全文获取类型
收费全文 | 37775篇 |
免费 | 2368篇 |
国内免费 | 2697篇 |
专业分类
电工技术 | 1333篇 |
综合类 | 2892篇 |
化学工业 | 7093篇 |
金属工艺 | 3954篇 |
机械仪表 | 2555篇 |
建筑科学 | 2021篇 |
矿业工程 | 543篇 |
能源动力 | 1425篇 |
轻工业 | 2209篇 |
水利工程 | 362篇 |
石油天然气 | 1767篇 |
武器工业 | 355篇 |
无线电 | 5064篇 |
一般工业技术 | 7197篇 |
冶金工业 | 1028篇 |
原子能技术 | 472篇 |
自动化技术 | 2570篇 |
出版年
2024年 | 78篇 |
2023年 | 398篇 |
2022年 | 641篇 |
2021年 | 819篇 |
2020年 | 901篇 |
2019年 | 792篇 |
2018年 | 770篇 |
2017年 | 1114篇 |
2016年 | 1084篇 |
2015年 | 1104篇 |
2014年 | 1728篇 |
2013年 | 1961篇 |
2012年 | 2287篇 |
2011年 | 2772篇 |
2010年 | 2125篇 |
2009年 | 2247篇 |
2008年 | 2030篇 |
2007年 | 2737篇 |
2006年 | 2443篇 |
2005年 | 2071篇 |
2004年 | 1936篇 |
2003年 | 1706篇 |
2002年 | 1417篇 |
2001年 | 1348篇 |
2000年 | 1132篇 |
1999年 | 984篇 |
1998年 | 831篇 |
1997年 | 634篇 |
1996年 | 561篇 |
1995年 | 469篇 |
1994年 | 408篇 |
1993年 | 338篇 |
1992年 | 245篇 |
1991年 | 175篇 |
1990年 | 112篇 |
1989年 | 126篇 |
1988年 | 80篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 20篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1959年 | 5篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
101.
102.
103.
104.
加氢处理润滑油基础油各组分对光安定性的影响 总被引:2,自引:1,他引:1
将经紫外光照前后的加氢处理润滑油基础油分离为饱和烃、轻质芳烃、中质芳烃、重质芳烃和极性组分,分别采用薄层色谱、质谱和紫外吸收光谱分析了各组分的烃组成、硫和氮含量的变化,并通过将从原料油中分离出的各组分反加到光安定性好的饱和烃中,试验验证了加氢处理润滑油基础油中的重质芳烃和极性组分是光不安定组分,其中含有硫、氮的芳香杂环化合物光安定性差。 相似文献
105.
106.
Mott–Schottky and photoelectrochemical measurements were used to explore the effects of hydrogen and chloride ions on the electronic properties of the passive film on X70 micro-alloyed steel in a solution of 0.5 M NaHCO3. Mott–Schottky analyses have shown that hydrogen increases the capacitance and donor density, and decreases the flat band potential and the space charge layer thickness of the passive film. The photocurrent of the film is remarkably increased by hydrogen. The effects of hydrogen become more pronounced with an increase in the hydrogen charging current densities. Hydrogen has no noticeable effect on the band gap energy Eg and the process by which hole-electron pairs are photo-generated in the film. The presence of chloride ions in the solution produces some similar effects on the electronic properties of the passive film to those observed with hydrogen, but reduces the photocurrent and increases the band gap energy of the film. No significant synergistic effects on the electronic properties of the passive film were observed in the presence of hydrogen and Cl−. These results provide very useful information for elucidating the mechanism by which hydrogen changes the properties of passive film and then promotes localized corrosion. 相似文献
107.
Toshiharu Makino Hiromitsu Kato Sung-Gi Ri Yigang Chen Hideyo Okushi 《Diamond and Related Materials》2005,14(11-12):1995
Electrical properties of homoepitaxial diamond p–n+ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 105 at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density Ni of the p–n+ junction is not uniform and Ni at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce Ni at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n+ interface and incorporating during the growth of p-type layer, which makes to reduce Ni at the vicinity of the p–n+ interface. 相似文献
108.
本文综术了集成电路工艺的Cu布线中Cu薄膜化学气相沉积(CVD)的研究背景,详细介绍了CVD生长Cu金属薄膜的国内外研究进展及CVD对前趋物的要求,并对前趋物的一些物理、化学性质进行了总结,最后,对薄膜沉积的计算机摸拟作了简要介绍。 相似文献
109.
110.
In this paper, we examine, both experimentally and theoretically, the kinetics of formation and microstructure of product
phases in thin film reactions, using the Nb/Al and Ti/Al systems as our prototypes. The results of calorimetry and microscopy
studies are interpreted using simple kinetic and morphology models. In particular, the kinetic models employed here focus
on the nucleation and growth components of the phase formation process and the morphology models provide a starting point
for the classification of product grain structures.
An erratum to this article is available at . 相似文献