全文获取类型
收费全文 | 46610篇 |
免费 | 4720篇 |
国内免费 | 2131篇 |
专业分类
电工技术 | 2722篇 |
技术理论 | 2篇 |
综合类 | 2699篇 |
化学工业 | 7913篇 |
金属工艺 | 2761篇 |
机械仪表 | 3087篇 |
建筑科学 | 3273篇 |
矿业工程 | 1328篇 |
能源动力 | 1357篇 |
轻工业 | 3522篇 |
水利工程 | 726篇 |
石油天然气 | 2636篇 |
武器工业 | 350篇 |
无线电 | 5739篇 |
一般工业技术 | 6340篇 |
冶金工业 | 2468篇 |
原子能技术 | 512篇 |
自动化技术 | 6026篇 |
出版年
2024年 | 129篇 |
2023年 | 1016篇 |
2022年 | 1540篇 |
2021年 | 2527篇 |
2020年 | 1834篇 |
2019年 | 1656篇 |
2018年 | 1748篇 |
2017年 | 1771篇 |
2016年 | 1667篇 |
2015年 | 2151篇 |
2014年 | 2534篇 |
2013年 | 2954篇 |
2012年 | 3051篇 |
2011年 | 3410篇 |
2010年 | 2677篇 |
2009年 | 2563篇 |
2008年 | 2562篇 |
2007年 | 2257篇 |
2006年 | 2352篇 |
2005年 | 1874篇 |
2004年 | 1366篇 |
2003年 | 1203篇 |
2002年 | 1129篇 |
2001年 | 980篇 |
2000年 | 922篇 |
1999年 | 964篇 |
1998年 | 810篇 |
1997年 | 702篇 |
1996年 | 617篇 |
1995年 | 519篇 |
1994年 | 405篇 |
1993年 | 270篇 |
1992年 | 225篇 |
1991年 | 198篇 |
1990年 | 169篇 |
1989年 | 151篇 |
1988年 | 100篇 |
1987年 | 84篇 |
1986年 | 57篇 |
1985年 | 48篇 |
1984年 | 34篇 |
1983年 | 37篇 |
1982年 | 31篇 |
1981年 | 23篇 |
1980年 | 31篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1976年 | 18篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
岩溶专项勘察非独立于初勘、详勘,宜采用钻探、综合物探等手段分阶段同步开展。结合南宁地铁4号线某工点工程地质及场地环境条件,确立了整体技术思路。为消除单一方法的局限性,采用高密度电法、地震映像法、井间电阻率CT结合的综合物探手段,其应用效果与初、详勘钻孔资料比对,并选择区段进行了钻探验证,较为准确地查明了岩溶发育特征。 相似文献
53.
54.
Mengwei Liu Jin Zhao Shunzo Shimai Dan Han Jian Zhang Shiwei Wang 《Journal of the American Ceramic Society》2022,105(7):4632-4638
MgAl2O4 transparent ceramics were shaped by a commonly used polyacrylic acid (PAA), which acted as both dispersant and gelling agent. The spinel slurries were prepared by ball-milling MgAl2O4 powder, PAA, and water in an attrition mill. The gelling of slurries happened at room temperature in air atmosphere without any other organic additive. The gelling mechanism was the formation of chelates between Mg2+ and carboxyl groups (-COO−) of PAA. The frequency-based testing method was applied to investigate the gelling process of the as-prepared slurry. In addition, a novel in situ characterization method based on a modified indentation testing was invented to better understand the strengthening of the wet green body with time and to guide when demolding could be carried out. After sintering, transparent MgAl2O4 ceramics with high in-line transmittance were resulted. 相似文献
55.
Yu Han Xu Cheng Gaolei Zhao Wenjiang Qiang Bingxin Huang 《Ceramics International》2021,47(9):12104-12110
The Ni-rich LiNi0.83Co0.12Mn0.05O2 (NCM83) cathode materials have drawn intensive attention due to the high energy density and low cost. However, Ni-rich LiNi1-x-yCoxMnyO2 still has the fatal weakness of poor cycle stability, limiting its further wide application. Bulk doping is an effective means to enhance the cycle stability, yet the electrochemical performances are very sensitive to the doping quantity. Here a facile method of co-precipitation is adopted to coat (Ni0.4Co0.2Mn0.4)1-xAlx(OH)2+x on precursor particles of NCM83. Al ions diffuse evenly in the NCM83 particles after sintering. The cells are operated at a high cut-off voltage of 4.5 V. The discharge capacity of NCM83 is 187.8 mAh g?1, and decays fast with cycles. The doped sample even exhibits a higher discharge capacity of 195 mAh g?1, and the capacity retention is improved to 83.8% after 200 cycles. 相似文献
56.
Tunneling nanotubes (TNTs) are recognized long membrane nanotubes connecting distance cells. In the last decade, growing evidence has shown that these subcellular structures mediate the specific transfer of cellular materials, pathogens, and electrical signals between cells. As intercellular bridges, they play a unique role in embryonic development, collective cell migration, injured cell recovery, cancer treatment resistance, and pathogen propagation. Although TNTs have been considered as potential drug targets for treatment, there is still a long way to go to translate the research findings into clinical practice. Herein, we emphasize the heterogeneous nature of TNTs by systemically summarizing the current knowledge on their morphology, structure, and biogenesis in different types of cells. Furthermore, we address the communication efficiency and biological outcomes of TNT-dependent transport related to diseases. Finally, we discuss the opportunities and challenges of TNTs as an exciting therapeutic approach by focusing on the development of efficient and safe drugs targeting TNTs. 相似文献
57.
The traditional ciphertext policy attribute-based encryption (CP-ABE) has two problems:one is that the access policy must be embedded in the ciphertext and sent, which leads to the disclosure of user爷 s privacy information, the other is that it does not support collaborative decryption, which cannot meet the actual demand of conditional collaborative decryption among multiple users. In order to deal with the above two problems at the same time, a fine-grained cooperative access control scheme with hidden policies (FCAC-HP) is proposed based on the existing CP-ABE schemes combined with blockchain technology. In FCAC-HP scheme, users are grouped by group identifier so that only users within the same group can cooperate. In the data encryption stage, the access policy is encrypted and then embedded in the ciphertext to protect the privacy information of the access policy. In the data access stage, the anonymous attribute matching technology is introduced so that only matched users can decrypt ciphertext data to improve the efficiency of the system. In this process, a smart contract is used to execute the
verification algorithm to ensure the credibility of the results. In terms of security, FCAC-HP scheme is based on the prime subgroup discriminative assumption and is proved to be indistinguishable under chosen plaintext attack (CPA) by dual system encryption technology. Experimental verification and analysis show that FCAC-HP scheme improves computational efficiency while implementing complex functions. 相似文献
58.
本文使用Prophet人工智能算法研究与预测移动通信网络“潮汐效应”现象,探索网络“潮汐效应”在优化网络资源配置实现网络降本增效的作用。Prophet人工智能算法是一种简单、有效,且易于实现的人工智能算法。通过facebook的人工智能开源框架fbprophet,研究4G网络PRB利用率等网络资源指标的“潮汐效应”,并预测这些网络资源指标在未来的变化趋势,用来指导当前4G网络减容、扩容和4/5G节电节能等,实现优化网络资源配置达到降本增效的目的。 相似文献
59.
钛酸镍(NiTiO3)是一种新型锂离子电池负极材料,采用溶胶.沉淀法可制备尺寸均匀、表面粗糙的球形NiTiO3颗粒.将制备的球形NiTiO3作为锂离子电池负极材料,具有良好的电化学性能,在0.1 C(50mA/g)时,其初始充电比容量约为375.6 mAh/g,库仑效率为52.1%;第二次充电比容量为331.3 mAh/g,库仑效率为90.9%;在1C时,其初始充电比容量为295.4mAh/g,经过前十次电池活化,循环20~100次的容量基本没有衰减,容量保持率高达99.7%.将球形NiTiO3与片状石墨复合,可提高首次库仑效率,改善循环性能,增加电子导电率,减小电池极化,有利于NiTiO3锂离子电池负极材料的工业应用. 相似文献
60.
Yue Chen Peng Han Bin Ma Xuefen Wang Meihu Ma Ning Qiu Xing Fu 《International Journal of Food Science & Technology》2022,57(5):2590-2599
Heat treatment will affect the nutritional properties and potential bioactivity of food materials. The aim of this work was to evaluate the effect of different thermal treatment (4, 56, 65 and 100 ℃) and in vitro gastrointestinal digestion on the antioxidant activity of egg white hydrolysate. The results demonstrated that egg white hydrolysate treated at 65 ℃ exhibited the highest antioxidant. Remarkably, the simulated digestion significantly increased antioxidant activity of egg white hydrolysate. Furthermore, we identified twenty-four potential antioxidant peptides by performing mass spectrometry and bioinformatic analysis. Six peptides were selected based on the activity prediction score of the online tool. The results showed that P6 (ACPECPK) possessed the most outstanding antioxidant properties and had low cytotoxicity and allergenicity. Bioinformatics technology combined with biochemical assays may offer a way for discovering novel antioxidant peptides from different kinds of food under various heat treatment conditions. 相似文献