全文获取类型
收费全文 | 3006篇 |
免费 | 125篇 |
国内免费 | 16篇 |
专业分类
化学 | 1603篇 |
晶体学 | 3篇 |
力学 | 107篇 |
综合类 | 1篇 |
数学 | 580篇 |
物理学 | 853篇 |
出版年
2023年 | 23篇 |
2021年 | 23篇 |
2020年 | 63篇 |
2019年 | 38篇 |
2018年 | 57篇 |
2017年 | 31篇 |
2016年 | 73篇 |
2015年 | 83篇 |
2014年 | 72篇 |
2013年 | 123篇 |
2012年 | 157篇 |
2011年 | 154篇 |
2010年 | 81篇 |
2009年 | 80篇 |
2008年 | 130篇 |
2007年 | 122篇 |
2006年 | 135篇 |
2005年 | 124篇 |
2004年 | 90篇 |
2003年 | 71篇 |
2002年 | 63篇 |
2001年 | 84篇 |
2000年 | 61篇 |
1999年 | 42篇 |
1998年 | 26篇 |
1997年 | 29篇 |
1996年 | 33篇 |
1995年 | 24篇 |
1994年 | 29篇 |
1993年 | 36篇 |
1992年 | 36篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 21篇 |
1987年 | 27篇 |
1986年 | 27篇 |
1985年 | 38篇 |
1984年 | 34篇 |
1983年 | 38篇 |
1982年 | 27篇 |
1981年 | 31篇 |
1980年 | 23篇 |
1979年 | 26篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1974年 | 27篇 |
1973年 | 27篇 |
1955年 | 22篇 |
1954年 | 23篇 |
排序方式: 共有3147条查询结果,搜索用时 328 毫秒
1.
2.
Atefeh Ashouri Saeed Mahdavifar Grégoire Misguich Javad Vahedi 《Annalen der Physik》2020,532(8):1900515
There has been some substantial research about the connections between quantum chaos and quantum correlations in many-body systems. This paper discusses a specific aspect of correlations in chaotic spin models, through concurrence (CC) and quantum discord (QD). Numerical results obtained in the quantum chaos regime and in the integrable regime of spin-1/2 chains are compared. The CC and QD between nearest-neighbor pairs of spins are calculated for all energy eigenstates. The results show that, depending on whether the system is in a chaotic or integrable regime, the distribution of CC and QD are markedly different. On the other hand, in the integrable regime, states with the largest CC and QD are found in the middle of the spectrum, in the chaotic regime, the states with the strongest correlations are found at low and high energies at the edges of spectrum. Finite-size effects are analyzed, and some of the results are discussed in the light of the eigenstate thermalization hypothesis. 相似文献
3.
Dr. Carlos Sánchez-Sánchez Dr. Thomas Dienel Dr. Adrien Nicolaï Dr. Neerav Kharche Dr. Liangbo Liang Colin Daniels Prof. Vincent Meunier Dr. Junzhi Liu Prof. Xinliang Feng Prof. Klaus Müllen Dr. Juan Ramón Sánchez-Valencia Dr. Oliver Gröning Dr. Pascal Ruffieux Prof. Roman Fasel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12074-12082
A bottom up method for the synthesis of unique tetracene-based nanoribbons, which incorporate cyclobutadiene moieties as linkers between the acene segments, is reported. These structures were achieved through the formal [2+2] cycloaddition reaction of ortho-functionalized tetracene precursor monomers. The formation mechanism and the electronic and magnetic properties of these nanoribbons were comprehensively studied by means of a multitechnique approach. Ultra-high vacuum scanning tunneling microscopy showed the occurrence of metal-coordinated nanostructures at room temperature and their evolution into nanoribbons through formal [2+2] cycloaddition at 475 K. Frequency-shift non-contact atomic force microscopy images clearly proved the presence of bridging cyclobutadiene moieties upon covalent coupling of activated tetracene molecules. Insight into the electronic and vibrational properties of the so-formed ribbons was obtained by scanning tunneling microscopy, Raman spectroscopy, and theoretical calculations. Magnetic properties were addressed from a computational point of view, allowing us to propose promising candidates to magnetic acene-based ribbons incorporating four-membered rings. The reported findings will increase the understanding and availability of new graphene-based nanoribbons with high potential in future spintronics. 相似文献
4.
Yingchun Wu Haipeng Li Xuecheng Wu Gérard Gréhan Lutz Mädler Cyril Crua 《Proceedings of the Combustion Institute》2019,37(3):3211-3218
Droplet evaporation characterization, although of great significance, is still challenging. The recently developed phase rainbow refractometry (PRR) is proposed as an approach to measuring the droplet temperature, size as well as evaporation rate simultaneously, and is applied to a single flowing n-heptane droplet produced by a droplet-on-demand generator. The changes of droplet temperature and evaporation rate after a transient spark heating are reflected in the time-resolved PRR image. Results show that droplet evaporation rate increases with temperature, from ?1.28 m2/s at atmospheric 293 K to a range of (?1.5, ?8) m2/s when heated to (294, 315) K, agreeing well with the Maxwell and Stefan–Fuchs model predictions. Uncertainty analysis suggests that the main source is the indeterminate gradient inside droplet, resulting in an underestimation of droplet temperature and evaporation rate. With the demonstration on simultaneous measurements of droplet refractive index as well as droplet transient and local evaporation rate in this work, PRR is a promising tool to investigate single droplet evaporation in real engine conditions. 相似文献
5.
6.
G. Grätzer 《Algebra Universalis》2015,74(3-4):351-359
7.
8.
9.
Dr. Jan Nekvinda Michael Kugler Dr. Josef Holub Dr. Suzan El Anwar Dr. Jiří Brynda Klára Pospíšilová Dr. Zdeňka Růžičková Dr. Pavlína Řezáčová Dr. Bohumír Grüner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16541-16553
Carbonic anhydrase IX (CA IX), a tumor-associated metalloenzyme, represents a validated target for cancer therapy and diagnostics. Herein, we report the inhibition properties of isomeric families of sulfonamidopropyl-dicarba-closo-dodecaboranes group(s) prepared using a new direct five-step synthesis from the corresponding parent cages. The protocol offers a reliable solution for synthesis of singly and doubly substituted dicarba-closo-dodecaboranes with a different geometric position of carbon atoms. The closo-compounds from the ortho- and meta-series were then degraded to corresponding 11-vertex dicarba-nido-undecaborate(1−) anions. All compounds show in vitro enzymatic activity against CA IX in the low nanomolar or subnanomolar range. This is accompanied by clear isomer dependence of the inhibition constant (Ki) and selectivity towards CA IX. Decreasing trends in Ki and selectivity index (SI) values are observed with increasing separation of the cage carbon atoms. Interactions of compounds with the active sites of CA IX were explored with X-ray crystallography, and eight high-resolution crystal structures uncovered the structural basis of inhibition potency and selectivity. 相似文献
10.
Experimental Mechanics - Digital Image Correlation (DIC) and Localized Spectrum Analysis (LSA) are two techniques available to extract displacement fields from images of deformed surfaces marked... 相似文献