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1.
A highly efficient catalytic system composed of a bifunctional polyacrylonitrile fiber (PANF‐PA[BnBr]) and a metal chloride was employed to produce 5‐hydroxymethylfurfural (HMF) from sucrose in mixed‐aqueous systems. The promoter of PANF‐PA[BnBr] incorporates protonic acid groups that promote the hydrolysis of the glycosidic bond to convert sucrose into glucose and fructose, and then catalyzes fructose dehydration to HMF, while the ammonium moiety may promote synergetically with the metal chloride the isomerization of glucose to fructose and transfer HMF from the aqueous to the organic phase. The detailed characterization by elemental analysis, FTIR spectroscopy, and SEM confirmed the rangeability of the fiber promoter during the modification and utilization processes. Excellent results in terms of high yield (72.8 %) of HMF, superior recyclability (6 cycles) of the process, and effective scale‐up and simple separation procedures of the catalytic system were obtained. Moreover, the prominent features (high strength, good flexibility, etc.) of the fibers are very attractive for fix‐bed reactor.  相似文献   
2.
柳娜  韩鑫  刘娜 《化学教育》2018,39(6):70-73
将1stOpt软件用于物理化学实验蔗糖水解反应速率常数的测定中,在无需严格记录反应开始时间和测定反应终了旋光度的情况下,通过非线性拟合无需编程及公式变换就可以简单方便准确地得到反应速率常数,避免了传统数据处理方法所带来的人为误差,可以补充和改进物理化学实验的教学。  相似文献   
3.
《Analytical letters》2012,45(4):819-829
Abstract

The effects of 9 saccharides on the crystallization of sucrose have been comparatively studied with analytical purposes. A sensitive (detection limit 0.1 μg mL?1) and simple kinetic turbidimetric procedure is used for determination of stachyose, based on its inhibitory action on the crystallization of sucrose. The supersaturated solutions of sucrose were prepared by addition of acetone to stable water sucrose solutions. The induction period of the crystallization process was turbidimetrically measured. Controlled constant stirring and temperature are convenient in order to obtain reproducible results. The method was applied to the determination of stachyose in synthetic mixtures.  相似文献   
4.
Abstract

Differential scanning calorimetric investigations have been conducted on sucrose solutions for temperatures T<?100°C and in the sucrose concentration range 74 < c < 97. A novel method is adopted for sample preparation. For c > 92, the room temperature phase is amorphous, as indicated by its x-ray diffraction pattern. A melting transition is reported for the first time for these concentrations. A second-order phase transition is recorded for T < 0°C, which is clearly observed only during heating cycles, indicating a continuous phase transition during cooling. These transitions have not been reported so far, suggesting that the phase formed due to the procedure adopted for sample preparation may be different from that reported in the literature.  相似文献   
5.
建立了一种测定蓝藻细胞培养液中蔗糖和甘油葡糖苷的高效阴离子交换色谱积分脉冲安培检测法。在最佳的分离条件下,蔗糖和甘油葡糖苷的质量浓度在0.1~50.0 mg/L范围内与色谱峰面积线性良好,线性相关系数r20.999 9。蔗糖和甘油葡糖苷的最低检测限分别是0.15 mg/L和0.03 mg/L,测定结果的相对标准偏差小于2%(n=8)。该方法样品处理简单,无基体干扰,测定的准确度,灵敏度高,可应用于蓝藻培养液中蔗糖和甘油葡糖苷的测定。  相似文献   
6.
Spectroscopic Fourier self-deconvolution analysis was used to investigate β-sheet features in the secondary structure of hemoglobin under mobile phone microwaves at 900 MHz. To this end, four samples of hemoglobin in bidistilled water, sucrose, trehalose, and sodium chloride aqueous solutions were exposed for up to 4 hr to 900 MHz microwaves at an average H-field intensity of 42 mA/m. Quantitative spectral analyses highlighted significant increases in β-sheet contents in the Amide I region of hemoglobin samples in bidistilled water solution, but no appreciable change was observed in hemoglobin samples in sucrose, trehalose, and sodium chloride solutions. These results led us to conclude that mobile phone microwaves can denaturate hemoglobin in bidistilled water solution whereas sucrose, trehalose, and sodium chloride solutions produce a protective effect against microwaves, preserving the protein from unfolding.  相似文献   
7.
Polyphenols display a number of interesting properties but their low solubility limits practical applications. In that respect, glycosylation offers a solution for which sucrose phosphorylase has been proposed as a cost‐effective biocatalyst. However, its activity on alternative acceptor substrates is too low for synthetic purposes and typically requires the addition of organic (co‐)solvents. Here, we describe the engineering of the enzyme from Thermoanaerobacterium thermosaccharolyticum to enable glycosylation of resveratrol as test case. Based on docking and modeling studies, an active‐site loop was predicted to hinder binding. Indeed, the unbolted loop variant R134A showed useful affinity for resveratrol (Km=185 mM ) and could be used for the quantitative production of resveratrol 3‐α‐glucoside in an aqueous system. Improved activity was also shown for other acceptors, introducing variant R134A as promising new biocatalyst for glycosylation reactions on bulky phenolic acceptors.  相似文献   
8.
Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific δ18O analysis has been commercially available for more than a decade, this method has been hardly applied so far. Here we present the first GC-Py-IRMS δ18O results for trimethylsilyl-derivatives of plant sap-relevant sugars and a polyalcohol (glucose, fructose, sucrose, raffinose and pinitol). Particularly, we focus on sucrose, which is assimilated in leaves and which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and paleoclimate studies. Replication measurements of sucrose standards and concentration series indicate that the GC-Py-IRMS δ18O measurements are not stable over time and that they are amount (area) dependent. We, therefore, suggest running sample batch replication measurements in alternation with standard concentration series of reference material. This allows for carrying out (i) a drift correction, (ii) a calibration against reference material and (iii) an amount (area) correction. Tests with 18O-enriched water do not provide any evidence for oxygen isotope exchange reactions affecting sucrose and raffinose. We present the first application of GC-Py-IRMS δ18O analysis for sucrose from needle extract (soluble carbohydrate) samples. The obtained δ18Osucrose/ Vienna Standard Mean Ocean Water (VSMOW) values are more positive and vary in a wider range (32.1–40.1 ‰) than the δ18Obulk/ VSMOW values (24.6–27.2 ‰). Furthermore, they are shown to depend on the climate parameters maximum day temperature, relative air humidity and cloud cover. These findings suggest that δ18Osucrose of the investigated needles very sensitively reflects the climatically controlled evaporative 18O enrichment of leaf water and thus highlights the great potential of GC-Py-IRMS δ18Osucrose analysis for plant physiology and paleoclimate studies.  相似文献   
9.
离子色谱脉冲安培法测定蜂蜜中的葡萄糖、果糖、蔗糖   总被引:11,自引:0,他引:11  
利用离子色谱脉冲安培检测器对蜂蜜中葡萄糖、果糖、蔗糖的测定方法进行了研究。采用CARBOPAC^TM PAl分离柱和脉冲安培检测器,对淋洗分离条件进行了实验,选择50mmol/L NaOH作淋洗液,可使蜂蜜中的葡萄糖、果糖、蔗糖很好地分离。检出限分别为:葡萄糖2μg/kg,果糖2μg/kg,蔗糖5μg/kg。加标回收率为90%-108%。该方法只需简单的前处理、无基体干扰,分离效果好,测定准确率高,适用于蜂蜜中葡萄糖、果糖、蔗糖的测定。  相似文献   
10.
利用差示扫描量热仪用经过退火处理的连续扫描法、不经过退火处理的连续扫描法和分步扫描法,对20%和50%蔗糖水溶液的玻璃化转变温度进行了测量。结果显示,退火处理的连续扫描法测量结果最好,测得蔗糖水溶液的玻璃化转变温度大致为-34.6℃,Tg'不受退火温度和溶液浓度的影响。三种方法测得20%蔗糖水溶液的Tg'的差别不大。退火方法和不退火方法测得50%蔗糖水溶液的Tg'差别很大。用两种不同的连续扫描方法做了几组测新鲜西瓜汁玻璃化转变温度的实验,结果在-42--44℃之间。  相似文献   
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