全文获取类型
收费全文 | 1110篇 |
免费 | 55篇 |
国内免费 | 6篇 |
专业分类
化学 | 934篇 |
晶体学 | 9篇 |
力学 | 11篇 |
数学 | 116篇 |
物理学 | 101篇 |
出版年
2023年 | 12篇 |
2022年 | 49篇 |
2021年 | 43篇 |
2020年 | 21篇 |
2019年 | 24篇 |
2018年 | 25篇 |
2017年 | 8篇 |
2016年 | 41篇 |
2015年 | 49篇 |
2014年 | 43篇 |
2013年 | 73篇 |
2012年 | 85篇 |
2011年 | 109篇 |
2010年 | 47篇 |
2009年 | 57篇 |
2008年 | 95篇 |
2007年 | 66篇 |
2006年 | 47篇 |
2005年 | 73篇 |
2004年 | 52篇 |
2003年 | 29篇 |
2002年 | 31篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 2篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有1171条查询结果,搜索用时 15 毫秒
121.
Sonia Stita Marta Galera Martínez Huynh Pham Xuan Ange Nzihou Patrick Sharrock 《Composite Interfaces》2013,20(6):503-515
With the expansion of human activities, there are more and more living areas adjacent to industrial and/or agricultural activities such as chemical processes, petroleum processes, paint finishing, food processing, livestock farming, composting plants etc. Bad odor is part of several nuisances caused by industrial and/or agricultural activities. Hydrogen sulfide (H2S) is a typical odorous molecule which causes foul odor at very low concentration. This molecule is formed in different industrial installations, in particular in coal combustion, and petrochemical refinery. The separation and/or transformation of H2S from gas phase to odorless products are important processes for sustainable development. In this paper, we communicate the preparation of new sorbents for the sorption of H2S from a synthetic gas effluent. These sorbents consist in an inorganic phase (hydroxyapatite) as host particles, and well-dispersed particles of a metal oxide as guest particles which are the active phase for the removal of H2S. At room conditions, iron, lead, and zinc doped calcium phosphates were found to be effective for the removal of H2S. The performance of the sorbents depends on preparation method and the nature of active phases. This opens new prospects for the treatment of H2S from gas phase. 相似文献
122.
Sonia Woodbury 《School science and mathematics》1998,98(6):303-311
The National Council of Teachers of Mathematics has proposed a broad core mathematics curriculum for all high school students. One emphasis in that core is on “mathematical connections” both among mathematical topics and between mathematics and other disciplines of study. It is suggested that mathematics should become a more integrated part of all students' high school education. In this article, working definitions for the terms curriculum, interdisciplinary, and integrated and a model of three categories of curriculum design based on the work of Harold Alberty are developed. This article then examines how a “connected” mathematics core curriculum might be situated within the different categories of curriculum organization. Examples from research on interdisciplinary education in high schools are presented. Issues arising from this study suggest the need for a greater emphasis on building and using models of curriculum integration both to frame and to give impetus to the work being done by teachers and administrators. 相似文献
123.
The generation of standard reference frequencies close to the ITU channels is essential for the calibration and maintenance of DWDM systems. This work describes a method to synthesize frequency references in the range from 187.1 to 205.1 THz (1462-1602 nm). The method is based on the generation of four equispaced frequencies (by the process of four-wave mixing in a semiconductor amplifier) of which two are locked to absorption lines of the acetylene 12C2H2 (1511-1542 nm). 相似文献
124.
Sonia Natale 《Algebras and Representation Theory》2002,5(5):445-455
We conclude the classification of Hopf algebras of dimension 12 over an algebraically closed field of characteristic zero. 相似文献
125.
In this work we apply the recently developed first-principles real space linear muffin-tin orbital atomic sphere approximation (RS-LMTO-ASA) scheme to calculate the hyperfine field for 3d impurities (V, Cr, Mn andFe) in Cu. We obtain the Fermi contact term at the impurities andat four shells of host atoms around the impurities. We compare our results with theoretical values obtained using the KKR-Green-function method andwith NMR measurements. The overall agreement is excellent, confirming the reliability of the RS-LMTO-ASA approach as means of obtaining information on hyperfine fields. 相似文献
126.
The57Fe isomer shifts in the crystalline compounds Zr2Fe and Zr3Fe are calculated. We use the standard first-principles linear-muffin-tin-orbital formalism in the atomic sphere approximation (LMTO-ASA) to obtain the electronic structure of the compounds. The electronic structure of pure Fe was also calculated with the same formalism, where the local spin density approximation for the exchange correlation term is used. We found that the calculated isomer shift values are in good agreement with the experimental values for Zr2Fe and Zr3Fe found in the literature. 相似文献
127.
128.
Pickering emulsions with controllable stability 总被引:1,自引:0,他引:1
We prepare solid-stabilized emulsions using paramagnetic particles at an oil/water interface that can undergo macroscopic phase separation upon application of an external magnetic field. A critical field strength is found for which emulsion droplets begin to translate into the continuous-phase fluid. At higher fields, the emulsions destabilize, leading to a fully phase-separated system. This effect is reversible, and long-term stability can be recovered by remixing the components with mechanical agitation. 相似文献
129.
Coriani S Marchesan D Gauss J Hättig C Helgaker T Jørgensen P 《The Journal of chemical physics》2005,123(18):184107
The performance of the standard hierarchy of ab initio models--that is, Hartree-Fock theory, second-order Moller-Plesset theory, coupled-cluster singles-and-doubles theory, and coupled-cluster singles-doubles-approximate-triples theory--in combination with correlation-consistent basis sets is investigated for equilibrium geometries of molecules containing second-row elements. From an analysis on a collection of 31 molecules (yielding statistical samples of 41 bond distances and 13 bond angles), the statistical errors (mean deviation, mean absolute deviation, standard deviation, and maximum absolute deviation) are established at each level of theory. The importance of core correlation is examined by comparing calculations in the frozen-core approximation with calculations where all electrons are correlated. 相似文献
130.
Zingaretti L Mariano Correa N Boscatto L Chiacchiera SM Durantini EN Bertolotti SG Rivarola CR Silber JJ 《Journal of colloid and interface science》2005,286(1):245-252
The distribution of different aliphatic and aromatic amines: n-butylamine (n-BA), isobutylamine (i-BA), tert-butylamine (t-BA), piperidine (PIP), N,N-dimethylaniline (DMA) and N-methylaniline (MA) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate(AOT)/n-hexane reverse micelles was investigated by steady-state fluorescence measurements. The partition constants were measured by an indirect method based on the effect that amine partitioning exert on the bimolecular rate of the reaction between a microphase incorporated fluorophore (Ru(bpy)2+(3)) and the quencher, (Fe(CN)3-(6)). For MA, that can act as a quencher of the fluorophore a direct method was used. The results show that primary amines have larger partition constants than the secondary ones. For tertiary amines the distribution constants were practically negligible. Laser flash photolysis experiments confirmed that tertiary amines, both aliphatic and aromatic, are not incorporated to the micellar pseudophase. The effect of the amine structure on the partition constant was analyzed through linear solvation free energy relationships (LSER) using solute parameters and compared with those obtained for alcohols. Hydrogen bond interactions with the AOT polar heads appear to be the main driving force for the distribution of amines between the organic and micellar pseudophases, whereas the size of the alkyl or aromatic group tends to hinder it. 相似文献