全文获取类型
收费全文 | 9972篇 |
免费 | 893篇 |
国内免费 | 1109篇 |
专业分类
化学 | 198篇 |
晶体学 | 3篇 |
力学 | 974篇 |
综合类 | 185篇 |
数学 | 9007篇 |
物理学 | 1607篇 |
出版年
2024年 | 20篇 |
2023年 | 127篇 |
2022年 | 103篇 |
2021年 | 154篇 |
2020年 | 221篇 |
2019年 | 309篇 |
2018年 | 317篇 |
2017年 | 310篇 |
2016年 | 329篇 |
2015年 | 251篇 |
2014年 | 474篇 |
2013年 | 809篇 |
2012年 | 407篇 |
2011年 | 584篇 |
2010年 | 558篇 |
2009年 | 760篇 |
2008年 | 707篇 |
2007年 | 729篇 |
2006年 | 615篇 |
2005年 | 562篇 |
2004年 | 469篇 |
2003年 | 479篇 |
2002年 | 443篇 |
2001年 | 308篇 |
2000年 | 326篇 |
1999年 | 332篇 |
1998年 | 274篇 |
1997年 | 250篇 |
1996年 | 176篇 |
1995年 | 78篇 |
1994年 | 80篇 |
1993年 | 53篇 |
1992年 | 47篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 45篇 |
1988年 | 25篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 19篇 |
1984年 | 29篇 |
1983年 | 15篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 47 毫秒
1.
Tomoyuki Nakatsuka 《Mathematische Nachrichten》2021,294(1):98-117
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution of the Navier–Stokes equation such that and uniformly in as . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described. 相似文献
2.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
3.
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
4.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
5.
6.
7.
8.
9.
Transformation hydrodynamics and the corresponding metamaterials have been proposed as a means to exclude the drag force acting on an object. Here, we report a strategy to deploy the hydrodynamic cloaks in a more practical manner by assembling different-shaped cloaking parts. Our strategy is to first model a square-shaped cloak and a carpet cloak and then combine them to conceal a more complex-shaped space in the three-dimensional hydrodynamic flow. With the derivation of transformation hydrodynamics, the coordinate transformations for each hydrodynamic cloaking are demonstrated with the calculated viscosity tensors. The pressure and velocity fields of the square, triangular (carpet), and exemplary three-dimensional house-shaped cloaks are numerically simulated, thus showing a cloaking effect and reduced drag. This study suggests an efficient way of cloaking complex architectures from fluid-dynamic forces. 相似文献
10.
Inner derivations and norm equality 总被引:3,自引:0,他引:3
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2002,130(2):471-476
We characterize when the norm of the sum of two bounded operators on a Hilbert space is equal to the sum of their norms.