全文获取类型
收费全文 | 3773篇 |
免费 | 324篇 |
国内免费 | 136篇 |
专业分类
电工技术 | 203篇 |
技术理论 | 1篇 |
综合类 | 213篇 |
化学工业 | 732篇 |
金属工艺 | 217篇 |
机械仪表 | 222篇 |
建筑科学 | 328篇 |
矿业工程 | 109篇 |
能源动力 | 210篇 |
轻工业 | 163篇 |
水利工程 | 56篇 |
石油天然气 | 209篇 |
武器工业 | 18篇 |
无线电 | 361篇 |
一般工业技术 | 538篇 |
冶金工业 | 205篇 |
原子能技术 | 25篇 |
自动化技术 | 423篇 |
出版年
2024年 | 8篇 |
2023年 | 66篇 |
2022年 | 85篇 |
2021年 | 146篇 |
2020年 | 117篇 |
2019年 | 104篇 |
2018年 | 129篇 |
2017年 | 142篇 |
2016年 | 121篇 |
2015年 | 128篇 |
2014年 | 160篇 |
2013年 | 219篇 |
2012年 | 250篇 |
2011年 | 224篇 |
2010年 | 200篇 |
2009年 | 208篇 |
2008年 | 185篇 |
2007年 | 177篇 |
2006年 | 207篇 |
2005年 | 180篇 |
2004年 | 111篇 |
2003年 | 122篇 |
2002年 | 95篇 |
2001年 | 65篇 |
2000年 | 107篇 |
1999年 | 120篇 |
1998年 | 106篇 |
1997年 | 68篇 |
1996年 | 76篇 |
1995年 | 86篇 |
1994年 | 60篇 |
1993年 | 29篇 |
1992年 | 38篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 6篇 |
1980年 | 1篇 |
排序方式: 共有4233条查询结果,搜索用时 15 毫秒
1.
Sijia Huo Yujin Wang Mianyi Yao Zhikun Zhang Lei Chen Hui Gu Jiahu Ouyang Yu Zhou 《Journal of the European Ceramic Society》2021,41(11):5466-5473
Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB2 addition as a sintering aid for the first time. The effects of ZrB2 contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB2 and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB2 (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports. 相似文献
2.
为了研究荷电细水雾对瓦斯爆炸超压的影响规律和机理,采用小尺寸管道模拟瓦斯爆炸,研究不同荷电电压作用下的瓦斯爆炸超压和平均压升速率,以及不同雾通量作用下的瓦斯爆炸超压.结果表明:随着荷电电压的升高,瓦斯爆炸超压和平均压升速率受到明显的抑制;随着雾通量的增加,瓦斯爆炸超压明显降低.在实验条件下,和普通细水雾相比,当雾通量为4L、荷电电压为8kV时,瓦斯爆炸超压峰值降低10.798kPa,降幅达49.78%;平均压升速率峰值降低180.468kPa/s,降幅达49.90%. 相似文献
3.
Wei Lai Lihong Ge Huaming Li Yilin Deng Bin Xu Bo Ouyang Erjun Kan 《International Journal of Hydrogen Energy》2021,46(53):26861-26872
The electrochemical water splitting to produce H2 in high efficiency with earth-abundant-metal catalysts remains a challenge. Here, we describe a simple “cyclic voltammetry + ageing” protocol at room temperature to activate Ni electrode (AC-Ni/NF) for hydrogen evolution reaction (HER), by which Ni/Ni(OH)2 heterostructure is formed at the surface. In situ Raman spectroscopy reveals the gradual growth of Ni/Ni(OH)2 heterostructure during the first 30 min of the aging treatment and combined with polarization measurements, it suggests a positive relation between the Ni/Ni(OH)2 amount and HER performance of the electrode. The obtained AC-Ni/NF catalyst, with plentiful Ni–Ni(OH)2 interfaces, exhibits remarkable performance towards HER, with the low overpotential of only 30 mV at a H2-evolving current density of 10 mA/cm2 and 153 mV at 100 mA/cm2, as well as a small Tafel slope of 46.8 mV/dec in 1 M KOH electrolyte at ambient temperature. The excellent HER performance of the AC-Ni/NF could be maintained for at least 24 h without obvious decay. Ex situ experiments and in situ electrochemical-Raman spectroscopy along with density functional theory (DFT) calculations reveal that Ni/Ni(OH)2 heterostructure, although partially reduced, can still persist during HER catalysis and it is the Ni–Ni(OH)2 interface reducing the energy barrier of H1 adsorption thus promoting the HER performance. 相似文献
4.
5.
混凝土的裂缝问题是一个普遍存在而又难于解决的工程实际问题,现对花坝二级电站引水隧洞工程中衬砌混凝土出现裂缝的原因进行分析,并针对出现的混凝土裂缝的具体情况,提出一些简单的预防和处理对策。 相似文献
6.
Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes. 相似文献
7.
钇铁石榴石薄膜材料的光吸收谱及Bi,Al掺入对谱的影响研究 总被引:2,自引:1,他引:1
采用单离子晶场跃迁模型,拟合出钇铁石榴石(YIG)薄膜材料的光吸收谱,与实验谱吻合得较好。从实验和理论上分析了(BIAI)YIG 薄膜材料的光吸收谱,结果表明,Al3+离子的作用如同稀释剂一样,减小了光吸收,Bi3+离子由于其强的自旋轨道耦合作用,增大了跃迁振子强度和跃迁线宽,从而增大了光吸收损耗,在此基础上所作的(BiAl)YIG的理论谱与实验谱符合得较好。 相似文献
8.
By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed. 相似文献
9.
10.
The current carrying capacity of single-walled semiconducting carbon nanotubes (CNTs) is studied by self-consistent quantum
simulations using the non-equilibrium Green’s function formalism with the self-consistent Born approximation. The simulation
shows that the current carrying capacity depends on the bias regime and is drastically different from that of metallic tubes.
For long CNTs (with a length much longer than zone boundary and optical phonon scattering mean free path), the current saturates
around 20 μA in the forward bias regime with unipolar transport due to phonon scattering. In ambipolar transport regime, the
current delivery limit is still about 20 μA due to recombination of electron and hole currents. In contrast, for short semiconducting
CNTs, the current delivery capacity can be above 25 μA in the unipolar transport regime and further double in the ambipolar
transport regime. In reverse bias regime, the current of a long CNT can exceed 20 μA due to the second subband conduction
and increased electron injection from the drain. The simulation provides a coherent explanation to the dependence of current
delivery limit on bias regime and channel length, which is consistent with recent experiments. 相似文献