全文获取类型
收费全文 | 78109篇 |
免费 | 8630篇 |
国内免费 | 4986篇 |
专业分类
电工技术 | 6184篇 |
技术理论 | 6篇 |
综合类 | 6813篇 |
化学工业 | 11704篇 |
金属工艺 | 4313篇 |
机械仪表 | 5322篇 |
建筑科学 | 6627篇 |
矿业工程 | 2412篇 |
能源动力 | 2695篇 |
轻工业 | 6783篇 |
水利工程 | 1976篇 |
石油天然气 | 3125篇 |
武器工业 | 955篇 |
无线电 | 8828篇 |
一般工业技术 | 8324篇 |
冶金工业 | 2962篇 |
原子能技术 | 1141篇 |
自动化技术 | 11555篇 |
出版年
2024年 | 324篇 |
2023年 | 1275篇 |
2022年 | 2678篇 |
2021年 | 3697篇 |
2020年 | 2627篇 |
2019年 | 2106篇 |
2018年 | 2254篇 |
2017年 | 2529篇 |
2016年 | 2273篇 |
2015年 | 3321篇 |
2014年 | 4146篇 |
2013年 | 4907篇 |
2012年 | 5780篇 |
2011年 | 5853篇 |
2010年 | 5623篇 |
2009年 | 5495篇 |
2008年 | 5530篇 |
2007年 | 5094篇 |
2006年 | 4902篇 |
2005年 | 3954篇 |
2004年 | 2827篇 |
2003年 | 2173篇 |
2002年 | 2320篇 |
2001年 | 1969篇 |
2000年 | 1730篇 |
1999年 | 1370篇 |
1998年 | 911篇 |
1997年 | 777篇 |
1996年 | 709篇 |
1995年 | 535篇 |
1994年 | 483篇 |
1993年 | 332篇 |
1992年 | 300篇 |
1991年 | 218篇 |
1990年 | 156篇 |
1989年 | 141篇 |
1988年 | 90篇 |
1987年 | 69篇 |
1986年 | 57篇 |
1985年 | 38篇 |
1984年 | 23篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 8篇 |
1976年 | 4篇 |
1970年 | 2篇 |
1959年 | 10篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
31.
Xiaohu Ren Xilou Pu Hongfeng Yin Yun Tang Hudie Yuan Huiqing Fan 《Ceramics International》2021,47(9):12122-12129
Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo2Fe16O27 is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications. 相似文献
32.
33.
Xiao-Ya Shangguan Bao-Lun Fang Chen-Xiao Xu Yuan Tan Yan-Gang Chen Zhi-Jun Xia Wei Chen 《Ceramics International》2021,47(5):6318-6328
A series of direct Z-scheme FeIn2S4/Bi2WO6 hierarchical heterostructures with intimate interface contacts were synthesized by in-situ growth route and characterized by systematical analyses. All as-prepared FeIn2S4/Bi2WO6 nanocomposites showed significantly enhanced photocatalytic activity towards photodegradation for the removal of tetracycline hydrochloride (TCH) in comparison with individual FeIn2S4 and Bi2WO6. Meanwhile, the highest photocatalytic degradation activity can be achieved by modulating adding amount of FeIn2S4 in FeIn2S4/Bi2WO6 nanocomposites and the optimized component ratio of FeIn2S4 to Bi2WO6 is determined to be 10 wt%. The enhanced photocatalytic activity could be ascribed to efficient separation between photogenerated holes and electrons based on the construction of direct Z-scheme system. The high photocatalytic stability of resultant 10 wt% FeIn2S4/Bi2WO6 nanocomposites was revealed through six successive recycling reactions. The main intermediate generated during TCH photodegradation was explored by HPLC-MS. Besides, the direct Z-scheme photocatalytic mechanism was confirmed by band position analysis, electron spin resonance (ESR) and active species capture experiment. 相似文献
34.
35.
Debin Wang Jingsong Liu Mengshi Zeng Chunmei Zhang Huiqin Li Hongtao Yu Ying Yuan Shuren Zhang 《Journal of the American Ceramic Society》2019,102(7):4029-4037
(1-x)Sr0.7Pb0.15Bi0.1TiO3-xBi4Ti3O12 ((1-x)SPBT-xBIT, x = 0-0.125) bulk ceramics were developed and calcined via the solid-state method, aimed at the application of pulsed power capacitors. The phase structures, temperature stability, hysteresis loop, and discharge properties were systematically investigated. Considering both the temperature stability and dielectric properties, 0.925SPBT-0.075BIT bulk ceramics with a capacitance variation satisfying the X7R specification were developed for pulsed power capacitors. The energy storage density was 0.252 J/cm3, and the ceramics showed high temperature stability at 80 kV/cm. The discharge current waveforms of the 0.925SPBT-0.075BIT ceramics were recorded. A high discharge power density of approximately 1.01 × 108 W/kg with an 8 Ω load resistor and short discharge period of 84 ns were achieved at 50 kV/cm. The good temperature stability properties and high power density show that the 0.925SPBT-0.075BIT ceramics are well suited for pulsed power capacitors with a wide temperature range. 相似文献
36.
黄浦江为感潮河流,低潮位重现期的确定对黄浦江航道的设计具有重要意义。为了准确估计黄浦江低潮位的重现期,以黄浦江下游吴淞口站年最低潮位序列为例,在对样本进行三性审查的基础上,分别采用传统的数理统计方法和时变矩方法进行水文频率分析。结果表明:吴淞口站年最低潮位序列在1996年发生了变异;还现修正后的序列服从位置参数线性时变的GEV模型,低潮位存在缓慢的上升趋势;一致性条件下百年一遇低潮位约为0.261 m,在非一致性条件下其重现期增大为150 a。非一致性条件下的重现期增大说明黄浦江现有的航道设计标准偏安全,航道通航保证率提高。 相似文献
37.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
38.
39.
Multimedia Tools and Applications - In Wyner-Ziv (WZ) video coding, decoder side information (SI) takes a key role in a WZ video codec among other building blocks. In this paper, we review the... 相似文献
40.