summarization: social attractiveness features and semantic features. The first feature set considers different aspects that make an image appealing such as image quality, aesthetic, and emotion to create attractiveness score for input images while the second one covers semantic content of images and assigns semantic score to them. We use social network infrastructure to identify attractiveness features and domain ontology for extracting ontology features. The final summarization is provided by integrating the attractiveness and semantic features of input images. The experimental results on a collection of human generated summaries on a set of Flickr images demonstrate the effectiveness of the proposed image collection summarization approach. 相似文献
46.
Syafikah Huda Paiman Mukhlis A Rahman Khairul Hamimah Abas Azian Abd Aziz Ahmad Fauzi Ismail Mohd Hafiz Dzarfan Othman Juhana Jaafar Mohammad Noorul Anam Mohd Norddin 《化学工程与技术》2019,42(6):1321-1329
Removal by absorptive ceramic membranes can simultaneously absorb and separate metal ions from water. Alumina/yttria‐stabilized zirconia (Al2O3/YSZ) hollow‐fiber membranes, fabricated using phase inversion and sintering process, were deposited with iron oxide by an in‐situ hydrothermal process. The results showed that α‐Fe2O3 was produced and incorporated across the membranes. A reduction in flux was recorded with the deposition of α‐Fe2O3. However, it improved the adsorption capacity for heavy metal adsorption. The adsorption‐separation test demonstrated that the optimized membrane is able to completely remove Pb(II) ions after two hours. 相似文献
47.
Mungra Dhara Agrawal Anjali Sharma Priyanka Tanwar Sudeep Obaidat Mohammad S. 《Multimedia Tools and Applications》2020,79(3-4):2285-2307
Multimedia Tools and Applications - Emotions are spontaneous feelings that are accompanied by fluctuations in facial muscles, which leads to facial expressions. Categorization of these facial... 相似文献
48.
Ha ABDEL MAKSOUD Mk MAHFOUZ Mi SOLIMAN Mohamed G ELHARRIF M ABBASS Ma EL-BADRY 《Biocell》2020,44(1):111-115
Pyrethroid esters are widely used as insecticides worldwide. In this study, we aimed to evaluate the harmful
effect of deltamethrin on the male reproductive system through the assessment of reproductive hormones, inflammatory
markers, and testicular function. To achieve our aim, eighty male 7-9-week-old, Wistar rats were taken, weighed, and
divided into four experimental groups. The first group was kept as a control group, and the other three groups were
given deltamethrin orally at different concentrations (0.87, 8.7, and 17.4 mg/kg body weight) for nine weeks. The results
indicated that deltamethrin administration associated with a significant decrease in reproductive hormones, especially
FSH, LH, and significant elevation in the interleukin 2 (IL2), interleukin 6 (IL6), histamine, and cortisol levels. Also, the
significance of inhibition of sperm motility and viability, decreased testis weights, sperm count, and fructose in semen
were noted. These findings clarify the harmful effect of deltamethrin on the male reproductive system by producing a
significant alteration in reproductive hormones, inflammatory markers as well as testicular function. 相似文献
49.
The physical mechanism of highly efficient photoluminescence (PL) emission from p-type silicon is described by a comparative study of the effectiveness of the etching parameters in an electrochemical anodization technique. Two series of porous silicon samples were prepared in a combination of anodization current and time, to maintain the total amount of anodic charge transfer constant. Photoluminescence studies show that irrespective of the amount of charge transfer, the samples prepared with comparatively higher current density show an efficient PL as well as stronger blueshift in the emission energy vis-à-vis the samples prepared for longer durations. An overall decrease in crystallite size, as estimated by Raman spectral analysis, was observed for both series of samples with the progress of charge transfer. Comparative analysis shows a marginal difference in crystallite size for both series of samples in the initial state of charge transfer, whereas major differences arise at higher values. This is explained with the formation of silicon suboxide on the porous surface at higher current density, leading to initiation of side wall reaction, and higher reduction rate in crystallite size as well as strong luminescence due to the carrier quantum confinement effect. 相似文献
50.
Sakizadeh Mohamad Mohamed Mohamed M. A. Klammler Harald 《Water Resources Management》2019,33(4):1425-1437
Water Resources Management - Overexploitation of groundwater in the Malayer Plain has resulted in a continuous decline of groundwater levels over recent years with associated risks to water... 相似文献