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561.
Andreas Heerwig Ulrike Müller Fabian Nitsche Prof. Dr. Michael Ruck 《无机化学与普通化学杂志》2012,638(10):1462-1467
A new family of quaternary phases with the general sum formula Cu3+δBi5–δSe8–2δX2+2δ (X = Cl, Br) was discovered by slow cooling of high temperature melts. Cu3.58(1)Bi4.42(1)Se6.84(2)Cl3.16(2) (δ = 0.58) and Cu4.52(1)Bi3.48(1)Se4.96(2)Br5.04(2) (δ = 1.52) crystallize isostructural in the orthorhombic space group type Pnnm with a = 1332.3(1)/1340.2(3) pm, b = 1683.7(2)/1717.2(1) pm, and c = 406.2(1)/407.1(2) pm. The new structure type resembles in some aspects the hollandite as well as the pavonite type. A framework of face‐ and edge‐sharing anion polyhedra around Bi3+ cations hosts Cu+ cations. The characteristic motif is an infinite band of polyhedra that has the width of five polyhedra, with three octahedra being enclosed by capped trigonal prisms. The octahedrally coordinated Bi3+ cations are partially substituted by Cu+ (in octahedra faces), while Se2– anions are replaced by X–. The sulfide iodide Cu3.33(2)Bi2S3.33(2)I2.67(2) crystallizes in the monoclinic space group C2/m with a = 2803.6(9) pm, b = 409.9(1) pm, c = 1058.0(3) pm, and β = 110.68(2)°. Double strands of face‐sharing [BiS1/1S2/2I4/4] as well as [BiS3/3I2/2(S0.33/I0.67)2/2] polyhedra run along [010]. In between them, the Cu+ cations are spread over numerous closely spaced sites. They define a ladder‐shaped continuous path for ion conduction along [010]. 相似文献
562.
M. Sc. Lotta Turunen M. Sc. Ulrike Warzok Dr. Rakesh Puttreddy Dr. Ngong Kodiah Beyeh Prof. Christoph A. Schalley Acad. Prof. Kari Rissanen 《Angewandte Chemie (International ed. in English)》2016,55(45):14033-14036
Two [N???I+???N] halogen‐bonded dimeric capsules using tetrakis(3‐pyridyl)ethylene cavitands with different lower rim alkyl chains are synthesized and analyzed in solution and the gas phase. These first examples of symmetrical dimeric capsules making use of the iodonium ion (I+) as the main connecting module are characterized by 1H NMR spectroscopy, diffusion ordered NMR spectroscopy (DOSY), electrospray ionization mass spectrometry (ESI‐MS), and ion mobility‐mass spectrometry (TW‐IMS) experiments. The synthesis and effective halogen‐bonded dimerization proceeds through analogous dimeric capsules with [N???Ag+???N] binding motifs as the intermediates as evidenced by the X‐ray structures of (CH2Cl2)2@[ 3 a 2?Ag4?(H2O)2?OTs4] and (CH2Cl2)2@[ 3 a 2?Ag4?(H2O)4?OTs4], two structurally different capsules. 相似文献
563.
Fast X‐ray microfluorescence imaging with submicrometer‐resolution integrating a Maia detector at beamline P06 at PETRA III 下载免费PDF全文
Ulrike Boesenberg Christopher G. Ryan Robin Kirkham D. Peter Siddons Matthias Alfeld Jan Garrevoet Teresa Núñez Thorsten Claussen Thorsten Kracht Gerald Falkenberg 《Journal of synchrotron radiation》2016,23(6):1550-1560
The high brilliance of third‐generation synchrotron sources increases the demand for faster detectors to utilize the available flux. The Maia detector is an advanced imaging scheme for energy‐dispersive detection realising dwell times per image‐pixel as low as 50 µs and count rates higher than 10 × 106 s?1. In this article the integration of such a Maia detector in the Microprobe setup of beamline P06 at the storage ring PETRA III at the Deutsches Elektronen‐Synchrotron (DESY) in Hamburg, Germany, is described. The analytical performance of the complete system in terms of rate‐dependent energy resolution, scanning‐speed‐dependent spatial resolution and lower limits of detection is characterized. The potential of the Maia‐based setup is demonstrated by key applications from materials science and chemistry, as well as environmental science with geological applications and biological questions that have been investigated at the P06 beamline. 相似文献
564.
Ehrlich G Hassfeld J Eggert U Kalesse M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2232-2247
Tedanolide, which was isolated by Schmitz in 1984 from the marine sponge Tedania ignis, is a highly cytotoxic macrolide leading to strong growth inhibition of P338 tumor cells in bioassays. A unique structural feature of the known tedanolides is the primary hydroxyl group incorporated in the macrolactone. This unusual motif for macrolactones originated from PKS biosynthesis might arise through lactonizations others than those derived by the thioesterase reaction. First experimental data that support this hypothesis and reflect the inherent preference of PKS-induced macrolactonization were obtained during this synthesis. The inherent preference for the formation of a 14-membered macrocyclization is discussed together with the pivotal steps in the synthesis. 相似文献
565.
Andreas Marc Palmer Vittoria Chiesa Hans Christof Holst Jacques Le Paih Antonio Zanotti-Gerosa Ulrike Nettekoven 《Tetrahedron: Asymmetry》2008,19(17):2102-2110
The asymmetric hydrogenation of complex heterocyclic ketones 1 in the presence of the novel catalyst RuCl2[(S)-Xyl-P-Phos][(S)-DAIPEN] and a base afforded the corresponding alcohols 2 in good enantiomeric purity. The outcome of the reaction depended on the substitution pattern of the ketone and the stoichiometry of the base. After optimization of the reaction conditions, the pure alcohols 2a and 2b were isolated in good yield (>70%) and enantiomeric purity (>93% ee) and used as key intermediates for the synthesis of the pharmaceutically active 3,6,7,8-tetrahydrochromeno[7,8-d]imidazoles 3a and 3b. 相似文献
566.
Paizs C Bartlewski-Hof U Rétey J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(10):2805-2811
Pyrogallol-phloroglucinol transhydroxylase from Pelobacter acidigallici, a molybdopterin-containing enzyme, catalyzes a key reaction in the anaerobic degradation of aromatic compounds. In vitro, the enzymatic reaction requires 1,2,3,5-tetrahydroxybenzene as a cocatalyst and the transhydroxylation occurs without exchange with hydroxy groups from water. To test our previous proposal that the transfer of the hydroxy group occurs via 2,4,6,3',4',5'-hexahydroxydiphenyl ether as an intermediate, we synthesized this compound and investigated its properties. We also describe the synthesis and characterization of 3,4,5,3',4',5'-hexahydroxydiphenyl ether. Both compounds could substitute for the cocatalyst in vitro. This indicates that the diphenyl ethers can intrude into the active site and initiate the catalytic cycle. Recently, the X-ray crystal structure of the transhydroxylase (TH) was published16 and it supports the proposed mechanism of hydroxy-group transfer. 相似文献
567.
568.
569.
Alcaraz G Helmstedt U Clot E Vendier L Sabo-Etienne S 《Journal of the American Chemical Society》2008,130(39):12878-12879
Starting from RuHCl(H2)(PCy3)2, a terminal ruthenium mesitylborylene complex was obtained via double B-H bond activation of mesitylborane and concomitant release of dihydrogen, such a process being remarkably reversible. 相似文献
570.
Salzner U 《The journal of physical chemistry. A》2008,112(24):5458-5466
The nature of the charge carriers in conducting organic polymers (COPs) is a long standing problem. Polythiophene is one of the prototypes of COPs and intensively studied. Because doping leads to changes in UV/vis spectra that are characteristic of the absorbing species, UV/vis spectra of charged thiophene oligomers with up to 25 rings were calculated with time-dependent density functional theory. The credibility of the method was established by comparing the results with a variety of theoretical levels and with experiment. Effects due to counterions (Cl 3 (-)) and solvent (CH 2Cl 2) were examined. It was found that TDDFT employing hybrid functionals is accurate enough to distinguish the absorbing species. The findings offer an explanation for the experimentally observed difference in UV-spectra of medium-sized and long oligomers upon doping. As chain lengths of the oligomers increase and energy levels get closer, configuration interaction leads to additional absorption peaks in the high energy sub-band region (at around 1.5-2.5 eV). Thus, long oligomers do not behave differently from medium-sized ones upon doping, only their spectra are different. At low doping levels radical cations (polarons) are produced. At higher doping levels, dications that harbor weakly interacting polaron pairs are formed. Bipolarons are predicted only on very short chains or at high doping levels. There is no bipolaron binding energy and disproportionation of monocations into dications and neutral species is energetically unfavorable. 相似文献