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71.
Adam J. McShane Yuanyuan Shen Mary Joan Castillo Xudong Yao 《Journal of the American Society for Mass Spectrometry》2014,25(10):1694-1704
Direct reductive methylation of peptides is a common method for quantitative proteomics. It is an active derivatization technique; with participation of the dimethylamino group, the derivatized peptides preferentially release intense a1 ions. The advantageous generation of a1 ions for quantitative proteomic profiling, however, is not desirable for targeted proteomic quantitation using multiple reaction monitoring mass spectrometry; this mass spectrometric method prefers the derivatizing group to stay with the intact peptide ions and multiple fragments as passive mass tags. This work investigated collisional fragmentation of peptides whose amine groups were derivatized with five linear ω-dimethylamino acids, from 2-(dimethylamino)-acetic acid to 6-(dimethylamino)-hexanoic acid. Tandem mass spectra of the derivatized tryptic peptides revealed different preferential breakdown pathways. Together with energy resolved mass spectrometry, it was found that shutting down the active participation of the terminal dimethylamino group in fragmentation of derivatized peptides is possible. However, it took a separation of five methylene groups between the terminal dimethylamino group and the amide formed upon peptide derivatization. For the first time, the gas-phase fragmentation of peptides derivatized with linear ω-dimethylamino acids of systematically increasing alkyl chain lengths is reported. Figure
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72.
互穿网络型二阶非线性光学极化聚合物 总被引:5,自引:0,他引:5
报导了二阶非线性光学材料含对硝基苯偶氮苯烷基胺发色基团的聚氨酯和聚丙烯酸酯的互窗网络聚合物的合成和极化工艺,考察了微观形态,用电致色变法测定了其极化膜发色基团的取向度及取向的热稳定性,其二阶非线性光学系数x^(2)可达10^-7esu量级。该互穿网络聚合物极化膜有良好的光学性质和优异的热稳定性,在120℃温度下序参数可长期保持稳定。 相似文献
73.
Dong Wenming Wang Xiangke Shen Yi Zhao Xudong Tao Zuyi 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(2):431-434
The factors affecting the sorption of radiocobalt by bentonite and kaolinite were studied with the aim to assess important factors which should be included in modelling radiocobalt migration in soils and waters. The distribution coefficients of radiocobalt sorption on bentonite and kaolinite from aqueous solutions were determined by using the batch method, and it was found that they were insensitive to the loading, the initial pH, the ionic strength, the humic substance and the sorption direction. Thus, the sorption characteristics of radiocobalt on bentonite and kaolinite facilitated the mathematical modelling of radiocobalt migration. In addition, the sorption kinetics and the sorption mechanism of radiocobalt on bentonite and kaolinite were also examined. 相似文献
74.
Xudong Zhang Caihong Ying Shanyu Quan Guimei Shi Zhijie Li 《Solid State Communications》2012,152(11):955-959
An investigation on the structural, phonon, elastic and thermodynamic properties of the Si0.5Sn0.5 cubic alloy has been conducted using the norm-conserving pseudopotentials within the local density approximation in the frame of the density functional theory (DFT) and the density functional perturbation theory (DFPT) in the ABINIT code. Our results demonstrate that the Si0.5Sn0.5 cubic alloy in the zinc-blende phase keeps dynamically stable until 8 GPa. The elastic constants and thermodynamic quantities as a function of pressure and/or temperature are also presented. 相似文献
75.
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77.
A one‐step strategy for aliphatic poly(carbonate‐ester)s with high performance derived from CO2, propylene oxide and l‐lactide 下载免费PDF全文
To improve the performance of PPC, aliphatic poly(carbonate‐ester)s were prepared in one‐step strategy from the terpolymerization of CO2, propylene oxide (PO), and l ‐lactide (L ‐LA) catalyzed by zinc glutarate. Consequently giving high‐molecular weight terpolymers (PPCLAs) in a very high yield (8450.8–9435.8 g mol?1 of Zn). The resulting terpolymers PPCLAs were characterized by 1H NMR, showing that PPCLAs had an almost alternating structure for the components of CO2, PO, and L‐LA. The influence of molecular weight and L‐LA content on the properties of PPCLAs was also investigated. Differential scanning calorimetry and thermogravimetric analysis (measurements revealed that the glass transition temperature (T g) and thermal decomposition temperature (T d) of PPCLAs are all much higher than those of PPC and increased with increasing molecular weight and L‐LA content. Tensile tests showed that the high mechanical properties of PPCLAs are due to the introduction of L‐LA into the copolymerization of CO2 and PO. Furthermore, PPCLA4 exhibits high degradability, and after 10 weeks, the weight loss increases up to 6.58%, which is significantly higher than that of PPC of 4.58%. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
78.
Li Cui Fengjuan Xu Jun Jiang E. Sun Zhenhai Zhang Xudong Cheng Jing Wang Xiaobin Jia 《Chromatographia》2014,77(17-18):1223-1234
Herba Epimedii (Epimedium) is a kind of tonic herb, widely used in China. Epimedin A is a major component of Herba Epimedii with bioactivities. Analysis of the metabolic profile in vivo plays a pivotal role in understanding how traditional Chinese medicine works. And the metabolites of epimedin A might influence the effects of Herba Epimedii. Moreover, the metabolic routes of epimedin A provide an important basis for safety evaluation. Until now, little has been known about the metabolism of epimedin A. The current study was designed to characterize the metabolic pathways of epimedin A in vivo. The metabolites in rat plasma, bile, feces, and urine were identified by UPLC/Q–TOF–MS analysis. A total of 27 metabolites from epimedin A were detected or tentatively identified. The major metabolic processes were hydrolysis, hydrogenation, hydroxylation, dehydrogenation, demethylation, and conjugation with glucuronic acid and different sugars. The present study revealed the metabolic pathways of epimedin A in rat for the first time, and epimedin A could undergo extensive phase I and phase II metabolism in rat. These findings would provide an important basis for the further study and clinical application of epimedin A. In addition, the results of this work have shown the feasibility of the UPLC/Q–TOF–MS approach for rapid and reliable characterization of metabolites. 相似文献
79.
Weiwei Huang Xudong Yu Hai Lin Huakuan Lin 《Journal of inclusion phenomena and macrocyclic chemistry》2011,69(1-2):69-73
A colorimetric anion sensor 1 based on 3-phthaloyl-N-4-nitrophenylhydrozone was synthesized and characterized. The binding ability evaluated by UV?Cvis experiment reveals that 1 can selectively recognize fluoride. Further insights into the nature of interactions between sensor 1 and anions were investigated by H NMR titrations experiments. In addition, the color changes induced by fluoride can provide a way of detection by ??naked-eye??. 相似文献
80.
We report rapid, sensitive, and direct detection of 2,4-dinitrotoluene (DNT) vapor using tailored gold nanoparticles (Au-NPs) as the SERS substrate. The Au-NPs were synthesized using the UV-assisted photo-chemical reduction method and subsequently formed a monolayer on the glass slide through polymer-mediated self-assembly. The SERS substrate such prepared has high SERS enhancement, high affinity towards DNT vapor, and rapid response to the DNT adsorption/desorption. We systematically studied the effect of the Au-NP size and surface density on the SERS performance such as enhancement factor and response time. With the optimized SERS substrate, an enhancement factor over 5.6 × 10(6) was achieved. Furthermore, real-time detection of DNT vapor with only 0.35 second data acquisition time was demonstrated using a 12 mW laser. Compared to previously reported results, we achieved two orders of magnitude reduction in detection time and more than one order of magnitude reduction in excitation laser power. The detection limit is estimated to be 0.4 attogram, which corresponds to a sub-ppb DNT concentration in air. This work will lead to the development of ultra-fast and ultra-sensitive SERS devices for explosive identification and monitoring. 相似文献