全文获取类型
收费全文 | 97382篇 |
免费 | 8872篇 |
国内免费 | 4775篇 |
专业分类
电工技术 | 5881篇 |
技术理论 | 4篇 |
综合类 | 6688篇 |
化学工业 | 15633篇 |
金属工艺 | 5755篇 |
机械仪表 | 6468篇 |
建筑科学 | 7968篇 |
矿业工程 | 2773篇 |
能源动力 | 2486篇 |
轻工业 | 6459篇 |
水利工程 | 1894篇 |
石油天然气 | 5632篇 |
武器工业 | 813篇 |
无线电 | 11984篇 |
一般工业技术 | 11317篇 |
冶金工业 | 4735篇 |
原子能技术 | 1102篇 |
自动化技术 | 13437篇 |
出版年
2024年 | 429篇 |
2023年 | 1725篇 |
2022年 | 3080篇 |
2021年 | 4265篇 |
2020年 | 3226篇 |
2019年 | 2565篇 |
2018年 | 2750篇 |
2017年 | 3299篇 |
2016年 | 2929篇 |
2015年 | 4133篇 |
2014年 | 5145篇 |
2013年 | 6271篇 |
2012年 | 6458篇 |
2011年 | 7279篇 |
2010年 | 6433篇 |
2009年 | 6141篇 |
2008年 | 6059篇 |
2007年 | 5567篇 |
2006年 | 5280篇 |
2005年 | 4395篇 |
2004年 | 2876篇 |
2003年 | 2377篇 |
2002年 | 2269篇 |
2001年 | 2012篇 |
2000年 | 1857篇 |
1999年 | 2045篇 |
1998年 | 1727篇 |
1997年 | 1480篇 |
1996年 | 1424篇 |
1995年 | 1176篇 |
1994年 | 981篇 |
1993年 | 721篇 |
1992年 | 573篇 |
1991年 | 464篇 |
1990年 | 338篇 |
1989年 | 283篇 |
1988年 | 231篇 |
1987年 | 160篇 |
1986年 | 130篇 |
1985年 | 91篇 |
1984年 | 80篇 |
1983年 | 57篇 |
1982年 | 58篇 |
1981年 | 40篇 |
1980年 | 39篇 |
1979年 | 23篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1974年 | 7篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Energy transfer from photo-excited electrons in a metal thin film to the dielectric substrate is important for understanding the ultrafast heat transfer process across the two materials. Substantial research has been conducted to investigate heat transfer in a metal-dielectric structure. In this work, a two-temperature model in metal was used to analyze the interface electron and dielectric substrate coupling. An improved temperature and wavelength-dependent Drude–Lorentz model was implemented to interpret the signals obtained in optical measurements. Ultrafast pump-and-probe measurements on Au-Si samples were carried out, where the probe photon energy was chosen to be close to the interband transition threshold of gold to minimize the influence of non-equilibrium electrons on the optical response and maximize the thermal modulation to the optical reflectance. Electron-substrate interface thermal conductance at different pump laser fluences was obtained, and was found to increase with the interface temperature. 相似文献
12.
Ying Chen HuiLi Zhang YuNing Liang YanHua Gao Yongchao Li 《Petroleum Science and Technology》2019,37(7):787-795
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst. 相似文献
13.
14.
15.
16.
17.
18.
19.
Hao Li Pengcheng Zhang Shengquan Yu Hongyu Yang Bin Tang Fuhai Li Shuren Zhang 《Ceramics International》2019,45(9):11639-11647
Mg2(Ti1-xSnx)O4 (x?=?0–1) ceramics were prepared through conventional solid-state method. This paper focused on the dependence of microwave dielectric properties on crystal structural characteristics via crystal structure refinement, Raman spectra study and complex chemical bond theory. XRD spectrums delineated the phase information of a spinel structure, and structural characteristic of these compositions were achieved with the help of Rietveld refinements. Raman spectrums were used to depict the correlations between vibrational phonon modes and dielectric properties. The variation of permittivity is ascribed to the Mg2(Ti1-xSnx)O4 average bond covalency. The relationship among the B-site octahedral bond energy, tetrahedral bond energy and temperature coefficient are discussed by defining on the change rate of bond energy and the contribution rate of octahedral bond energy. The quality factor is affected by systematic total lattice energy, and the research of XPS patterns illustrated that oxygen vacancies can be effectively restrained in rich oxygen sintering process. Obviously, the microwave dielectric properties of Mg2(Ti1-xSnx)O4 compounds were obtained (= 12.18, ?=?170,130?GHz, ?=??53.1?ppm/°C, x?=?0.2). 相似文献
20.
A new constitutive equation of thermoelasticity for crystals is presented based on the interatomic potential and solid mechanics at finite temperature. Using the new constitutive equation, the calculations for crystal copper and graphene are carried out under different loading paths at different temperatures. The calculated results are in good agreement with those of the previous thermoelasticity constitutive equation based on quantum mechanics, which clearly indicates that our new constitutive equation of thermoelasticity is correct. A lot of comparisons also show that the present theory is more concise and efficient than the previous thermal stress theory in the practical application. 相似文献