全文获取类型
收费全文 | 421篇 |
免费 | 13篇 |
国内免费 | 8篇 |
专业分类
化学 | 295篇 |
力学 | 23篇 |
数学 | 53篇 |
物理学 | 71篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 24篇 |
2020年 | 19篇 |
2019年 | 9篇 |
2018年 | 21篇 |
2017年 | 12篇 |
2016年 | 37篇 |
2015年 | 18篇 |
2014年 | 33篇 |
2013年 | 69篇 |
2012年 | 32篇 |
2011年 | 30篇 |
2010年 | 26篇 |
2009年 | 28篇 |
2008年 | 21篇 |
2007年 | 25篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 1篇 |
1985年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有442条查询结果,搜索用时 15 毫秒
61.
H. Hossienkhani V. Fayaz S. A. A. Terohid N. Azimi Z. Zarei M. Ganji 《Theoretical and Mathematical Physics》2018,194(3):415-438
We study a dilaton scalar field coupled to ghost dark energy in an anisotropic universe. The evolution of dark energy, which dominates the universe, can be completely described by a single dilaton scalar field. This connection allows reconstructing the kinetic energy and also the dynamics of the dilaton scalar field according to the evolution of the energy density. Using the latest observational data, we obtain bounds on the ghost dark energy models and also on generalized dark matter and dark energy. For this, we investigate how the expansion history H(z) is determined by observational quantities. We calculate the evolution of density perturbations in the linear regime for both ghost and generalized ghost dark energy and compare the results with ΛCDM models. We discuss the justification of the generalized second law of thermodynamics in a Bianchi type-I universe. The obtained model is stable for large time intervals but is unstable at small times. 相似文献
62.
Z.Z. Ganji D.D. Ganji Ammar D. Ganji M. Rostamian 《Numerical Methods for Partial Differential Equations》2010,26(1):117-124
In this letter, we implement a relatively new analytical technique, the homotopy perturbation method (HPM), for solving linear partial differential equations of fractional order arising in fluid mechanics. The fractional derivatives are described in Caputo derivatives. This method can be used as an alternative to obtain analytic and approximate solutions of different types of fractional differential equations applied in engineering mathematics. The corresponding solutions of the integer order equations are found to follow as special cases of those of fractional order equations. Some numerical examples are presented to illustrate the efficiency and reliability of HPM. He's HPM, which does not need small parameter is implemented for solving the differential equations. In this method, a homotopy is introduced to be constructed for the equation. The initial approximations can be freely chosen with possible unknown constants that can be determined by imposing the boundary and initial conditions. It is predicted that HPM can be found widely applicable in engineering. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 相似文献
63.
D.D. Ganji M. Gorji M. Alipanah E. Farnad 《Numerical Methods for Partial Differential Equations》2010,26(6):1463-1475
As thermal conductivity plays an important role on fin efficiency, we tried to solve heat transfer equation with thermal conductivity as a function of temperature. In this research, some new analytical methods called homotopy perturbation method, variational iteration method, and Adomian decomposition method are introduced to be applied to solve the nonlinear heat transfer equations, and also the comparison of the applied methods (together) is shown graphically. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 相似文献
64.
Davood Momeni Muhammad Raza Mohammad Reza Setare Ratbay Myrzakulov 《International Journal of Theoretical Physics》2013,52(8):2773-2783
The holographic model for a two-dimensional superconductor has been investigated by considering the three-dimensional gravity in the bulk. To find the critical temperature, we used the Sturm–Liouville variational method. Where as the same method is applied for calculating the condensation of the dual operators on the boundary. We included the back reactions on the metric by a combination of the perturbation method of the fields with respect to the small parameter and then applying the variational integrals on the resulting equations of the motion. The critical temperature has been successfully obtained on the backreaction effects, and we showed that it dropped with a rise in the backreaction of the fields, and it makes the condensation harder. We can use our analytical results to support the numerical data which was reported previously. 相似文献
65.
Alessandro Bravetti Davood Momeni Ratbay Myrzakulov Hernando Quevedo 《General Relativity and Gravitation》2013,45(8):1603-1617
We study the thermodynamics and geometrothermodynamics of different black hole configurations in more than four spacetime dimensions. We use the response functions to find the conditions under which second order phase transitions occur in higher-dimensional static Reissner–Nordström and stationary Kerr black holes. Our results indicate that the equilibrium manifold of all these black hole configurations is in general curved and that curvature singularities appear exactly at those places where second order phase transitions occur. 相似文献
66.
Karimi Kerdabadi Javad Haghanimanesh Maedeh Karimipour Arash Toghraie Davood Tlili Iskander 《Journal of Thermal Analysis and Calorimetry》2021,143(1):293-308
Journal of Thermal Analysis and Calorimetry - Hot-rolled strips are cooled on the run-out table to achieve the customer-required mechanical properties. Cooling reduces the oxidation, which can... 相似文献
67.
68.
Rostami Sara Toghraie Davood Esfahani Masihollah Ahmadi Hekmatifar Maboud Sina Nima 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1119-1128
Journal of Thermal Analysis and Calorimetry - In the current work, after generating experimental data points for different volume fraction of nanoparticles ( $$\phi$$ ) and different temperatures,... 相似文献
69.
Abdollah Rahimi Davood Habibi Amin Rostami Mohammad Ali Zolfigol Shadpour Mallakpour 《Tetrahedron letters》2018,59(4):383-387
The direct aerobic oxidation of 4-substituted urazoles using the laccase enzyme from Trametes versicolor in a phosphate buffer solution at ambient temperature, and subsequent cross-coupling with sodium benzenesulfinates was investigated to afford arylsulfonyl-1,2,4-triazolidine-3,5-dione derivatives in good to high yields. 相似文献
70.
A facile and one pot electrochemical synthesis of disubstituted hydroquinone generated from the electrochemical oxidation of 4-1-(4-(4-hydroxyphenyl)piperazin-1-yl)ethanone (1) in the presence of 4-hydroxy-6,7-dimethylcoumarin (3) has been reported. The results revealed that p-quinone imine derived from oxidation of (1) participate in Michael addition reactions with 3 and followed by a hydrolysis reaction attain to the highly symmetric and conjugated coumarin derivative. We derived a new product in good yield based on controlled potential electrochemical oxidation at carbon electrode in a divided cell. 相似文献