全文获取类型
| 收费全文 | 413篇 |
| 免费 | 13篇 |
| 国内免费 | 43篇 |
专业分类
| 化学 | 120篇 |
| 晶体学 | 1篇 |
| 力学 | 22篇 |
| 综合类 | 4篇 |
| 数学 | 244篇 |
| 物理学 | 78篇 |
出版年
| 2023年 | 6篇 |
| 2022年 | 12篇 |
| 2021年 | 4篇 |
| 2020年 | 15篇 |
| 2019年 | 14篇 |
| 2018年 | 12篇 |
| 2017年 | 14篇 |
| 2016年 | 7篇 |
| 2015年 | 8篇 |
| 2014年 | 19篇 |
| 2013年 | 26篇 |
| 2012年 | 15篇 |
| 2011年 | 43篇 |
| 2010年 | 35篇 |
| 2009年 | 42篇 |
| 2008年 | 30篇 |
| 2007年 | 28篇 |
| 2006年 | 19篇 |
| 2005年 | 16篇 |
| 2004年 | 23篇 |
| 2003年 | 19篇 |
| 2002年 | 12篇 |
| 2001年 | 4篇 |
| 2000年 | 5篇 |
| 1999年 | 6篇 |
| 1998年 | 9篇 |
| 1997年 | 7篇 |
| 1996年 | 4篇 |
| 1995年 | 2篇 |
| 1994年 | 2篇 |
| 1993年 | 3篇 |
| 1991年 | 3篇 |
| 1990年 | 2篇 |
| 1984年 | 3篇 |
排序方式： 共有469条查询结果，搜索用时 0 毫秒
461.
462.
Yuri G Zarhin 《Journal of Number Theory》2004,108(1):44-59
Recently, Levin proved the Tate conjecture for ordinary cubic fourfolds over finite fields. In this paper, we prove the Tate conjecture for self-products of ordinary cubic fourfolds. Our proof is based on properties of so-called polynomials of K3-type introduced by the author about 12 years ago. 相似文献
463.
讨论一类具有二虚平行不变直线的三次系统，求出了奇点O(0,0)的焦点量, 证明了δlmn=0 时系统在O外围至多有一个极限环. 利用分支理论给出了分界线环和半稳 定环分支曲线的分支图，进一步说明了系统至多有二个极限环. 相似文献
464.
Experiments were performed to study surface pressure on a cubic building underlying conical vortices, which are known to cause severe structural damage and failure. The focus is on the effects of turbulence in the incident flow. Three turbulent boundary layers were created in a boundary layer wind tunnel. A wall-mounted cube, i.e. a cube situated on the horizontal ground floor surface of the wind-tunnel test section, was used as an experimental model. The cube was subjected to the incidence flow at 40°. Steady and unsteady pressure measurements were performed on the cube surface. The analysis suggests that conical vortices developed above the top surface of the wall-mounted cube. A larger mean suction was observed on the top cube surface in the less turbulent boundary layer. With an increase in turbulence in the incoming flow, the strong suction zones decreased in size. The fluctuating pressure coefficient profiles retained their shape when the turbulence in the upstream flow of the cube increased. The fluctuating pressure coefficient was observed to be larger in more turbulent flows. The pressure fluctuations were larger on the cube surface underlying outer boundaries of the conical vortex. The fluctuating pressure coefficient under the conical vortex was three to four times larger than in the weak suction zone on the central area of the top cube surface. Close to the leading cube corner, the pressure spectra were dominated by a single low frequency peak. As the conical vortex developed, this primary peak weakened and a secondary peak emerged at a higher reduced frequency. There is a general trend of shifting the pressure spectra towards higher reduced frequencies when the turbulence in the undisturbed incident flow increases. 相似文献
465.
《Physics letters. A》2020,384(25):126625
We propose a mechanism for realising a unidirectional flow of discrete solitons in optical waveguide arrays. Modulating the nonlinear interaction strength in each waveguide according to a double reflectionless potential well with slight difference in the depths of its two wells, we achieve a unidirectional flow of the soliton propagation. We verify clearly, through the transport coefficients as in terms of the speed of the incident soliton, that an incident soliton velocity window of finite width exists where unidirectional flow can be realised. We discuss the physics underlying this behaviour on the basis of energy exchange between the soliton's kinetic and interaction energies. 相似文献
466.
We consider a quasilinear system of partial differential equations (PDEs) governing the one-dimensional unsteady planar and cylindrically symmetric motion of an electrically conducting van der Waals fluid permeated with a transverse magnetic field. An asymptotic method is used to derive an evolution equation that governs the wave amplitude in the far field. Our main objective is to study the evolution equation, and to investigate as to how the presence of magnetic field and geometrical spreading (in cylindrical case) along with the cubic nonlinearity, inherently present in the system, influence the wave structure that finally develops. 相似文献
467.
Monotonicity-preserving interpolants are used in several applications as engineering or computer aided design. In last years some new techniques have been developed. In particular, in Aràndiga (2013) some new methods to design monotone cubic Hermite interpolants for uniform and non-uniform grids are presented and analyzed. They consist on calculating the derivative values introducing the weighted harmonic mean and a non-linear variation. With these changes, the methods obtained are third-order accurate, except in extreme situations. In this paper, a new general mean is used and a third-order interpolant for all cases is gained. We perform several experiments comparing the known techniques as the method proposed by Fritsch and Butland using the Brodlie’s function, PCHIP program of Matlab (Moler, 2004; Wolberg and Alfy, 2002) with the new algorithm. 相似文献
468.
In this paper, we establish a complete classification of locally strongly convex isotropic centroaffine hypersurfaces in the -dimensional affine space . 相似文献
469.
Huaifang Zhang Yanbo Li Chuanqi Cheng Jin Zhou Dr. Pengfei Yin Haoming Wu Prof. Zhiqin Liang Prof. Jiangwei Zhang Qinbai Yun Prof. An-Liang Wang Prof. Lijie Zhu Prof. Bin Zhang Prof. Wenbin Cao Prof. Xiangmin Meng Prof. Jing Xia Prof. Yifu Yu Prof. Qipeng Lu 《Angewandte Chemie (International ed. in English)》2023,62(4):e202213351
The direct electrochemical nitric oxide reduction reaction (NORR) is an attractive technique for converting NO into NH3 with low power consumption under ambient conditions. Optimizing the electronic structure of the active sites can greatly improve the performance of electrocatalysts. Herein, we prepare body-centered cubic RuGa intermetallic compounds (i.e., bcc RuGa IMCs) via a substrate-anchored thermal annealing method. The electrocatalyst exhibits a remarkable NH4+ yield rate of 320.6 μmol h−1 mg−1Ru with the corresponding Faradaic efficiency of 72.3 % at very low potential of −0.2 V vs. reversible hydrogen electrode (RHE) in neutral media. Theoretical calculations reveal that the electron-rich Ru atoms in bcc RuGa IMCs facilitate the adsorption and activation of *HNO intermediate. Hence, the energy barrier of the potential-determining step in NORR could be greatly reduced. 相似文献