全文获取类型
收费全文 | 15069篇 |
免费 | 1365篇 |
国内免费 | 464篇 |
专业分类
化学 | 4740篇 |
晶体学 | 15篇 |
力学 | 847篇 |
综合类 | 65篇 |
数学 | 6556篇 |
物理学 | 4675篇 |
出版年
2024年 | 21篇 |
2023年 | 149篇 |
2022年 | 258篇 |
2021年 | 349篇 |
2020年 | 393篇 |
2019年 | 402篇 |
2018年 | 271篇 |
2017年 | 324篇 |
2016年 | 550篇 |
2015年 | 448篇 |
2014年 | 695篇 |
2013年 | 1138篇 |
2012年 | 663篇 |
2011年 | 716篇 |
2010年 | 636篇 |
2009年 | 878篇 |
2008年 | 1029篇 |
2007年 | 1027篇 |
2006年 | 849篇 |
2005年 | 624篇 |
2004年 | 526篇 |
2003年 | 575篇 |
2002年 | 575篇 |
2001年 | 440篇 |
2000年 | 461篇 |
1999年 | 386篇 |
1998年 | 371篇 |
1997年 | 253篇 |
1996年 | 211篇 |
1995年 | 174篇 |
1994年 | 175篇 |
1993年 | 153篇 |
1992年 | 146篇 |
1991年 | 93篇 |
1990年 | 87篇 |
1989年 | 89篇 |
1988年 | 103篇 |
1987年 | 72篇 |
1986年 | 66篇 |
1985年 | 103篇 |
1984年 | 80篇 |
1983年 | 24篇 |
1982年 | 50篇 |
1981年 | 47篇 |
1980年 | 48篇 |
1979年 | 38篇 |
1978年 | 33篇 |
1977年 | 34篇 |
1976年 | 30篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering 下载免费PDF全文
Electron-phonon coupling (EPC) in cuprate and iron-based superconducting systems, as revealed by Raman scat- tering, is briefly reviewed. We introduce how to extract the coupling information through phonon lineshape. Then we discuss the strength of EPC in different high-temperature superconductor (HTSC) systems and possible factors affecting the strength. A comparative study between Raman phonon theories and experiments allows us to gain insight into some crucial electronic properties, especially superconductivity. Finally, we summarize and compare EPC in the two existing HTSC systems, and discuss what role it may play in the HTSC. 相似文献
132.
133.
基于核学习的强大非线性映射能力,结合用于回归建模的线性偏最小二乘(PLS)算法,提出一种小波核偏最小二乘(WKPLS)回归方法. 该方法基于支持向量机使用的经典核函数技巧,将输入映射到高维非线性的特征空间,在特征空间中,构造线性的PLS回归模型. PLS方法利用输入与输出变量之间的协方差信息提取潜在特征,而可允许的小波核函数具有近似正交以及适用于信号局部分析的特性. 因此,结合它们优点的WKPLS方法显示了更好的非线性建模性能. 将WKPLS方法应用在非线性混沌动力系统建模上,并与基于高斯核的核偏最小二乘
关键词:
小波核
偏最小二乘回归
混沌系统
建模 相似文献
134.
A whole impulsive control scheme of nonlinear systems with time-varying delays, which is an extension for impulsive control of nonlinear systems without time delay, is presented in this paper. Utilizing the Lyapunov functions and the impulsive-type comparison principles, we establish a series of different conditions under which impulsively controlled nonlinear systems with time-varying delays are asymptotically stable. Then we estimate upper bounds of impulse interval and time-varying delays for asymptotically stable control. Finally a numerical example is given to illustrate the effectiveness of the method. 相似文献
135.
It is well-known that nano-systems can have properties which are distinctly different from macroscopic systems. In this study we point out the following specific behaviour: if the particle number is decreased so that the size of the system is in the nanometer-realm, new effects emerge which reflect certain features of biological systems although the system is inorganic in nature. This behaviour is shown by realistic molecular dynamics calculations in connection with aluminum-nanoclusters at various temperatures. The clusters can transform without external influence from a metastable into a stable state, and there can be more than one stable state, that is, we observe a bifurcation in the sense of chaos-theory. The stable states can differ in both the atomic structure and the outer shape. 相似文献
136.
137.
138.
139.
Lanthanide Identity Governs Guest-Induced Dimerization in LnIII[15-MC
N(L-pheHA)-5])3+ Metallacrowns
Prof. Carmelo Sgarlata Bernadette L. Schneider Valeria Zito Dr. Rossella Migliore Prof. Matteo Tegoni Prof. Vincent L. Pecoraro Prof. Giuseppe Arena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17669-17675
Series of lanthanide-containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (LnIII[15-MC N(L-pheHA)-5])3+ metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host-guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric host-guest-host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides). 相似文献
140.