全文获取类型
收费全文 | 105632篇 |
免费 | 2791篇 |
国内免费 | 1177篇 |
专业分类
电工技术 | 1907篇 |
技术理论 | 3篇 |
综合类 | 3655篇 |
化学工业 | 15326篇 |
金属工艺 | 5892篇 |
机械仪表 | 4374篇 |
建筑科学 | 3891篇 |
矿业工程 | 1046篇 |
能源动力 | 1724篇 |
轻工业 | 5167篇 |
水利工程 | 1634篇 |
石油天然气 | 1610篇 |
武器工业 | 172篇 |
无线电 | 11557篇 |
一般工业技术 | 19397篇 |
冶金工业 | 3831篇 |
原子能技术 | 566篇 |
自动化技术 | 27848篇 |
出版年
2024年 | 85篇 |
2023年 | 325篇 |
2022年 | 536篇 |
2021年 | 706篇 |
2020年 | 579篇 |
2019年 | 508篇 |
2018年 | 14905篇 |
2017年 | 13948篇 |
2016年 | 10463篇 |
2015年 | 1374篇 |
2014年 | 1173篇 |
2013年 | 1377篇 |
2012年 | 4394篇 |
2011年 | 10694篇 |
2010年 | 9413篇 |
2009年 | 6626篇 |
2008年 | 7939篇 |
2007年 | 8871篇 |
2006年 | 1353篇 |
2005年 | 2354篇 |
2004年 | 1855篇 |
2003年 | 1862篇 |
2002年 | 1176篇 |
2001年 | 662篇 |
2000年 | 899篇 |
1999年 | 844篇 |
1998年 | 719篇 |
1997年 | 625篇 |
1996年 | 570篇 |
1995年 | 489篇 |
1994年 | 374篇 |
1993年 | 274篇 |
1992年 | 238篇 |
1991年 | 198篇 |
1990年 | 141篇 |
1989年 | 124篇 |
1988年 | 104篇 |
1987年 | 44篇 |
1986年 | 50篇 |
1985年 | 44篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1959年 | 36篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
22.
23.
24.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献
25.
26.
27.
High‐performance thermosets with tailored properties derived from methacrylated eugenol and epoxy‐based vinyl ester 下载免费PDF全文
Yuehong Zhang Yuzhan Li Vijay Kumar Thakur Zhenhua Gao Jiyou Gu Michael R Kessler 《Polymer International》2018,67(5):544-549
A renewable chemical, eugenol, is methacrylated to produce methacrylated eugenol (ME) employing the Steglich esterification reaction without any solvent. The resulting ME is used as a low‐viscosity co‐monomer to replace styrene in a commercial epoxy‐based vinyl ester resin (VE). The volatility and viscosity of ME and styrene are compared. The effect of ME loading and temperature on the viscosity of the VE–ME resin is investigated. Moreover, the thermomechanical properties, curing extent and thermal stability of the fully cured VE–ME thermosets are systematically examined. The results indicate that ME is a monomer with low volatility and low viscosity, and therefore the incorporation of ME monomer in VE resins allows significant reduction of viscosity. Moreover, the viscosity of the VE–ME resin can be tailored by adjusting the ME loadings and processing temperature to meet commercial liquid molding technology requirements. The glass transition temperatures of VE–ME thermosets range from 139 to 199 °C. In addition, more than 95% of the monomer is incorporated and fixed in the crosslinked network structure of VE–ME thermosets. Overall, the developed ME monomer exhibits promising potential for replacing styrene as an effective low‐viscosity co‐monomer. The VE–ME resins show great advantages for use in polymer matrices for high‐performance fiber‐reinforced composites. This work is of great significance to the vinyl ester industry by providing detailed experimental support. © 2018 Society of Chemical Industry 相似文献
28.
29.
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
30.
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