全文获取类型
收费全文 | 4335篇 |
免费 | 327篇 |
国内免费 | 71篇 |
专业分类
电工技术 | 140篇 |
综合类 | 88篇 |
化学工业 | 926篇 |
金属工艺 | 162篇 |
机械仪表 | 171篇 |
建筑科学 | 153篇 |
矿业工程 | 43篇 |
能源动力 | 313篇 |
轻工业 | 409篇 |
水利工程 | 45篇 |
石油天然气 | 25篇 |
武器工业 | 15篇 |
无线电 | 409篇 |
一般工业技术 | 910篇 |
冶金工业 | 285篇 |
原子能技术 | 34篇 |
自动化技术 | 605篇 |
出版年
2024年 | 17篇 |
2023年 | 98篇 |
2022年 | 222篇 |
2021年 | 277篇 |
2020年 | 216篇 |
2019年 | 201篇 |
2018年 | 225篇 |
2017年 | 207篇 |
2016年 | 208篇 |
2015年 | 149篇 |
2014年 | 234篇 |
2013年 | 351篇 |
2012年 | 244篇 |
2011年 | 287篇 |
2010年 | 199篇 |
2009年 | 172篇 |
2008年 | 164篇 |
2007年 | 158篇 |
2006年 | 116篇 |
2005年 | 94篇 |
2004年 | 75篇 |
2003年 | 70篇 |
2002年 | 81篇 |
2001年 | 51篇 |
2000年 | 48篇 |
1999年 | 45篇 |
1998年 | 56篇 |
1997年 | 47篇 |
1996年 | 42篇 |
1995年 | 35篇 |
1994年 | 18篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 26篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1976年 | 14篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有4733条查询结果,搜索用时 15 毫秒
1.
2.
Chattopadhyay Arup Kumar Nag Amitava Singh Jyoti Prakash 《Multimedia Tools and Applications》2022,81(24):34969-34999
Multimedia Tools and Applications - A secret sharing scheme partitions a secret into a set of shares and distributes them among the eligible participants, with each participant receiving one share... 相似文献
3.
Kalli Sai Bhavani Tummala Anusha Pradeep Kumar Brahman 《International Journal of Hydrogen Energy》2021,46(13):9199-9214
In the present study, we report an eco-friendly and simple route to design and synthesize novel nanocomposite catalyst based on platinum nanoparticles anchored on binary support of graphitic carbon nitride (g-C3N4) and cobalt-metal-organic framework (ZIF-67). For this purpose, ZIF-67 was prepared by precipitation method and g-C3N4 was prepared through thermal polymerization method. Later, ZIF-67 and g-C3N4 were hybridized through sonication to get homogeneous g–C3N4–ZIF-67 nanocomposite support material. Platinum nanoparticles (PtNPs) were uniformly deposited on g–C3N4–ZIF-67 by an electrochemical method. The as-developed nanocatalyst was characterized by morphological, structural and electrochemical techniques. The electrocatalytic activity of PtNPs@g–C3N4–ZIF-67 nanocatalyst towards butanol oxidation was evaluated via CV, CA, LSV and EIS in an alkaline medium. Results revealed that the proposed catalyst showed greatly enhanced electrooxidation of butanol in terms of high magnificent current density, lower oxidation potential, excellent long-term stability, large surface area, low charge transfer resistance and less toxic ability. Enhanced catalytic performance of the proposed catalyst could be ascribed to the synergistic effect of g–C3N4–ZIF-67 nanocomposite and PtNPs. The PtNPs@g–C3N4–ZIF-67 catalyst holds promising potential applications to be used as an anodic electrocatalyst for the development of high-performance alkaline fuel cells. 相似文献
4.
Wireless Personal Communications - In this paper, cooperative communication (CC) assisted cognitive wireless sensor network (CWSN) is presented for monitoring health and activity of an end-user in... 相似文献
5.
6.
P. Sampath Brijesh Kakarla Raghava Reddy C. Venkata Reddy Nagaraj P. Shetti Raghavendra V. Kulkarni Anjanapura V. Raghu 《化学工程与技术》2020,43(7):1240-1248
Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency. 相似文献
7.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献
8.
9.
This paper presents the design criteria, procedure, and implementation of a soft-switched power-factor-correction (PFC) circuit based on the extended-period quasi-resonant (EPQR) principles. All power electronic devices including switches and diodes in the circuit are fully soft switched. The design method is demonstrated in a prototype circuit. The operating principles are confirmed with computer simulation and experimental results. A comparison of the EP-QR operation and zero-voltage-transition (ZVT) pulse-width modulation (PWM) method 相似文献
10.
U. Rambabu N. R. Munirathnam T. L. Prakash B. Vengalrao S. Buddhudu 《Journal of Materials Science》2007,42(22):9262-9266
High purity gallium oxide nanopowders have been synthesized by using a simple precipitation technique with calcination at
elevated temperature. From the X-ray pattern, the phase purity of the synthesized powders was confirmed as β-Ga2O3. Elemental quantification (stoichiometry) of Ga2O3 was also examined from the X-ray energy dispersive analysis (EDAX). Based on the recorded Fourier Transform Infrared (FTIR)
spectrum of Ga2O3, the IR bands due to Ga–O bond and crystal lattice vibrations have been identified in the wavenumber range 400–4,000 cm−1. From the measured SEM images, it is obvious to notice that the pH value has been playing a dominant role in obtaining morphologically
different gallium oxide nanopowders. Thermogravimetric analysis reveals 8.3% of weight loss when the sample was heated to
the temperature of 1,100 °C from the room temperature, which also shows a crystalline phase transformation. It is very interesting
to report that a broad blue emission at 455 nm has been measured from the synthesized gallium oxide nanopowders. 相似文献