全文获取类型
收费全文 | 288532篇 |
免费 | 23244篇 |
国内免费 | 12221篇 |
专业分类
电工技术 | 19168篇 |
技术理论 | 45篇 |
综合类 | 30167篇 |
化学工业 | 29711篇 |
金属工艺 | 11518篇 |
机械仪表 | 14906篇 |
建筑科学 | 42815篇 |
矿业工程 | 15624篇 |
能源动力 | 9878篇 |
轻工业 | 18411篇 |
水利工程 | 14145篇 |
石油天然气 | 13359篇 |
武器工业 | 3487篇 |
无线电 | 19619篇 |
一般工业技术 | 20000篇 |
冶金工业 | 16333篇 |
原子能技术 | 2077篇 |
自动化技术 | 42734篇 |
出版年
2024年 | 1122篇 |
2023年 | 3368篇 |
2022年 | 6427篇 |
2021年 | 8522篇 |
2020年 | 8446篇 |
2019年 | 6284篇 |
2018年 | 5924篇 |
2017年 | 7635篇 |
2016年 | 9255篇 |
2015年 | 10061篇 |
2014年 | 20402篇 |
2013年 | 17520篇 |
2012年 | 20597篇 |
2011年 | 22726篇 |
2010年 | 16934篇 |
2009年 | 17506篇 |
2008年 | 16387篇 |
2007年 | 20042篇 |
2006年 | 17949篇 |
2005年 | 15637篇 |
2004年 | 13185篇 |
2003年 | 11548篇 |
2002年 | 9360篇 |
2001年 | 7528篇 |
2000年 | 6335篇 |
1999年 | 4916篇 |
1998年 | 3436篇 |
1997年 | 2945篇 |
1996年 | 2391篇 |
1995年 | 2017篇 |
1994年 | 1644篇 |
1993年 | 1187篇 |
1992年 | 932篇 |
1991年 | 673篇 |
1990年 | 547篇 |
1989年 | 542篇 |
1988年 | 326篇 |
1987年 | 225篇 |
1986年 | 231篇 |
1985年 | 263篇 |
1984年 | 214篇 |
1983年 | 187篇 |
1982年 | 88篇 |
1981年 | 93篇 |
1980年 | 89篇 |
1979年 | 51篇 |
1978年 | 27篇 |
1977年 | 36篇 |
1975年 | 22篇 |
1959年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
陈继初 《湖南冶金职业技术学院学报》2003,(4)
会计政策选择类型在理论上大体可分为机会主义型和效率(或有效契约)型。会计政策选择具有效率性,但也为经理人员的机会主义行为打开了大门。在我国,由于企业缺乏一系列有效的激励约束机制,会计政策选择的机会主义仍然严重。为此,必须建立适合我国企业有效的激励约束机制。 相似文献
132.
介绍了油库油料计量中,在油品高度、油品温度和油品密度测量中存在的问题及应遵循的操作规范和注意事项。 相似文献
133.
134.
Christos Bouras Agisilaos Konidaris 《International Journal of Communication Systems》2005,18(2):119-142
Redundant data transfers over the Web, can be mainly attributed to the repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken down to fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process, we propose solutions for dealing with redundant data transfers. This paper has been based on our previous work on ‘Web Components’ but also on related work by other researchers. It utilises a proxy based, client/server architecture, and imposes changes to the algorithms executed on the Proxy server and on clients. We show that our proposed solution can considerably reduce the amount of redundant data transferred on the Web. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
135.
叙述了目前加油站在实行按任意温度下的体积交接,由于未考虑油品体积随温度、压力、密度的变化,出现了零售损耗很大的问题。建议加油站在现阶段采用“准标准体积”交接;在由体积转换为质量计算加油站损溢时,使用油库当月发出的平均密度;当财会核销损溢时,不使用盘存的体积和固定密度进行计算的方法,而使用实际盘点的质量数,以真实反映加油站的当期损溢。 相似文献
136.
137.
建立垂直管吸收器管内泡式吸收过程中传热传质的数学物理模型,对其泡式吸收过程进行数值研究,获得泡式吸收方式的一些传热传质特性,为吸收器的优化设计提供一定理论指导。 相似文献
138.
Central to cost-based competition is the capability to accurately predict the cost of delivering a project. Most literature on cost estimation focuses on specific estimation methods as generic techniques and little attention has been paid to the unique requirements at each project stage. This note attempts to identify the critical factors for effective estimation at various stages of typical construction projects. Drawing from organization control theory and cost estimating literature, this note develops a theoretical framework that identifies the critical factors for effective cost estimation during each project phase of a conventional construction project. The underlying logic is that as a cost estimating effort progresses, both task programmability and output measurability improve. As a result, control effort will shift from input-oriented control to a combination of output and behavior control. 相似文献
139.
Comments on the article "A house divided? The psychology of red and blue America" by D. C. Seyle and M. L. Newman (see record 2006-11202-001). Seyle and Newman concluded that the red and blue metaphor is inaccurate and proposed a purple America strategy to better convey that the majority of people do not align themselves with political extremes. There is interdisciplinary agreement on this. Although not cited by Seyle and Newman, the findings by Professor Fiorina of Stanford University were reported by the APA Monitor on Psychology in its coverage of the 2005 APA State Leadership Conference (Murray Law, 2005). In contrast to their social psychological analysis, Seyle and Newman were incorrect in concluding that "[a]s psychologists, we are not in a position to change either the elements of the American political system that may spur this conflict or even the decisions made by pundits, politicians, and reporters about the terms they choose to use in political discussion" (p. 579). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
140.
Hong Long Chen 《Canadian Metallurgical Quarterly》2007,23(4):171-181
The difficulty in applying the standard curve (S-curve) and cost-schedule integration (CSI) techniques for company-level cost flow forecasting in a project-based industry is the prerequisite of forecasting future unknown individual projects and contract classifications. By analyzing cost flows at the company level through a pool of macroeconomic and internal financial data, this paper proposes an innovative approach to firm-specific model estimation. First, a series of data transformations introduce linear relationships between cost, macroeconomic, and internal financial variables. Second, multivariate regression analysis is employed for initial model building. Third, for the purposes of model restructuring, a subsequent application of Yule–Walker estimates and incomplete principal component analysis is used. This paper uses a sample of four project-based construction firms to demonstrate model performance. Using this methodology, mean absolute percentage error (MAPE) values of the forecasting models range from 0.27 to 0.60%. As such, the transformed cost, macroeconomic, internal financial data could strongly predict company-level cost flow forecasting. While converting the predicted cumulative cost data to periodic cost flows, the MAPE values were augmented, ranging from 7.04 to 17.55%, thus, requiring future research. 相似文献