全文获取类型
收费全文 | 56207篇 |
免费 | 4647篇 |
国内免费 | 3726篇 |
专业分类
电工技术 | 4918篇 |
综合类 | 3754篇 |
化学工业 | 9378篇 |
金属工艺 | 6370篇 |
机械仪表 | 3999篇 |
建筑科学 | 1058篇 |
矿业工程 | 2579篇 |
能源动力 | 1824篇 |
轻工业 | 2926篇 |
水利工程 | 272篇 |
石油天然气 | 1651篇 |
武器工业 | 410篇 |
无线电 | 7330篇 |
一般工业技术 | 12422篇 |
冶金工业 | 2755篇 |
原子能技术 | 843篇 |
自动化技术 | 2091篇 |
出版年
2024年 | 243篇 |
2023年 | 866篇 |
2022年 | 1290篇 |
2021年 | 1577篇 |
2020年 | 1629篇 |
2019年 | 1394篇 |
2018年 | 1454篇 |
2017年 | 1915篇 |
2016年 | 1948篇 |
2015年 | 1972篇 |
2014年 | 2722篇 |
2013年 | 3224篇 |
2012年 | 3606篇 |
2011年 | 4293篇 |
2010年 | 3029篇 |
2009年 | 3279篇 |
2008年 | 3020篇 |
2007年 | 3764篇 |
2006年 | 3512篇 |
2005年 | 2972篇 |
2004年 | 2579篇 |
2003年 | 2280篇 |
2002年 | 1913篇 |
2001年 | 1661篇 |
2000年 | 1500篇 |
1999年 | 1188篇 |
1998年 | 1028篇 |
1997年 | 892篇 |
1996年 | 721篇 |
1995年 | 644篇 |
1994年 | 567篇 |
1993年 | 462篇 |
1992年 | 338篇 |
1991年 | 242篇 |
1990年 | 179篇 |
1989年 | 176篇 |
1988年 | 113篇 |
1987年 | 72篇 |
1986年 | 47篇 |
1985年 | 44篇 |
1984年 | 52篇 |
1983年 | 33篇 |
1982年 | 50篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
薄膜磁头磁轭制备工艺研究 总被引:1,自引:1,他引:0
本文重点讨论了用不同的工艺方法来制备薄膜磁头中的关键元件-磁轭。采用多次光刻的方法克服湿法工艺中磁性膜NiFe层的侧向钻蚀问题,从而实现对磁轭几何尺寸的精确控制,并对几种工艺方法的优缺点作了比较详细的分析。 相似文献
103.
厚膜导体Pd-Ag/Au、Pt-Pd-Au/Au平面复合结构,Pd-Ag/Au立体复合结构可使多种组装技术相互兼容。立体复合结构还可有效地降低导体线电阻,减少线损耗。而且,其超声键合性尤佳 相似文献
104.
Fusae Nakanishi 《Polymer International》1992,27(3):237-241
Preparation of photoreactive Langmuir-Blodgett (LB) films was carried out using polymers/oligomers prepared from long-chain dialkyl esters of di-and tetra-olefins and having cyclobutane rings in the main chain. These polymers/oligomers formed stable monolayers on a water surface when mixed with arachidic acid. These monolayers could be deposited onto a substrate successfully forming Y-type films. The oligomer LB films were polymerized on irradiation. The polymer LB films showed a photo-reversible process between polymers and oligomers, depending on wavelength of the irradiating light. On the basis of spectral data and molecular weight change, this behaviour was found to be caused by cleavage and formation of cyclobutane rings. 相似文献
105.
Poly(N-vinyl-carbazole) (PVK) thin films doped with bromine has been studied by scanning electron microscopy, X-ray diffraction, infrared absorption, X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), optical transmission (visible, near ultra violet) and conductivity measurements. The polymer has been doped at room temperature and at 373 K. It is shown by ESR, XPS and optical measurements that a charge transfer complex (CT-complex) is formed between PVK and Br. However, if some bromine acts as dopant of the polymer there is another bromine contribution, which corresponds to bromine covalently bonded to PVK and some only adsorbed. It is also shown by ESR that there is not only polymer doping by bromine but also some partial polymer degradation. Therefore, it can be said that the optimum doping condition of PVK thin films with bromine has been shown to be room temperature post-doping. 相似文献
106.
In the absence of a bulk diffusion effect, it is shown for the first time that the impedance spectra for the chlorine evolution reaction on a rotating thin ring electrode comprise three consecutive semicircles in the capacitive half of the complex plane. The first (highest frequency) semicircle is due to the charge-transfer resistance for chloride discharge and the simultaneous chlorine adsorption coupled to the double-layer capacitance. The second semicircle (around 5 Hz) is due to the adsorption and desorption of a chlorine intermediate. The third (lowest frequency, around 0.5 Hz) semicircle is due to the relaxation of surface oxygen species. The impedance data allow the steps of the overall reaction to be examined individually. On a Pt surface the rate of chloride discharge and simultaneous chlorine adsorption (the admittance of the first semicircle) is first order with respect to chloride concentration and has a potential-dependence close to 58 mV/decade. The rate of the adsorption and desorption process (the admittance of the second semicircle) is second order with respect to chloride concentration, and has a potential dependence close to 30 mV/decade. The time constant for the adsorption/desorption processes is ca 20 ms, independent of electrode potential in the range studied. These features are consistent with a mechanism in which a faster discharge reaction (Cl− Clad + e) is followed by a slower surface combination reaction (2Clad → Cl2), but inconsistent with mechanisms in which ion + atom desorption is predominant, the initial chloride discharge is slow, or a unipositively charged chlorine species is involved. 相似文献
107.
The synthesis of rare-earth perovskite-type composition thin films of LaNiO3 by means of the inorganic-sol-gel (ISG) method was studied. The structural stability under high temperature in reducing atmospheres and the oxygen-sensitivity mechanism of the LaNiO3 thin films were examined. It is shown that under the experimental conditions, LaNiO3 decomposes and the valance states of nickel are +2 and +3. 相似文献
108.
用磁控溅射方法制备了系列 (Fe0 .86 Zr0 .0 33Nb0 .0 33B0 .0 6 8Cu0 .0 1 ) x(Al2 O3) 1 -x颗粒膜样品 ,体积百分比x从 0 .3 3~ 0 .63 ,样品厚度约为10 0nm。室温下在Fe0 .86 Zr0 .0 33Nb0 .0 33B0 .0 6 8Cu0 .0 1 体积百分比x =0 .43时得到 17.5 μΩ·cm的最大饱和霍耳电阻率 ,比纯铁磁金属提高了 3~ 4个量级。对其磁性和微结构进行了研究 ,样品霍耳电阻率随外场的变化曲线 ρxy~H与磁场平行于膜面时的磁化曲线M~H有相似性 ,说明霍尔电阻率 ρxy与磁化强度M相关。样品电阻率 ρxx随金属体积百分比x的减小而增加 ,在x =0 .43附近发生突变 ,从金属导电变为绝缘体。根据微结构和输运性质对可能的机制进行了探讨 相似文献
109.
110.