全文获取类型
收费全文 | 367篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 302篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 49篇 |
物理学 | 24篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 14篇 |
2012年 | 38篇 |
2011年 | 33篇 |
2010年 | 18篇 |
2009年 | 13篇 |
2008年 | 23篇 |
2007年 | 24篇 |
2006年 | 13篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 13 毫秒
31.
Helen?BarbasEmail author Claus?C?Hilgetag Subhash?Saha Caterina?R?Dermon Joanna?L?Suski 《BMC neuroscience》2005,6(1):32
Background
The neocortical commissures have a fundamental role in functional integration across the cerebral hemispheres. We investigated whether commissural projections in prefrontal cortices are organized according to the same or different rules as those within the same hemisphere, by quantitatively comparing density, topography, and laminar origin of contralateral and ipsilateral projections, labeled after unilateral injection of retrograde tracers in prefrontal areas. 相似文献32.
We define the algorithmic complexity of a quantum state relative to a given precision parameter, and give upper bounds for various examples of states. We also establish a connection between the entanglement of a quantum state and its algorithmic complexity. 相似文献
33.
Villoresi P Bonora S Pascolini M Poletto L Tondello G Vozzi C Nisoli M Sansone G Stagira S De Silvestri S 《Optics letters》2004,29(2):207-209
We present a method for the optimization of high-order harmonic generation based on wave-front correction of the driving laser beam. The technique exploits wave-front adaptive control by means of a deformable mirror, governed by an optimization procedure. 相似文献
34.
Caterina?Minelli Isabelle?Geissbuehler Rolf?Eckert Horst?Vogel Harry?Heinzelmann Martha?LileyEmail author 《Colloid and polymer science》2004,282(11):1274-1278
We present an extremely versatile method for the lateral organization of nano-scale objects (NOs) based on the phenomenon of polymer demixing. NOs are suspended in a solution of two immiscible polymers, which is used to form a thin polymer film by spin coating. During spin coating the two polymers separate to give a microphase structure, whose length scale depends on the experimental conditions. The NOs spontaneously partition into one or other of the polymer phases resulting in their lateral organization. In this work, the organization of CdSe nanoparticles and fluorescent organic dyes was studied by fluorescence microscopy. The NOs were organized in the polymer film in stochastic patterns or in ordered designs on substrates pre-patterned by soft-lithography techniques. Single-particle measurements, using confocal microscopy, showed that at low concentrations there was little aggregation of the particles. 相似文献
35.
[reaction: see text] A highly regio- and stereoselective bis-stannylation of unsymmetrically substituted butadiyne 3 provides bis-stannane 4. Selective lithiation of the internal tin residue effects a 1,4-retro-Brook rearrangement to afford vinylsilane 5. This was elaborated into the novel diethynylethene 1, which also functions as a masked triyne. 相似文献
36.
37.
Massimiliano Aschi Caterina Fraschetti Antonello Filippi Maurizio Speranza 《Journal of mass spectrometry : JMS》2009,44(7):1038-1046
The nature of the ionic species, formed by electrospray ionization (ESI) of Co(NO3)2/CH3OH solutions with a pair of aminoalcohols W and Y, has been investigated by mass spectrometric and computational methods. Collision induced dissociation (CID) of ions, formally corresponding to the [WYCoNO3]+ structures, yields fragmentation patterns which reflect not only the expected [WYCoNO3]+ connectivity but also that of other isomeric structures. Formation of these latter species is observed only in the presence of a tertiary aminoalcohol, like N‐methylpseudoephedrine. The CID patterns are found to be strongly dependent on the chemical form (whether the free aminoalcohol or its hydrochloride), the configuration, and the relative concentration of the W and Y aminoalcohols. This variability parallels the results of classical MD (molecular dynamics) simulations of the [WYCoNO3]+ adducts which show a drastic alteration of the mechanical–dynamical features of the adducts by simply changing the charge state of W and/or Y, their absolute configuration, or by removing the solvent. The present experimental and computational study confirms the observation of fast stereoselective reactions in ESI nanodroplets before their evaporation and warns against any automatic correlation between the ESI spectrum of an analyte and its structure in solution. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
38.
Giuliano Alagona Caterina Ghio Alessandro Giolitti Susanna Monti 《Theoretical chemistry accounts》1999,101(1-3):143-150
Several histidine-tryptophan complexes (either stacked or T-shaped), derived from the crystal structures available in the
Brookhaven Protein Data Bank, have been examined with molecular mechanics (MM), using the Tripos force field with Gasteiger-Hückel
charges, whose trend was found to be analogous to the AMBER or CHARMM ones. The MM results were compared to the ab initio
MP2 results, with and without counterpoise (CP) correction, previously obtained using extended basis sets on 5-methylimidazole
and indole as model systems. MM seems to underestimate the interaction energy between the two monomers when compared to the
uncorrected MP2 results, while the agreement is much better after including the CP correction at the MP2 level in all cases.
MM was thus used to qualitatively analyse the dependence of the stacking energy on the ring rotation at a variable distance
and ring centroid displacement for these systems, while keeping the rings in parallel planes. An analogous study was carried
out for a T-shaped adduct.
Received: 24 March 1998 / Accepted: 3 September 1998 / Published online: 1 February 1999 相似文献
39.
40.
Caterina Canovaro Irene Calliari Michele Asolati Francesco Grazzi Antonella Scherillo 《Applied Physics A: Materials Science & Processing》2013,112(4):1019-1025
Mixing of different organic charge-transfer-complexes (CT-complexes) might allow the adjustment of the optical and morphological properties of the resulting material system. In this work, a study of two CT-complexes, mixed by thermal coevaporation at different concentrations by substituting only the acceptor molecules, is presented. Electron diffraction patterns, which were collected on samples of the ternary system of the prototypical CT-complexes DBTTF-TCNQ and DBTTF-F4TCNQ do not show any indication of a mixed crystalline phase or novel crystalline order. X-ray diffraction measurements additionally confirm the phase separation in the ternary system. However, upon mixing of the complexes, the degree of crystallinity of the individual phases is reduced. This effect correlates with the mixing ratio of the CT-complexes in the ternary compound. Furthermore, we do not observe a shift or the appearance of new peaks in the infrared spectra of (DBTTF-TCNQ) x :(DBTTF-F4TCNQ)1?x . Hence, there is no indication for a pronounced or novel chemical interaction between the individual CT-complexes in the mixed compound. 相似文献