全文获取类型
收费全文 | 7436篇 |
免费 | 894篇 |
国内免费 | 145篇 |
专业分类
电工技术 | 50篇 |
综合类 | 345篇 |
化学工业 | 4756篇 |
金属工艺 | 122篇 |
机械仪表 | 102篇 |
建筑科学 | 132篇 |
矿业工程 | 31篇 |
能源动力 | 80篇 |
轻工业 | 937篇 |
水利工程 | 11篇 |
石油天然气 | 53篇 |
武器工业 | 18篇 |
无线电 | 392篇 |
一般工业技术 | 1306篇 |
冶金工业 | 75篇 |
原子能技术 | 22篇 |
自动化技术 | 43篇 |
出版年
2024年 | 36篇 |
2023年 | 135篇 |
2022年 | 101篇 |
2021年 | 303篇 |
2020年 | 277篇 |
2019年 | 261篇 |
2018年 | 311篇 |
2017年 | 295篇 |
2016年 | 299篇 |
2015年 | 336篇 |
2014年 | 350篇 |
2013年 | 526篇 |
2012年 | 454篇 |
2011年 | 447篇 |
2010年 | 359篇 |
2009年 | 397篇 |
2008年 | 328篇 |
2007年 | 408篇 |
2006年 | 484篇 |
2005年 | 354篇 |
2004年 | 352篇 |
2003年 | 311篇 |
2002年 | 250篇 |
2001年 | 184篇 |
2000年 | 164篇 |
1999年 | 119篇 |
1998年 | 128篇 |
1997年 | 94篇 |
1996年 | 64篇 |
1995年 | 52篇 |
1994年 | 56篇 |
1993年 | 43篇 |
1992年 | 43篇 |
1991年 | 53篇 |
1990年 | 32篇 |
1989年 | 31篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有8475条查询结果,搜索用时 15 毫秒
71.
以纳米尺度的镍粉为催化剂,使乙炔气体在高温下热解,制备了纳米碳纤维,利用透电子显微镜对样品的形貌和结构进行了观察研究,讨论了纳米碳纤维的形成机制。 相似文献
72.
Bo Qiao Di Zhou Zhenyu Dai Weikang Zhao Qiming Yang Yanan Xu Xiangjie Li Jun Wu Shuquan Guo Dianming Jiang 《Advanced functional materials》2019,29(22)
Bone plates have been applied to fix fractures for over a hundred years. Metal plates are the gold standard. However, an increasing number of clinical practices and animal experiments have shown that metal plates have had incidents of failure due to their rigid fixation and long‐term complications. Degradable composites present the advantages of a lower elastic modulus and absorbable properties but are unsuitable for load‐bearing applications. Nondegradable bone plates composed of a nanohydroxyapatite/polyamide 66/glass fiber (n‐HA/PA66/GF) composite are prepared, which have enough strength and a low elastic modulus for an internal fixation device. To better assess its function as a bone plate, animal experiments are conducted using a canine load‐bearing femur fracture model. The results show that the n‐HA/PA66/GF plate can fix fractures effectively. Gross observation, radiographic films, and histological analysis all show that the n‐HA/PA66/GF plate leads to a secondary (indirect) union with obvious callus formation, whereas the titanium plate leads to primary (direct) union due to rigid fixation. Furthermore, the histological results reveal that new bone grows at the interface and that the n‐HA/PA66/GF plate can integrate with native bone tissue. Consequently, the n‐HA/PA66/GF composite shows good potential as a bone plate to fix loading‐bearing bone fractures. 相似文献
73.
Marc-Joseph Antonini Atharva Sahasrabudhe Anthony Tabet Miriam Schwalm Dekel Rosenfeld Indie Garwood Jimin Park Gabriel Loke Tural Khudiyev Mehmet Kanik Nathan Corbin Andres Canales Alan Jasanoff Yoel Fink Polina Anikeeva 《Advanced functional materials》2021,31(43):2104857
Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical, and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low-loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here, two fabrication approaches are introduced: 1) an iterative thermal drawing with a soft, low melting temperature (Tm) metal indium, and 2) a metal convergence drawing with traditionally non-drawable high Tm metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low-impedance metallic electrodes and low-loss waveguides, capable of recording optically-evoked and spontaneous neural activity in mice over several weeks. These fibers are coupled with a light-weight mechanical microdrive (1 g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, the compatibility of these fibers with magnetic resonance imaging is demonstrated and they are applied to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber-based neural probes in neuroscience and neuroengineering. 相似文献
74.
75.
介绍了基于少模光纤(FMF)的MDM技术和基于涡旋光纤的OAM复用技术的研究背景与最新研究进展,并对其原理和理论模型进行概述,讨论了OAM模式的生成方式、OAM复用技术和模分复用的特点,并对这两种技术面临问题的解决方法和复用技术的发展方向提出了一些思路。 相似文献
76.
普通单模光纤中光孤子传输问题的研究 总被引:1,自引:0,他引:1
在使用普通单模光纤的光孤子传输系统中,放大器自发辐射(ASE)噪声和色散波逸出是限制光孤子传输的两个主要因素,它们将引起孤子能量科动和定时抖动,从而导致系统误码。本文分别研究了带限光滤波器对ASE噪声的抑制和非线性增益对色散波的抑制以及对孤子传输系统的稳定作用,并设计了使用普通单模光纤的光孤子传输系统。 相似文献
77.
78.
近年来欧美等地出现了许多从铁道、石油、电力等工业起家的新的电信运营者,它们的发展经历了大规模兴建光纤网、组建宽带IP网、提供多样化业务三步曲。传统的电信运营公司则通过重新部署战略重点进行转轨以成为全方位的业务提供者。但新、老运营者在网络发展上均趋于新一代宽带IP网,业务发展重点则转向基于Internet的增值业务。 相似文献
79.
镀银导电纤维的研制与开发 总被引:7,自引:0,他引:7
本文介绍了有关聚酯镀银导电纤维的研制方法,聚酯纤维经过除油、粗化等工序后,浸没有特殊设计的氧化-还原熔注体系中,经热处理后纤维表面就覆盖了一层薄薄的银层。纤维的地率S迅速增加,可达到10^2S/cm以上。为了有利于产业化生产,镀银摈弃了传统的烧杯模式,采用了连续化过程。最近采用放大后的设备已成功地实现了镀银导电纤维的产业化生产。 相似文献
80.
Maoxin Chen Lei Wang Xinghao Sheng Tao Wang Jian Zhou Shengyang Li Xiaohua Shen Meng Zhang Qiusheng Zhang Xinzhi Yu Jian Zhu Bingan Lu 《Advanced functional materials》2020,30(40)
Potassium‐ion hybrid capacitors (PIHCs) show great potential in large‐scale energy storage due to the advantages of electrochemical capacitors and potassium‐ion batteries. However, their development remains at the preliminary stage and is mainly limited by the kinetic imbalance between the two electrodes. Herein, an architecture of NbSe2 nanosheets embedded in N, Se co‐doped carbon nanofibers (NbSe2/NSeCNFs) as flexible, free‐standing, and binder‐free anodes for PIHCs is reported. The NbSe2/NSeCNFs with hierarchically porous structure and N, Se co‐doping afford highly efficient channels for fast transportation of potassium ions and electrons during repeated cycling process. Furthermore, excellent electrochemical reversibility of the NbSe2/NSeCNFs electrode is demonstrated through in situ XRD, in situ Raman, ex situ transmission electron microscopy and element mapping. Thus, PIHCs with the NbSe2/NSeCNFs anode and active carbon cathode achieve a high energy of 145 W h kg?1 at a current density of 50 mA g?1, as well as an ultra‐long cycle life of over 10 000 cycles at a high current density of 2 A g?1. These results indicate that the assembled PIHCs display great potential for applications in the field of ultra‐long cycling energy storage devices. 相似文献