全文获取类型
收费全文 | 164篇 |
免费 | 2篇 |
专业分类
化学 | 115篇 |
力学 | 9篇 |
数学 | 7篇 |
物理学 | 35篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 14篇 |
2012年 | 2篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 2篇 |
排序方式: 共有166条查询结果,搜索用时 281 毫秒
91.
92.
The reactions of masked ortho-benzoquinones with furan under sonochemical irradiation were studied. Variation of the acoustic energy, temperature, and solvent composition permitted to optimize the yields, and provided insights into the mechanism. While the radical pathway could not be established, a double Michael stepwise pathway seems more probable, as shown by the effect of solvent polarity and the regioselectivity. The sonochemical effect involves most likely a mechanical micromixing, giving evidence to its role even in homogeneous systems. 相似文献
93.
Anna A Herasimtschuk Samantha J Westrop Graeme J Moyle Jocelyn S Downey Nesrina Imami 《Journal of immune based therapies and vaccines》2008,6(1):7
Background
Efficacious immune-based therapy in treated chronic HIV-1 infection requires the induction of virus-specific CD4+ T cells and subsequent maturation and maintenance of specific memory CD8+ T cells. Concomitant daily administration of recombinant human growth hormone (rhGH) with highly active antiretroviral therapy (HAART) was used in chronically infected patients with lipodystrophy in an attempt to reconstitute these virus-specific T-cell responses. 相似文献94.
95.
Homologation of a terminal acetylene to an allene is easily accomplished in a “one-flask” process, via a Mannich base which is transformed to the desired allene by a 1–5 hydrogen shift. 相似文献
96.
A kinetic study of the reduction of nitric oxide (NO) by isobutane in simulated conditions of the reburning zone was carried out in a fused silica jet‐stirred reactor operating at 1 atm, at temperatures ranging from 1100 to 1450 K. In this new series of experiments, the initial mole fraction of NO was 1000 ppm, that of isobutane was 2200 ppm, and the equivalence ratio was varied from 0.75 to 2. It was demonstrated that for a given temperature, the reduction of NO is favored when the temperature is increased and a maximum NO reduction occurs slightly above stoichiometric conditions. The present results generally follow those reported in previous studies of the reduction of NO by C1 to C3 hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (979 reversible reactions and 130 species). An overall reasonable agreement between the present data and the modeling was obtained. Furthermore, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethylene, ethane, acetylene, a natural gas blend (methane‐ethane 10:1), propene, and HCN. According to this study, the main route to NO reduction by isobutane involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: iC4H10 → C3H6 → C2H4 → C2H3 → C2H2 → HCCO; HCCO + NO → HCNO + CO and HCN + CO2; HCNO + H → HCN → NCO → NH; NH + NO → N2 and NH + H → followed by N + NO → N2; NH + NO → N2O followed by N2O + H → N2. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 365–377, 2000 相似文献
97.
Ray L. Frost Sara J. Palmer Jocelyn M. Bouzaid B. Jagannadha Reddy 《Journal of Raman spectroscopy : JRS》2007,38(1):68-77
Raman spectroscopy has been used to study the structure of the humite mineral group ((A2SiO4)n–A(OH, F)2 where n represents the number of olivine and brucite layers in the structure and is 1, 2, 3 or 4 and A2+ is Mg, Mn, Fe or some mix of these cations). The humite group of minerals forms a morphotropic series with the minerals olivine and brucite. The members of the humite group contain layers of the olivine structure that alternate with layers of the brucite‐like sheets. The minerals are characterized by a complex set of bands in the 800–1000 cm−1 region attributed to the stretching vibrations of the olivine (SiO4)4− units. The number of bands in this region is influenced by the number of olivine layers. Characteristic bending modes of the (SiO4)4− units are observed in the 500–650 cm−1 region. The brucite sheets are characterized by the OH stretching vibrations in the 3475–3625 cm−1 wavenumber region. The position of the OH stretching vibrations is determined by the strength of the hydrogen bond formed between the brucite‐like OH units and the olivine silica layer. The number of olivine sheets and not the chemical composition determines the strength of the hydrogen bonds. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
98.
Valérie Brousseau Patrick Caron Jocelyn Trottier Thérèse Di Paolo Piotr Milkiewicz Olivier Barbier 《Journal of mass spectrometry : JMS》2022,57(5):e4827
24S-hydroxycholesterol (i.e., cerebrosterol, 24S-OH-Chol) is the main form of cholesterol elimination from the brain. Liquid chromatography–tandem mass spectrometry methods were developed for the quantification of the total and unesterified/unbound fractions of 24S-OH-Chol, its monosulfate, monoglucuronide, and diconjugate derivatives (24S-OH-Chol-3sulfate [3S], 24S-OH-Chol-24glucuronide [24G] and 24S-OH-Chol-3S, 24G, respectively) in human plasma. Linearity, precision, accuracy, and extraction recovery were validated within the typical physiological and pathological ranges of concentrations for each compound. The lower limit of quantifications was 2.00, 0.33, 0.26, and 0.74 ng/ml for 24S-OH-Chol, 24S-OH-Chol-24G, 24S-OH-Chol-3S, and 24-OH-Chol-3S, 24G, respectively. Extraction recovery values in total and unbound plasma fractions were also analyzed in murine and monkey plasma and varied from 73% in mouse to 113% in cynomolgus monkey. The methods could rapidly (less than 7 min) quantify individual compounds with high sensitivity, accuracy (bias ≤15%), and reproducibility (coefficient of variation [CV] ≤ 17%). Their clinical applications were validated by measuring levels of the 4 compounds in samples from 20 noncholestatic donors, 5 cholestatic patients suffering from primary biliary cirrhosis, and 10 patients suffering from biliary stenosis. Results highlight the abundance of 24S-OH-Chol in the total fraction and the abundance of 24S-OH-Chol-3S and 24G in the unbound ones. While the latter strongly accumulate in plasma fractions of cholestatic patients, levels of 24S-OH-Chol remained similar to those of healthy donors. Our results indicate that this approach is suitable for monitoring cerebrosterol and its conjugates in large-scale clinical studies. 相似文献
99.
Jocelyn S. Paradero-Vilela 《代数通讯》2013,41(7):2495-2505
A torsion-free module is called quasi-regular if each cyclic submodule is a quasi-summand. This article characterizes torsion-free Abelian groups that are quasi-regular as modules over a subring of their endomorphism ring. In particular, if G is a torsion-free Abelian group such that its ring Q E of quasi-endomorphisms is Artinian, then the left E-module G is quasi-regular if and only if the left C-module G is quasi-regular, where C is the center of its endomorphism ring E. 相似文献
100.
Jocelyn L. Prendergast Lorna T. Sniegoski Michael J. Welch Karen W. Phinney 《Analytical and bioanalytical chemistry》2010,397(5):1779-1785
The definitive method (DM), now known as the reference measurement procedure (RMP), for the analysis of glucose in serum was
originally published in 1982 by the National Institute of Standards and Technology (NIST). Over the years the method has been
subject to a number of modifications to adapt to newer technologies and simplify sample preparation. We discuss here an adaptation
of the method associated with serum glucose measurements using a modified isotope dilution gas chromatography/mass spectrometry
(ID-GC/MS) method. NIST has used this modified method to certify the concentrations of glucose in SRM 965b, Glucose in Frozen
Human Serum, and SRM 1950, Metabolites in Human Plasma. Comparison of results from the revised method with certified values
for existing Standard Reference Materials (SRMs) demonstrated that these modifications have not affected the quality of the
measurements, giving both good precision and accuracy, while reducing the sample preparation time by a day and a half. 相似文献