全文获取类型
收费全文 | 5939篇 |
免费 | 536篇 |
国内免费 | 866篇 |
专业分类
化学 | 2786篇 |
晶体学 | 25篇 |
力学 | 450篇 |
综合类 | 81篇 |
数学 | 2928篇 |
物理学 | 1071篇 |
出版年
2024年 | 5篇 |
2023年 | 64篇 |
2022年 | 68篇 |
2021年 | 135篇 |
2020年 | 169篇 |
2019年 | 175篇 |
2018年 | 162篇 |
2017年 | 169篇 |
2016年 | 210篇 |
2015年 | 180篇 |
2014年 | 275篇 |
2013年 | 477篇 |
2012年 | 280篇 |
2011年 | 320篇 |
2010年 | 273篇 |
2009年 | 384篇 |
2008年 | 423篇 |
2007年 | 417篇 |
2006年 | 399篇 |
2005年 | 318篇 |
2004年 | 304篇 |
2003年 | 294篇 |
2002年 | 245篇 |
2001年 | 226篇 |
2000年 | 233篇 |
1999年 | 147篇 |
1998年 | 140篇 |
1997年 | 125篇 |
1996年 | 117篇 |
1995年 | 123篇 |
1994年 | 91篇 |
1993年 | 75篇 |
1992年 | 64篇 |
1991年 | 51篇 |
1990年 | 31篇 |
1989年 | 15篇 |
1988年 | 25篇 |
1987年 | 25篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1957年 | 1篇 |
排序方式: 共有7341条查询结果,搜索用时 218 毫秒
1.
《Indagationes Mathematicae》2021,32(6):1229-1239
2.
We study the Leibniz n-algebra Un(∑),whose multiplication is defined viathe bracket of a Leibniz algebra ∑ as[x1,...,xn]=[x1,[...,[xn-2,[xn-1,xn]]...]].Weshow that Un(∑) is simple if and only if ∑ is a simple Lie algebra.An analog of Levi'stheorem for Leibniz algebras in Un(Lb) is established and it is proven that the Leibnizn-kernel of Un(Σ) for any semisimple Leibniz algebra Σ is the n-algebra Un(Σ). 相似文献
3.
4.
5.
6.
Polina Kapitanova Esmaeel Zanganeh Nikita Pavlov Mingzhao Song Pavel Belov Andrey Evlyukhin Andrey Miroshnichenko 《Annalen der Physik》2020,532(12):2000293
The existence of non-radiating electromagnetic sources attracts much attention in photonic community and gives rise to extensive discussions of various applications in lasing, medical imaging, sensing, and nonlinear optics. In this article, the existence of magnetic anapole states (or magnetic-type non-radiating sources) characterized by a suppressed magnetic dipole radiation in a dielectric cylindrical particle is theoretically predicted and experimentally demonstrated. The specific features of the magnetic anapole state under ideal conditions are identified, followed by a demonstration of how their existence can be detected in practical structures. The concept is valid in various frequency bands from visible range for nanoparticles to microwave range for millimeter size objects. The experimental study is performed in microwave frequency range which allows not only to measure the far-field (scattered field) characteristics, but also to probe the peculiar field profile directly inside the dielectric particle. The experimental results agree well with the analytical ones and pave the way to detect and identify nontrivial different-type anapole states. 相似文献
7.
Cycloelimination of Imidazolidin‐2‐ylidene N‐Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable “NHC‐CDI” Amidinates 下载免费PDF全文
Aleksandr V. Zhukhovitskiy Julie Geng Prof. Dr. Jeremiah A. Johnson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5685-5688
We report the discovery that 1,3‐bis(aryl)imidazolidin‐2‐ylidenes, one of the most widely studied classes of N‐heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic “NHC‐CDI” amidinates upon heating to ≈100 °C in solution. The mechanism of this novel NHC decomposition process is studied in detail. These studies enabled the rational synthesis of a new class of bench stable amidinates from a panel of NHCs and carbodiimides. We expect these constructs to find utility in a variety of applications. 相似文献
8.
Gallai’s path decomposition conjecture states that the edges of any connected graph on vertices can be decomposed into at most paths. We confirm that conjecture for all graphs with maximum degree at most five. 相似文献
9.
《Comptes Rendus Mecanique》2019,347(11):780-792
The present work aims at proposing a new methodology for learning reduced models from a small amount of data. It is based on the fact that discrete models, or their transfer function counterparts, have a low rank and then they can be expressed very efficiently using few terms of a tensor decomposition. An efficient procedure is proposed as well as a way for extending it to nonlinear settings while keeping limited the impact of data noise. The proposed methodology is then validated by considering a nonlinear elastic problem and constructing the model relating tractions and displacements at the observation points. 相似文献
10.
应用互补集成经验模态分解(CEEMD)方法对香港1997―2018年的住宅价格月度数据进行了分解,将经过重构后的数据分成高频序列、低频序列与残差项。将BP多断点检测应用于低频序列,并结合样本时段内的重大事件进行实证分析。结果表明:1997年亚洲金融风暴对房价的影响大于2008年金融危机;外部经济体的救市政策间接地影响香港房价;在经济不景气的大环境下“孙九招”政策没有立即见效;资本投资者入境计划、住房供给调整与按揭贷款调整对房价的影响较为显著;税收调整对房价影响不显著、对交易量影响显著;SARS爆发使住宅价格下降约1%。 相似文献