全文获取类型
收费全文 | 267859篇 |
免费 | 3257篇 |
国内免费 | 800篇 |
专业分类
电工技术 | 5172篇 |
综合类 | 202篇 |
化学工业 | 40540篇 |
金属工艺 | 14626篇 |
机械仪表 | 11137篇 |
建筑科学 | 6641篇 |
矿业工程 | 1725篇 |
能源动力 | 5896篇 |
轻工业 | 18993篇 |
水利工程 | 2955篇 |
石油天然气 | 4577篇 |
武器工业 | 2篇 |
无线电 | 28208篇 |
一般工业技术 | 55716篇 |
冶金工业 | 42196篇 |
原子能技术 | 5388篇 |
自动化技术 | 27942篇 |
出版年
2021年 | 1625篇 |
2019年 | 1500篇 |
2018年 | 10943篇 |
2017年 | 11583篇 |
2016年 | 7308篇 |
2015年 | 2425篇 |
2014年 | 3295篇 |
2013年 | 8984篇 |
2012年 | 7922篇 |
2011年 | 15820篇 |
2010年 | 13805篇 |
2009年 | 13432篇 |
2008年 | 13323篇 |
2007年 | 15187篇 |
2006年 | 5801篇 |
2005年 | 8997篇 |
2004年 | 7053篇 |
2003年 | 6307篇 |
2002年 | 5251篇 |
2001年 | 4504篇 |
2000年 | 4342篇 |
1999年 | 4380篇 |
1998年 | 10704篇 |
1997年 | 7676篇 |
1996年 | 5969篇 |
1995年 | 4563篇 |
1994年 | 3917篇 |
1993年 | 3840篇 |
1992年 | 2859篇 |
1991年 | 2707篇 |
1990年 | 2629篇 |
1989年 | 2627篇 |
1988年 | 2539篇 |
1987年 | 2283篇 |
1986年 | 2208篇 |
1985年 | 2544篇 |
1984年 | 2364篇 |
1983年 | 2156篇 |
1982年 | 2045篇 |
1981年 | 2102篇 |
1980年 | 1931篇 |
1979年 | 1972篇 |
1978年 | 1891篇 |
1977年 | 2225篇 |
1976年 | 2840篇 |
1975年 | 1672篇 |
1974年 | 1652篇 |
1973年 | 1712篇 |
1972年 | 1420篇 |
1971年 | 1309篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
C. G. Prosgolitis S. G. Lambrakos A. D. Zervaki 《Journal of Materials Engineering and Performance》2018,27(10):5102-5113
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size. 相似文献
72.
Paul Ocheje Ameh Nnabuk Okon Eddy 《Protection of Metals and Physical Chemistry of Surfaces》2018,54(6):1169-1181
Protection of Metals and Physical Chemistry of Surfaces - In this work, phthalic acid is investigated for its corrosion inhibition properties (for aluminum in solutions of HCl and H2SO4) through... 相似文献
73.
74.
75.
76.
77.
78.
79.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
80.