全文获取类型
收费全文 | 89107篇 |
免费 | 14343篇 |
国内免费 | 6856篇 |
专业分类
电工技术 | 12853篇 |
技术理论 | 2篇 |
综合类 | 7354篇 |
化学工业 | 3429篇 |
金属工艺 | 12460篇 |
机械仪表 | 7223篇 |
建筑科学 | 4388篇 |
矿业工程 | 2021篇 |
能源动力 | 1200篇 |
轻工业 | 5157篇 |
水利工程 | 1165篇 |
石油天然气 | 2870篇 |
武器工业 | 1075篇 |
无线电 | 14389篇 |
一般工业技术 | 6628篇 |
冶金工业 | 2540篇 |
原子能技术 | 780篇 |
自动化技术 | 24772篇 |
出版年
2024年 | 699篇 |
2023年 | 1928篇 |
2022年 | 3198篇 |
2021年 | 3498篇 |
2020年 | 3611篇 |
2019年 | 2924篇 |
2018年 | 2659篇 |
2017年 | 3544篇 |
2016年 | 3727篇 |
2015年 | 4156篇 |
2014年 | 6675篇 |
2013年 | 6150篇 |
2012年 | 7190篇 |
2011年 | 7489篇 |
2010年 | 5708篇 |
2009年 | 5584篇 |
2008年 | 5440篇 |
2007年 | 6337篇 |
2006年 | 5477篇 |
2005年 | 4564篇 |
2004年 | 3713篇 |
2003年 | 3168篇 |
2002年 | 2522篇 |
2001年 | 2059篇 |
2000年 | 1652篇 |
1999年 | 1374篇 |
1998年 | 1057篇 |
1997年 | 854篇 |
1996年 | 777篇 |
1995年 | 573篇 |
1994年 | 406篇 |
1993年 | 303篇 |
1992年 | 285篇 |
1991年 | 225篇 |
1990年 | 181篇 |
1989年 | 145篇 |
1988年 | 107篇 |
1987年 | 55篇 |
1986年 | 53篇 |
1985年 | 45篇 |
1984年 | 35篇 |
1983年 | 34篇 |
1982年 | 22篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
91.
Ti-23Al-14Nb-3V合金氩弧焊接头的显微组织及其力学性能 总被引:6,自引:1,他引:5
研究了预热对Ti-23Al-14Nb-3V合金焊接性,特别是对消除氩弧焊冷裂纹的作用以及对接头显微组织和力学性能的影响。结果表明,焊前预热可有效降低该合金的冷裂倾向。经预热处理后,焊缝区的结晶层状线消失,热影响区的硬度峰得到缓和,整个焊缝的显微硬度分布趋于均匀,但焊缝区的枝晶发生粗化,热影响区有所扩大。焊件接头的拉伸试验表明,预热可使焊缝区的接头强度系数增加,但无论预热与否,接头强度均低于母材强度,且不显示宏观塑性。 相似文献
92.
Barrett Lisa Feldman; Quigley Karen S.; Bliss-Moreau Eliza; Aronson Keith R. 《Canadian Metallurgical Quarterly》2004,87(5):684
People differ in the extent to which they emphasize feelings of activation or deactivation in their verbal reports of experienced emotion, termed arousal focus (AF). Two multimethod studies indicate that AF is linked to heightened interoceptive sensitivity (as measured by performance on a heartbeat detection task). People who were more sensitive to their heartbeats emphasized feelings of activation and deactivation when reporting their experiences of emotion over time more than did those who were less sensitive. This relationship was not accounted for by several other variables, including simple language effects. Implications for the role of interoception in experienced emotion and the validity of self-reported emotion are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
二维地震过障碍观测系统模式及其参数设计 总被引:2,自引:1,他引:1
在二维地震勘探中,为了避免因地表障碍物使地震反射剖面出现间断现象,需要改变观测系统设计,跨越障碍物(江河、城镇等),以保证反射同相轴能连续追踪对比。在以往地震勘探中,有时因过障碍观测系统设计不合理,不但增加勘探费用,而且影响采集质量。因此只有科学合理地设计过障碍观测系统模式和参数,才能保证地震测线顺利通过障碍物,得到较好的障碍物下方的地震资料并降低勘探成本。为此本文在调查和研究大量野外实际的过障碍观测系统的基础上,总结归纳成三大类过障碍观测系统模式,并分析其特点和应用范围。采用图解法,推导出主要模式的跨越宽度、最小炮检距及最大炮检距等参数公式。采用这套过障碍观测模式不仅可以得到和障碍区两侧等质量的地震资料,而且可以有效地降低勘探成本。 相似文献
94.
95.
靳军 《石油化工安全环保技术》2003,19(3):17-18
简述了大庆油田助剂厂3500kt/a常减压减压塔的管道布置设计特点,体现出塔类设备的管道设计原则,并结合管道设计的经济性、安全性展开论述。 相似文献
96.
The mechanical and microstructural properties of 6061+20% Al2O3p and 7005+10% Al2O3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation. 相似文献
97.
98.
European intercomparison on electron spin resonance identification of irradiated foodstuffs 总被引:1,自引:0,他引:1
J. RAFFI † M. H. STEVENSON M. KENT J. M. THIERY J.-J. BELLIARDO 《International Journal of Food Science & Technology》1992,27(2):111-124
The results of a co-trial organized by the Community Bureau of Reference on the use of Electron Spin Resonance spectroscopy for the identification of irradiated food in 21 laboratories are presented. The trial was qualitative on beef and trout bones, sardine scales, pistachio nut shells, dried grapes, and papaya, and quantitative on poultry bones. There was no difficulty in identifying irradiated meat bones, dried grapes, and papaya. In the case of fish bones there is a need for further kinetic study on different species. Identification of irradiation in pistachio nuts is more complicated and additional research is needed before further trials. All laboratories were able to distinguish between chicken bones irradiated at 1 to 3 kGy or 7 to 10 kGy although there was a partial overlap between the results. 相似文献
99.
In the first half of the paper, various types of processing pertaining to a polygon, using the 4×4 determinant theories are explained along with a new containment test algorithm of a point in a polygon. In the latter half of the paper, a general-purpose geometric processor, the POLYGON ENGINE, is presented which can deal with various types of interference problems, such as Boolean operations in solid modelling, hidden line and surface eliminations, ray tracing and so on. It is, a successor of the TRIANGLE PROCESSOR and is also based upon the 4×4 determinant theories [4–6]. While the TRIANGLE PROCESSOR processes a triangulated polygon on a triangle-by-triangle basis, the POLYGON ENGINE can treat a polygon without triangulation. The latter is expected to be more functional, more efficient and easier to use. 相似文献
100.