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排序方式: 共有825条查询结果,搜索用时 218 毫秒
11.
Summary A method is described for the determination of nitrated polynuclear aromatic hydrocarbons (nitro-PAHs), in particular 1-nitropyrene, in diesel particulate extracts. The method employs a multidimensional HPLC (column switching) technique with final on-line peak identification by UV-VIS spectral comparison with standards. To achieve exceptional chromatographic selectivity for nitro-PAHs, a new pyrene butyric acid amide phase has been prepared which is capable of forming donor-acceptor complexes with them. With this technique it is possible to confirm the presence of 1-nitropyrene in the range 3–100 ng/mg on filter-collected diesel soot. Its utility was demonstrated with diesel exhaust extracts spiked with varying levels of 1-nitropyrene and proved to be highly selective.Parts of this work have been presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984.Dedicated to Prof. J. F. K. Huber at the occasion of his 60th birthday. 相似文献
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13.
A new extraction method for ginsenosides from ginseng roots, ginseng leaves and ginseng drug preparations by Sep-Pak C18 cartridges has been studied. Ginsenoside extraction by Sep-Pak cartridges is a rapid, efficient, reproducible method. In addition, the extracts were analyzed by high performance thin layer chromatography (HPTLC) and reverse phase high performance liquid chromatography (HPLC). The major components of ginseng saponins were effectively separated using an ODS-120T column. 相似文献
14.
Triantafyllos Roukas 《Applied biochemistry and biotechnology》1998,74(1):43-53
The production of citric acid from carob pod extract byA. niger in surface fermentation was investigated. A maximum citric acid concentration (85.5 g/L), citric acid productivity (4.07
g/L/d), specific citric acid production rate (0.18 g/g/d), and specific sugar uptake rate (0.358 g/g/d) was achieved at an
initial sugar concentration of 200 g/L, pH of 6.5, and a temperature of 30°C. Other kinetic parameters, namely, citric acid
yield, biomass yield, specific biomass production rate, and fermentation efficiency were maximum at pH 6.5, temperature 30°C,
and initial sugar concentration 100 g/L. The external addition of methanol into the carob pod extract at a concentration up
to 4% (v/v) improved the production of citric acid. 相似文献
15.
Assessment of various carbon sources and nutrient feeding strategies for Panax ginseng cell culture 总被引:1,自引:0,他引:1
Ginseng (root of Panax ginseng C. A. Meyer) cells were cultivated on medium supplemented with various carbohydrates including sucrose, glucose, and fructose,
at initial concentrations ranging from 10 to 110 g/L. Sucrose was shown to be the superior carbon source to the monosaccharides
for ginseng cell growth and the optimal concentration was between 30 and 50 g/L. An increase in the initial concentration
within this range increased the maximum cell density and growth index significantly, whereas much higher concentrations inhibited
cell growth. Feeding of sucrose and some other medium components during the growth (fed-batch mode) was more effective in
enhancing the cell growth and biomass productivity, increasing the growth index by more than 60–70% and biomass productivity
by more than 50%. 相似文献
16.
Jiang‐Tao Chen Hai‐Zhou Li Dong Wang Ying‐Jun Zhang Chong‐Ren Yang 《Helvetica chimica acta》2006,89(7):1442-1448
Three new dammarane monodesmosides, named notoginsenosides Ft1 ( 1 ), Ft2 ( 2 ), and Ft3 ( 3 ), together with three known ginsenosides, were obtained from a mild acidic hydrolysis of the saponins from notoginseng (Panax notoginseng (Burk .) F. H. Chen ) leaves. Their structures were elucidated to be (3β,12β,20R)‐12,20‐dihydroxydammar‐24‐en‐3‐yl O‐β‐D ‐xylopyranosyl‐(1 → 2)‐O‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranoside ( 1 ), (3β,12β)‐12,20,25‐trihydroxydammaran‐3‐yl O‐β‐D ‐xylopyranosyl‐(1 → 2)‐O‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranoside ( 2 ), and (3β,12β,24ξ)‐12,20,24‐trihydroxydammar‐25‐en‐3‐yl O‐β‐D ‐xylopyranosyl‐(1 → 2)‐O‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranoside ( 3 ), by means of spectroscopic evidences. The known ginsenosides Rh2 and Rg3 4 – 6 were obtained as the major products from this acidic deglycosylation. 相似文献
17.
Maria A. Morosanova Tatyana V. Fedorova Alexandra S. Polyakova Elena I. Morosanova 《Molecules (Basel, Switzerland)》2020,25(24)
In the present work crude Agaricus bisporus extract (ABE) has been prepared and characterized by its tyrosinase activity, protein composition and substrate specificity. The presence of mushroom tyrosinase (PPO3) in ABE has been confirmed using two-dimensional electrophoresis, followed by MALDI TOF/TOF MS-based analysis. GH27 alpha-glucosidases, GH47 alpha-mannosidases, GH20 hexosaminidases, and alkaline phosphatases have been also detected in ABE. ABE substrate specificity has been studied using 19 phenolic compounds: polyphenols (catechol, gallic, caffeic, chlorogenic, and ferulic acids, quercetin, rutin, dihydroquercetin, l-dihydroxyphenylalanine, resorcinol, propyl gallate) and monophenols (l-tyrosine, phenol, p-nitrophenol, o-nitrophenol, guaiacol, o-cresol, m-cresol, p-cresol). The comparison of ABE substrate specificity and affinity to the corresponding parameters of purified A. bisporus tyrosinase has revealed no major differences. The conditions for spectrophotometric determination have been chosen and the analytical procedures for determination of 1.4 × 10−4–1.0 × 10−3 M l-tyrosine, 3.1 × 10−6–1.0 × 10−4 M phenol, 5.4 × 10−5–1.0 × 10−3 M catechol, 8.5 × 10−5–1.0 × 10−3 M caffeic acid, 1.5 × 10−4–7.5 × 10−4 M chlorogenic acid, 6.8 × 10−5–1.0 × 10−3 M l-DOPA have been proposed. The procedures have been applied for the determination of l-tyrosine in food supplements, l-DOPA in synthetic serum, and phenol in waste water from the food manufacturing plant. Thus, we have demonstrated the possibility of using ABE as a substitute for tyrosinase in such analytical applications, as food supplements, medical and environmental analysis. 相似文献
18.
HPLC determination of four active saponins from Panax notoginseng in rat serum and its application to pharmacokinetic studies 总被引:1,自引:0,他引:1
Four main active saponins (ginsenosides Rg1, Rb1, Rd and notoginsenoside R1) in Panax notoginseng in rat serum after oral and intravenous administration of total saponins of P. notoginseng (PNS) to rats were determined using a simple and sensitive high-performance chromatographic method. The serum samples were pretreated with solid-phase extraction before analysis. The calibration curves for the four saponins were linear in the given concentration ranges. The intra-day and inter-day assay coefficients in serum were less than 10.0% and the recoveries of the method were higher than 80.0% in the high, middle and low concentrations. This method was applied to study the pharmacokinetics following oral and intravenous administration of PNS. 相似文献
19.
Green synthesis and characterization of silver nanoparticles by Allium cepa L. to produce silver nano‐coated fabric and their antimicrobial evaluation 下载免费PDF全文
Prashansa Sharma Suman Pant Shambhavi Rai Renu Bala Yadav Swapnil Sharma Vivek Dave 《应用有机金属化学》2018,32(3)
This research work was proposed to study the antimicrobial activity of the silver nanocoated fabric with the purpose of producing good dressing and clothing material. We synthesized simple, ecofriendly, cost‐effective and sustainable silver nanoparticles by using the aqueous extract of Allium cepa L. Here, A. cepa L. acts as a good reducing and capping agent that produced stable silver nanoparticles having particle size of range 36 ± 1 to 98 ± 2 nm, Poly dispersiblity index 0.234 ± 0.61 to 1.023 ± 0.33 and Zeta potential ‐12 ± 1.5 mV to ‐26 ± 1.2 mV. The effect of temperature and extract volume used was considered for optimization of synthetic procedure. The nanocoated fabric was characterized for morphological study, size (using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE‐SEM) and zeta‐potential (Zeta Potentiometer). The presence of functional groups were observed by using attenuated total reflection‐Fourier transform infrared (ATR‐FTIR) and Raman spectroscopy. The crystallinity and structural property of the synthesized silver nanoparticles were studied in terms of Powder X‐ray diffraction (PXRD). An IC50 value and zone of inhibition was studied which demonstrate that the silver nanocoated fabric have an excellent antibacterial property against Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacteria. Further nanocoated fabric material was washed (with function of time 0, 10, 25, and 50 laundry cycles) and still retained their anti‐bacterial activity towards both strain. Initially there was 52 μg/ml of silver nanoparticles on the cotton fabric but after 50 laundry cycle in 500 ml of distilled water the fabric showed 92% efficiency against gram positive and 90% efficacy toward gram negative bacteria. It was found that 4.16 μg/ml nano particles leached in case of S. Aureus and 5.2 μg/mL silver nanoparticles leached in case of E. coli. Nanocoated fabric material synthesized using green synthesis was found to be economical with good resistance to washing. 相似文献
20.
《Analytical letters》2012,45(8):1341-1354
The radix of Panax notoginseng is an important herbal resource for clinics, commercial markets, and the health industry worldwide. The quality of P. notoginseng roots is known to be associated with its cultivation age. This study used 1H-nuclear-magnetic-resonance-spectrometry-based metabolic profiling to characterize P. notoginseng roots. Twenty metabolites—including four ginsenosides—contributed to the composition of P. notoginseng according to age. A partial least-squares regression model using a combined data set from two solvent systems was the best predictor of cultivation age. Finally, receiver-operating-characteristic analysis was used to screen potential markers of P. notoginseng root age. These results may be applied to the development of medicinal and nutraceutical products using P. notoginseng roots. 相似文献