全文获取类型
收费全文 | 54篇 |
免费 | 7篇 |
国内免费 | 6篇 |
专业分类
化学 | 46篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 6篇 |
物理学 | 11篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1948年 | 3篇 |
排序方式: 共有67条查询结果,搜索用时 0 毫秒
1.
2.
The solubilization of benzo[a]pyrene by organic solvents (dioxane, toluene and dichloromethane) and a surfactant (Triton X-100) was investigated. These media were successfully used for the determination of benzo[a]pyrene using fluorescence detection, with excellent limits of detection and large linear analytical ranges. Benzo[a]pyrene was detected in coal washing waters using liquid chromatography with fluorescence detection. The stability of this compound in dioxane was also examined. 相似文献
3.
MENG Jian REN Yu-Fang LI Xiao-GuangLaboratory of Rare Earth Chemistry Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin ChinaPopov V.V. Repin S.M. Smirnov LA. loffe Physicotechnical Institute Russian Academy of Sciences Saint Petersburg Russia 《中国化学》1994,12(5):419-424
YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC. 相似文献
4.
MARIAN ELBANOWSKI MARIA PAETZ JANUSZ SIAWINSKI LESZEK CIELA 《Photochemistry and photobiology》1988,47(3):463-466
Abstract— Chemiluminescence of the Eu(II)/Eu(III)-adenine nucleotide-H2 O2 system and fluorescence of the Eu(III)-adenosine triphosphate system have been investigated. The spectral distribution of the chemiluminescence emission has shown an occurrence of three main bands (Λ=470–480,590–620 and ca. 700 nm). The energy transfer process from the adenosine triphosphate molecules to the Eu(III) ions has been observed in the fluorescence spectrum. The examined chemiluminescence and fluorescence spectra show that these both kinds of emission originate from the 5 D *** τ7 F*** ( n =1–4) transitions in the Eu(III) ions. 相似文献
5.
Satoka Aoyagi John S. Fletcher Sadia Sheraz Tomoko Kawashima Irma Berrueta Razo Alex Henderson Nicholas P. Lockyer John C. Vickerman 《Analytical and bioanalytical chemistry》2013,405(21):6621-6628
A novel application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) with continuous Ar cluster beams to peptide analysis was investigated. In order to evaluate peptide structures, it is necessary to detect fragment ions related to multiple neighbouring amino acid residues. It is, however, difficult to detect these using conventional ToF-SIMS primary ion beams such as Bi cluster beams. Recently, C60 and Ar cluster ion beams have been introduced to ToF-SIMS as primary ion beams and are expected to generate larger secondary ions than conventional ones. In this study, two sets of model peptides have been studied: (des-Tyr)-Leu-enkephalin and (des-Tyr)-Met-enkephalin (molecular weights are approximately 400 Da), and [Asn1 Val5]-angiotensin II and [Val5]-angiotensin I (molecular weights are approximately 1,000 Da) in order to evaluate the usefulness of the large cluster ion beams for peptide structural analysis. As a result, by using the Ar cluster beams, peptide molecular ions and large fragment ions, which are not easily detected using conventional ToF-SIMS primary ion beams such as Bi3 +, are clearly detected. Since the large fragment ions indicating amino acid sequences of the peptides are detected by the large cluster beams, it is suggested that the Ar cluster and C60 ion beams are useful for peptide structural analysis. 相似文献
6.
针对纤维材料变温环境力学性能测试的需要,在华中科技大学研制的纤维材料试验机的基础上引入了温控装置,从而实现纤维材料在高低温环境下的力学性能测试。采用该装置对不同直径微米铜丝在不同温度、不同拉伸速率条件下的力学性能开展实验研究,测试结果表明弹性模量和抗拉强度随温度的降低而线性增加,屈服强度的变化不太明显。另外,低温环境下微米铜丝的力学性能表现出与其直径相关的尺度效应,而这一现象在常温下一直没有观测到。最后,还研究了拉伸速率对微米铜丝的力学性能影响,结果表明,在现有装置的许用范围之内,拉伸速率对其力学性能的影响不大。 相似文献
7.
Rosa Maria Alonso‐Salces Claude Guillou Luis A. Berrueta 《Rapid communications in mass spectrometry : RCM》2009,23(3):363-383
Liquid chromatography coupled with a photodiode array detector, electrospray ionization, collision‐induced dissociation and tandem mass spectrometry (LC‐DAD/ESI‐CID‐MS/MS) on a triple quadrupole (QqQ) has been used to detect and characterize polyphenols and methylxanthines in green coffee beans: three phenolic acids (caffeic acid, ferulic acid and dimethoxycinnamic acid), three isomeric caffeoylquinic acids (Mr 354), three feruloylquinic acids (Mr 368), one p‐coumaroylquinic acid (Mr 338), three dicaffeoylquinic acids (Mr 516), three feruloyl‐caffeoylquinic acids (Mr 530), four p‐coumaroyl‐caffeoylquinic acids (Mr 500), three diferuloylquinic acids (Mr 544), six dimethoxycinnamoyl‐caffeoylquinic acids (Mr 544), three dimethoxycinnamoyl‐feruloylquinic acids (Mr 558), six cinnamoyl‐amino acid conjugates, three cinnamoyl glycosides, and three methylxanthines (caffeine, theobromine and theophylline). Dimethoxycinnamic acid, three isomers of dimethoxycinnamoyl‐caffeoylquinic acids and another three of dimethoxycinnamoyl‐feruloylquinic acids, as well as the three cinnamoyl glycosides, had not previously been reported in coffee beans. Structures have been assigned on the basis of the complementary information obtained from UV‐visible spectra, relative hydrophobicity, scan mode MS spectra, and fragmentation patterns in MS2 spectra (both in the positive and negative ion modes) obtained using a QqQ at different collision energies. A structure diagnosis scheme is provided for the identification of different isomers of polyphenols and methylxanthines. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
8.
This paper deals with robustness of adaptive control of continuoussystems subject to known output delay, input saturation, unmodelledlinear dynamics, and bounded disturbances. A simple gradient-typealgorithm with a relative deadzone is used. The relative deadzoneis built with an estimated contribution of the unmodelled dynamicsto the system output. The basic tool used for stability androbustness analysis is Gronwall's lemma. 相似文献
9.
电感耦合等离子体-发射光谱法(ICP-AES)快速测定饮用水中8种微量元素 总被引:4,自引:0,他引:4
用电感耦合等离子体-发射光谱法(ICP-AES)同时快速测定饮用水中微量的铜、铅、锌、铁、锰、镉、铬、砷,具有快速、简便、灵敏度高等优点,精密度为1.2%~8.2%(RSD,n=5).回收率为90%~110%. 相似文献
10.
A. Bakkali A. Barranco R. M. Alonso-Salces E. Corta L. A. Berrueta B. Gallo F. Vicente J. I. Márquez 《Chromatographia》1999,49(3-4):202-207
Summary A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC procedure is reported for the
assay of papaverine, diltiazem, desipramine and nicardipine in urine. Disposable extraction cartridges (DECs) filled with
C18, C8, C2, CH and PH silica-bonded phases were used. The effect on recovery of sample pH, composition of washing and elution
solvents and nature of SPE cartridge were evaluated. The selectivity of SPE was examined using spiked urine samples and the
PH cartridge gave rise to the cleanest extracts. Phenyl cartridges were conditioned with methanol and acetic acid-sodium acetate
buffer. Urine sample was buffered and then applied to the DEC. The washing step was with acetone-water and subsequently with
methanol-acetate buffer. The analytes were eluted with methanol-acetate buffer. The extract was evaporated to dryness, reconstituted
in mobile phase, and chromatographed on a reversed-phase C18 column with UV detection at 212 nm. Recoveries of the tested
compounds from spiked urine samples using the PH cartridge were in all cases>80%. The within-day and between-day repeatabilities
were<5% and 9%, respectively. 相似文献