全文获取类型
收费全文 | 1471篇 |
免费 | 66篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 24篇 |
综合类 | 3篇 |
化学工业 | 386篇 |
金属工艺 | 26篇 |
机械仪表 | 37篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 93篇 |
轻工业 | 137篇 |
水利工程 | 5篇 |
石油天然气 | 26篇 |
无线电 | 173篇 |
一般工业技术 | 273篇 |
冶金工业 | 86篇 |
原子能技术 | 8篇 |
自动化技术 | 248篇 |
出版年
2023年 | 20篇 |
2022年 | 35篇 |
2021年 | 66篇 |
2020年 | 48篇 |
2019年 | 52篇 |
2018年 | 68篇 |
2017年 | 54篇 |
2016年 | 69篇 |
2015年 | 42篇 |
2014年 | 50篇 |
2013年 | 115篇 |
2012年 | 62篇 |
2011年 | 81篇 |
2010年 | 75篇 |
2009年 | 48篇 |
2008年 | 40篇 |
2007年 | 59篇 |
2006年 | 37篇 |
2005年 | 32篇 |
2004年 | 19篇 |
2003年 | 21篇 |
2002年 | 25篇 |
2001年 | 29篇 |
2000年 | 16篇 |
1999年 | 15篇 |
1998年 | 38篇 |
1997年 | 12篇 |
1996年 | 24篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1973年 | 11篇 |
1972年 | 7篇 |
排序方式: 共有1549条查询结果,搜索用时 31 毫秒
71.
Omar Arafat Kdudsi Khalil Olga Maria Mascarenhas de Faria Oliveira José Carlos Rebuglio Vellosa Andreza Urba de Quadros Loriangela Marceli Dalposso Thaysa Ksiaskiewcz Karam Rubiana Mara Mainardes Najeh Maissar Khalil 《Food chemistry》2012
The objective of this study was to evaluate the antifungal and antioxidant activities of curcumin, ascorbic acid and the mixture of these two compounds. For the antifungal assay, the minimum inhibitory concentrations (MIC) were determined using Candida strains (ATCC and clinical isolates). Curcumin alone inhibited growth of Candida albicans yeast cells, whereas ascorbic acid did not present effects. However, when the mixture of ascorbic acid and curcumin was assayed to determine the association of the two compounds, the curcumin MIC decreased 5- to 10-fold. In the antioxidant assays, the sum of the alone activities of curcumin and ascorbic acid were lower than the activity of the two-compound mixture. This study highlights the importance of the association between two common antioxidants in foods, to improve the antifungal and antioxidant activities of curcumin (in vitro), and can be applied to Candida spp. infection and diseases associated with oxidative stress. 相似文献
72.
Nazish Jahan Saba Aslam Khalil ur Rahman Tuba Fazal Fareeha Anwar Rubab Saher 《Journal of Experimental Nanoscience》2016,11(1):72-80
Nanotechnology is a promising technique to increase the bioavailability of herbal medicines. This paper presents the nanosuspension approach for increasing the aqueous solubility and thereby bioactivity of important herbal extracts. Nanosuspensions of the seeds of three plants extract (Silybum marianum, Elettaria cardamomum and Coriandrum sativum) were prepared by using polyvinyl alcohol (1.5% w/v) as a stabiliser. Prepared nanoparticles were characterised by scanning electron microscope. Activity of nanosuspension formulation was assessed by using four in vitro antioxidant assays. S. marianum, E. cardamomum and C. sativum particle size was observed to fall in range of 446.1 ± 112.6, 456.63 ± 339.2 and 432.1 ± 172.8 nm, respectively, most of the particles were having spherical shape and smooth topology. These synthesised nanoparticles were found to be more effective against quenching free radical than their crude extracts and standards [butylated hydroxyl toluene and ascorbic acid]. C. sativum nanosuspension showed most free radical scavenging potential against 2,2-diphenyl-1-picrylhdrazyl (DPPH) and superoxide free radical scavenging assays (IC50 0.59 ± 0.01 and 0.81 ± 0.11 mg/ml). S. marianum nanosuspension was found to be most effective against DPPH radicals scavenging (IC50 0.34 ± 0.02 mg/ml). It was concluded that nanosuspension of herbal medicines potentiates the antioxidant potential. 相似文献
73.
Noor-Ul-Ain Babar Yasir Faheem Joya Hassan Khalil Fayyaz Hussain Khurram Saleem Joya 《International Journal of Hydrogen Energy》2021,46(11):7885-7902
Developing only Fe derived bifunctional overall water splitting electrocatalyst both for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) while performing at low onset overpotential and with high catalytic stability is a rare instance. We present here the first demonstration of unique iron-oxide nanobeads (FeOx-NBs) based electrocatalyst executing both OER and HER with high activity. Thin-film electrocatalytic FeOx-NBs assembly is surface grown via simple spray coating (SC). The unique SC/FeOx-NBs propels OER initiating water oxidation just at 1.49 VRHE (η = 260 mV) that is the lowest observable onset potential for OER on simple Fe-oxide based catalytic films reported so far. Catalyst also reveals decently high HER activity and competent overall water splitting performance in the FeOx-NBs two-electrode system as well. Catalyst also presents stable kinetics, with promising high electrochemically active surface area (ECSA) of 1765 cm2, notable Tafel slopes of just 54 mV dec1? (OER) and 85 mV dec1? (HER), high exchange current density of 1.10 mA cm2? (OER), 0.58 mA cm2? (HER) and TOF of 74.29s1?@1.58VRHE, 262s1?@1.62VRHE (OER) and 82.5s1?@-0.45VRHE, 681s1?@-0.56VRHE (HER). 相似文献
74.
Entanglement and Entropy Squeezing for Moving Two Two-Level Atoms Interaction with a Radiation Field
S. Abdel-Khalek E. M. Khalil Beida Alsubei A. Al-Barakaty S. M. Abo Dahab 《计算机、材料和连续体(英文)》2021,66(3):2445-2456
In this paper, we analyzed squeezing in the information entropy, quantum state fidelity, and qubit-qubit entanglement in a time-dependent system. The proposed model consists of two qubits that interact with a two-mode electromagnetic field under the dissipation effect. An analytical solution is calculated by considering the constants for the equations of motion. The effect of the general form of the time-dependent for qubit-field coupling and the dissipation term on the temporal behavior of the qubit-qubit entanglement, quantum state fidelity, entropy, and variance squeezing are examined. It is shown that the intervals of entanglement caused more squeezing for the case of considering the time-dependent parameters. Additionally, the entanglement between the qubits became more substantial for the case of time dependence. Fidelity and negativity rapidly reached the minimum values by increasing the effect of the dissipation parameter. Moreover, the amount of variance squeezing and the amplitude of the oscillations decreased considerably when the time dependence increased, but the fluctuations increased substantially. We show the relation between entropy and variance squeezing in the presence and absence of the dissipation parameter during the interaction period. This result enables new parameters to control the degree of entanglement and squeezing, especially in quantum communication. 相似文献
75.
76.
In this article, the nondestructive eddy current (EC) method was used for microstructural evaluation of Ni-hard4 cast iron (NiHCI). Different destabilizing heat treatments were used to produce different microstructures and hardness. The microstructural analysis and hardness measurement were done for conventional characterization of the reference blocks. Then, the EC techniques were applied to evaluate the hardness and microstructural changes by the detection of EC parameters at different frequencies. Metallurgical investigations showed that increasing the destabilizing soaking time and temperature decreases the amount of retained austenite in NiHCIs. The nondestructive evaluation method (NDT) revealed that it can be good correlated between retained austenite amount and hardness with EC parameters. This shows that the EC technique can detect NiHCIs products according to the metallurgical characterization with good accuracy. 相似文献
77.
Internet of Things for the Future of Smart Agriculture: A Comprehensive Survey of Emerging Technologies
下载免费PDF全文
![点击此处可从《IEEE/CAA Journal of Automatica Sinica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Othmane Friha Mohamed Amine Ferrag Lei Shu Leandros Maglaras Xiaochan Wang 《IEEE/CAA Journal of Automatica Sinica》2021,8(4):718-752
This paper presents a comprehensive review of emerging technologies for the internet of things (IoT)-based smart agriculture. We begin by summarizing the existing surveys and describing emergent technologies for the agricultural IoT, such as unmanned aerial vehicles, wireless technologies, open-source IoT platforms, software defined networking (SDN), network function virtualization (NFV) technologies, cloud/fog computing, and middleware platforms. We also provide a classification of IoT applications for smart agriculture into seven categories: including smart monitoring, smart water management, agrochemicals applications, disease management, smart harvesting, supply chain management, and smart agricultural practices. Moreover, we provide a taxonomy and a side-by-side comparison of the state-of-the-art methods toward supply chain management based on the blockchain technology for agricultural IoTs. Furthermore, we present real projects that use most of the aforementioned technologies, which demonstrate their great performance in the field of smart agriculture. Finally, we highlight open research challenges and discuss possible future research directions for agricultural IoTs. 相似文献
78.
Khan Abdul Manan Yun Deok-won Zuhaib Khalil Muhammad Iqbal Junaid Yan Rui-Jun Khan Fatima Han Changsoo 《International Journal of Control, Automation and Systems》2017,15(2):802-814
International Journal of Control, Automation and Systems - In this paper, we have addressed two issues for upper limb assist exoskeleton. 1) Estimation of Desired Motion Intention (DMI); 2) Robust... 相似文献
79.
Tarak Amine Joseph W. Newkirk Frank Liou 《The International Journal of Advanced Manufacturing Technology》2014,73(9-12):1739-1749
A potential problem in applying the direct laser deposition (DLD) technique to material fabrication is the effect that subsequent deposited layers have on reheating previous laser deposition layers. Most of the previous investigations examined the effect of the laser deposition parameters on the microstructure and mechanical properties of a single layer. This work focused on the effect of the laser parameters of subsequent layers on the microstructure and mechanical properties of the deposited layers to select proper parameters and characterize the effect. The microstructure morphology and property values are affected by the varied parameters. This leads to some tempering and aging effects in the steels. The microstructure of the top layer was equiaxed, while the near substrate region was fine dendritic. Typically, both of the travel speed and power of the laser show the significant effects on microstructure and hardness. 相似文献
80.
In light of current calls by medical professionals to confront the global issue of obesity and related illnesses, we developed a mobile application called STEP UP that monitors physical activity and provides data that can be easily shared within a social network. We then conducted an exploratory, theoretical study based on the theory of reasoned action (TRA) followed by an experimental trial and user study. The purpose of the studies was to explore the effect of persuasive technology on physical activity behavior and to investigate its effectiveness in motivating users to use the technology to be more physically active. The application was found to have a positive effect on the participants and their level of physical activity. They enjoyed using the application and were motivated to walk more, especially when enabled to share their step counts with their friends. The social component of the application clearly enhanced users’ walking experience, as the atmosphere of friendly competition motivated them to walk more. Based on user responses, we conclude that a further enhanced application that includes chat functionality may be even more successful in supporting increased physical activity and thus healthier lifestyle. 相似文献