全文获取类型
收费全文 | 1173篇 |
免费 | 46篇 |
国内免费 | 4篇 |
专业分类
化学 | 722篇 |
晶体学 | 9篇 |
力学 | 22篇 |
数学 | 166篇 |
物理学 | 304篇 |
出版年
2023年 | 10篇 |
2022年 | 45篇 |
2021年 | 37篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 26篇 |
2017年 | 24篇 |
2016年 | 50篇 |
2015年 | 30篇 |
2014年 | 39篇 |
2013年 | 64篇 |
2012年 | 78篇 |
2011年 | 79篇 |
2010年 | 65篇 |
2009年 | 46篇 |
2008年 | 63篇 |
2007年 | 63篇 |
2006年 | 56篇 |
2005年 | 56篇 |
2004年 | 36篇 |
2003年 | 34篇 |
2002年 | 24篇 |
2001年 | 25篇 |
2000年 | 25篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有1223条查询结果,搜索用时 15 毫秒
981.
Esther Neyrolles José Lara Cruz Georgio Bassil François Contamine Pierre Cezac Philippe Arpentinier 《国际化学动力学杂志》2020,52(5):329-340
The sequestration of carbon dioxide fumes from oxyfuel combustion is used to reduce significantly the carbon dioxide emissions from coal-fired power plants. Impurities like nitric oxide, present in the fumes, can cause technical difficulties during the capture, the treatment, the transport, and the storage steps of the CO2 fumes. The purpose of this study is to better understand the oxidation of nitric oxide under pressure in the presence of carbon dioxide and in the experimental condition of flue gas treatment. This reaction is known to be a third-order reaction, two order in nitric oxide and first order in oxygen. To examine the effect of the temperature, the pressure and the volume fraction of oxygen on the rate constant of oxidation, k1, an autoclave is used. The first experiment studies the influence of the temperature between 288 and 323 K. The results found are in the form of an Arrhenius-type equation: k1 = 810 exp(620/T) and are in agreement with the literature. Carbon dioxide does not seem to have an influence on the rate constant, whereas our experimental measurements indicate an influence of the volume fraction of oxygen. The rate constant decreases when the oxygen volume fraction increases by up to 10%. Then the rate constant remains constant. This observation allows us to conclude that the mechanism involving the mechanism with a dimer of NO as an intermediate is more likely to be the mechanism involved in the nitric oxide oxidation in our experimental conditions: high pressure and ambient temperature. The rate constant k2, k–2, and k3 were also estimated in these conditions. 相似文献
982.
Luís Cruz Nuno Basílio Johan Mendoza Nuno Mateus Victor de Freitas Maun H. Tawara Juan Correa Eduardo Fernandez-Megia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(50):11696-11706
The interaction of two anthocyanins with a water-soluble polyanionic dendrimer was studied through UV/Vis, stopped-flow, and NMR spectroscopy. Cyanidin-3-glucoside (cy3glc) revealed a stronger interaction than malvidin-3-glucoside (mv3glc) at pH 1 according to their apparent association constants. A higher color increased was also obtained for cy3glc at pH 3.5 as a result of this stronger interaction. A high-frequency chemical shift of the cy3glc aromatic protons suggest the formation of ionic pairs. The interaction parameters (K≈700 m −1, n≈295) indicated the binding of approximately two anthocyanin molecules by each sulfate group. The equilibrium and rate constants of cy3glc in the presence of dendrimer showed an increased stability of the flavylium cation and a higher protection of this species from hydration (pK′a and pKh increased almost one pH unit). The tuning and color stabilization of anthocyanins by using this dendrimer allow novel applications as colorimetric sensors for food packaging. 相似文献
983.
Li Cruz Y. Chen Zengshun Tse Tim K. T. Weerasuriya Asiri U. Zhang Xuelin Fu Yunfei Lin Xisheng 《Nonlinear dynamics》2022,107(4):3683-3707
Nonlinear Dynamics - Scientific research and engineering practice often require the modeling and decomposition of nonlinear systems. The dynamic mode decomposition (DMD) is a novel Koopman-based... 相似文献
984.
Suhas Balasaheb Mitkari Alberto Medina-Ortíz Dr. José Luis Olivares-Romero Dr. Miguel A. Vázquez Dr. Eduardo Peña-Cabrera Dr. Clarisa Villegas Gómez Dr. David Cruz Cruz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):618-621
An aminocatalytic privileged diversity-oriented synthesis (ApDOS) strategy utilizing trienamine catalysis for the construction of diverse and complex thiopyrans-piperidone fused rings through a thia-Diels–Alder/nucleophilic ring-closing sequence by using dithioamides as activated heterodienophiles is reported. Following this strategy, a super cascade reaction to assemble nine fused rings can be achieved by employing a bis-dithioamide. Additionally, by linking an indole moiety on the dithioamide, a Pictet–Spengler type reaction can be promoted once the cascade sequence has been achieved, leading to more complex penta- hexa- and heptacyclic fused ring derivatives in a one-pot process. This investigation opens new perspectives for the synthesis of a new class of complex and diverse thiopyrans that contribute to populate new relevant regions in the chemical space. 相似文献
985.
Cruz Guillermo J. Ordóñez-Regil Eduardo Almazán-Torres María Guadalupe 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(2):421-426
Journal of Radioanalytical and Nuclear Chemistry - Alpha emitters in Mexican Pacific beach sands were studied to calculate the 234U/238U activity ratio (AR) and the 239+240Pu content. AR was... 相似文献
986.
Arboviruses, such as chikungunya, dengue, yellow fever, and zika, caused by the bite of the Aedes aegypti mosquito, have been a frequent public health problem, with a high incidence of outbreaks in tropical and subtropical countries. These diseases are easily confused with a flu-like illness and present very similar symptoms, difficult to distinguish, and treat appropriately. The effects that these infections cause in the organism are fundamentally derived from complex metabolic processes. A prominent area of science that investigates the changes in the metabolism of complex organisms is the metabolomics. Metabolomics measures the metabolites produced or altered in biological organisms, through the use of robust analytical platforms, such as separation techniques hyphenated with mass spectrometry, combined with bioinformatics. This review article presents an overview of the basic concepts of metabolomics workflow and advances in this field, and compiles research articles that use this omic approach to study these arboviruses. In this context, the metabolomics is applied to search new therapies, understand the viral replication mechanisms, and access the host-virus interactions. 相似文献
987.
Reyna-Cavazos K. A. la Cruz A. Martínez-de Contreras David Longoria-Rodríguez F. E. 《Research on Chemical Intermediates》2022,48(3):949-967
Research on Chemical Intermediates - BiOI samples were synthesized by coprecipitation method in glycerol medium at 100 °C followed by a thermal treatment of the precursor powders at... 相似文献
988.
989.
Usefulness of parallel factor analysis to handle the matrix effect in the fluorescence determination of tetracycline in whey milk 总被引:2,自引:0,他引:2
The determination of tetracycline by fluorescence spectrophotometry in complex matrices has some difficulties, because the presence of other compounds in the matrix affects the analytical signal. In this work, the effect of some inorganic species that are present in whey milk on the fluorescence signal of tetracycline is studied using a D-optimal experimental design. Next, an experimental strategy is proposed in conjunction with Parallel Factor Analysis, PARAFAC, modeling that leads to suitably modeling the severe matrix effect in the determination of tetracycline in whey milk. A specific design is performed in such a way that the lack of trilinearity due to the effect of the presence of interferents on the signal is obviated. Then, ten test samples from three brands of milk, spiked with different quantities of tetracycline and measured in 2 days were analysed using this methodology (mean of the absolute value of the relative errors: 5.1%). The developed analytical method fulfils the property of trueness, the relative errors being, both in calibration and prediction, inside the interval set by Commission Decision 2002/657/EC at these concentration levels. Decision limits (CCα) at x0 = 0 μg L−1 and at x0 = 100 μg L−1 were 13.2 and 112.4 μg L−1 respectively, for α = 0.05; whereas detection capabilities (CCβ) were 25.9 μg L−1 and 124.4 μg L−1 respectively for α = β = 0.05. 相似文献
990.
Nelson F. Martínez Estela Lladosa MªCruz Burguet Juan B. Montón Marlen Yazimon 《Fluid Phase Equilibria》2009
Isobaric vapour–liquid equilibrium (VLE) measurements for the binary systems 4-methyl-2-pentanone + 1-butanol and 4-methyl-2-pentanone + 2-butanol are reported at 20 and 101.3 kPa. The system 4-methyl-2-pentanone + 1-butanol presents a minimum boiling point azeotrope at both pressures (20 and 101.3 kPa) and the system 4-methyl-2-pentanone + 2-butanol presents only a minimum boiling azeotrope at 20 kPa. In both systems, which deviate positively from ideal behaviour, the azeotropic composition is strongly dependent on pressure. The activity coefficients and boiling points of the solutions were correlated with its composition by the Wilson, UNIQUAC, and NRTL models for which the parameters are reported. 相似文献