全文获取类型
收费全文 | 138篇 |
免费 | 2篇 |
国内免费 | 13篇 |
专业分类
系统科学 | 29篇 |
丛书文集 | 3篇 |
教育与普及 | 1篇 |
理论与方法论 | 1篇 |
综合类 | 119篇 |
出版年
2023年 | 3篇 |
2022年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1989年 | 1篇 |
1988年 | 3篇 |
排序方式: 共有153条查询结果,搜索用时 15 毫秒
71.
为了探索模拟Pu4+在Gd2Zr2O7中实现快速固化的可能性,用CeO2替代PuO2,以CeO2,ZrO2和Gd2O3混合粉体为原料进行了高温高压合成实验,借助XRD衍射图谱、EDS谱和Raman谱研究了材料的微观结构。结果表明:在5.2 GPa的高压和1 873 K的高温条件下,保温保压30 min,成功制备出具有立方烧绿石结构的Gd2Zr2-xCexO7化合物。对该合成样品进行SEM电镜扫描观察,形成的晶粒小于30μm。该法可为开展α废物(特别是钚)的固化研究提供参考。 相似文献
72.
73.
模拟退火算法是以固体退火过程为物理背景的全局优化算法,具有全局寻优的能力,是一种有效的非线性组合优化算法。模拟退火反演算法实质是利用了地球物理反演问题求解过程与熔化固体退火过程的相似性,模拟其达到最低能量状态为系统目标函数的最优解。本文概要地介绍了模拟退火法的基本原理,解的接受准则,模拟退火法的实现方法、特点及其局限性。总结了近年来对模拟退火方法进行的改进,并给出了模拟退火法在多层密度界面反演中的实例。 相似文献
74.
研究了热处理对电子束蒸发法制备的TiO2薄膜结构和表面形貌的影响。利用X射线衍射仪和原子力显微镜,检测了TiO2薄膜的晶体结构和表面形貌。实验结果显示:沉积态TiO2薄膜为非晶态;低温(400℃以下)退火TiO2薄膜开始向锐钛矿相转变;高温退火(850℃以下)TiO2薄膜由锐钛矿向金红石相转变。 相似文献
75.
禹建丽 《河南科技大学学报(自然科学版)》2001,22(3):50-52
针对已知障碍物形状和位置环境下的机器人全局路径规划问题 ,提出利用神经网络路径规划算法进行路径规划。为解决神经网络路径规划算法的局部极小值问题 ,提出针对障碍物的形状设定各条边的模拟退火初始温度。采用此方法仿真试验的结果表明 ,该方法能够避免某些局部极小值情况 ,规划的无碰路径达到了最短无碰路径 相似文献
76.
利用基于模拟退火算法的神经网络技术进行测井约束的波阻抗反演,可根据数据本身之间的内在联系建立一个自适应非线性认知系统,只要在输入端输入特征数据,便能在输出端得到期望输出值,而不必关心系统本身的内部机理。在反演前,从测井资料中整理出地层波阻抗参数,用神经网络建立起地震波特征和地层波阻抗参数的映射关系,然后再利用这种映射关系进行外推,得到其它地震道所对应的波阻抗参数。在训练过程中,引入了模拟退火算法,使网络能有效地避开局部极小,这样可以提高收敛速度和拟合精度。 相似文献
77.
78.
《自然科学进展(英文版)》2022,32(2):206-214
Rare-earth AB5-type La–Ni–Al hydrogen storage alloys are widely studied due to their extensive application potentials in hydrogen isotope storage, hydrogen isotope isolation and hydrogen compressors, etc. Good hydriding/dehydriding kinetics, easily activation, high reversibility are important factors for their practical application. However, their overall hydrogen storage performance, especially plateau pressure and hydrogen absorption/desorption durability need to be further optimized. In this study, the microstructures and the hydrogen storage properties of as-cast, annealed, and melt-spun LaNi3.95Al0.75Co0.3 alloys were investigated. The experimental results of XRD and SEM showed that all alloys contained a pure CaCu5 type hexagonal structure LaNi4Al phase. The cell volume increased in an order of annealed ?> ?melt-spun ?> ?as-cast, resulting in a lower hydrogen absorption/desorption plateau pressure and a more stable hydride phase. The hydrogen storage capacity of three alloys was almost the same. The slope factor of the annealed and melt-spun alloys is smaller than the as-cast alloy, indicating that heat-treatment process can make the alloys more uniform. For the cycle stability of the alloys, the hydrogen absorption rate of the annealed alloy and melt-spun alloy was much faster than that of the as-cast alloy after 500 cycles. The melt-spun alloy showed high pulverization resistance during hydrogen absorption/desorption, and exhibited an excellent cycling retention of 99% after 500 cycles, suggesting that melt-spinning process can enhance the cycle stability and improve the cycle life of the alloy. 相似文献
79.
Ebrahim Karamian Mahmood Reza Kalantar Motamedi Amirsalar Khandan Parisa Soltani Sahel Maghsoudi 《自然科学进展(英文版)》2014,24(2):68-74
The surface characteristics of an implant that influence the speed and strength of osseointegration include crystal structure and bioactivity. The aim of this study was to evaluate the bioactivity of a novel natural hydroxyapatite/zircon(NHA/zircon) nanobiocomposite coating on 316L stainless steel(SS) dental implants soaking in simulated body fluid. A novel NHA/zircon nanobiocomposite was fabricated with 0(control),5, 10, and 15 wt% of zircon in NHA using ball mill for 1 h. The composite mixture was coated on SS implants using a plasma spray method.Scanning electron microscopy(SEM) was used to evaluate surface morphology, and X-ray diffraction(XRD) was used to analyze phase composition and crystallinity(Xc). Further, calcium ion release was measured to evaluate the coated nanobiocomposite samples. The prepared NHA/zircon coating had a nanoscale morphological structure with a mean crystallite size of 30–40 nm in diameter and a bone-like composition,which is similar to that of the biological apatite of a bone. For the prepared NHA powder, high bioactivity was observed owing to the formation of apatite crystals on its surface. Both minimum crystallinity(Xc=41.1%) and maximum bioactivity occurred in the sample containing 10 wt% of zircon because of minimum Xcand maximum biodegradation of the coating sample. 相似文献
80.
In this paper, an approach for resource-constrained flexible manufacturing system (FMS) scheduling was proposed, which is based on the particle swarm optimization (PSO) algorithm and simulated annealing (SA) algorithm. First, the formulation for resource-constrained FMS scheduling problem was introduced and cost function for this problem was obtained. Then, a hybrid algorithm of PSO and SA was employed to obtain optimal solution. The simulated results show that the approach can dislodge a state from a local minimum and guide it to the global minimum. 相似文献