全文获取类型
收费全文 | 618篇 |
免费 | 21篇 |
专业分类
化学 | 386篇 |
晶体学 | 1篇 |
力学 | 28篇 |
数学 | 97篇 |
物理学 | 127篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 6篇 |
2021年 | 20篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 26篇 |
2015年 | 26篇 |
2014年 | 11篇 |
2013年 | 26篇 |
2012年 | 38篇 |
2011年 | 42篇 |
2010年 | 20篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 41篇 |
2006年 | 29篇 |
2005年 | 23篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1990年 | 5篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1966年 | 2篇 |
1956年 | 2篇 |
1954年 | 4篇 |
1909年 | 2篇 |
1884年 | 1篇 |
排序方式: 共有639条查询结果,搜索用时 15 毫秒
551.
Magazù S Maisano G Migliardo F Benedetto A 《The journal of physical chemistry. B》2008,112(30):8936-8942
In the present work an operational recipe for the mean square displacement (MSD) determination, highlighting the connection between the self-distribution function and average statistical values, is presented. The determination of the MSD and of its contributions associated with different mechanisms, together with their thermal behavior, is performed by evaluating the self-distribution function derived by elastic incoherent neutron scattering (EINS). The approach is tested on EINS data collected by the backscattering spectrometer IN13 (ILL, Grenoble, France) on two model systems such as dry myoglobin in trehalose and poly(ethylene glycol) with mean molecular weight M(w) = 400 (PEG 400). 相似文献
552.
Donati F Pucci A Cappelli C Mennucci B Ruggeri G 《The journal of physical chemistry. B》2008,112(12):3668-3679
In this work, two perylene derivatives containing different peripheral alkyl chains (i.e., N,N'-bis-(hexyl)perylene-3,4,9,10-tetracarboxyldiimide (ES-PTCDI) and N,N'-bis-(2'-ethylhexyl)perylene-3,4,9,10-tetracarboxyldiimide (EE-PTCDI)) were synthesized and efficiently dispersed at low loadings (from 0.01 to 0.1 wt %) into linear low-density polyethylene (LLDPE) by processing in the melt. Spectroscopic investigations (UV-vis and fluorescence) combined with quantum-mechanical studies demonstrated the ability of both chromophores to generate aggregates among the planar structure of dyes when dissolved in solution or dispersed into LLDPE above a certain concentration. The data acquired for dyes' dispersions into the polymer matrix reveal that the optical properties and responsiveness to mechanical stimuli are strongly dependent on the compactness of perylene aggregates provided by the different molecular structure of dyes. In particular, the strong intermolecular aggregates of ES-PTCDI resulted in being more resistant toward mechanical stress and less orientable by uniaxial drawing along the drawing direction of the film, whereas the less compact and distorted supramolecular architecture of EE-PTCDI chromophores provided composite films with a remarkable optical response to mechanical solicitations. 相似文献
553.
Minoru Eto Luca Ferretti Kenichi Konishi Giacomo Marmorini Muneto Nitta Keisuke Ohashi Walter Vinci Naoto Yokoi 《Nuclear Physics B》2007,780(3):161-187
It is argued that the dual transformation of non-Abelian monopoles occurring in a system with gauge symmetry breaking G→H is to be defined by setting the low-energy H system in Higgs phase, so that the dual system is in confinement phase. The transformation law of the monopoles follows from that of monopole-vortex mixed configurations in the system (with a large hierarchy of energy scales, v1v2) , under an unbroken, exact color-flavor diagonal symmetry . The transformation property among the regular monopoles characterized by π2(G/H), follows from that among the non-Abelian vortices with flux quantized according to π1(H), via the isomorphism π1(G)π1(H)/π2(G/H). Our idea is tested against the concrete models—softly-broken supersymmetric SU(N), SO(N) and USp(2N) theories, with appropriate number of flavors. The results obtained in the semiclassical regime (at v1v2Λ) of these models are consistent with those inferred from the fully quantum-mechanical low-energy effective action of the systems (at v1,v2Λ). 相似文献
554.
555.
Giacomo Perfetti Thibault Alphazan W. J. Wildeboer Gabrie M. H. Meesters 《Journal of Thermal Analysis and Calorimetry》2012,109(1):203-215
Hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA) are important polymers in pharmaceutical, food and other industries being largely used as encapsulation agents. The characterization of two reference grades of HPMC (Pharmacoat? 603 and Pharmacoat? 615) and one reference grade of PVA (Mowiol? 4-98), through X-ray diffraction (XRD) and thermogravimetry (TG) is described. Specific analyses were performed by means of dynamic vapour sorption analysis of water adsorption/desorption from vapours at 10, 25, 40, 55 and 70?°C. Guggenheim?CAnderson?Cde Boer (GAB), Brunauer?CEmmett?CTeller (BET), Park and n-layer BET models were successfully used to fit the experimental data. The glass transition temperature as function of water content was measured by means of differential scanning calorimetry (DSC). The experimental data were analysed according to Linear, Gordon?CTaylor, Fox and Roos equations. XRD studies revealed amorphous structure for the Pharmacoat??603 and Pharmacoat??615 and crystalline for Mowiol??4-98. Single and multi-step temperature degradation point was found for Pharmacoat??603 and Pharmacoat??615 and Mowiol??4-98, respectively. The water uptake is higher for Pharmacoat??603 and Pharmacoat??615 than Mowiol??4-98. The influence of temperature on water uptake is opposite for the two types of polymers. GAB and n-layer BET were found to better model Pharmacoat??603 and Pharmacoat??615 and Mowiol??4-98 data, respectively. The water makes the glass transition to decrease quite drastically. Gordon?CTaylor is better fitting the experimental data both for Pharmacoat??603 and Pharmacoat??615 and Mowiol??4-98. 相似文献
556.
557.
Giacomo Renzetti 《Central European Journal of Physics》2013,11(5):531-544
An annotated guide to navigate the intricate history of the attempts to measure the Lense-Thirring orbital precessions with artificial satellites is offered to the reader. 相似文献
558.
Carnevale V Fiorin G Levine BG Degrado WF Klein ML 《The journal of physical chemistry. C, Nanomaterials and interfaces》2010,114(48):20856-20863
The tetrameric M2 protein bundle of the influenza A virus is the proton channel responsible for the acidification of the viral interior, a key step in the infection cycle. Selective proton transport is achieved by successive protonation of the conserved histidine amino acids at position 37. A recent X-ray structure of the tetrameric transmembrane (TM) domain of the protein (residues 22-46) resolved several water clusters in the channel lumen, which suggest possible proton pathways to the His37 residues. To explore this hypothesis, we have carried out molecular dynamics (MD) simulations of a proton traveling towards the His37 side chains using MD with classical and quantum force fields. Diffusion through the first half of the channel to the "entry" water cluster near His37 may be hampered by significant kinetic barriers due to electrostatic repulsion. However, once in the entry cluster, a proton can move to one of the acceptor His37 in a nearly barrierless fashion, as evidenced both by MD simulations and a scan of the potential energy surface (PES). Water molecules of the entry cluster, although confined in the M2 pore and restricted in their motions, can conduct protons with a rate very similar to that of bulk water. 相似文献
559.
560.
Lino Colombo Marcello Di Giacomo Massimo Serra Simone M. Tambini 《Tetrahedron》2009,65(29-30):5838-5843
We report two different synthetic approaches for the stereoselective synthesis of (2E,4E)-4-(4,4-dimethylpent-2-ynylidene)-N1,N5-dimethyl-N1,N5-bis(naphthalen-1-ylmethyl)pent-2-ene-1,5-diamine 1, an important impurity-reference standard for the chemical characterization of terbinafine. The diamine 1 was obtained in only six steps with a good overall yield starting from commercially available glutaconic acid. 相似文献