全文获取类型
收费全文 | 42806篇 |
免费 | 5170篇 |
国内免费 | 2008篇 |
专业分类
电工技术 | 1227篇 |
技术理论 | 8篇 |
综合类 | 2329篇 |
化学工业 | 16597篇 |
金属工艺 | 2904篇 |
机械仪表 | 956篇 |
建筑科学 | 2302篇 |
矿业工程 | 835篇 |
能源动力 | 2675篇 |
轻工业 | 2135篇 |
水利工程 | 291篇 |
石油天然气 | 2191篇 |
武器工业 | 153篇 |
无线电 | 2075篇 |
一般工业技术 | 9560篇 |
冶金工业 | 2799篇 |
原子能技术 | 371篇 |
自动化技术 | 576篇 |
出版年
2024年 | 241篇 |
2023年 | 1032篇 |
2022年 | 1472篇 |
2021年 | 1594篇 |
2020年 | 1654篇 |
2019年 | 1551篇 |
2018年 | 1472篇 |
2017年 | 1681篇 |
2016年 | 1773篇 |
2015年 | 1655篇 |
2014年 | 2466篇 |
2013年 | 2625篇 |
2012年 | 3049篇 |
2011年 | 3459篇 |
2010年 | 2600篇 |
2009年 | 2636篇 |
2008年 | 2064篇 |
2007年 | 2520篇 |
2006年 | 2622篇 |
2005年 | 2141篇 |
2004年 | 1770篇 |
2003年 | 1598篇 |
2002年 | 1252篇 |
2001年 | 888篇 |
2000年 | 805篇 |
1999年 | 616篇 |
1998年 | 539篇 |
1997年 | 378篇 |
1996年 | 336篇 |
1995年 | 276篇 |
1994年 | 251篇 |
1993年 | 182篇 |
1992年 | 149篇 |
1991年 | 117篇 |
1990年 | 107篇 |
1989年 | 62篇 |
1988年 | 44篇 |
1987年 | 48篇 |
1986年 | 32篇 |
1985年 | 57篇 |
1984年 | 46篇 |
1983年 | 45篇 |
1982年 | 25篇 |
1981年 | 4篇 |
1980年 | 13篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1963年 | 1篇 |
1959年 | 5篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
91.
92.
简要介绍了全板电镀镍金加工过程中镀金面发白现象及改善措施。特别是针对高位发白(或粗糙)的产生原因和处理过程进行较为详细的描述,并对工艺在此处理过程中存在问题进行了简要剖析。 相似文献
93.
Woo Yong Sung Seung Min Lee Wal Jun Kim Jong Girl Ok Ho Young Lee Yong Hyup Kim 《Diamond and Related Materials》2008,17(6):1003-1007
Complementary electroplating combined with electrophoresis enhanced the field emission characteristics of emitters by improving the adhesions between CNT emitters and substrate. The emitting current of the CNT emitters prepared by our combined method increased nine times higher than that of CNT emitters prepared by electrophoresis only, since electroplating improved the adhesion of CNT emitters. During the life-time measurement for 10 h, the emitting current of CNT emitters fabricated by electrophoresis only was drastically decreased to 13% of the initial current, while that prepared by the combination of electrophoresis and successive electroplating decreased to 64% of the initial current. We suggest that our method is a promising approach for the efficient fabrication of reliable CNT emitters. 相似文献
94.
The continuous production of hydrogen from cyclohexanes is achieved effectively using Pt/ACF (ACF = activated carbon fiber) catalysts in a fixed-bed flow reactor. The Pt catalysts are more effective than a Pd/ACF catalyst for the reaction. Besides cyclohexane, methylcyclohexane, 1,4-dimethylcyclohexane, and p-menthane can also be employed as hydrogen source in the reaction system. 相似文献
95.
The Wabash River Integrated Methanol and Power Production from Clean Coal Technologies (IMPPCCT) project is investigating an Early Entrance Coproduction Plant (EECP) concept to evaluate integrated electrical power generation and methanol production from coal and other carbonaceous feedstocks. Research, development and testing (RD&T) that is currently being conducted under the project is evaluating cost effective process systems for removing contaminants, particularly sulfur species, from the generated gas which contains mainly synthesis gas (syngas), CO2 and steam at concentrations acceptable for the methanol synthesis catalyst. The RD&T includes laboratory testing followed by bench-scale and field testing at the SG Solutions Gasification Plant located in West Terre Haute, Indiana. Actual synthesis gas produced by the plant was utilized at system pressure and temperature for bench-scale field testing. 相似文献
96.
采用冷柱头进样的高温气相色谱技术,建立了测定高滴熔点微晶蜡中正构和非正构烃类含量及碳数分布的方法。对滴熔点在90℃以下的微晶蜡进行测定。实验表明,使用大口径高温毛细管柱可以分析碳数在72以下的微晶蜡。方法快速,准确,实用性强。 相似文献
97.
98.
无氢类金刚石碳膜的研究进展 总被引:1,自引:0,他引:1
介绍了无氢类金刚石碳膜的制备方法 ,它们的机械、光学、电学性能 ,将无氢与含氢的类金刚石碳膜进行了简单比较 ,总结及探讨了它们的应用 相似文献
99.
Frank J. Owens 《Materials Letters》2007,61(10):1997-1999
Molecular orbital calculations of the ionization potential of single wall carbon nanotubes having donor NH2 and acceptor NO2 groups bonded to the side walls and ends and boron and nitrogen substituted for carbon show substantial increases in ionization potential compared to carbon nanotubes with no functional groups and no carbon substitutions. The presence of a carbon vacancy on the side wall also causes a substantial increase in the ionization potential. The effect of tube length on the ionization energy is also calculated. The calculations also suggest that at appropriate levels of boron and nitrogen doping the armchair carbon nanotubes could be high temperature organic ferromagnetic materials. 相似文献
100.
We report the production of carbon nanotubes by high dose of electron irradiation. The irradiation was performed with a 2 MeV Van de Graaff accelerator, while the irradiation conditions were the following: voltage 1.3 MeV, current 5 µA, dose rate 25 kGy/min, and total dosage 1000 kGy. The samples were analyzed in a high-resolution transmission electron microscope. The main features observed on the samples, were huge nanotubes of several nanometer long and few nanometer wide, which are capped at one end. It is good to point out, that at this level of irradiation, we were not able to find either onion-like or particle structures throughout the material, as it is usual in similar hexagonal structures. This behavior could be attributed to the level of irradiation used to create the nanotubes under investigation. 相似文献