全文获取类型
收费全文 | 555篇 |
免费 | 39篇 |
国内免费 | 3篇 |
专业分类
化学 | 394篇 |
晶体学 | 2篇 |
力学 | 22篇 |
数学 | 69篇 |
物理学 | 110篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 43篇 |
2012年 | 42篇 |
2011年 | 62篇 |
2010年 | 28篇 |
2009年 | 21篇 |
2008年 | 26篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 30篇 |
2004年 | 19篇 |
2003年 | 22篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1995年 | 3篇 |
1993年 | 30篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有597条查询结果,搜索用时 15 毫秒
521.
Brillet K Reimmann C Mislin GL Noël S Rognan D Schalk IJ Cobessi D 《Journal of the American Chemical Society》2011,133(41):16503-16509
Pyochelin (Pch) and enantiopyochelin (EPch) are enantiomeric siderophores, with three chiral centers, produced under iron limitation conditions by Pseudomonas aeruginosa and Pseudomonas fluorescens , respectively. After iron chelation in the extracellular medium, Pch-Fe and EPch-Fe are recognized and transported by their specific outer-membrane transporters: FptA in P. aeruginosa and FetA in P. fluorescens . Structural analysis of FetA-EPch-Fe and FptA-Pch-Fe, combined with mutagenesis and docking studies revealed the structural basis of the stereospecific recognition of these enantiomers by their respective transporters. Whereas FetA and FptA have a low sequence identity but high structural homology, the Pch and EPch binding pockets do not share any structural homology, but display similar physicochemical properties. The stereospecific recognition of both enantiomers by their corresponding transporters is imposed by the configuration of the siderophore's C4' and C2' chiral centers. This recognition involves specific hydrogen bonds between the Arg91 guanidinium group and EPch-Fe for FetA and between the Leu117-Leu116 main chain and Pch-Fe for FptA. FetA and FptA are the first membrane receptors to be structurally described with opposite binding enantioselectivities for their ligands, giving insights into the structural basis of their enantiospecificity. 相似文献
522.
Chodera JD Swope WC Noé F Prinz JH Shirts MR Pande VS 《The Journal of chemical physics》2011,134(24):244107
Dynamical averages based on functionals of dynamical trajectories, such as time-correlation functions, play an important role in determining kinetic or transport properties of matter. At temperatures of interest, the expectations of these quantities are often dominated by contributions from rare events, making the precise calculation of these quantities by molecular dynamics simulation difficult. Here, we present a reweighting method for combining simulations from multiple temperatures (or from simulated or parallel tempering simulations) to compute an optimal estimate of the dynamical properties at the temperature of interest without the need to invoke an approximate kinetic model (such as the Arrhenius law). Continuous and differentiable estimates of these expectations at any temperature in the sampled range can also be computed, along with an assessment of the associated statistical uncertainty. For rare events, aggregating data from multiple temperatures can produce an estimate with the desired precision at greatly reduced computational cost compared with simulations conducted at a single temperature. Here, we describe use of the method for the canonical (NVT) ensemble using four common models of dynamics (canonical distribution of Hamiltonian trajectories, Andersen thermostatting, Langevin, and overdamped Langevin or Brownian dynamics), but it can be applied to any thermodynamic ensemble provided the ratio of path probabilities at different temperatures can be computed. To illustrate the method, we compute a time-correlation function for solvated terminally-blocked alanine peptide across a range of temperatures using trajectories harvested using a modified parallel tempering protocol. 相似文献
523.
Besnard M Cabaço MI Chávez FV Pinaud N Sebastião PJ Coutinho JA Danten Y 《Chemical communications (Cambridge, England)》2012,48(9):1245-1247
The formation of 1-butyl-3-methylimidazolium-2-carboxylate in the mixture of CO(2) with 1-butyl-3-methylimidazolium acetate under mild conditions (298 K, 0.1 MPa) has been put in evidence in the liquid phase using Raman and infrared spectroscopy complemented by DFT calculations and NMR ((1)H, (13)C, (15)N) spectroscopy. 相似文献
524.
César V Tourneux JC Vujkovic N Brousses R Lugan N Lavigne G 《Chemical communications (Cambridge, England)》2012,48(17):2349-2351
An elusive free 4-(isopropylamino)imidazol-2-ylidene is engaged in a tautomeric equilibrium with its mesoionic tautomer, 4-(isopropylamido)imidazolium, which displays the typical reactivity of a cyclic diaminocarbene; once coordinated to a Rh(I) centre, it undergoes a smooth 4e(-) oxidation of its backbone to yield an amido-amidino-carbene, a weak electron donor viable only in its complexed form. 相似文献
525.
526.
JR Hiscock PA Gale N Lalaoui ME Light NJ Wells 《Organic & biomolecular chemistry》2012,10(38):7780-7788
The influence of anions on tautomerism in benzimidazole containing anion receptors has been studied via a variety of techniques in both solution and the solid state. The results show that hydrogen bonding interactions between the receptors and guests have a significant effect of the nature of the tautomer present. The compounds show a preference for complexation of lactate over pyruvate. 相似文献
527.
S. Millour L. Noël R. Chekri C. Vastel A. Kadar T. Guérin 《Accreditation and quality assurance》2010,15(9):503-513
In 2006, the French Food Safety Agency (AFSSA) started the second French Total Diet Study to assess exposure to essential
and non-essential elements through dietary intake by analysing 1352 food samples. A total of 21 elements were analysed to
date by Inductively Coupled Plasma Mass Spectrometry after closed vessel microwave digestion, in 660 samples corresponding
to at half of the study. This work presents and discusses the results of the various internal quality controls (IQC) applied
to ensure that the analytical procedure is correctly carried out, from digestion to analysis, and to enable analytical chemists
to validate the results obtained. The whole IQC allows to estimate uncertainties according to elements and to select those
that should be discarded from the study or only given as indicative values for elements that were not within defined quality
limits. 相似文献
528.
Rohand T Baruah M Qin W Boens N Dehaen W 《Chemical communications (Cambridge, England)》2006,(3):266-268
The BODIPY chromophore can be easily modified by nucleophilic mono- or disubstitution of 3,5-dichloroBODIPY with O-, N-, S- and C-nucleophiles. Absorption and fluorescence spectral data of the new BODIPY derivatives are also reported. 相似文献
529.
Antunes MA Dias M Monteiro B Domingos A Santos IC Marques N 《Dalton transactions (Cambridge, England : 2003)》2006,(27):3368-3374
Reaction of [U{(SiMe2NPh)3-tacn}Cl] with LiNEt2 or LiNPh2 affords the corresponding amide compounds, [U{(SiMe2NPh)3-tacn}(NR2)] (R = Et (1), R = Ph (2)). The complexes have been fully characterized by spectroscopic methods and the solid-state structure of 1 was determined by single-crystal X-ray diffraction analysis. The six nitrogen atoms of the tris(dimethylsilylanilide)triazacyclononane ligand are in a trigonal prismatic configuration with the nitrogen atom of the diethylamide ligand capping one of the trigonal faces of the trigonal prism. Crystallization of 2 from CH3CN solution gave crystals of the six-membered heterocycle [U{(SiMe2NPh)3-tacn}{kappa2-(HNC(Me))2CC[triple bond]N}] (3). The reactivity of the amides was investigated. Both compounds undergo acid-base reactions with protic substrates such as HOC6H2-2,4,6-Me3, 3,5-Me2pzH (pz = pyrazolyl) and HSC5H4N to give the corresponding [U{(SiMe2NPh)3-tacn}X] (X = OC6H2-2,4,6-Me3 (4), 3,5-Me2pzH (5), kappa2-SC5H4N (6)) complexes. The solid-state structures of and were determined by single-crystal X-ray diffraction and revealed that the compounds are eight-coordinate with dodecahedral geometry. 相似文献
530.
Christophe Matignon Daniel Desbordes Henri Noël Presles 《Comptes Rendus Mecanique》2006,334(4):238-242
The goal of this Note is to determine the influence of H2 addition on the detonation and detonability of stoichiometric CH4/O2/N2 mixtures for three values of the nitrogen dilution ( (oxygen); 2; 3.76 (air)) and also of the influence of the initial temperature. It is based on the measurement of the mean cell size of the steady self-sustained detonation in these mixtures, this characteristic length being representative of the mixture detonability. Results indicate that the detonability of the (CH4H2) mixture is mainly controlled by the heavier fuel, i.e., CH4 and for instance the detonability of the mixture where 20% of CH4 volume has been replaced by H2 is nearly the same as that of the mixture where CH4 is the only fuel. The influence of the initial temperature on the detonability depends on N2 concentration. To cite this article: C. Matignon et al., C. R. Mecanique 334 (2006). 相似文献