全文获取类型
收费全文 | 14940篇 |
免费 | 2130篇 |
国内免费 | 1636篇 |
专业分类
化学 | 5571篇 |
晶体学 | 92篇 |
力学 | 961篇 |
综合类 | 233篇 |
数学 | 7746篇 |
物理学 | 4103篇 |
出版年
2024年 | 30篇 |
2023年 | 122篇 |
2022年 | 230篇 |
2021年 | 307篇 |
2020年 | 434篇 |
2019年 | 554篇 |
2018年 | 396篇 |
2017年 | 524篇 |
2016年 | 608篇 |
2015年 | 489篇 |
2014年 | 755篇 |
2013年 | 1205篇 |
2012年 | 838篇 |
2011年 | 915篇 |
2010年 | 793篇 |
2009年 | 1022篇 |
2008年 | 1019篇 |
2007年 | 991篇 |
2006年 | 842篇 |
2005年 | 753篇 |
2004年 | 728篇 |
2003年 | 691篇 |
2002年 | 599篇 |
2001年 | 428篇 |
2000年 | 421篇 |
1999年 | 397篇 |
1998年 | 361篇 |
1997年 | 337篇 |
1996年 | 281篇 |
1995年 | 202篇 |
1994年 | 196篇 |
1993年 | 150篇 |
1992年 | 137篇 |
1991年 | 98篇 |
1990年 | 99篇 |
1989年 | 74篇 |
1988年 | 58篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 61篇 |
1984年 | 47篇 |
1983年 | 32篇 |
1982年 | 63篇 |
1981年 | 55篇 |
1980年 | 37篇 |
1979年 | 64篇 |
1978年 | 34篇 |
1977年 | 37篇 |
1976年 | 24篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The chiral phase transition and equation of state are studied within a novel self-consistent mean-field approximation of the two-flavor Nambu-Jona-Lasinio model. In this newly developed model, modifications to the chemical μ and chiral chemical \begin{document}$\mu_5$\end{document} ![]()
![]()
potentials are naturally included by introducing vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian. In the proper-time scheme, the chiral phase transition is a crossover in the \begin{document}$T-\mu$\end{document} ![]()
![]()
plane. However, when \begin{document}$\mu_5$\end{document} ![]()
![]()
is incorporated, our study demonstrates that a first order phase transition may emerge. Furthermore, the chiral imbalance will soften the equation of state of quark matter. The mass-radius relationship and tidal deformability of quark stars are calculated. The maximum mass and radius decrease as \begin{document}$\mu_5$\end{document} ![]()
![]()
increases. Our study also indicates that the vector and axial-vector channels exhibit an opposite influence on the equation of state. 相似文献
3.
4.
5.
Functional Carbazole Liquid‐Crystal Block Codendrimers with Optical and Electronic Properties
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ismael Gracia Beatriz Feringán Prof. José Luis Serrano Dr. Roberto Termine Dr. Attilio Golemme Dr. Ana Omenat Prof. Joaquín Barberá 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1359-1369
The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole‐containing 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) dendrons are reported. The liquid‐crystal behaviour was investigated by means of differential scanning calorimetry, polarised‐light optical microscopy and X‐ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role. 相似文献
6.
7.
8.
Ieva
Dauickait Amos S. Lawless Jennifer A. Scott Peter Jan van Leeuwen 《Numerical Linear Algebra with Applications》2020,27(5)
We consider the large sparse symmetric linear systems of equations that arise in the solution of weak constraint four‐dimensional variational data assimilation, a method of high interest for numerical weather prediction. These systems can be written as saddle point systems with a 3 × 3 block structure but block eliminations can be performed to reduce them to saddle point systems with a 2 × 2 block structure, or further to symmetric positive definite systems. In this article, we analyse how sensitive the spectra of these matrices are to the number of observations of the underlying dynamical system. We also obtain bounds on the eigenvalues of the matrices. Numerical experiments are used to confirm the theoretical analysis and bounds. 相似文献
9.
通过耦合三维微波腔中光子和腔内钇铁石榴石单晶小球中的自旋波量子形成腔-自旋波量子的耦合系统,并通过精确调节系统参数在该实验系统中观测到各向异性奇异点.奇异点对应于非厄米系统中一种特殊状态,在奇异点处,耦合系统的本征值和本征矢均简并,并且往往伴随着非平庸的物理性质.以往大量研究主要集中在各向同性奇异点的范畴,它的特征是在系统参数空间中沿着不同参数坐标趋近该奇异点时具有相同的函数关系.在这篇文章中,主要介绍实验上在腔光子-自旋波量子耦合系统中通过调节系统的耦合强度和腔的耗散衰减系数两条趋近奇异点的路径而实现了各向异性奇异点,具体分别对应于在趋近奇异点时,本征值的虚部的变化与耦合强度和腔的衰减系数的变化会有线性和平方根不同的行为.各向异性奇异点的实现有助于基于腔光子-自旋波量子耦合系统的量子信息处理和精密探测器件的进一步研究. 相似文献
10.
Hideaki Murasugi Dr. Shohei Kumagai Dr. Hiroaki Iguchi Prof. Dr. Masahiro Yamashita Dr. Shinya Takaishi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9885-9891
Crystal structures of a series of organic–inorganic hybrid gold iodide perovskites, formulated as A2[AuII2][AuIIII4] [A=methylammonium (MA) ( 1 ) and formamidinium (FA) ( 2 )], A′2[I3]1−x[AuII2]x[AuIIII4] [A′=imidazolium (IMD) ( 3 ), guanidinium (GUA) ( 4 ), dimethylammonium (DMA) ( 5 ), pyridinium (PY) ( 6 ), and piperizinium (PIP) ( 7 )], systematically changed depending on the cation size. In addition, triiodide (I3−) ions were partly incorporated into the AuI2− sites of 3 – 7 , whereas they were not incorporated into those of 1 and 2 . Such a difference comes from the size of the organic cation. Optical absorption spectra showed characteristic intervalence charge-transfer bands from AuI to AuIII species, and the optical band gap increased as the size of the cation became larger. 相似文献