全文获取类型
收费全文 | 153837篇 |
免费 | 17334篇 |
国内免费 | 11675篇 |
专业分类
电工技术 | 13812篇 |
技术理论 | 2篇 |
综合类 | 15372篇 |
化学工业 | 19627篇 |
金属工艺 | 10871篇 |
机械仪表 | 10989篇 |
建筑科学 | 11601篇 |
矿业工程 | 6275篇 |
能源动力 | 4403篇 |
轻工业 | 13967篇 |
水利工程 | 4568篇 |
石油天然气 | 6494篇 |
武器工业 | 2463篇 |
无线电 | 16651篇 |
一般工业技术 | 14011篇 |
冶金工业 | 6436篇 |
原子能技术 | 2439篇 |
自动化技术 | 22865篇 |
出版年
2024年 | 526篇 |
2023年 | 2238篇 |
2022年 | 5129篇 |
2021年 | 6951篇 |
2020年 | 5069篇 |
2019年 | 3753篇 |
2018年 | 3952篇 |
2017年 | 4694篇 |
2016年 | 4270篇 |
2015年 | 6748篇 |
2014年 | 8406篇 |
2013年 | 9883篇 |
2012年 | 12747篇 |
2011年 | 13268篇 |
2010年 | 12592篇 |
2009年 | 12002篇 |
2008年 | 12062篇 |
2007年 | 11588篇 |
2006年 | 10177篇 |
2005年 | 8171篇 |
2004年 | 6218篇 |
2003年 | 4900篇 |
2002年 | 4888篇 |
2001年 | 4334篇 |
2000年 | 3001篇 |
1999年 | 1624篇 |
1998年 | 720篇 |
1997年 | 615篇 |
1996年 | 514篇 |
1995年 | 399篇 |
1994年 | 296篇 |
1993年 | 222篇 |
1992年 | 170篇 |
1991年 | 138篇 |
1990年 | 119篇 |
1989年 | 89篇 |
1988年 | 66篇 |
1987年 | 55篇 |
1986年 | 44篇 |
1985年 | 19篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 31篇 |
1979年 | 19篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1959年 | 21篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
72.
73.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献
74.
The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath. In this paper, the phase shift characteristics of electromagnetic wave propagation in plasma were investigated. Firstly, the impact factors of phase shift including electron density,collision frequency and incident frequency were discussed. Then, the plasma with different electron density distribution profiles were employed to investigate the influence on the phase shift characteristics. In a real case, the plasma sheath around the hypersonic vehicle will affect and even break down the communication. Based on the hypersonic vehicle model, we studied the electromagnetic wave phase shift under different flight altitude, speed, and attack angle. The results indicate that the phase shift is inversely proportional to the flight altitude and positively proportional to the flight speed and attack angle. Our work provides a theoretical guidance for the further research of phase shift characteristics and parameters inversion in plasma. 相似文献
75.
Muhammad Sheeraz Mamoon Ur Rashid Asad Ali Fazli Akram Ho Jeong Lee Jin San Choi Jong-Seong Bae Yong Soo Kim Young-Han Shin Chang Won Ahn Tae Heon Kim 《Journal of the European Ceramic Society》2021,41(10):5155-5162
We demonstrate the structural evolution of polymorphic phases in Al2O3-inserted SrMnO3 ceramics synthesized by solid state reaction. While the 4H-hexagonal phase is predominant in pure SrMnO3 ceramics, a small amount of 6H-hexagonal polymorph is identified in addition to the primary 4H-hexagonal SrMnO3 and the secondary hexagonal SrAl2O4 phases in the as-sintered ceramics, evidenced by x-ray diffraction and subsequent Rietveld refinement analyses. The existence of the 6H-hexagonal SrMnO3 phase is corroborated using Raman spectroscopy. The chemical compositions and electronic structures of the Al2O3-inserted SrMnO3 compounds are also examined using energy dispersive spectroscopy and x-ray photoelectron spectroscopy, respectively. The first-principles calculations reveal that there is no clear difference between the total energies of 4H- and 6H-hexagonal polymorphs regardless of the presence/absence of Sr and oxygen vacancies. Possible origins are discussed with the estimation of actual strain based on the refined lattice parameter of 6H SrMnO3. 相似文献
76.
设计了基于Web的3D模型浏览与交互系统,主要采用基于WebGL的第三方库Three.js来实现。该系统的建立主要包括场景的构建、场景的交互控制和模型的云存储。模型是场景构建的前提,用户可从外部导入所需模型或利用系统自带的简单模型进行模型的构建。场景交互技术主要包括模型的平移、旋转、缩放、拾取、剖切、3D动画模型的播放以及信息的显示等。模型的云存储是指用户可以通过登录账户将3D模型存储到服务器,日后需要时直接从服务器中加载即可。 相似文献
77.
78.
79.
共价有机框架材料(COFs)是一类由共价键连接的多孔晶态材料。因具有单体链接方式灵活、结构可调、活性位点丰富、比表面积大、理化性质相对稳定等特点,它们在气体储存与分离、能量储存、催化和光电学领域受到了广泛的关注。本文主要从结构设计、合成方法及功能化、材料的分析表征和晶形控制等方面概括地介绍了COFs材料。在此基础上,综述了COFs材料在关键核素分离方面的研究进展,并展望了其在核素分离领域的应用前景和今后的研究方向。 相似文献
80.