全文获取类型
收费全文 | 1196篇 |
免费 | 53篇 |
国内免费 | 3篇 |
专业分类
化学 | 741篇 |
晶体学 | 25篇 |
力学 | 49篇 |
数学 | 212篇 |
物理学 | 225篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 24篇 |
2021年 | 42篇 |
2020年 | 39篇 |
2019年 | 34篇 |
2018年 | 29篇 |
2017年 | 49篇 |
2016年 | 53篇 |
2015年 | 53篇 |
2014年 | 46篇 |
2013年 | 115篇 |
2012年 | 101篇 |
2011年 | 103篇 |
2010年 | 77篇 |
2009年 | 64篇 |
2008年 | 73篇 |
2007年 | 64篇 |
2006年 | 40篇 |
2005年 | 43篇 |
2004年 | 51篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1972年 | 2篇 |
1907年 | 1篇 |
排序方式: 共有1252条查询结果,搜索用时 15 毫秒
251.
An efficient edge based data structure has been developed in order to implement an unstructured vertex based finite volume algorithm for the Reynolds-averaged Navier–Stokes equations on hybrid meshes. In the present approach, the data structure is tailored to meet the requirements of the vertex based algorithm by considering data access patterns and cache efficiency. The required data are packed and allocated in a way that they are close to each other in the physical memory. Therefore, the proposed data structure increases cache performance and improves computation time. As a result, the explicit flow solver indicates a significant speed up compared to other open-source solvers in terms of CPU time. A fully implicit version has also been implemented based on the PETSc library in order to improve the robustness of the algorithm. The resulting algebraic equations due to the compressible Navier–Stokes and the one equation Spalart–Allmaras turbulence equations are solved in a monolithic manner using the restricted additive Schwarz preconditioner combined with the FGMRES Krylov subspace algorithm. In order to further improve the computational accuracy, the multiscale metric based anisotropic mesh refinement library PyAMG is used for mesh adaptation. The numerical algorithm is validated for the classical benchmark problems such as the transonic turbulent flow around a supercritical RAE2822 airfoil and DLR-F6 wing-body-nacelle-pylon configuration. The efficiency of the data structure is demonstrated by achieving up to an order of magnitude speed up in CPU times. 相似文献
252.
Journal of Inclusion Phenomena and Macrocyclic Chemistry - Newly phthalocyanine derivative which carries 2,6-dimethoxyphenoxy bioactive groups as tetrakis from non-peripheral positions of the... 相似文献
253.
Yazid Gouari Zoubir Dahmani Mehmet Zeki Sarikaya 《Mathematical Methods in the Applied Sciences》2020,43(11):6938-6949
In this paper, using Riemann–Liouville integral and Caputo derivative, we study a nonlinear singular integro-differential equation of Lane–Emden type with nonlocal multi-point integral conditions. We prove the existence and uniqueness of solutions by application of Banach contraction principle. Also, we prove an existence result using Schaefer fixed point theorem. Then, we present some examples to show the applicability of the main results. 相似文献
254.
Abdul Q. Ramle Asli Karakas Abdul K. M. Arof Mustafa Karakaya Mehmet Taser Aysun Gozutok Chee Chin Fei Nurhidayatullaili M. Julkapli Wan J. Basirun 《Journal of heterocyclic chemistry》2020,57(10):3566-3573
Two new macrocyclic dibenzotetraaza[14]annulene (DBTAA) compounds with indolenine ( 5 ) and pyridoindolenine ( 6 ) moieties were synthesized and characterized by spectroscopy. Both DBTAAs exhibit strong UV-Vis absorption properties in the Soret band region. The theoretical second-order nonlinear optical property, electric dipole moment (μ), dispersion-free dipole polarizability (α) and first hyper-polarizability values were calculated by density functional theory and time dependent density functional theory. The ab-initio quantum mechanical calculation by time-dependent Hartree-Fock method was utilized to investigate the dynamic dipole polarizabilities, dynamic second-order, static, and dynamic third-order (γ) hyper-polarizabilities of the DBTAAs. The configuration interaction technique of all doubly occupied molecular orbitals possesses theoretically defined single-photon absorption (OPA) specifications for the examined structures. The computed maximum OPA wavelengths on both macrocyclic compounds coincide with the preceding measurement outcomes. 相似文献
255.
Journal of Visualization - 相似文献
256.
257.
258.
Stefaan Cottenier Veerle Vanhoof Doru Torumba Valerio Bellini Mehmet Çakmak Michel Rots 《Hyperfine Interactions》2004,158(1-4):9-18
For some years already, ab initio calculations based on Density Functional Theory (DFT) belong to the toolbox of the field of hyperfine interaction studies.
In this paper, the standard ab initio approach is schematically sketched. New features, methods and possibilities that broke through during the past few years
are listed, and their relation to the standard approach is explained. All this is illustrated by some highlights of recent
ab initio work done by the Nuclear Condensed Matter Group at the K.U.Leuven. 相似文献
259.
260.
A novel implicit cell‐vertex finite volume method is described for the solution of the Navier–Stokes equations at high Reynolds numbers. The key idea is the elimination of the pressure term from the momentum equation by multiplying the momentum equation with the unit normal vector to a control volume boundary and integrating thereafter around this boundary. The resulting equations are expressed solely in terms of the velocity components. Thus any difficulties with pressure or vorticity boundary conditions are circumvented and the number of primary variables that need to be determined equals the number of space dimensions. The method is applied to both the steady and unsteady two‐dimensional lid‐driven cavity problem at Reynolds numbers up to 10000. Results are compared with those in the literature and show excellent agreement. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献