全文获取类型
收费全文 | 687篇 |
免费 | 76篇 |
国内免费 | 75篇 |
专业分类
电工技术 | 10篇 |
综合类 | 44篇 |
化学工业 | 104篇 |
金属工艺 | 26篇 |
机械仪表 | 92篇 |
建筑科学 | 9篇 |
矿业工程 | 9篇 |
能源动力 | 2篇 |
轻工业 | 75篇 |
水利工程 | 5篇 |
石油天然气 | 11篇 |
武器工业 | 3篇 |
无线电 | 139篇 |
一般工业技术 | 83篇 |
冶金工业 | 78篇 |
原子能技术 | 22篇 |
自动化技术 | 126篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 21篇 |
2017年 | 17篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 52篇 |
2013年 | 67篇 |
2012年 | 65篇 |
2011年 | 37篇 |
2010年 | 53篇 |
2009年 | 54篇 |
2008年 | 38篇 |
2007年 | 41篇 |
2006年 | 44篇 |
2005年 | 41篇 |
2004年 | 35篇 |
2003年 | 37篇 |
2002年 | 41篇 |
2001年 | 33篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有838条查询结果,搜索用时 46 毫秒
1.
Yang Luo Shi-li Zheng Shu-hua Ma Chun-li Liu Xiao-hui Wang 《Journal of the European Ceramic Society》2018,38(16):5282-5293
A novel mullite-bonded SiC-whisker-reinforced SiC matrix composite (SiCw/SiC, SiC whisker-to-SiC powder mass ratio of 1:9) was designed and successfully prepared. Before preparing the composite, the inexpensive lab-made SiCw was first modified by an oxidation/leaching process and then coated with Al2O3. The kinetics results indicate that the oxidation process can be described by improved shrinking-cylinder models. The aspect ratio of SiCw improved after modification. Subsequently, raw materials with a SiC–SiO2–Al2O3 triple-layered structure were obtained after the Al2O3-coating process and used as feedstocks during the subsequent hot-pressing sintering. Finally, the characterization of the composites indicates that the mullite-bonded sample performs better (relative density of 93.8?±?1.4%, flexural strength of 533.3?±?18.2?MPa, fracture toughness of 13.6?±?2.1?MPa?m1/2, and Vickers hardness of 20.6?±?2.5?GPa) than the reference sample without the mullite interface. The improved toughness could essentially be attributed to the moderately strong interface bonding and effective load transfer effects of the mullite interface. 相似文献
2.
为克服迭代最近点(ICP)算法易陷入局部最优的缺陷,提出一种基于线特征及ICP算法的地基建筑物点云自动配准方法。首先,基于法向一致性进行建筑物点云平面分割;接着,采用alpha-shape算法进行点簇轮廓线提取,并拆分和拟合处理得到特征线段;然后,以线对作为配准基元,以线对夹角和距离作为相似性测度进行同名特征匹配,实现建筑物点云的粗配准;最后,以粗配准结果为初值,进一步采用ICP算法完成点云精确配准。利用两组部分重叠的建筑物点云进行配准实验,实验结果表明,采用由粗到精的配准方法能有效改善ICP算法对初值依赖的问题,实现具有部分重叠的建筑物点云的有效配准。 相似文献
3.
4.
5.
通过微电子机械技术(MEMS)在抛光的熔融石英基材表面制作了平面精度达到0.4μm的超大单片面积的全息透镜。采用了分辨率达到0.2μm的步进投影式拼接光刻,适合石英基材的专用等离子耦合刻蚀(ICP)干法刻蚀技术,特殊的物理清洗方法,以及相关的多项辅助工艺。透镜理想面形横截面曲线为分段抛物线,每一片由23个柱状结构单元周期横向排列构成,采用等深度不等宽度的4台阶结构拟合,单元宽度约为2.966mm。在4in(10.16cm)圆片上,获得了单片尺寸为68mm×68mm的方形透镜。采用接触式台阶仪,扫描电子显微镜(SEM),高倍光学显微镜等方法进行不同阶段检测。结果显示:台阶平面精度为0.4μm,垂直精度为30nm,有非常好的立墙陡直度和刻蚀均匀性。此工艺方案可实现小规模批量生产,成本适中,可以直接用于制作6in(15.24cm)以上同等级要求的石英透镜,经适当改进也可用于蓝宝石等基底材料的制作。 相似文献
6.
7.
《中国工程学刊》2012,35(1):101-113
Changes of the cartilage morphology over time can tell the progression of osteoarthritis (OA) and show particular promise for evaluating the efficacy of disease-modifying OA drugs. Hence, cartilage matching is required prior to cartilage morphology comparison. An accurate cartilage matching allows one to ensure longitudinal focal and local changes of cartilage morphology due to OA. The method described in this article meets this need. The proposed method consists of three steps. First, the knee femur surfaces are aligned, using the principal axes transformation to correct for different knee joint positions and orientations in the magnetic resonance (MR) scanner. Second, we present a global registration algorithm based on Lipschitz optimization theory for accurately identifying the corresponding points of the knee femur surface. Third, the rigid transformation of the knee femur surface registration is applied to the cartilage surface. Our registration algorithm is efficient and robust, and its performance is evaluated on MR images of pig knees. 相似文献
8.
Multiple measurements using various data acquisition systems are generally required to substancially enhance measurement accuracy, reliability and holisticity of freeform shapes. The obtained multiple measurement data of the shape are transformed and fused into a common coordinate system within a registration technique involving coarse and fine alignments. Standardized methods have been established for fine registration such as Iterative Closest Points (ICP) and its variants. For coarse registration, no conventional method has been adopted yet despite a significant number of techniques which have been developed in the literature to supply an automatic rough matching between data sets.The work presented in this paper proposes an improvement of registration techniques by the consideration of new discrete curvature parameters. Two main issues are addressed in this paper: the coarse registration and the fine registration. For coarse registration, two novel automated methods based on the exploitation of discrete curvatures are presented: an enhanced Hough Transformation (HT) and an improved Ransac Transformation. The use of curvature features in both methods aims to reduce computational cost. For fine registration, a new variant of ICP method is proposed in order to reduce registration error using curvature parameters. A specific distance considering the curvature similarity is combined with Euclidean distance to define the distance criterion used for correspondences searching. Additionally, the objective function is improved by combining the point-to-point (P-P) minimization and the point-to-plane (P-Pl) minimization with automatic weights. The algorithms are applied on simulated and real data performed by a computed tomography (CT) system. The obtained results reveal the benefit of the proposed improved curvature-based registration methods. 相似文献
9.
报道了在GaN表面以Ni纳米岛结构作为模板,利用电感耦合等离子(ICP)刻蚀制备GaN纳米柱的研究结果。原子力显微镜(AFM)测试结果表明,金属Ni薄膜在快速热退火(RTA)作用下形成了平均直径和高度大约分别为325 nm和70 nm的纳米岛状结构。通过电子扫描显微镜(SEM)照片看出,以GaN表面所形成的Ni纳米岛作为模板图形,通过控制ICP刻蚀时间,在一定的刻蚀时间内(2 min)获得有序的并拥有半极性晶面的GaN纳米柱阵列。这种新颖的半极性GaN纳米柱作为氮化物量子阱或者超晶格结构的生长模板,可以有效减小甚至消除极化效应,提高光电子器件的效率和性能。 相似文献
10.
介绍了改进GaN功率MMIC背面通孔工艺的相关方法,并对通孔进行了可靠性方面的测试与分析。通过优化机械研磨的方法,减薄圆片至75μm左右,保持片内不均匀性在4%以内;利用ICP对基于SiC衬底的GaN功率MMIC进行了背面通孔工艺的优化,减少了孔底的柱状生成物。随后的可靠性测试测得圆片通孔的平均电阻值为6.3 mΩ,平均电感值为17.2 nH;对通孔样品在0.4 A工作电流175°C节温下进行了工作寿命试验,200 h后通孔特性无明显退化。 相似文献