全文获取类型
收费全文 | 697篇 |
免费 | 67篇 |
国内免费 | 2篇 |
专业分类
化学 | 625篇 |
力学 | 14篇 |
数学 | 59篇 |
物理学 | 68篇 |
出版年
2023年 | 13篇 |
2022年 | 14篇 |
2021年 | 29篇 |
2020年 | 34篇 |
2019年 | 17篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 56篇 |
2015年 | 30篇 |
2014年 | 38篇 |
2013年 | 28篇 |
2012年 | 53篇 |
2011年 | 74篇 |
2010年 | 21篇 |
2009年 | 12篇 |
2008年 | 51篇 |
2007年 | 44篇 |
2006年 | 43篇 |
2005年 | 28篇 |
2004年 | 33篇 |
2003年 | 18篇 |
2002年 | 24篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1985年 | 5篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1944年 | 2篇 |
1943年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1930年 | 1篇 |
1921年 | 1篇 |
1899年 | 2篇 |
排序方式: 共有766条查询结果,搜索用时 15 毫秒
51.
Mulet X Kaasgaard T Conn CE Waddington LJ Kennedy DF Weerawardena A Drummond CJ 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18415-18423
Three nucleoside lipids have been synthesized: 3'-oleoylthymidine, 3',5'-dioleoylthymidine, and 3'-phytanoylthymidine. Differential scanning calorimetry and X-ray diffraction have been employed to characterize the physical properties of these neat lipids. Polarizing optical microscopy, small-angle X-ray scattering, and cryo-transmission electron microscopy techniques have been used to investigate the phase behavior in aqueous systems. Both oleoyl-based nucleoside lipids adopted a lamellar crystalline phase in the neat form at room temperature, and the phytanoyl derivative exhibited a fluid isotropic phase. Under excess water conditions, the presence of one branched (phytanoyl) or one unsaturated (oleoyl) chain promoted the formation of a liquid-crystalline lamellar phase at physiological temperatures. In contrast, the 3',5'-dioleoylthymidine derivative is nonswelling and does not exhibit lyotropic liquid-crystalline phase behavior. The nucleolipids' propensity for DNA-type binding and recognition has been evaluated by using a monolayer system to measure surface pressure-area isotherms in a Langmuir trough and indicates that the nucleoside base is available for nonspecific hydrogen bonding in the monolayer liquid expanded state for the single-chain nucleolipids but not for the dual-chain amphiphile. 相似文献
52.
Martineau C Engelke F Taulelle F 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,212(2):311-319
The effects of multiple-resonance heteronuclear decoupling under magic angle spinning (MAS) on the resolution of one-dimensional 19F and 31P and various two-dimensional MAS NMR spectra and on the residual non-refocusable coherence lifetimes in fluorinated aluminophosphate AlPO4-CJ2, i.e. a compound that contains numerous highly abundant nuclei but no homonuclear spin bath, has been investigated. The design of the four-channel (1H, 19F, 27Al, 31P) MAS probe used for this study is first described. 1H and 1H–27Al double-resonance decouplings allows lengthening the optimized transverse relaxation and increasing the resolution in the 19F and 31P dimensions. Under the application of multi-nuclear decoupling, a two-dimensional 19F–31P CP-HETCOR correlation spectrum for AlPO4-CJ2 is recorded with unprecedented high-resolution in the two dimensions. Moreover, because 1H-decoupling increases the 19F , it has been applied during the entire duration of the 2D NMR experiments, allowing the direct use of residual small interactions to generate 19F–19F and 19F–27Al 2D NMR correlation spectra in AlPO4-CJ2. 相似文献
53.
Regina Schmitt Patrick Mayer Benjamin Kirsch Jan Aurich Charlotte Kuhn Ralf Müller Kaushik Bhattacharya 《PAMM》2014,14(1):383-384
This work is motivated by cryogenic turning which allows end shape machining and simultaneously attaining a hardened surface due to deformation induced martensitic transformations. To study the process on the microscale, a multivariant phase field model for martensitic transformations in conjunction with a crystal plastic material model is introduced. The evolution of microstructure is assumed to follow a time-dependent Ginzburg-Landau equation. To solve the field equations the finite element method is used. Time integration is performed with Euler backward schemes, on the global level for the evolution equation of the phase field, and on the element level for the crystal plastic material law. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
54.
Charlotte Kestner 《Archive for Mathematical Logic》2014,53(5-6):593-620
In this paper we prove that in modules, MS-measurability (in the sense of Macpherson–Steinhorn) depends on being able to define a measure function on the p.p. definable subgroups. We give a classification of abelian groups in terms of measurability. Finally we discuss the relation with \({\mathbb{Q}[t]}\) -valued measures. 相似文献
55.
Regina Schmitt Ralf Müller Charlotte Kuhn Herbert M. Urbassek 《Archive of Applied Mechanics (Ingenieur Archiv)》2013,83(6):849-859
A phase field model approach for multivariant martensitic transformations of stable and metastable phases is introduced. The evolution of the microstructure is examined with respect to elastic energy minimization in which one or two martensitic orientation variants are considered. In this context, the martensitic nucleation behavior is simulated for different activation barriers. Furthermore, the influence of time-dependent external loads on the formation of the different phases is studied. The numerical implementation is performed with finite elements and an implicit time integration scheme. 相似文献
56.
Cyrielle Pautigny Charlotte Debouit Philippe Vayron Tahar Ayad Virgine Ratovelomanana-Vidal 《Tetrahedron: Asymmetry》2010,21(11-12):1382-1388
The asymmetric hydrogenation of various trisubstituted enamides derived from 2-tetralones under mild reaction conditions using Ru-SYNPHOS catalysts is reported. This practical and clean method gives access to several chiral 2-aminotetralins derivatives in high isolated yields and enantiomeric excesses up to 95% depending on the substitution pattern of the aromatic ring and the nature of the amide moiety. In addition, the usefulness of the current method is demonstrated via a practical synthetic approach to the enantiomerically pure SR58611A compound, a potent and selective β3-adrenergic receptor agonist. 相似文献
57.
58.
59.
60.
Charlotte E. Boott Dr. Ali Nazemi Prof. Ian Manners 《Angewandte Chemie (International ed. in English)》2015,54(47):13876-13894
The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non‐covalent 2D polymers and frameworks, and self‐assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers. 相似文献