全文获取类型
收费全文 | 198903篇 |
免费 | 19871篇 |
国内免费 | 12774篇 |
专业分类
电工技术 | 31932篇 |
技术理论 | 9篇 |
综合类 | 19112篇 |
化学工业 | 11529篇 |
金属工艺 | 7823篇 |
机械仪表 | 18088篇 |
建筑科学 | 18413篇 |
矿业工程 | 8936篇 |
能源动力 | 6488篇 |
轻工业 | 7832篇 |
水利工程 | 7208篇 |
石油天然气 | 7934篇 |
武器工业 | 3040篇 |
无线电 | 14871篇 |
一般工业技术 | 9959篇 |
冶金工业 | 9123篇 |
原子能技术 | 1513篇 |
自动化技术 | 47738篇 |
出版年
2024年 | 411篇 |
2023年 | 2508篇 |
2022年 | 4352篇 |
2021年 | 5335篇 |
2020年 | 6178篇 |
2019年 | 4835篇 |
2018年 | 4244篇 |
2017年 | 6016篇 |
2016年 | 6653篇 |
2015年 | 7309篇 |
2014年 | 13441篇 |
2013年 | 11609篇 |
2012年 | 14712篇 |
2011年 | 15732篇 |
2010年 | 11886篇 |
2009年 | 12134篇 |
2008年 | 11761篇 |
2007年 | 14453篇 |
2006年 | 12939篇 |
2005年 | 11300篇 |
2004年 | 9364篇 |
2003年 | 8245篇 |
2002年 | 6627篇 |
2001年 | 5491篇 |
2000年 | 4779篇 |
1999年 | 3748篇 |
1998年 | 2845篇 |
1997年 | 2427篇 |
1996年 | 1995篇 |
1995年 | 1692篇 |
1994年 | 1437篇 |
1993年 | 1041篇 |
1992年 | 821篇 |
1991年 | 631篇 |
1990年 | 497篇 |
1989年 | 427篇 |
1988年 | 296篇 |
1987年 | 186篇 |
1986年 | 132篇 |
1985年 | 125篇 |
1984年 | 171篇 |
1983年 | 127篇 |
1982年 | 126篇 |
1981年 | 84篇 |
1980年 | 67篇 |
1979年 | 65篇 |
1978年 | 51篇 |
1977年 | 49篇 |
1964年 | 27篇 |
1959年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(85):36216-36231
The fuel cell/battery durability and hybrid system stability are major considerations for the power management of fuel cell hybrid electric bus (FCHEB) operating on complicated driving conditions. In this paper, a real time nonlinear adaptive control (NAC) with stability analyze is formulated for power management of FCHEB. Firstly, the mathematical model of hybrid power system is analyzed, which is established for control-oriented design. Furthermore, the NAC-based strategy with quadratic Lyapunov function is set up to guarantee the stability of closed-loop power system, and the power split between fuel cell and battery is controlled with the durability consideration. Finally, two real-time power management strategies, state machine control (SMC) and fuzzy logic control (FLC), are implemented to evaluate the performance of NAC-based strategy, and the simulation results suggest that the guaranteed stability of NAC-based strategy can efficiently prolong fuel cell/battery lifespan and provide better fuel consumption economy for FCHEB. 相似文献
2.
《Journal of dairy science》2022,105(11):8621-8637
Lactobacillus reuteri fortified camel milk infant formula (CMIF) was produced. The effect of encapsulation in different matrices (sodium alginate and galacto-oligosaccharides) via spray drying, simulated infant gastrointestinal digestion (SIGID), and storage conditions (temperature and humidity) on the viability of L. reuteri in CMIF and the physicochemical properties of CMIF were evaluated. Compared with free cells, probiotic cell viability was significantly enhanced against SIGID conditions upon encapsulation. However, L. reuteri viability in CMIF decreased after 60 d of storage, predominantly at higher storage humidity and temperature levels. At the end of the storage period, significant changes in the color values were observed in all CMIF, with a reduction in their greenness, an increase in yellowness, and a wide variation in their whiteness. Moreover, pH values and caking behavior of all CMIF stored at higher temperature (40°C) and humidity [water activity (aw) = 0.52] levels were found to be significantly higher than the samples stored under other conditions. Over 30 d of storage at lower humidity conditions (aw = 0.11 and 0.33) and room temperature (25°C), no significant increase in CMIF lipid oxidation rates was noted. Fourier-transform infrared spectroscopy analysis showed that, compared with the other storage conditions, CMIF experienced fewer changes in functional groups when stored at aw = 0.11. Microscopic images showed typical morphological characteristics of milk powder, with round to spherical-shaped particles. Overall, camel milk fortified with encapsulated L. reuteri can be suggested as a promising alternative in infant formula industries, potentially able to maintain its physicochemical characteristics as well as viability of probiotic cells when stored at low humidity levels (aw = 0.11) and temperature (25°C), over 60 d of storage. 相似文献
3.
高面板坝的变形对面板的安全运行有着特别重要的影响,国内外已建的高面板坝工程中,因坝体变形大导致防渗面板挤压破损,坝体渗漏量大的实例较多,不得不降低水库水位进行修复处理,造成较大的经济损失乃至给大坝的长期运行留下安全隐患。通过发生挤压破损的实例分析,发现变形控制缺乏系统性是发生面板挤压破损的主要因素,为预防面板破损,系统提出了“控制坝体总变形,转化有害变形,适应纵向变形”的坝体变形控制方法,并在使用软硬岩混合料筑坝的董箐面板堆石坝中得到的应用,取得了良好效果,该工程运行至今达十余年,未见面板有挤压破损迹象,该方法对建设200 m以上乃至300 m级超高面板坝具有重要借鉴意义。 相似文献
4.
5.
《Ceramics International》2022,48(1):754-759
Thermal control coatings (TCCs) are an essential part of the thermal control systems in the spacecraft. Solar absorptance and emittance are the key performance parameters of TCCs. To develop an ultra-low solar absorption and stable inorganic TCCs for surface radiator, different TCCs were prepared by co-sintering ZnO and SiO2 nanoparticles to form Zn2SiO4/SiO2 pigment in this work, and the optical properties and radiation stability were systematically studied. It is found that the coating based on composite pigment has high reflectivity in the ultraviolet band and excellent optical performance possessing the low solar absorption of 0.06. In addition, the Zn2SiO4/SiO2 coating demonstrates the highest proton and electron radiation stability because that SiO2 between Zn2SiO4 particles acts as the relaxation center of the defects caused by radiation. 相似文献
6.
《International Journal of Hydrogen Energy》2022,47(94):40099-40115
In order to reveal the mechanism of water fog explosion suppression and research the combined effect of water fog and obstacle on hydrogen/air deflagration, multiple sets of experiments were set up. The results show that the instability of thermal diffusion under lean combustion conditions is the main influencing factor of hydrogen/air flame surface instability, and the existence of water fog will aggravate the hydrogen/air flame surface instability. When obstacle is not considered, 8 μm, 15 μm, 30 μm water fog can significantly reduce the flame velocity and explosion overpressure of hydrogen/air, 45 μm fine water fog plays the opposite role. When considering the relative position of the water fog release position and the obstacle, the 8 μm, 15 μm, 30 μm water fog has almost no suppression effect when released near the obstacle, but a significant suppression effect occur, when using the 45 μm water fog. In the field of theoretical research, the research results not only provide an experimental basis for the fine water fog to reduce the consequences of hydrogen explosion accidents, and the optimal diameter range used by the water fog, but also provide experimental reference for the numerical simulation of hydrogen/air explosion suppression in semi-open space, and promote the development of hydrogen explosion suppression theory. In terms of engineering applications, this study can provide a theoretical basis for the layout of fire fighting equipment in the engine room of nuclear power plants or hydrogen-powered ships. 相似文献
7.
现代战场中的无线通信设备日益增多,精准获取个体信息已成为研究热点,但也是难点。针对通信电台,提出了一种分选识别技术。该技术从电台物理层特性出发,对其辐射信号的细微特征进行K-means聚类以实现分选,分选的同时提取各个个体的特征属性值,未知信号通过与特征属性值相关运算实现个体识别。该技术无需先验知识,无需训练运算,通过实验验证,其可行、高效,易于工程实现。 相似文献
8.
9.
随着社会的进步和发展,计算机网络通信技术已被应用到实际生活、生产的各个方面,对人们的生活、生产等产生了深刻的影响。为此,文章就计算机通信及网络远程控制技术在实际生活中的应用问题进行了探究,旨在借助先进科技促进社会实现更优质发展。 相似文献
10.
《Ceramics International》2022,48(24):36860-36870
For the advantages of high-temperature resistance, corrosion resistance and ultra-high hardness, SiCf/SiC composite is becoming a preferred material for manufacturing aero-engine parts. However, the anisotropy and heterogeneity bring great challenges to the processing technology. In this study, a nanosecond pulsed laser is applied to process SiCf/SiC composite, where the influence of the scanning speed and laser scanning direction to the SiC fibers on the morphology of ablated grooves is investigated. The surface characteristics after ablation and the involved chemical reaction of SiCf/SiC are explored. The results show that the increased laser scanning speed, accompanied by the decreasing spot overlap rate, leads to the less accumulation of energy on the material surface, so the ablation effect drops. In addition, for the anisotropy of the SiCf/SiC material, the obtained surface characteristics are closely dependent on the laser scanning direction to the SiC fibers, resulting in different groove morphology. The element composition and phase analysis of the machined surface indicate that the main deposited product is SiO2 and the carbon substance. The results can provide preliminary technical support for controlling the machining quality of ceramic matrix composites. 相似文献