全文获取类型
收费全文 | 166篇 |
免费 | 48篇 |
国内免费 | 6篇 |
专业分类
化学 | 100篇 |
晶体学 | 1篇 |
力学 | 1篇 |
综合类 | 8篇 |
数学 | 1篇 |
物理学 | 109篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 12篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2012年 | 16篇 |
2011年 | 24篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 15 毫秒
61.
A. Bacaloni S. Insogna A. Sancini M. Ciarrocca F. Sinibaldi 《Biomedical chromatography : BMC》2013,27(8):987-993
In order to monitor biogenic amines in human urine, a method based on field‐amplified sample injection combined with capillary electrophoresis and direct UV absorption detection was developed. Dopamine, tyramine, tryptamine, serotonin and epinephrine were effectively separated and identified in human urine samples, and detection limits were 0.072, 0.010, 0.027, 0.010 and 0.120 µmol/L, respectively. Detection limits comparable to laser‐induced fluorescence detection or solid phase extraction combined with capillary electrophoresis were achieved. Parameters affecting electrophoretic system detection sensitivity were investigated. Optimal separation conditions were obtained using as background electrolyte a pH 6.5 mixture of 2‐(morpholino)ethanesulfonic acid 20 mmol/L and 30 mmol/L phosphate buffer, containing 0.05% hydroxypropylcellulose and 10% v/v methanol. Injections of the sample solution were performed by applying a voltage of 12 kV for 50 s. Recovery and accuracy ranged between 89.4 and 94.9%, and 89 and 112%, respectively. The method was successfully applied on actual urine samples (from a healthy volunteer): target bioamine content was consistent with endogenous levels reported in the literature. The proposed method is simple, fast and inexpensive and can be conveniently employed in work‐related stress studies. The affordability and noninvasive sampling of the method allow epidemiological studies on large number of exposed persons to be performed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
62.
We discuss the conditions required for an optimal SASE FEL operation when bunch compression techniques are exploited to enhance the bunch peak current. We discuss the case of velocity bunching and magnetic bunch compression. With reference to the latter technique we provide a quantitative estimate of the amount of laser heater power necessary to suppress the micro-bunching instability without creating any problem to the SASE dynamics. 相似文献
63.
64.
65.
An on-line sample stacking method, namely field-amplified sample injection, has been developed for the separation and determination of carnosine, anserine, and homocarnosine by capillary electrophoresis. Using electrokinetic injection, about 130- to 160-fold improvement of sensitivity was achieved without loss of separation efficiency when compared to conventional sample injection. For conventional injection, the samples were dissolved in running buffer and then hydrodynamically injected for 10 s (3.45 kPa). Various parameters affecting separation and sample stacking were optimized. Under optimum conditions, linear responses were obtained over two orders of magnitude and the detection limits (defined as S/N = 3) of carnosine, anserine, and homocarnosine were 1.5 x 10(-8) to 1.6 x 10(-8) mol/L. 相似文献
66.
After comparing with electrokinetic injection (EKI) and transient isotachophoresis (t-ITP), the principles of electrokinetic supercharging (EKS) were introduced. Thereafter, the advances and applications of EKS in capillary electrophoresis were intorduced in the following aspects: EKI setups, t-ITP setups, capillary electrophoresis (CE) separation, and real sample analysis. The factors that limit its application are discussed, and the future development of EKS is also prospected. 相似文献
67.
Xianyu Fan Ji Li Shengyuan Wu Jingjing Jiang Jiajing Wang Shuowen Wang Yuefen Lou Guorong Fan 《Journal of separation science》2020,43(17):3555-3564
This article describes a method for the simultaneous quantitation of risperidone and its major metabolite, 9‐hydroxyrisperidone, in beagle dog plasma by field‐amplified sample injection in capillary zone electrophoresis. The separation was carried out at 25°C in a 48 cm × 75 µm fused‐silica capillary with an applied voltage of 20 kV using 60 mM NaH2PO4 buffer (pH 3.6). The detection wavelength was 280 nm. Clean‐up and preconcentration of plasma samples were conducted by 96‐well formatted liquid‐liquid extraction. In this study, this stacking technique provided a sensitivity enhancement of approximately 158 to 188 fold compared with the same sample without stacking. The method was suitably validated with respect to stability, specificity, linearity, lower limit of quantitation, accuracy, precision, and extraction recovery. Calibration curves exhibited good linearity (r2 > 0.995) over a wide concentration range of 2.5 to 200 ng/mL for both risperidone and 9‐hydroxyrisperidone. The intra‐ and interday precisions at the three quality control levels were less than 11.40%. The intra‐ and interday accuracies ranged from 87.90 to 107.17% for risperidone and from 88.43 to 105.92% for 9‐hydroxyrisperidone. All validation data were within the required limits. In conclusion, the method developed was successfully applied to pharmacokinetic studies of risperidone and 9‐hydroxyrisperidone in beagle dogs. 相似文献
68.
69.
自从在以 8-羟基喹啉铝 (Alq)掺杂小分子激光染料 DCM为激活介质的波导结构中 [1] ,光泵浦下观察到激光现象以来 ,这种以高效发光有机半导体材料代替以往的溶胶、凝胶或透明聚合物材料来稀释激光染料的方法 ,引起了人们广泛的关注和巨大的兴趣。因为 Alq的发射谱和 DCM的激发谱有很大的重叠 ,所以经光泵浦后的 Alq∶ DCM薄膜中处于激发态的 Alq分子很容易与附近的 DCM分子形成能量迁移[1] ,从而其发射谱表现为 DCM的荧光谱 ,而不是 Alq和 DCM的荧光谱的简单叠加。由于材料的发射谱相对于激发谱红移很大 ,所以很大程度上降低了材料… 相似文献
70.
Chaoqun Wang Prof. Rui Liu Jianyu Hu Prof. Yi Lv 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12270-12274
DNA walking machines opened new avenues for the biosensing and demonstrated great success in the past few years. Since DNA machines are mainly nonequilibrium systems driven by dynamic interactions, the matrix effects on DNA machines is a bottleneck and more intricate than common DNA-mediated assays, especially for complicated physiological samples. Herein, to realize an accurate and reliable quantitative machine, a ratiometric DNA walking machine was developed in human serums and cell lysates based on the elemental isotope ratio measurement. The target DNA-triggered walking machine converted and amplified biological signals into mass spectrometric signal ratios (197Au/115In) via a burnt-bridge mechanism. Under the optimized conditions, the limit of detection (LOD, 3σ) was 8 fM for target DNA, with a dynamic linear range of 0.05–0.7 pM. The ratiometric DNA walking machine was directly applied in human serum samples with satisfactory recoveries of 94 to 105 %, demonstrating an excellent stability and a high accuracy. Combining the aptamer-based specific recognition, the proposed DNA machine is expected to be a versatile platform for other targets, such as small biomolecules and proteins. 相似文献