全文获取类型
收费全文 | 963篇 |
免费 | 27篇 |
国内免费 | 100篇 |
专业分类
化学 | 989篇 |
晶体学 | 6篇 |
力学 | 1篇 |
综合类 | 8篇 |
物理学 | 86篇 |
出版年
2023年 | 6篇 |
2022年 | 21篇 |
2021年 | 15篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 34篇 |
2014年 | 48篇 |
2013年 | 78篇 |
2012年 | 102篇 |
2011年 | 59篇 |
2010年 | 50篇 |
2009年 | 63篇 |
2008年 | 74篇 |
2007年 | 66篇 |
2006年 | 54篇 |
2005年 | 47篇 |
2004年 | 45篇 |
2003年 | 44篇 |
2002年 | 29篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1090条查询结果,搜索用时 381 毫秒
41.
The chiral separation of trimetoquinol hydrochloride, which is a bronchodilator (Inolin), and three related compounds by micellar electrokinetic chromatography was investigated using a bile salt as a chiral surfactant. Enantiomers of these compounds, except laudanosoline, were successfully separated within 12 min using a separation tube of effective length 500 mm × 0.05 rum i.d. and a 0.05 M sodium taurodeoxycholate solution of pH 7.0. The observed theoretical plate numbers of the peaks were ca. 150000. Chiral recognition was affected by the structure of bile salts, the pH of the buffer solutions used and the structure of the solutes. Of four kinds of bile salts, successful chiral separation was achieved only using sodium taurodeoxycholate solution under neutral conditions. The method was applied to the optical purity determination of trimetoquinol hydrochloride. The effects of surfactant concentrations and some additives to the micellar solution are briefly described. 相似文献
42.
Summary A rapid and accurate LC method is described for simultaneous determination of pseudoephedrine hydrochloride (PSE), acetaminophen (AMP), dextromethorphen hydrobromide (DEX), and diphenhydramine hydrochloride (DPH) in a compound formulation. Chromatographic separation of the four drugs was achieved on a Hypersil CN column (150 mm × 4.6 mm, 5 m particle) by use of a mobile phase comprising a mixture of 3 mM ion-pairing solution, 2% aqueous triethylamine solution, and 2 M phosphoric acid, 68:48:88 (v/v), pH 3.0, delivered at 1.0 mL min–1. Compounds were detected at 215 nm and the run time was less than 10 min. The linearity, accuracy, and precision of the method were found to be acceptable over the concentration ranges 6.1–36.4 g mL–1 for PSE, 65.0–390.0 g mL–1 for AMP, 3.1–18.6 g mL–1 for DEX, and 5.0–30.0 g mL–1 for DPH. 相似文献
43.
Biju Mathew B. Narayana B. Muralidhara Rao C. H. Raghavan Nambiar B. Ramachandra 《Mikrochimica acta》1996,122(3-4):295-299
A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions 相似文献
44.
45.
Sun Z Zheng X Hoshi T Kashiwagi Y Anzai J Li G 《Analytical and bioanalytical chemistry》2004,380(3):545-550
Ligustrazine is one of the active ingredients contained in Ligusticum chuanxiong Hort. (Umbelliferae), which is widely used in traditional Chinese medicine for the treatment of cardiovascular problems. In this work, the electrochemistry of Ligustrazine hydrochloride (LZC) and its determination are investigated. The detection limit is estimated to be 8.0×10–8 M, with three linear ranges from 1.0×10–6 to 1.0×10–4 M, 1.0×10–4 to 5.0×10–4 M, and 6.5×10–4 to 1.6×10–3 M. The method has been proved to be highly sensitive, selective, and stable, and has been successfully applied to determining LZC in LZC injections. 相似文献
46.
By combining the layer-by-layer (LBL) self-assembly technique with the electrochemical polymerization method, multilayer Ni(II)-polyluminol
films were modified on the surface of a vaseline-impregnated graphite electrode. It was found that, compared with an electrode
modified by direct electrochemical polymerization, this modified electrode offered a suitable ECL reaction micro-environment
created by the special multilayer films, which was beneficial to the ephedrine hydrochloride enhancing effect for luminol
ECL intensity. The ECL enhancing effect of ephedrine hydrochloride on the electro-oxidation luminol was improved on this modified
electrode. Based on this finding, a new sensitive ECL method was developed for ephedrine hydrochloride determination under
the optimal conditions. At the same time, a new idea is proposed for improving the analytical performance of the luminol ECL
system by modifying the ECL reaction micro-environment with the layer-by-layer self- assembly method. Under the optimum experimental
conditions, the ephedrine hydrochloride concentration in the range of 2.0 × 10−8–7.0 × 10−6 mol L−1 was proportional to the enhanced ECL signal, and it offered an 8.0 × 10−9 mol L−1 detection limit for ephedrine hydrochloride. 相似文献
47.
A new sequential injection spectrophotometric method was proposed for the determination of metoclopramide and tetracaine hydrochloride. The method was based on the detection of an unstable red intermediate compound resulting from the reaction of metoclopramide or tetracaine hydrochloride with potassium dichromate, in the presence of sodium oxalate, in sulfuric acid solution. The related reaction mechanisms of this new method have been studied. The experimental conditions were optimized for the stopped-flow and continuous-flow sequential injection models. For continuous flow, the linear range for determination of metoclopramide, the detection limit and the sampling frequency were 13-130 μg ml−1, 9.4 μg ml−1 and 40 samples per hour, respectively. For stopped flow, they were 3-42 μg ml−1, 1.0 μg ml−1 and 18 h−1, respectively. Adopting the continuous-flow model for tetracaine hydrochloride, the linear range was 25-300 μg ml−1, and the detection limit was 18.0 μg ml−1 with sampling frequency of 40 h−1. This method has been used to determine metoclopramide and tetracaine hydrochloride in pharmaceutical preparations, and the results are compared with those determined by the pharmacopoeia method. Statistical analysis reveals that there was no evidence of significant difference between the methods. 相似文献
48.
M. Alcolea Palafox 《光谱学快报》2013,46(8):1395-1415
The infrared and laser Raman spectra (100-4000 cm1) of benzocaine hydrochloride were recorded and its vibrations analysed. A theoretical spectrum with the AM1 semiempirical method was calculated. An infrared study with the temperature was also made. From the experimental data, the torsion and inversion barriers of amine group were calculated. 相似文献
49.
Xiaotian Li Baoluo Wan Tong Yu Linxi Wang Lianqi Hao Maowen Guo 《Biomedical chromatography : BMC》2013,27(12):1595-1602
A reversed‐phase ion pair chromatography method with liquid–liquid extraction analytical method was developed and validated for the determination of antazoline hydrochloride in plasma and excreta of rat. The aim of our study was to characterize the preclinical pharmacokinetics and excretion profiles of antazoline hydrochloride in rats after intravenous injection at the dose of 10 mg/kg. Plasma and excreta samples were extracted with ethyl acetate, and phenacetin was used as the internal standard. The result showed that the method is suitable for the quantification of antazoline hydrochloride in plasma and excreta samples. Analysis of accuracy (90.89–112.33%), imprecision (<7.1%) and recovery (>82.5%) showed adequate values. After a single intravenous administration at 10 mg/kg to rats, plasma concentration profile showed a relative fast elimination proceeding with a terminal elimination half‐life of 3.53 h. Approximately 61.8 and 14.2% of the administered dose were recovered in urine and bile after 72 and 24 h post‐dosing respectively; 5.9% of the administered dose was recovered in feces after 72 h post‐dosing. The above results show that the major elimination route is urinary excretion. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
50.
AHMED Khan MUHAMMAD Asghar MOHAMMED Yaqoob MASOOD Ahmed Siddiqui SAMAR Ali 《高等学校化学研究》2021,37(3):629-638
Asensitive and selective method employing chemiluminescence(CL) coupled with flow injection(FI) is reported for nalbuphine hydrochloride(NAL) assay in pharmaceutical formulations. The enhancement effect of NAL on the CL reaction between tris(2,2'-bipyridyl)ruthenium(II) chloride-diperiodatocuprate(III) {Ru[(bpy)3]2+-Cu(III) complex} in acidic medium is used as analytical measurement. The optimal conditions of the CL reaction were sulfuric acid 1.0×10-3 mol/L, Ru[(bpy)3]2+ 7.5×10-5 mol/L, Cu(III)/Ag(III) complexes 4.0×10-4/5.0×10-4 mol/L, sample loop volume of 120 μL and flow rate of 2.5 mL/min. The sensitivities of the method in terms of detection(S/N=3) and quantification(S/N=10) limits are 5×10-4 and 0.001 ppm(1 ppm=1 mg/L), respectively. The linear response of the instrument in the form of CL intensity with respect to NAL concentration is over the range 0.001-15.0 ppm(R2=0.9999) with relative standard deviation from 0.8% to 3.2% and injection throughput of 120 injection/h. The applications of the method include the quantitative analysis of NAL in pharmaceutical injection samples. Variations and the average results of the proposed method are not signi-ficantly different from the results of a reported method by applying F- and paired student t-test. The most likely CL reaction mechanism is written in accordance with spectrophotometric and CL studies. 相似文献