全文获取类型
收费全文 | 55982篇 |
免费 | 5514篇 |
国内免费 | 2699篇 |
专业分类
电工技术 | 3569篇 |
技术理论 | 8篇 |
综合类 | 3672篇 |
化学工业 | 9561篇 |
金属工艺 | 2962篇 |
机械仪表 | 3307篇 |
建筑科学 | 4030篇 |
矿业工程 | 1534篇 |
能源动力 | 1777篇 |
轻工业 | 3637篇 |
水利工程 | 1151篇 |
石油天然气 | 2854篇 |
武器工业 | 651篇 |
无线电 | 7038篇 |
一般工业技术 | 6854篇 |
冶金工业 | 2917篇 |
原子能技术 | 708篇 |
自动化技术 | 7965篇 |
出版年
2024年 | 268篇 |
2023年 | 957篇 |
2022年 | 1889篇 |
2021年 | 2568篇 |
2020年 | 1902篇 |
2019年 | 1596篇 |
2018年 | 1748篇 |
2017年 | 1886篇 |
2016年 | 1670篇 |
2015年 | 2335篇 |
2014年 | 2760篇 |
2013年 | 3506篇 |
2012年 | 3630篇 |
2011年 | 3822篇 |
2010年 | 3347篇 |
2009年 | 3247篇 |
2008年 | 3126篇 |
2007年 | 2950篇 |
2006年 | 2980篇 |
2005年 | 2473篇 |
2004年 | 1854篇 |
2003年 | 1617篇 |
2002年 | 1671篇 |
2001年 | 1530篇 |
2000年 | 1317篇 |
1999年 | 1333篇 |
1998年 | 1159篇 |
1997年 | 989篇 |
1996年 | 799篇 |
1995年 | 670篇 |
1994年 | 495篇 |
1993年 | 429篇 |
1992年 | 329篇 |
1991年 | 266篇 |
1990年 | 183篇 |
1989年 | 180篇 |
1988年 | 144篇 |
1987年 | 86篇 |
1986年 | 88篇 |
1985年 | 77篇 |
1984年 | 33篇 |
1983年 | 27篇 |
1982年 | 37篇 |
1981年 | 34篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Bin Zhang Meng Zhang Yu Li Huansheng Cheng Jianming Zheng 《Ceramics International》2019,45(3):3081-3087
Proton induced X-ray emission (PIXE) technique and factor analysis were used to study the recovery of making-technology of Chinese Longquan celadon made in the late Southern Song Dynasty (1127–1279 CE). Based on factor analysis, for the raw material for body and the recipe for glaze, there is a close but slightly different relationship between these Longquan celadons unearthed from the core area of Dayao and the non-core area, despite all the Longquan celadons belong to the high-calcium-glaze system. The chemical compositions of most of the tentative body and glaze samples are very close to those of Longquan celadons unearthed from the core area of Dayao and the non-core area. This study can provide a guidance for recovery of making-technology of Longquan celandon. 相似文献
32.
33.
A novel bio‐based phthalonitrile resin derived from catechin: synthesis and comparison of curing behavior with petroleum‐based counterpart 下载免费PDF全文
Yu Qi Zhihuan Weng Jinyan Wang Shouhai Zhang Lishuai Zong Cheng Liu Xigao Jian 《Polymer International》2018,67(3):322-329
The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry 相似文献
34.
35.
测向误差的减小一直以来都是无线电测向精度提高的一个难点,对于不同的测向体制所采用的减小测向误差的方法都不尽相同。本文主要介绍的是相关干涉仪测向体制的基本原理以及通过内插法的应用来减小测向误差的方法。 相似文献
36.
The support flux was first investigated as a separate influencing factor for its effect on performances of ceramic filtration membranes. Three pre-membranes were prepared by tape-casting and then transfer-coated to supports to form dual-layer ceramic membranes after sintering. Experiments demonstrated that membrane layers with almost the same properties were obtained despite the huge difference in support flux. When the support flux increases from 3.120 to 97.53 m3m?2h?1, the flux of these three membrane series have increased by 75%, 186% and 228%, respectively. Experimental rules can provide structural design and evaluation from the perspective of permeability. The limit membrane flux of a certain system was derived according to the resistance distribution law of internal membrane structure and the Darcy's theorem. On this basis, a method for designing support flux was proposed. Furthermore, we present a criterion to quickly and easily evaluate the match between the support and the top layer, which is the ratio of membrane resistance to total resistance. Finally, the filtration resistance of penetration caused by suction of membrane particles into the support was measured for the first time, taking the advantage of the transfer-coating method that inherently free of penetration. Our works are expected to deepen the understanding of the ceramic membrane structure and provided guidance for its rational design and optimization. 相似文献
37.
38.
40.
Hechun Cao Hui Zheng Lining Fan Zifeng Cheng Jianwei Zhou Qiong Wu Peng Zheng Liang Zheng Yang Zhang 《International Journal of Applied Ceramic Technology》2020,17(2):813-822
In this study, yttrium iron garnet co-doped with Zn and Zr atoms with a chemical formula Y3ZnxZrxFe(5−2x)O12 (x = 0.0-0.3) has been successfully prepared by the solid-state reaction method. The effects of doping concentration on the microstructure, crystal structure, magnetic properties, and dielectric properties of Y3ZnxZrxFe(5−2x)O12 were investigated. The microstructure analysis indicates that co-doping of YIG with Zn and Zr can effectively reduce the grain size of the ceramic. The crystal structure results reveal that the doping concentration of Zn–Zr has substantial influence on the lattice parameters of YIG, such as, increases the lattice constant, crystal cell size, and interplanar spacing. However, the second phase of ZrO2 appears once x ≥ 0.15. Additionally, the dielectric properties of YIG ferrite can be regulated using this Zn–Zr co-doping method. Zn–Zr co-doping can improve the dielectric stability and reduce the dielectric loss at high temperature. The magnetization measurement shows that the saturation magnetization is stabilized at x < 0.15, and the magnetic loss is decreased with the increase in the doping concentration. Overall, the findings show that the ceramic with x = 0.1 exhibits better properties included high saturation magnetization (24.607 emu/g), low magnetic loss (0.0025 @ 1 MHz), and relatively low dielectric loss (496 @ 400°C). 相似文献