全文获取类型
收费全文 | 39931篇 |
免费 | 3503篇 |
国内免费 | 1704篇 |
专业分类
电工技术 | 2223篇 |
技术理论 | 2篇 |
综合类 | 2546篇 |
化学工业 | 7025篇 |
金属工艺 | 2483篇 |
机械仪表 | 2383篇 |
建筑科学 | 3077篇 |
矿业工程 | 1237篇 |
能源动力 | 1051篇 |
轻工业 | 2207篇 |
水利工程 | 671篇 |
石油天然气 | 2924篇 |
武器工业 | 320篇 |
无线电 | 4714篇 |
一般工业技术 | 4788篇 |
冶金工业 | 1811篇 |
原子能技术 | 517篇 |
自动化技术 | 5159篇 |
出版年
2024年 | 210篇 |
2023年 | 735篇 |
2022年 | 1254篇 |
2021年 | 1743篇 |
2020年 | 1334篇 |
2019年 | 1073篇 |
2018年 | 1233篇 |
2017年 | 1356篇 |
2016年 | 1203篇 |
2015年 | 1592篇 |
2014年 | 2021篇 |
2013年 | 2401篇 |
2012年 | 2509篇 |
2011年 | 2787篇 |
2010年 | 2350篇 |
2009年 | 2132篇 |
2008年 | 2069篇 |
2007年 | 1897篇 |
2006年 | 2096篇 |
2005年 | 1863篇 |
2004年 | 1268篇 |
2003年 | 1088篇 |
2002年 | 967篇 |
2001年 | 852篇 |
2000年 | 980篇 |
1999年 | 1124篇 |
1998年 | 880篇 |
1997年 | 773篇 |
1996年 | 737篇 |
1995年 | 606篇 |
1994年 | 498篇 |
1993年 | 356篇 |
1992年 | 286篇 |
1991年 | 209篇 |
1990年 | 150篇 |
1989年 | 135篇 |
1988年 | 115篇 |
1987年 | 71篇 |
1986年 | 50篇 |
1985年 | 26篇 |
1984年 | 19篇 |
1983年 | 19篇 |
1982年 | 31篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 2篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Xueli Du Yuelong Wang Rongna Shi Zhiyong Mao Zhihao Yuan 《Journal of the European Ceramic Society》2018,38(10):3512-3517
The PbClxS1-x and Pb1-xBixS (x? =?0–0.05) bulks were fabricated with a facile method of hydrothermal synthesis and microwave sintering, and the effect of anionic and cationic donors on the thermoelectric performance of PbS was investigated. Although Cl? and Bi3+ both effectively improved the thermoelectric properties of n-type PbS, more excellent thermoelectric performance was obtained from Cl? doped samples because of higher electrical property and lower thermal conductivity at higher temperature (T? >?600?K). The thermoelectric figure of merit (ZT) reaches 1.04 for PbCl0.015S0.985 at 800?K and increases with temperature increasing without sign of saturation, which is probably the highest value ever reported for single-phase polycrystalline n-type PbS. The results also indicate that the hydrothermal synthesis and microwave sintering can realize anion doping as well as cation doping for n-type PbS at low cost, and PbS should be a robust alternative for PbTe thermoelectric materials. 相似文献
23.
24.
Machine Intelligence Research - This paper proposes an image encryption algorithm LQBPNN (logistic quantum and back propagation neural network) based on chaotic sequences incorporating quantum... 相似文献
25.
WeiJia Luo LingXia Li Shihui Yu Qianyu Guo Bowen Zhang Zheng Sun 《Ceramics International》2018,44(11):12414-12419
Low-loss (Zn1-xNix)ZrNbTaO8 (0.02?≤?x?≤?0.10) ceramics possessing single wolframite structure are initiatively synthesized by solid-state route. Based on the results of Rietveld refinement, complex chemical bond theory is used to establish the correlation between structural characteristics and microwave performance in this ceramic system. A small amount of Ni2+ (x?=?0.06) in A-site with the fixed substitution of Ta5+ in B-site can effectually raise the Q?×?f value of ZnZrNb2O8 ceramic, embodying a dense microstructure and high lattice energy. The dielectric constant and τf are mainly affected by bond ionicity and the average octahedral distortion. The (Zn0.94Ni0.06)ZrNbTaO8 ceramic sample sintered at 1150?°C for 3?h exhibits an outstanding combination of microwave dielectric properties: εr =?27.88, Q?×?f?=?128,951?GHz, τf =?–39.9?ppm/°C. Thus, it is considered to be a candidate material for the communication device applications at high frequency. 相似文献
27.
Ningning Fu Jiaxing Li Ming Wang Lili Ren Youqing Luo 《International journal of molecular sciences》2020,21(22)
An obligate mutualistic relationship exists between the fungus Amylostereum areolatum and woodwasp Sirex noctilio. The fungus digests lignin in the host pine, providing essential nutrients for the growing woodwasp larvae. However, the functional properties of this symbiosis are poorly described. In this study, we identified, cloned, and characterized 14 laccase genes from A. areolatum. These genes encoded proteins of 508 to 529 amino acids and contained three typical copper-oxidase domains, necessary to confer laccase activity. Besides, we performed molecular docking and dynamics simulation of the laccase proteins in complex with lignin compounds (monomers, dimers, trimers, and tetramers). AaLac2, AaLac3, AaLac6, AaLac8, and AaLac10 were found that had low binding energies with all lignin model compounds tested and three of them could maintain stability when binding to these compounds. Among these complexes, amino acid residues ALA, GLN, LEU, PHE, PRO, and SER were commonly present. Our study reveals the molecular basis of A. areolatum laccases interacting with lignin, which is essential for understanding how the fungus provides nutrients to S. noctilio. These findings might also provide guidance for the control of S. noctilio by informing the design of enzyme mutants that could reduce the efficiency of lignin degradation. 相似文献
28.
Petre Badica Dan Batalu Mihail Burdusel Mihai A. Grigoroscuta Gheorghe V. Aldica Monica Enculescu Raluca A. Gabor Zhiyong Wang Ruoxuan Huang Peifeng Li 《Ceramics International》2018,44(9):10181-10191
Pristine and (SiC+Te)-added MgB2 powders, green and spark plasma sintered (SPS) compacts were investigated from the viewpoint of quasi-static and dynamic (Split-Hopkinson Pressure Bar, SHPB) compressive mechanical properties The amount of the additive (SiC+Te) was selected to be the optimum one for maximization of the superconducting functional parameters. Pristine and added MgB2 show very similar compressive parameters (tan δ, fracture strength, Vickers hardness, others) and fragment size in the SHPB test. However, for the bulk SPSed samples the ratio of intergranular to transgranular fracturing changes, the first one being stronger in the added sample. This is reflected in the quasi-static KIC that is higher for the added sample. Despite this result, sintered samples are brittle and have roughly similar fragmentation behavior as for brittle engineering ceramics. In the fragmentation process, the composite nature of our samples should be considered with a special focus on MgB2 blocks (colonies) that show the major contribution to fracturing. The Glenn-Chudnovsky model of fracturing under dynamic load provides the closest values to our experimental fragment size data. 相似文献
29.
为了实现对微小环片零件的自动化装配,搭建了自动装配系统.通过4根直线导向轴与4个直线轴承来提高系统的导向精度和刚度.采用直线导轨进行各装配作业模块之间的切换,保证了微小环片零件的自动装配与取出.在环片的装配方向上,螺旋升降机和光栅尺实现环片的位置精度控制.在Lab VIEW编程环境中,采用分层软件架构和模块化控制思想,避免了不必要的数据循环检测与丢失,能够达到环片组件的装配精度要求.控制系统分为系统初始化模块、参数设置模块、装配模块和取出模块,自动装配系统通过各个模块间的相互交流配合完成装配任务.采用本文中自动装配系统装配环片的实验结果表明,环片零件装配的最大位置误差为26μm,垂直度误差为17μm,平均装配时间为75 s/片,可满足环片组件所需的精度要求. 相似文献
30.
Tian Xiaoying Peng Hui Luo Xuguang Nie Shiyuan Zhou Feng Peng Xiaoyan 《International Journal of Control, Automation and Systems》2020,18(4):897-910
International Journal of Control, Automation and Systems - There is a class of typical nonlinear industrial process, which can be characterized by a first-order inertia plus pure delay model in an... 相似文献