全文获取类型
收费全文 | 994篇 |
免费 | 10篇 |
国内免费 | 56篇 |
专业分类
化学 | 854篇 |
力学 | 1篇 |
综合类 | 3篇 |
数学 | 8篇 |
物理学 | 194篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 41篇 |
2012年 | 132篇 |
2011年 | 41篇 |
2010年 | 32篇 |
2009年 | 58篇 |
2008年 | 52篇 |
2007年 | 69篇 |
2006年 | 64篇 |
2005年 | 68篇 |
2004年 | 43篇 |
2003年 | 37篇 |
2002年 | 32篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 30篇 |
1998年 | 44篇 |
1997年 | 18篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 16篇 |
1991年 | 28篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有1060条查询结果,搜索用时 15 毫秒
181.
182.
化妆品中2种限用呫吨染料的高效液相色谱检测 总被引:1,自引:0,他引:1
建立了化妆品种中2种限用呫吨染料酸性黄73和溶剂橙16的高效液相色谱/二极管阵列检测器检测方法。在ODS C18反相色谱柱上,流动相为0.1 mol/L乙酸铵-甲醇-乙腈(体积比为65:17.5:17.5)等度洗脱,检测波长为492 nm,柱温35℃,流速1.0 mL/min。以保留时间定性,外标法定量。在5~500μg/mL范围内,酸性黄73和溶剂橙16的质量浓度与各自相应的峰面积呈现良好的线性关系,仪器检出限均为0.5μg/mL。样品前处理方法采用甲醇作溶剂超声提取,酸性黄73和溶剂橙16的加标回收率分别在91.2%~106.2%和93.2%~101.5%范围内。 相似文献
183.
184.
Ultrathin crystalline CdSe nanosheets have been synthesized through a facile solution processes. Their application to simultaneous electrochemical determination of catechol and hydroquinone is demonstrated. The few-layer single crystalline CdSe modified electrode exhibits strong electrocatalytic activity toward the oxidation of a mixture of catechol and hydroquinone. The excellent analytical performance makes the ultrathin CdSe nanomaterials promising for the development of electrochemical sensors for potential applications in medicine, biotechnology and environmental chemistry. 相似文献
185.
The paper presents a novel method for the flotation separation of Bi3+ using microcrystalline adsorption system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTMAB), various salts and acidity etc. on the flotation yield of Bi3+ have been investigated to select the optimum experimental conditions. The possible flotation separation mechanism of Bi3+ was discussed. The results showed that under the optimum conditions, dodecyl trimethyl ammonium bromide cation (DTMAB+ ) reacted with I? to produce themicrocrystalline matter (Ms‐M) of (DTMAB+·I?), the water‐insoluble ternary association complex of (DTMAB)3[BiI6] which produced by Bi3+ and I?, DTMAB+ was quantificationally adsorbed on the surface of Ms‐M of (DTMAB+·I?) and was floated above water phase, the liquid‐solid phases were formed with clear interface. In this condition, K+, Na+, Ca2+, Mg2+, Co2+, Ni2+, Mn2+, Zn2+, Fe2+ and Al3+ could not be floated. Therefore, Bi3+ was separated completely from the above metal ions. A new method for flotation separation and determination of bismuth using microcrystalline adsorption system was established. The proposed method has been successfully applied to the determination of Bi3+ in bismuthiferous drug samples, and the results agreed well with those obtained by pharmacopoeia method. The recoveries were 94.1%~106.8%, and the RSD was 1.5%~2.3%. 相似文献
186.
187.
《Analytical letters》2012,45(1-3):340-348
A flow injection spectrophotometric procedure with symmetric merging zones for dipyrone determination in pharmaceutical formulations is proposed. The determination is based on the formation of a blue complex (monitored at a wavelength of 642 nm) yield in the complexation reaction of dipyrone with Fe(III) in acid medium. Under optimum conditions, a calibration curve was obtained from 3.5 to 281 mg L?1 with a detection limit of 2.8 mg L?1 and the samples throughput was 80 h?1. The analytical results obtained for commercial formulation samples by applying the proposed method were in good agreement with labeled values and those obtained by a comparative procedure at a 95% confidence level. 相似文献
188.
《Analytical letters》2012,45(15):2755-2760
Abstract The preparation of cellulose tribenzoate (CTB) chiral stationary phases coated on a small-particle (5 μ m, 120A°) spherical silica support, according to a process that is reported, is presented. The products of asymmetric hydroesterification of norbornene are resolved on the cellulose tribenzoate chiral stationary phases. 相似文献
189.
《Analytical letters》2012,45(17-18):1449-1464
Abstract Spectrophotometric Method for the Rapid Determination of Microgram Amounts of Ethionamide A simple and sensitive method for the determination of microgram amounts of ethionamide is described. Ethionamide is converted to corresponding 2-ethyl-γ-pyridyl thiohydroxamic acid which gives a purple violet colour (Λmax 510 nm) with ferric chloride in acidic medium. This forms the basis for the quantitative determination of ethionamide in its pure form and in tablet form. The influence of substrates, commonly employed as excipients, is studied. An attempt has been made to determine ethionamide in the presence of other antitubercular drugs. 相似文献
190.
《Analytical letters》2012,45(2):228-242
Abstract A new luminescence method based on the minocycline (MNC)-europium (Eu3+)-sodium dodecylbenzene sulfonate (SDBS) system was developed for the determination of MNC. SDBS formed a ternary complex with MNC-Eu3+ and significantly enhanced the luminescence intensity of Eu3+. The enhanced luminescence intensity showed a good linear relationship with the concentration of MNC over the range of 4.0 × 10?7 ~ 1.0 × 10?5 mol L?1 with a detection limit of 2.0 × 10?8 mol L?1. This method is rapid and sensitive, and has been successfully applied for the determination of MNC in capsules and human urine/serum samples. The luminescence mechanism is also studied. 相似文献