全文获取类型
收费全文 | 89135篇 |
免费 | 6914篇 |
国内免费 | 3629篇 |
专业分类
电工技术 | 4442篇 |
技术理论 | 14篇 |
综合类 | 5405篇 |
化学工业 | 15976篇 |
金属工艺 | 4952篇 |
机械仪表 | 5427篇 |
建筑科学 | 7365篇 |
矿业工程 | 2503篇 |
能源动力 | 2559篇 |
轻工业 | 5445篇 |
水利工程 | 1417篇 |
石油天然气 | 5542篇 |
武器工业 | 652篇 |
无线电 | 10366篇 |
一般工业技术 | 11341篇 |
冶金工业 | 4419篇 |
原子能技术 | 991篇 |
自动化技术 | 10862篇 |
出版年
2024年 | 263篇 |
2023年 | 1396篇 |
2022年 | 2316篇 |
2021年 | 3198篇 |
2020年 | 2527篇 |
2019年 | 2235篇 |
2018年 | 2416篇 |
2017年 | 2800篇 |
2016年 | 2470篇 |
2015年 | 3326篇 |
2014年 | 4112篇 |
2013年 | 4990篇 |
2012年 | 5476篇 |
2011年 | 5772篇 |
2010年 | 5121篇 |
2009年 | 4908篇 |
2008年 | 4735篇 |
2007年 | 4712篇 |
2006年 | 4885篇 |
2005年 | 4286篇 |
2004年 | 2943篇 |
2003年 | 2620篇 |
2002年 | 2590篇 |
2001年 | 2288篇 |
2000年 | 2265篇 |
1999年 | 2637篇 |
1998年 | 2299篇 |
1997年 | 1874篇 |
1996年 | 1778篇 |
1995年 | 1404篇 |
1994年 | 1309篇 |
1993年 | 897篇 |
1992年 | 700篇 |
1991年 | 555篇 |
1990年 | 401篇 |
1989年 | 356篇 |
1988年 | 278篇 |
1987年 | 162篇 |
1986年 | 116篇 |
1985年 | 83篇 |
1984年 | 45篇 |
1983年 | 35篇 |
1982年 | 45篇 |
1981年 | 29篇 |
1980年 | 15篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Shanquan Chen Sicong Wei Fei Jin Shanming Ke Xierong Zeng Lang Chen Chuanwei Huang 《Ceramics International》2018,44(12):13695-13698
From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La0.7Sr0.3MnO3 films was studied. High quality La0.7Sr0.3MnO3 films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from ??2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La0.7Sr0.3MnO3 films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La0.7Sr0.3MnO3 films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments. 相似文献
62.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献
63.
64.
本文立足于太赫兹波成像领域近年来备受关注的研究热点—太赫兹波计算鬼成像,首先回顾了鬼成像从量子到经典再到计算的历史过程,然后阐述了计算鬼成像的数学原理,随后综述了计算鬼成像在太赫兹波段的发展历程,及其在超衍射分辨成像、石墨烯光电导成像、太赫兹光谱成像等方面的应用,并在最后展望了太赫兹波计算鬼成像的发展前景:计算鬼成像作为一种成像手段,可以绕开在太赫兹频段缺乏经济高效的焦面阵列式探测器的难题,但目前的成像帧率还难以满足快速成像的应用需求,相信在未来随着器件性能的提升和成像算法的优化,其成像帧率可以得到大幅提升。 相似文献
65.
Shuang Shao Yong Liu Chun-Shui Xu Ying-Xuan Xu Bin Wu Xiao-Shu Zeng Xian-Feng Lu Xiang-Jie Yang 《金属学报(英文版)》2015,(1):7-14
The microstructure and mechanical properties of Mg–6Zn–1Y and Mg–6Zn–3Y(wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing(SDAS) of Mg–6Zn–1Y and Mg–6Zn–3Y is reduced by 32 and 30% with increasing cooling rates(Rc) from 10.2 to 23 K/s, which can be predicted using a empirical model of SDAS=68 R 0:45:45cand SDAS=73 R 0c, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction(Vf) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory. 相似文献
66.
67.
Journal of Mechanical Science and Technology - The idea of integral calculus is used in traditional milling force prediction methods. In the traditional method, the milling cutter is divided into... 相似文献
68.
69.
The red grape berry pigments, anthocyanins, were characterized in the early 20th century, but investigations of wine pigments were stymied during that era. The question of their identity was a major challenge for wine chemists. A number of techniques showed that the pigments were polymeric in nature. Some structures were postulated by mid-century based on reactions between anthocyanins and condensed tannin, and later postulated wine pigments were observed in model reactions. Some related compounds were then observed in wine. By the end of the 20th century, the ionization of non-volatiles for mass spectrometry opened the door to these compounds. In addition, a new class of compounds was observed, the pyranoanthocyanins, a product of fermentation and aging metabolites with anthocyanins. These compounds possess the pigment stability to SO2 and pH change that is characteristic of aged red wine. Aging experiments show a dynamic situation with shifts in the population of pigment classes over time. The very large number of diverse pigments explains why it has been so difficult to answer the century-old question of the structure of wine pigments. Our current understanding is founded on the use of mass spectral analysis using electrospray and related ionization techniques over the last 25 years. Future progress will rely on more sophisticated analysis of this very complex mixture of substances. © 2019 Society of Chemical Industry 相似文献