全文获取类型
收费全文 | 1663028篇 |
免费 | 27115篇 |
国内免费 | 7223篇 |
专业分类
电工技术 | 35241篇 |
综合类 | 6561篇 |
化学工业 | 282483篇 |
金属工艺 | 66779篇 |
机械仪表 | 47130篇 |
建筑科学 | 49897篇 |
矿业工程 | 11758篇 |
能源动力 | 51329篇 |
轻工业 | 132003篇 |
水利工程 | 16775篇 |
石油天然气 | 38117篇 |
武器工业 | 153篇 |
无线电 | 201677篇 |
一般工业技术 | 308405篇 |
冶金工业 | 235648篇 |
原子能技术 | 34650篇 |
自动化技术 | 178760篇 |
出版年
2021年 | 16483篇 |
2020年 | 12628篇 |
2019年 | 15408篇 |
2018年 | 19401篇 |
2017年 | 18864篇 |
2016年 | 23821篇 |
2015年 | 18353篇 |
2014年 | 29779篇 |
2013年 | 90078篇 |
2012年 | 40207篇 |
2011年 | 55449篇 |
2010年 | 46807篇 |
2009年 | 54202篇 |
2008年 | 50689篇 |
2007年 | 48312篇 |
2006年 | 48229篇 |
2005年 | 43402篇 |
2004年 | 44942篇 |
2003年 | 44500篇 |
2002年 | 42976篇 |
2001年 | 40287篇 |
2000年 | 38303篇 |
1999年 | 38693篇 |
1998年 | 67889篇 |
1997年 | 52963篇 |
1996年 | 44344篇 |
1995年 | 36117篇 |
1994年 | 33178篇 |
1993年 | 33129篇 |
1992年 | 27418篇 |
1991年 | 24785篇 |
1990年 | 24943篇 |
1989年 | 24043篇 |
1988年 | 22617篇 |
1987年 | 20755篇 |
1986年 | 20124篇 |
1985年 | 23401篇 |
1984年 | 22937篇 |
1983年 | 20934篇 |
1982年 | 19755篇 |
1981年 | 19999篇 |
1980年 | 18641篇 |
1979年 | 18938篇 |
1978年 | 18209篇 |
1977年 | 19169篇 |
1976年 | 22108篇 |
1975年 | 16346篇 |
1974年 | 15752篇 |
1973年 | 15894篇 |
1972年 | 13340篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
106.
107.
108.
ABSTRACTThis paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR . In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs. 相似文献
109.
Konstantinos Spyrou Matteo Calvaresi Evmorfia K. Diamanti Theodoros Tsoufis Dimitrios Gournis Petra Rudolf Francesco Zerbetto 《Advanced functional materials》2015,25(2):263-269
Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”. 相似文献
110.