全文获取类型
收费全文 | 7084篇 |
免费 | 129篇 |
专业分类
电工技术 | 85篇 |
综合类 | 1篇 |
化学工业 | 902篇 |
金属工艺 | 108篇 |
机械仪表 | 117篇 |
建筑科学 | 246篇 |
矿业工程 | 34篇 |
能源动力 | 119篇 |
轻工业 | 597篇 |
水利工程 | 59篇 |
石油天然气 | 22篇 |
武器工业 | 1篇 |
无线电 | 710篇 |
一般工业技术 | 921篇 |
冶金工业 | 2351篇 |
原子能技术 | 49篇 |
自动化技术 | 891篇 |
出版年
2021年 | 44篇 |
2020年 | 39篇 |
2019年 | 76篇 |
2018年 | 84篇 |
2017年 | 62篇 |
2016年 | 70篇 |
2015年 | 67篇 |
2014年 | 98篇 |
2013年 | 301篇 |
2012年 | 164篇 |
2011年 | 243篇 |
2010年 | 176篇 |
2009年 | 194篇 |
2008年 | 234篇 |
2007年 | 240篇 |
2006年 | 231篇 |
2005年 | 206篇 |
2004年 | 181篇 |
2003年 | 154篇 |
2002年 | 160篇 |
2001年 | 155篇 |
2000年 | 126篇 |
1999年 | 154篇 |
1998年 | 522篇 |
1997年 | 362篇 |
1996年 | 250篇 |
1995年 | 211篇 |
1994年 | 201篇 |
1993年 | 194篇 |
1992年 | 126篇 |
1991年 | 82篇 |
1990年 | 122篇 |
1989年 | 109篇 |
1988年 | 80篇 |
1987年 | 91篇 |
1986年 | 86篇 |
1985年 | 108篇 |
1984年 | 100篇 |
1983年 | 82篇 |
1982年 | 67篇 |
1981年 | 61篇 |
1980年 | 64篇 |
1979年 | 75篇 |
1978年 | 65篇 |
1977年 | 89篇 |
1976年 | 178篇 |
1975年 | 61篇 |
1974年 | 46篇 |
1973年 | 47篇 |
1972年 | 39篇 |
排序方式: 共有7213条查询结果,搜索用时 15 毫秒
1.
Guilherme M. Martins Cristiano Fantini Roberto L. Moreira Anderson Dias 《Ceramics International》2021,47(11):15202-15209
In this work, Gd2Ge2O7 polymorphs were obtained by solid-state reactions at 1100–1300 °C. Structural and vibrational features were investigated by X-ray diffraction and Raman spectroscopy. For the triclinic (space group P1) polymorph, all the predicted phonons were discerned in perfect agreement with the group theory calculations, while for the tetragonal polymorph (space group P41212), 53 bands of the 81 predicted modes could be identified and characterized. The Gd3+ 4f-4f electronic transitions were investigated by diffuse reflectance spectroscopy in the range 200–340 nm. By applying the Kubelka-Munk function, it was possible to determine the bandgap values for all ceramics studied. The tetragonal polymorph exhibited higher bandgap values (5.88 eV) than the triclinic one (5.59 eV), which are both more energetic than other pyrochlore polymorphs reported in the literature. The results indicate that the presence of polymorphism in Gd2Ge2O7 ceramics can be used to produce tailor-made materials since their crystal structures have a strong influence on their optical properties. Consequently, these properties could be used to tuning the optical properties of Gd-containing materials to sensitize and transfer energy to other luminescent lanthanide ions, aiming for innovative applications. 相似文献
2.
Liangyou Lin Timothy W. Jones Terry Chien-Jen Yang Noel W. Duffy Jinhua Li Li Zhao Bo Chi Xianbao Wang Gregory J. Wilson 《Advanced functional materials》2021,31(5):2008300
In the past decade, the perovskite solar cell (PSC) has attracted tremendous attention thanks to the substantial efforts in improving the power conversion efficiency from 3.8% to 25.5% for single-junction devices and even perovskite-silicon tandems have reached 29.15%. This is a result of improvement in composition, solvent, interface, and dimensionality engineering. Furthermore, the long-term stability of PSCs has also been significantly improved. Such rapid developments have made PSCs a competitive candidate for next-generation photovoltaics. The electron transport layer (ETL) is one of the most important functional layers in PSCs, due to its crucial role in contributing to the overall performance of devices. This review provides an up-to-date summary of the developments in inorganic electron transport materials (ETMs) for PSCs. The three most prevalent inorganic ETMs (TiO2, SnO2, and ZnO) are examined with a focus on the effects of synthesis and preparation methods, as well as an introduction to their application in tandem devices. The emerging trends in inorganic ETMs used for PSC research are also reviewed. Finally, strategies to optimize the performance of ETL in PSCs, effects the ETL has on J–V hysteresis phenomenon and long-term stability with an outlook on current challenges and further development are discussed. 相似文献
3.
An instrumented hot compression molding apparatus was fabricated to allow real-time monitoring and precise temperature control during the compaction and consolidation of large polyether ether ketone (PEEK) products. The objective was to determine the impact of controlled variables on the properties of the molded article. Four different strategies were designed to control the mold thermal profiles. The average crystallinity in a commercial molding process is restricted due to large thermal masses with low thermal conductivity. In contrast, this research was able to reduce the crystallinity range from 33% to 6% by developing a special controlled apparatus and implementing new processing methodologies. In this study, PEEK showed a significant increase in the modulus compared to typical values measured on commercially produced analogs, and a higher degree of property uniformity. In a single commercially molded PEEK billet, compressive modulus variability was 13% at room temperature, and 21% at 225°C. Properties of billets produced using the laboratory apparatus showed a reduction in variability to 2%. 相似文献
4.
5.
Ricardo Cambraia Parreira Diana Paola Gmez‐Mendoza Itamar Couto Guedes de Jesus Rafael Pereira Lemos Anderson Kennedy Santos Cristiana Perdigo Rezende Henrique Csar Pereira Figueiredo Mauro Cunha Xavier Pinto Frank Kjeldsen Silvia Guatimosim Rodrigo Ribeiro Resende Thiago Verano‐Braga 《Proteomics. Clinical applications》2020,14(4)
6.
7.
Marcelo Fernandes Cipreste Michele Rocha de Rezende Marlon Luiz Hneda Anderson Maia Peres Alexandre Alberto Chaves Cotta Verônica de Carvalho Teixeira Waldemar Augusto de Almeida Macedo Edésia Martins Barros de Sousa 《Ceramics International》2018,44(15):17800-17811
Hydroxyapatite (HA) nanoparticles (NPs) doped with different radioisotopes for use as theranostic systems play an important role in scientific research nowadays due to their ability to simultaneously act in the treatment and diagnosis of various types of cancers. In this work, we describe the synthesis and characterization of a hydroxyapatite/tenorite nanocomposite functionalized with folic acid, representing a nanotheranostic material with potential for application as an agent in positron emission tomography imaging systems and to act specifically in the treatment and diagnosis of osteosarcoma. 64Cu and 32P were produced by nuclear activation in the TRIGA reactor at CDTN. The obtained samples were characterized by XRD with Rietveld refinement, XAFS, SEM, BET, TGA, FTIR, CHN, ICP-AES, XPS and gamma spectroscopy. We investigated how CuO grows in HA NPs, the stability of the interactions between CuO and HA constituents and the interactions between folic acid and the surface of the HA NPs. The results indicate the formation of a second phase (tenorite) besides hydroxyapatite, and that the interactions between the two phases are stable, resulting in a nanocomposite. Furthermore, the activation of 64Cu and 32P inside the HA matrix, through the exposition to a neutron flux, produces a theranostic material of interest for biological tests. 相似文献
8.
9.
10.