全文获取类型
收费全文 | 503篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
化学 | 312篇 |
晶体学 | 7篇 |
力学 | 20篇 |
数学 | 55篇 |
物理学 | 130篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 32篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 39篇 |
2012年 | 35篇 |
2011年 | 37篇 |
2010年 | 44篇 |
2009年 | 34篇 |
2008年 | 46篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有524条查询结果,搜索用时 15 毫秒
1.
Synthesis and characterization of 4-{(E)-[(5-bromo-2-hydroxyphenyl)methylidene]amino}-N-carbamimidoylbenzene-1-sulfonamide(SA) and its composites with graphene(SA-GF) were performed. Compound SA and SA-GF were characterized by FTIR and 1H NMR. The GF dispersion in the composites was analyzed by means of scanning electron microscopy(SEM) for morphology. Thermal properties of SA and nanocomposites were investigated using differential thermal analysis(DTA) and thermogravimetric analysis(TGA). The optimum electrical conductivity of the new sulfonamide-based Schiff base was determined to be 1.78×10–5 S/cm at a frequency of 9923 Hz, an applied voltage of –19 V, a mass fraction of 9.38% for graphene loading using a central composite design in the response surface methodology. The significance of the selected parameters(frequency, voltage and GF amount) in the model was determined by the analysis of variance(ANOVA). The results showed that frequency and graphene loading represent important model terms and have considerable effects on the conductivity of SA. 相似文献
2.
Hussain Shafqat Öztop Hakan F. Mehmood Khalid Ali Mohamed E. 《Journal of Thermal Analysis and Calorimetry》2019,137(5):1735-1755
Journal of Thermal Analysis and Calorimetry - A computational analysis has been performed to study the impact of magnetic field on entropy generation due to mixed convective nanofluid flow with top... 相似文献
3.
Dağlı Özge Köse Dursun Ali İçten Okan Avcı Gülçin Alp Şahin Onur 《Journal of Thermal Analysis and Calorimetry》2019,136(4):1467-1480
Journal of Thermal Analysis and Calorimetry - The coumarilate (coum?) and 1,10-phenanthroline (phen) mixed ligand complexes of Co(II) (1), Ni(II) (2) Cu(II) (3) and Zn(II) (4) were... 相似文献
4.
We studied the synthesis and characterization of polymeric coordination complexes of Co(II) and Ni(II) ions with pyrazine-2,3-dicarboxylic acid and 1-vinylimidazole. The e lemental analysis, infrared spectroscopy, powder X-ray diffraction, magnetic susceptibility, thermal analysis and X-ray single crystal techniques were used in the characterization. The X-ray single crystal analysis suggests that the pyrazine-2,3-dicarboxylato ligand acts as a bridging ligand through the oxygen atoms of the carboxylate groups and the nitrogen atoms on the pyrazine ring. The 1-vinylimidazole ligand behaves as a monodentate ligand via the ring nitrogen atom. Further, the H2 adsorption studies were carried out at 75 K for various increasing pressures and the highest H2 adsorption performances for Co(II) and Ni(II) complexes were estimated as 2.66 and 2.99 wt% at 87 bar. The theoretical calculations using the crystal data were also performed to determine the voids in the structure of Co(II) complex. 相似文献
5.
6.
The multiple lump solutions method is employed for the purpose of obtaining multiple soliton solutions for the generalized Bogoyavlensky-Konopelchenko(BK) equation. The solutions obtained contain first-order, second-order, and third-order wave solutions. At the critical point,the second-order derivative and Hessian matrix for only one point is investigated, and the lump solution has one maximum value. He's semi-inverse variational principle(SIVP) is also used for the generalized BK equation. Three major cases are studied, based on two different ansatzes using the SIVP. The physical phenomena of the multiple soliton solutions thus obtained are then analyzed and demonstrated in the figures below, using a selection of suitable parameter values.This method should prove extremely useful for further studies of attractive physical phenomena in the fields of heat transfer, fluid dynamics, etc. 相似文献
7.
Selimefendigil Fatih Öztop Hakan F. Abu-Hamdeh Nidal 《Journal of Thermal Analysis and Calorimetry》2020,141(1):465-482
Journal of Thermal Analysis and Calorimetry - Forced convection of nanofluid in a vented cavity with elastic bottom wall is studied by using an inner conductive L-shaped object and magnetic field.... 相似文献
8.
Mustafa Özdemir Melek Erdoğdu Hakan Şimşek 《Advances in Applied Clifford Algebras》2014,24(1):179-192
In this paper, we examine eigenvalue problem of a rotation matrix in Minkowski 3 space by using split quaternions. We express the eigenvalues and the eigenvectors of a rotation matrix in term of the coefficients of the corresponding unit timelike split quaternion. We give the characterizations of eigenvalues (complex or real) of a rotation matrix in Minkowski 3 space according to only first component of the corresponding quaternion. Moreover, we find that the casual characters of rotation axis depend only on first component of the corresponding quaternion. Finally, we give the way to generate an orthogonal basis for ${\mathbb{E}^{3}_{1}}$ by using eigenvectors of a rotation matrix. 相似文献
9.
Bülbül Hakan Köysal Yavuz Doğan Onur Erman Dege Necmi Ağar Erbil 《Crystallography Reports》2019,64(3):403-406
Crystallography Reports - The title compound, C17H15NOS, crystallizes in the orthorhombic sp. gr. Pca21. Two molecules in the asymmetric unit have similar structure. Crystal structure contains weak... 相似文献
10.