全文获取类型
收费全文 | 116973篇 |
免费 | 9634篇 |
国内免费 | 5161篇 |
专业分类
电工技术 | 6776篇 |
技术理论 | 9篇 |
综合类 | 8004篇 |
化学工业 | 19606篇 |
金属工艺 | 7056篇 |
机械仪表 | 7616篇 |
建筑科学 | 9081篇 |
矿业工程 | 3915篇 |
能源动力 | 3575篇 |
轻工业 | 7096篇 |
水利工程 | 2076篇 |
石油天然气 | 8185篇 |
武器工业 | 978篇 |
无线电 | 12448篇 |
一般工业技术 | 13755篇 |
冶金工业 | 5770篇 |
原子能技术 | 1293篇 |
自动化技术 | 14529篇 |
出版年
2024年 | 396篇 |
2023年 | 1878篇 |
2022年 | 3143篇 |
2021年 | 4653篇 |
2020年 | 3616篇 |
2019年 | 3057篇 |
2018年 | 3432篇 |
2017年 | 3815篇 |
2016年 | 3373篇 |
2015年 | 4512篇 |
2014年 | 5844篇 |
2013年 | 6615篇 |
2012年 | 7162篇 |
2011年 | 7945篇 |
2010年 | 7108篇 |
2009年 | 6464篇 |
2008年 | 6424篇 |
2007年 | 6125篇 |
2006年 | 6211篇 |
2005年 | 5298篇 |
2004年 | 3837篇 |
2003年 | 3733篇 |
2002年 | 4059篇 |
2001年 | 3449篇 |
2000年 | 2879篇 |
1999年 | 3200篇 |
1998年 | 2510篇 |
1997年 | 2167篇 |
1996年 | 2069篇 |
1995年 | 1651篇 |
1994年 | 1281篇 |
1993年 | 930篇 |
1992年 | 766篇 |
1991年 | 527篇 |
1990年 | 410篇 |
1989年 | 328篇 |
1988年 | 269篇 |
1987年 | 163篇 |
1986年 | 131篇 |
1985年 | 78篇 |
1984年 | 60篇 |
1983年 | 51篇 |
1982年 | 51篇 |
1981年 | 30篇 |
1980年 | 36篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1951年 | 3篇 |
1940年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
101.
Spherical LiNi1/3Co1/3Mn1/3O2 cathode particles were resynthesized by a carbonate co-precipitation method using spent lithium-ion batteries (LIBs) as a raw material. The physical characteristics of the Ni1/3Co1/3Mn1/3CO3 precursor, the (Ni1/3Co1/3Mn1/3)3O4 intermediate, and the regenerated LiNi1/3Co1/3Mn1/3O2 cathode material were investigated by laser particle-size analysis, scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), thermogravimetry–differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the regenerated LiNi1/3Co1/3Mn1/3O2 was studied by continuous charge–discharge cycling and cyclic voltammetry. The results indicate that the regenerated Ni1/3Co1/3Mn1/3CO3 precursor comprises uniform spherical particles with a narrow particle-size distribution. The regenerated LiNi1/3Co1/3Mn1/3O2 comprises spherical particles similar to those of the Ni1/3Co1/3Mn1/3CO3 precursor, but with a narrower particle-size distribution. Moreover, it has a well-ordered layered structure and a low degree of cation mixing. The regenerated LiNi1/3Co1/3Mn1/3O2 shows an initial discharge capacity of 163.5 mA h g?1 at 0.1 C, between 2.7 and 4.3 V; the discharge capacity at 1 C is 135.1 mA h g?1, and the capacity retention ratio is 94.1% after 50 cycles. Even at the high rate of 5 C, LiNi1/3Co1/3Mn1/3O2 delivers the high capacity of 112.6 mA h g?1. These results demonstrate that the electrochemical performance of the regenerated LiNi1/3Co1/3Mn1/3O2 is comparable to that of a cathode synthesized from fresh materials by carbonate co-precipitation. 相似文献
103.
104.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
105.
Natural Computing - The fiber stretching process plays the key role in the process of fiber production and its effects is measured by the stretching ratio. The stretching ratio is determined by the... 相似文献
106.
108.
Ziqian Wang Yalan Chen Yating He Weidong Jiang Yan Long Guangyin Fan 《International Journal of Hydrogen Energy》2021,46(21):11587-11596
Developing high-efficiency and low-cost catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) is significant and critical for the exploitation and utilization of hydrogen energy. Herein, the in-situ fabrication of well-dispersed and small bimetallic RuNi alloy nanoparticles (NPs) with tuned compositions and concomitant hydrolysis of AB are successfully achieved by using graphitic carbon nitride (g-C3N4) as a NP support without additional stabilizing ligands. The optimized Ru1Ni7.5/g-C3N4 catalyst exhibits an excellent catalytic activity with a high turnover frequency of 901 min?1 and an activation energy of 28.46 kJ mol?1 without any base additives, overtaking the activities of many previously reported catalysts for AB hydrolysis. The kinetic studies indicate that the AB hydrolysis over Ru1Ni7.5/g-C3N4 is first-order and zero-order reactions with respect to the catalyst and AB concentrations, respectively. Ru1Ni7.5/g-C3N4 has a good recyclability with 46% of the initial catalytic activity retained even after five runs. The high performance of Ru1Ni7.5/g-C3N4 should be assigned to the small-sized alloy NPs with abundant accessible active sites and the synergistic effect between the composition-tuned Ru–Ni bimetals. This work highlights a potentially powerful and simple strategy for preparing highly active bimetallic alloy catalysts for AB hydrolysis to generate hydrogen. 相似文献
109.
Climate change raises many concerns for urban water management because of the effects on all aspects of the hydrological cycle. Urban water infrastructure has traditionally been designed using historical observations and assuming stationary climatic conditions. The capability of this infrastructure, whether for storm-water drainage, or water supply, may be over- or under-designed for future climatic conditions. In particular, changes in the frequency and intensity of extreme rainfall events will have the most acute effect on storm-water drainage systems. Therefore, it is necessary to take future climatic conditions into consideration in engineering designs in order to enhance water infrastructure investment planning practices in a long time horizon. This paper provides the initial results of a study that is examining ways to enhance urban infrastructure investment planning practices against changes in hydrologic regimes for a changing climate. Design storms and intensity-duration-frequency curves that are used in the engineering design of storm-water drainage systems are developed under future climatic conditions by empirically adjusting the general circulation model output, and using the Gumbel distribution and the Chicago method. Simulations are then performed on an existing storm-water drainage system from NE Calgary to investigate the resiliency of the system under climate change. 相似文献
110.
气烟囱效应——礁滩相岩性气藏的典型地震响应特征 总被引:14,自引:0,他引:14
品质良好的地震剖面上出现的地震模糊带称为气烟囱,发现和识别气烟囱是寻找大型气藏的有效方法。四川盆地东北部长兴组气藏是礁滩相岩性气藏,礁、滩作为一个独立的岩性体,与周围的地层、岩性结构差异较大,由此在构造应力场中形成力学尖点,从而产生气烟囱效应。已知的黄龙场、普光等气田,其气烟囱普遍存在。点礁通常形成下方的气烟囱,台缘礁通常在上方形成气烟囱;礁滩相在构造运动中控制了断层的发育过程,凸起的礁滩相上方可能发育对冲断层;斜坡较陡的台缘礁可能发育叠置的逆冲断层;礁、滩两侧边缘的断层一般都比较发育。断层发育加强了气烟囱效应。模拟试验验证了地震剖面解释结果。根据气烟囱地震相特征,预测黑池梁存在一个大型气藏。 相似文献