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排序方式: 共有236条查询结果,搜索用时 140 毫秒
31.
Biao Liu Dongxia Yuan Qiaoyue Li Xin Zhou Hao Wu Yihong Bao Hongyun Lu Ting Luo Jinling Wang 《Molecules (Basel, Switzerland)》2021,26(21)
High content of citric acid in lemon juice leads to poor sensory experience. The study aimed to investigate the dynamics changes in organic acids, phenolic compounds, and antioxidant activities of lemon juice fermented with Issatchenkia terricola WJL-G4. The sensory evaluation of fermented lemon juice was conducted as well. Issatchenkia terricola WJL-G4 exhibited a potent capability of reducing the contents of citric acid (from 51.46 ± 0.11 g/L to 8.09 ± 0.05 g/L within 60 h fermentation) and increasing total phenolic level, flavonoid contents, and antioxidant activities compared to those of unfermented lemon juice. A total of 20 bioactive substances, including 10 phenolic acids and 10 flavonoid compounds, were detected both in fermented and unfermented lemon juice. The lemon juice fermented for 48 h had better sensory characteristics. Our findings demonstrated that lemon juice fermented with Issatchenkia terricola exhibited reduced citric acid contents, increased levels of health-promoting phenolic compounds, and enhanced antioxidant activities. 相似文献
32.
采用湿法消解对不同厂区的土壤进行前处理,应用电感耦合等离子体原子发射光谱法(ICP-OES)测定土壤中的金属元素含量,使用原子荧光光谱法AFS测定砷的含量,测定的相对标准偏差为0.8%~3.0%,回收率为89.0%~105.5%。实验表明,方法简单快速、准确,较高的灵敏度和较低的检出限,均能满足土壤中多元素分析的要求。 相似文献
33.
We propose that domain inversion can be directly induced by femtosecond laser both theoretically and experimentally, which opens a path to achieve three-dimensional (3D) nonlinear crystal with a period in sub-micron-scale. A simulation of domain inversion is modeled by considering the temporal distribution of femtosecond pulses. The calculation results clarify that the domain inversions can happen within or after the interaction with the laser pulse, and the response time of domain inversion is in the picosecond level depending on the intensity and the materials. The domain reversal windows of lithium niobate by femtosecond laser are observed which agrees with theoretical predictions qualitatively. 相似文献
34.
A novel method for fabricating protein-MWNT films on pyrolytic graphite (PG) electrodes was described. Positively charged hemoglobin (Hb) or myoglobin (Mb) in buffers at pH 5.5 or 5.0 was first adsorbed on the surface of acid-pretreated, negatively charged multiwalled carbon nanotubes (MWNTs) mainly by electrostatic interaction, forming a core-shell structure. The aqueous dispersion of protein-coated MWNTs was then cast on PG electrodes, forming protein-MWNT films after evaporation of solvent. The protein-MWNT films exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks, characteristic of heme Fe(III)/Fe(II) redox couples. The protein films were characterized by voltammetry, UV-vis spectroscopy, and scanning electron microscopy (SEM). This approach for assembly of protein-MWNT films showed higher surface concentration of electroactive proteins than the simple cast method, and the amount of proteins in the films could be controlled more precisely compared with the dipping method. Furthermore, the film assembly using this method was more stable than that using simple cast method. The proteins in MWNT films retained their near-native structure, and electrochemically catalyzed reduction of oxygen and hydrogen peroxide, suggesting the potential applicability of the films as the new type of biosensors or bioreactors based on direct electrochemistry of enzymes. 相似文献
35.
通过化学键合的方法制备单壁碳纳米管包覆的四氧化三铁(Fe3O4/CNTs)磁性复合纳米粒子。首先用水热法合成磁性Fe3O4纳米粒子,并进行硅烷氨基化处理,羧基化的单壁碳纳米管通过1-(3-二甲基氨基丙基)-3-乙基碳二亚胺(EDC)和N-羟基琥珀酰亚胺(NHS)交联剂反应修饰到Fe3O4纳米颗粒表面。合成的Fe3O4/CNTs复合纳米粒子具有很高的磁响应度和很好的分散能力,是一种很好的分散固相萃取剂。本研究将合成的Fe3O4/CNTs纳米粒子用于分散固相微萃取富集牛奶中的香精添加剂,并与高效液相色谱分析联用,实现了香兰素和乙基香兰素的快速高效富集和高灵敏度检测,两者的检出限达10 μg/L,回收率大于92%。本研究表明,合成的Fe3O4/CNTs磁性复合粒子是一种很好的奶制品中香兰素添加剂的样品前处理富集材料。 相似文献
36.
Min Liu Hongyun Jin Meiying Liu Jie Dong Pan Hou Zhengjia Ji Shuen Hou 《Crystal Research and Technology》2014,49(10):820-828
A composite‐hydroxide mediated (CHM) method was utilized for the synthesis of CuO peony‐flower nanostructures under temperatures ranging between 25 and 160 °C. The CHM mechanism was confirmed through X‐ray Powder Diffraction (XRD) and a Thermo‐Gravimetric Differential Scanning Calorimeter (TG‐DSC). Cu(NO3)2 was shown to transform into Cu(OH)2 in the mixed alkalis (NaOH/KOH); the reaction was facilitated by the solvent properties of the mixed alkalis. Cu(OH)2 subsequently consumed H2O in the adsorption of the mixed alkalis at 25∼65 °C. At higher reaction temperatures (>65 °C), the Cu(OH)2 was seen to decompose at an accelerated rate. Therefore, crystalline CuO could be obtained not only above 65 °C but also at 25 °C. The crystal morphology and structure of CuO were examined through Filed Emission Scanning Electron Microscopy (FE‐SEM) and Transmission Electron Microscopy (TEM). It was determined that the CuO peony‐flower had a polycrystalline structure composed of single crystalline CuO petals. Using the Selected Area Electron Diffraction (SAED) results, the rings were indexed as (002), (111), (112), (202) and (−113), which was in agreement with the XRD results. With increasing temperature, the CuO flower petals self‐assembled through random aggregation and gathered CuO nanorod parts, which led to incomplete CuO flower petals through orientated aggregation. Prolonged reaction time led to the growth of CuO flower petals in the direction of [001]. An ideal CuO flower structure was observed through TEM observation. 相似文献
37.
38.
Superhydrophobic surfaces have shown inspiring applications in microfluidics, and self-cleaning coatings owing to water-repellent and low-friction properties. However, thermodynamic mechanism responsible for contact angle hysteresis (CAH) and free energy barrier (FEB) have not been understood completely yet. In this work, we propose an intuitional 3-dimension (3D) droplet model along with a reasonable thermodynamic approach to gain a thorough insight into the physical nature of CAH. Based on this model, the relationships between radius of three-phase contact line, change in surface free energy (CFE), average or local FEB and contact angle (CA) are established. Moreover, a thorough theoretical consideration is given to explain the experimental phenomena related to the superhydrophobic behavior. The present study can therefore provide some guidances for the practical fabrications of the superhydrophobic surfaces. 相似文献
39.
Hongmei Chai Hongyun Liu Xihong Guo Dong Zheng Yasemin Kutes Bryan D. Huey James F. Rusling Naifei Hu 《Electroanalysis》2012,24(5):1129-1140
Glutathione‐decorated 5 nm gold nanoparticles (AuNPs) and oppositely charged poly(allylamine hydrochloride) (PAH) were assembled into {PAH/AuNP}n films fabricated layer‐by‐layer (LbL) on pyrolytic graphite (PG) electrodes. These AuNP/polyion films utilized the AuNPs as electron hopping relays to achieve direct electron transfer between underlying electrodes and redox proteins on the outer film surface across unprecedented distances >100 nm for the first time. As film thickness increased, voltammetric peak currents for surface myoglobin (Mb) on these films decreased but the electron transfer rate was relatively constant, consistent with a AuNP‐mediated electron hopping mechanism. 相似文献
40.
Ronny Pini Giuseppe Storti Marco Mazzotti Hongyun Tai Kevin M. Shakesheff Steven M. Howdle 《Macromolecular Symposia》2007,259(1):197-202
Summary: The equilibrium sorption and swelling behavior in supercritical CO2 of poly(D,L-lactic acid) and poly(lactic-co-glycolic acid) has been studied at a temperature of 35 °C and at pressures up to 200 bar. Sorption was measured through a gravimetric technique and swelling by visualization. From these data, the behavior of the different polymers can be compared. In terms of partial molar volume of CO2 in the polymer matrix, all the polymers exhibit a behavior typical of rubbery systems. The experimental results have been modeled using the Sanchez-Lacombe equation of state, which is able to represent the actual behavior of the polymer-CO2 systems with reasonable accuracy. 相似文献