全文获取类型
收费全文 | 11629篇 |
免费 | 1527篇 |
国内免费 | 698篇 |
专业分类
化学 | 3957篇 |
晶体学 | 101篇 |
力学 | 3647篇 |
综合类 | 73篇 |
数学 | 1098篇 |
物理学 | 4978篇 |
出版年
2024年 | 8篇 |
2023年 | 109篇 |
2022年 | 176篇 |
2021年 | 224篇 |
2020年 | 295篇 |
2019年 | 272篇 |
2018年 | 252篇 |
2017年 | 350篇 |
2016年 | 437篇 |
2015年 | 434篇 |
2014年 | 477篇 |
2013年 | 1300篇 |
2012年 | 654篇 |
2011年 | 767篇 |
2010年 | 573篇 |
2009年 | 687篇 |
2008年 | 638篇 |
2007年 | 658篇 |
2006年 | 573篇 |
2005年 | 620篇 |
2004年 | 506篇 |
2003年 | 454篇 |
2002年 | 403篇 |
2001年 | 341篇 |
2000年 | 252篇 |
1999年 | 212篇 |
1998年 | 236篇 |
1997年 | 215篇 |
1996年 | 166篇 |
1995年 | 232篇 |
1994年 | 175篇 |
1993年 | 181篇 |
1992年 | 133篇 |
1991年 | 132篇 |
1990年 | 88篇 |
1989年 | 85篇 |
1988年 | 108篇 |
1987年 | 74篇 |
1986年 | 77篇 |
1985年 | 55篇 |
1984年 | 46篇 |
1983年 | 19篇 |
1982年 | 52篇 |
1981年 | 29篇 |
1980年 | 10篇 |
1979年 | 24篇 |
1978年 | 11篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
采用自主设计搭建的雾化辅助化学气相沉积系统设备,开展了Ga2O3薄膜制备及其特性研究工作。通过X射线衍射研究了沉积温度、系统沉积压差对Ga2O3薄膜结晶质量的影响。结果表明,Ga2O3在425~650 ℃温度区间存在物相转换关系。随着沉积温度从425 ℃升高至650 ℃,薄膜结晶分别由非晶态、纯α-Ga2O3结晶状态向α-Ga2O3、β-Ga2O3两相混合结晶状态改变。通过原子力显微镜表征探究了生长温度对Ga2O3薄膜表面形貌的影响,从475 ℃升高至650 ℃时,薄膜表面粗糙度由26.8 nm下降至24.8 nm。同时,高分辨X射线衍射仪测试表明475 ℃、5 Pa压差条件下的α-Ga2O3薄膜样品半峰全宽仅为190.8″,为高度结晶态的单晶α-Ga2O3薄膜材料。 相似文献
2.
Evolution of electrical conductivity and semiconductor to metal transition of iron oxides at extreme conditions 下载免费PDF全文
Yukai Zhuang 《中国物理 B》2022,31(8):89101-089101
Iron oxides are widely found as ores in Earth's crust and are also important constituents of its interiors. Their polymorphism, composition changes, and electronic structures play essential roles in controlling the structure and geodynamic properties of the solid Earth. While all-natural occurring iron oxides are semiconductors or insulators at ambient pressure, they start to metalize under pressure. Here in this work, we review the electronic conductivity and metallization of iron oxides under high-pressure conditions found in Earth's lower mantle. We summarize that the metallization of iron oxides is generally controlled by the pressure-induced bandgap closure near the Fermi level. After metallization, they possess much higher electrical and thermal conductivity, which will facilitate the thermal convection, support a more stable and thicker D$\prime\prime$ layer, and formulate Earth's magnetic field, all of which will constrain the large-scale dynamos of the mantle and core. 相似文献
3.
4.
A cost‐effective curvature calculation approach for interfacial flows on unstructured meshes 下载免费PDF全文
We present a simple and cost‐effective curvature calculation approach for simulations of interfacial flows on structured and unstructured grids. The interface is defined using volume fractions, and the interface curvature is obtained as a function of the gradients of volume fractions. The gradient computation is based on a recently proposed gradient recovery method that mimicks the least squares approach without the need to solve a system of equations and is quite easy to implement on arbitrary polygonal meshes. The resulting interface curvature is used in a continuum surface force formulation within the framework of a well‐balanced finite‐volume algorithm to simulate multiphase flows dominated by surface tension. We show that the proposed curvature calculation is at least as accurate as some of the existing approaches on unstructured meshes while being straightforward to implement on any mesh topology. Numerical investigations also show that spurious currents in stationary problems that are dependent on the curvature calculation methodology are also acceptably low using the proposed approach. Studies on capillary waves and rising bubbles in viscous flows lend credence to the ability of the proposed method as an inexpensive, robust, and reasonably accurate approach for curvature calculation and numerical simulation of multiphase flows. 相似文献
5.
High pressure can effectively control the phase transition of MoTe2 in experiment, but the mechanism is still unclear. In this work, we show by first-principles calculations that the phase transition is suppressed and phase becomes more stable under high pressure, which originates from the pressure-induced change of the interlayer band occupancies near the Fermi energy. Specifically, the interlayer states of phase tend to be fully occupied under high pressure, while they keep partially occupied for the phase. The increase of the band occupancies makes the phase more favorable in energy and prevents the structure changing from to phase. Moreover, we also analyze the superconductivity under high pressure based on BCS theory by calculating the density of states and phonon spectra. Our results may shed some light on understanding the relationship between the interlayer band occupancy and crystal stability of MoTe2 under high pressures. 相似文献
6.
Eduard Feireisl 《偏微分方程通讯》2019,44(3):271-278
We show the weak–strong uniqueness property for the compressible Navier–Stokes system with general non-monotone pressure law. A weak solution coincides with the strong solution emanating from the same initial data as long as the latter solution exists. 相似文献
7.
Kazuo Yamazaki 《随机分析与应用》2019,37(3):412-444
The magnetohydrodynamics system consists of the Navier-Stokes equations from fluid mechanics, coupled with the Maxwell’s equations from electromagnetism through multiples of non-linear terms involving derivatives. Following the approach of [1], we prove the existence of a unique invariant measure in case the forcing terms consist of the cylindrical Wiener processes with only low modes. Its proof requires taking advantage of the structure of the non-linear terms carefully and is extended to various other related models such as the magnetohydrodynamics-Boussinesq system from fluid mechanics in atmosphere and oceans, as well as the magneto-micropolar fluid system from the theory of microfluids. 相似文献
8.
Two-dimensional van der Waals magnetic materials are intriguing for applications in the future spintronics devices, so it is crucial to explore strategy to control the magnetic properties. Here, we carried out first-principles calculations and Monte Carlo simulations to investigate the effect of biaxial strain and hydrostatic pressure on the magnetic properties of the bilayer CrI3. We found that the magnetic anisotropy, intralayer and interlayer exchange interactions, and Curie temperature can be tuned by biaxial strain and hydrostatic pressure. Large compressive biaxial strain may induce a ferromagneticto-antiferromagnetic transition of both CrI3 layers. The hydrostatic pressure could enhance the intralayer exchange interaction significantly and hence largely boost the Curie temperature. The effect of the biaxial strain and hydrostatic pressure revealed in the bilayer CrI3 may be generalized to other two-dimensional magnetic materials. 相似文献
9.
Wenjing Li Mingchun Lu Eva Zurek Xuedi Xu Lulu Chen Miao Zhang Lili Gao Xin Zhong Jia Li Xiaoming Zhou Wenyan Liu 《Physics letters. A》2019,383(10):1047-1051
Silicon (Si) is one of the most essential elements, as it is indispensable for modern electronic technology. The standard Si structure at ambient conditions is the cubic diamond structure, and it has an indirect band gap, which prevents it from being considered as a next-generation platform for semiconductor technologies. Therefore, the search for new allotropes of silicon has attracted great attention. Herein, first principles swarm-intelligence structure searches coupled with density-functional theory were performed to explore the stable high-pressure phases of silicon-rich lithium containing compounds, LiSix (). The LiSi4 stoichiometry was predicted to be stable, and it was found to assume one of the following space groups, P4/mnc, Cmmm, and C2/m within the pressure range of 0 to 50 GPa. By removing the Li atoms from these compounds, three silicon allotropes were obtained that were metastable at ambient pressures. Our work illustrates how novel silicon allotropes can be predicted using the CALYPSO method. 相似文献
10.
为提高计算效率,提出有限体积法离散下的虚拟区域颗粒两相流动直接模拟方法.在控制方程中加入相应的虚拟区域源项,保证了颗粒内部的刚体运动特性.该源项中含有颗粒信息部分及流体信息部分.在每次迭代后,对源项中的流体信息部分进行更新,从而更好地保证颗粒内速度的刚体分布.计算静止颗粒圆柱绕流及单个颗粒的沉降过程,验证了算法的准确性. 相似文献