全文获取类型
收费全文 | 6221篇 |
免费 | 853篇 |
国内免费 | 461篇 |
专业分类
电工技术 | 557篇 |
综合类 | 521篇 |
化学工业 | 901篇 |
金属工艺 | 474篇 |
机械仪表 | 486篇 |
建筑科学 | 520篇 |
矿业工程 | 246篇 |
能源动力 | 192篇 |
轻工业 | 514篇 |
水利工程 | 159篇 |
石油天然气 | 402篇 |
武器工业 | 76篇 |
无线电 | 560篇 |
一般工业技术 | 572篇 |
冶金工业 | 382篇 |
原子能技术 | 64篇 |
自动化技术 | 909篇 |
出版年
2024年 | 41篇 |
2023年 | 106篇 |
2022年 | 255篇 |
2021年 | 385篇 |
2020年 | 249篇 |
2019年 | 193篇 |
2018年 | 188篇 |
2017年 | 227篇 |
2016年 | 176篇 |
2015年 | 278篇 |
2014年 | 305篇 |
2013年 | 372篇 |
2012年 | 452篇 |
2011年 | 491篇 |
2010年 | 457篇 |
2009年 | 429篇 |
2008年 | 412篇 |
2007年 | 424篇 |
2006年 | 393篇 |
2005年 | 260篇 |
2004年 | 195篇 |
2003年 | 134篇 |
2002年 | 132篇 |
2001年 | 164篇 |
2000年 | 156篇 |
1999年 | 97篇 |
1998年 | 80篇 |
1997年 | 87篇 |
1996年 | 91篇 |
1995年 | 67篇 |
1994年 | 43篇 |
1993年 | 33篇 |
1992年 | 38篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 25篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有7535条查询结果,搜索用时 0 毫秒
101.
卜丽娜 《兰州工业高等专科学校学报》2012,(6):112-115
随着信息化、技术化的发展及大学英语教学改革的进程的加快,教师角色亟须转变。基于Web的MCALL模式下的英语写作教学更需要教师转变角色,发挥中介作用。结合高校英语写作教学实践,在教师和学习者中进行了相关调查,分析了角色转变过程中教师对中介角色作用的看法和具体做法及学习者对教师做法的态度。结果得出,绝大部分教师和学习者认同教师的中介作用,但在实践过程中教师的做法与学习者的看法存在差异。 相似文献
102.
103.
104.
105.
106.
稀土和Ca、Mg元素对高强度钢焊接热影响区组织和韧性的影响 总被引:1,自引:0,他引:1
研究了低合金高强度非调质中厚板钢中添加稀土(REM)和Ca、Mg微量元素对大线高能焊接热影响区(HAZ)显微组织微细化和晶内针状铁素体(IAF)形成的影响.结果表明,添加REM和Ca、Mg元素可在钢的HAZ中形成弥散稳定的氧硫化物(CeCa)2O2S和(CeMg)2O2,热轧奥氏体化(1450℃)和焊接热输入10 kJ/mm时都十分稳定,比传统采用TiN强化的钢具有更优良的低温韧性.有效地控制细小弥散的氧硫化合物,能获得适中的奥氏体有效晶粒尺寸和提供HAZ中形成晶内针状铁素体及稳定活性的形核位置.促进晶内铁素体协同形核生长,有效地使得HAZ组织微细化. 相似文献
107.
108.
Solidification structures of high niobium containing TiAl alloys 总被引:1,自引:0,他引:1
JingwenXu JunpinLin YanliWang ZhiLin GuoliangChen 《北京科技大学学报(英文版)》2005,12(2):134-138
To understand the effect of alloy stoichiometry on the microstructural development and mechanical behavior of γ-TiAlbased materials, it is necessary to have a determination of the phase relationships for the TiAl alloy system near the γ phase field.Cast structures and phases of Ti-(43-47)Al-8Nb-(1-2)Mn (at%) alloys have been studied by using scanning electron microscope and X-ray diffraction. Their solidification path and microstructure development during the solidification were analyzed. The experimental results show that the alloys with different Al contents form different macrostructures and microstructural morphologies. This indicates that the solidification paths are different with different Al contents. The alloy with 43Al forms equiaxed grain structure, and the solidification path is as follows: L → L β→β→α β→α β cores →α2 γ B2 cores. Whereas the alloy with 47Al forms columnar grain structure, and the solidification path is as follows: L → L β→α β L →α γ β cores →α2 γ B2 cores. The β phase is their primary solid phase and can be retained to ambient temperature. The alloy with 43Al solidifies completely into β phase. The peritectic reactions L β→α and L α→γ appear when the Al content increases to 47Al. 相似文献
109.
GuoliangChen XidongHui KefuYao HuaiyuHou XiongjunLiu MeilingWang GuangChen 《北京科技大学学报(英文版)》2005,12(2):143-150
The atomic configuration of chemical short-range order (CSRO) for the Zr-base metallic glasses was investigated by using nano-diffraction and high resolution transmission electronic microscopy (HRTEM) technology with a beam size of 0.5 rim. It is illustrated that the pattern of atomic configuration of CSRO might have various compound counterparts because of the chemical interaction of bonding atoms. Some atomic configuration of MCSRO is similar to the icosahedral structure with 10-fold symmetry of very weak spots. In deed, the nano-beam technology could clearly detect the evolution of atomic configuration in nanometer scale during the transformation from the metallic melt to the primary crystallization. The local atomic configuration of CSRO is also investigated by molecular dynamics simulation (MD) for the Zr2Ni compound in a wider temperature range. The CSRO in the melt could be pictorially demonstrated as distorted coordination polyhedron of the compound structure and/or the structure similar to cubo-octahedron analogs. The MD simulation illustrates that the atomic packing of long-range order disappears just above the melting point, but the chemical interaction of bonding atoms still exists that leads to form the various CSRO with the atomic configuration similar to stable or metastable unit cell of Zr2Ni compound. The icosahedral polyhedron became more abundance as the overheating temperature was raised. 相似文献
110.
Jianfeng Gao Xiangjun Xu Junpin Lin Xiping Song Yanli Wang Guoliang Chen 《北京科技大学学报(英文版)》2005,12(6):535-539
The effect of strain rate on the yield strength of high Nb containing TiAl alloy was studied. The results show that the strain rate sensitivity varies with the test temperature, and the yield strength is not sensitive to the strain rate at room temperature but significantly sensitive to the strain rate at high temperature. An increase of the strain rate or a decrease of the temperature results in an obvious change of fracture mode. It is found that the strain rate sensitivity of this alloy varying with temperature is due to the dislocation climb generated at high temperature. 相似文献