全文获取类型
收费全文 | 614195篇 |
免费 | 6895篇 |
国内免费 | 1560篇 |
专业分类
电工技术 | 11052篇 |
综合类 | 462篇 |
化学工业 | 91753篇 |
金属工艺 | 31087篇 |
机械仪表 | 21799篇 |
建筑科学 | 12422篇 |
矿业工程 | 5245篇 |
能源动力 | 14711篇 |
轻工业 | 36554篇 |
水利工程 | 7830篇 |
石油天然气 | 17268篇 |
武器工业 | 36篇 |
无线电 | 65832篇 |
一般工业技术 | 135984篇 |
冶金工业 | 100499篇 |
原子能技术 | 16739篇 |
自动化技术 | 53377篇 |
出版年
2021年 | 5526篇 |
2020年 | 4272篇 |
2019年 | 5425篇 |
2018年 | 13981篇 |
2017年 | 14251篇 |
2016年 | 13310篇 |
2015年 | 6505篇 |
2014年 | 10637篇 |
2013年 | 26919篇 |
2012年 | 17557篇 |
2011年 | 25402篇 |
2010年 | 21151篇 |
2009年 | 22336篇 |
2008年 | 23103篇 |
2007年 | 23769篇 |
2006年 | 16745篇 |
2005年 | 16457篇 |
2004年 | 15300篇 |
2003年 | 15069篇 |
2002年 | 13817篇 |
2001年 | 13254篇 |
2000年 | 12709篇 |
1999年 | 12593篇 |
1998年 | 29751篇 |
1997年 | 21098篇 |
1996年 | 16121篇 |
1995年 | 12233篇 |
1994年 | 10923篇 |
1993年 | 11050篇 |
1992年 | 8380篇 |
1991年 | 8061篇 |
1990年 | 8128篇 |
1989年 | 7685篇 |
1988年 | 7372篇 |
1987年 | 6729篇 |
1986年 | 6520篇 |
1985年 | 7222篇 |
1984年 | 6781篇 |
1983年 | 6241篇 |
1982年 | 5788篇 |
1981年 | 5905篇 |
1980年 | 5645篇 |
1979年 | 5769篇 |
1978年 | 5878篇 |
1977年 | 6354篇 |
1976年 | 7791篇 |
1975年 | 5205篇 |
1974年 | 5116篇 |
1973年 | 5216篇 |
1972年 | 4546篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
181.
182.
183.
184.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention. 相似文献
185.
V. A. Eremenko V. N. Karpov V. V. Timonin N. G. Barnov I. O. Shakhtorin 《Journal of Mining Science》2015,51(6):1113-1125
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed. 相似文献
186.
187.
188.
Hoang V. Le Phuong T. Pham Ly T. Le Anh D. Nguyen Ngoc Quang Tran Phong D. Tran 《International Journal of Hydrogen Energy》2021,46(44):22852-22863
WO3 is a potential material candidate for construction of photoanode for solar driven water splitting. In this work, μm-thick porous WO3 photoanode is prepared by depositing a stable ink made of WO3 nanoparticles and Aristoflex velvet polymer in water using the doctor blade technique, followed by a sintering in air. The nature of WO3 nanoparticles, its loading mass on F-doped tin oxide electrode as well as sintering temperature are examined in order to optimize the photocatalytic activity of the resultant WO3 photoanode. The operation of WO3 photoanode is investigated by varying the light illumination direction and light incident intensity as well as changing the nature of the electrolyte. Dissolved tungsten in electrolyte is quantified by ICP-MS providing insights into the influences of electrolyte nature and operating conditions to the corrosion of WO3. It is proposed that the H2O2 and OH. radical generated as by-products of the photo-driven water oxidation on the photoanode surface are harmful species that accelerate the dissolution of WO3. 相似文献
189.
Sleptsov V. V. Kukushkin D. Yu. Kulikov S. N. Diteleva A. O. 《Russian Engineering Research》2021,41(5):416-418
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor... 相似文献
190.
D. Kherifi H. Belhouchet S. Ramesh K.Y. Sara Lee A. Kenzour S. Djoualah M.K.G. Abbas Y.H. Wong S. Ramesh 《Ceramics International》2021,47(12):16483-16490
In this work, the sintering behaviour of fluorapatite (FAp)–silicate composites prepared by mixing variable amounts of natural quartz (2.5 wt% to 20 wt%) and FAp was studied. The composites were pressureless sintered in air at temperatures from 1000 °C to 1350 °C. The effects of temperatures on the densification, phase formation, chemical bonding and Vickers hardness of the composites were evaluated. All the samples exhibited mixed phase, comprising FAp and francolite as the major constituents along with some minor phases of cristobalite, wollastonite, dicalcium silicate and/or whitlockite dependent on the quartz content and sintering temperature. The composite containing 2.5 wt% quartz exhibited the best sintering properties. The highest bulk density of 3 g/cm3 and a Vickers hardness of >4.2 GPa were obtained for the 2.5 wt% quartz–FAp composite when sintered at 1100 °C. The addition of quartz was found to alter the microstructure of the composites, where it exhibited a rod-like morphology when sintered at 1000 °C and a regular rounded grain structure when sintered at 1350 °C. A wetted grain surface was observed for composites containing high quartz content and was believed to be associated with a transient liquid phase sintering. 相似文献