全文获取类型
收费全文 | 107437篇 |
免费 | 10390篇 |
国内免费 | 5201篇 |
专业分类
电工技术 | 6916篇 |
技术理论 | 12篇 |
综合类 | 7207篇 |
化学工业 | 17712篇 |
金属工艺 | 6111篇 |
机械仪表 | 6908篇 |
建筑科学 | 7999篇 |
矿业工程 | 3182篇 |
能源动力 | 3385篇 |
轻工业 | 7153篇 |
水利工程 | 2221篇 |
石油天然气 | 5515篇 |
武器工业 | 1194篇 |
无线电 | 12837篇 |
一般工业技术 | 12915篇 |
冶金工业 | 5331篇 |
原子能技术 | 1482篇 |
自动化技术 | 14948篇 |
出版年
2024年 | 416篇 |
2023年 | 1727篇 |
2022年 | 3214篇 |
2021年 | 4685篇 |
2020年 | 3444篇 |
2019年 | 2948篇 |
2018年 | 3321篇 |
2017年 | 3522篇 |
2016年 | 3257篇 |
2015年 | 4472篇 |
2014年 | 5480篇 |
2013年 | 6705篇 |
2012年 | 7376篇 |
2011年 | 7786篇 |
2010年 | 6827篇 |
2009年 | 6596篇 |
2008年 | 6280篇 |
2007年 | 5911篇 |
2006年 | 5785篇 |
2005年 | 4850篇 |
2004年 | 3631篇 |
2003年 | 3225篇 |
2002年 | 3361篇 |
2001年 | 2999篇 |
2000年 | 2496篇 |
1999年 | 2457篇 |
1998年 | 1925篇 |
1997年 | 1592篇 |
1996年 | 1379篇 |
1995年 | 1173篇 |
1994年 | 856篇 |
1993年 | 735篇 |
1992年 | 561篇 |
1991年 | 437篇 |
1990年 | 313篇 |
1989年 | 264篇 |
1988年 | 239篇 |
1987年 | 127篇 |
1986年 | 142篇 |
1985年 | 98篇 |
1984年 | 54篇 |
1983年 | 36篇 |
1982年 | 49篇 |
1981年 | 41篇 |
1980年 | 28篇 |
1979年 | 31篇 |
1977年 | 23篇 |
1976年 | 22篇 |
1975年 | 18篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
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
12.
Dong Liu Xia Ke Zhong-Ce Hu Yu-Guo Zheng 《Journal of Bioscience and Bioengineering》2021,131(5):518-524
13.
14.
Chaozhong Sun Xiaoying Guo Rui Ji Changzheng Hu Laijun Liu Liang Fang Zhenxiang Cheng Nengneng Luo 《Ceramics International》2021,47(4):5038-5043
The triboelectric effect has recently demonstrated its great potential in environmental remediation and even new energy applications for triggering a number of catalytic reactions by utilizing trivial mechanical energy. In this study, Ba4Nd2Fe2Nb8O30 (BNFN) submicron powders were used to degrade organic dyes via the tribocatalytic effect. Under the frictional excitation of three PTFE stirring rods in a 5 mg/L RhB dye solution, BNFN demonstrates a high tribocatalytic degradation efficiency of 97% in 2 h. Hydroxyl radicals (?OH) and superoxide radicals (?O2-) were also detected during the catalysis process, which proves that triboelectric energy stimulates BNFN to generate electron-hole pairs. The tribocatalysis of tungsten bronze BNFN submicron powders provides a novel and efficient method for the degradation of wastewater dye by utilizing trivial mechanical energy. 相似文献
15.
Journal of Signal Processing Systems - With the latest development of automation technology, object detection technology has received more and more research attention. Automated object detection... 相似文献
16.
A novel CdS/CaFe2O4 (CS/CFO) heterogeneous p-n junction was created by thermal deposition of CaFe2O4 nanoparticles on CdS rods. The CS/CFO hetero-structured photocatalysts exhibited increasingly efficient visible light harvesting compared to the bare CdS. The CS/CFO composites also presented higher photocurrent and slower decay of photoluminescence, suggesting a better separation of the photo-generated electrons and holes. The photocatalytic H2 evolution quantity on the optimized CS/CFO composite from water in the presence of ethanol was up to 2200 μmol after 3-h visible light illumination, which is more than twice that of the pristine CdS. The chemical interaction between CdS and CaFe2O4 was confirmed by the shifts in the XPS peaks, which made it possible for the charge carriers to transfer across the p-n junction interface. This research highlights the importance of forming an interfacial p-n heterojunction between two semiconductors for efficient charge separation and improved photocatalytic performance. 相似文献
17.
Jieyi Yu Xianguo Liu Rui Su Xuefeng Zhang Xinglong Dong 《Ceramics International》2021,47(17):23950-23957
Increasing the dielectric loss capacity plays an important role in enhancing the electromagnetic absorption performance of materials. It remains a challenge to simultaneously introduce multiple types of dielectric losses in the material. In this work, we show that the atomic and interfacial dipole polarizations can be simultaneously enhanced by substituting N species into both carbon coating layers and bulk TiC lattices of a core-shell TiC@C material. Additionally, substitution of N species results more exposed TiC(111) facets and refines the TiC grain sizes in the bulk material, which is beneficial for enhancing the scattering of the external electromagnetic waves. The maximum reflection loss of the N substituted TiC@C material is measured as ?47.1 dB with an effective absorbing bandwidth of 4.83 GHz at 1.9 mm, which illustrates a valuable way to further tuning the electromagnetic absorption performance of this type of materials. 相似文献
18.
Water Resources Management - The low impact development (LID) concept aims to control storm runoff and pollution through decentralized, small-scale source control to bring the development area as... 相似文献
19.
20.
Yuan-Xia Wang Ying Shi Chen-Chen Wang Jia-Hui Cheng Ying Wang Wen-Jun Shao Li-Zhi Liu 《应用聚合物科学杂志》2021,138(27):50651
Crosslinking of polyolefin elastomer (POE, ENGAGE™ 8480) with Dicumyl Peroxide (DCP) can have effects on its crystallization dynamics, crystal structure, and properties. The POE crosslinked uniformly has significantly lower crystalline ability than the one with only amorphous phase crosslinked, which, in turn, has weaker crystalline ability than neat POE. The crystallinity and melting point depend on how the POE is crosslinked. The neat POE and POE crosslinked in amorphous phase only, are investigated with DSC and in-situ tensile/synchrotron radiation (WAXD/SAXS). In situ tensile/synchrotron X-ray during a uniaxial stretching process indicates that severe crystal fragmentation is observed at a strain around 45%, and with further increase in strain. The stress in the crosslinked POE is significantly larger than neat POE. For both samples, crystal orientation increases sharply within the strain range up to 88% where orientation-induced new crystals aligned in stretching direction are observed. The long period increases more in stretching direction for the crosslinked POE, consistent with larger stress in this sample, and the stress difference is more pronounced at large strains (27.3 vs. 10.9 MPa at a strain 435%). Permanent set of the crosslinked POE is smaller, consistent with less oriented crystals observed after the test for permanent set. 相似文献