全文获取类型
收费全文 | 10439篇 |
免费 | 507篇 |
国内免费 | 128篇 |
专业分类
化学 | 7407篇 |
晶体学 | 94篇 |
力学 | 514篇 |
综合类 | 3篇 |
数学 | 1278篇 |
物理学 | 1778篇 |
出版年
2024年 | 24篇 |
2023年 | 94篇 |
2022年 | 487篇 |
2021年 | 439篇 |
2020年 | 360篇 |
2019年 | 445篇 |
2018年 | 451篇 |
2017年 | 372篇 |
2016年 | 608篇 |
2015年 | 421篇 |
2014年 | 577篇 |
2013年 | 1071篇 |
2012年 | 816篇 |
2011年 | 775篇 |
2010年 | 558篇 |
2009年 | 451篇 |
2008年 | 500篇 |
2007年 | 440篇 |
2006年 | 313篇 |
2005年 | 320篇 |
2004年 | 194篇 |
2003年 | 192篇 |
2002年 | 162篇 |
2001年 | 84篇 |
2000年 | 55篇 |
1999年 | 64篇 |
1998年 | 42篇 |
1997年 | 52篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 39篇 |
1993年 | 20篇 |
1992年 | 37篇 |
1991年 | 33篇 |
1990年 | 30篇 |
1989年 | 36篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 37篇 |
1984年 | 35篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 18篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
In an effort to expand the capabilities of a validated simulation environment for fluid-structure interaction to turbulent flows, we present the simulation of a turbulent FSI benchmark case with large displacements in a simplified two-dimensional unsteady RANS setup. We find a fair agreement to experimental data that encourages further refinement of our approach and future three-dimensional simulations with eddy-resolving schemes. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
962.
We consider a continuous time principal-agent model where the principal/firm compensates an agent/manager who controls the output’s exposure to risk and its expected return. Both the firm and the manager have exponential utility and can trade in a frictionless market. When the firm observes the manager’s choice of effort and volatility, there is an optimal contract that induces the manager to not hedge. In a two factor specification of the model where an index and a bond are traded, the optimal contract is linear in output and the log return of the index. We also consider a manager who receives exogenous share or option compensation and illustrate how risk taking depends on the relative size of the systematic and firm-specific risk premia of the output and index. Whilst in most cases, options induce greater risk taking than shares, we find that there are also situations under which the hedging manager may take less risk than the non-hedging manager. 相似文献
963.
Moazzam Ali Martin D. Donakowski Christian Mayer Markus Winterer 《Journal of nanoparticle research》2012,14(3):689
The continuous functionalization of nanoparticles in the gas-phase directly after their generation, chemical vapor functionalization,
is studied with ZnO and 1-hexanol as a model system using two reactors in series. In the first reactor ZnO nanoparticles are
synthesized in the gas-phase from diethylzinc and oxygen at 1,073 K with grain sizes of 13 nm as determined by Rietveld refinement
of X-ray diffractograms. The second reactor, connected at the exit of the first reactor and kept at lower temperatures (573,
673, and 773 K), is used as a functionalization chamber. At the connection point of the two reactors, the vapor of 1-hexanol
is injected to react with the surface of ZnO nanoparticles in the gas phase. The process has been analyzed by quadrupole mass
spectrometry to obtain information about optimal conditions for functionalization. Dynamic light scattering data show that
the functionalized particles have substantially improved colloidal dispersibility with hydrodynamic diameters of 60 nm. Diffuse
reflectance fourier transform infrared spectra and 1H nuclear magnetic resonance spectra are consistent with 1-hexanol adsorbed at the particle surface acting as a functionalizing
agent. The agglomerate size is substantially reduced owing to chemical vapor functionalization. 相似文献
964.
965.
966.
Jeroen D.C. Codée Asghar Ali Herman S. Overkleeft Gijsbert A. van der Marel 《Comptes Rendus Chimie》2011,14(2-3):178-193
Protecting groups play a pivotal role in carbohydrate chemistry. This review describes a selection of protecting groups and protecting group strategies that have been introduced since the beginning of this century. 相似文献
967.
The multigrid method is one of the most efficient techniques for convergence acceleration of iterative methods. In this method, a grid coarsening algorithm is required. Here, an agglomeration scheme is introduced, which is applicable in both cell‐center and cell‐vertex 2 and 3D discretizations. A new implicit formulation is presented, which results in better computation efficiency, when added to the multigrid scheme. A few simple procedures are also proposed and applied to provide even higher convergence acceleration. The Euler equations are solved on an unstructured grid around standard transonic configurations to validate the algorithm and to assess its superiority to conventional explicit agglomeration schemes. The scheme is applied to 2 and 3D test cases using both cell‐center and cell‐vertex discretizations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
968.
969.
Hasrat Ali 《Tetrahedron letters》2009,50(3):337-4397
Covalently linked phthalocyanine-phthalocyanine (Pc-Pc) heterodimers and Pc-Pc triad phthalocyanines connected through phenyl-phenyl (C-C) linkages are prepared using phthalocyanine-boronate (Suzuki Pc-synthon) and palladium catalyst. 相似文献
970.