全文获取类型
收费全文 | 11899篇 |
免费 | 1302篇 |
国内免费 | 649篇 |
专业分类
电工技术 | 215篇 |
综合类 | 978篇 |
化学工业 | 1023篇 |
金属工艺 | 2713篇 |
机械仪表 | 3278篇 |
建筑科学 | 978篇 |
矿业工程 | 538篇 |
能源动力 | 195篇 |
轻工业 | 321篇 |
水利工程 | 192篇 |
石油天然气 | 514篇 |
武器工业 | 146篇 |
无线电 | 119篇 |
一般工业技术 | 1830篇 |
冶金工业 | 484篇 |
原子能技术 | 66篇 |
自动化技术 | 260篇 |
出版年
2024年 | 63篇 |
2023年 | 229篇 |
2022年 | 319篇 |
2021年 | 394篇 |
2020年 | 412篇 |
2019年 | 418篇 |
2018年 | 460篇 |
2017年 | 530篇 |
2016年 | 510篇 |
2015年 | 490篇 |
2014年 | 577篇 |
2013年 | 716篇 |
2012年 | 746篇 |
2011年 | 767篇 |
2010年 | 569篇 |
2009年 | 650篇 |
2008年 | 511篇 |
2007年 | 801篇 |
2006年 | 779篇 |
2005年 | 629篇 |
2004年 | 622篇 |
2003年 | 443篇 |
2002年 | 306篇 |
2001年 | 323篇 |
2000年 | 316篇 |
1999年 | 240篇 |
1998年 | 199篇 |
1997年 | 168篇 |
1996年 | 146篇 |
1995年 | 137篇 |
1994年 | 69篇 |
1993年 | 59篇 |
1992年 | 64篇 |
1991年 | 40篇 |
1990年 | 31篇 |
1989年 | 23篇 |
1988年 | 35篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
91.
92.
Effects of sintering pressure and temperature on microstructure and tribological characteristic of Cu-based aircraft brake material 总被引:3,自引:0,他引:3
A novel Cu-based P/M aircraft brake material was prepared and the effects of sintering pressure and temperature on microstructure and tribological characteristic were investigated. For the constant sintering temperature, when the sintering pressure increases from 0.5 MPa to 1.5 MPa, the porosity, wear loss and friction coefficient decrease remarkably. When the sintering pressure increases from 1.5 MPa to 2.5 MPa, the porosity further decreases but in a little degree and wear behaviors are improved slightly. However, once the sintering pressure is larger than 2.5 MPa, it has no obvious effect on microstructure and tribological characteristic. For the constant sintering pressure, when the sintering temperature increases from 900 ℃ to 930 ℃, the sintered density remarkably-increases, and wear behaviors are obviously improved. For further increasing sintering temperature to l 000 ℃, the density keeps on increasing, but wear behaviors change slightly. 相似文献
93.
摩擦焊机可编程控制系统的研制 总被引:2,自引:1,他引:2
介绍了C609型可编程序控制器对摩擦焊工艺程序的控制以及对焊机检测电路、保护电路的控制,包括摩擦焊工艺流程逻辑图、PC的硬件接口及软件编程等,该PC系统结构简单,操作及修改程序容易,可靠性强,控制功能及精度亦优于原系统。 相似文献
94.
95.
1.~nonNUInericalmodellingbythefiniteelement(FE)methodhasbecomeaneffectiveandeconomyicmeansforsimulatingmetalfoeingprocesses.However,accuratemodellingdemandsthecorrectdefinitionandinputsofthedataforthethermalandphysicalpIDPertiesoftheworkpieceandtoolmaterials,theboUndaryconditionsattheworkpiece--toolinterfaceandinotherareas,inadditiontoappropriatemeshgenerationandnumericalsolutions.Althoughmostofthematerialdataareavailable,thedataforinterfacialheattransferandfrictionconditions,Whichhavesubst… 相似文献
96.
ZHU Xianfang ZHANG Lide Institute of Solid State Physics Academia Sinica Hefei China Research Assistant Institute of Solid State Physics Academia Sinica Hefei China 《金属学报(英文版)》1989,2(5):315-319
The characteristics of the low frequency internal friction and the modulus effect associatedwith the non-equilibrium spinodal pretransformation and the following discontinuous trans-formation was investigated in an as-quenched eutectiod Al-Zn alloy.It was observed that theloss of the stability in the lattice,which corresponded to the large-amplitude long-wavelengthstatic concentration wave in the non-equilibrium spinodal pretransformation,did not induceany effect of localized soft modulus.Although there are two aging internal friction peaks inphase transformation which correspond to the appearance and disappearance of the coherencyin spinodal pretransformation and the maximum of the interface area in the discontinuoustransformation respectively,the effect of localized soft modulus did not take place yet. 相似文献
97.
By use of X-ray diffractometry and scanning electron microscope(SEM),the friction and wear results obtained from MM-1000 dynamometer tests of CVI pitch/resin C/C composites were analyzed.By investigating the factors that affected the friction and wear properties,such as matrix carbon,applcation environment,graphitization degree and brake pressure,etc,friction and wear mechanism of carbon materials were probed.The results indicate that pitch densified CVI initially treated composite is more graphitizable with its graphitization degree up 59 62%,and which results in uniform small debris easier to generate,more smooth friction curves with the coefficient of 0.3-0.4 and relatively higher wear and mass loss,compared with CVI/resin C/C composites.It was further proved by SEM observation that tribological behavior of C/C composite was system dependent.Factors determining the friction and wear properties such as the size of debris and its influence on friction and wear,brake pressure,graphization degree and debris bilm formation interacted and affected each other.The friction and wear mechanism of C/C composites under different high temperature treatments needs further research. 相似文献
98.
100.
几何因素与摩擦耦合对高纯铝箔剪切织构的影响 总被引:5,自引:3,他引:5
采用取向分布函数 (ODF)研究了轧制几何因素、轧制摩擦条件对高纯铝箔轧制织构的影响。结果显示 ,如果轧制摩擦因数大 ,当处于均匀变形几何条件 1相似文献