全文获取类型
收费全文 | 2462篇 |
免费 | 321篇 |
国内免费 | 270篇 |
专业分类
化学 | 1690篇 |
晶体学 | 29篇 |
力学 | 164篇 |
综合类 | 22篇 |
数学 | 241篇 |
物理学 | 907篇 |
出版年
2024年 | 3篇 |
2023年 | 47篇 |
2022年 | 79篇 |
2021年 | 103篇 |
2020年 | 99篇 |
2019年 | 91篇 |
2018年 | 73篇 |
2017年 | 89篇 |
2016年 | 132篇 |
2015年 | 120篇 |
2014年 | 164篇 |
2013年 | 164篇 |
2012年 | 243篇 |
2011年 | 289篇 |
2010年 | 140篇 |
2009年 | 179篇 |
2008年 | 131篇 |
2007年 | 127篇 |
2006年 | 136篇 |
2005年 | 84篇 |
2004年 | 86篇 |
2003年 | 55篇 |
2002年 | 51篇 |
2001年 | 30篇 |
2000年 | 47篇 |
1999年 | 43篇 |
1998年 | 35篇 |
1997年 | 33篇 |
1996年 | 33篇 |
1995年 | 21篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 20篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1959年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有3053条查询结果,搜索用时 31 毫秒
101.
This paper presents a microsensor chip integrated with a gold nanoparticles‐modified ultramicroelectrode array (UMEA) as the working electrode for the detection of copper ions in water. The microsensor chip was fabricated with Micro‐Electromechanical System technique. Gold nanoparticles were electrodeposited onto the surface of UMEA at a constant potential of ?0.3 V. The ratio d/Rb of interelectrode spacing (d) over the individual electrode’s radius (Rb) was investigated to improve the electrochemical performance. The UMEA with a d/Rb of 20 showed the best hemispherical diffusion mode, resulted in fast response time and high current response. The gold nanoparticles increased the active surface area of UMEA by not changing the geometries of UMEA, and the current response was increased further. Incorporating the optimized characteristic of UMEA and gold nanoparticles, the microsensor showed a good linear range from 0.5 to 200 µg L?1 of copper ions in the acetate buffer solutions with the method of square wave stripping voltammetry. Compared with the gold nanoparticles‐modified disk electrode, the gold nanoparticles‐modified UMEA showed higher sensitivity (0.024 µA mm?2 µg?1 L) and lower limit of detection (0.2 µg L?1). Water samples from river water and tap water were analyzed by the microsensor chip with recovery ranging from 100.7 % to 107.8 %. 相似文献
102.
Curing behaviors of the unsaturated polyester resin (UPR) containing 1–1.8 wt% methyl ethyl ketone peroxide (MEKP) initiator are investigated. The viscosity, gelation and vitrification transition of the UPR-MEKP systems are examined using the rotating viscometer and differential scanning calorimetry (DSC). A liquid fragility parameter, M c, defined as the viscosity variation rate of the liquids towards the curing temperature is presented. It is found that M c has a good negative relation with the glass transition temperature (T g) in the systems. M c can be used for predicting the stability of the cured amorphous systems. The relationship between the liquid and cured thermoset polymer systems is studied from both the thermodynamic and kinetic point of view. 相似文献
103.
Jian Fei Yang Xiu Fang Bian Mei Ling Yuan Yan Wen Bai Yang Liu Jun Peng Fan Xiao Qian Lu Kai Kai Song 《Journal of Sol-Gel Science and Technology》2013,67(2):362-367
The metallic glass/titanium dioxide powders (MG/TiO2) with enhanced photocatalytic oxidation activity were synthesized, which exhibit a higher efficiency in decolorizing methylene blue solutions (MB). Compared with the pure TiO2 and crystalline alloy/TiO2 (CA/TiO2) under the same circumstances, its degradation rate was 60 % and 30 % higher, respectively. Furthermore, compared with the CA/TiO2, the MG/TiO2 photocatalytic rate was three times faster when decolorizing MB. Considering the excellent intrinsic high-performance photocatalytic degradation under visible light irradiation, these novel powders were proven to have potential applications in water purification industry. 相似文献
104.
Yong‐Jun Bian Chao‐Yue Chen Prof. Zhi‐Zhen Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):1129-1133
An efficient palladium‐catalyzed C? H functionalization of aldehydes with various N‐substituted N‐heteroarene‐2‐carboxamides has been developed for the synthesis of secondary imides. The reaction tolerates various functionalities, such as methoxy, fluoro, chloro, and bromo groups. A tentative radical mechanism for a PdII/PdIV catalytic cycle is proposed. 相似文献
105.
Dr. J. Grant Hill Xiaojun Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3620-3628
Benchmark quality geometries and interaction energies for the prereactive halogen‐bonded complexes of dihalogens and ammonia, including hypothetical astatine containing dihalogens, have been produced via explicitly correlated coupled cluster methods. The application of local electron correlation partitioning reveals dispersion, electrostatics and ionic substitutions all contribute significantly to the interaction energy, with a linear relationship between the ionic substitutions and the degree of charge transfer. Potential energy curves for H3N???ClF show that as the relative orientations of the two subunits are manipulated appreciable interactions can be found at considerably angular displaced geometries, signifying lower directionality in halogen bonding than previously supposed. 相似文献
106.
The Landau–Lifshitz equation is analyzed via the inverse scattering method. First, we give the well‐posedness theory for Landau–Lifshitz equation with the frame of inverse scattering method. The generalized Darboux transformation is rigorous considered in the frame of inverse scattering transformation. Finally, we give the high‐order soliton solution formula of Landau–Lifshitz equation and vortex filament equation. 相似文献
107.
Henghui Li Xing Zhao Qiwei Zhang Xiaojun Feng Bi-Feng Liu Xin Liu 《Analytical and bioanalytical chemistry》2014,406(25):6235-6246
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been a major approach for glycan analysis. However, the preferential cleavage of the sialic acid moiety by in- and post-source decay influences the determination of sialylated glycans by MALDI-MS. Many chemical derivatization methods were introduced to stabilize the sialylated glycan during MALDI-MS. Among current derivatization methods, methylamidation is a promising means for simultaneous analysis of natural sialylated glycans regardless of their sialic acid linkage types. Here, a novel derivatization method was developed, in which proteins were conjugated on the solid-phase support in order to stabilize the sialic acids by methylamidation and to reduce sample loss and contamination during the derivatization process. This derivatization strategy was used to investigate N-glycans from fetuin, a glycoprotein containing different types of complex N-glycans. The developed method was also applied to the N-glycan profiling of human serum from patients and healthy volunteers. Results were consistent with N-glycan profiling by HPLC-fluorescence detection. This new method provided a sensitive, simple, and robust approach for profiling glycan structures of complex samples. 相似文献
108.
Zhiwei Men Wenhui Fang Shenghan Wang Zhanlong Li Chenglin Sun Xiaojun Wang 《Journal of Raman spectroscopy : JRS》2015,46(4):388-391
The polarized Raman spectra of the upper part of a thin ice Ih film were obtained in the range of 150 cm−1 to 3800 cm−1. The spectra showed clear polarization dependence; several new peaks were also observed. The longitudinaloptic–tranverseoptic (LO–TO) splitting of the mode near 220 cm−1 in the translational vibration region was experimentally confirmed at 133 K. The Fermi resonance between the bending overtone (around 3270 cm−1) and symmetry stretching fundamental (around 3350 cm−1) in the stretching vibration region appeared at nearly the same temperature. Results showed that ice XI (i.e. proton‐ordered phase of ice Ih) slowly formed in the upper part of a thin ice Ih film without KOH as the temperature gradually decreased below 133 K. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
109.
Chen Kuang Zhang Xiaojun Wang Fei Wu Yitian Zhou Haoxi Zhang Ying Zou Wenbo Zhang Jinming Liu Rong 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(7):2859-2868
Journal of Radioanalytical and Nuclear Chemistry - This study evaluated the potential of Al18F-labelled restrained complexing agent (RESCA)-ICG to assess hepatic function reserve on PET/CT imaging.... 相似文献
110.