全文获取类型
收费全文 | 33032篇 |
免费 | 2714篇 |
国内免费 | 1706篇 |
专业分类
电工技术 | 1110篇 |
技术理论 | 1篇 |
综合类 | 2309篇 |
化学工业 | 11262篇 |
金属工艺 | 4786篇 |
机械仪表 | 1021篇 |
建筑科学 | 2067篇 |
矿业工程 | 744篇 |
能源动力 | 1987篇 |
轻工业 | 3160篇 |
水利工程 | 437篇 |
石油天然气 | 1788篇 |
武器工业 | 206篇 |
无线电 | 915篇 |
一般工业技术 | 2978篇 |
冶金工业 | 1635篇 |
原子能技术 | 363篇 |
自动化技术 | 683篇 |
出版年
2024年 | 69篇 |
2023年 | 610篇 |
2022年 | 815篇 |
2021年 | 1037篇 |
2020年 | 1085篇 |
2019年 | 1012篇 |
2018年 | 937篇 |
2017年 | 1059篇 |
2016年 | 1008篇 |
2015年 | 1005篇 |
2014年 | 1626篇 |
2013年 | 1822篇 |
2012年 | 1980篇 |
2011年 | 2390篇 |
2010年 | 1726篇 |
2009年 | 2025篇 |
2008年 | 1737篇 |
2007年 | 2155篇 |
2006年 | 1976篇 |
2005年 | 1684篇 |
2004年 | 1459篇 |
2003年 | 1279篇 |
2002年 | 1070篇 |
2001年 | 969篇 |
2000年 | 838篇 |
1999年 | 584篇 |
1998年 | 515篇 |
1997年 | 431篇 |
1996年 | 425篇 |
1995年 | 304篇 |
1994年 | 268篇 |
1993年 | 247篇 |
1992年 | 226篇 |
1991年 | 204篇 |
1990年 | 167篇 |
1989年 | 103篇 |
1988年 | 83篇 |
1987年 | 68篇 |
1986年 | 62篇 |
1985年 | 54篇 |
1984年 | 56篇 |
1983年 | 27篇 |
1982年 | 43篇 |
1981年 | 42篇 |
1980年 | 37篇 |
1979年 | 22篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1976年 | 18篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 145 毫秒
91.
Feiyue Yang Yiwen Yao Zichun Yang Shuang Zhao Guobing Chen Kunfeng Li 《Ceramics International》2021,47(13):18351-18357
To meet demand for lightweight and high-strength ceramic foams, in-situ self-reinforced Si3N4 ceramic foams, with compressive strength of 13.2–45.9 MPa, were fabricated by protein foaming method combined with sintered reaction-bonded method. For comparison, ordinary protein foamed ceramics with irregular block microstructure were fabricated via reaction-bonded method, which had compressive strength of 3.6–20.5 MPa. Physical properties of these two types of samples were systematically compared. When open porosity was about 80%, both types of Si3N4 ceramic foams had excellent thermal insulation properties (<0.15 W m?1 K?1), while compressive strength of in-situ self-reinforced samples increased by more than 158% compared with ordinary samples. Under high-temperature oxidation conditions, microstructures of both types of samples were deformed with increase in oxidation temperature. Moreover, after oxidation temperature was increased to 1400 °C, oxidation weight gain decreased from 18.07% for ordinary samples to only 2.18% for self-reinforced samples. Thus, high-temperature oxidation resistance of Si3N4 ceramic foams was greatly improved. 相似文献
92.
《Ceramics International》2021,47(22):31485-31496
Mesoporous SmMnO3/CuMnOx catalyst was prepared by a two-step method using flaky CuMnOx with high specific surface and excellent catalytic ability as the carrier, which was further applied to photothermal synergistic degradation of gaseous toluene. Quantitative analysis of O2-TPD and H2-TPR showed that SmMnO3/CuMnOx exhibited abundant of the surface oxygen species and oxygen vacancies content, which enabled it to convert free oxygen to lattice oxygen more quickly during the reaction, and thus improving the reaction process. I-t and photoluminescence experiments demonstrated the improvement of photogenerated electron and hole separation ability of SmMnO3/CuMnOx catalyst. UV–Vis analysis manifested the full spectral range of absorption. XPS analysis verified the unequal positions of valence band of the two materials, which can facilitate the separation of photogenerated electrons from holes and improve the ability of better electron transfer. SmMnO3/CuMnOx catalyst has higher adsorbed oxygen content and light absorption capacity, which is beneficial to the catalytic oxidation. In situ DRIFTs proved that the oxidation reaction on the catalyst followed the Mars-van Krevelen redox cycle. The VOCs test found that SmMnO3/CuMnOx composite catalyst is with lower onset reaction temperature (T90 = 190 °C, T90, corresponding to 90% conversion) and good mineralization (100% at 275 °C). 相似文献
93.
94.
Vinícius D. Silva Rafael A. Raimundo Thiago A. Simões Francisco J.A. Loureiro Duncan P. Fagg Marco A. Morales Daniel A. Macedo Eliton S. Medeiros 《International Journal of Hydrogen Energy》2021,46(5):3798-3810
The development of technologically efficient anodes for water oxidation is crucial to improve hydrogen production via water splitting. Electrodes based on metallic active sites dispersed in carbon matrices have been shown to be an attractive way to attain this goal. However, challenges remain to prevent catalyst agglomeration that otherwise can result in a decrease of performance over time.In this work, we report an alternative and efficient method to produce nickel-nickel oxide nanoparticles-embedded in carbon nanofibers (Ni–NiO/C), by the solution blow spinning (SBS) process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses show the carbon nanofibrillar matrix as a robust support, with well-dispersed nickel nanoparticles on the surface. The responses of the linear scanning voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy demonstrate how a small fraction of nickel on the fiber surface (≈1.2–5.3%) is enough to promote substantial improvement in performance (η = 278 and 309 mV vs RHE for 10 mA cm?2) and a significant turnover frequency (TOF) values of 1.38 (η = 278) and 1.30 s?1 (η = 309). These promising results are correlated with a large amount of Ni3+ present on the fiber surfaces, as identified by X-ray Photoelectron Spectroscopy (XPS). This work provides a low-cost and rapid preparation technique that can be extended for the manufacture of a wide variety of electrodes based on metals supported on carbon nanofibers. 相似文献
95.
96.
Caizhi Zhang Hao Liu Tao Zeng Jiawei Chen Pengfeng Lin Bo Deng Fujian Liu Yifeng Zheng 《International Journal of Hydrogen Energy》2021,46(45):23489-23497
During the operation of proton exchange membrane fuel cell (PEMFC), it always suffers from reversible performance loss caused by the oxidation of platinum catalyst on its electrode, which reduces the electrochemical active surface area. Short circuit method has been found to improve the performance of fuel cells by stripping of oxides and other adsorbed species from platinum, which needs systematical understanding the effective parameters of short circuit method on fuel cell performance. In this paper, the effects of different short circuit activation parameters (duration, interval, cycles, cut-off voltage, operating current) are carefully studied and analyzed during short circuit operations. In addition, the mechanism revealing how relevant parameters influence short circuit activations is deeply analyzed. The results show that five groups of activation parameters have obvious influence on the activation of fuel cell, indicating that the short-circuit activation effect can be optimized. Among these parameters, the short-circuit duration parameter have the greatest impact on activation, because the platinum hydroxides and oxides is gradually removed during short-circuit duration and results in a larger effective surface area of the platinum catalyst for the electrochemical reaction. However, the smallest impact is short-circuit interval. Another finding is that the five activation parameters are not independent, so the optimal activation parameter value needs to be analyzed in combination with the operating conditions. Finally, according to the activation principle, selection of appropriate short circuit activation parameters for application are proposed to further improve performance and fuel utilization by considering the safety of the stack. 相似文献
97.
Waheed Iqbal Mariam Batool Arslan Hameed Saghir Abbas Muhammad Arif Nadeem 《International Journal of Hydrogen Energy》2021,46(49):25050-25059
Transition metal oxyhydroxides have been used as promising electrocatalysts for water splitting however, their catalytic activity is restricted due to low surface area and poor conductivity. Herein, we report novel composite FeOOH@ZIF-12/graphene composite as electrocatalyst for water oxidation, whereby ZIF-12 provide extra surface for the FeOOH dispersion whilst graphene act as excellent electron mediator. The composite shows a low overpotential value of 291 mV to attain a current density of 10 mA cm?2 and a low Tafel slope value of 78 mV dec?1. The catalyst offers a maximum current density of 101 mA cm?2, while it gives a turnover frequency (TOF) value of 0.031 s?1 at an overpotential of 291 mV only. The excellent activity and remarkable stability of composite is attributed to highly conductive and porous support. 相似文献
98.
《International Journal of Hydrogen Energy》2021,46(55):28078-28086
Interfacial hydrophobic/hydrophilic reaction fields significantly affect various reactions at the electrode surface. The hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) have been investigated on single crystal Pt electrodes modified with hydrophobic/hydrophilic cations and anion-exchange copolymers in alkaline solutions. In alkali metal hydroxide solutions, Pt (110) exhibits the highest HER/HOR activity in the low-index planes of Pt. On the low-index planes of Pt, the hydrophilicity of the alkali metal cation in the supporting electrolyte activates the HER/HOR depending on its hydration energy. Hydrophilic cations at the interface facilitate the extraction of hydrogen from the hydrated water. The modification of anion-exchange copolymers with a hydrophobic skeleton on Pt (110) further enhanced the HER/HOR activity. The hydrogen bonding network formed around the hydrophobic species facilitated the mobility of water molecules and the OH− as the reactant/product of the HER/HOR. Appropriately forming hydrophilic and hydrophobic reaction fields at the interface improved the HER/HOR activity. 相似文献
99.
Hanna Harrysson Birgitta Swolin Michael Axelsson Ingrid Undeland 《International Journal of Food Science & Technology》2020,55(6):2462-2471
Whole body saline-perfused rainbow trout (Oncorhynchus mykiss) was ice-stored for 4 weeks and compared with unwashed/washed minces from unbled and bled trout in terms of rancid odour, peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and redness loss. Muscle from saline-perfused fish, which had 72% less total haem, was deficient in rancid odour during the whole storage, while bled (54% less haem) and unbled samples developed rancid odour already after ~4 and 2 days; higher intensity without bleeding. PV/TBARS also developed in the order unbled > bled > perfused samples; however, PV/TBARS were not as completely prevented as rancid odour after perfusion. Saline washing (3 × 3 volumes) of unbled mince removed 84% haem and yielded the second most stable sample while saline washing (1 × 1 volumes) destabilised unbled mince, despite 64% haem removal. Concurrent antioxidant removal during washing of minces obviously counteracted the effect of blood removal and washing fish mince with small volumes of solution should be used with great care. 相似文献
100.