全文获取类型
收费全文 | 17085篇 |
免费 | 1202篇 |
国内免费 | 739篇 |
专业分类
电工技术 | 1875篇 |
技术理论 | 1篇 |
综合类 | 1857篇 |
化学工业 | 925篇 |
金属工艺 | 296篇 |
机械仪表 | 552篇 |
建筑科学 | 4844篇 |
矿业工程 | 557篇 |
能源动力 | 914篇 |
轻工业 | 406篇 |
水利工程 | 515篇 |
石油天然气 | 468篇 |
武器工业 | 103篇 |
无线电 | 812篇 |
一般工业技术 | 899篇 |
冶金工业 | 1062篇 |
原子能技术 | 51篇 |
自动化技术 | 2889篇 |
出版年
2024年 | 41篇 |
2023年 | 162篇 |
2022年 | 302篇 |
2021年 | 341篇 |
2020年 | 425篇 |
2019年 | 311篇 |
2018年 | 315篇 |
2017年 | 367篇 |
2016年 | 442篇 |
2015年 | 454篇 |
2014年 | 1480篇 |
2013年 | 1145篇 |
2012年 | 1182篇 |
2011年 | 1161篇 |
2010年 | 950篇 |
2009年 | 1247篇 |
2008年 | 1130篇 |
2007年 | 1494篇 |
2006年 | 1093篇 |
2005年 | 866篇 |
2004年 | 748篇 |
2003年 | 798篇 |
2002年 | 592篇 |
2001年 | 436篇 |
2000年 | 362篇 |
1999年 | 270篇 |
1998年 | 194篇 |
1997年 | 142篇 |
1996年 | 135篇 |
1995年 | 112篇 |
1994年 | 75篇 |
1993年 | 55篇 |
1992年 | 43篇 |
1991年 | 27篇 |
1990年 | 30篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
文章结合作者近年来工程项目管理的实践,阐述了目前施工企业工程项目管理中存在的问题,并就如何提高工程项目管理水平,提出一些有益的建议。 相似文献
43.
Capital cost correlations are given for oil-water separators, equalization basins, primary clarifiers, clarifiers and clarifier mechanisms, reverse osmosis unit, ultrafiltration units, gravity filters and miroscreens. Data are included for raw sewage, intermediate and recirculation pumping stations and for preliminary treatment (or bar screens, grit removal, overflow and bypass chamber and Parshall flume), for grit removal, comminution and gas stripping. The correlations are accurate to ± 30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module. For inflation indices, a critique of the Engineering News Record, EPA small city, Marshall and Swift, Chemical Engineering and Southam inflation indices suggested that the Marshall and Swift index is most appropriate for the construction and process equipment studied here. Concerning the currency exchange, for the equipment and processes in this study, equipment costs the same whether expressed directly in US or Canadian dollars. To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data. 相似文献
44.
In the history of operations research in industry there has been an abundance of analyses and recommendations produced in millions of man hours by dedicated OR specialists. And yet the net improvement is significantly lower than expected. There are numerous reasons for this shortfall: incomplete analysis, too much theory, incomplete implementation, unreliable recommendations, or a combination of some of these reasons.
By describing several examples, the major reasons for the fragility of the link between recommendation and implementation will be reviewed. What has to be done today to increase the likelihood of implementing an OR recommendation and thus improve the performance of an industrial entity by using the power of OR tools will then be described. 相似文献
By describing several examples, the major reasons for the fragility of the link between recommendation and implementation will be reviewed. What has to be done today to increase the likelihood of implementing an OR recommendation and thus improve the performance of an industrial entity by using the power of OR tools will then be described. 相似文献
45.
Verbruggen Frederick; Liefooghe Baptist; Vandierendonck André; Demanet Jelle 《Canadian Metallurgical Quarterly》2007,33(2):342
In the task-switching literature, it has frequently been demonstrated that although advance task preparation reduces the switch cost, it never really eliminates the switch cost. This remaining residual switch cost received much attention, and it has been argued that advance preparation is restricted in nature. In the present study, the role of task-cue presentation in the establishment of the residual switch cost was investigated. In 4 experiments, the cue was removed during the preparation interval, and it was hypothesized that this would encourage participants to complete advance task preparation. The results of all 4 experiments provided support for this hypothesis: When the cue was presented for a short time and then removed, the residual switch cost completely disappeared. This was found for different cue types. Furthermore, Experiment 3 demonstrated that it was not the presence of the cue itself but merely differences in advance task preparation that caused the effects. This suggests that advance task preparation is not as restricted in nature as previously assumed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
提出了技术杠杆的概念,并就技术成本杠杆和技术价格杠杆对企业息税前收益变化的影响程度进行了探讨,经理论计算说明了通过技术进步不但可以提高企业的息税前收益,而且当企业的经济效益越差时,技术进步使产品的变动成本降低或使产品的单位售价提高而带来的企业息税前收益提高的速度越快。 相似文献
47.
48.
M.A.K. Lodhi 《Energy Conversion and Management》1996,37(12):1677-1694
Solar ponds are probably the simplest technology available for the useful conversion of solar energy. The basic technology is proven. Solar ponds have been shown to be technically feasible and economically viable for many applications, particularly for thermal use. The electrical conversion and use of solar energy via solar ponds is still questionable, in general, for economic viability. By putting the untapped sources together in the South Plains region, it looks promising economically both for thermal and electrical conversions and applications. There are a number of alkaline lake basins randomly scattered in the South Plains region of the U.S.A. In that area, there are thousands of crude oil producing wells that produce brine in abundance. The selection of suitable alkaline lake basins as a solar pond site and as depository sites of brine from oil wells and the using of this brine and salty water from alkaline lakes makes the solar pond economically viable for both thermal and electrical demands in the area. 相似文献
49.
本文详细介绍了变频调速节能改造方案的经济性评价方法。静态分析法包括投资回收期法、抵偿年限法和年计算费用法;动态分析法则包括净现值法、内部回收率法、总费用现值法和最小年费用法。 相似文献
50.