全文获取类型
收费全文 | 31495篇 |
免费 | 3872篇 |
国内免费 | 3891篇 |
专业分类
化学 | 9588篇 |
晶体学 | 197篇 |
力学 | 3970篇 |
综合类 | 332篇 |
数学 | 12488篇 |
物理学 | 12683篇 |
出版年
2024年 | 66篇 |
2023年 | 328篇 |
2022年 | 500篇 |
2021年 | 685篇 |
2020年 | 951篇 |
2019年 | 927篇 |
2018年 | 909篇 |
2017年 | 1042篇 |
2016年 | 1253篇 |
2015年 | 1077篇 |
2014年 | 1638篇 |
2013年 | 2665篇 |
2012年 | 1703篇 |
2011年 | 2066篇 |
2010年 | 1621篇 |
2009年 | 2070篇 |
2008年 | 2170篇 |
2007年 | 2240篇 |
2006年 | 1880篇 |
2005年 | 1632篇 |
2004年 | 1333篇 |
2003年 | 1344篇 |
2002年 | 1291篇 |
2001年 | 941篇 |
2000年 | 926篇 |
1999年 | 812篇 |
1998年 | 740篇 |
1997年 | 604篇 |
1996年 | 432篇 |
1995年 | 389篇 |
1994年 | 316篇 |
1993年 | 291篇 |
1992年 | 265篇 |
1991年 | 247篇 |
1990年 | 234篇 |
1989年 | 199篇 |
1988年 | 171篇 |
1987年 | 160篇 |
1986年 | 121篇 |
1985年 | 142篇 |
1984年 | 129篇 |
1983年 | 54篇 |
1982年 | 95篇 |
1981年 | 85篇 |
1980年 | 70篇 |
1979年 | 85篇 |
1978年 | 72篇 |
1977年 | 69篇 |
1976年 | 64篇 |
1973年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Mendeleev Communications》2022,32(4):467-470
Isomeric forms of indoline spiropyrans show unusual behavior compared with similar compounds, according to experimental data. DFT modeling for gas phase was made to consider the simplest case without environmental effects, which revealed the intramolecular reasons for occurrence of ring opening reaction depending on the particular structure of the compound. The questions of charge redistributions, the changes of geometry and chemical bonds in the structures are also discussed. 相似文献
2.
本文提出了一种新的能够计及尺度效应的微纳米蜂窝等效模量的计算方法。将一种单参数应变梯度理论引入到本构方程当中,并基于能量等效原理推导了蜂窝面内等效模量地计算公式。算例分析表明,本文方法能够有效地计及尺度效应对蜂窝等效模量的影响。尺度效应与胞壁厚度和长度的值都有关,当胞壁厚度较小时,尺度效应显著,本文方法预测的模量会明显高于传统方法;而当胞壁厚度较大时,尺度效应变得微弱乃至可以忽略不计。但如果胞壁的长度/厚度比很大,则面内等效模量会趋近于0,此时是否考虑尺度效应意义不大。 相似文献
3.
4.
5.
从头发的结构和组成出发分析头发形状和颜色改变的可能性,剖析烫发、染发的化学原理,阐释先烫发后染发的本质原因,从化学视角辨证地看待烫发、染发的利弊。 相似文献
6.
Chemical bonding in representative astrophysically relevant neutral,cation, and anion HCnH chains 下载免费PDF全文
Ioan Baldea 《中国物理 B》2022,31(12):123101-123101
Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths. Building on our recent work, in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis. Presently reported results include atomic charges, natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC2k/2k+1H chain family. They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes, e.g., electron removal from or electron attachment to a neutral chain. Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC2k/2k+1H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study. 相似文献
7.
Giang Truong Nguyen Prof. Dr. Liviu Ungur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200227
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs. 相似文献
8.
Liquid-liquid-solid systems are becoming increasingly common in everyday life with many possible applications. Here, we focus on a special case of such liquid-liquid-solid systems, namely, capillary suspensions. These capillary suspensions originate from particles that form a network based on capillary forces and are typically composed of solids in a bulk liquid with an added secondary liquid. The structure of particle networks based on capillary bridges possesses unique properties compared with networks formed via other attractive interactions where these differences are inherently related to the properties of the capillary bridges, such as bridge breaking and coalescence between adjacent bridges. Thus, to tailor the mechanical properties of capillary suspensions to specific requirements, it is important to understand the influences on different length scales ranging from the dynamics of the bridges with varying external stimuli to the often heterogeneous network structure. 相似文献
9.
10.