全文获取类型
收费全文 | 3134篇 |
免费 | 494篇 |
国内免费 | 392篇 |
专业分类
化学 | 2437篇 |
晶体学 | 33篇 |
力学 | 174篇 |
综合类 | 40篇 |
数学 | 323篇 |
物理学 | 1013篇 |
出版年
2024年 | 11篇 |
2023年 | 61篇 |
2022年 | 95篇 |
2021年 | 120篇 |
2020年 | 138篇 |
2019年 | 128篇 |
2018年 | 95篇 |
2017年 | 103篇 |
2016年 | 143篇 |
2015年 | 133篇 |
2014年 | 187篇 |
2013年 | 225篇 |
2012年 | 252篇 |
2011年 | 303篇 |
2010年 | 199篇 |
2009年 | 170篇 |
2008年 | 184篇 |
2007年 | 179篇 |
2006年 | 163篇 |
2005年 | 141篇 |
2004年 | 117篇 |
2003年 | 94篇 |
2002年 | 94篇 |
2001年 | 84篇 |
2000年 | 77篇 |
1999年 | 80篇 |
1998年 | 75篇 |
1997年 | 52篇 |
1996年 | 54篇 |
1995年 | 40篇 |
1994年 | 43篇 |
1993年 | 29篇 |
1992年 | 37篇 |
1991年 | 15篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4020条查询结果,搜索用时 31 毫秒
961.
Hao Zhuo Dao-Bin Guan Jia-Cun He Prof. Dr. Hai-Bing Xu Prof. Dr. Ming-Hua Zeng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16204-16211
We designed two near-infrared (NIR) lanthanide complexes [( L )2-Nd(NO3)3] ( L =TPE2-BPY for 1 , TPE-BPY for 2 ) by employing aggregation-induced emission (AIE)-active tetraphenylethylene (TPE) derivatives as sensitizers, which possessed matched energy to NdIII, prevented competitive deactivation under aggregation, even shifted the excitation window toward 600 nm by twisted intramolecular charge transfer. Furthermore, benefiting from the 4 f electron shielding effect and antenna effect, the enhanced excitation energies of the AIE-active sensitizers by structural rigidification transferred into the inert NdIII excited state through 3LMCT, affording the first aggregation-induced phosphorescence enhancement (AIPE)-active discrete NIR-emitting lanthanide complexes. As 1 equipped with more AIE-active TPE than 2 , L →Nd energy transfer efficiency in the former was higher than that in the latter under the same conditions. Consequently, the crystal of 1 exhibited one of the longest lifetimes (9.69 μs) among NdIII-based complexes containing C−H bonds. 相似文献
962.
963.
964.
Dr. Nadezhda B. Tamm Runnan Guan Prof. Shangfeng Yang Prof. Sergey I. Troyanov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(3):616-619
Data concerning the isomeric composition of C98 and the chemistry of C98 derivatives are scarce due to very low abundance of C98 in the fullerene soot. Trifluoromethylation of C98-containing mixtures followed by HPLC separation of CF3 derivatives and single crystal X-ray diffraction study resulted in structural characterization of four compounds C98(248)(CF3)18/20, C98(116)(CF3)18, and C98(120)(CF3)20. To date, these compounds represent the largest fullerenes isolated as CF3 derivatives with experimentally determined molecular structures. The addition patterns of C98(CF3)18/20 are discussed in detail revealing the stabilizing factors, such as isolated double C=C bonds and benzenoid rings on C98 fullerene cages. A detailed comparison with the addition patterns of the known C98Cln allowed us to contribute to the better understanding the chemistry of elusive C98 fullerene. 相似文献
965.
A visible-light-mediated metal-free thiocyanate radical addition/ipso-cyclization/oxidation cascade reaction for the synthesis of thiocyanato-containing azaspirotrienediones from N-phenylpropynamides is described. Cheap and readily available ammonium thiocyanate was used as a precursor to the thiocyanate free radical, which undergoes a radical addition reaction with the alkyne, followed by selective ipso-cyclization and oxidation to afford the dearomatized products. No product of ortho-cyclization was detected. The reaction completes the synthesis of C–S, C–C, and CO bonds in one pot, with abundant and renewable air oxygen as the sole sacrificial reagent and oxygen source. 相似文献
966.
967.
968.
We reported here an efficient regioselective protection strategy for xylose with two-step successive protections on 4- and 2-OH. This method enables the expeditious preparation of various xylose building blocks (3a–c, 5, 6). The rapid selective 2,4-protection especially facilitates the synthesis of 3-substituted xyloside structures. By this approach, typical arabino-α-1,3-xyloside disaccharide and trisaccharide, as fragment structure units from arabinoxylans, have been successfully synthesized. 相似文献
969.
使用液相包覆工艺对LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA)材料进行FePO_4包覆改性,利用FePO_4优异的结构稳定性与热稳定性,对NCA的长期可靠性与安全性能进行改良。重点研究FePO_4包覆对NCA材料的改性效果,以及不同包覆量造成的NCA材料电化学性能差异。表面包覆的FePO_4保护层,能够防止NCA材料与电解液直接接触发生副反应,抑制长期循环过程中过渡金属离子的溶出,保持结构的长期稳定性。当包覆量为1.0%(w/w)时,NCA材料表现出最优的综合性能,充放电循环800次后,容量保持率依然高达95%,25℃下存储100 d后,容量保持率也高于95%,达到了兼顾能量密度、使用寿命及安全性能的理想效果。 相似文献
970.