全文获取类型
收费全文 | 827篇 |
免费 | 96篇 |
国内免费 | 4篇 |
专业分类
化学 | 723篇 |
晶体学 | 1篇 |
力学 | 16篇 |
数学 | 83篇 |
物理学 | 104篇 |
出版年
2023年 | 31篇 |
2022年 | 32篇 |
2021年 | 49篇 |
2020年 | 71篇 |
2019年 | 80篇 |
2018年 | 29篇 |
2017年 | 19篇 |
2016年 | 73篇 |
2015年 | 52篇 |
2014年 | 35篇 |
2013年 | 66篇 |
2012年 | 47篇 |
2011年 | 60篇 |
2010年 | 25篇 |
2009年 | 16篇 |
2008年 | 34篇 |
2007年 | 20篇 |
2006年 | 28篇 |
2005年 | 25篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1988年 | 2篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1934年 | 2篇 |
1932年 | 2篇 |
1931年 | 2篇 |
1930年 | 2篇 |
1929年 | 1篇 |
1928年 | 2篇 |
1919年 | 1篇 |
1913年 | 1篇 |
1894年 | 1篇 |
排序方式: 共有927条查询结果,搜索用时 187 毫秒
41.
Alexander K. Mengele Dominik Weixler Avinash Chettri Maite Maurer Fabian Lukas Huber Prof. Gerd M. Seibold Prof. Benjamin Dietzek Prof. Bernhard J. Eikmanns Prof. Sven Rau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16840-16845
A series of three Ru(II) polypyridine complexes was investigated for the selective photocatalytic oxidation of NAD(P)H to NAD(P)+ in water. A combination of (time-resolved) spectroscopic studies and photocatalysis experiments revealed that ligand design can be used to control the mechanism of the photooxidation: For prototypical Ru(II) complexes a 1O2 pathway was found. Rudppz ([(tbbpy)2Ru(dppz)]Cl2, tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, dppz=dipyrido[3,2-a:2′,3′-c]phenazine), instead, initiated the cofactor oxidation by electron transfer from NAD(P)H enabled by supramolecular binding between substrate and catalyst. Expulsion of the photoproduct NAD(P)+ from the supramolecular binding site in Rudppz allowed very efficient turnover. Therefore, Rudppz permits repetitive selective assembly and oxidative conversion of reduced naturally occurring nicotinamides by recognizing the redox state of the cofactor under formation of H2O2 as additional product. This photocatalytic process can fuel discontinuous photobiocatalysis. 相似文献
42.
Dr. Dmitry Katayev Kai F. Pfister Timo Wendling Prof. Dr. Lukas J. Gooßen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):9902-9905
Various (hetero)arenecarboxylic acids were converted to the corresponding Daugulis amides and nitrated selectively in the ortho‐position in the presence of [CuNO3(PPh3)2] and AgNO2 at 50 °C. A microwave‐assisted saponification allows regenerating the carboxylate group within minutes, which may then be removed tracelessly by protodecarboxylation, or substituted by aryl‐ or alkoxy‐groups via decarboxylative cross‐coupling. 相似文献
43.
Aryl–Phenyl Scrambling in Intermediate Organopalladium Complexes: A Gas‐Phase Study of the Mizoroki–Heck Reaction 下载免费PDF全文
Lukas Fiebig Dr. Nils Schlörer Prof. Hans‐Günther Schmalz Priv.‐Doz. Dr. Mathias Schäfer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4906-4910
The intramolecular aryl–phenyl scrambling reaction within palladium–DPPP–aryl complex (DPPP=1,3‐bis(diphenylphosphino)propane) ions was analyzed by state‐of‐the‐art tandem MS, including gas‐phase ion/molecule reactions. The Mizoroki–Heck cross‐coupling reaction was performed in the gas phase, and the intrinsic reactivity of important intermediates could be examined. Moreover, linear free‐energy correlations were applied, and a mechanism for the scrambling reaction proceeding via phosphonium cations was assumed. 相似文献
44.
Simon Eyer Nicholas P. Stadie Andreas Borgschulte Lukas Emmenegger Joachim Mohn 《Adsorption》2014,20(5-6):657-666
Methane (CH \(_4\) ) adsorption has been widely studied, mainly in the context of natural gas purification. A much less prominent, but highly relevant application is the preconcentration of CH \(_4\) from ambient air. In this study, we compare six different commercial adsorbent materials with respect to their effectiveness for methane preconcentration: a macroporous polymeric resin (HayeSep D), multi-walled carbon nanotubes, two microporous metal-organic frameworks (HKUST-1 and ZIF-8), and two zeolites (5A and 13X). The most relevant properties, such as isosteric enthalpy of adsorption, specific surface area and the selectivity for CH \(_4\) adsorption over N \(_2\) were characterized by analyzing adsorption/desorption isotherms. Using these parameters, we discuss the tested adsorbents with respect to the most important properties and identify the most promising candidates. Furthermore we identify the experimental conditions that are expected to give the best results with respect to practical applications. 相似文献
45.
TEAD–YAP Interaction Inhibitors and MDM2 Binders from DNA-Encoded Indole-Focused Ugi Peptidomimetics
Verena B. K. Kunig Dr. Marco Potowski Dr. Mohammad Akbarzadeh Dr. Mateja Klika Škopić Denise dos Santos Smith Lukas Arendt Ina Dormuth Dr. Hélène Adihou Blaž Andlovic Dr. Hacer Karatas Shabnam Shaabani Tryfon Zarganes-Tzitzikas Prof. Dr. Constantinos G. Neochoritis Ran Zhang Prof. Dr. Matthew Groves Dr. Stéphanie M. Guéret Dr. Christian Ottmann Prof. Dr. Jörg Rahnenführer Prof. Dr. Roland Fried Prof. Dr. Alexander Dömling Dr. Andreas Brunschweiger 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20518-20522
DNA-encoded combinatorial synthesis provides efficient and dense coverage of chemical space around privileged molecular structures. The indole side chain of tryptophan plays a prominent role in key, or “hot spot”, regions of protein–protein interactions. A DNA-encoded combinatorial peptoid library was designed based on the Ugi four-component reaction by employing tryptophan-mimetic indole side chains to probe the surface of target proteins. Several peptoids were synthesized on a chemically stable hexathymidine adapter oligonucleotide “hexT”, encoded by DNA sequences, and substituted by azide-alkyne cycloaddition to yield a library of 8112 molecules. Selection experiments for the tumor-relevant proteins MDM2 and TEAD4 yielded MDM2 binders and a novel class of TEAD-YAP interaction inhibitors that perturbed the expression of a gene under the control of these Hippo pathway effectors. 相似文献
46.
Single crystals of three new strontium nitridogermanates(IV) were grown in sealed niobium ampules from sodium flux. Dark red Sr4[GeN4] crystallizes in space group P21/c with a = 9.7923(2) Å, b = 6.3990(1) Å, c = 11.6924(3) Å and β = 115.966(1)°. Black Sr8Ge2[GeN4] contains Ge4– anions coexisting with [GeIVN4]8– tetrahedra and adopts space group Cc with a = 10.1117(4) Å, b = 17.1073(7) Å, c = 10.0473(4) Å and β = 115.966(1)°. Black Sr17Ge6N14 features the same anions alongside trigonal planar [GeIVN3]5– units. It crystallizes in P1 with a = 7.5392(1) Å, b = 9.7502(2) Å, c = 11.6761(2) Å, α = 103.308(1)°, β = 94.651(1)° and γ = 110.248(1)°. 相似文献
47.
Philipp Rotering Lukas F. B. Wilm Janina A. Werra Dr. Fabian Dielmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(2):406-411
Electron-rich tertiary phosphines are valuable species in chemical synthesis. However, their broad application as ligands in catalysis and reagents in stoichiometric reactions is often limited by their costly synthesis. Herein, we report the synthesis and properties of a series of phosphines with 1-alkylpyridin-4-ylidenamino and 1-alkylpyridin-2-ylidenamino substituents that are accessible in a very short and scalable route starting from commercially available aminopyridines and chlorophosphines. The determination of the Tolman electronic parameter (TEP) value reveals that the electron donor ability can be tuned by the substituent pattern at the aminopyridine backbone and it can exceed that of common alkylphosphines and N-heterocyclic carbenes. The potential of the new phosphines as strong nucleophiles in phosphine-mediated transformations is demonstrated by the formation of Lewis base adducts with CO2 and CS2. In addition, the coordination chemistry of the new phosphines towards CuI, AuI, and PdII metal centers has been explored, and a convenient procedure to introduce the most basic phosphine into metal complexes starting from air-stable phosphonium salt is described. 相似文献
48.
Lukas Spree Christin Schlesier Dr. Aram Kostanyan Dr. Rasmus Westerström Prof. Dr. Thomas Greber Prof. Dr. Bernd Büchner Dr. Stanislav M. Avdoshenko Dr. Alexey A. Popov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(11):2436-2449
The substitution of scandium in fullerene single-molecule magnets (SMMs) DySc2N@C80 and Dy2ScN@C80 by lutetium has been studied to explore the influence of the diamagnetic metal on the SMM performance of dysprosium nitride clusterfullerenes. The use of lutetium led to an improved SMM performance of DyLu2N@C80, which shows a higher blocking temperature of magnetization (TB=9.5 K), longer relaxation times, and broader hysteresis than DySc2N@C80 (TB=6.9 K). At the same time, Dy2LuN@C80 was found to have a similar blocking temperature of magnetization to Dy2ScN@C80 (TB=8 K), but substantially different interactions between the magnetic moments of the dysprosium ions in the Dy2MN clusters. Surprisingly, although the intramolecular dipolar interactions in Dy2LuN@C80 and Dy2ScN@C80 are of similar strength, the exchange interactions in Dy2LuN@C80 are close to zero. Analysis of the low-frequency molecular and lattice vibrations showed strong mixing of the lattice modes and endohedral cluster librations in k-space. This mixing simplifies the spin–lattice relaxation by conserving the momentum during the spin flip and helping to distribute the moment and energy further into the lattice. 相似文献
49.
Florian Ritter Dr. Lukas John Dr. Tobias Schindler Julian P. Schroers Simon Teeuwen Dr. Michael E. Tauchert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(59):13436-13444
The dative Pd→B interaction in a series of RDPBR’ Pd0 and PdII complexes (RDPBR’=(o-PR2C6H4)2BR’, diphosphinoborane) was analyzed using XRD, 11B NMR spectroscopy and NBO/NLMO calculations. The borane acceptor discriminates between the oxidation state PdII and Pd0, stabilizing the latter. Reaction of lithium amides with [(RDPBR’)PdII(4-NO2C6H4)I] chemoselectively yields the C−N coupling product. DFT modelling indicates no significant impact of PdII→B coordination on the inner-sphere reductive elimination rate. 相似文献
50.
Zechao Yang Lukas Fromm Tim Sander Julian Gebhardt Tobias A. Schaub Andreas Grling Milan Kivala Sabine Maier 《Angewandte Chemie (International ed. in English)》2020,59(24):9549-9555
Demonstrated here is a supramolecular approach to fabricate highly ordered monolayered hydrogen‐ and halogen‐bonded graphyne‐like two‐dimensional (2D) materials from triethynyltriazine derivatives on Au(111) and Ag(111). The 2D networks are stabilized by N???H?C(sp) bonds and N???Br?C(sp) bonds to the triazine core. The structural properties and the binding energies of the supramolecular graphynes have been investigated by scanning tunneling microscopy in combination with density‐functional theory calculations. It is revealed that the N???Br?C(sp) bonds lead to significantly stronger bonded networks compared to the hydrogen‐bonded networks. A systematic analysis of the binding energies of triethynyltriazine and triethynylbenzene derivatives further demonstrates that the X3‐synthon, which is commonly observed for bromobenzene derivatives, is weaker than the X6‐synthon for our bromotriethynyl derivatives. 相似文献