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411.
Boron periodination of o-carborane has been achieved by taking account of the fact that B atoms in the cluster are of two types, i.e., those adjacent to both C atoms and the remainder. The high number of nonequivalent leaving groups opens the possibility through B-C coupling to materials with novel possibilities and to self-assembling due to the enhanced polarizability of the C-H bond. Periodination has accentuated the acidity of the carborane, and monoprotic salts are stable in water. 相似文献
412.
In order to obtain chiral compounds of low molecular weight expected to exhibit mesogenic and ferroelectric properties, the asymmetric carbon was introduced into the central part of the molecule. The series consists of nine chiral dimers in which the chiral flexible spacer derives from S-2-chlorosuccinic acid. The mesomorphic properties of the compounds were studied and all of them were found to be mesogenic. From n = 6 onwards the mesophases were chiral smectic C. Some analogous compounds derived from S-2-chloroglutaric acid were also prepared; these were not found to be mesogenic. The thermal instability of the 2-chlorosuccinic acid derivatives prevented the study of their ferroelectric properties. We attempted to perform this study for several mixtures involving 3-methyladipic acid derivatives and both 2-chlorosuccinic and 2-chloroglutaric acids derivatives. All the mixtures studied show chiral smectic C phases. The mixtures containing 2-chlorosuccinoyl derivatives show thermal instability; however those containing 2-chloroglutaroyl derivatives are stable, but do not show significant values of spontaneous polarization. 相似文献
413.
Ionic Self‐Assembly and Red‐Phosphorescence Properties of a Charged Platinum(II) 8‐Quinolinol Complex Associated with Ammonium‐Based Amphiphiles 下载免费PDF全文
Dr. Franck Camerel Dr. Antoine Vacher Dr. Olivier Jeannin Prof. Joaquín Barberá Dr. Marc Fourmigué 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(52):19149-19158
A series of ionic associates based on the platinum(II) chelate of 5‐sulfo‐8‐quinolinol, [Pt(qS)2]2?, and ammonium‐based amphiphiles is described. At variance with the prototypical neutral complex Pt(q)2 (q=8‐quinolinol), these dianionic fluorophores, functionalized at the periphery with sulfonate groups, can be associated by the ionic self‐assembly approach with various ammonium cations, such as (H2 n+1Cn)2Me2N+ (n=12, 16, 18) or complex ammonium cations carrying three Cn carbon chains (n=12, 14, 16) and an additional amide group. Investigations of their luminescence properties in solution, in the solid state, and, when possible, in thin films revealed that the phosphorescence properties in condensed phases are directly correlated to intermolecular interactions between the luminescent [Pt(qS)2]2? centers. Of particular interest is also the formation of a columnar liquid‐crystalline phase around room temperature (between ?25 and +180 °C), as well as the very good film‐forming ability of some of these fluorophores from organic solvents. 相似文献
414.
Alberto V. Puga Dr. Francesc Teixidor Prof. Dr. Reijo Sillanpää Prof. Dr. Raikko Kivekäs Dr. Massimiliano Arca Dr. Gemma Barberà Dr. Clara Viñas Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(38):9755-9763
The incorporation of iodine atoms onto the boron vertices of the o‐carborane framework causes, according to spectroscopic data, a uniform increase in the acidic character of the Cc? H (Cc= cluster carbon) vertices, whereas the incorporation of methyl groups onto the boron vertices of the o‐carborane framework reduces their acidity. Methyl groups when attached to boron are electron‐withdrawing in boron clusters, whereas iodine atoms bonded to boron act as electron donors. This has been proven on B‐methyl and B‐iodinated o‐carboranes with NMR spectroscopy measurements and DFT calculations of natural bond orbital (NBO) charges, which show a cumulative buildup of positive cluster‐only total charge (CTC) on B‐methyl o‐carboranes and a cumulative buildup of negative cluster‐only total charge for B‐iodinated o‐carboranes. 相似文献
415.
Eduardo Beltrán Emma Cavero Dr. Joaquín Barberá Dr. José Luis Serrano Prof. Anabel Elduque Dr. Raquel Giménez Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9017-9023
Chiral polycatenar 1H‐pyrazoles self‐assemble to form columnar mesophases that are stable at room temperature. X‐ray diffraction and CD studies in the mesophase indicate a supramolecular helical organization consisting of stacked H‐bonded dimers. The liquid‐crystalline compounds reported are 3,5‐bis(dialkoxyphenyl)‐1H‐pyrazoles that incorporate two or four dihydrocitronellyl chiral tails. It can be observed that the grafting of these branched chiral substituents onto the 3,5‐diphenyl‐1H‐pyrazole core has a beneficial role in inducing mesomorphism, because isomeric linear‐chain compounds are not liquid crystalline; this is not the usual scheme of behavior. Furthermore, the molecular chirality is transferred to the columnar mesophase, because preferential helical arrangements are observed. Films of the compounds are luminescent at room temperature and constitute an example of the self‐organization of nondiscoid units into columnar liquid‐crystalline assemblies in which the functional molecular unit transfers its properties to a hierarchically built superstructure. 相似文献
416.
Novel liquid crystal materials based on 3,4-di-n-alkoxybenzoylthiosemicarbazides (3a–h, n = 5–10, 12, 14) were synthesised. The mesomorphic properties of these compounds were characterised and studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. Compound 3a did not show mesomorphic properties; 3b shows a monotropic hexagonal columnar (Colh) phase. Compounds 3c–h display an enantiotropic Colh phase. The mesomorphic properties were found to be dependent on the length of alkoxy side chains. In N,N-dimethylformamide solution, all the compounds displayed a room temperature emission with λmax at 361–332 nm. A thermogravimetric analysis also was performed. 相似文献
417.
Julie B. Trads Katharina Hüll Bryan S. Matsuura Laura Laprell Timm Fehrentz Nicole Grldt Krystian A. Kozek C. David Weaver Nikolaj Klcker David M. Barber Dirk Trauner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15567-15574
Photopharmacology relies on ligands that change their pharmacodynamics upon photoisomerization. Many of these ligands are azobenzenes that are thermodynamically more stable in their elongated trans‐configuration. Often, they are biologically active in this form and lose activity upon irradiation and photoisomerization to their cis‐isomer. Recently, cyclic azobenzenes, so‐called diazocines, have emerged, which are thermodynamically more stable in their bent cis‐form. Incorporation of these switches into a variety of photopharmaceuticals could convert dark‐active ligands into dark‐inactive ligands, which is preferred in most biological applications. This “pharmacological sign‐inversion” is demonstrated for a photochromic blocker of voltage‐gated potassium channels, termed CAL, and a photochromic opener of G protein‐coupled inwardly rectifying potassium (GIRK) channels, termed CLOGO. 相似文献
418.
Dr. Iwona Nierengarten Dr. Sebastiano Guerra Dr. Haifa Ben Aziza Dr. Michel Holler Prof. Rym Abidi Prof. Joaquín Barberá Prof. Robert Deschenaux Dr. Jean‐François Nierengarten 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(18):6185-6189
New liquid‐crystalline pillar[5]arene derivatives have been prepared by grafting first‐generation Percec‐type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc‐shaped structure perfectly suited for self‐organization into a columnar liquid‐crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6‐dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Colh mesophase has been deduced from X‐ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4‐dimethoxypillar[5]arene and 1,6‐dicyanohexane. 相似文献
419.
John J. Monaghan Michael Barber Robert S. Bordoli R. Donald Sedgwick Andrew N. Tyler 《Journal of mass spectrometry : JMS》1982,17(11):569-574
Fast atom bombardment mass spectra of a range of involatile mono and disazo sulphonated dyestuffs are presented. Excellent spectra are obtained for dyestuffs containing up to five sulphonate groups. The fragmentations are discussed with special reference to the ions formed by cleavage of the azo linkage. The negative ion spectra are shown to be superior to those obtained in the positive ion mode. 相似文献
420.
Voltammetric determination of 2-nitrophenol at a bentonite-modified carbon paste electrode 总被引:2,自引:0,他引:2
Ignacio Naranjo Rodriguez Manuel Barea Zamora Juan M. Barberá Salvador Juan A Muñoz Leyva María P. Hernandez-Artiga Jose L. Hidalgo Hidalgo de Cisneros 《Mikrochimica acta》1997,126(1-2):87-92
A bentonite-modified carbon paste electrode has been applied to the determination of 2-nitrophenol by differential pulse voltammmetry. The electrochemical reduction of 2-nitrophenol at –0.8 V is carried out in an artificial sea water-formic acid/sodium formate medium at pH 4. The peak height was found to be dependent on the pH over the range 2–11; the presence of a secondary process was observed in the pH range 8–11. The peak potential showed a dependence on pH, with two linear regions with different slopes. A linear relationship between peak intensity and concentration was obtained in the range 0.07–10 mgl–1, with a detection limit of 0.03 mg 1–1 and a coefficient of variation of 1.3% at 5 mg 1–1. The effects of organic and inorganic species on the 2-nitrophenol determination were studied with a view to testing the resolution of the voltammetric technique. The proposed method has been applied to sea water samples with good results. 相似文献