全文获取类型
收费全文 | 36112篇 |
免费 | 3982篇 |
国内免费 | 2466篇 |
专业分类
电工技术 | 844篇 |
综合类 | 1844篇 |
化学工业 | 8163篇 |
金属工艺 | 3185篇 |
机械仪表 | 1089篇 |
建筑科学 | 2272篇 |
矿业工程 | 709篇 |
能源动力 | 1384篇 |
轻工业 | 1438篇 |
水利工程 | 259篇 |
石油天然气 | 263篇 |
武器工业 | 473篇 |
无线电 | 4062篇 |
一般工业技术 | 13672篇 |
冶金工业 | 1961篇 |
原子能技术 | 342篇 |
自动化技术 | 600篇 |
出版年
2024年 | 167篇 |
2023年 | 883篇 |
2022年 | 920篇 |
2021年 | 1345篇 |
2020年 | 1590篇 |
2019年 | 1383篇 |
2018年 | 1257篇 |
2017年 | 1362篇 |
2016年 | 1316篇 |
2015年 | 1333篇 |
2014年 | 1916篇 |
2013年 | 2112篇 |
2012年 | 2276篇 |
2011年 | 3030篇 |
2010年 | 2156篇 |
2009年 | 2337篇 |
2008年 | 2096篇 |
2007年 | 2411篇 |
2006年 | 2100篇 |
2005年 | 1980篇 |
2004年 | 1566篇 |
2003年 | 1400篇 |
2002年 | 1128篇 |
2001年 | 821篇 |
2000年 | 749篇 |
1999年 | 509篇 |
1998年 | 484篇 |
1997年 | 336篇 |
1996年 | 278篇 |
1995年 | 216篇 |
1994年 | 223篇 |
1993年 | 160篇 |
1992年 | 128篇 |
1991年 | 131篇 |
1990年 | 117篇 |
1989年 | 97篇 |
1988年 | 44篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 34篇 |
1983年 | 19篇 |
1982年 | 28篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1963年 | 2篇 |
1955年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
J. Lub W.P.M. Nijssen R.T. Wegh J.P.A. Vogels A. Ferrer 《Advanced functional materials》2005,15(12):1961-1972
This paper describes the synthesis of photoisomerizable derivatives of isosorbide. These derivatives contain a stilbene or cinnamate moiety and can therefore be used as photoisomerizable chiral compounds in cholesteric liquid‐crystalline mixtures. The reflection wavelength of cholesteric layers made from these mixtures is increased by UV irradiation due to the fact that the Z‐isomers of these derivatives exhibit a lower helical twisting power than the corresponding E‐isomers. The cinnamate derivatives are very suitable for use in cholesteric color filters that find application in liquid‐crystal displays. 相似文献
52.
53.
54.
55.
The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0.0015% at 1073K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523-723K for 1h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet. 相似文献
56.
部分种子成分的特征X射线在等效生物材料中衰减的测定 总被引:6,自引:5,他引:1
用Si(Li)探测器实现了Na、Mg、S、Cl的特征X射线在有机膜中的相对衰减以及与O、K元素的特征X射线能量相当的X射线或轫致辐射在有机膜中的相对衰减,分别得出了它们减的数学描述,并把实验得到不同能量的X射线在有机膜中的质量吸收系数与Berkeley的OCG软件计算出的结果相比,相关都小于30%。 相似文献
57.
This two-part paper presents a closed-form procedure for evaluation of estimates of local thermomechanical stress fields in two-phase fibrous composites and laminates. The first part is concerned with a unidirectional elastic laminate subjected to uniform mechanical loads and to uniform changes in temperature. Both phases are assumed to be elastic, with temperature-dependent moduli and expansion coefficients; the solution reflects the influence of thermomechanical interactions. Exact solutions are not possible for any real system, because the local geometry is not known in detail. Instead, estimates of the fields are found from a modified Mori-Tanaka approximation. Examples are presented for two SiC/Ti---Al---Nb composites. Local stresses of interest are found after cooling from fabrication to room temperature. The presence of local yielding, and the influence of coupling terms on the local stress magnitudes are examined. Extension of the results to laminated plates is presented in Part II (Dvorak, G.J., Chen, T. & Teply, J., Composites Science and Technology, 43 (1992) 359–368, this issue). 相似文献
58.
本文根据90年代以来新材料技术的新进展,高度概括地评述了世界新材料技术发展的新趋势,以期对跟踪世界高新技术提供依据。 相似文献
59.
A. Stein 《Advanced materials (Deerfield Beach, Fla.)》2003,15(10):763-775
This report highlights developments in the fields of microporous and mesoporous materials that were published mostly during the year 2002. Selected examples are provided to illustrate new zeolite structures, porous coordination materials, mesoporous solids with new compositions, controlled morphologies, and increased hydrothermal and thermal stabilities, as well as porous solids with tunable pore openings or other structural features that can be dynamically modified. A number of applications are discussed, including stabilization of reactive guests, separations, electronic materials, and sensors. 相似文献
60.
材质对蜂窝纸板缓冲性能的影响 总被引:2,自引:1,他引:1
对两种不同材质的蜂窝纸板静态应力应变性能和动态缓冲结果进行了比较分析。讨论了蜂窝纸板力学性能对应变速度的敏感性及两种纸板的缓冲性能差异。缓冲试验结果表明。在不同的冲击应变率下蜂窝纸板的材质影响蜂窝纸板缓冲性能。 相似文献