全文获取类型
收费全文 | 13957篇 |
免费 | 1690篇 |
国内免费 | 982篇 |
专业分类
电工技术 | 637篇 |
综合类 | 772篇 |
化学工业 | 2863篇 |
金属工艺 | 3173篇 |
机械仪表 | 598篇 |
建筑科学 | 72篇 |
矿业工程 | 145篇 |
能源动力 | 360篇 |
轻工业 | 1291篇 |
水利工程 | 7篇 |
石油天然气 | 153篇 |
武器工业 | 145篇 |
无线电 | 1375篇 |
一般工业技术 | 2307篇 |
冶金工业 | 1166篇 |
原子能技术 | 1363篇 |
自动化技术 | 202篇 |
出版年
2024年 | 60篇 |
2023年 | 329篇 |
2022年 | 607篇 |
2021年 | 666篇 |
2020年 | 625篇 |
2019年 | 606篇 |
2018年 | 595篇 |
2017年 | 624篇 |
2016年 | 546篇 |
2015年 | 514篇 |
2014年 | 696篇 |
2013年 | 930篇 |
2012年 | 829篇 |
2011年 | 947篇 |
2010年 | 657篇 |
2009年 | 742篇 |
2008年 | 689篇 |
2007年 | 948篇 |
2006年 | 806篇 |
2005年 | 670篇 |
2004年 | 653篇 |
2003年 | 505篇 |
2002年 | 368篇 |
2001年 | 325篇 |
2000年 | 284篇 |
1999年 | 245篇 |
1998年 | 188篇 |
1997年 | 185篇 |
1996年 | 162篇 |
1995年 | 104篇 |
1994年 | 93篇 |
1993年 | 96篇 |
1992年 | 75篇 |
1991年 | 57篇 |
1990年 | 37篇 |
1989年 | 37篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1959年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
《等离子体科学和技术》2020,22(6):65401
The double-coupled microwave resonance probe(DMRP) based on the hairpin probe is proposed for diagnosing atmospheric plasma jet(n_e10~(17) m~(-3)). In this work, the resonance characteristics of DMRP are investigated by numerical simulation. It shows that two resonance peaks on the reflectance spectrum can be observed, and influenced significantly by some parameters, such as the probe separation, the distance to the handheld radio frequency atmospheric pressure glow discharge plasma jet(RF-APGDPJ) and the plasma electron density less than 1017 m~(-3). Based on two resonance modes of DMRP, the electron densities in the afterglow of RF-APGDPJ at the different rf powers and helium flow rates are diagnosed experimentally by matching the change of FWHM(Df_1-Df_(1,air)and Df_2-Df_(2,air)) measured by vector network analyzer with the simulated relation between the FWHM changes and the plasma density. 相似文献
992.
《等离子体科学和技术》2020,22(8):85001
Based on the beam–plasma system model established in this paper, the trajectory of the electron beam in the ion channel is studied quantitatively through the envelope equation. Under different initial system parameters, the focusing transmission conditions of the beam in the ion channel are discussed. Then, a series of particle-in-cell simulations are performed, which generally versifies the theoretical results and shows some further details of the focusing behavior of the beam. It is found that the deceleration of some electrons around the focusing point or the beam–plasma interaction at the ion channel boundary will result in the generation of the residual electrons,which forms the electron return current that leads to the new instabilities influencing the focusing characteristics of the beam. 相似文献
993.
Xiu ZOU 《等离子体科学和技术》2020,22(12):125001
In this paper, an electronegative magnetized plasma sheath model with non-extensive electron distribution is established, and the Bohm criterion affected by the non-extensive parameter q is theoretically derived. The ion Mach number varies with q. The numerical simulation results show that compared with electronegative magnetized plasma sheath with Maxwell distribution (q = 1), the sheath structures with super-extensive distribution (q < 1) and sub-extensive distribution (q > 1) are different. The physical quantities including the sheath potential distribution, ion density distribution, the electron density distribution, negative ion density distribution and the net space charge density distribution are discussed. It is shown that the non-extensive parameter q has a significant influence on the structure of the electronegative magnetized plasma sheath. Due to the Lorentz force, both the magnitude and the angle of the magnetic field affect the structure of the sheath, whether the electrons are Maxwell distributed or non-extensively distributed. 相似文献
994.
通过扫描电镜观察到低温空气等离子体诱导酿酒酵母产生一种特殊的“空洞”形细胞。空洞细胞的形态特征及生长特性提示,空洞的形成可能是由于低温空气等离子体所致的细胞诱变效应,而不是等离子体对细胞表面的直接损伤。结果提示低温空气等离子体对细胞的损伤及诱变作用可能具有复杂的作用机制。 相似文献
995.
Laser plasma propulsion in glass-layer confined ablation was experimentally investigated. The results showed that compared to that of direct ablation, the coupling coefficient was enhanced over ten times. By observing the plasma expansion and calculating the ablation pressure, it was found that a higher ablation pressure and larger glass mass resulted in a higher coupling coefficient in the confined laser ablation. 相似文献
996.
Viscose-based activated carbon fibers(VACFs)were treated by a dielectric-barrier discharge plasma under the feed gas of N_2.The surface functional groups of VACFs were modified to improve the adsorption and catalysis capacity for SO_2.The surface properties of the untreated and plasma-treated VACFs were diagnosed by SEM,BET,FTIR,and XPS,and the adsorption capacities of VACFs for SO_2 were also compared and discussed.The results show that after the plasma treatment,the external surface of VACFs was etched and became rougher,while the surface area and the total pore volume decreased.FTIR and XPS revealed that nitrogen atoms were introduced onto the VACFs surface and the distribution of functional groups on the VACFs surface was changed remarkably.The adsorption characteristic of SO_2 indicates that the plasmatreated VACFs have better adsorption capacity than the original VACFs due to the nitrogen functional groups and new functional groups formed in modification,which is beneficial to the adsorption of SO_2. 相似文献
997.
Preparation of Copper Nanoparticles Using Dielectric Barrier Discharge at Atmospheric Pressure and its Mechanism简 总被引:1,自引:0,他引:1
Dielectric barrier discharge (DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide (CuO). Power X-ray diffraction (XRD) was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the diffusion of the active hydrogen species. Optical emission spectra (OES) were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen (H) radicals, and the heating effect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles. 相似文献
998.
Ar/CH3OH and Ar/N2/CH3OH plasma jets were generated at atmospheric pressure by dual-frequency excitations. Two different cases were studied with focus laid on the generation of CN radicals. In one case Ar gas passed through a bubbler with saturated methanol steam but without addition of N2 (Ar/CH3OH plasma). In the other case N2 passed through the bubbler with saturated methanol steam (Ar/N2/CH3OH plasma). The optical emission lines of CN radicals have been observed in these two cases of plasma discharges. The addition of N2 can significantly increase the optical emission intensity of CN bands. 相似文献
999.
1000.
Sintered silicon carbide (SiC) was etched by a dielectric barrier discharge source. A high voltage bipolar pulse was used with helium gas for the plasma generation. One stable filament plasma was generated and could be used for SiC etching. As the processing gas (NF3) mixing rate increased, the width and depth of the etching profile became narrower and deeper. The differentiated V–Q Lissajous method was used for measuring the capacitances (Ceq) of the electrode after the plasma turned on. The width of the etching profile was proportional to Ceq. As the current peak value Ismx of the substrate current increased, the volume removal rate of SiC increased. The etch depth was proportional to the ratio of Ismx to Ceq. Additionally, because of the different characteristics of the plasma disks on SiC substrate by the voltage polarity, the etching profile was unstable. However, in high NF3 mixing process, the etching profile became stable and deeper. 相似文献