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831.
Jens P. Eußner Beatrix E. K. Barth Eliza Leusmann Zhiliang You Niklas Rinn Prof. Dr. Stefanie Dehnen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(41):13792-13802
The synthesis of new functionalized organotin‐chalcogenide complexes was achieved by systematic optimization of the reaction conditions. The structures of compounds [(R1, 2Sn)3S4Cl] ( 1 , 2 ), [((R2Sn)2SnS4)2(μ‐S)2] ( 3 ), [(R1, 2Sn)3Se4][SnCl3] ( 4, 5 ), and [Li(thf)n][(R3Sn)(HR3Sn)2Se4Cl] ( 6 ), in which R1=CMe2CH2C(O)Me, R2=CMe2CH2C(NNH2)Me, and R3=CH2CH2COO, are based on defect heterocubane scaffolds, as shown by X‐ray diffraction, 119Sn NMR spectroscopy, and ESI mass spectrometry analyses. Compounds 4 , 5 , and 6 constitute the first examples of defect heterocubane‐type metal‐chalcogenide complexes that are comprised of selenide ligands. Comprehensive DFT calculations prompted us to search for the formal intermediates [(R1SnCl2)2(μ‐S)] ( 7 ) and [(R1SnCl)2(μ‐S)2] ( 8 ), which were isolated and helped to understand the stepwise formation of compounds 1 – 6 . 相似文献
832.
Dr. Esteban Mejía Dr. Shu‐Ping Luo Dr. Michael Karnahl Aleksej Friedrich Dr. Stefanie Tschierlei Dr. Annette‐Enrica Surkus Dr. Henrik Junge Prof. Dr. Serafino Gladiali Prof. Dr. Stefan Lochbrunner Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(47):15972-15978
A series of heteroleptic copper(I) complexes with bidentate $\widehat{PP}$ and $\widehat{NN}$ chelate ligands was prepared and successfully applied as photosensitizers in the light‐driven production of hydrogen, by using [Fe3(CO)12] as a water‐reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble‐metal‐free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton‐reduction systems. Within these experiments, considerably long excited‐state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway. 相似文献
833.
Dr. Nathalie Lunau Dipl.‐Chem. Katrin Seelhorst Dipl.‐Chem. Stefanie Kahl Dr. Kathrin Tscherch Dr. Christina Stacke Prof. Dr. Sascha Rohn Prof. Dr. Joachim Thiem Prof. Dr. Ulrich Hahn Prof. Dr. Chris Meier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17379-17390
Fucosylation is often the final process in glycan biosynthesis. The resulting glycans are involved in a variety of biological processes, such as cell adhesion, inflammation, or tumor metastasis. Fucosyltransferases catalyze the transfer of fucose residues from the activated donor molecule GDP‐β‐L ‐fucose to various acceptor molecules. However, detailed information about the reaction processes is still lacking for most fucosyltransferases. In this work we have monitored α1,3‐fucosyltransferase activity. For both donor and acceptor substrates, the introduction of a fluorescent ATTO dye was the last step in the synthesis. The subsequent conversion of these substrates into fluorescently labeled products by α1,3‐fucosyltransferases was examined by high‐performance thin‐layer chromatography coupled with mass spectrometry as well as dual‐color fluorescence cross‐correlation spectroscopy, which revealed that both fluorescently labeled donor GDP‐β‐L ‐fucose‐ATTO 550 and acceptor N‐acetyllactosamine‐ATTO 647N were accepted by recombinant human fucosyltransferase IX and Helicobacter pylori α1,3‐fucosyltransferase, respectively. Analysis by fluorescence cross‐correlation spectroscopy allowed a quick and versatile estimation of the progress of the enzymatic reaction and therefore this method can be used as an alternative method for investigating fucosyltransferase reactions. 相似文献
834.
Two types of manganese complexes with [Mn4] cores featuring the unusual distorted cube topology are presented, the first of which comprises new modifications of the reported complex [MnIII4(sao)4(saoH)4]·3CHCl3: [Mn4(sao)4(saoH)4]·1.32(C4H10O)·0.43(CH4O) ( 1a ) and [Mn(sao)4(saoH)4]·0.5(CH4O)·0.5(C2H3N) ( 1b ) sao = salicylaldoxime. The second, 0.55[Mn4Cl4(C12H9N2O)4(CH3OH)2(H2O)2]·0.45[Mn4Cl4(C12H9N2O)4(CH3OH)4] ( 2 ), is the first reported case of a {MnII4} core of this topology besides known {MnIII4} compounds. Differences between the {MnII4} and {MnIII4} situation are discussed, and so far overlooked differences in magnetic properties between different {MnIII4} compounds are pointed out. 相似文献
835.
836.
The congener profile of samples contaminated with dioxin and dioxin-like compounds allows identifying sources of contamination. This article studies the statistical methods of congener profile analysis reported in the literature with respect to the reliability of obtained results. The performance of customary analysis methods regarding raw data transformation and applied TEF (toxic equivalency factor) values is discussed. In particular, the method of principal component analysis and k-means cluster is taken as an example and examined in detail. Reasons for occurring inconsistencies such as the dependence of results on raw data transformation and the disregard of measurement uncertainty are described, and it is shown that they also explain inconsistencies in other methods of cluster analysis such as hierarchical cluster analysis and neural networks. It is concluded that these methods cannot be employed to reach court-proof decisions, i.e. decisions which meet court evidentiary standards. An alternative approach to analyzing congener profiles based on mathematical statistics is briefly presented, allowing reliable, court-proof decisions. 相似文献
837.
838.
Siebenberg S Kaysser L Wemakor E Heide L Gust B Kammerer B 《Rapid communications in mass spectrometry : RCM》2011,25(4):495-502
The development of reliable analytic methods, capable of separating mixtures of secondary metabolites as well as providing structural information, is essential for the investigation of secondary metabolites, e.g. from Streptomyces. Here we report a liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method using a triple quadrupole mass analyzer for the structural elucidation of caprazamycins and liposidomycins from culture extracts of the wild-type producer strains. Comparison of the fragmentation patterns in positive as well as in negative ionization mode revealed several characteristic product ions used for identification of six new caprazamycins. Furthermore, a chromatographic method for the purification of nucleosides from cell cultures using a boronic acid gel was adapted for the partial purification of the culture extracts. 相似文献
839.
Stefanie Tschierlei Benjamin Dietzek Michael Karnahl Sven Rau Frederick M. MacDonnell Michael Schmitt Jürgen Popp 《Journal of Raman spectroscopy : JRS》2008,39(5):557-559
Resonance Raman spectroscopy was utilized for the first time to characterize the nature of the 1metal‐to‐ligand charge transfer (MLCT) state of a ruthenium complex containing the redoxactive tetraazatetrapyrido‐pentacene (tatpp) ligand. The presented results show that the long‐wavelength absorption is originating from transitions involving the terminal phenanthroline and the tatpp ligands. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
840.
Christian Kuhnt Stefanie Tschierlei Michael Karnahl Sven Rau Benjamin Dietzek Michael Schmitt Jürgen Popp 《Journal of Raman spectroscopy : JRS》2010,41(9):922-932
We present a combined Raman–density functional theory (DFT) study of novel dipyridophenazine (dppz) derivatives and their Ru–bipyridine complexes. Our results show that the molecular architecture of dppz and its Ru complexes can be considered to consist of two independent moieties, the structural ground state properties of which can be tuned independently by means of side‐specific substitution. These results are expected to be of importance for the design of highly specific dppz‐based DNA sensors. Methodologically, the results presented in this paper highlight the power of a combined Raman–DFT approach to unravel the details of the structural properties of complex molecules. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献