全文获取类型
收费全文 | 19383篇 |
免费 | 1844篇 |
国内免费 | 1023篇 |
专业分类
电工技术 | 1299篇 |
综合类 | 1701篇 |
化学工业 | 2197篇 |
金属工艺 | 1197篇 |
机械仪表 | 1574篇 |
建筑科学 | 1668篇 |
矿业工程 | 671篇 |
能源动力 | 529篇 |
轻工业 | 2084篇 |
水利工程 | 431篇 |
石油天然气 | 796篇 |
武器工业 | 265篇 |
无线电 | 2174篇 |
一般工业技术 | 1176篇 |
冶金工业 | 1167篇 |
原子能技术 | 223篇 |
自动化技术 | 3098篇 |
出版年
2024年 | 68篇 |
2023年 | 203篇 |
2022年 | 597篇 |
2021年 | 780篇 |
2020年 | 618篇 |
2019年 | 349篇 |
2018年 | 414篇 |
2017年 | 575篇 |
2016年 | 473篇 |
2015年 | 898篇 |
2014年 | 1216篇 |
2013年 | 1487篇 |
2012年 | 1974篇 |
2011年 | 2045篇 |
2010年 | 1853篇 |
2009年 | 1778篇 |
2008年 | 1700篇 |
2007年 | 1500篇 |
2006年 | 1122篇 |
2005年 | 682篇 |
2004年 | 448篇 |
2003年 | 273篇 |
2002年 | 159篇 |
2001年 | 111篇 |
2000年 | 86篇 |
1999年 | 60篇 |
1998年 | 179篇 |
1997年 | 142篇 |
1996年 | 111篇 |
1995年 | 60篇 |
1994年 | 44篇 |
1993年 | 46篇 |
1992年 | 20篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 33篇 |
1976年 | 74篇 |
1975年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
A novel CdS/CaFe2O4 (CS/CFO) heterogeneous p-n junction was created by thermal deposition of CaFe2O4 nanoparticles on CdS rods. The CS/CFO hetero-structured photocatalysts exhibited increasingly efficient visible light harvesting compared to the bare CdS. The CS/CFO composites also presented higher photocurrent and slower decay of photoluminescence, suggesting a better separation of the photo-generated electrons and holes. The photocatalytic H2 evolution quantity on the optimized CS/CFO composite from water in the presence of ethanol was up to 2200 μmol after 3-h visible light illumination, which is more than twice that of the pristine CdS. The chemical interaction between CdS and CaFe2O4 was confirmed by the shifts in the XPS peaks, which made it possible for the charge carriers to transfer across the p-n junction interface. This research highlights the importance of forming an interfacial p-n heterojunction between two semiconductors for efficient charge separation and improved photocatalytic performance. 相似文献
3.
Jieyi Yu Xianguo Liu Rui Su Xuefeng Zhang Xinglong Dong 《Ceramics International》2021,47(17):23950-23957
Increasing the dielectric loss capacity plays an important role in enhancing the electromagnetic absorption performance of materials. It remains a challenge to simultaneously introduce multiple types of dielectric losses in the material. In this work, we show that the atomic and interfacial dipole polarizations can be simultaneously enhanced by substituting N species into both carbon coating layers and bulk TiC lattices of a core-shell TiC@C material. Additionally, substitution of N species results more exposed TiC(111) facets and refines the TiC grain sizes in the bulk material, which is beneficial for enhancing the scattering of the external electromagnetic waves. The maximum reflection loss of the N substituted TiC@C material is measured as ?47.1 dB with an effective absorbing bandwidth of 4.83 GHz at 1.9 mm, which illustrates a valuable way to further tuning the electromagnetic absorption performance of this type of materials. 相似文献
4.
6.
Yuxi Guo Xuefeng Chen Pin Gong Fuxin Chen Dandan Cui Mengrao Wang 《International Journal of Food Science & Technology》2021,56(10):4970-4982
In vitro digestion models are widely used to study the structural changes, digestion and release of food components under simulated gastrointestinal conditions. As compared to the in vivo digestion tests, the in vitro digestion reflects the digestion and utilisation of food after ingestion and has the advantages of being time consuming, inexpensive, reproducible and free from moral and ethical restrictions. This study reviewed the current research studies on the in vitro simulated digestion of polysaccharides conducted in the last 5 years and focused on the oral, gastric and intestinal digestion models, with the aim of providing a basis for the further testing of changes in the content, structure and active ingredients of polysaccharides before and after digestion. 相似文献
7.
8.
9.
基于DTW改进算法的孤立词识别系统的仿真与分析 总被引:5,自引:0,他引:5
传统的DTW算法在进行孤立词语音识别时着重于时间规整和语音测度的计算,而没有对数据的可靠性和有效性进行分析。本文提出了一种改进的端点检测算法,并采用一种改进的DTW算法,在计算机上进行了仿真。实验结果表明采用改进后的DTW算法有效的降低了识别时间和存储数据量,提高了系统性能。 相似文献
10.
Feng Juanni Guo Xuefeng Xu Chunjie Zhang Zhongming 《中国稀土学报(英文版)》2006,24(1):120-120
As-east mierostruetures and their distribution of Mg-Zn-Y ternary alloy with high magnesium, low zinc and yttrium were examined using Nikon Epiphot optical microscopy (OM), RigakuD/max-3C X- ray diffraetion (XRD), and JEOL JSM-6700F scanning electron microscopy (SEM) equipped with an energydispersive X-ray spectroscopy (EDS). In the as-east mierostructures, Yttrium and zinc tend to segregate at grain boundaries, 相似文献