全文获取类型
收费全文 | 58634篇 |
免费 | 10142篇 |
国内免费 | 6442篇 |
专业分类
化学 | 41457篇 |
晶体学 | 689篇 |
力学 | 3492篇 |
综合类 | 373篇 |
数学 | 6937篇 |
物理学 | 22270篇 |
出版年
2024年 | 54篇 |
2023年 | 1244篇 |
2022年 | 1420篇 |
2021年 | 2057篇 |
2020年 | 2552篇 |
2019年 | 2404篇 |
2018年 | 2054篇 |
2017年 | 1968篇 |
2016年 | 2949篇 |
2015年 | 2878篇 |
2014年 | 3461篇 |
2013年 | 4438篇 |
2012年 | 5524篇 |
2011年 | 5581篇 |
2010年 | 3860篇 |
2009年 | 3634篇 |
2008年 | 3881篇 |
2007年 | 3427篇 |
2006年 | 3103篇 |
2005年 | 2631篇 |
2004年 | 2008篇 |
2003年 | 1574篇 |
2002年 | 1338篇 |
2001年 | 1108篇 |
2000年 | 996篇 |
1999年 | 1192篇 |
1998年 | 972篇 |
1997年 | 911篇 |
1996年 | 908篇 |
1995年 | 841篇 |
1994年 | 717篇 |
1993年 | 599篇 |
1992年 | 514篇 |
1991年 | 442篇 |
1990年 | 391篇 |
1989年 | 284篇 |
1988年 | 202篇 |
1987年 | 186篇 |
1986年 | 193篇 |
1985年 | 172篇 |
1984年 | 99篇 |
1983年 | 107篇 |
1982年 | 59篇 |
1981年 | 43篇 |
1980年 | 35篇 |
1979年 | 20篇 |
1977年 | 19篇 |
1976年 | 22篇 |
1975年 | 21篇 |
1972年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Rational Design of Two-Dimensional Magnetic Chromium Borides Based on First-Principles Calculation 下载免费PDF全文
Two-dimensional(2D) magnetic materials have been experimentally recognized recently,however,the Curie temperatures(TC) of known 2D systems are quite low.Generally,magnetic systems can be seen as constituent magnetic elements providing spins and the non-magnetic elements providing frameworks to host the magnetic elements.Short bond lengths between the magnetic and non-magnetic elements would be beneficial for strong magnetic interactions and thus high TC.Based on this,we propose to combine the magnetic element Cr and the non-magnetic element boron to design novel 2D magnetic systems.Using our self-developed software package IM2 ODE,we design a series of chromium-boride based 2D magnetic materials.Nine stable magnetic systems are identified.Among them,we find that CrB4-Ⅰ,CrB4-Ⅱ and CrBs-Ⅰ with common structural units [CrB8] are ferromagnetic metals with estimated TC of 270 K,120 K and 110 K,respectively.On the other hand,five CrB3 phases with structural units [Cr2B12] are antiferromagnetic metals.Additionally,we also find one antiferromagnetic semiconductor CrB2-Ⅰ.Our work may open new directions for identifying 2D magnetic systems with high TC. 相似文献
52.
53.
54.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
55.
为探究加强型Bi-2212超导股线的力学性能以及不锈钢包带对超导股线力学性能的影响,运用Ansys软件建立加强型Bi-2212超导股线的三维模型,采用有限元分析方法,对其机械结构进行仿真,模拟高温高压热处理后轴向受拉形变量和应力应变分布情况。仿真结果显示,在同样施加100 N拉力的情况下,与超导原线(Bi-2212超导线)相比,密绕Ni80Cr20包带后的加强型Bi-2212超导股线轴向受拉形变程度减小,约10%;应力应变均降低,约30%。采用Ni80Cr20作为外包带制成的加强型Bi-2212超导股线力学性能显著,是未来超导线发展方向之一。 相似文献
56.
Cycloparaphenylene (CPP) shows modulated photophysical and electronic properties due to its strained structure and radially oriented π-electron system. Incorporation of CPP into metal-organic frameworks (MOFs) could transfer its extensive properties in solution to porous solids. Moreover, with the unique arrangement of the macrocycles and their interactions with the framework, emerging characteristics are anticipated. As an example of “robust dynamics”, we synthesized the first MOF structure (FDM-1001) with CPP precisely anchored to the ordered framework by employing a [8]CPP-containing linear dicarboxylate linker. Metric relationship between the dynamic macrocycles and the robust backbone creates ideal π-π interactions between them, which leads to an essentially directional arrangement of [8]CPP in the three-dimensional space. Furthermore, the MOF with [8]CPP could be successfully oxidized to generate an infinite array of radicals that show enhanced air stability compared to its molecular analogue. 相似文献
57.
Crystallography Reports - A di-nuclear uranyl complex with the formula of [(UO2)2(L)4(H2O)2]?4H2O (1) (HL = quinoline-6-carboxylic acid) was synthesized hydrothermally and characterized by... 相似文献
58.
Nonlinear Dynamics - This paper mainly investigates the dynamics of the non-resonant and near-resonant Hopf–Hopf bifurcations caused by the interaction of the lateral and yaw motion in a... 相似文献
59.
Nonlinear Dynamics - Vibro-impact drilling has shown huge potential of delivering better rate of penetration, improved tools lifespan and better borehole stability. However, being resonantly... 相似文献
60.
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the... 相似文献