全文获取类型
收费全文 | 177篇 |
免费 | 9篇 |
国内免费 | 9篇 |
专业分类
化学 | 141篇 |
综合类 | 7篇 |
数学 | 2篇 |
物理学 | 45篇 |
出版年
2023年 | 4篇 |
2022年 | 26篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 3篇 |
2015年 | 10篇 |
2014年 | 2篇 |
2013年 | 15篇 |
2012年 | 5篇 |
2011年 | 1篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 2篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有195条查询结果,搜索用时 31 毫秒
41.
42.
43.
在不含有机模板剂体系(OSDAs)中,利用异相晶种(T型分子筛)诱导快速合成出纯相的低硅菱沸石分子筛。采用XRD、SEM、TEM、27Al MAS NMR和紫外拉曼等手段表征分子筛的结构属性和形貌特点。详细研究了菱沸石分子筛的晶化过程以及晶种添加量、nAl2O3/nSi O2、nH2O/nSiO2和碱度对菱沸石分子筛晶化的影响,并探讨T型分子筛晶种诱导合成菱沸石分子筛的晶化机理。原位合成体系中仅形成L型分子筛晶相,而一定量T型分子筛异相晶种的加入诱导溶胶快速制备出纯相的菱沸石分子筛。T型分子筛晶体在一定的水热条件下不断溶解而释放的六元环(6R)和四元环(4R)迅速形成菱沸石分子筛特征笼(CHA笼),抑制了L型分子筛特征单元和特征笼(不含四元环的CAN笼)的形成。 相似文献
44.
Dr. Chaoran Li Shumin Zhang Dr. Bingchang Zhang Dr. Jingjing Liu Weihu Zhang Prof. Alexander A. Solovev Prof. Rujun Tang Dr. Feng Bao Jia Yu Prof. Qiao Zhang Prof. Yeshayahu Lifshitz Prof. Le He Prof. Xiaohong Zhang 《Angewandte Chemie (International ed. in English)》2018,57(14):3772-3776
Site‐selective growth on non‐spherical seeds provides an indispensable route to hierarchical complex nanostructures that are interesting for diverse applications. However, this has only been achieved through epitaxial growth, which is restricted to crystalline materials with similar crystal structures and physicochemical properties. A non‐epitaxial growth strategy is reported for hierarchical nanostructures, where site‐selective growth is controlled by the curvature of non‐spherical seeds. This strategy is effective for site‐selective growth of silica nanorods from non‐spherical seeds of different shapes and materials, such as α‐Fe2O3, NaYF4, and ZnO. This growth strategy is not limited by the stringent requirements of epitaxy and is thus a versatile general method suitable for the preparation of hierarchical nanostructures with controlled morphologies and compositions to open up a verity of applications in self‐assembly, nanorobotics, catalysis, electronics, and biotechnology. 相似文献
45.
D. T. Asilbekova 《Chemistry of Natural Compounds》2003,39(6):528-530
The composition of free and bound lipids from Capsicum annuum (Solanaceae) seeds was studied. Glycolipids, phospholipids, mono- and diacylglycerides, and free fatty acids were observed in the bound lipids. 相似文献
46.
M.K.-K. Figueiredo G.A. Romeiro R.N. Damasceno 《Journal of Analytical and Applied Pyrolysis》2009,86(1):53-57
The low temperature conversion (LTC) process applied to a castor seed sample at 380 °C produced pyrolysis oil (50%, w/w), pyrolytic char (29%, w/w), water (13%, w/w) and gas (8%, w/w) fractions. The oil fraction was subjected to analysis of by FTIR, 1H NMR, 13C NMR, GCMS and physical–chemical analysis such as sulfur content, distillation, density, flash-point, kinematic viscosity, Ramsbottom carbon residue, ash content, corrosivity to copper, water content and sediment, cold filter plugging point, and gross calorific value. 相似文献
47.
Summary TS-1 with relatively small crystal sizes (0.4-1.5 μm) was synthesized using inorganic sources of Ti and Si. The effects of
conditions in the preparation of seeds on the synthesized zeolites were studied. 相似文献
48.
《Arabian Journal of Chemistry》2022,15(8):103985
This study aimed to investigate the effect of pumpkin (Cucurbita maxima) seed supplementation on the anthropometric measurements, biochemical parameters, and blood pressure (BP) of Indian women with metabolic syndrome (MetS). Initially, in vitro antioxidant activities of pumpkin seeds extract were assessed using standard methods. In vitro alpha-amylase, alpha-glucosidase, and dipeptidyl peptidase IV (DPP-IV) inhibition effects, along with glucose uptake assay using 3T3-L1 cell lines were performed to determine the antidiabetic effects of the seeds extract. Fatty acids and phytoconstituents were identified using gas chromatography-mass spectrometry (GC–MS). Indian women aged 30–50 years, having MetS were assigned either to intervention (n = 21) or control (n = 21) group on a random basis. Participants in the intervention group received 5 g of pumpkin seeds for 60 days. Participants in both intervention and control were advised to follow certain dietary guidelines throughout the study. Pumpkin seeds extract exhibited not only strong reducing power but also scavenged DPPH and ABTS●+ free radicals with low IC50 values. Pumpkin seeds inhibited alpha-amylase, alpha-glucosidase, and DPP-IV enzymes at varying concentrations with IC50 values of 138, 22, and 246 µg/mL, respectively. Furthermore, glucose uptake was enhanced by 213% at 300 ng/mL on the 3T3-L1 cell line. GC–MS analysis showed the presence of propyl piperidine, flavone, oleic acid, and methyl esters of fatty acids in the seed extract. On comparing the changes in mean reduction/ increment in the anthropometric measurements as well as biochemical parameters and BP between the groups, significant difference (P = 0.012) was observed only for fasting plasma glucose. Findings of the present study highlight the role of pumpkin seeds as a cost-effective adjunct in treating MetS. 相似文献
49.
Serge Kokot 《中国化学快报》2010,21(2):213-216
<正>High performance liquid chromatographic(HPLC) fingerprints of Cassia seed,a traditional Chinese medicine(TCM),were developed by means of the chromatograms at two wavelengths of 238 and 282 nm.Then,the two data sets were combined into one matrix.The application of principal component analysis(PCA) for this data matrix showed that the samples were clustered into four groups in accordance with the plant sources and preparation procedures.Furthermore,partial least squares(PLS),back propagation artificial neural network(BP-ANN),and radial basis function artificial neural network(RBF-ANN) were effectively applied to predict the category of the four different samples in the test set. 相似文献
50.
A. Kamangerpour M. Ashraf-Khorassani L. T. Taylor H. M. McNair L. Chorida 《Chromatographia》2002,55(7-8):417-421
Summary Supercritical Fluid Chromatography with a packed column on a mixture of eight polyphenols has been optimized. Carbon dioxide
which was modified with methanol which contained less than 1% (w/w) citric acid as a secondary additive served as the mobile
phase. Two tandem diol columns were used sequentially. The optimized method was applied to a supercritical fluid grape seed
extract. Various components in the extract could be identified by retention time and ultraviolet spectral comparison with
our synthetic mixture of polyphenols. 相似文献