全文获取类型
收费全文 | 6751篇 |
免费 | 342篇 |
国内免费 | 535篇 |
专业分类
电工技术 | 74篇 |
综合类 | 176篇 |
化学工业 | 2045篇 |
金属工艺 | 295篇 |
机械仪表 | 104篇 |
建筑科学 | 86篇 |
矿业工程 | 25篇 |
能源动力 | 325篇 |
轻工业 | 904篇 |
水利工程 | 5篇 |
石油天然气 | 131篇 |
武器工业 | 11篇 |
无线电 | 485篇 |
一般工业技术 | 1089篇 |
冶金工业 | 72篇 |
原子能技术 | 1755篇 |
自动化技术 | 46篇 |
出版年
2024年 | 13篇 |
2023年 | 82篇 |
2022年 | 128篇 |
2021年 | 204篇 |
2020年 | 145篇 |
2019年 | 148篇 |
2018年 | 172篇 |
2017年 | 216篇 |
2016年 | 252篇 |
2015年 | 184篇 |
2014年 | 275篇 |
2013年 | 578篇 |
2012年 | 339篇 |
2011年 | 671篇 |
2010年 | 386篇 |
2009年 | 424篇 |
2008年 | 320篇 |
2007年 | 397篇 |
2006年 | 383篇 |
2005年 | 296篇 |
2004年 | 271篇 |
2003年 | 261篇 |
2002年 | 177篇 |
2001年 | 160篇 |
2000年 | 150篇 |
1999年 | 115篇 |
1998年 | 112篇 |
1997年 | 97篇 |
1996年 | 67篇 |
1995年 | 101篇 |
1994年 | 74篇 |
1993年 | 71篇 |
1992年 | 76篇 |
1991年 | 54篇 |
1990年 | 53篇 |
1989年 | 32篇 |
1988年 | 36篇 |
1987年 | 20篇 |
1986年 | 22篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1959年 | 7篇 |
排序方式: 共有7628条查询结果,搜索用时 15 毫秒
1.
The aim of this article is to synthesis tungsten oxide (WO3) nanoparticle along with Manganese (3 wt% and 10 wt%) by Microwave irradiation method. The physical properties of the synthesized Manganese doped Tungsten oxide materials were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscope (TEM), UV-Diffuse Reflectance Spectroscopy, SEM-EDAX and Photoluminescence studies. The predominant peaks obtained in X-ray diffraction pattern reveal the crystalline nature of the nanoparticles and the structure belongs to Monoclinic for pure and Mn doped WO3. FTIR analysis shows the presence of Tungsten and oxygen in the synthesis material and verified with EDAX. TEM analysis shows both pristine and Mn doped WO3 nanopaticles. They are having spherical shaped morphology with average particle size from 35 to 40 nm. UV-DRS revealed that the bandgap energy for pure and Manganese doped WO3 are discussed in this article. The Scanning Electron Microscope analysis shows the plate like morphology for pure WO3 and the morphology were decreased by doping Manganese. The defects and oxygen deficiencies were analysed by photoluminescence spectroscopy. 相似文献
2.
Cyclic tension and bend tests were performed on heat-resistant 12Cr1MoV steel specimens in as-supplied condition as well as after Zr+ ion beam surface irradiation. Distinct differences in strain induced relief, as well in cracking pattern of modified surface layer were observed by optical microscopy and interference profilometry. Changes in subsurface layer are characterized by means of nano- and microindentation and fractography of fracture surfaces (with the help of scanning electron microscopy). It is shown that the main influence on mechanical properties is mostly induced by thermal treatment during irradiation rather than formation of a 2 μm thick layer doped with Zr. The differences in deformation behavior may be explained by physical mesomechanics concepts. 相似文献
3.
The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m?2 and 45 W m?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m?1 to 30.2 MPa and 158 J m?1, respectively. Copyright © 2003 Society of Chemical Industry 相似文献
4.
小剂量辐射对肿瘤细胞K_(562)及肿瘤病人天然杀伤细胞(NK)活性的影响 总被引:2,自引:0,他引:2
已知小剂量辐射可增强机体免疫功能。从对高本底地区的调查发现,该地区居民肿瘤死亡率及某些肿瘤发病率有所降低(1)。NK细胞能直接杀伤肿瘤细胞,在肿瘤免疫中起着重要的作用。本文观察小剂量辐射对肿瘤病人和正常人外周血淋巴细胞NK活性的相对效应以及对人红白血病细胞(K(562)细胞)的影响,以期从体外买验来探索较小剂量辐射对肿瘤治疗的影响 相似文献
5.
医用聚氯乙烯材料的表面光接枝改性 总被引:6,自引:0,他引:6
研究了在不排氧氛围下 ,紫外光照射 ,以二苯甲酮 (BP)为光引发剂 ,甲基丙烯酸缩水甘油酯(GMA)在医用聚氯乙烯 (PVC)薄膜表面的气相接枝聚合。探讨了反应条件对接枝结果的影响 ,并用正交法指出了影响因素的显著性。用傅立叶红外 (FT- IR)、水接触角作为接枝改性结果的表征。FT- IR谱图表明 GMA已接枝到 PVC膜表面。水接触角由接枝前的 78°下降到 5 4° 相似文献
6.
Keita Ikeue Shingo Ando Tomohiro Mitsuyama Yusuke Ohta Keishi Arayama Akiko Tsutsumi Masato Machida 《Topics in Catalysis》2008,47(3-4):175-180
Lanthanide-based oxysulfides and sulfide, LnTaO3.5S0.5, Ln10OS14 (Ln = La, Pr, Nd, Sm) and La4In5S13, were successively synthesized by sulfurization in a flowing H2S. The sulfurization decreased the band-gap energies from >4 eV to <3eV, because of the formation of occupied S3p orbitals
on the top of valence band. In accordance with the small band gap, the H2 evolution from a 0.01 M Na2S and 0.01 M Na2SO3 solution system was observed under irradiation of light up to >500 nm. The rate of H2 evolution under light irradiation of >500 nm increased in the order of Ni/LaTaO3.5S0.5 < Ru/La10OS14 < Pt/La4In5S13. 相似文献
7.
5(4H)-Oxazolones react with ammonium acetate under microwave irradiation and using graphite as support in an eco-friendly process.
The reaction was carried out under solvent-free conditions and the imidazolones were obtained quantitatively. Moreover the
reaction time was reduced too. 相似文献
8.
9.
10.