全文获取类型
收费全文 | 674篇 |
免费 | 22篇 |
国内免费 | 4篇 |
专业分类
化学 | 438篇 |
晶体学 | 9篇 |
力学 | 14篇 |
数学 | 79篇 |
物理学 | 160篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 17篇 |
2014年 | 27篇 |
2013年 | 47篇 |
2012年 | 69篇 |
2011年 | 60篇 |
2010年 | 40篇 |
2009年 | 31篇 |
2008年 | 51篇 |
2007年 | 30篇 |
2006年 | 29篇 |
2005年 | 44篇 |
2004年 | 34篇 |
2003年 | 31篇 |
2002年 | 36篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有700条查询结果,搜索用时 296 毫秒
691.
This paper examines the estimation of an indirect signal embedded in white noise on vector bundles. It is found that the sharp asymptotic minimax bound is determined by the degree to which the indirect signal is embedded in the linear operator. Thus when the linear operator has polynomial decay, recovery of the signal is polynomial where the exact minimax constant and rate are determined. Adaptive sharp estimation is carried out using a blockwise shrinkage estimator. Application to the spherical deconvolution problem for the polynomially bounded case is made. 相似文献
692.
Jihoon JeonSangkyun Koo 《Journal of magnetism and magnetic materials》2012,324(4):424-429
We investigate the viscosity behavior of a magnetic suspension in which magnetic particles are dispersed in a mixture of polyacrylic liquids. The size of magnetite particles is nearly 300 nm and the volume fraction of the magnetic particles is in the range of 0.003-0.03. The particle concentration dependence of the suspension viscosity yields the intrinsic viscosity [η], which varies from 25.6 at 5 s−1 to 5.1 at 400 s−1. The yield stress and the infinite shear viscosity of the suspension increase non-linearly as the particle concentration ? increases. We examine the effect of process conditions such as milling time and amount of dispersant on the viscosity behavior of the suspension. As milling time elapses, yield stress and low shear viscosity decrease and then reach constant values while the infinite shear viscosity remains constant. When oleic acid is added as a dispersant, the yield stress and low shear viscosity of the suspension show minimum values as the amount of oleic acid increases. These results agree with experimental results of sedimentation tests, which enable us to estimate the aggregate size of magnetic suspension. The yield stress and the low shear viscosity of the magnetic suspension are found to be useful in evaluating the dispersion state of the magnetic suspension. 相似文献
693.
To examine the difference between the magnetic structures of Sr2MGe2O7 (M=Mn, Co), we evaluated their spin exchange interactions by performing energy-mapping analysis based on density functional theory calculations. The calculated intra- and inter-layer spin exchanges correctly predict the G-type and C-type antiferromagnetic structures of Sr2MnGe2O7 and Sr2CoGe2O7, respectively, and the Curie–Weiss temperatures estimated from these spin exchanges are also in good agreement with the experiment. The ∥c and ⊥c orientations of the spins in the ordered magnetic structures of Sr2MnGe2O7 and Sr2CoGe2O7, respectively, were also examined by considering spin–orbit coupling. 相似文献
694.
Je Huan Koo 《Solid State Communications》2012,152(1):5-7
We propose a finite block spin phenomenology for permanent magnets in which we consider an average domain as a block spin. The permanent ferromagnetism arises in two ways: (1) the ferromagnetism that occurs inside a big block spin, i.e. the intrablock ferromagnetism, and the ferromagnetism between small block spins (SBSs) in a big block spin (BBS) which can be induced by collective ferromagnetic pairing between two SBSs mediated by temperature-irreversible bosonic strains; and (2) the ferromagnetism between BBSs, i.e. the interblock ferromagnetism. The coercivity originates from temperature-irreversible strains treated as external phonons. 相似文献
695.
Byoungseon Jeon Changhyun Ko Adri C.T. van Duin Shriram Ramanathan 《Surface science》2012,606(3-4):516-522
Compositional stability of various vanadium oxides and oxide growth on vanadium surfaces have been studied using reactive molecular dynamics simulation methods. Vanadium dioxide (VO2), sesquioxide (V2O3), pentoxide (V2O5), and hexavanadium tridecaoxide (V6O13) are studied in bulk crystalline and thin film structures, investigating charge distribution and pair distribution functions of particle interactions. The stability is estimated to be pentoxide, hexavanadium tridecaoxide, sesquioxide, and dioxide respectively in decreasing order in thin film structures. We then analyze oxide growth kinetics on vanadium (100) and (110) surfaces. The oxidation rate, stoichiometry, charge distribution, and the effect of surface orientation on kinetic phenomena are noted. In the early stages of surface oxidation of our simulation configurations, sesquioxide is found to be the dominant component. The modeling and simulation results are compared with experiments where available. 相似文献
696.
SnO2-core/In2O3-shell nanobelts were fabricated by a two-step process comprising thermal evaporation of Sn powders and sputter-deposition of In2O3. Transmission electron microscopy and X-ray diffraction analyses revealed that the core of a typical core–shell nanobelt comprised a simple tetragonal-structured single crystal SnO2 and that the shell comprised an amorphous In2O3. Multiple networked SnO2-core/In2O3-shell nanobelt sensors showed the response of 5.35% at a NO2 concentration of 10 ppm at 300 °C. This response value is more than three times larger than that of bare-SnO2 nanobelt sensors at the same NO2 concentration. The enhancement in the sensitivity of SnO2 nanobelts to NO2 gas by sheathing the nanobelts with In2O3 can be accounted for by the modulation of electron transport by the In2O3–In2O3 homojunction. 相似文献
697.
Changhyun Jin Hyunsoo Kim Kyungjoon Baek Hyoun Woo Kim Chongmu Lee 《Crystal Research and Technology》2010,45(2):199-203
Ga2O3/SnO2 coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO2. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis results indicate that the Ga2O3 cores and the SnO2 shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO2 shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H2/N2 atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H2/N2 annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
698.
Lintao Zeng Tianhong Chen Beitong Zhu Seyoung Koo Yonghe Tang Weiying Lin Tony D. James Jong Seung Kim 《Chemical science》2022,13(16):4523
Chemical warfare agents (CWAs) such as phosgene and nerve agents pose serious threats to our lives and public security, but no tools can simultaneously screen multiple CWAs in seconds. Here, we rationally designed a robust sensing platform based on 8-cyclohexanyldiamino-BODIPY (BODIPY-DCH) to monitor diverse CWAs in different emission channels. Trans-cyclohexanyldiamine as the reactive site provides optimal geometry and high reactivity, allowing trans-BODIPY-DCH to detect CWAs with a quick response and high sensitivity, while cis-BODIPY-DCH has much weaker reactivity to CWAs due to intramolecular H-bonding. Upon reaction with phosgene, trans-BODIPY-DCH was rapidly converted to imidazolone BODIPY (<3 s), triggering green fluorescence with good sensitivity (LOD = 0.52 nM). trans-BODIPY-DCH coupled with nerve agent mimics, affording a blue fluorescent 8-amino-BODIPY tautomer. Furthermore, a portable test kit using trans-BODIPY-DCH displayed an instant response and low detection limits for multiple CWAs. This platform enables rapid and highly sensitive visual screening of various CWAs.Chemical warfare agents (CWAs) such as phosgene and nerve agents pose serious threats to our lives and public security, necessitating tools that can simultaneously screen multiple CWAs in seconds. 相似文献
699.
700.