全文获取类型
收费全文 | 15462篇 |
免费 | 3242篇 |
国内免费 | 1959篇 |
专业分类
电工技术 | 815篇 |
综合类 | 1503篇 |
化学工业 | 702篇 |
金属工艺 | 483篇 |
机械仪表 | 1264篇 |
建筑科学 | 481篇 |
矿业工程 | 409篇 |
能源动力 | 276篇 |
轻工业 | 366篇 |
水利工程 | 208篇 |
石油天然气 | 176篇 |
武器工业 | 402篇 |
无线电 | 2964篇 |
一般工业技术 | 1407篇 |
冶金工业 | 387篇 |
原子能技术 | 674篇 |
自动化技术 | 8146篇 |
出版年
2024年 | 75篇 |
2023年 | 515篇 |
2022年 | 937篇 |
2021年 | 1009篇 |
2020年 | 795篇 |
2019年 | 605篇 |
2018年 | 524篇 |
2017年 | 570篇 |
2016年 | 694篇 |
2015年 | 802篇 |
2014年 | 1071篇 |
2013年 | 1102篇 |
2012年 | 1254篇 |
2011年 | 1289篇 |
2010年 | 985篇 |
2009年 | 1081篇 |
2008年 | 1060篇 |
2007年 | 1194篇 |
2006年 | 945篇 |
2005年 | 886篇 |
2004年 | 704篇 |
2003年 | 563篇 |
2002年 | 440篇 |
2001年 | 317篇 |
2000年 | 215篇 |
1999年 | 194篇 |
1998年 | 168篇 |
1997年 | 128篇 |
1996年 | 87篇 |
1995年 | 79篇 |
1994年 | 64篇 |
1993年 | 51篇 |
1992年 | 39篇 |
1991年 | 31篇 |
1990年 | 50篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 2篇 |
1964年 | 2篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1959年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
针对目标估计过程需要大量人工参与、自动化程度低的问题,提出了基于数据质量评价的目标估计方法。利用目标数据质量评价方法,对不同传感器得到的目标数据质量进行科学、有效的测度和评价,并根据质量得分动态调整各数据源在目标估计过程中所占的权重,从而减少人工干预,提高目标估计效能。仿真试验结果证明了该方法的有效性。 相似文献
2.
3.
Sk Tanbir Islam Sudip K. Samanta Santanu Das Himadri Chattopadhyay 《Journal of the American Ceramic Society》2022,105(7):4608-4620
The micro-powder injection molding (micro-PIM) process has the potential to bridge the gap between the design and manufacturing of micro-components that are often used in small and handy devices. Numerical modeling helps to analyze and overcome various difficulties of micro-PIM. In the present work, a numerical model is developed to predict the powder–binder separation (a common defect in PIM and especially severe in micro-PIM) during the injection of an alumina feedstock. A powder–binder separation criterion is proposed dealing with applied injection pressure and friction force between the powder and binder. An indirect comparison of feedstock travel time between two locations is used to validate the model. The predicted segregation from the simulated result is supported by a qualitative experimental measurement. The developed model can be used to optimize injection parameters to get a defect-free product. 相似文献
4.
Aiming at the performance degradation of the existing presentation attack detection methods due to the illumination variation, a two-stream vision transformers framework (TSViT) based on transfer learning in two complementary spaces is proposed in this paper. The face images of RGB color space and multi-scale retinex with color restoration (MSRCR) space are fed to TSViT to learn the distinguishing features of presentation attack detection. To effectively fuse features from two sources (RGB color space images and MSRCR images), a feature fusion method based on self-attention is built, which can effectively capture the complementarity of two features. Experiments and analysis on Oulu-NPU, CASIA-MFSD, and Replay-Attack databases show that it outperforms most existing methods in intra-database testing and achieves good generalization performance in cross-database testing. 相似文献
5.
《Current Opinion in Solid State & Materials Science》2022,26(6):101024
One of the main challenges in the laser powder bed fusion (LPBF) process is making dense and defect-free components. These porosity defects are dependent upon the melt pool geometry and the processing conditions. Power-velocity (PV) processing maps can aid in visualizing the effects of LPBF processing variables and mapping different defect regimes such as lack-of-fusion, under-melting, balling, and keyholing. This work presents an assessment of existing analytical equations and models that provide an estimate of the melt pool geometry as a function of material properties. The melt pool equations are then combined with defect criteria to provide a quick approximation of the PV processing maps for a variety of materials. Finally, the predictions of these processing maps are compared with experimental data from the literature. The predictive processing maps can be computed quickly and can be coupled with dimensionless numbers and high-throughput (HT) experiments for validation. The present work provides a boundary framework for designing the optimal processing parameters for new metals and alloys based on existing analytical solutions. 相似文献
6.
7.
8.
《Ceramics International》2022,48(8):11265-11272
Three dimensional silica mesh structures are prepared through a new and simple method for enhancing the quantum dot sensitized solar cells performance and stability.Silica patterns are made on the top of the TiO2 photoanodes and a marked improvement in light scattering properties of meshed structures is confirmed by diffuse reflectance spectroscopy measurements. This improvement enhances the current density and consequently the cells ‘efficiency. Parameters of electron transport in cells are explored by electrochemical impedance spectroscopy (EIS). According to the EIS results, silica mesh declines the recombination rate in cells in a clear way. Here more than 50% efficiency improvement is obtained in meshed structures in comparison to cells with normal TiO2 photoanode structures. The insulated silica mesh, reduces the electrolyte's deleterious effect on the semiconductor layers and the cells’ stability is improved. 相似文献
9.
The combined effect of resistance spot welding and precipitation hardening on the localised corrosion of A286 superalloy is studied. The specimens tested by double loop electrochemical potentiokinetic reactivation were welded in the solution treated condition, and then subjected to different precipitation hardening treatments. For both base metal and weld nugget, the maximum localised corrosion is reached when η phase is clearly observable. The fact that the localised corrosion resistance of weld nugget is different from that shown by base metal may be explained by the segregation of Ni and Ti towards the interdendritic region of weld nugget (studied by using scanning electron microscope/energy dispersive X-ray analysis). 相似文献
10.
针对基于局部熵进行加密图像视觉安全性评估存在块效应的局限性,引入图像的边缘特征,通过共有边缘来衡量加密图像与原始图像的边缘相似度,消除了块效应。由于局部熵对加密等级低的图像不敏感,边缘相似度对加密等级高的图像不敏感,将两个评估方法进行自适应融合,提出[SLEES](Local Entropy and Edge Similarity,[SLEES])指标。通过改变图像像素位置和图像像素值的加密方式处理图像和视频帧进行测试,实验结果表明,[SLEES]指标相比传统评估指标有更好的鲁棒性,评估范围更广。 相似文献