全文获取类型
收费全文 | 86768篇 |
免费 | 9427篇 |
国内免费 | 5100篇 |
专业分类
电工技术 | 6316篇 |
技术理论 | 3篇 |
综合类 | 7392篇 |
化学工业 | 13713篇 |
金属工艺 | 4751篇 |
机械仪表 | 5454篇 |
建筑科学 | 6771篇 |
矿业工程 | 2583篇 |
能源动力 | 2479篇 |
轻工业 | 8664篇 |
水利工程 | 2030篇 |
石油天然气 | 4273篇 |
武器工业 | 920篇 |
无线电 | 10117篇 |
一般工业技术 | 8896篇 |
冶金工业 | 3237篇 |
原子能技术 | 885篇 |
自动化技术 | 12811篇 |
出版年
2024年 | 533篇 |
2023年 | 1855篇 |
2022年 | 3578篇 |
2021年 | 4686篇 |
2020年 | 3356篇 |
2019年 | 2646篇 |
2018年 | 2811篇 |
2017年 | 3087篇 |
2016年 | 2705篇 |
2015年 | 4022篇 |
2014年 | 4878篇 |
2013年 | 5481篇 |
2012年 | 6541篇 |
2011年 | 6826篇 |
2010年 | 6013篇 |
2009年 | 5776篇 |
2008年 | 5576篇 |
2007年 | 5151篇 |
2006年 | 4695篇 |
2005年 | 3902篇 |
2004年 | 2852篇 |
2003年 | 2441篇 |
2002年 | 2550篇 |
2001年 | 2067篇 |
2000年 | 1557篇 |
1999年 | 1251篇 |
1998年 | 840篇 |
1997年 | 723篇 |
1996年 | 628篇 |
1995年 | 520篇 |
1994年 | 414篇 |
1993年 | 326篇 |
1992年 | 250篇 |
1991年 | 187篇 |
1990年 | 113篇 |
1989年 | 102篇 |
1988年 | 100篇 |
1987年 | 54篇 |
1986年 | 50篇 |
1985年 | 28篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 26篇 |
1981年 | 11篇 |
1980年 | 27篇 |
1979年 | 11篇 |
1978年 | 1篇 |
1959年 | 3篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Xiao-Ya Shangguan Bao-Lun Fang Chen-Xiao Xu Yuan Tan Yan-Gang Chen Zhi-Jun Xia Wei Chen 《Ceramics International》2021,47(5):6318-6328
A series of direct Z-scheme FeIn2S4/Bi2WO6 hierarchical heterostructures with intimate interface contacts were synthesized by in-situ growth route and characterized by systematical analyses. All as-prepared FeIn2S4/Bi2WO6 nanocomposites showed significantly enhanced photocatalytic activity towards photodegradation for the removal of tetracycline hydrochloride (TCH) in comparison with individual FeIn2S4 and Bi2WO6. Meanwhile, the highest photocatalytic degradation activity can be achieved by modulating adding amount of FeIn2S4 in FeIn2S4/Bi2WO6 nanocomposites and the optimized component ratio of FeIn2S4 to Bi2WO6 is determined to be 10 wt%. The enhanced photocatalytic activity could be ascribed to efficient separation between photogenerated holes and electrons based on the construction of direct Z-scheme system. The high photocatalytic stability of resultant 10 wt% FeIn2S4/Bi2WO6 nanocomposites was revealed through six successive recycling reactions. The main intermediate generated during TCH photodegradation was explored by HPLC-MS. Besides, the direct Z-scheme photocatalytic mechanism was confirmed by band position analysis, electron spin resonance (ESR) and active species capture experiment. 相似文献
42.
Qiang Liu Xinyu Mao Xiaoying Li Penghui Chen Xin Liu Ziyu Liu Danyang Zhu Haohong Chen Tengfei Xie Jiang Li 《Journal of the American Ceramic Society》2021,104(10):4927-4931
0.5 at.% Cr:ZnGa2O4 precursor was synthesized by the co-precipitation method with nitrates as raw materials, using ammonium carbonate as the precipitant. Low-agglomerated Cr:ZnGa2O4 powders with an average particle size of 43 nm were obtained by calcining the precursor at 900℃ for 4 h. Using the powders as starting materials, 0.5 at.% Cr:ZnGa2O4 ceramics with an average grain size of about 515 nm were prepared by presintering at 1150℃ for 5 h in air and HIP post-treatment at 1100℃ for 3 h under 200 MPa Ar. The in-line transmittance of 0.5 at.% Cr:ZnGa2O4 ceramics with a thickness of 1.3 mm reaches 59.5% at the wavelength of 700 nm. The Cr:ZnGa2O4 ceramics can be effectively excited by visible light and produce persistent luminescence at 700 nm. For Cr:ZnGa2O4 transparent ceramics, the brightness of afterglow was larger than 0.32 mcd/m2 after 30 min, which is far superior to that of Cr:ZnGa2O4 persistent luminescence powders. 相似文献
43.
山西某矿5308底抽巷在掘进过程中速度慢、效率低,直接影响工作面的瓦斯抽采,为了改善上述情形,对炮孔间距进行研究。通过使用ANSYS软件对不同炮孔间距下快速掘进效果的模拟分析,并经现场验证,得出了适应该矿的最佳炮孔间距。结果表明:炮孔间距为500 mm时,爆破产生裂隙发育范围和岩石损伤区域都最大,快速掘进的效果最好。 相似文献
44.
45.
46.
47.
In this research, the three‐dimensional structural and colorimetric modeling of three‐dimensional woven fabrics was conducted for accurate color predictions. One‐hundred forty single‐ and double‐layered woven samples in a wide range of colors were produced. With the consideration of their three‐dimensional structural parameters, three‐dimensional color prediction models, K/S‐, R‐, and L*a*b*‐based models, were developed through the optimization of previous two‐dimensional models which have been reported to be the three most accurate models for single‐layered woven structures. The accuracy of the new three‐dimensional models was evaluated by calculating the color differences ΔL*, ΔC*, Δh°, and ΔECMC(2:1) between the measured and the predicted colors of the samples, and then the error values were compared to those of the two‐dimensional models. As a result, there has been an overall improvement in color predictions of all models with a decrease in ΔECMC(2:1) from 10.30 to 5.25 units on average after the three‐dimensional modeling. 相似文献
48.
49.