全文获取类型
收费全文 | 4593篇 |
免费 | 82篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 145篇 |
综合类 | 2篇 |
化学工业 | 916篇 |
金属工艺 | 1611篇 |
机械仪表 | 70篇 |
建筑科学 | 46篇 |
矿业工程 | 1篇 |
能源动力 | 136篇 |
轻工业 | 147篇 |
水利工程 | 2篇 |
石油天然气 | 6篇 |
无线电 | 342篇 |
一般工业技术 | 592篇 |
冶金工业 | 460篇 |
原子能技术 | 68篇 |
自动化技术 | 139篇 |
出版年
2022年 | 16篇 |
2021年 | 30篇 |
2020年 | 15篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 29篇 |
2016年 | 41篇 |
2015年 | 28篇 |
2014年 | 73篇 |
2013年 | 175篇 |
2012年 | 156篇 |
2011年 | 163篇 |
2010年 | 126篇 |
2009年 | 170篇 |
2008年 | 187篇 |
2007年 | 160篇 |
2006年 | 153篇 |
2005年 | 116篇 |
2004年 | 111篇 |
2003年 | 143篇 |
2002年 | 164篇 |
2001年 | 157篇 |
2000年 | 125篇 |
1999年 | 153篇 |
1998年 | 267篇 |
1997年 | 233篇 |
1996年 | 184篇 |
1995年 | 124篇 |
1994年 | 123篇 |
1993年 | 186篇 |
1992年 | 176篇 |
1991年 | 150篇 |
1990年 | 69篇 |
1989年 | 62篇 |
1988年 | 47篇 |
1987年 | 38篇 |
1986年 | 54篇 |
1985年 | 47篇 |
1984年 | 56篇 |
1983年 | 37篇 |
1982年 | 28篇 |
1981年 | 32篇 |
1980年 | 23篇 |
1979年 | 45篇 |
1978年 | 21篇 |
1977年 | 20篇 |
1976年 | 25篇 |
1974年 | 14篇 |
1973年 | 15篇 |
1972年 | 15篇 |
排序方式: 共有4683条查询结果,搜索用时 31 毫秒
1.
Koji Morita Byung-Nam Kim Hidehiro Yoshida Keijiro Hiraga Yoshio Sakka 《Journal of the European Ceramic Society》2018,38(6):2588-2595
Carbon contamination from the carbon paper/dies during spark-plasma-sintering (SPS) processing was examined in the MgAl2O4 spinel. The carbon contamination sensitively changes with the heating rate during the SPS processing. At the high heating rate of 100 °C/min, the carbon contamination having organized structures occurred over almost the entire area from the surface to deep inside the SPSed spinel disk. In contrast, at the slow heating rate of 10 °C/min, the carbon contamination having disordered structures occurred only around the surface area. The carbon phases transform into high pressure CO/CO2 gases by post-annealing in air and lead to pore formation along the grain junctions. The pore formation significantly occurs at the high heating rate due to the large amount of the contaminant carbon phases. This suggests that if once the carbon contamination was formed in the materials, it is very difficult to remove the carbon phases from the materials. 相似文献
2.
3.
4.
5.
6.
A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitatite disaturated species
of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted
by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential
refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC.
The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chroamtograms obtained by
RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responsed in the same degree for different, authentic standards
of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human
lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those
reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis
among the molecular species containing disaturated species. 相似文献
7.
H. Okamoto 《Journal of Phase Equilibria and Diffusion》2002,23(4):384-385
8.
9.
1-GHz-spaced 16-channel arrayed-waveguide grating for a wavelength reference standard in DWDM network systems 总被引:3,自引:0,他引:3
We fabricated a 1-GHz-spaced 16-channel arrayed-waveguide grating (AWG) by using a new AWG configuration where the path of each arrayed waveguide winds backward and forward across a 4-in diameter wafer without crossing any other waveguides. The ultra-narrow (< 1 GHz) and stable transmission bands of this AWG can be used to construct a wavelength reference standard covering the S, C, and L bands in the dense wavelength-division-multiplexing network systems whose frequency deviation is /spl plusmn/160 MHz. 相似文献
10.
Wakejima A. Matsunaga K. Okamoto Y. Ando Y. Nakayama T. Miyamoto H. 《Electronics letters》2005,41(25):1371-1372
A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power. 相似文献