全文获取类型
收费全文 | 2838篇 |
免费 | 261篇 |
国内免费 | 14篇 |
专业分类
化学 | 2120篇 |
晶体学 | 8篇 |
力学 | 60篇 |
数学 | 414篇 |
物理学 | 511篇 |
出版年
2023年 | 52篇 |
2022年 | 35篇 |
2021年 | 118篇 |
2020年 | 166篇 |
2019年 | 186篇 |
2018年 | 83篇 |
2017年 | 69篇 |
2016年 | 198篇 |
2015年 | 149篇 |
2014年 | 160篇 |
2013年 | 193篇 |
2012年 | 274篇 |
2011年 | 266篇 |
2010年 | 154篇 |
2009年 | 127篇 |
2008年 | 194篇 |
2007年 | 155篇 |
2006年 | 148篇 |
2005年 | 97篇 |
2004年 | 59篇 |
2003年 | 30篇 |
2002年 | 30篇 |
2001年 | 25篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
1932年 | 2篇 |
1928年 | 1篇 |
排序方式: 共有3113条查询结果,搜索用时 31 毫秒
951.
Sebastian Pomplun Christopher R. Shugrue Adeline M. Schmitt Carly K. Schissel Charlotte E. Farquhar Bradley L. Pentelute 《Angewandte Chemie (International ed. in English)》2020,59(28):11566-11572
Capture and release of peptides is often a critical operation in the pathway to discovering materials with novel functions. However, the best methods for efficient capture impede facile release. To overcome this challenge, we report linkers based on secondary amino alcohols for the release of peptides after capture. These amino alcohols are based on serine (seramox) or isoserine (isoseramox) and can be incorporated into peptides during solid‐phase peptide synthesis through reductive amination. Both linkers are quantitatively cleaved within minutes under NaIO4 treatment. Cleavage of isoseramox produced a native peptide N‐terminus. This linker also showed broad substrate compatibility; incorporation into a synthetic peptide library resulted in the identification of all sequences by nanoLC‐MS/MS. The linkers are cell compatible; a cell‐penetrating peptide that contained this linker was efficiently captured and identified after uptake into cells. These findings suggest that such secondary amino alcohol based linkers might be suitable tools for peptide‐discovery platforms. 相似文献
952.
Thorsten Lückerath Kaloian Koynov Sebastian Loescher Colette J. Whitfield Lutz Nuhn Andreas Walther Christopher Barner‐Kowollik David Y. W. Ng Tanja Weil 《Angewandte Chemie (International ed. in English)》2020,59(36):15474-15479
Nanostructures derived from amphiphilic DNA–polymer conjugates have emerged prominently due to their rich self‐assembly behavior; however, their synthesis is traditionally challenging. Here, we report a novel platform technology towards DNA–polymer nanostructures of various shapes by leveraging polymerization‐induced self‐assembly (PISA) for polymerization from single‐stranded DNA (ssDNA). A “grafting from” protocol for thermal RAFT polymerization from ssDNA under ambient conditions was developed and utilized for the synthesis of functional DNA–polymer conjugates and DNA–diblock conjugates derived from acrylates and acrylamides. Using this method, PISA was applied to manufacture isotropic and anisotropic DNA–polymer nanostructures by varying the chain length of the polymer block. The resulting nanostructures were further functionalized by hybridization with a dye‐labelled complementary ssDNA, thus establishing PISA as a powerful route towards intrinsically functional DNA–polymer nanostructures. 相似文献
953.
B. Sc. Jule Kristin Philipp B. Sc. Sebastian Fritsch Prof. Dr. Ralf Ludwig 《Chemphyschem》2020,21(21):2411-2416
Cyclic octamers are well-known structural motifs in chemistry, biology and physics. These include covalently bound cyclic octameric sulphur, cylic octa-alkanes, cyclo-octameric peptides as well as hydrogen-bonded ring clusters of alcohols. In this work, we show that even calculated cyclic octamers of hydroxy-functionalized pyridinium cations with a net charge Q=+8e are kinetically stable. Eight positively charged cations are kept together by hydrogen bonding despite the strong Coulomb repulsive forces. Sufficiently long hydroxy-octyl chains prevent “Coulomb explosion” by increasing the distance between the positive charges at the pyridinium rings, reducing the Coulomb repulsion and thus strengthen hydrogen bonds between the OH groups. The eightfold positively charged cyclic octamer shows spectroscopic properties similar to those obtained for hydrogen-bonded neutral cyclic octamers of methanol. Thus, the area of the hydrogen bonded OH ring represents a ‘molecular island’ within an overall cationic environment. Although not observable, the spectroscopic properties and the correlated NBO parameters of the calculated cationic octamer support the detection of smaller cationic clusters in ionic liquids, which we observed despite the competition with ion pairs wherein attractive Coulomb forces enhance hydrogen bonding between cation and anion. 相似文献
954.
Ştefan Ţălu Sebastian Stach Joana Zaharieva Miroslava Getsova Denitsa Elenkova Maria Milanova 《International Journal of Polymer Analysis and Characterization》2014,19(7):648-660
The aim of this study was to investigate by atomic force microscopy and multifractal analysis the three-dimensional (3-D) of surface micromorphology of the complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methyl)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(C25H15O7)3 · 5H2O immobilized in transparent SiO2-based films by a simple casting technique. The 3-D surfaces contain irregularities of various orders spread on the surface due to the intrinsic method of surface preparation. We found that the micromorphology of all analyzed samples has multifractal characteristics. The generalized dimension D q and the singularity spectrum f(α) provided quantitative values that describe the degree of heterogeneity in the 3-D surface geometry at nanometer scale. The results showed that the larger the spectrum width Δα (Δα = α max ? α min ) of the multifractal spectra f(α), the more nonuniform is the surface micromorphology. These results demonstrate that multifractal analysis is a more precise and reliable tool for quantitative characterization of 3-D surface micromorphology. 相似文献
955.
Ramona Samba Kai Fuchsberger Ilona Matiychyn Sebastian Epple Lydia Kiesel Alfred Stett Wolfgang Schuhmann Martin Stelzle 《Electroanalysis》2014,26(3):548-555
In this work, composite microelectrodes from poly(3,4‐ethylenedioxythiophene) (PEDOT) and carbon nanotubes (CNT) are characterized as electrochemical sensing material for neurotransmitters. Dopamine can be detected using square wave voltammetry at these microelectrodes. The CNTs improve the sensitivity by a factor of two. In addition, the selectivity towards dopamine in the presence of ascorbic acid and uric acid was examined. While both electrodes, PEDOT and PEDOT‐CNT are able to detect all measured concentrations of dopamine in the presence of uric acid, small concentrations of dopamine and ascorbic acid are only distinguishable at PEDOT‐CNT electrodes. Changing the pH has a strong influence on the selectivity. Moreover, it is possible to detect concentrations as low as 1 µM dopamine in complex cell culture medium. Finally, other catecholamines like serotonin, epinephrine, norepinephrine and L ‐dopa are also electrochemically detectable at PEDOT‐CNT microelectrodes. 相似文献
956.
Filip Kaftan Vladimír Vrkoslav Philipp Kynast Purva Kulkarni Sebastian Böcker Josef Cvačka Markus Knaden Aleš Svatoš 《Journal of mass spectrometry : JMS》2014,49(3):223-232
The spatial distribution of neutral lipids and semiochemicals on the surface of six‐day‐old separately reared naive Drosophila melanogaster flies has been visualized and studied using matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry and laser‐assisted desorption/ionization (LDI)‐TOF imaging (MSI). Metal targets were designed for two‐dimensional MSI of the surface of 3‐D biological objects. Targets with either simple grooves or profiled holes designed to accurately accommodate the male and female bodies were fabricated. These grooves and especially holes ensured correct height fixation and spatial orientation of the flies on the targets after matrix application and sample drying. For LDI‐TOF to be used, the flies were arranged into holes and fixed to a plane of the target using fast‐setting glue. In MALDI‐TOF mode, the flies were fixed as above and sprayed with a lithium 2,5‐dihydroxybenzoate matrix using up to 100 airbrush spray cycles. The scanning electron microscopy images revealed that the deposits of matrix were homogenous and the matrix formed mostly into the clusters of crystals (40–80 µm) that were separated from each other by an uncovered cuticle surface (30–40 µm). The MSI using target with profiled holes provided superior results to the targets with simple grooves, eliminating the ion suppression/mass deviation due to the 3‐D shape of the flies. Attention was paid to neutral lipids and other compounds including the male anti‐attractant 11‐cis‐vaccenyl acetate for which the expected distribution with high concentration on the tip of the male abdomen was confirmed. The red and blue mass shift (PlusMinus1 colour scale) was observed associated with mass deviation predominantly between ±0.2 and 0.3 Da. We use in‐house developed software for mass recalibration, to eliminate the mass deviation effects and help with the detection of low‐intensity mass signals. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
957.
Dr. Ümit Akbey Dr. Andrew J. Nieuwkoop Dr. Sebastian Wegner Anja Voreck Dr. Britta Kunert Dr. Priyanga Bandara Dr. Frank Engelke Prof. Dr. Niels Chr. Nielsen Prof. Dr. Hartmut Oschkinat 《Angewandte Chemie (International ed. in English)》2014,53(9):2438-2442
1H‐detected magic‐angle spinning NMR experiments facilitate structural biology of solid proteins, which requires using deuterated proteins. However, often amide protons cannot be back‐exchanged sufficiently, because of a possible lack of solvent exposure. For such systems, using 2H excitation instead of 1H excitation can be beneficial because of the larger abundance and shorter longitudinal relaxation time, T1, of deuterium. A new structure determination approach, “quadruple‐resonance NMR spectroscopy”, is presented which relies on an efficient 2H‐excitation and 2H‐13C cross‐polarization (CP) step, combined with 1H detection. We show that by using 2H‐excited experiments better sensitivity is possible on an SH3 sample recrystallized from 30 % H2O. For a membrane protein, the ABC transporter ArtMP in native lipid bilayers, different sets of signals can be observed from different initial polarization pathways, which can be evaluated further to extract structural properties. 相似文献
958.
Dr. Sebastian Götze Dr. Nahid Azzouz Dr. Yu‐Hsuan Tsai Prof. Dr. Uwe Groß Anika Reinhardt Dr. Chakkumkal Anish Prof. Dr. Peter H. Seeberger Dr. Daniel Varón Silva 《Angewandte Chemie (International ed. in English)》2014,53(50):13701-13705
Around 2 billion people worldwide are infected with the apicomplexan parasite Toxoplasma gondii which induces a variety of medical conditions. For example, primary infection during pregnancy can result in fetal death or mental retardation of the child. Diagnosis of acute infections in pregnant women is challenging but crucially important as the drugs used to treat T. gondii infections are potentially harmful to the unborn child. Better, faster, more reliable, and cheaper means of diagnosis by using defined antigens for accurate serological tests are highly desirable. Synthetic pathogen‐specific glycosylphosphatidylinositol (GPI) glycan antigens are diagnostic markers and have been used to distinguish between toxoplasmosis disease states using human sera. 相似文献
959.
Andreas Reif Sebastian Siebenhaar Andrea Tröster Marina Schmälzlein Carolin Lechner Phanindra Velisetty Karen Gottwald Claudia Pöhner Irene Boos Volker Schubert Prof. Stefan Rose‐John Prof. Carlo Unverzagt 《Angewandte Chemie (International ed. in English)》2014,53(45):12125-12131
Human interleukin 6 (IL‐6) is a potent cytokine with immunomodulatory properties. As the influence of N‐glycosylation on the in vivo activities of IL‐6 could not be elucidated so far, a semisynthesis of homogeneous glycoforms of IL‐6 was established by sequential native chemical ligation. The four cysteines of IL‐6 are convenient for ligations and require only the short synthetic glycopeptide 43–48. The Cys‐peptide 49–183 could be obtained recombinantly by cleavage of a SUMO tag. The fragment 1–42 was accessible by the simultaneous cleavage of two inteins, leading to the 1–42 thioester with the native N‐terminus. Ligation and refolding studies showed that the inherently labile Asp? Pro bond 139–140 was detrimental for the sequential C‐ to N‐terminal ligation. A reversed ligation sequence using glycopeptide hydrazides gave full‐length IL‐6 glycoproteins, which showed full bioactivity after efficient refolding and purification. 相似文献
960.
Helge Klare Sebastian Hanft Dr. Jörg M. Neudörfl Dr. Nils E. Schlörer Prof. Dr. Axel Griesbeck Prof. Dr. Bernd Goldfuss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11847-11855
Modular cyclodiphosph(V)azanes are synthesised and their affinity for chloride and actetate anions were compared to those of a bisaryl urea derivative ( 1 ). The diamidocyclodiphosph(V)azanes cis‐[{ArNHP(O)(μ‐tBu)}2] [Ar=Ph ( 2 ) and Ar=m‐(CF3)2Ph ( 3 )] were synthesised by reaction of [{ClP(μ‐NtBu)}2] ( 4 ) with the respective anilines and subsequent oxidation with H2O2. Phosphazanes 2 and 3 were obtained as the cis isomers and were characterised by multinuclear NMR spectroscopy, FTIR spectroscopy, HRMS and single‐crystal X‐ray diffraction. The cyclodiphosphazanes 2 and 3 readily co‐crystallise with donor solvents such as MeOH, EtOH and DMSO through bidentate hydrogen bonding, as shown in the X‐ray analyses. Cyclodiphosphazane 3 showed a remarkably high affinity (log[K]=5.42) for chloride compared with the bisaryl urea derivative 1 (log[K]=4.25). The affinities for acetate (AcO?) are in the same range ( 3 : log[K]=6.72, 1 : log[K]=6.91). Cyclodiphosphazane 2 , which does not contain CF3 groups, exhibits weaker binding to chloride (log[K]=3.95) and acetate (log[K]=4.49). DFT computations and X‐ray analyses indicate that a squaramide‐like hydrogen‐bond directionality and Cα?H interactions account for the efficiency of 3 as an anion receptor. The Cα?H groups stabilise the Z,Z‐ 3 conformation, which is necessary for bidentate hydrogen bonding, as well as coordinating with the anion. 相似文献