全文获取类型
收费全文 | 51438篇 |
免费 | 4477篇 |
国内免费 | 2022篇 |
专业分类
电工技术 | 2636篇 |
技术理论 | 2篇 |
综合类 | 2521篇 |
化学工业 | 9143篇 |
金属工艺 | 2814篇 |
机械仪表 | 3316篇 |
建筑科学 | 3189篇 |
矿业工程 | 1301篇 |
能源动力 | 1567篇 |
轻工业 | 3420篇 |
水利工程 | 689篇 |
石油天然气 | 2499篇 |
武器工业 | 337篇 |
无线电 | 6784篇 |
一般工业技术 | 7256篇 |
冶金工业 | 3176篇 |
原子能技术 | 578篇 |
自动化技术 | 6709篇 |
出版年
2024年 | 248篇 |
2023年 | 931篇 |
2022年 | 1594篇 |
2021年 | 2281篇 |
2020年 | 1673篇 |
2019年 | 1579篇 |
2018年 | 1670篇 |
2017年 | 1676篇 |
2016年 | 1655篇 |
2015年 | 2062篇 |
2014年 | 2558篇 |
2013年 | 3216篇 |
2012年 | 3197篇 |
2011年 | 3617篇 |
2010年 | 2812篇 |
2009年 | 2853篇 |
2008年 | 2807篇 |
2007年 | 2505篇 |
2006年 | 2610篇 |
2005年 | 2114篇 |
2004年 | 1597篇 |
2003年 | 1436篇 |
2002年 | 1393篇 |
2001年 | 1181篇 |
2000年 | 1127篇 |
1999年 | 1163篇 |
1998年 | 1193篇 |
1997年 | 929篇 |
1996年 | 789篇 |
1995年 | 653篇 |
1994年 | 521篇 |
1993年 | 391篇 |
1992年 | 288篇 |
1991年 | 276篇 |
1990年 | 225篇 |
1989年 | 212篇 |
1988年 | 140篇 |
1987年 | 132篇 |
1986年 | 96篇 |
1985年 | 81篇 |
1984年 | 66篇 |
1983年 | 56篇 |
1982年 | 42篇 |
1981年 | 46篇 |
1980年 | 42篇 |
1979年 | 26篇 |
1978年 | 30篇 |
1977年 | 22篇 |
1976年 | 39篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Eui Dae Jung Amit Kumar Harit Do Hui Kim Chung Hyeon Jang Jong Hyun Park Shinuk Cho Myoung Hoon Song Han Young Woo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(30):2002333
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s. 相似文献
22.
23.
24.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。 相似文献
25.
26.
通过分析A公司在研发项目范围管理中所存在问题,提出研发项目范围管理的方法及其在C产品的应用实例,通过运用研发项目范围管理的工具和方法,改善产品开发流程,从而缩短新产品开发周期,提高响应市场的速度,并提高企业研发项目的管理能力。 相似文献
27.
28.
Peer-to-Peer Networking and Applications - P2P-TV is a TV system that receives content through a peer-to-peer network. Content is stored in the distributed manner then to be serviced to users, and... 相似文献
29.
Wai-Ching Liu Huey-Yuan Wang Lung-Chien Chen Shih-Wei Huang Chengtie Wu Ren-Jei Chung 《Ceramics International》2019,45(5):5668-5679
Tricalcium silicate (C3S) and hydroxyapatite (HAp) composites were fabricated through the sol-gel process. The aim of this research is to improve the biocompatibility of C3S through HAp addition and study the potential of using this as coating materials. The composites (HAp/C3S) were characterised by Fourier transform infrared spectrometry, thermal gravity-differential thermal analysis and X-ray diffraction. The working and setting times of cement pastes were tested using Gillmore needle. Mechanical properties were examined by nanoindentation and material testing system. In vitro biocompatibility of the materials were studied by cell attachment and viability of L929 and MG-63 cells. HAp/C3S as a coating material on gelatin film were measured with the surface roughness and imaged by scanning electron microscope. With the addition of HAp, no undesirable free CaO was detected with the synthesis by the sol-gel preparation. The pH values of HAp added groups were between 7.54 and 8.76, which were much lower than pure C3S group (pH?=?11.75). For in vitro studies, the presence of HAp could effectively enhance the cell attachment and viability of both L929 and MG-63 cells grown in the extract or directly on the composites. However, the mechanical properties of the composites were impaired as compared to pure C3S. Lastly, HAp/C3S cement could be evenly coated on gelatin film. HAp is successfully demonstrated to improve C3S biocompatibility with this new composites HAp/C3S. C-75 (75% C3S and 25% HAp), in particular, has good biocompatibility, relatively high compressive strength and can be uniformly coated onto gelatin film. Thus, C-75 is a promising material for further investigation as a coating on other biopolymers. 相似文献
30.