全文获取类型
收费全文 | 1217873篇 |
免费 | 117111篇 |
国内免费 | 75932篇 |
专业分类
电工技术 | 91226篇 |
技术理论 | 55篇 |
综合类 | 108665篇 |
化学工业 | 171400篇 |
金属工艺 | 77152篇 |
机械仪表 | 82453篇 |
建筑科学 | 92326篇 |
矿业工程 | 44364篇 |
能源动力 | 31670篇 |
轻工业 | 104241篇 |
水利工程 | 33692篇 |
石油天然气 | 55471篇 |
武器工业 | 14170篇 |
无线电 | 130124篇 |
一般工业技术 | 123601篇 |
冶金工业 | 59497篇 |
原子能技术 | 19250篇 |
自动化技术 | 171559篇 |
出版年
2024年 | 4964篇 |
2023年 | 16747篇 |
2022年 | 37931篇 |
2021年 | 51671篇 |
2020年 | 37457篇 |
2019年 | 27906篇 |
2018年 | 31532篇 |
2017年 | 35734篇 |
2016年 | 32514篇 |
2015年 | 48056篇 |
2014年 | 62212篇 |
2013年 | 74759篇 |
2012年 | 88654篇 |
2011年 | 95742篇 |
2010年 | 88597篇 |
2009年 | 84599篇 |
2008年 | 86082篇 |
2007年 | 83871篇 |
2006年 | 75501篇 |
2005年 | 63443篇 |
2004年 | 46067篇 |
2003年 | 34981篇 |
2002年 | 33169篇 |
2001年 | 30028篇 |
2000年 | 25895篇 |
1999年 | 19002篇 |
1998年 | 13993篇 |
1997年 | 11516篇 |
1996年 | 10331篇 |
1995年 | 8571篇 |
1994年 | 6913篇 |
1993年 | 5351篇 |
1992年 | 4395篇 |
1991年 | 3481篇 |
1990年 | 3052篇 |
1989年 | 2698篇 |
1988年 | 2257篇 |
1987年 | 1723篇 |
1986年 | 1530篇 |
1985年 | 1296篇 |
1984年 | 1137篇 |
1983年 | 1007篇 |
1982年 | 990篇 |
1981年 | 1000篇 |
1980年 | 1067篇 |
1979年 | 1004篇 |
1978年 | 884篇 |
1977年 | 906篇 |
1976年 | 1041篇 |
1973年 | 812篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Shuang Chen Chao Yu Zhanfang Cao Xiaoping Huang Shuai Wang Hong Zhong 《International Journal of Hydrogen Energy》2021,46(10):7037-7046
The development of efficient and stable oxygen evolution reaction (OER) catalysts is an ongoing challenge. In order to solve the problem of low oxygen evolution efficiency of the current OER catalysts, a novel material was synthesized by the incorporation of NiFeCr-LDH and MoS2, and its structural and electrochemical properties were also investigated. The introduction of MoS2 improves the electrochemical performance of NiFeCr-LDH. The polarization curve shows that the potential of composite material is only 1.50 V at a current density of 10 mA cm?2, which is far superior to commercial precious metal catalysts. In addition, the stability experiment shows that the composite material has excellent stability, and the current density has little change after 500 cycles. Furthermore, we found that some metal ions, such as Ni, Cr and Mo, exist in the form of high valence on the surface of NiFeCr-LDH@MoS2, which is also conducive to the occurrence of oxygen evolution reaction. 相似文献
72.
73.
Yunqi Li Jing Li Yang-Gang Wang Xiran Chen Mingtao Liu Zhong Zheng Xihong Peng 《International Journal of Hydrogen Energy》2021,46(24):13273-13282
In this work, density functional theory (DFT) calculations were used to investigate the mechanism of carbon corrosion on nitrogen-doped carbon support. Free energy diagrams were generated based on three proposed reaction pathways to evaluate corrosion mechanisms. The most energetically preferred mechanism on nitrogen-doped carbon was determined. The results show that the step of water dissociation to form #OH was the rate-determining step for gra-G-1N (graphene doped with graphitic N) and pyrr-G-1N (graphene doped with pyrrolic N). As for graphene doped with pyridinic N, the step of C#OC#O formation was critical. It was found that the control of nitrogen concentration was necessary for precisely designing optimized carbon materials. Abundance of nitrogen moieties aggravated the carbon corrosion. When the high potential was applied, specific types of graphitic N and pyridinic N were found to be favorable carbon modifications to improve carbon corrosion resistance. Moreover, the solvent effect was also investigated. The results provide theoretical insights and design guidelines to improve corrosion resistance in carbon support through material modification by inhibiting the adsorption of surface oxides (OH, O, and OOH). 相似文献
74.
介绍装配式建筑电气设计中的管线分离SI体系、模块化机电设计、集成机电部品、装配式建筑防雷接地系统等关键技术,并进行简要分析. 相似文献
75.
Junjie Li Mei Liang Wanjing Cheng Shuhao Wang 《International Journal of Hydrogen Energy》2021,46(14):9553-9566
Electric vehicles (EVs) are considered a promising alternative to conventional vehicles (CVs) to alleviate the oil crisis and reduce urban air pollution and carbon emissions. Consumers usually focus on the tangible cost when choosing an EV or CV but overlook the time cost for restricting purchase or driving and the environmental cost from gas emissions, falling to have a comprehensive understanding of the economic competitiveness of CVs and EVs. In this study, a life cycle cost model for vehicles is conducted to express traffic and environmental policies in monetary terms, which are called intangible cost and external cost, respectively. Battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs), and CVs are compared in four first-tier, four new first-tier, and 4 s-tier and below cities in China. The comparison shows that BEVs and FCEVs in most cities are incomparable with CVs in terms of tangible cost. However, the prominent traffic and environmental policies in first-tier cities, especially in Beijing and Shanghai, greatly increase the intangible and external costs of CVs, making consumers more inclined to purchase BEVs and FCEVs. The main policy benefits of BEVs and FCEVs come from three aspects: government subsidies, purchase and driving restrictions, and environmental taxes. With the predictable reduction in government subsidies, traffic and environmental policies present important factors influencing the competitiveness of BEVs and FCEVs. In first-tier cities, BEVs and FCEVs already have a competitive foundation for large-scale promotion. In new first-tier and second-tier and below cities, stricter traffic and environmental policies need to be formulated to offset the negative impact of the reduction in government subsidies on the competitiveness of BEVs and FCEVs. Additionally, a sensitivity analysis reveals that increasing the mileage and reducing fuel prices can significantly improve the competitiveness of BEVs and FCEVs, respectively. 相似文献
76.
Shilin Du Yichen Dong Feiqiang Guo Beile Tian Songbo Mao Lin Qian Chengyun Xin 《International Journal of Hydrogen Energy》2021,46(27):14138-14147
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications. 相似文献
77.
本文通过对各项治理技术比选,提出了生态封场技术在非正规垃圾堆放场治理中的应用,并结合实际案例给出了详细治理方案. 相似文献
78.
79.
An electrolyte Equation of State is presented by combining the Cubic Plus Association Equation of State,Mean Spherical Approximation and the Born equation.This new model uses experimental relative static permittivity,intend to predict well the activity coefficients of individual ions (ACI) and liquid densities of aqueous solutions.This new model is applied to model water + NaCl binary system and water + gas +NaCl ternary systems.The cation/anion-water interaction parameters of are obtained by fitting the exper-imental data of ACI,mean ionic activity coefficients (MIAC) and liquid densities of water + NaCl binary system.The cation/anion-gas interaction parameters are obtained by fitting the experimental data of gas solubilities in aqueous NaCl solutions.The modeling results show that this new model can correlate well with the phase equilibrium and volumetric properties.Without gas,predictions for ACI,MIAC,and liquid densities present relative average deviations of 1.3%,3.6% and 1.4% compared to experimental ref-erence values.For most gas-containing systems,predictions for gas solubilities present relative average deviations lower than 7.0%.Further,the contributions of ACI,and salting effects of NaCl on gases are ana-lyzed and discussed. 相似文献
80.
Elise Laszlo Gregory De Crescenzo Alfonso Nieto-Argüello Xavier Banquy Davide Brambilla 《Advanced functional materials》2021,31(46):2106061
The noninvasive sampling of dermal interstitial fluid (ISF) for the monitoring of clinical biomarkers is a greatly appealing area of research. The identification of molecular biomarkers in biological fluids has been accelerated with -omics analyses but remains limited in ISF because of its time-consuming and complex extraction process. Here, the generation of microneedle (MN) patches made of superabsorbent acrylate-based hydrogels for the rapid sampling of dermal ISF is described to explore its proteome. In depth, iterative optimization allows the identification of novel acrylate-based compositions with the required chemical, mechanical, and biocompatibility properties allowing proteomic analysis of the extracted ISF for the first time after sampling with swelling MNs. The generated MN arrays show no cytotoxic effect, successfully cross the stratum corneum, and can collect up to 6 µL of dermal ISF in 10 min in vivo. Proteomics lead to the detection of 176 clinically relevant biomarkers in the collected samples validating the use of ISF as a relevant bodily fluid for disease monitoring and diagnostic. Importantly, it is discovered that extraction fingerprint is strongly dependent on the MNs chemistry, and thus specific biomarkers could be selectively extracted by tuning the composition of the patch, making the system versatile and specific. 相似文献