全文获取类型
收费全文 | 789篇 |
免费 | 21篇 |
国内免费 | 54篇 |
专业分类
化学 | 306篇 |
晶体学 | 1篇 |
力学 | 28篇 |
数学 | 199篇 |
物理学 | 330篇 |
出版年
2024年 | 1篇 |
2023年 | 74篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 14篇 |
2018年 | 13篇 |
2017年 | 25篇 |
2016年 | 19篇 |
2015年 | 16篇 |
2014年 | 57篇 |
2013年 | 98篇 |
2012年 | 37篇 |
2011年 | 49篇 |
2010年 | 37篇 |
2009年 | 49篇 |
2008年 | 30篇 |
2007年 | 25篇 |
2006年 | 30篇 |
2005年 | 22篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 20篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 3篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有864条查询结果,搜索用时 31 毫秒
101.
Yanan Chang Zhangyu Ma Xuyun Lu Shasha Wang Prof. Jianchun Bao Prof. Ying Liu Prof. Chao Ma 《Angewandte Chemie (International ed. in English)》2023,62(41):e202310163
The rational design of advanced nanohybrids (NHs) with optimized interface electronic environment and rapid reaction kinetics is pivotal to electrocatalytic schedule. Herein, we developed a multiple heterogeneous Co9S8/Co3S4/Cu2S nanoparticle in which Co3S4 germinates between Co9S8 and Cu2S. Using high-angle annular-dark-field imaging and theoretical calculation, it was found that the integration of Co9S8 and Cu2S tends to trigger the interface phase transition of Co9S8, leading to Co3S4 interlayer due to the low formation energy of Co3S4/Cu2S (−7.61 eV) than Co9S8/Cu2S (−5.86 eV). Such phase transition not only lowers the energy barrier of oxygen evolution reaction (OER, from 0.335 eV to 0.297 eV), but also increases charge carrier density (from 7.76×1014 to 2.09×1015 cm−3), and creates more active sites. Compared to Co9S8 and Cu2S, the Co9S8/Co3S4/Cu2S NHs also demonstrate notable photothermal effect that can heat the catalyst locally, offset the endothermic enthalpy change of OER, and promote carrier migrate, reaction intermediates adsorption/deprotonation to improve reaction kinetics. Profiting from these favorable factors, the Co9S8/Co3S4/Cu2S catalyst only requires an OER overpotential of 181 mV and overall water splitting cell voltage of 1.43 V to driven 10 mA cm−2 under the irradiation of near-infrared light, outperforming those without light irradiation and many reported Co-based catalysts. 相似文献
102.
ChangYan Hu Dr. Ying Li Dr. Dong Wang Dr. Chunjin Wu Feng Chen Linghong Zhang Prof. Fang Wan Prof. Weibo Hua Prof. Yan Sun Prof. Benhe Zhong Dr. Zhenguo Wu Prof. Xiaodong Guo 《Angewandte Chemie (International ed. in English)》2023,62(46):e202312310
Na2Ti6O13 (NTO) with high safety has been regarded as a promising anode candidate for sodium-ion batteries. In the present study, integrated modification of migration channels broadening, charge density re-distribution, and oxygen vacancies regulation are realized in case of Nb-doping and have obtained significantly enhanced cycling performance with 92 % reversible capacity retained after 3000 cycles at 3000 mA g−1. Moreover, unexpected low-temperature performance with a high discharge capacity of 143 mAh g−1 at 100 mA g−1 under −15 °C is also achieved in the full cell. Theoretical investigation suggests that Nb preferentially replaces Ti3 sites, which effectively improves structural stability and lowers the diffusion energy barrier. What's more important, both the in situ X-ray diffraction (XRD) and in situ Raman furtherly confirm the robust spring effect of the Ti−O bond, making special charge compensation mechanism and respective regulation strategy to conquer the sluggish transport kinetics and low conductivity, which plays a key role in promoting electrochemical performance. 相似文献
103.
Hongbin Dai Prof. Ran Hong Yafei Ma Dr. Xiaoxiao Cheng Prof. Wei Zhang 《Angewandte Chemie (International ed. in English)》2023,62(50):e202314848
Precise control over the chirality and morphologies of polymer assemblies, a remaining challenge for both chemists and materials scientists, is receiving ever-increasing attention in the recent years. Herein, we report the subtle manipulation of the achiral spacers from the chiral stereocenter to the azobenzene (Azo) unit, of which the chiroptical consistency or chiroptical inversion of self-assemblies could be successfully controlled and present “two-fold” odd-even effect. Furthermore, morphological transitions from 0D spherical micelles, 1D worms, and nanowires to 3D vesicles, spindle- and dumbbell-shaped vesicles were also unexpectedly found to exhibit odd-even correlations. These observations were collectively elucidated by mesomorphic properties, stacking modes, chiroptical dynamics, and stimuli-responsive behaviors. Negligible modifications to the spacer structures can enable remarkable modulation of supramolecular chirality and anisotropic topologies in polymer assemblies, which is of great significance for the design of complex chiral functional polymers. 相似文献
104.
Starting from a field theory action that describes a Dirac fermion, we propose and analyze a model based on a low‐relativistic Pauli equation coupled to a torsion‐like term to study Spin Hall Effect (SHE). We point out a very particular connection between the modified Pauli equation and the (SHE), where what we refer to torsion as field playing an important role in the spin‐orbit (SO) coupling process. In this scenario, we present a proposal of a spin‐type current, considering the tiny contributions of torsion in connection with intrinsic anisotropy of the crystal electric field. 相似文献
105.
For Gaussian process models, likelihood-based methods are often difficult to use with large irregularly spaced spatial datasets, because exact calculations of the likelihood for n observations require O(n3) operations and O(n2) memory. Various approximation methods have been developed to address the computational difficulties. In this article, we propose new, unbiased estimating equations (EE) based on score equation approximations that are both computationally and statistically efficient. We replace the inverse covariance matrix that appears in the score equations by a sparse matrix to approximate the quadratic forms, then set the resulting quadratic forms equal to their expected values to obtain unbiased EE. The sparse matrix is constructed by a sparse inverse Cholesky approach to approximate the inverse covariance matrix. The statistical efficiency of the resulting unbiased EE is evaluated both in theory and by numerical studies. Our methods are applied to nearly 90,000 satellite-based measurements of water vapor levels over a region in the Southeast Pacific Ocean. 相似文献
106.
107.
108.
为了提高全色图像与多光谱图像的融合质量,提出一种基于非下采样双树复轮廓波变换和稀疏表示的图像融合算法.对多光谱图像进行亮度-色度-饱和度变换,再对亮度分量和全色图像进行直方图匹配及亮度平滑滤波处理.利用非下采样双树复轮廓波变换处理亮度分量和全色图像,得到对应的高低频系数.对于低频系数,利用稀疏表示进行融合,采用空间频率和l1范数双指标取大的融合规则得到稀疏表示系数;对于高频系数,将改进的拉普拉斯能量和作为脉冲耦合神经网络的外部输入项,提出了改进的脉冲耦合神经网络的融合策略.最后进行非下采样双树复轮廓波逆变换和亮度-色度-饱和度逆变换得到融合结果.实验结果表明,该算法最大限度地保留光谱信息的同时可以提高空间分辨率,视觉效果及客观指标均优于经典的融合算法. 相似文献
109.
110.
A new experimental technique has been developed to investigate the onset of fracture in metals at low and intermediate stress
triaxialities. The gage section of a flat specimen has been designed such that cracks are most likely to initiate within the
specimen center, remote from the specimen boundaries. Along with the specimen, a biaxial testing device has been built to
apply a well-defined displacement field to the specimen shoulders. The stress state within the specimen is adjusted by changing
the biaxial loading angle. Using this new experimental technique, the crack initiation in metals can be studied experimentally
for stress triaxialities ranging from 0.0 to 0.6. The stress and strain fields within the specimen gage section are determined
from finite element analysis. The reliability of the computational model of the test set-up has been verified by comparing
the simulation results with laser speckle-interferometric displacement measurements during testing. Sample experiments have
been performed on the Al-7Si-Mg gravity die casting alloy. A three-step hybrid experimental–numerical calibration procedure
has been proposed and applied to determine a phenomenological crack formation criterion for the Al-7Si-Mg alloy.
相似文献
D. MohrEmail: |