全文获取类型
收费全文 | 2781篇 |
免费 | 157篇 |
国内免费 | 49篇 |
专业分类
化学 | 1872篇 |
晶体学 | 12篇 |
力学 | 148篇 |
数学 | 283篇 |
物理学 | 407篇 |
无线电 | 265篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 48篇 |
2021年 | 107篇 |
2020年 | 150篇 |
2019年 | 141篇 |
2018年 | 177篇 |
2017年 | 145篇 |
2016年 | 201篇 |
2015年 | 120篇 |
2014年 | 207篇 |
2013年 | 339篇 |
2012年 | 224篇 |
2011年 | 231篇 |
2010年 | 173篇 |
2009年 | 147篇 |
2008年 | 152篇 |
2007年 | 110篇 |
2006年 | 64篇 |
2005年 | 41篇 |
2004年 | 36篇 |
2003年 | 42篇 |
2002年 | 28篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有2987条查询结果,搜索用时 15 毫秒
81.
82.
Rostami Mojtaba Aghajanzadeh Mozhgan Zamani Mostafa Manjili Hamidreza Kheiri Danafar Hossein 《Research on Chemical Intermediates》2018,44(3):1889-1904
Research on Chemical Intermediates - In this study, a kind of magnetic Fe3O4@mTiO2-GO (where m was shorted mesoporous) hybrids with core–shell nano-structure for controlled dual targeted drug... 相似文献
83.
Hashemi Karouei Seyed Hossein Ajarostaghi Seyed Soheil Mousavi Gorji-Bandpy Mofid Hosseini Fard Seyed Reza 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1455-1466
Journal of Thermal Analysis and Calorimetry - In the present study, the effect of inserting an innovative curved turbulator and utilizing two types of hybrid nanofluids on thermal performance in a... 相似文献
84.
In this paper, we investigate the complete moment convergence for dependent linear processes with random coefficients to form 相似文献
85.
Hosseini Seyed Ghorban Gholami Setareh Mahyari Mojtaba 《Research on Chemical Intermediates》2019,45(3):1527-1543
Research on Chemical Intermediates - Nickel cobalt bimetallic nanoparticles (NiCo NPs) with different molar ratios were stabilized over three-dimensional nitrogen-doped graphene [3D-(N)G] by a... 相似文献
86.
Neda Choodari Milani Yazdan Maghsoud Mahdieh Hosseini Abouzar Babaei Hamidreza Rahmani Stephen Mark Roe Khodayar Gholivand 《应用有机金属化学》2020,34(4):e5526
Seven novel complexes (C1–C7) were synthesized by the interaction between Cu(I) metal cation, L1, L2, L3, X and PPh3, where L1–L3 are derivatives of ((pyridine-2-ylmethylene)amino)phenol imine ligands and X = Cl−, Br−, I−, NCS−. All the complexes were characterized using infrared, 1H NMR and 31P NMR spectroscopies. The crystal structures of C1–C7 were also determined using single-crystal X-ray diffraction. The organization of the crystal structures and the intermolecular interactions are discussed. The supramolecular assemblies are driven by cooperative π…π interactions and hydrogen bonds, followed by CH…π linkages. The potential anticancer effect of C1–C7 was assessed for human glioblastoma cells using several anticancer experiments, which showed that these complexes have marked anticancer property against U87 cells. It was also found that the minimum and maximum anticancer effects are shown by C3- and C4-treated samples, respectively. Furthermore, theoretical approaches were used to investigate the nature of metal–ligand interactions which suggest a closed-shell and electrostatic character for Cu…N, Cu…P and Cu…X bonds. 相似文献
87.
In this study, a novel Cu-immobilized ionic liquid (IL)was designed, characterized, and employed as both promoter and solvent in the synthesis of some dihydropyrano[2,3-c]pyrazoles. The synthesized ionic liquid was characterized by 1H NMR, 13C NMR, FTIR, ICP and EDX analysis and showed high catalytic activity to proceed the synthesis of bioactive dihydropyrano[2,3-c]pyrazole derivatives. This method has the advantage of using the IL as a green medium for the synthesize of the products in high to excellent yields within short reaction times. 相似文献
88.
Mahmoud Nasrollahzadeh Mohaddeseh Sajjadi Hartmut Komber Hossein Ali Khonakdar S. Mohammad Sajadi 《应用有机金属化学》2019,33(7)
In the present work, for the first time we have designed a novel approach for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles using reduced graphene oxide (rGO) decorated with Cu‐Ni bimetallic nanoparticles (NPs). In situ synthesis of Cu/Ni/rGO nanocomposite was performed by a cost efficient, surfactant‐free and environmentally benign method using Crataegus azarolus var. aronia L. leaf extract as a stabilizing and reducing agent. Phytochemicals present in the extract can be used to reduce Cu2+ and Ni2+ ions and GO to Cu NPs, Ni NPs and rGO, respectively. Analyses by means of FT‐IR, UV–Vis, EDS, TEM, FESEM, XRD and elemental mapping confirmed the Cu/Ni/rGO formation and also FT‐IR, NMR, and mass spectroscopy as well as elemental analysis were used to characterize the tetrazoles. The Cu/Ni/rGO nanocomposite showed the superior catalytic activity for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles within a short reaction time and high yields. Furthermore, this protocol eliminates the need to handle HN3. 相似文献
89.
Tungstate ions were successfully loaded onto triazine‐based ionic liquid‐functionalized magnetic nanoparticles through an anion exchange process. The use of triazine core for creating ionic liquid led to the immobilization of high amounts of WO42?. The resulting catalyst showed high activity and selectivity in the oxidation of sulfides to sulfoxides with H2O2 as a green oxidant at room temperature. In addition, due to the presence of ammonium groups in the catalyst structure, water dispersibility of the catalyst was increased. More important, the catalyst was magnetically recovered and reused for up to six runs without any marked decrease of activity and selectivity. Finally, easy gram‐scale oxidation of methylphenyl sulfide as well as fast separation of catalyst and product makes the protocol economical and industrially applicable. 相似文献
90.