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251.
252.
FP Binder K Lemme RC Preston B Ernst 《Angewandte Chemie (International ed. in English)》2012,51(29):7327-7331
Organized and released: Sialyl Lewis(x) (sLe(x)) represents a "pre-organized water oligomer", that is, a surrogate for clustered water molecules attached to a scaffold. The impetus for sLe(x) binding to E-selectin is shown to be the high degree of pre-organization allowing an array of directed hydrogen bonds, and the entropic benefit of the release of water molecules from the large binding interface to bulk water (see picture). 相似文献
253.
Atomic‐Resolution Three‐Dimensional Structure of Amyloid β Fibrils Bearing the Osaka Mutation 下载免费PDF全文
Dr. Anne K. Schütz Dr. Toni Vagt Dr. Matthias Huber Dr. Oxana Y. Ovchinnikova Riccardo Cadalbert Dr. Joseph Wall Prof. Dr. Peter Güntert Dr. Anja Böckmann Prof. Dr. Rudi Glockshuber Prof. Dr. Beat H. Meier 《Angewandte Chemie (International ed. in English)》2015,54(1):331-335
Despite its central importance for understanding the molecular basis of Alzheimer's disease (AD), high‐resolution structural information on amyloid β‐peptide (Aβ) fibrils, which are intimately linked with AD, is scarce. We report an atomic‐resolution fibril structure of the Aβ1‐40 peptide with the Osaka mutation (E22Δ), associated with early‐onset AD. The structure, which differs substantially from all previously proposed models, is based on a large number of unambiguous intra‐ and intermolecular solid‐state NMR distance restraints. 相似文献
254.
De Novo 3D Structure Determination from Sub‐milligram Protein Samples by Solid‐State 100 kHz MAS NMR Spectroscopy 下载免费PDF全文
Dr. Vipin Agarwal Susanne Penzel Kathrin Szekely Riccardo Cadalbert Emilie Testori Andres Oss Jaan Past Prof. Ago Samoson Prof. Matthias Ernst Dr. Anja Böckmann Prof. Beat H. Meier 《Angewandte Chemie (International ed. in English)》2014,53(45):12253-12256
Solid‐state NMR spectroscopy is an emerging tool for structural studies of crystalline, membrane‐associated, sedimented, and fibrillar proteins. A major limitation for many studies is still the large amount of sample needed for the experiments, typically several isotopically labeled samples of 10–20 mg each. Here we show that a new NMR probe, pushing magic‐angle sample rotation to frequencies around 100 kHz, makes it possible to narrow the proton resonance lines sufficiently to provide the necessary sensitivity and spectral resolution for efficient and sensitive proton detection. Using restraints from such spectra, a well‐defined de novo structure of the model protein ubiquitin was obtained from two samples of roughly 500 μg protein each. This proof of principle opens new avenues for structural studies of proteins available in microgram, or tens of nanomoles, quantities that are, for example, typically achieved for eukaryotic membrane proteins by in‐cell or cell‐free expression. 相似文献
255.
Individual transitions of magnetically equivalent spin systems such as methyl groups residing on isotropically tumbling molecules in solution usually cannot be observed as multiplet-split NMR lines. We propose a pair of NMR experiments, 2D [13C,1Halphaalpha]Methyl and [13C,1Hbetabeta]Methyl HSQC, to overcome this limitation and enable direct and selective observation of individual 1H transitions in 13C-labeled methyl spin systems. Immediate applications include quantitative measurements of 1H-1H residual dipolar couplings (RDC) and cross-correlated relaxation between 1H chemical shift anisotropy and 1H-1H dipole-dipole interactions. The use of the experiments for the measurement of RDCs is demonstrated with two proteins, one weakly aligned by means of Pf1 phages and the other using a naturally present paramagnetic heme group. 相似文献
256.
Günther-Leopold I Kivel N Kobler Waldis J Wernli B 《Analytical and bioanalytical chemistry》2008,390(2):503-510
Isotopic analyses of radioactive materials such as irradiated nuclear fuel are of major importance for the optimization of
the nuclear fuel cycle and for safeguard aspects. Among the mass-spectrometric techniques available, inductively coupled plasma
mass spectrometry (ICP-MS) and thermal ionization mass spectrometry are the most frequently applied methods for nuclear applications.
Because of the low detection limits, the ability to analyze the isotopic composition of the elements and the applicability
of the techniques for measuring stable as well as radioactive nuclides with similar sensitivity, both mass-spectrometric techniques
are an excellent amendment to classical radioactivity counting methods. The paper describes selected applications of multicollector
ICP-MS in combination with chromatographic separation techniques and laser ablation for the isotopic analysis of irradiated
nuclear fuels. The advantages and limitations of the selected analytical technique for the characterization of such a heterogeneous
sample matrix are discussed. 相似文献
257.
Dmitry Chernyshov Marc Hostettler Hans‐Beat Bürgi Karl W. Trnroos 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(10):m450-m452
The octahedral cis and trans isomers of dichlorobis(2‐picolylamine)iron(II), [FeCl2(C6H8N2)2], co‐crystallize in a 1:1 ratio. The cis isomer lies on a twofold axis, whereas the trans isomer lies on an inversion centre. The structure is fully ordered, with both Fe atoms in a pure high‐spin state. The Fe, Cl and N(H2) atoms of both isomers lie in the same plane, allowing all Cl and amine H atoms to be engaged in extensive two‐dimensional hydrogen bonding. The hydrogen‐bonded layers are interconnected through π–π interactions between the pyridine rings. Searches in the Cambridge Structural Database uncover very few examples of such isomer co‐existence. 相似文献
258.
Alexander A. Malär Dr. Shunxi Dong Dr. Gerald Kehr Prof. Gerhard Erker Prof. Beat H. Meier Dr. Thomas Wiegand 《Chemphyschem》2019,20(5):672-679
Proton spectroscopy in solid-state NMR on catalytic materials offers new opportunities in structural characterization, in particular of reaction products of catalytic reactions such as hydrogenation reactions. Unfortunately, the 1H NMR line widths in magic-angle spinning solid-state spectra are often broadened by an incomplete averaging of 1H-1H dipolar couplings. We herein discuss two model compounds, namely the H2-splitting products of two phosphane-borane Frustrated Lewis Pairs (FLPs), to study potentials and limitations of proton solid-state NMR experiments employing magic-angle spinning frequencies larger than 100 kHz at a static magnetic field strength of 20.0 T. The 1H lines are homogeneously broadened as illustrated by spin-echo decay experiments. We study two structurally similar materials which however show significant differences in 1H line widths which we explain by differences in their 1H-1H dipolar networks. We discuss the benefit of fast MAS experiments up to 110 kHz to detect the resonances of the H+/H− pair in the hydrogenation products of FLPs. 相似文献
259.
Karl W. Krmer Ralph Schenker Jürg Hauser Hgni Weihe Hans U. Güdel Hans‐Beat Bürgi 《无机化学与普通化学杂志》2001,627(11):2511-2516
The syntheses and X‐ray structure determinations of single crystals and powders are reported for the compounds (Et4N)3M2F9 (M = V3+, Cr3+, Fe3+). The compounds are isostructural and represent a new structure type for A3M2X9 compounds. They crystallize in the hexagonal space group P63/m with Z = 2. Their lattice parameters are (Et4N)3V2F9: a = 13.3017(3), c = 10.7714(2) Å; (Et4N)3Cr2F9: a = 13.2691(3), c = 10.7148(3) Å; and (Et4N)3Fe2F9: a = 13.3040(3), c = 10.7650(3) Å. 相似文献
260.
Structural Studies of Self‐Assembled Subviral Particles: Combining Cell‐Free Expression with 110 kHz MAS NMR Spectroscopy 下载免费PDF全文
Guillaume David Dr. Marie‐Laure Fogeron Maarten Schledorn Roland Montserret Uta Haselmann Susanne Penzel Dr. Aurélie Badillo Dr. Lauriane Lecoq Prof. Patrice André Prof. Michael Nassal Prof. Ralf Bartenschlager Prof. Beat H. Meier Dr. Anja Böckmann 《Angewandte Chemie (International ed. in English)》2018,57(17):4787-4791
Viral membrane proteins are prime targets in combatting infection. Still, the determination of their structure remains a challenge, both with respect to sample preparation and the need for structural methods allowing for analysis in a native‐like lipid environment. Cell‐free protein synthesis and solid‐state NMR spectroscopy are promising approaches in this context, the former with respect to its great potential in the native expression of complex proteins, and the latter for the analysis of membrane proteins in lipids. Herein, we show that milligram amounts of the small envelope protein of the duck hepatitis B virus (DHBV) can be produced by cell‐free expression, and that the protein self‐assembles into subviral particles. Proton‐detected 2D NMR spectra recorded at a magic‐angle‐spinning frequency of 110 kHz on <500 μg protein show a number of isolated peaks with line widths comparable to those of model membrane proteins, paving the way for structural studies of this protein that is homologous to a potential drug target in HBV infection. 相似文献