全文获取类型
收费全文 | 24268篇 |
免费 | 2256篇 |
国内免费 | 1151篇 |
专业分类
电工技术 | 426篇 |
技术理论 | 1篇 |
综合类 | 1181篇 |
化学工业 | 10211篇 |
金属工艺 | 743篇 |
机械仪表 | 454篇 |
建筑科学 | 1248篇 |
矿业工程 | 584篇 |
能源动力 | 482篇 |
轻工业 | 677篇 |
水利工程 | 106篇 |
石油天然气 | 2312篇 |
武器工业 | 1279篇 |
无线电 | 1607篇 |
一般工业技术 | 5542篇 |
冶金工业 | 443篇 |
原子能技术 | 95篇 |
自动化技术 | 284篇 |
出版年
2024年 | 81篇 |
2023年 | 366篇 |
2022年 | 450篇 |
2021年 | 579篇 |
2020年 | 649篇 |
2019年 | 664篇 |
2018年 | 585篇 |
2017年 | 864篇 |
2016年 | 850篇 |
2015年 | 829篇 |
2014年 | 1266篇 |
2013年 | 1378篇 |
2012年 | 1496篇 |
2011年 | 1750篇 |
2010年 | 1322篇 |
2009年 | 1373篇 |
2008年 | 1238篇 |
2007年 | 1563篇 |
2006年 | 1636篇 |
2005年 | 1329篇 |
2004年 | 1164篇 |
2003年 | 1104篇 |
2002年 | 945篇 |
2001年 | 831篇 |
2000年 | 573篇 |
1999年 | 510篇 |
1998年 | 421篇 |
1997年 | 297篇 |
1996年 | 272篇 |
1995年 | 247篇 |
1994年 | 250篇 |
1993年 | 200篇 |
1992年 | 147篇 |
1991年 | 107篇 |
1990年 | 50篇 |
1989年 | 45篇 |
1988年 | 36篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 52篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 28篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
Kim Bini Desta Gedefaw Caroline Pan Jonas M. Bjuggren Anirudh Sharma Ergang Wang Mats R. Andersson 《应用聚合物科学杂志》2019,136(27):47729
An easily accessible anthraquinone-benzodithiophene-based high bandgap polymer (PTAq) was synthesized by Stille coupling reactions in remarkably high yield (96.5%). The highest occupied molecular orbital energy level of the polymer was estimated from the onset of oxidation in a cyclic voltammetry study to be −5.7 eV. PTAq showed an orange-to-green color switching with the application of a 1.0-V external potential to the polymer film, which was visible to the naked eye. The optical behavior change was also monitored using ultraviolet–visible absorption spectroscopy and revealed a respectable 75% transmittance change when the polymer film was subjected to a 1.0-V external potential. The high color contrast observed makes PTAq one of the most promising materials for electrochromic device applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47729. 相似文献
22.
以 -二(1-羧乙基)咪唑盐(HL)和Zn(NO3)2·6H2O反应合成二维配位聚合物[Zn(L)2] n (Zn-L),产物再与K2PdCl4在四氢呋喃溶液中反应引入氮杂环卡宾-钯(NHC-Pd)催化位点,制得催化剂NHC-Pd@Zn-L,并通过PXRD、TGA、ICP、SEM、EDS和XPS进行表征。结果表明,NHC-Pd@Zn-L具有良好的热稳定性且修饰后晶体的框架结构没有发生变化,Pd以NHC-Pd的形式结合在Zn-L中,并均匀分散在配位聚合物中。将NHC-Pd@Zn-L用于催化Suzuki-Miyaura交叉偶联反应,当以苯硼酸和溴苯为底物,催化剂用量为15 mg,乙醇为溶剂,碳酸钾为碱的条件下60℃反应6 h,产率达到>99%,而且催化剂易于回收并可循环使用3次。 相似文献
23.
《Ceramics International》2022,48(8):10885-10894
Lead-free bismuth sodium titanate-strontium titanate (NBT-ST) dielectric ceramic materials have been extensively investigated energy storage materials because of their relaxor characteristics. In this study, four different lanthanide elements were introduced into the ferroelectric NBT-ST ceramic to improve their relaxor properties. The introduction of the lanthanide resulted in an increase in disorder at location A within the perovskite lattice and improved relaxor characteristics, leading to a stored energy density of more than 3.5 J/cm3. In particular, an ultrahigh recoverable stored energy density of 4.94 J/cm3 and efficiency of 88.45% were achieved at 440 kV/cm when the NBT-ST ceramic was modified with neodymium. The modified ceramic also exhibited good thermal stability in the range of 30–120 °C, as well as a fast discharge time of ~153 ns, indicating that Nd-incorporated NBT-ST is a promising candidate for electrical energy storage ceramic. 相似文献
24.
Bian Da Liu Yaxuan Aradhyula Thirumala Vasu Guo Yongxin Tang Hao Zhao Yongwu Wang Yongguang 《Ceramics International》2021,47(11):15722-15731
To enhance the tribocorrosion properties of chemically bonded phosphate ceramic coating (CBPCC), GO-ZnO was prepared and added into CBPCC. And the tribocorrosion behaviour of CBPCC was investigated. Results show that, with the introduction of GO-ZnO, the open circuit potential of CBPCC shifts in a positive direction and corrosion current density decreases. In addition, the total material loss, the total mechanical wear loss and the total electrochemical corrosion loss of CBPCC all decrease with the increase of GO-ZnO. The wear track of CBPCC after tribocorrosion without GO-ZnO is rough and porous, while the wear track becomes smooth and dense with the incorporation of GO-ZnO. The material in wear track is anchored by GO-ZnO due to the strong bond between GO-ZnO and CBPCC, which decreases the wear loss. Because of the extra force from the tribocorrosion experiment, the material anchored by GO-ZnO forms to a dense structure which prevents electrolyte diffusion into CBPCC. Moreover, GO-ZnO can block the electrolyte diffusion pathway and make it more tortuous. The resistance to the electrolyte diffusion decreases the corrosion current density and the increased wear loss due to electrochemical corrosion. 相似文献
25.
Shuo Wan Yunlong Ma Dongdong Cai Wenyuan Lin Pengsong Wang Jinyun Wang Qingdong Zheng 《Advanced functional materials》2021,31(15):2010436
Ending group halogenation is an effective strategy for modulating the energy levels, bandgaps, and intermolecular interactions of nonfullerene acceptors. Understanding the influence of different halogen atoms on the acceptor properties is of great importance for designing high-performance nonfullerene acceptors. Here, three acceptor–donor–acceptor (A-D-A) type nonfullerene acceptors (M5, M6, and M7), which are constructed by using a ladder-type heteroheptacene core without the traditional sp3 carbon-bonded side chains as the electron-rich core, and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile without or with halogen atoms as the ending groups. The nonfullerene acceptors with chlorinated (M6) and brominated (M7) ending groups exhibit broadened absorption spectra, down-shifted energy levels, and enhanced molecular ordering compared to the counterpart without any halogenated ending groups (M5). Among the nonfullerene acceptors, M6 has the strongest intermolecular π π interaction with its shortest π π interaction distance and the longest coherent length which are beneficial for enhancing the charge transport and therefore boosting the photovoltaic performance. An excellent power conversion efficiency of 15.45% is achieved for the best-performing polymer solar cell based on M6. These results suggest that the halogenated ending groups are essential for high-performance heteroheptacene-based nonfullerene acceptors considering their simultaneous enhancements in both the light-harvesting and the charge transport. 相似文献
26.
This work describes facile synthesis of a porous polymeric material ( T-HCP ) using readily available reagents. Specifically, T-HCP is a thermally stable and hypercrosslinked polymer (HCP) that is essentially microporous with a high BET specific surface area (940 m2 g?1). Triptycene based polymers are known to feature internal free volume. Thus, the incorporation of triptycene units and extensive crosslinking by an external cross-linker in T-HCP makes it a promising adsorbent for small gas capture applications. Experimental results show that T-HCP demonstrated good CO2 capture capacity of 132 mg g?1 (273 K, 1 bar). Molecular hydrogen storage capacity of T-HCP is estimated to be 17.7 mg g?1 (77 K, 1 bar). T-HCP revealed high CO2/N2 selectivity (up to 63) as well as promising CO2/CH4 (up to 9.1) selectivity suggesting its potential applicability for CO2 separation from flue and natural gases. 相似文献
27.
Komethi Muniandy 《Materials Science & Technology》2019,35(9):1016-1027
Surface deformation study of a polymer film during plastic film blowing (PFB) extrusion process though is considered essential, is difficult to execute as the process is fast and continuous. Digital image correlation (DIC) is an optical technique that is non-destructive, highly accurate and designed to measure deformations from micro to macro scale. DIC can be proposed as a reliable tool to understand the relationship of polymer structure-processing-properties. In this literature, digital image correlation, its basic principle of operation and reliability guided DIC for continuous large deformation are comprehensively explored. Versatility of DIC, and the conditions that affect the measurement algorithm as well as preceding use of DIC in polymer processes are reviewed. The implementation and potential use of DIC in PFB are described.
This review was submitted as part of the 2019 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged. 相似文献
28.
29.
30.