全文获取类型
收费全文 | 137篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 106篇 |
力学 | 2篇 |
数学 | 14篇 |
物理学 | 26篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 31 毫秒
1.
Yuyang Ji Rebekka S. Klausen 《Journal of polymer science. Part A, Polymer chemistry》2021,59(21):2521-2529
The synthesis of vinyl alcohol copolymers is limited due to the poor radical reactivity of vinyl acetate (VAc), the traditional precursor to polyvinyl alcohol (PVA). Main group monomers such as BN 2-vinylnaphthalene (BN2VN) have attracted attention as alternatives to VAc to form side chain hydroxyls via oxidation, but outstanding questions of molecular weight control remain. Herein we report systematic investigation of solvent, temperature, and initiator concentration as factors influencing BN2VN degree of polymerization. We find increased chain transfer to toluene, hypothesized to arise from differences in radical stabilization and reactivity by aromatic and BN aromatic rings. As a result of these combined efforts, high molecular weight (Mw ~ 105 g mol−1) BN2VN homopolymers and BN2VN-styrene copolymers were obtained. 相似文献
2.
Zusammenfassung Zur Messung der Zugfestigkeit bei kürzesten Beanspruchungszeiten wird eine Prüfapparatur beschrieben, bei der die Beanspruchung
des Prüfstabes durch eine Sprengstoffdetonation erfolgt. Durch ein besonders eingebautes Me?element, das aus einem dünnwandigen
Stahlrohr mit geeignet angebrachten Dehnungsme?streifen besteht, ist es m?glich, den zeitlichen Verlauf der vor dem Zerrei?en
auf den Prüfstab wirkenden Kraft exakt zu messen. Es wird gezeigt, da? durch die besondere Anordnung der Dehnungsme?streifen
ein tr?gheitsfreies Messen bis zu einer Zeit von 5 · 10−5 sec, bei einer Genauigkeit der Kraftmessung von ± 10%, erreicht werden kann.
Messungen mit dieser Apparatur an verschiedenen Kunststoffen zeigen, da? das für den kurzzeitigsten Beanspruchungsbereich
gewonnene Kurvenstück, das die Abh?ngigkeit der Zugfestigkeit von der Beanspruchungszeit gibt, zwanglos mit der Zugfestigkeit
beim normalen Zugversuch mit wesentlich l?ngerer Beanspruchungszeit in Verbindung gesetzt werden kann.
Auch Stoffe, die beim üblichen Zugversuch fast gleiche Zugfestigkeiten aufweisen, zeigen im kurzzeitigsten Bereich ein sehr
unterschiedliches Verhalten. Ein glas?hnlicher Bruch beim Polyester und Polystyrol l?uft parallel mit einer konstanten Zugfestigkeit
auch bei kürzesten Beanspruchungszeiten, w?hrend die spr?den Brüche von bei normalen Beanspruchungszeiten plastisch verformbaren
Substanzen parallel laufen mit einem zum Teil sehr starken Anstieg der Zugfestigkeit, wie das beim Polyamid und Polyvinylchlorid
der Fall ist.
Vorgetragen auf der Arbeitssitzung des Fachausschusses „Physik der Hochpolymeren“ im Verband der Deutschen Physikalischen
Gesellschaften zur Physikertagung München am 7. September 1956.
Abschliegend sei noch den Herren Dr. H. Elsner und Dr. E. Nümann, Dynamit-Actien-Gesellsehafg, Troisdorf, für die freundliehe
Ungerstützung dureh Hinweise gedankt. Ebenso sei noehmals dankend erw?hnt, da? die Farbenfabriken Bayer, Abt. Kautsehuk und
Kunstsgoffe, freundlieherweise Kunststoffproben zur Verfügung gestellg haben. 相似文献
3.
4.
5.
6.
Rebekka Scholz Peter Palatzky Frank-Michael Matysik 《Analytical and bioanalytical chemistry》2014,406(3):687-694
Oxidative stress plays a crucial role in DNA and RNA damage within biological cells. As a consequence, mutations of DNA can occur, leading to disorders like cancer and neurodegenerative and cardiovascular diseases. The oxidative attack of guanosine and 8-oxo-7,8-dihydroguanosine is simulated by electrochemistry coupled to capillary electrophoresis–mass spectrometry. The electrochemical conversion of the compound of interest is implemented in the injection protocol termed electrochemically assisted injection (EAI). In this way, oxidation products of guanosine can be generated electrochemically, separated by capillary electrophoresis, and detected by electrospray ionization time-of-flight mass spectrometry (EAI–CE–MS). A fully automated laboratory-made EAI cell with an integrated buffer reservoir and a compartment holding screen-printed electrodes is used for the injection. In this study, parameters like pH of the sample solution and the redox potential applied during the injection were investigated in terms of corresponding formation of well-known markers of DNA damage. The important product species, 8-oxo-7,8-dihydroguanosine, was investigated in a separate study to distinguish between primary and secondary oxidation products. A comparison of product species formed under alkaline, neutral, and acidic conditions is presented. To compare real biological systems with an analytical approach for simulation of oxidative stress, it is desirable to have a well-defined control over the redox potential and to use solutions, which are close to physiological conditions. In contrast to typical HPLC–MS protocols, the hyphenation of EAI, CE, and MS enables the generation and separation of species involved without the use of organic solvents. Thus, information of the electrochemical behavior of the nucleoside guanosine as well as the primary oxidation product 8-oxo-7,8-dihydroguanosine can be characterized under conditions close to the physiological situation. In addition, the migration behavior found in CE separations of product species can be used to identify compounds if several possible species have the same mass-to-charge values determined by MS detection. 相似文献
7.
Dr. Lewis C. H. Maddock Rebekka Morton Dr. Alan R. Kennedy Prof. Dr. Eva Hevia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(61):15181-15187
Alkali-metal ferrates containing amide groups have emerged as regioselective bases capable of promoting Fe−H exchanges of aromatic substrates. Advancing this area of heterobimetallic chemistry, a new series of sodium ferrates is introduced incorporating the bulky arylsilyl amido ligand N(SiMe3)(Dipp) (Dipp=2,6-iPr2-C6H3). Influenced by the large steric demands imposed by this amide, transamination of [NaFe(HMDS)3] (HMDS=N(SiMe3)2) with an excess of HN(SiMe3)(Dipp) led to the isolation of heteroleptic [Na(HMDS)2Fe{N(SiMe3)Dipp}]∞ ( 1 ) resulting from the exchange of just one HMDS group. An alternative co-complexation approach, combining the homometallic metal amides [NaN(SiMe3)Dipp] and [Fe{N(SiMe3)Dipp}2] induces lateral metallation of one Me arm from the SiMe3 group in the iron amide furnishing tetrameric [NaFe{N(SiCH2Me2)Dipp}{N(SiMe3)Dipp}]4 ( 2 ). Reactivity studies support that this deprotonation is driven by the steric incompatibility of the single metal amides rather than the basic capability of the sodium reagent. Displaying synergistic reactivity, heteroleptic sodium ferrate 1 can selectively promote ferration of pentafluorobenzene using one of its HMDS arms to give heterotrileptic [Na{N(SiMe3)Dipp}(HMDS)Fe(C6F5)]∞ ( 4 ). Attempts to deprotonate less activated pyridine led to the isolation of NaHMDS and heteroleptic Fe(II) amide [(py)Fe{N(SiMe3)Dipp}(HMDS)] ( 5 ), resulting from an alternative redistribution process which is favoured by the Lewis donor ability of this substrate. 相似文献
8.
Taylor D. Krueger Dr. Longteng Tang Dr. Liangdong Zhu Isabella L. Breen Prof. Dr. Rebekka M. Wachter Prof. Dr. Chong Fang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1661-1669
The molecular mechanisms for the photoconversion of fluorescent proteins remain elusive owing to the challenges of monitoring chromophore structural dynamics during the light-induced processes. We implemented time-resolved electronic and stimulated Raman spectroscopies to reveal two hidden species of an engineered ancestral GFP-like protein LEA, involving semi-trapped protonated and trapped deprotonated chromophores en route to photoconversion in pH 7.9 buffer. A new dual-illumination approach was examined, using 400 and 505 nm light simultaneously to achieve faster conversion and higher color contrast. Substitution of UV irradiation with visible light benefits bioimaging, while the spectral benchmark of a trapped chromophore with characteristic ring twisting and bridge-H bending motions enables rational design of functional proteins. With the improved H-bonding network and structural motions, the photoexcited chromophore could increase the photoswitching-aided photoconversion while reducing trapped species. 相似文献
9.
David A. Burns Eric M. Press M. A. Siegler Rebekka S. Klausen V. Sara Thoi 《Angewandte Chemie (International ed. in English)》2020,59(2):763-768
We report the synthesis of a set of 2D metal–organic frameworks (MOFs) constructed with organosilicon‐based linkers. These oligosilyl MOFs feature linear SinMe2n(C6H4CO2H)2 ligands (lin‐Sin, n=2, 4) connected by Cu paddlewheels. The stacking arrangement of the 2D sheets is dictated by van der Waals interactions and is tunable by solvent exchange, leading to reversible structural transformations between many crystalline and amorphous phases. 相似文献
10.
F.J. Himpsel K. Christmann P. Heimann D.E. Eastman Peter J. Feibelman 《Surface science》1982,115(3):L159-L164
We have studied carbon-induced two-dimensional energy bands on Ru(0001) using angleresolved photoelectron spectroscopy and have compared them with ab initio calculations. We find a nearly parabolic band (bottom at EF ?9.8 eV at k∥ = 0, effective mass ~ 1.5 me) which we assign to the C 2pz valence states of a graphitic carbon overlayer. Compared to graphite, these states are bound more tightly by 2.3 eV. 相似文献