全文获取类型
收费全文 | 40162篇 |
免费 | 3328篇 |
国内免费 | 1604篇 |
专业分类
电工技术 | 3727篇 |
技术理论 | 2篇 |
综合类 | 3881篇 |
化学工业 | 3136篇 |
金属工艺 | 2078篇 |
机械仪表 | 2734篇 |
建筑科学 | 7128篇 |
矿业工程 | 1042篇 |
能源动力 | 3515篇 |
轻工业 | 2320篇 |
水利工程 | 990篇 |
石油天然气 | 1409篇 |
武器工业 | 400篇 |
无线电 | 1728篇 |
一般工业技术 | 4155篇 |
冶金工业 | 2784篇 |
原子能技术 | 489篇 |
自动化技术 | 3576篇 |
出版年
2024年 | 169篇 |
2023年 | 515篇 |
2022年 | 1022篇 |
2021年 | 1174篇 |
2020年 | 1263篇 |
2019年 | 989篇 |
2018年 | 979篇 |
2017年 | 1157篇 |
2016年 | 1372篇 |
2015年 | 1395篇 |
2014年 | 2885篇 |
2013年 | 2576篇 |
2012年 | 2560篇 |
2011年 | 2984篇 |
2010年 | 2233篇 |
2009年 | 2551篇 |
2008年 | 2256篇 |
2007年 | 2799篇 |
2006年 | 2332篇 |
2005年 | 1953篇 |
2004年 | 1676篇 |
2003年 | 1577篇 |
2002年 | 1312篇 |
2001年 | 1047篇 |
2000年 | 818篇 |
1999年 | 725篇 |
1998年 | 505篇 |
1997年 | 437篇 |
1996年 | 403篇 |
1995年 | 298篇 |
1994年 | 243篇 |
1993年 | 169篇 |
1992年 | 128篇 |
1991年 | 100篇 |
1990年 | 98篇 |
1989年 | 76篇 |
1988年 | 56篇 |
1987年 | 45篇 |
1986年 | 29篇 |
1985年 | 27篇 |
1984年 | 31篇 |
1983年 | 25篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1965年 | 5篇 |
1964年 | 5篇 |
1963年 | 5篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
《International Journal of Pressure Vessels and Piping》1996,66(1-3):187-198
The limit carrying capacity of gas pipelines having corrosion defects were evaluated by means of an improved FEM analysis, together with the ANSI/ASME defect judgement and an experimental verification. When compared with our past presentation at the proceedings of the CAPE'93 Colloquium (dealing with reproduced defects), this paper evaluates the remaining lifetime of a pipeline having natural faults. The new improved analysis includes geometrical nonlinearities leading to a modification of limit state parameters and thus matching better with actuality. This presented work was initiated by the firm of Trans-Gas in Prague after having had a pipeline inspected proving some parts of it as being heavily corroded. The task in hand was to determine the remaining pipeline lifetime with the view to at least a two-year period. 相似文献
113.
许进 《西安电子科技大学学报(自然科学版)》1994,(3)
文中解决了2-重自补图的计数问题,获得了具有p个顶点的2-重自补图的数目是其中Z(A)表示置换群A的圈指标,S ̄(2)_p表示p次对称群的对群. 相似文献
114.
115.
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
116.
117.
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
118.
119.
随着我国经济的迅速发展,能源消耗不断增加,节约能源、降低能源消耗势在必行,余热利用是节约能源的一个重要环节,冶金行业高炉冲渣水作为采暖热媒可以节约大量能源。 相似文献
120.
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