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101.
Dr. Christopher J. Shaffer Dr. Detlef Schröder Dr. Christian Alcaraz Dr. Ján Žabka Dr. Emilie‐Laure Zins 《Chemphyschem》2012,13(11):2688-2698
Even in the highly diluted gas phase, rather than electron transfer the benzene dication C6H62+ undergoes association with dinitrogen to form a transient C6H6N22+ dication which is best described as a ring‐protonated phenyl diazonium ion. Isotopic labeling studies, photoionization experiments using synchrotron radiation, and quantum chemical computations fully support the formation of protonated diazonium, which is in turn a prototype species of superacidic chemistry in solution. Additionally, reactions of C6H62+ with background water involve the transient formation of diprotonated phenol and, among other things, afford a long‐lived C6H6OH22+ dication, which is attributed to the hydration product of Hogeveen’s elusive pyramidal structure of C6H62+, as the global minimum of doubly ionized benzene. Nitrogen is essential for the formation of the C6H6OH22+ dication in that it mediates the formation of the water adduct, while the bimolecular encounter of the C6H62+ dication with water only leads to (dissociative) electron transfer. 相似文献
102.
103.
Putkunz CT D'Alfonso AJ Morgan AJ Weyland M Dwyer C Bourgeois L Etheridge J Roberts A Scholten RE Nugent KA Allen LJ 《Physical review letters》2012,108(7):073901
Ptychographic coherent diffractive imaging (CDI) has been extensively applied using both x rays and electrons. The extension to atomic resolution has been elusive. This Letter demonstrates ptychographic electron diffractive imaging at atomic resolution, permitting identification of structure in a boron nitride helical cone at a resolution of order 1 ?, beyond that of comparative Z-contrast images. A scanning transmission electron microscope is used to create a diverging illumination in a defocused Fresnel CDI geometry, providing a robust strategy leading to a unique solution. 相似文献
104.
Schroeder BC Ashraf RS Thomas S White AJ Biniek L Nielsen CB Zhang W Huang Z Tuladhar PS Watkins SE Anthopoulos TD Durrant JR McCulloch I 《Chemical communications (Cambridge, England)》2012,48(62):7699-7701
Thieno[3,2-b]thienobis(silolothiophene), a new electron rich hexacyclic monomer has been synthesized and incorporated into three novel donor-acceptor low-bandgap polymers. By carefully choosing the acceptor co-monomer, the energy levels of the polymers could be modulated and high power conversion efficiencies of 5.52% were reached in OPV devices. 相似文献
105.
Prof. Eric Collet Dr. Maciej Lorenc Dr. Marco Cammarata Dr. Laurent Guérin Dr. Marina Servol Dr. Antoine Tissot Dr. Marie‐Laure Boillot Prof. Hervé Cailleau Prof. Marylise Buron‐Le Cointe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(7):2051-2055
We study by 100 picosecond X‐ray diffraction the photo‐switching dynamics of single crystal of the orthorhombic polymorph of the spin‐crossover complex [(TPA)Fe(TCC)]PF6, in which TPA=tris(2‐pyridyl methyl)amine, TCC2?=3,4,5,6‐Cl4‐Catecholate2?. In the frame of the emerging field of dynamical structural science, this is made possible by using optical pump/X‐ray probe techniques, which allow following in real time structural reorganization at intra‐ and intermolecular levels associated with the change of spin state in the crystal. We use here the time structure of the synchrotron radiation generating 100 picosecond X‐ray pulses, coupled to 100 fs laser excitation. This study has revealed a rich variety of structural reorganizations, associated with the different steps of the dynamical process. Three consecutive regimes are evidenced in the time domain: 1) local molecular photo‐switching with structural reorganization at constant volume, 2) volume relaxation with inhomogeneous distribution of local temperatures, 3) homogenization of the crystal in the transient state 100 µs after laser excitation. These findings are fundamentally different from those of conventional diffraction studies of long‐lived photoinduced high spin states. The time‐resolution used here with picosecond X‐ray diffraction probes different physical quantities on their intrinsic time‐scale, shedding new light on the successive processes driving macroscopic switching in a functionalized material. These results pave the way for structural studies away from equilibrium and represent a first step toward femtosecond crystallography. 相似文献
106.
Matthieu Tissot Daniele Poggiali Dr. Hélène Hénon Daniel Müller Dr. Laure Guénée Dr. Marc Mauduit Prof. Alexandre Alexakis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8731-8747
The copper‐catalyzed conjugate addition of various Grignard reagents to polyconjugated enones (dienone and enynone derivatives) is reported. The catalyst system, composed of copper triflate and an NHC ligand, led to the unusual selective formation of the 1,4‐addition products. This reaction allows for the creation of all‐carbon chiral quaternary centers with enantiomeric excesses up to 99 %. The remaining unsaturation on the 1,4 adducts give access to valuable synthetic transformations. 相似文献
107.
Costes JP Duhayon C Vendier L Colacio E Mota Ávila AJ Suarez Varela J 《Inorganic chemistry》2012,51(2):1011-1019
The copper template effect allows the preparation of tridentate ligands that chelate copper ions, leaving unoccupied the fourth basal coordination position and at least one axial position of the copper coordination polyhedron. Two such cationic complexes, [LCu](+) and [L(1)Cu](+) (L(-) = 2-{(E)-[(2-aminoethyl)imino]methyl}phenoxo] and L(1-) = 2-{(E)-[(2-aminopropyl)imino]methyl}phenoxo), react with diamagnetic polycyanometalate tectons such as Ni(CN)(4)(2-) or Ag(CN)(2)(-) to yield different neutral 1D complexes. In {[(LCu)(2)Ni(CN)(4)]}(n) (1) the four cyano nitrogen atoms are involved in coordination with copper ions in such a manner that each copper atom is pentacoordinated and linked to two cyano functions that occupy axial and equatorial coordination positions. Two L(1)Cu(+) cationic entities are linked, through their equatorial plane, to two trans cyano groups of the Ni(CN)(4)(2-) tecton in complex [(L(1)Cu)(2)Ni(CN)(4)] (2), the two uncoordinated cyano groups being involved in hydrogen bonds. 2 is a racemate, a S stereoisomer being associated with a R one in each [(L(1)Cu)(2)Ni(CN)(4)] unit. Zigzag Cu-Ag chains are present in [(LCu)Ag(CN)(2)] (3), where the copper centers are pentacoordinated and connected to the cyano groups in an alternate axial-equatorial coordination scheme. A bidimensional structure is developed by interchain argentophilic interactions. In complex 4, {(L(1)CuMeOH)(L(1)Cu)[Ag(CN)(2)](2)}, two L(1)Cu units are connected by a NC-Ag-CN bridge in an equatorial position. These resulting units exhibit argentophilic interactions with [Ag(CN(2))](-) entities that are monocoordinated in the equatorial position to the next unit, ultimately leading to a chain. Weak Cu-Cu magnetic interactions are detected in the four compounds, antiferromagnetic in the case of equatorial-equatorial copper interactions, ferromagnetic for orthogonal interacting copper orbitals (axial-equatorial interactions), while axial-axial bridges are characterized by an absence of interaction. The presence of weak ferromagnetic interactions through large NC-Ni-CN or NC-Ag-CN bridges (Cu···Cu distances larger than 10 ?) furnishes experimental evidence for the existence of next-nearest-neighbor interactions through diamagnetic centers. DFT calculations do confirm the existence of these magnetic transmission pathways through the diamagnetic metal bridge. 相似文献
108.
We consider in this paper the numerical solution of the Falkner-Skan differential equation, modelling under some similarity assumptions the boundary layer equation. We look for the extremal solution of this third order differential equation. The methods we use are basically the Newton method with a shooting process, which is coupled with a continuation method: they allow us to follow the solution arcs which contain regular and turning point solutions. 相似文献
109.
While the μ-alkylidenetungsten complex, (CO)9W2CHCHC(CH3)2 gives the expected ester resulting from CO insertion-solvolysis reactions, the μ-alkylidene-iron complex (CO)8Fe2CH2 gives, as well as the expected ester, a malonate formed by double carbonylation of the bridging carbon atom. 相似文献
110.
Nguyen Ba Chanh Christian Hauw Alain Meresse Madeleine Rey-Lafon Laure Ricard 《Journal of Physics and Chemistry of Solids》1985,46(12):1413-1420
The existence of three main crystalline phases (called III, II and I) in (C12H25NH3)2CdCl4 has been revealed by differential scanning calorimetry. X-ray diffraction and spectroscopic studies. The crystal- lographic evolution with increasing temperature appears to be monoclinic (III) → orthorhombic (II) → tetragonal (I). The low temperature phase III is the only ordered structure. The phase transition (III-II), which is of first order type, corresponds to an order-disorder mechanism involving the organic part of the structure (alkylammonium chains) whereas the phase transition (II-I), which is of second-order type, is related to the arrangement of the mineral matrix (octahedra of perovskite layers). An intermediate disordered form II', stable in a very narrow temperature range and structurally similar to the form II, has also been observed, so that the transformation (III-II) proceeds, in fact, in two steps (III-II'-II). The variation enthalpies observed at the transitions (III-II'-II) and analyzed through an order-disorder mechanism demonstrate the high disorder of the alkylammonium chains in form II, in agreement with spectroscopic results. No thermal anomaly or spectroscopic modification is observed for the high temperature transition (II-I). 相似文献