全文获取类型
收费全文 | 302026篇 |
免费 | 5960篇 |
国内免费 | 866篇 |
专业分类
电工技术 | 5451篇 |
综合类 | 372篇 |
化学工业 | 45234篇 |
金属工艺 | 11116篇 |
机械仪表 | 9278篇 |
建筑科学 | 7547篇 |
矿业工程 | 1162篇 |
能源动力 | 7357篇 |
轻工业 | 28443篇 |
水利工程 | 2909篇 |
石油天然气 | 4087篇 |
武器工业 | 74篇 |
无线电 | 37173篇 |
一般工业技术 | 57406篇 |
冶金工业 | 56453篇 |
原子能技术 | 5657篇 |
自动化技术 | 29133篇 |
出版年
2021年 | 3022篇 |
2020年 | 2320篇 |
2019年 | 2765篇 |
2018年 | 5042篇 |
2017年 | 5070篇 |
2016年 | 5332篇 |
2015年 | 3423篇 |
2014年 | 5533篇 |
2013年 | 14181篇 |
2012年 | 9024篇 |
2011年 | 11340篇 |
2010年 | 8849篇 |
2009年 | 9543篇 |
2008年 | 10588篇 |
2007年 | 10268篇 |
2006年 | 9077篇 |
2005年 | 8230篇 |
2004年 | 7858篇 |
2003年 | 7622篇 |
2002年 | 7202篇 |
2001年 | 6989篇 |
2000年 | 6686篇 |
1999年 | 6856篇 |
1998年 | 17361篇 |
1997年 | 12163篇 |
1996年 | 9363篇 |
1995年 | 7171篇 |
1994年 | 6364篇 |
1993年 | 6221篇 |
1992年 | 4778篇 |
1991年 | 4447篇 |
1990年 | 4278篇 |
1989年 | 3997篇 |
1988年 | 3832篇 |
1987年 | 3363篇 |
1986年 | 3257篇 |
1985年 | 3829篇 |
1984年 | 3576篇 |
1983年 | 3178篇 |
1982年 | 3030篇 |
1981年 | 3137篇 |
1980年 | 2928篇 |
1979年 | 2778篇 |
1978年 | 2625篇 |
1977年 | 3150篇 |
1976年 | 4018篇 |
1975年 | 2426篇 |
1974年 | 2392篇 |
1973年 | 2405篇 |
1972年 | 1904篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
81.
Scientometrics - This study investigates a potential relationship between highly-cited scholarly papers and the number of citations received by other papers with which they share a journal issue.... 相似文献
82.
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of... 相似文献
83.
Giorgio Benedek Joseph R. Manson Salvador Miret-Artés 《Advanced materials (Deerfield Beach, Fla.)》2020,32(25):2002072
Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision. 相似文献
84.
Kolmachikhina E. B. Sviridov A.V. Naumov K. D. 《Russian Journal of Non-Ferrous Metals》2020,61(5):488-493
Russian Journal of Non-Ferrous Metals - This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate... 相似文献
85.
86.
87.
88.
89.
An alternative Equivalent Electrical Circuit for Proton Exchange Membrane Fuel Cells is modelled in this study. Both I–V characteristics and H2 consumptions corresponding to generated power under load and no-load conditions are investigated. For this purpose, H2 consumptions and I–V characteristics of three different sized PEMFCs are tested. There is a very good harmony between the model results and measured values (relative error %0.7, %6.4 and %2.5 for FC-A, FC-B and FC-C respectively). In the proposed model current passes only on parallel resistance and not on serial resistance at no-load condition. Thus, a FC with higher parallel resistance should be preferred. Another key output of this study is that based on the proposed model, performance comparison of FCs can be performed with the parameters defined in this work. Proposals made in this study can easily be used for performance analysis of FCs under for both steady state and transient analysis. 相似文献
90.
Marcela Stoia Cornelia Păcurariu Ciprian Mihali Iosif Mălăescu Cătălin Nicolae Marin Aylin Căpraru 《Ceramics International》2019,45(2):2725-2735
Magnetic MnFe2O4 nanopowders were synthesized by an original solvothermal method in the absence and in the presence of tetra-n-butylammonium bromide (TBAB) and Tween 80 (TW) as surfactants. Manganese ferrite/polyaniline (PANI) hybrid materials were synthesized by in situ polymerization of aniline on the surface of MnFe2O4 using ammonium persulfate as oxidant. The purpose of the study was to investigate the influence of the two surfactants on the properties of the MnFe2O4 powders and of their composites with PANI. The specific surface area, the cumulative surface area of pores and the cumulative volume of pores are influenced by the nature of surfactant in case of MnFe2O4 powders and are higher by comparison to those of the MnFe2O4/PANI hybrid materials. The values of saturation magnetization in case of MnFe2O4 powders are higher than those of the hybrid materials and are not influenced by the surfactant nature. These features revealed that MnFe2O4 powders can be efficiently used as adsorbents for the purification of wastewaters. The values of the electrical conductivity of the composites exhibit a significant increase in comparison to the MnFe2O4 powders and depend on the surfactant nature. The highest value of electrical conductivity was achieved by the composite obtained using Tween 80 as surfactant (σDC = 54.5·10?5S?m?1) which was close to that of PANI (σDC = 61.2·10?5 S?m?1). The fact that the magnetic and electric properties of the synthesized MnFe2O4/PANI composites can be changed by design, demonstrate the high potential of these materials to be used in magneto-electric applications. 相似文献