全文获取类型
收费全文 | 1327篇 |
免费 | 228篇 |
国内免费 | 106篇 |
学科分类
工业技术 | 1661篇 |
出版年
2024年 | 5篇 |
2023年 | 54篇 |
2022年 | 91篇 |
2021年 | 129篇 |
2020年 | 77篇 |
2019年 | 67篇 |
2018年 | 74篇 |
2017年 | 70篇 |
2016年 | 66篇 |
2015年 | 96篇 |
2014年 | 78篇 |
2013年 | 84篇 |
2012年 | 107篇 |
2011年 | 125篇 |
2010年 | 91篇 |
2009年 | 75篇 |
2008年 | 66篇 |
2007年 | 55篇 |
2006年 | 72篇 |
2005年 | 42篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 9篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 12篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1661条查询结果,搜索用时 31 毫秒
1.
运动员检测是篮球运动智能化分析的基础,由于篮球视频存在场景复杂、目标运动快速、目标间遮挡严重的问题,现有目标检测技术不能实现对密集遮挡运动员的精确检测.为此,提出一种基于自适应关键点热图的遮挡篮球运动员检测算法.首先通过预先构建的全卷积编码-解码网络进行运动员特征提取,利用高斯核函数在特征图上渲染关键点热图,热图的渲染采用自适应策略,高斯核半径随着目标宽和高的变化而变化,能够加快网络收敛;然后在热图中提取运动员中心点,回归得到运动员宽高、位置等信息,省去了基于锚框检测中复杂耗时的后处理过程,更利于在遮挡条件下区分2个运动员.在篮球运动数据集BasketballPlayer上进行实验的结果表明,在复杂篮球视频场景下,该算法能有效地解决密集遮挡运动员之间漏检、误检和检测精度不高的问题,处理速度可达到26帧/s. 相似文献
2.
High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bonding time on microstructure evolution and mechanical properties of the TLP joints were investigated.Owing to the complete isothermal solidification of the joints bonded for 30 min 120 min at 1100°C,no athermally solidified zones(ASZs) formed by eutectic phases were observed in the welded zone. Thus the TLP joints were only composed by the isothermally solidified zone(ISZ) and two diffusion affected zone(DAZ) adjacent to the dissimilar base metals and the negative effect of the ASZ on joint properties can be avoided. In addition, the increase of the bonding time can also make the Ti B2 borides precipitated in the DAZ near HEA and the brittle borides or carbides in the DAZ near IN718 alloy decrease and reduce the possibility of the stress concentration happened in the joints under loading. Therefore, the highest shear strength(632.1 MPa) of the TLP joints was obtained at 1100°C for 120 min, which was higher than that of the joint bonded for 30 min, 404.2 MPa. Furthermore, the extension of the bonding time made the fracture mechanism of the joint be transformed from the intergranular fracture to the transgranular fracture. However, as the brittle borides in the DAZ near IN718 can not be eliminated completely and refining of grains also happened in such region, all the TLP joints fractured inner the DAZ near IN718 alloy. 相似文献
3.
Shichao Zhang Zhen Wang Chao Chen Jiangtao Jia Zhibin Chen 《International Journal of Hydrogen Energy》2021,46(10):7415-7425
The helium-cooled lead lithium (PbLi) blanket is considered as one of the candidate blanket concepts selected for the hydrogen fusion DEMO reactors and beyond, which has the advantages of simple structure, strong heat removal capacity and high tritium breeding ratio. However, due to the harsh environment such as high-energy neutron irradiation, high thermal load and great pressure gradient, there is a high possibility that one or some of the thousands of coolant channels will break in the breeding zone, which is so-called In-box Loss of Coolant Accident (In-box LOCA). When the accident occurs, the high pressure helium will rapidly inject into the lead lithium flow channel, generating a complex two-phase flow and great pressure shock effect, which may cause the peak pressure to exceed the design limit and threaten the integrity of the blanket structure. Therefore, it is of great significance to perform the transient analysis of in-box LOCA to improve the safety of the blanket and avoid the leakage of radioactive materials. In this paper, a two-way coupling model for fluid-solid interaction was established based on the ANSYS Workbench, and the model were validated through the experimental data obtained by injecting the high pressure helium gas into liquid lithium lead. Then the validated model was applied to the transient pressure wave propagation analysis and structural stress analysis of the Dual-Functional Lithium Lead (DFLL) blanket in order to explore the integrity of blanket structure under In-box LOCA. In addition, the effects of break location on pressure and structural stress was also investigated through six cases. The study found that the transient pressure in the DFLL blanket gone through three stages in any case: step rise, oscillate, and flatten out. Pressure peaks occurred during oscillations and their values were strongly dependent on the break location. The closer to the inlet/outlet, the higher the peak pressure was. The maximum pressure reached more than twice of the inlet pressure (up to ~16 MPa). As a result, the structural stress in some local areas has exceeded the allowable limits, and the corresponding suggestions for improvement have also been put forward. This study can provide guidance for safety design, operation and accident mitigation measures of helium-cooled lead lithium blankets. 相似文献
5.
使用竖直管代替波动管模型开展稳压器波动管竖直管段内空气-水两相逆流限制(CCFL)特性可视化实验研究。实验现象表明:竖直管与上容器接口处的局部CCFL决定了进入竖直管内的液相流量;竖直管内的局部CCFL决定了从竖直管流出的液相流量;两处局部CCFL均随空气流量的增大而增强。在较低气量情况,进入竖直管内的液相能够完全或大部分流出,竖直管内的局部CCFL较弱,上容器和竖直管接口处的局部CCFL在整体CCFL中占主导地位,整体CCFL程度随着上容器液位升高而略有增强。在高气量情况,从上容器进入竖直管的液相大部分或者完全被限制而不能向下流出,竖直管内的局部CCFL强烈,在整体CCFL中占主导地位,整体CCFL特性不受上容器液位变化的影响。通过实验数据拟合得到了新的稳压器竖直管CCFL模型。稳压器波动管CCFL数据和稳压器竖直管CCFL数据基本重合,表明波动管CCFL主要由CCFL-U决定。 相似文献
6.
7.
8.
Co-doping effects of (Al,Ti, Mg) on the microstructure and electrical behavior of ZnO-based ceramics
Qianying Sun Guorong Li Tian Tian Jiangtao Zeng Kunyu Zhao Liaoying Zheng Maud Barré Jens Dittmer Francois Gouttenoire Anthony Rousseau Abdel Hadi Kassiba 《Journal of the American Ceramic Society》2020,103(5):3194-3204
Co-doped ZnO-based ceramics using Al, Ti, and Mg ions in different ratios were synthesized with the objective to investigate the doping effects on the crystalline features, microstructure and the electrical behavior. For Al and Ti doping, a coexistence of crystalline phases was shown with a major wurtzite ZnO structure and secondary spinel phases (ZnAl2O4, Zn2TiO4, or ZnaTibAlcOd), while Mg doping did not alter significantly the structural features of the wurtzite ZnO phase. The electrical behavior induced by Al, Ti, and Mg co-doping in different ratios was investigated using Raman, electron paramagnetic resonance (EPR) and 27Al and 67Zn solid-state nuclear magnetic resonance (NMR). Al doping induces a high electrical conductivity compared to other doping elements. In particular, shallow donors from Zni-AlZn defect structures are inferred from the characteristic NMR signal at about 185 ppm; that is, quite far from the usual oxygen coordinated Al. The Knight shift effect emanating from a highly conducting Al-doped ZnO ceramics was considered as the origin of this observation. Oppositely, as Ti doping leads to the formation of secondary spinel phases, EPR analysis shows a high concentration of Ti3+ ions which limit the electrical conductivity. The correlation between the structural features at the local order, the involved defects and the electrical behavior as function of the doping process are discussed. 相似文献
9.
河北省某碱性长石花岗岩铷矿,稀有金属以铷为主,伴生有锂、铯、铌、钽。铷和铯以类质同象的形式赋存于钾长石和铁锂云母中,锂主要以铁锂云母形式存在。铌钽主要以独立矿物存在于铌钽铁矿中。采用"弱磁-强磁-浮选云母-长石石英分离"的联合选矿工艺流程,最终可获得Nb_2O_5品位3 241g/t、Ta_2O_5品位1 091g/t、Nb_2O_5回收率54.32%、Ta_2O_5回收率45.45%的铌钽铁精矿。Rb_2O品位11 941g/t、Li_2O品位25 220g/t、Cs_2O品位2 265g/t、Rb_2O回收率28.51%、Li_2O回收率75.89%、Cs_2O回收率54.77%的云母精矿。Rb_2O品位2 276g/t、Rb_2O回收率54.58%的长石精矿以及SiO_2品位98%以上的石英精矿。回收铷等稀有金属矿的同时,云母、长石、石英亦得到了分选回收与综合利用。 相似文献
10.