全文获取类型
收费全文 | 18086篇 |
免费 | 1260篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 104篇 |
综合类 | 12篇 |
化学工业 | 3502篇 |
金属工艺 | 304篇 |
机械仪表 | 335篇 |
建筑科学 | 511篇 |
矿业工程 | 40篇 |
能源动力 | 291篇 |
轻工业 | 3436篇 |
水利工程 | 217篇 |
石油天然气 | 68篇 |
武器工业 | 2篇 |
无线电 | 785篇 |
一般工业技术 | 2943篇 |
冶金工业 | 4416篇 |
原子能技术 | 71篇 |
自动化技术 | 2321篇 |
出版年
2024年 | 32篇 |
2023年 | 146篇 |
2022年 | 165篇 |
2021年 | 403篇 |
2020年 | 397篇 |
2019年 | 432篇 |
2018年 | 785篇 |
2017年 | 743篇 |
2016年 | 746篇 |
2015年 | 593篇 |
2014年 | 737篇 |
2013年 | 1445篇 |
2012年 | 1135篇 |
2011年 | 950篇 |
2010年 | 812篇 |
2009年 | 731篇 |
2008年 | 754篇 |
2007年 | 716篇 |
2006年 | 455篇 |
2005年 | 351篇 |
2004年 | 378篇 |
2003年 | 330篇 |
2002年 | 303篇 |
2001年 | 218篇 |
2000年 | 195篇 |
1999年 | 264篇 |
1998年 | 1464篇 |
1997年 | 946篇 |
1996年 | 590篇 |
1995年 | 305篇 |
1994年 | 245篇 |
1993年 | 286篇 |
1992年 | 93篇 |
1991年 | 83篇 |
1990年 | 76篇 |
1989年 | 77篇 |
1988年 | 77篇 |
1987年 | 63篇 |
1986年 | 65篇 |
1985年 | 82篇 |
1984年 | 49篇 |
1983年 | 39篇 |
1982年 | 54篇 |
1981年 | 65篇 |
1980年 | 53篇 |
1979年 | 25篇 |
1978年 | 25篇 |
1977年 | 98篇 |
1976年 | 191篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
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
14.
15.
16.
17.
Zhang Xi Wang Xianhai Zhao Hongke Ordóñez de Pablos Patricia Sun Yongqiang Xiong Hui 《Scientometrics》2019,119(3):1311-1344
Scientometrics - Altmetrics indices are increasingly applied to measure scholarly influence in recent years because they can reflect the influence of research outputs more timely comparing with... 相似文献
18.
Indium separation using ion exchange resins from acidic polymetallic and very diluted solutions are investigated. Since the selectivity of commercial ion exchange resins have proven to be too low for an effective separation from solutions with high content of other metals, Lewatit® TP 208 was impregnated with common extractants to enhance its properties. By resin impregnation with D2EHPA and Cyanex 272, not only the selective indium recovery was reached but also the resin capacity was increased approx. two times. The best loading and elution performance were shown by Cyanex 272-impregnated Lewatit® TP 208, increasing the indium purity in the eluate from 0.75 % to 85 %. 相似文献
19.
Andrés Mario Zervigón 《History of Photography》2019,43(2):130-143
For decades now, Douglas Crimp’s landmark 1980 essay ‘The Photographic Activity of Postmodernism’ has shaped our understanding of modernism’s aftermath, at least as it unfolded in North America and Western Europe. Less remembered, however, is the degree to which the procedures of disjunction, copying, appropriation, and outright theft that he highlighted were epitomised not just by contemporary photography, but by photomontage in particular. This article recovers the debates that led critics such as Crimp, Abigail Solomon-Godeau, Christopher Phillips, Benjamin Buchloh and others to turn to photomontage as one of their principal objects of concern in what became known as the postmodern critique of photography. Why was montage tasked to perform this critical function, particularly by people around the journal October who had not otherwise devoted the balance of their writing to photography’s history? The article suggests that these men and women, along with the contemporary artists they foregrounded, manifested what Mary Anne Doane has called a ‘desire for signification’, a reaction in the late 1970s against the mute theatricality of minimalist and conceptual art. Photomontage reintroduced representation to contemporary art and to the canon of art history. But unlike the reemerging illusionism in painting that also manifested this desire, montage guarded against an uncomplicated realism by highlighting and critiquing operations of representation in a manner that painting no longer could. 相似文献