全文获取类型
收费全文 | 16972篇 |
免费 | 1685篇 |
国内免费 | 883篇 |
专业分类
电工技术 | 939篇 |
综合类 | 1205篇 |
化学工业 | 2806篇 |
金属工艺 | 1040篇 |
机械仪表 | 1035篇 |
建筑科学 | 1087篇 |
矿业工程 | 382篇 |
能源动力 | 618篇 |
轻工业 | 1264篇 |
水利工程 | 275篇 |
石油天然气 | 617篇 |
武器工业 | 197篇 |
无线电 | 2299篇 |
一般工业技术 | 2106篇 |
冶金工业 | 665篇 |
原子能技术 | 149篇 |
自动化技术 | 2856篇 |
出版年
2024年 | 40篇 |
2023年 | 236篇 |
2022年 | 421篇 |
2021年 | 655篇 |
2020年 | 465篇 |
2019年 | 460篇 |
2018年 | 523篇 |
2017年 | 531篇 |
2016年 | 565篇 |
2015年 | 634篇 |
2014年 | 786篇 |
2013年 | 975篇 |
2012年 | 1097篇 |
2011年 | 1201篇 |
2010年 | 1106篇 |
2009年 | 1018篇 |
2008年 | 1034篇 |
2007年 | 959篇 |
2006年 | 888篇 |
2005年 | 715篇 |
2004年 | 711篇 |
2003年 | 856篇 |
2002年 | 1118篇 |
2001年 | 867篇 |
2000年 | 443篇 |
1999年 | 295篇 |
1998年 | 157篇 |
1997年 | 152篇 |
1996年 | 130篇 |
1995年 | 95篇 |
1994年 | 64篇 |
1993年 | 67篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 25篇 |
1989年 | 14篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
快速星图匹配算法的研究 总被引:9,自引:5,他引:4
将态敏感和姿态稳定是卫星的重要技术之一。星体敏感器是目前最高精度的姿态测量技术。对于这种技术,很多文献都进行了讨论,并涌现了许多关于星图匹配行之有效的算法。 相似文献
52.
Characterization of the cavity nucleation factor for life prediction under creep-fatigue interaction
Baig Gyu Choi Soo Woo Nam Young Cheol Yoon Joong Jae Kim 《Journal of Materials Science》1996,31(18):4957-4966
It is understood that grain boundary cavitation is one of the detrimental processes for the degradation of materials that reduces the creep-fatigue life at high temperatures. In a previous investigation, a model for life prediction under creep-fatigue conditions was proposed in terms of cavity nucleation and growth. In that model, the cavity nucleation factor (P) was introduced to correlate between the number of cavities and the plastic strain range from which athermal vacancies are generated. It was considered to be a material specific constant which was independent of the experimental conditions. However, in this study, it is found that the cavity nucleation factor is a function of the plastic strain range but is independent of the testing temperature at near 0.5 T
m. In the light of this dependency, a new cavity nucleation factor (P'), is introduced. Using this new cavity nucleation factor (P'), a modified equation for life prediction is proposed, and it is shown that there is good agreement between predicted and experimental lives. Additionally, an interesting approach has been made to find the physical meaning of the new cavity nucleation factor (P'). According to this study, it is suggested that the new cavity nucleation factor, which is regarded as a material specific constant, is found to be strongly related to the density of the grain boundary precipitates with a linear relationship existing between them. 相似文献
53.
A practical and efficient method is presented for the counting of third-order products generated by an arbitrary number of carriers with arbitrary power spectral shapes. In particular, three selective counting procedures (i.e. sorting by position, sorting by position and group, and sorting by position, group, and kind) are introduced in a systemic way, based upon a discrete third-order Volterra model. The advantage of the counting algorithm is that (1) the algorithm provides the exact counting of third-order products of all eleven possible groups; (2) the counting process requires only two multiplications for the selective counting of third-order products at each position, and the algorithm, which is thus efficient, can be easily implemented 相似文献
54.
A new method using high‐intensity ultrasonic waves, instead of peroxide‐aided reactive extrusion, was applied to modify a linear polypropylene into a branched structure. The ultrasonic waves induced chain scission and created reactive macromolecules of polypropylene successfully in the melt state without any peroxide. To enhance and control the recombination reaction during sonication, a multifunctional agent and an antioxidant were used. The rheological property measurements clearly confirmed that the modified polypropylene had a nonlinear branched structure. It showed shear‐thinning behaviors in its viscosities at low frequencies, high elastic behaviors in Cole–Cole plots, and a high rheological polydispersity index in comparison with a linear polypropylene. The degradation or recombination of polypropylene was adequately controlled by an antioxidant, which stabilized the structure during sonication. Also, the use of an antioxidant was quite effective in improving the extrusion processability by delaying the instability of the extrudate to a higher shear rate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
55.
56.
模糊规划在炼油厂生产计划优化中的应用 总被引:7,自引:1,他引:6
生产计划的编制是炼油化工企业生产经营管理中的一个关键环节,然而由于市场变化的不确定性,使得企业的长远规划制定受到限制,笔者将模糊数学应用于炼厂生产计划的编制,通过模糊规划对炼油企业生产计划进行优化,使编得的生产计划在一定程度上反映市场的变化并使企业的生产效益最优,为企业管理决策者进行长期规划给予指导,给出了实例来说明该方法的可行性。 相似文献
57.
Young-Taek Lee Jong-Sik Lim Jun-Seok Park Ahn D. Sangwook Nam 《Microwave and Wireless Components Letters, IEEE》2002,12(2):39-41
A new technique to reduce the phase noise in microwave oscillators is developed using the resonant characteristic of the defected ground structure (DGS). Two kinds of oscillators have been designed and measured for the examination of the reduction of phase noise by the DGS. The first adopts the DGS section under the microstrip line at the gate circuit, while the second has only the conventional microstrip line. Measurement shows reduced phase noise by 10-15 dB in the oscillator with the DGS compared to the conventional one 相似文献
58.
中频反应溅射SiO2膜与直流溅射ITO膜的在线联镀 总被引:2,自引:2,他引:0
多数ITO透明导电玻璃生产线在实现SiO2膜与ITO膜在线联镀时,应用SiO2靶射频溅射沉积SiO2膜工艺和ITO靶直流溅射沉积ITO膜工艺,如果SiO2膜应用硅靶反应磁控溅射工艺,存在这种工艺是否可以与ITO靶直流溅射沉积ITO膜工艺在线联用以及如何实现联用的问题。作者对现有的生产线进行了改造设计、加工,做了大量实验、质谱分析和多项测试研究,成功地实现反应溅射SiO2膜与ITO膜在线联镀,做到SiO2镀膜室的工作状态的变化基本上不影响ITO镀膜室的工艺条件。 相似文献
59.
采动覆岩中关键层运动对围岩支承压力分布的影响 总被引:5,自引:2,他引:3
运用数值模拟方法,主要分析了关键层的破断、关键层相对位置及采深等对围岩支承压力的影响;同时,研究了采空区支承压力的分布规律.研究结果对采场围岩的控制提供了一定的理论依据. 相似文献
60.
聚苯乙烯(PS)在苯溶液中与溴代丁二酰亚胺(NBS)反应,经分离提纯得到了固体溴代聚苯乙烯(PSB)。将所得PSB溶于苯并与低分子量的聚二甲基硅氧烷硅醇锂(PDMSOLi)反应,经分离提纯得到固体的溴代聚苯乙烯接枝聚二甲基硅氧烷(PSB-g-PDMSO),所得PSB-g-PDMSO的结构经^1H-NMR、IR及TEM表征。 相似文献