全文获取类型
收费全文 | 117302篇 |
免费 | 13483篇 |
国内免费 | 9008篇 |
专业分类
电工技术 | 10036篇 |
技术理论 | 1篇 |
综合类 | 12781篇 |
化学工业 | 15819篇 |
金属工艺 | 8149篇 |
机械仪表 | 8319篇 |
建筑科学 | 8786篇 |
矿业工程 | 4092篇 |
能源动力 | 3155篇 |
轻工业 | 12060篇 |
水利工程 | 3431篇 |
石油天然气 | 4135篇 |
武器工业 | 1599篇 |
无线电 | 12348篇 |
一般工业技术 | 10425篇 |
冶金工业 | 4571篇 |
原子能技术 | 2024篇 |
自动化技术 | 18062篇 |
出版年
2024年 | 326篇 |
2023年 | 1745篇 |
2022年 | 4058篇 |
2021年 | 5337篇 |
2020年 | 3866篇 |
2019年 | 2776篇 |
2018年 | 3044篇 |
2017年 | 3333篇 |
2016年 | 3012篇 |
2015年 | 4742篇 |
2014年 | 6055篇 |
2013年 | 7393篇 |
2012年 | 8946篇 |
2011年 | 9407篇 |
2010年 | 9105篇 |
2009年 | 8864篇 |
2008年 | 9423篇 |
2007年 | 9031篇 |
2006年 | 8213篇 |
2005年 | 6776篇 |
2004年 | 4953篇 |
2003年 | 3792篇 |
2002年 | 3923篇 |
2001年 | 3569篇 |
2000年 | 2593篇 |
1999年 | 1438篇 |
1998年 | 726篇 |
1997年 | 565篇 |
1996年 | 543篇 |
1995年 | 465篇 |
1994年 | 326篇 |
1993年 | 309篇 |
1992年 | 236篇 |
1991年 | 162篇 |
1990年 | 147篇 |
1989年 | 135篇 |
1988年 | 101篇 |
1987年 | 65篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 32篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 24篇 |
1980年 | 38篇 |
1979年 | 17篇 |
1978年 | 4篇 |
1962年 | 3篇 |
1959年 | 25篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 278 毫秒
61.
Hao Liu Jinke Chen Yan Fu Zujin Zhao Ben Zhong Tang 《Advanced functional materials》2021,31(33):2103273
Sensitizing conventional fluorescence (CF) dopants with thermally activated delayed fluorescence (TADF) materials has achieved considerable progress, by which the advantages of TADF materials and CF dopants can be fully harnessed. However, the usually used co-phase configuration of CF dopant-engaged sensitizing systems often encounters exciton loss due to Dexter energy transfer (DET). Herein, an effective out-of-phase configuration is proposed to sensitize CF dopants in the fabrication of white organic light-emitting diodes (WOLEDs). Based on a new efficient sky-blue TADF luminogen DCP-BP-DPAC which has an electroluminescence (EL) peak at 486 nm and an EL efficiency of 26.6%, a green TADF material BDMAC-XT, and a red CF dopant DBP sensitized by BDMAC-XT through an out-of-phase configuration without interlayer, efficient WOLEDs are successfully fabricated. By further adopting orange TBRB or 4CzTPNBu as intermediate sensitizers, more efficient energy transfer to DBP is achieved via Förster energy transfer. Through step-by-step energy transfer and elimination of excess DET process, high-performance all-fluorescent WOLEDs are achieved, providing excellent EL efficiencies over 23.0%, and highly stable white light with a high color rendering index of 87. The outstanding EL performance and high-quality emission color demonstrate the great potential of the proposed out-of-phase design for sensitizing systems of WOLEDs. 相似文献
62.
Shuang Chen Chao Yu Zhanfang Cao Xiaoping Huang Shuai Wang Hong Zhong 《International Journal of Hydrogen Energy》2021,46(10):7037-7046
The development of efficient and stable oxygen evolution reaction (OER) catalysts is an ongoing challenge. In order to solve the problem of low oxygen evolution efficiency of the current OER catalysts, a novel material was synthesized by the incorporation of NiFeCr-LDH and MoS2, and its structural and electrochemical properties were also investigated. The introduction of MoS2 improves the electrochemical performance of NiFeCr-LDH. The polarization curve shows that the potential of composite material is only 1.50 V at a current density of 10 mA cm?2, which is far superior to commercial precious metal catalysts. In addition, the stability experiment shows that the composite material has excellent stability, and the current density has little change after 500 cycles. Furthermore, we found that some metal ions, such as Ni, Cr and Mo, exist in the form of high valence on the surface of NiFeCr-LDH@MoS2, which is also conducive to the occurrence of oxygen evolution reaction. 相似文献
63.
64.
Yunqi Li Jing Li Yang-Gang Wang Xiran Chen Mingtao Liu Zhong Zheng Xihong Peng 《International Journal of Hydrogen Energy》2021,46(24):13273-13282
In this work, density functional theory (DFT) calculations were used to investigate the mechanism of carbon corrosion on nitrogen-doped carbon support. Free energy diagrams were generated based on three proposed reaction pathways to evaluate corrosion mechanisms. The most energetically preferred mechanism on nitrogen-doped carbon was determined. The results show that the step of water dissociation to form #OH was the rate-determining step for gra-G-1N (graphene doped with graphitic N) and pyrr-G-1N (graphene doped with pyrrolic N). As for graphene doped with pyridinic N, the step of C#OC#O formation was critical. It was found that the control of nitrogen concentration was necessary for precisely designing optimized carbon materials. Abundance of nitrogen moieties aggravated the carbon corrosion. When the high potential was applied, specific types of graphitic N and pyridinic N were found to be favorable carbon modifications to improve carbon corrosion resistance. Moreover, the solvent effect was also investigated. The results provide theoretical insights and design guidelines to improve corrosion resistance in carbon support through material modification by inhibiting the adsorption of surface oxides (OH, O, and OOH). 相似文献
65.
66.
地下连续墙为地铁车站深基坑施工中的关键内容,但受现场地下水、地质条件等方面的影响,易导致地下连续墙出现渗漏现象,做好接缝渗漏处理是确保地下连续墙正常使用的必要前提.文章以工程实例为依托,深入分析了地下连续墙接缝渗漏的成因,如混凝土质量、地质条件影响等,并详细探讨了具体的处治技术,最终取得了良好的处置效果. 相似文献
67.
Xu Wang Yujie Zhong Qian Sun Dongqing Qi Fuxue Yan Quangang Xian Dong Wang Kui Du Jingyang Wang 《Journal of the American Ceramic Society》2019,102(4):2176-2186
The microstructure evolution and growth behavior of the Al2O3/Y3Al5O12(YAG)/ZrO2 ternary eutectic ceramics during directional solidification were well investigated. During directional solidification of the Al2O3/YAG/ZrO2 ternary eutectic ceramics, {} Al2O3 paralleled with {001}ZrO2 while they did not parallel with {001}YAG at the same time in the competitive growth stage. All of the interfaces parallel to each other finally. The area percentage of the Al2O3/ZrO2 and YAG/ZrO2 interfaces are 40.4 ± 0.2% and 30.8 ± 0.1%, respectively, higher than that of the Al2O3/YAG (28.8 ± 0.2%). The content of Al2O3 and YAG phases are 39.9% and 41.1%, respectively, almost double of that of ZrO2. The interfaces of Al2O3/ZrO2 and YAG/ZrO2 are shorter and more dispersed than that of the Al2O3/YAG. It was found that the interfacial energy of Al2O3/ZrO2 and YAG/ZrO2 interfaces are lower than that of Al2O3/YAG. It can be concluded that interfacial energy plays a decisive role in affecting the crystallographic orientation and interfaces distribution in the Al2O3/YAG/ZrO2 eutectic since the interfaces of Al2O3/ZrO2 and YAG/ZrO2 with lower interfacial energy can be formed more easily during directional solidification. Therefore, the contents of Al2O3/ZrO2 and YAG/ZrO2 interfaces are higher. This study can provide theoretical guidance for interface design of multi-phase materials. 相似文献
68.
仲春华 《皮革制作与环保科技》2021,(5):34-35
社会经济的快速发展对生态环境造成了较大破坏,并产生了一系列连锁反应,不利于我国可持续发展目标的实现。为此,必须要切实做好环境监测工作。本文从环境监测的概念出发,就现阶段的环境监测现状进行了分析,并在此基础上阐述了环境监测工作未来发展及优化对策,以供参考。 相似文献
69.
70.
目的 检测水产品及养殖水中丁香酚类化合物。方法 应用食品补充检验方法BJS 201908《水产品及水中丁香酚类化合物的测定》,以海水鱼、淡水鱼、海水虾、淡水虾及养殖水作为基质,测定6种丁香酚类化合物的含量。结果 通过对实际样品测定后发现,在水产品中检出了丁香酚类化合物,主要为丁香酚,检出率为28.9%,其中海水鱼相对突出。结论 本研究为丁香酚作为渔用麻醉剂提供了方法论,为丁香酚类化合物在水产运输的合理使用提供理论依据。 相似文献