全文获取类型
收费全文 | 388282篇 |
免费 | 8434篇 |
国内免费 | 5917篇 |
专业分类
化学 | 196625篇 |
晶体学 | 5401篇 |
力学 | 20389篇 |
综合类 | 380篇 |
数学 | 57797篇 |
物理学 | 122041篇 |
出版年
2021年 | 3318篇 |
2020年 | 3887篇 |
2019年 | 4154篇 |
2018年 | 12465篇 |
2017年 | 13004篇 |
2016年 | 10168篇 |
2015年 | 5250篇 |
2014年 | 6750篇 |
2013年 | 13380篇 |
2012年 | 15861篇 |
2011年 | 24775篇 |
2010年 | 16386篇 |
2009年 | 16319篇 |
2008年 | 21789篇 |
2007年 | 24610篇 |
2006年 | 11874篇 |
2005年 | 15957篇 |
2004年 | 12241篇 |
2003年 | 11353篇 |
2002年 | 9692篇 |
2001年 | 9062篇 |
2000年 | 7111篇 |
1999年 | 5146篇 |
1998年 | 4471篇 |
1997年 | 4202篇 |
1996年 | 4321篇 |
1995年 | 3677篇 |
1994年 | 3845篇 |
1993年 | 3622篇 |
1992年 | 3809篇 |
1991年 | 3921篇 |
1990年 | 3719篇 |
1989年 | 3550篇 |
1988年 | 3404篇 |
1987年 | 3317篇 |
1986年 | 3308篇 |
1985年 | 4162篇 |
1984年 | 4193篇 |
1983年 | 3550篇 |
1982年 | 3769篇 |
1981年 | 3495篇 |
1980年 | 3231篇 |
1979年 | 3530篇 |
1978年 | 3764篇 |
1977年 | 3699篇 |
1976年 | 3861篇 |
1975年 | 3516篇 |
1974年 | 3629篇 |
1973年 | 3714篇 |
1972年 | 2959篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
We consider conformal gravity as a gauge natural theory. We study its conservation laws and superpotentials. We also consider the Mannheim and Kazanas spherically symmetric vacuum solution and discuss conserved quantities associated to conformal and diffeomorphism symmetries. 相似文献
73.
A. Lashgari S. Ghammamy R. Ramirez-Tagle G. Salgado-Moran 《Journal of Structural Chemistry》2015,56(8):1505-1513
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data. 相似文献
74.
We present the fabrication of core-shell-satellite Au@SiO2-Pt nanostructures and demonstrate that LSPR excitation of the core Au nanoparticle can induce plasmon coupling effect to initiate photocatalytic hydrogen generation from decomposition of formic acid. Further studies suggest that the plasmon coupling effect induces a strong local electric field between the Au core and Pt nanoparticles on the SiO2 shell, which enables creation of hot electrons on the non-plasmonic-active Pt nanoparticles to participate hydrogen evolution reaction on the Pt surface. In addition, small SiO2 shell thickness is required in order to obtain a strong plamon coupling effect and achieve efficient photocatalytic activities for hydrogen generation. 相似文献
75.
Khusnutdinov R. I. Shchadneva N. A. Mayakova Yu. Yu. Aminov R. I. 《Russian Journal of Organic Chemistry》2021,57(6):950-953
Russian Journal of Organic Chemistry - Binder-free iron- and nickel-containing micro-, meso-, and macroporous zeolites FeHY and NiHY were found to effectively catalyze Knoevenagel condensation of... 相似文献
76.
Wu Shang-Zhuo Yu Qiang Li Yue-Hua Cui Guang-Hua 《Research on Chemical Intermediates》2021,47(2):835-851
Research on Chemical Intermediates - Combination of three aromatic carboxylic acids (5-nitroisophthalic acid (H2nip), 2,6-naphthalenedicarboxylic acid (H2ndc), tetrabromoterephthalic acid (H2tbta))... 相似文献
77.
Journal of Thermal Analysis and Calorimetry - In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame... 相似文献
78.
Du Yongbo Yu Pengfei Wang Junxiong Zhang Jinping Wang Chang’an Che Defu 《Journal of Thermal Analysis and Calorimetry》2021,143(1):327-334
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential... 相似文献
79.
80.
Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups... 相似文献