全文获取类型
收费全文 | 963篇 |
免费 | 33篇 |
国内免费 | 2篇 |
专业分类
化学 | 652篇 |
晶体学 | 13篇 |
力学 | 27篇 |
数学 | 124篇 |
物理学 | 182篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 17篇 |
2019年 | 9篇 |
2018年 | 23篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 44篇 |
2014年 | 37篇 |
2013年 | 55篇 |
2012年 | 69篇 |
2011年 | 70篇 |
2010年 | 41篇 |
2009年 | 27篇 |
2008年 | 63篇 |
2007年 | 56篇 |
2006年 | 44篇 |
2005年 | 49篇 |
2004年 | 34篇 |
2003年 | 41篇 |
2002年 | 22篇 |
2001年 | 24篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有998条查询结果,搜索用时 15 毫秒
991.
L. P. Castro S. Saitoh Y. Sawano A. M. Sim?es 《Complex Analysis and Operator Theory》2012,6(1):307-324
In this paper we shall introduce new constructions of approximate solutions of general linear partial differential equations
with constant coefficients on the whole spaces, and establish fundamental estimates of the solutions depending on the inhomogeneous
terms. This will be done by combining general ideas of the Tikhonov regularization and discretization of bounded linear operator
equations on reproducing kernel Hilbert spaces. Furthermore, we will provide approximate solutions for the related inverse
source problems. 相似文献
992.
The effect of dopant cesium (Cs(I)) over a concentration range from 1 to 10 mol% on the growth process, morphology, thermal and optical properties of tri(thiourea)zinc(II) sulfate (ZTS) single crystals grown by slow evaporation solution growth technique has been investigated. Incorporation of Cs(I) into the crystal lattice was well confirmed by energy dispersive X-ray spectroscopy (EDS). The lattice parameters of the as-grown crystals were obtained by single crystal X-ray diffraction analysis. The reduction in the intensities observed in powder X-ray diffraction patterns of doped specimen and slight shifts in vibrational frequencies in fourier transform infrared spectra (FT-IR) indicate the lattice stress as a result of doping. Thermal studies reveal the purity of the material and no decomposition is observed up to the melting point. High transmittance is observed in the visible region and the cut-off λ is ~280 nm. The surface morphology of the as-grown specimens was studied by scanning electron microscopy (SEM). The second harmonic generation (SHG) efficiency of the host crystal is enhanced greatly in the presence of high concentrations of the dopant. 相似文献
993.
We study a gas of N hard disks in a box with semi-periodic boundary conditions. The unperturbed gas is hyperbolic and ergodic (these facts are proved for N=2 and expected to be true for all N≥2). We study various perturbations by twisting the outgoing velocity at collisions with the walls. We show that the dynamics tends to collapse to various stable regimes, however we define the perturbations, and however small they are. 相似文献
994.
M Sanz BF de Simón E Cadahía E Esteruelas AM Muñoz T Hernández I Estrella E Pinto 《Journal of mass spectrometry : JMS》2012,47(7):905-918
The phenolic composition of heartwood extracts from Fraxinus excelsior L. and F. americana L., both before and after toasting in cooperage, was studied using LC-DAD/ESI-MS/MS. Low-molecular weight (LMW) phenolic compounds, secoiridoids, phenylethanoid glycosides, dilignols and oligolignols compounds were detected, and 48 were identified, or tentatively characterized, on the basis of their retention time, UV/Vis and MS spectra, and MS fragmentation patterns. Some LMW phenolic compounds like protocatechuic acid and aldehyde, hydroxytyrosol and tyrosol, were unlike to those for oak wood, while ellagic and gallic acid were not found. The toasting of wood resulted in a progressive increase in lignin degradation products with regard to toasting intensity. The levels of some of these compounds in medium-toasted ash woods were much higher than those normally detected in toasted oak, highlighting vanillin levels, thus a more pronounced vanilla character can be expected when using toasted ash wood in the aging wines. Moreover, in seasoned wood, we found a great variety of phenolic compounds which had not been found in oak wood, especially oleuropein, ligstroside and olivil, along with verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. Toasting mainly provoked their degradation, thus in medium-toasted wood, only four of them were detected. This resulted in a minor differentiation between toasted ash and oak woods. The absence of tannins in ash wood, which are very important in oak wood, is another peculiar characteristic that should be taken into account when considering its use in cooperage. 相似文献
995.
996.
997.
998.
Dr. Phillip M. Danby Andrew Jeong Dr. Lyann Sim Dr. Ryan P. Sweeney Jacob F. Wardman Ryan Karimi Dr. Andreas Geissner Dr. Liam J. Worrall Prof. Dr. Jolene. P. Reid Prof. Dr. Natalie C. J. Strynadka Prof. Dr. Stephen G. Withers 《Angewandte Chemie (International ed. in English)》2023,62(21):e202301258
Suitably configured allyl ethers of unsaturated cyclitols act as substrates of β-glycosidases, reacting via allylic cation transition states. Incorporation of halogens at the vinylic position of these carbasugars, along with an activated leaving group, generates potent inactivators of β-glycosidases. Enzymatic turnover of these halogenated cyclitols (F, Cl, Br) displayed a counter-intuitive trend wherein the most electronegative substituents yielded the most labile pseudo-glycosidic linkages. Structures of complexes with the Sulfolobus β-glucosidase revealed similar enzyme-ligand interactions to those seen in complexes with a 2-fluorosugar inhibitor, the lone exception being displacement of tyrosine 322 from the active site by the halogen. Mutation of Y322 to Y322F largely abolished glycosidase activity, consistent with lost interactions at O5, but minimally affected (7-fold) rates of carbasugar hydrolysis, yielding a more selective enzyme for unsaturated cyclitol ether hydrolysis. 相似文献