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51.
单一阴离子交换柱同时分离有机酸和无机阴阳离子 总被引:8,自引:0,他引:8
研究了用乙二胺四乙酸(EDTA)作淋洗液时,性质迥异的有机酸、无机阴离子和碱土金属离子(Ca^2+、Mg^2+)在同一阴离子交换柱上的同时分离以及保留机理,结果表明,在离子交换机理之外,非离子交换机理对有机酸及钙镁的EDTA络阴郭的保留行为起一定的辅助作用,9种有机酸和无机阴阳离子在10min内得到了较好的分离。各离子的电导检测灵敏度在10^-9至10^-11mol,能满足环境和食吕分析的要求。 相似文献
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The natural abundances of stable nitrogen isotopes in plants and soils have been viewed as recorders that can be used to reconstruct paleoclimate and ecological processes or to indicate the biogeochemical cycle of nitrogen in nature. This study systematically measured the nitrogen isotope composition (δ15N) in plants and surface soils along an altitudinal transect of elevation range of 1200 to 4500 m on the eastern slope of Mount Gongga in southwest China. The influences of photosynthetic pathways on plant δ15N as well as the effects of temperature and precipitation on δ15N altitudinal trends in plants and surface soils are discussed. Across this altitude transect, the δ15N values of C3 and C4 plants on Mount Gongga range between ?9.87‰ and 7.58‰ with a mean value of ?1.33‰, and between ?3.98‰ and 4.38‰ with a mean value of ?0.25‰, respectively. There is an evident δ15N difference between C3 plants and C4 plants. If, however, you only compare C4 plants with those C3 plants growing at the same altitudinal range, no significant difference in δ15N exists between them, suggesting that photosynthetic pathway does not have an influence on the plant δ15N values. In addition, we found that C3, C4 plants and surface soil (0–5 cm depth) all trend significantly towards more negative δ15N with increasing elevation. Furthermore, this study shows that the mean annual temperature and the mean annual precipitation positively and negatively correlate with δ15N in C3 and C4 plants, respectively. This indicates that precipitation and temperature are the main controlling factors of the δ15N variation in plants with altitude. We propose that lower δ15N values of plants and soils at higher altitude should be attributed to lower mineralization and lower net nitrification rates induced by low temperature and abundant rainfall. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
53.
Xiaocheng Qi Svetlana Ignatova Guoan Luo Qionglin Liang Frank Wu Jun Yiming Wang Ian Sutherland 《Journal of chromatography. A》2010,1217(13):1995-2001
Ginseng is a popular herb worldwide and has had varied uses in traditional Asian medicine for thousands of years. There are several different species of the herb, but all share the same constituents. Ginsenosides, the most extensively studied chemical components of ginseng, are generally considered to be one of the most important active ingredients of the plant. In this study, we have developed fast and efficient methodology for isolation of four known ginsenosides Rf, Rd, Re and Rb1 from Ginseng by high performance counter-current chromatography (HPCCC) coupled with evaporative light scattering detection (ELSD). The crude sample for HPCCC was purified firstly from a ginseng extraction using macroporous resin. The enriched saponin fraction (480 mg) was separated by using methylene chloride–methanol–5 mM aqueous ammonium acetate–isopropanol (6:2:4:3, v/v,) as the two-phase solvent system and yielded 10.7 mg of Rf, 11.0 mg of Rd, 13.4 mg of Re and 13.9 mg of Rb1. The purity of these ginsenosides was 99.2%, 88.3%, 93.7% and 91.8%, respectively assessed by HPLC-DAD-ELSD, and their structures were characterized by electrospray ionization mass spectrometry (ESI-MS) and compared with standards. Ammonium acetate was used to shorten the separation time and eliminate emulsification together with a flow step-gradient. The salt can be removed by re-dissolving the sample using acetone. 相似文献
54.
Guoan Liu Lan Ding Chengwen Luo Hong Yang Dongjuan Yang Guixia Liang Lai Wang 《Research on Chemical Intermediates》2006,32(2):145-152
Seven flavonoids were isolated from Eremosparton songoricum (Litv) Vass and their antioxidation actions were examined. To investigate protective ability against DNA damage induced by
H2O2, human peripheral blood mononuclear cells (PBMCs) were incubated with 5-hydroxy-7,4′-dimethoxyflavone,5,7-dihydroxy-3′,4′-dimethoxyflavone,
acacetin, chrysoeriol, pedalitin, flavogadorinin and 5,7,4′-trihydroxy-3′-methoxyflavone-4′-O-D-glucoside separately and then
treated by H2O2. The percentage of damaged cells were determined by single-cell gel electrophoresis. To examine their inhibition of lipid
peroxidation, the compounds were incubated with rat microsomes and the reaction was initiated by Fe2+/Vc. The lipid peroxidation product thiobarbituric acid reactive substances (TBARS) was determined. The result showed most
of flavonoids had concentration-dependent antioxdative activities. The relationship of antioxidation and the structure is
discussed. 相似文献
55.
The utility and versatility of carboxylic single-walled carbon nanotubes (c-SWNT) in capillary electrophoresis (CE) is demonstrated, using as model solutes homologues and structural isomers. In the case of homologues of caffeine and theobromine, distinct changes in the electrophoretic parameters occur at a critical concentration of c-SWNT in the run buffer. It is suggested that the c-SWNT of a definite concentration could form a network in the run buffer as a pseudostationary phase on the basis of the unique tubule structure, providing a different separation from sodium dodecyl sulfate (SDS) micelles. In the case of structural isomers of catechol and hydroquinone, differing from the homologues, it is mainly attributable to the functional groups on the c-SWNT that have an effect on the electrophoretic behaviors by forming intermolecular hydrogen bonding with analytes. Furthermore, aggregated c-SWNT serve as anticonvective media and minimize solute diffusion contributing to zone broadening. The presence of charged c-SWNT suppressed the electrodiffusion and decreased the adsorption between capillary wall and solutes, which led to better peak shapes of isomers. 相似文献
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IntroductionTherearemanystructuresinengineering,whicharenotaxi_symmetric,butcyclicallysymmetric,orcalledrotationallyperiodic,... 相似文献
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