全文获取类型
收费全文 | 394篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 274篇 |
晶体学 | 28篇 |
力学 | 11篇 |
数学 | 43篇 |
物理学 | 45篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 29篇 |
2010年 | 31篇 |
2009年 | 28篇 |
2008年 | 40篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 29篇 |
2004年 | 22篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 4篇 |
1991年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有401条查询结果,搜索用时 234 毫秒
71.
72.
Canan Kazak Muhittin Aygün Günseli Turgut Mustafa Odabao
lu Süheyla
zbey Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):1044-1045
The molecular structure of the title compound, C11H9NOS, has three planar moieties, two of which are rings, namely the hydroxyphenyl and the thiophene, with an angle of 20.76 (10)° between them. The crystal structure is stabilized by an O—H?N hydrogen bond and by C—H?O intermolecular interactions. The C?O intermolecular contact distance is 3.443 (2) Å. 相似文献
73.
Mixed convection heat transfer about a semi-infinite inclined plate in the presence of magneto and thermal radiation effects
is studied. The fluid is assumed to be incompressible and dense. The nonlinear coupled parabolic partial differential equations
governing the flow are transformed into the non-similar boundary layer equations, which are then solved numerically using
the Keller box method. The effects of the mixed convection parameter R
i, the angle of inclination α, the magnetic parameter M and the radiation–conduction parameter R
d on the velocity and temperature profiles as well as on the local skin friction and local heat transfer parameters. For some
specific values of the governing parameters, the results are compared with those available in the literature and a fairly
good agreement is obtained. 相似文献
74.
In this study, thermally developing laminar forced convection in a pipe including viscous dissipation and wall conductance
is investigated numerically. The constant heat flux is assumed to be imposed at the outer surface of the pipe wall. The finite
volume method is used. The distributions for the developing temperature and local Nusselt number in the entrance region are
obtained. The dependence of the results on the Brinkman number and the dimensionless thermal conductivity are shown. The viscous
heating effect on the wall is shown. Significant viscous dissipation effects have been observed for large Br. 相似文献
75.
Dinçer Ülkü Leyla Tatar Orhan Atakol Mecit Aksu 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(3):273-274
In the title linear trinuclear compound, [Zn{Zn(CH3COO)(C17H16N2O2)}2], the central Zn2+ ion, which is located on an inversion centre, has a distorted octahedral coordination involving four bridging O atoms from two N,N′-bis(salicylidene)-1,3-propanediaminate ligands in the equatorial plane and one O atom from each bridging acetate group in the axial positions. The coordination around the terminal Zn2+ ion is irregular square pyramidal, with two O and two N atoms of the ligand in the basal plane and one O atom from an acetate group in the apical position. The acetate bridges linking the central and terminal Zn2+ ions are mutually trans. The Zn⃛Zn distance is 3.0520 (8) Å. The relationship of this structure to that of [Zn{Cu(CH3COO)(C17H16N2O2)}2] is discussed. 相似文献
76.
Tahir SAVRAN Abdurrahman KARAG
Z ükriye Nihan KARUK ELMAS Duygu AYDIN Furkan
ZEN Kenan KORAN Fatma Nur ARSLAN Ahmet Orhan G
RGÜLÜ brahim YILMAZ 《Turkish Journal of Chemistry》2020,44(4):1148
A fluorogenic probe based on a coumarin-derivative for Cu2+ sensing in CH3CN/H2O media (v/v, 95/5, 5.0 μM) was developed and applied in real samples. 3-(4-chlorophenyl)-6,7-dihydroxy-coumarin (MCPC) probe was obtained by synthetic methodologies and identified by spectral techniques. The probe MCPC showed remarkable changes with a “turn-off” fluorogenic sensing approach for the monitoring of Cu2+ at 456 nm under an excitation wavelength of 366 nm. The response time of the probe MCPC was founded as only 1 min. The detection limit of the probe MCPC was recorded to be 1.47 nM. The binding constant and possible stoichiometric ratio (1:1) values were determined by Benesi-Hildebrand and Job’s plot systems, respectively. The mechanism of the probe MCPC with Cu2+ was further confirmed by ESI-MS and FT-IR analyses, as well as supported by theoretical calculations. Furthermore, the probe MCPC was successfully employed for the practical applications to sense Cu2+ in different herbal and black tea samples. The proposed sensing method was also verified by ICP-OES method. 相似文献
77.
Orhan ?çelli Salih Erzeneogˇlu 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,97(1):34-40
Ncoh/NComp and NKβ/NKα intensity ratios of scattered photons by Zn in the linear region and the infinite mass thickness region are measured as functions of the pressure used for compressing the pellets with a Si(Li) detector using Am-241 and Fe-55 annular source. Besides, the effect on the experimental intensity ratio of relation between two different thicknesses of sample with applied different pressures on the sample is investigated in this study. Harmony between the linear and infinitive (critical) thickness region and the applied pressure on the sample has directly affected the experimental intensity ratios. Experimental results were not compared with various theoretical values in the literature, for present results constitute the first experimental measurements. 相似文献
78.
In the present paper we prove a Korovkin type approximation theorem for a sequence of positive linear operators acting from
a weighted space Cρ1 into a weighted space Bρ2 with the use of a matrix summability method which includes both convergence and almost convergence. We also study the rates
of convergence of these operators. 相似文献
79.
Experimental and simulated data for adsorption of gas mixtures on energetically heterogeneous surfaces like activated carbon and zeolites exhibit negative deviations from ideality. The deviations are large in some cases, with activity coefficients at infinite dilution equal to 0.1 or less. Similar molecules form ideal mixtures, but molecules of different size or polarity are nonideal. Equations for bulk liquid mixtures (Wilson, Margules, etc.) do not apply to isobars for adsorbed mixtures. A two-constant equation for activity coefficients as a function of composition and spreading pressure is in good agreement with theory, simulation, and experiment. 相似文献
80.
Erkan Yilmaz Yıldız Tut Orhan Turkoglu Mustafa Soylak 《Journal of the Iranian Chemical Society》2018,15(8):1721-1731
In this study, Pd nanoparticle-modified magnetic Sm2O3–ZrO2 material (Pd–Fe3O4–Sm2O3–ZrO2) as multifunctional catalyst was fabricated and used for catalytic reduction of 2-nitrophenol compound, degradation of methylene blue and rhodamine B dyes, which are toxic pollutants. The magnetic material was used for the first time as a catalyst for the reduction and degradation studies. Pd nanoparticle-modified magnetic Sm2O3–ZrO2 catalyst was prepared using the deposition–precipitation methods and were characterized by X-ray diffraction, scanning electron microscopy, atomic absorption spectrometry, Raman spectroscopy and BET surface analyzer. The Pd nanoparticle-modified magnetic Sm2O3–ZrO2 material can lead to high catalytic activity for the reduction of 2-nitrophenol and degradation of rhodamine B and methylene blue with >?95% conversion within ~?2 and 80 s even when the content of Pd in it is as low as 5.8 wt%. 相似文献