全文获取类型
收费全文 | 2062篇 |
免费 | 73篇 |
国内免费 | 18篇 |
专业分类
化学 | 1396篇 |
晶体学 | 5篇 |
力学 | 69篇 |
数学 | 429篇 |
物理学 | 254篇 |
出版年
2022年 | 15篇 |
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 35篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 47篇 |
2015年 | 55篇 |
2014年 | 45篇 |
2013年 | 139篇 |
2012年 | 117篇 |
2011年 | 115篇 |
2010年 | 89篇 |
2009年 | 70篇 |
2008年 | 117篇 |
2007年 | 119篇 |
2006年 | 106篇 |
2005年 | 95篇 |
2004年 | 116篇 |
2003年 | 93篇 |
2002年 | 94篇 |
2001年 | 37篇 |
2000年 | 35篇 |
1999年 | 24篇 |
1998年 | 29篇 |
1997年 | 21篇 |
1996年 | 44篇 |
1995年 | 24篇 |
1994年 | 27篇 |
1993年 | 15篇 |
1992年 | 24篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 26篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 20篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1974年 | 14篇 |
1973年 | 18篇 |
排序方式: 共有2153条查询结果,搜索用时 15 毫秒
81.
82.
83.
The knowledge of atomic fundamental parameters, such as mass attenuation coefficients or fluorescence yields with low uncertainties, is of decisive importance in elemental quantification involving X-ray fluorescence analysis techniques. Several databases providing the mass attenuation coefficients are accessible and frequently used within a large community of users. These compilations are most often in good agreement for photon energies in the hard X-ray ranges. However, they significantly differ for low photon energies and around the absorption edges of the elements. Mass attenuation coefficients of several elements were determined experimentally in the photon energy range from 100 eV to 35 keV by using monochromatized radiation at the SOLEIL synchrotron (France). The application of high-accuracy experimental techniques resulted in low uncertainty mass attenuation coefficients. The results are compared with tabulated data. 相似文献
84.
Yogesh Patil George Zapsas Yves Gnanou Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):163-171
This study presents the synthesis and properties of linear PVDF-based amphiphilic triblock terpolymers with PS and PEO, [PVDF-b-PS-b-PEO], by adopting a procedure that involves: (a) iodine-transfer polymerization (ITP) of VDF with 1-iodoperfluorohexane (C6F13I) serving as chain-transfer agent (CTA) to afford C6F13-PVDF-I, (b) ITP of styrene with the C6F13-PVDF-I macromolecular-CTA to obtain C6F13-PVDF-b-PS-I diblock copolymer, (c) end-group exchange from iodo- to azido-group by nucleophilic substitution reaction with NaN3, and (d) copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-terminated PEO to achieve C6F13-PVDF-b-PS-b-PEO triblock terpolymers. The 1H and 19F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self-assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α-phase into α + β-phases and β + γ-phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 163–171 相似文献
85.
Carmine Coluccini Yoke Mooi Ng Yves Ira A. Reyes Hsin-Yi Tiffany Chen Yit Lung Khung 《Molecules (Basel, Switzerland)》2020,25(22)
In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host–guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform. 相似文献
86.
Alexandra Botz Yves Chenavier Jacques Pécaut Pascale Delangle Christelle Gateau 《Tetrahedron letters》2018,59(26):2550-2553
The synthesis of several thiazonaphthalimide derivatives is described. The exclusive formation of angular rather than linear isomers was unequivocally demonstrated by NMR and single crystal X-ray diffraction. Their photophysical properties and ability to bind calf-Thymus DNA with affinities in the range of 104 makes them interesting candidates to probe DNA by fluorescence. 相似文献
87.
Yves Pomeau 《Comptes Rendus Mecanique》2018,346(3):184-197
The equations for a self-similar solution to an inviscid incompressible fluid are mapped into an integral equation that hopefully can be solved by iteration. It is argued that the exponents of the similarity are ruled by Kelvin's theorem of conservation of circulation. The end result is an iteration with a nonlinear term entering a kernel given by a 3D integral for a swirling flow, likely within reach of present-day computational power. Because of the slow decay of the similarity solution at large distances, its kinetic energy diverges, and some mathematical results excluding non-trivial solutions of the Euler equations in the self-similar case do not apply. 相似文献
88.
Let X be a 1-connected CW-complex of finite type and ε?(X) be the group of homotopy classes of self-equivalences of X which induce the identity on homotopy groups. In this paper, we prove that every finitely generated 2-solvable rational nilpotent group is realizable as ε?(X) where X is the rationalization of a 1-connected CW-complex of finite type. 相似文献
89.
Yves Fé lix Jean-Claude Thomas 《Proceedings of the American Mathematical Society》2004,132(1):305-312
Let be a simply-connected closed oriented -dimensional manifold. We prove that for any field of coefficients there exists a natural homomorphism of commutative graded algebras where is the loop algebra defined by Chas and Sullivan. As usual denotes the monoid of self-equivalences homotopic to the identity, and the space of based loops. When is of characteristic zero, yields isomorphisms where denotes the Hodge decomposition on .
90.