全文获取类型
收费全文 | 222842篇 |
免费 | 22985篇 |
国内免费 | 13527篇 |
专业分类
电工技术 | 17813篇 |
技术理论 | 5篇 |
综合类 | 19758篇 |
化学工业 | 32419篇 |
金属工艺 | 13310篇 |
机械仪表 | 14653篇 |
建筑科学 | 18524篇 |
矿业工程 | 6919篇 |
能源动力 | 6319篇 |
轻工业 | 19623篇 |
水利工程 | 5433篇 |
石油天然气 | 10240篇 |
武器工业 | 2564篇 |
无线电 | 26327篇 |
一般工业技术 | 22107篇 |
冶金工业 | 8450篇 |
原子能技术 | 2476篇 |
自动化技术 | 32414篇 |
出版年
2024年 | 943篇 |
2023年 | 3428篇 |
2022年 | 7166篇 |
2021年 | 9825篇 |
2020年 | 7355篇 |
2019年 | 5739篇 |
2018年 | 6303篇 |
2017年 | 7277篇 |
2016年 | 6465篇 |
2015年 | 9748篇 |
2014年 | 12571篇 |
2013年 | 14762篇 |
2012年 | 17307篇 |
2011年 | 18257篇 |
2010年 | 16941篇 |
2009年 | 16028篇 |
2008年 | 15943篇 |
2007年 | 14990篇 |
2006年 | 13683篇 |
2005年 | 10788篇 |
2004年 | 7584篇 |
2003年 | 6315篇 |
2002年 | 6182篇 |
2001年 | 5367篇 |
2000年 | 4277篇 |
1999年 | 3291篇 |
1998年 | 2094篇 |
1997年 | 1678篇 |
1996年 | 1582篇 |
1995年 | 1343篇 |
1994年 | 1043篇 |
1993年 | 667篇 |
1992年 | 534篇 |
1991年 | 400篇 |
1990年 | 308篇 |
1989年 | 270篇 |
1988年 | 201篇 |
1987年 | 127篇 |
1986年 | 108篇 |
1985年 | 51篇 |
1984年 | 49篇 |
1983年 | 33篇 |
1982年 | 39篇 |
1981年 | 42篇 |
1980年 | 58篇 |
1979年 | 35篇 |
1978年 | 11篇 |
1976年 | 14篇 |
1959年 | 14篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
71.
Priyadarshi Chakraborty Yiming Tang Tomoya Yamamoto Yifei Yao Tom Guterman Shai Zilberzwige-Tal Nofar Adadi Wei Ji Tal Dvir Ayyalusamy Ramamoorthy Guanghong Wei Ehud Gazit 《Advanced materials (Deerfield Beach, Fla.)》2020,32(9):1906043
Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications. 相似文献
72.
刘伟 《信息技术与信息化》2015,(2):80-81
本文据国内矫直机的使用情况,提出完善弯辊功能,解决辊缝标定清零及运行中的问题,提升轧钢厂运行效率与产品质量。 相似文献
73.
本文提出了一种基于分散加载技术实现Boot程序和用户应用程序在同一个工程编写开发的固件更新方法 .通过编写分散加载规范文件在工程中实现代码存储区分区.为了保证固件更新的稳定性和可靠性,在固件下载过程中引入CRC校验、丢包错包重传等容错技术.实验结果 验证了方法的有效性和可靠性. 相似文献
74.
75.
76.
在伯克氏菌Bth264野生株产新型抗癌药物Thailandepsin A以及调节基因tdp R正向调控Thailandepsin A生物合成的基础上,利用基因工程菌Bth264/p BMTL3-tdp R发酵生产Thailandepsin A,以提高产量。以0.5%乳糖为诱导剂,确定最佳诱导条件:发酵15 h添加乳糖,诱导时间6 h;通过单因素实验,确定葡萄糖和胰蛋白胨作为碳氮源、装液量65/250 m L以及接种量1%;同时结合优化发酵培养基进行发酵,Thailandepsin A产量达到252.14 mg·L-1,比优化前的产量提高56%;另外在发酵过程中,添加大孔树脂HP-20原位吸附产物,Thailandepsin A产量可达283.75 mg·L-1,比不加树脂提高13.8%;最后,基于RT-PCR和比较Ct值法,基因工程菌和野生菌相比,Thailandepsin A生物合成基因tdp B、tdp C1的转录水平分别提高11.4倍和6.0倍,对应的产量增加4.6倍,从而在很大程度上说明调节基因tdp R的过表达促进生物合成基因转录水平的提高以及产量的增加。 相似文献
77.
In this study, 0.95?Sr0.7Ba0.3Nb2O6-0.05CaTiO3-x wt% Er2O3 ceramics (SBNCTEx; x?=?0–5) were synthesized using traditional solid-state method, and we investigated the microstructure, energy storage properties as well as the relationship between dielectric breakdown strength and interfacial polarization. As compared with pure 0.95?Sr0.7Ba0.3Nb2O6-0.05CaTiO3 ceramics, the Er2O3 dopants suppressed the grain growth of SBNCTEx, and the doped ones showed the dense microstructure. The secondary phase was found for x?≥?1 according to the EDS results, and the influence of the secondary phase on relative dielectric breakdown strength has also been studied. The dielectric breakdown strength increased from 18.1?kV/mm to 34.4?kV/mm, which is good for energy storage. The energy storage density of 0.28?J/cm3 and the energy storage efficiency of 91.4% were obtained in the SBNCTE5 ceramics. The results indicate that SBNCTE ceramics can be used as energy storage capacitors. 相似文献
78.
Yafei Liu Zhilong Fu Xingyu Chen Yaxin Wei Bo Zhang Aimin Chang 《Journal of the American Ceramic Society》2021,104(5):2134-2142
Rare-earth ions doped Ca0.9R0.1CeNbMoO8 (R = Y, Sm, Nd, La) ceramics have been successfully prepared by solid-state method, and their modifications to the microstructure and electrical properties are also investigated. The rare-earth ions doped ceramics exhibit the scheelite structure. With the increase in the radius of rare-earth ions, the lattice distortion and bond interaction will be enhanced, and the consistency of grain size will be reduced. The ceramics exhibit negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 473 K-1273 K, and the activation energy decreases with the increase of the radius of rare-earth ions. Rare-earth ions doping can increase the content of Ce3+ ions and promote the conductivity of ceramics. Except for Sm3+-doped ceramics, the high-temperature aging rate of other ceramics is less than 2%. The existence of some metastable Sm2+ ions in Sm3+-doped ceramics not only increases the activation energy, but also reduces the high-temperature stability of the ceramics. 相似文献
80.
Shuyi Fu Wenrui Feng Ying Jia Tielong Deng Wenzhong Wang Guling Zhang Junli Fu 《International Journal of Hydrogen Energy》2021,46(21):11544-11555
ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S. 相似文献