全文获取类型
收费全文 | 5012篇 |
免费 | 388篇 |
国内免费 | 153篇 |
专业分类
化学 | 2028篇 |
晶体学 | 12篇 |
力学 | 1468篇 |
综合类 | 16篇 |
数学 | 469篇 |
物理学 | 1560篇 |
出版年
2024年 | 6篇 |
2023年 | 56篇 |
2022年 | 53篇 |
2021年 | 65篇 |
2020年 | 96篇 |
2019年 | 85篇 |
2018年 | 87篇 |
2017年 | 96篇 |
2016年 | 107篇 |
2015年 | 136篇 |
2014年 | 189篇 |
2013年 | 269篇 |
2012年 | 285篇 |
2011年 | 328篇 |
2010年 | 224篇 |
2009年 | 306篇 |
2008年 | 295篇 |
2007年 | 327篇 |
2006年 | 302篇 |
2005年 | 237篇 |
2004年 | 295篇 |
2003年 | 206篇 |
2002年 | 171篇 |
2001年 | 125篇 |
2000年 | 139篇 |
1999年 | 96篇 |
1998年 | 114篇 |
1997年 | 91篇 |
1996年 | 94篇 |
1995年 | 68篇 |
1994年 | 57篇 |
1993年 | 88篇 |
1992年 | 49篇 |
1991年 | 78篇 |
1990年 | 46篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 35篇 |
1986年 | 31篇 |
1985年 | 38篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有5553条查询结果,搜索用时 46 毫秒
991.
《Analytical letters》2012,45(15):2733-2742
Abstract A simple flow-injection spectrophotometric method for the determination of thioridazine is described. The method is based on the oxidation of thioridazine with phosphotungstic acid in hydrochloric acidic media. Concentrations of thioridazine in the range 10 – 60 ppm are determined with a relative standard deviation of 1.1%. The method was applied to the determination of thioridazine in pharmaceutical formulations. 相似文献
992.
A novel flow injection chemiluminescence (FI‐CL) method for the determination of genistein was described. The method was based on the reaction between genistein and potassium ferricyanide in alkaline solution to give weak CL signal, which was dramatically enhanced by rhodamine 6G (Rh G). The CL emission allowed quantitation of genistein concentration in the range 1.0 × 10?7–4.0 × 10?5 mol/L with a detection limit (3σ) of 4.2 × 10?8 mol/L. The relative standard deviation for 11 parallel measurements of 5.0 × 10?7 mol/L, 4.0 × 10?6 mol/L and 1.0 × 10?5 mol/L genistein were 2.59%, 2.40% and 1.48%, respectively. The experimental conditions for the CL reaction were optimized and the possible reaction mechanism was discussed. The method was applied to the determination of genistein in biological fluids. 相似文献
993.
《Analytical letters》2012,45(15-16):1573-1590
Abstract A direct flow injection flame atomic absorption spectrometry method of determining zinc salt solutions with concentrations of 100's g dm?3 is reported. It was shown that high concentrations of KCl, NaCl and NH4Cl do not significantly interfere with the determination of zinc in both the mg dm?3 and g dm?3 concentration ranges. Where g dm?3 concentrations were determined a secondary spectral line at 307.6 nm was found satisfactory. Galvanizing preflux solutions were analyzed both after dilution to the mg dm?3 range at 213.9 nm and directly injected at 307.6 nm. Precisions of better than 6.6% rsd were observed by the direct method compared with better than 4.8 by dilution techniques. Concentrations up to 110 g dm?3 in zinc were determined the total salt content being greater than 300 g dm?3. 相似文献
994.
《Analytical letters》2012,45(5):385-396
Abstract A very simple flow injection analysis system for direct determination of glucose in blood serum based on Trinder's reaction is described. The sera samples (15 μl) can be injected directly to the system without the deproteinization or the use of a dialyzer. Calibration curves are linear in the range 50–400 mg/dl. The sampling frequency is 60 samples per hour. Results obtained by the proposed procedure are compared with those acquired at a local hospital using their routine glucose procedure also based on Trinder's reaction. It is shown that a better mix between sample and reagents is achieved using the single bead string reactor (SBSR). 相似文献
995.
《Analytical letters》2012,45(7):1729-1742
Abstract A method is proposed for the flow-injection amperometric determination of hydrogen peroxide. Iodine is generated, by injecting hydrogen peroxide solution into an eluent 0.2 M in potassium iodide and 1 Min sulphuric acid and 5×10?3M in Mo(VI) and is monitored at a platinum electrode that is being held at 0.1 V versus SCE. the rectilinearity range is from 10?3?10?6 M and the method is simple, accurate and compared favourably with the titrimetric method involving starch as indicator. 相似文献
996.
《Analytical letters》2012,45(13):2767-2778
ABSTRACT A new flow injection method for the determination of riboflavin based on the inhibition of the intensity of chemiluminescence (CL) from the luminol-K3Fe(CN)6 system is described. While riboflavin mixed with K3Fe(CN)6, by the fast oxidation reaction between riboflavin and K3Fe(CN)6, K4Fe(CN)6 was generated, which then inhibited the CL reaction of K3Fe(CN)6 and luminol in alkaline aqueous solution. The CL emission was correlated with the riboflavin concentration in the range from 0.032 to 100 μg·ml?1, and the detection limit was 0.01 μg·ml?1 (3σ). A complete analysis could be performed in 2 min with a relative standard deviation of less than 2.2%. The influence of foreign species was studied and the method has been applied successfully to the determination of riboflavin in pharmaceutical samples, the recovery was from 98.0% to 102%. 相似文献
997.
998.
《Analytical letters》2012,45(12):2679-2686
Abstract Two equations for justifying whether a FIA peak is a gamma peak or an exponentially modified Gaussian (EMG) peak or neither of them have been presented. From these two equations, the peaks of flow injection extraction and FIA with single-line and two-line manifolds obtained in this paper are gamma peaks. 相似文献
999.
《Analytical letters》2012,45(14):2037-2052
A rapid and simple flow injection (FI) method is reported for the determination of vitamin A (retinol) based on its strong enhancing effect on the Ce(IV)–Na2SO3 chemiluminescence (CL) reaction in an acidic solution. The effect of key chemical and physical parameters (i.e., reagent concentrations, flow rate, and sample volume) was optimized and potential interferences examined. Under the selected experimental conditions, a linear calibration was obtained between the CL intensity and vitamin A concentration in the range 0.1–8.0 µg mL?1 (r 2 = 0.9986, n = 8). The limit of detection (3 s x blank) was 0.01 µg mL?1 retinol (n = 6) and the relative standard deviation (RSD) for 0.25 µg mL?1 retinol was 2.3% (n = 10) with a sampling rate of 180 h?1. The method was successfully applied to infant milk-based formulas and pharmaceutical formulations and the results were not significantly different at 95% confidence interval with those obtained by using a spectrophotometric reference method. The possible CL mechanism is also discussed briefly supporting with UV-visible, fluorescence, and CL spectra. 相似文献
1000.
《Analytical letters》2012,45(14):2026-2036
A novel chemiluminescence (CL) system was established for the determination of diammonium glycyrrhizinate (DG) in pharmaceutical preparations and its ability of scavenging hydroxyl radical. It was shown that a strong CL signal was observed when Eosin Y mixed with Fenton reagent. The CL intensity was decreased significantly when DG was added to the reaction system and partially scavenged the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometrical relationship with DG concentration. Based on this, we developed a new method for the determination of DG using a flow injection chemiluminescence (FI-CL) technique. Under the optimal conditions, the linear range of DG concentration was 6.0 × 10?8–5.0 × 10?6 mol/L (R = 0.9982) with a detection limit of 8.0 × 10?9 mol/L (SN = 3), and the RSD was 3.8% for 2.0 × 10?7 mol/L DG (n = 11). This method was successfully used in the determination of DG in tablets and the evaluation of hydroxyl radical scavenging capacity of DG. The possible reaction mechanism of the CL system is discussed. 相似文献