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571.
Park JW Park SR Han AR Ban YH Yoo YJ Kim E Kim BS Sohng JK Yoon YJ 《Journal of chromatography. A》2011,1218(16):2284-2291
Microbial cultures produce complex and potentially interesting mixtures of biosynthetic intermediates and derivatives of metabolites. These mixtures' reliable identification is important and so too is the development of techniques for their analysis. Here, a simple and highly selective method of detecting the biosynthetic congeners involved in the pentangular polyphenol pradimicin (PR) pathway from Actinomadura hibisca fermentation was developed. Solid-phase extraction (SPE) cleanup using an OASIS HLB cartridge was a simple and reliable tool for the extraction of PRs from a fermentation broth. The separation of each natural PR analog--eluted with a gradient system of aqueous acetonitrile through a reversed-phase C(18) column containing ammonium acetate and acetic acid as additives--allowed their simultaneous profiling. The combined use of SPE cleanup and chromatographic separation, coupled with electrospray ionization-tandem mass spectrometry (ESI-MS/MS) detection was demonstrated to be sufficiently accurate and reliable to analyze the natural PR analogs produced from A. hibisca. Ten natural PRs were identified: four alanine-containing (PRA, PRC, PRL, and PRB), two glycine-substituted (PRD and PRE), and four serine-substituted (PRFA-1, PRFA-2, PRFL, and PRFB). This report demonstrates the first use of both SPE cleanup and HPLC-ESI-MS/MS to profile a wide range of structurally closely related PRs in a bacterial fermentation broth. 相似文献
572.
Matthias Ferger Dr. Željka Ban Ivona Krošl Dr. Sanja Tomić Lena Dietrich Sabine Lorenzen Dr. Florian Rauch Dr. Daniel Sieh Dr. Alexandra Friedrich Dr. Stefanie Griesbeck Dr. Adriana Kenđel Prof. Dr. Snežana Miljanić Dr. Ivo Piantanida Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5142-5159
We report four new luminescent tetracationic bis-triarylborane DNA and RNA sensors that show high binding affinities, in several cases even in the nanomolar range. Three of the compounds contain substituted, highly emissive and structurally flexible bis(2,6-dimethylphenyl-4-ethynyl)arene linkers ( 3 : arene=5,5′-2,2′-bithiophene; 4 : arene=1,4-benzene; 5 : arene=9,10-anthracene) between the two boryl moieties and serve as efficient dual Raman and fluorescence chromophores. The shorter analogue 6 employs 9,10-anthracene as the linker and demonstrates the importance of an adequate linker length with a certain level of flexibility by exhibiting generally lower binding affinities than 3 – 5 . Pronounced aggregation–deaggregation processes are observed in fluorimetric titration experiments with DNA for compounds 3 and 5 . Molecular modelling of complexes of 5 with AT-DNA, suggest the minor groove as the dominant binding site for monomeric 5 , but demonstrate that dimers of 5 can also be accommodated. Strong SERS responses for 3 – 5 versus a very weak response for 6 , particularly the strong signals from anthracene itself observed for 5 but not for 6 , demonstrate the importance of triple bonds for strong Raman activity in molecules of this compound class. The energy of the characteristic stretching vibration of the C≡C bonds is significantly dependent on the aromatic moiety between the triple bonds. The insertion of aromatic moieties between two C≡C bonds thus offers an alternative design for dual Raman and fluorescence chromophores, applicable in multiplex biological Raman imaging. 相似文献
573.
<正>Two new taraxastane-type triterpenoids,20-taraxastene-3β,12β,16β-triol 1 and 3β-feruloyloxy-20-taraxastene-16β,28-diol 2, were isolated from the fruit of Cicuta virosa L.var latisecta Celak.There structures were elucidated by ESI-MS,1D- and 2D-NMR spectroscopic methods. 相似文献
574.
Nguyen Xuan Nhiem Phan Van Kiem Chau Van Minh Ninh Khac Ban Nguyen Xuan Cuong Le Minh Ha Bui Huu Tai Tran Hong Quang Nguyen Huu Tung Young Ho Kim 《Magnetic resonance in chemistry : MRC》2010,48(5):392-396
The chemical study of Momordica charantia fruits led to the isolation of three new cucurbitane triterpene glycosides, momordicosides U, V, and W (1–3). The structures of these compounds were determined to be (19R, 23R)‐5β, 19‐epoxy‐19‐methoxycucurbita‐6,24‐diene‐3β, 23‐diol 3‐O‐β‐D‐allopyranoside (1), (23R)‐5β, 19‐epoxycucurbita‐6,24‐diene‐3β, 23‐diol 3‐O‐β‐D‐allopyranoside (2), and (19R)‐5β, 19‐epoxy‐19,25‐dihydroxycucurbita‐6,23(E)‐diene‐3β‐ol 3‐O‐β‐D‐glucopyranoside (3), by chemical and spectroscopic methods. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
575.
Jingyun Ren Xu Ban Xin Zhang Siu Min Tan Richmond Lee Choon‐Hong Tan 《Angewandte Chemie (International ed. in English)》2020,59(23):9055-9058
We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium‐catalyzed kinetic resolution (KR) of racemic tertiary bromides under base‐free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a SN2X pathway. 相似文献
576.
Double Strain‐Promoted Macrocyclization for the Rapid Selection of Cell‐Active Stapled Peptides 下载免费PDF全文
Dr. Maxim Rossmann Dr. Ban Xiong Tan Dr. Peterson de Andrade Dr. Yaw Sing Tan Dr. Chandra Verma Dr. Grahame J. McKenzie Prof. Ashok R. Venkitaraman Dr. Marko Hyvönen Prof. David R. Spring 《Angewandte Chemie (International ed. in English)》2015,54(51):15410-15413
Peptide stapling is a method for designing macrocyclic alpha‐helical inhibitors of protein–protein interactions. However, obtaining a cell‐active inhibitor can require significant optimization. We report a novel stapling technique based on a double strain‐promoted azide–alkyne reaction, and exploit its biocompatibility to accelerate the discovery of cell‐active stapled peptides. As a proof of concept, MDM2‐binding peptides were stapled in parallel, directly in cell culture medium in 96‐well plates, and simultaneously evaluated in a p53 reporter assay. This in situ stapling/screening process gave an optimal candidate that showed improved proteolytic stability and nanomolar binding to MDM2 in subsequent biophysical assays. α‐Helicity was confirmed by a crystal structure of the MDM2‐peptide complex. This work introduces in situ stapling as a versatile biocompatible technique with many other potential high‐throughput biological applications. 相似文献
577.
Sampling of Glycan‐Bound Conformers by the Anti‐HIV Lectin Oscillatoria agardhii agglutinin in the Absence of Sugar 下载免费PDF全文
Marta G. Carneiro Leonardus M. I. Koharudin David Ban T. Michael Sabo Pablo Trigo‐Mourino Adam Mazur Christian Griesinger Angela M. Gronenborn Donghan Lee 《Angewandte Chemie (International ed. in English)》2015,54(22):6462-6465
Lectins from different sources have been shown to interfere with HIV infection by binding to the sugars of viral‐envelope glycoproteins. Three‐dimensional atomic structures of a number of HIV‐inactivating lectins have been determined, both as free proteins and in glycan‐bound forms. However, details on the mechanism of recognition and binding to sugars are elusive. Herein we focus on the anti‐HIV lectin OAA from Oscillatoria agardhii: We show that in the absence of sugars in solution, both the sugar‐free and sugar‐bound protein conformations that were observed in the X‐ray crystal structures exist as conformational substates. Our results suggest that glycan recognition occurs by conformational selection within the ground state; this model differs from the popular “excited‐state” model. Our findings provide further insight into molecular recognition of the major receptor on the HIV virus by OAA. These details can potentially be used for the optimization and/or development of preventive anti‐HIV therapeutics. 相似文献
578.
Kazuo Soga Takashi Arai Ban The Hoang Toshiya Uozumi 《Macromolecular rapid communications》1995,16(12):905-911
Three kinds of zirconocene catalysts, supported on polysiloxanes substituted with methylindenyl, methyl-fluorenyl and two indenyl groups, respectively, were prepared and applied to propene and ethylene polymerizations using methylaluminoxane as cocatalyst. Both the activity and stereospecificity of these catalysts were found to lie between those of corresponding homogeneous and SiO2-supported catalysts. Surprisingly, all the catalysts gave a mixture of atactic and isotactic poly(propylene), plausible reasons for which are briefly discussed. 相似文献
579.
4,4′‐Bis(3‐N‐methoxyformyl thioureido)‐diphenyloxide was prepared via reaction of 4,4′‐diaminodiphenyl alter with potassium sulfocyanate and ethyl chloroacetate in ethyl acetate. The single crystal of the title compound was cultured by slow evaporation method at room temperature. The crystal structure was determined with X‐ray diffractometer. It is a monoclinic crystal, space group C2/c with a=0.95911(19) nm, b=0.75922(15) nm, c=2.7161(5) nm, α=90°, β=97.675 (3) °, γ=90°, V=1.9601(7) nm3, Z=4, Dc=1.472 g·cm−3, F(000) =904, µ=0.311 cm−1, R1=0.0367, wR2=0.1408. The specific heat capacity of the title compound was determined with continuous Cp mode of mircocalorimeter. The thermal behavior of the title compound was studied under a non‐isothermal condition by DSC method. 相似文献
580.
N-Benzylanilines were designed and synthesized as vascular endothelial growth factor (VEGF)-2 inhibitors using de novo drug design systems based on the X-ray structure of VEGFR-2 kinase domain. Among compounds synthesized, compound showed the most potent inhibitory activity toward VEGFR-2 (KDR) tyrosine kinase and its IC(50) value was 0.57 microM. 相似文献