全文获取类型
收费全文 | 755篇 |
免费 | 12篇 |
国内免费 | 4篇 |
专业分类
化学 | 291篇 |
晶体学 | 2篇 |
力学 | 24篇 |
数学 | 183篇 |
物理学 | 271篇 |
出版年
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 13篇 |
2012年 | 29篇 |
2011年 | 27篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 35篇 |
2007年 | 34篇 |
2006年 | 34篇 |
2005年 | 35篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 24篇 |
1995年 | 10篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 12篇 |
1973年 | 8篇 |
排序方式: 共有771条查询结果,搜索用时 15 毫秒
761.
Ball V Dahéron L Arnoult C Toniazzo V Ruch D 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):1859-1866
The concept of reactive layer-by-layer (LBL) deposition allows the build-up of films containing polycations and oxide particles, namely, silica and poorly crystalline anatase. Because polyelectrolyte multilayer films have been produced from blended polyanions or polycations solutions and since preferential incorporation of one of the partners of the blend has been found in most cases, one should wonder if a preferential polycondensation of either silica or titania should occur when the reactive deposition is performed from a solution containing a precursor of both inorganic species. X-ray photoelectron (XPS) and UV-visible spectroscopies show that the reactive LBL films made from the blend and poly(diallyldimethylammonium chloride) (PDADMAC) incorporate predominantly silica over TiO(2) over the whole molar fraction range of the silicic acic/hydrosoluble Ti(IV) complex. The transparency of the films below 365 nm, corresponding to the band edge of TiO(2), can easily be modulated. The silica/TiO(2) films are all able to bind hexacyanoferrate owing to the presence of the polycation allowing the binding of the oxide particles to the substrate. However, the binding capacity of the film does not scale proportionally to its thickness. The films made from eight dipping cycles showed a sudden decrease in their binding capacity for hexacyanoferrate when the molar fraction of the titanium complex was higher than ~0.6 in the blend. For the same films, electrochemical impedance spectra (EIS) showed marked differences with a change in film composition: the more TiO(2) in the film, the higher the resistance to electron and to mass transfer. Therefore, EIS helps to explain the reduced surface concentration measured by means of cyclic voltammetry for films rich in TiO(2). 相似文献
762.
Zhang J Al-Eryani R Ball HL 《Journal of the American Society for Mass Spectrometry》2011,22(11):1958-1967
Peptides with two or more basic residues, including those with post-translational modifications (PTMs), such as methylation
and phosphorylation, can be highly hydrophilic and, therefore, are often difficult to be retained on a reversed-phase (RP)
column. In addition, these highly hydrophilic peptides may carry two or more positive charges, which often fragment poorly
upon collisionally activated dissociation (CAD), resulting in few sequence-specific ions. C-terminal rearrangement may also
occur during CAD. Furthermore, some PTMs are labile and tend to be lost when subjected to CAD as is the case with phosphorylation
on serine or threonine. To overcome the difficulties of separation, detection, and fragmentation of highly hydrophilic peptides,
we report here the effect of carboxy group derivatization with 2-nitrophenylhydrazine (this strategy will be called NPHylation
for simplicity). NPHylation significantly increases the hydrophobicity of the peptides, eliminates C-terminal rearrangement
in all cases, and offers enhanced sensitivity in some cases. In addition, the CAD spectra of the resulting NPHylated peptides
carry more sequence-specific ions due to significant reduction of sequence scrambling as observed for peptide EHAGVISVL. Furthermore,
the different carboxy derivatives of this peptide undergo sequence scrambling to varying degrees, which clearly demonstrates
that the C-terminus has a profound effect on peptide fragmentation. Finally, sequence scrambling is a charge dependent phenomenon,
which affects CAD of doubly charged peptides far more than their singly charged counterparts. 相似文献
763.
We extend our previous results on small-x resummation in the pure Yang–Mills theory to full QCD with nf quark flavours, with a resummed two-by-two matrix of resummed quark and gluon splitting functions. We also construct the corresponding deep-inelastic coefficient functions, and show how these can be combined with parton densities to give fully resummed deep-inelastic structure functions F2 and FL at the next-to-leading logarithmic level. We discuss how this resummation can be performed in different factorization schemes, including the commonly used scheme. We study the importance of the resummation effects by comparison with fixed-order perturbative results, and we discuss the corresponding renormalization and factorization scale variation uncertainties. We find that for x below 10−2 the resummation effects are comparable in size to the fixed order NNLO corrections, but differ in shape. We finally discuss the phenomenological impact of the small-x resummation, specifically in the extraction of parton distribution from present day experiments and their extrapolation to the kinematics relevant for future colliders such as the LHC. 相似文献
764.
Girod FX Niyazov RA Avakian H Ball J Bedlinskiy I Burkert VD De Masi R Elouadrhiri L Garçon M Guidal M Jo HS Joo K Kubarovsky V Kuleshov SV MacCormick M Niccolai S Pogorelko O Sabatié F Stepanyan S Stoler P Ungaro M Zhao B Amaryan MJ Ambrozewicz P Anghinolfi M Asryan G Bagdasaryan H Baillie N Ball JP Baltzell NA Batourine V Battaglieri M Bellis M Benmouna N Berman BL Biselli AS Blaszczyk L Bouchigny S Boiarinov S Bradford R Branford D Briscoe WJ Brooks WK Bültmann S Butuceanu C Calarco JR 《Physical review letters》2008,100(16):162002
The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (e p-->epgamma) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (x(B) from 0.11 to 0.58, Q2 from 1 to 4.8 GeV2, -t from 0.09 to 1.8 GeV2), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A approximately a sinphi/(1+c cosphi). This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector. 相似文献
765.
Direct photon production is an important process at hadron colliders, being relevant both for precision measurement of the gluon density, and as background to Higgs and other new physics searches. Here we explore the implications of recently derived results for high-energy resummation of direct photon production for the interpretation of measurements at the Tevatron and the LHC. The effects of resummation are compared to various sources of theoretical uncertainties like PDFs and scale variations. We show how the high-energy resummation procedure stabilizes the logarithmic enhancement of the cross section at high energy which is present at any fixed order in the perturbative expansion starting at NNLO. The effects of high-energy resummation are found to be negligible at Tevatron, while they enhance the cross section by a few percent for pT?10 GeV at the LHC. Our results imply that the discrepancy at small pT between fixed order NLO and Tevatron data cannot be explained by unresummed high-energy contributions. 相似文献
766.
Alexandre Chappard Dr. Craig Leighton Dr. Rebecca S. Saleeb Kiani Jeacock Dr. Sarah R. Ball Katie Morris Owen Kantelberg Dr. Ji-Eun Lee Dr. Elsa Zacco Prof. Dr. Annalisa Pastore Prof. Dr. Margaret Sunde Dr. David J. Clarke Dr. Patrick Downey Prof. Dr. Tilo Kunath Dr. Mathew H. Horrocks 《Angewandte Chemie (International ed. in English)》2023,62(15):e202216771
Protein misfolding and aggregation into oligomeric and fibrillar structures is a common feature of many neurogenerative disorders. Single-molecule techniques have enabled characterization of these lowly abundant, highly heterogeneous protein aggregates, previously inaccessible using ensemble averaging techniques. However, they usually rely on the use of recombinantly-expressed labeled protein, or on the addition of amyloid stains that are not protein-specific. To circumvent these challenges, we have made use of a high affinity antibody labeled with orthogonal fluorophores combined with fast-flow microfluidics and single-molecule confocal microscopy to specifically detect α-synuclein, the protein associated with Parkinson's disease. We used this approach to determine the number and size of α-synuclein aggregates down to picomolar concentrations in biologically relevant samples. 相似文献
767.
Ben W. Joynson Dr. Graham R. Cumming Dr. Liam T. Ball 《Angewandte Chemie (International ed. in English)》2023,62(31):e202305081
We demonstrate that arylchlorodiazirines serve as photo-activated halocarbene precursors for the selective one-carbon ring expansion of N-substituted pyrroles and indoles to the corresponding pyridinium and quinolinium salts. Preliminary investigations indicate that the same strategy also enables the conversion of N-substituted pyrazoles to pyrimidinium salts. The N-substituent of the substrate plays an essential role in: (1) increasing substrate scope by preventing product degradation, (2) enhancing yields by suppressing co-product inhibition, and (3) activating the azinium products towards subsequent synthetic manipulations. This latter point is illustrated by subjecting the quinolinium salts to four complementary partial reductions, which provide concise access to ring-expanded products with different degrees of increased C(sp3) character. Thermal analysis of the diazirines by differential scanning calorimetry (DSC) provides detailed insight into their energetic properties, and highlights the safety benefits of photolyzing—rather than thermolyzing—these reagents. 相似文献
768.
769.
Skeletal editing involves making specific point-changes to the core of a molecule through the selective insertion, deletion or exchange of atoms. It thus represents a potentially powerful strategy for the step-economic modification of complex substrates and is a perfect complement to methods such as C−H functionalization that target the molecular periphery. Given their ubiquity in biologically active compounds, the ability to perform skeletal editing on – and therefore interconvert between – aromatic heterocycles is especially valuable. This review summarizes both recent and key historical examples of skeletal editing as applied to interconversion of aromatic rings; we anticipate that it will serve to highlight not only the innovative and enabling nature of current skeletal editing methods, but also the tremendous opportunities that still exist in the field. 相似文献
770.