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81.
82.
Functionalization of Quinoxalines by Using TMP Bases: Preparation of Tetracyclic Heterocycles with High Photoluminescene Quantum Yields 下载免费PDF全文
Julia Nafe Dr. Simon Herbert Dr. Florian Auras Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Thomas Bein Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1102-1107
Tetracyclic heterocycles that exhibit high photoluminescence quantum yields were synthesized by anellation reactions of mono‐, di‐, and trifunctionalized 2,3‐dichloroquinoxalines. Thus, treatment of 2,3‐dichloroquinoxaline with TMPLi (TMP=2,2,6,6‐tetramethylpiperidyl) allows a regioselective lithiation in position 5. Quenching with various electrophiles (iodine, (BrCl2C)2, allylic bromide, acid chloride, aryl iodide) leads to 5‐functionalized 2,3‐dichloroquinoxalines. Further functionalization in positions 6 and 8 can be achieved by using TMPLi or TMPMgCl ? LiCl furnishing a range of new di‐ and tri‐functionalized 2,3‐dichloroquinoxalines. The chlorine atoms are readily substituted by anellation with 1,2‐diphenols or 1,2‐dithiophenols leading to a series of new tetracyclic compounds. These materials exhibit strong, tunable optical absorption and emission in the blue and green spectral region. The substituted O‐heterocyclic compounds exhibit particularly high photoluminescence quantum yields of up to 90 %, which renders them interesting candidates for fluorescence imaging applications. 相似文献
83.
Versatile Tailoring of Paddle‐Wheel ZnII Metal–Organic Frameworks through Single‐Crystal‐to‐Single‐Crystal Transformations 下载免费PDF全文
Tapan K. Pal Dr. Subhadip Neogi Prof. Parimal K. Bharadwaj 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16083-16090
A new tetracarboxylate ligand having short and long arms formed 2D layer ZnII coordination polymer 1 with paddle‐wheel secondary building units under solvothermal conditions. The framework undergoes solvent‐specific single crystal‐to‐single crystal (SC‐SC) transmetalation to produce 1Cu . With a sterically encumbered dipyridyl linker, the same ligand forms non‐interpenetrated, 3D, pillared‐layer ZnII metal–organic framework (MOF) 2 , which takes part in SC‐SC linker‐exchange reactions to produce three daughter frameworks. The parent MOF 2 shows preferential incorporation of the longest linker in competitive linker‐exchange experiments. All the 3D MOFs undergo complete SC‐SC transmetalation with CuII, whereby metal exchange in different solvents and monitoring of X‐ray structures revealed that bulky solvated metal ions lead to ordering of the shortest linker in the framework, which confirms that the solvated metal ions enter through the pores along the linker axis. 相似文献
84.
Laura Ielo Laura Castoldi Saad Touqeer Jessica Lombino Alexander Roller Cristina Prandi Wolfgang Holzer Vittorio Pace 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21038-21043
The selective formal insertion (homologation) of a carbon unit bridging the two trifluoroacetamidoyl chlorides (TFAICs) units is reported. The tactic is levered on a highly chemoselective homologation–metalation–acyl nucleophilic substitution sequence which precisely enables to assemble novel trifluoromethylated β-diketiminates within a single synthetic operation. Unlike previous homologations conducted with LiCH2Cl furnishing aziridines, herein we exploit the unique capability of iodomethyllithium to act contemporaneously as a C1 source (homologating effect) and metalating agent. The mechanistic rationale grounded on experimental evidences supports the hypothesized proposal and, the structural analysis gathers key aspects of this class of valuable ligands in catalysis. 相似文献
85.
Haag B Mosrin M Ila H Malakhov V Knochel P 《Angewandte Chemie (International ed. in English)》2011,50(42):9794-9824
The preparation of highly functionalized organometallic compounds can be achieved by direct C H activation of a broad range of unsaturated substrates using lithium chloride solubilized 2,2,6,6‐tetramethylpiperidide bases (TMPnMXm⋅p LiCl). These are excellent reagents for converting a wide range of aromatic and heterocyclic substrates into valuable organometallic reagents with broad applications in organic synthesis. 相似文献
86.
87.
Melzig L Rauhut CB Naredi-Rainer N Knochel P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(19):5362-5372
The aryl sulfoxide moiety allows an expedient two‐step difunctionalisation of readily available diaryl sulfoxides. Highly functionalised 1,2,4‐trisubstituted arenes and difunctionalised heteroarenes (furans, thiophenes, benzofurans and pyridines) were prepared in a two‐step sequence, triggered by an aryl sulfoxide group. In the first step, the sulfoxide moiety acts as a metallation‐directing group, allowing smooth ortho‐magnesiation with TMPMgCl ? LiCl (TMP=tetramethylpiperidine). After a quenching reaction with an electrophile, the resulting sulfoxide is converted into a second magnesium reagent with iPrMgCl ? LiCl (sulfoxide–magnesium exchange), which can be trapped with various electrophiles. Highly chemoselective TMPMgCl ? LiCl and iPrMgCl ? LiCl are compatible with a broad range of functional groups (e.g., F, Cl, CF3, CN, CO2tBu, alkynyl, ethers, thioethers). Large‐scale reactions (25–40 mmol) and the preparation of fully functionalised furans and thiophenes are also reported. 相似文献
88.
Victoria L. Blair Luca M. Carrella William Clegg Prof. Jan Klett Dr. Robert E. Mulvey Prof. Dr. Eva Rentschler Prof. Dr. Luca Russo Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):856-863
With the aim of introducing the diisopropylamide [NiPr2] ? ligand to alkali‐metal‐mediated manganation (AMMMn) chemistry, the temperature‐dependent reactions of a 1:1:3 mixture of butylsodium, bis(trimethylsilylmethyl)manganese(II), and diisopropylamine with ferrocene in hexane/toluene have been investigated. Performed at reflux temperature, the reaction affords the surprising, ferrocene‐free, hydrido product [Na2Mn2 (μ‐H)2{N(iPr)2}4]?2 toluene ( 1 ), the first Mn hydrido inverse crown complex. Repeating the reaction rationally, excluding ferrocene, produces 1 in an isolated crystalline yield of 62 %. At lower temperatures, the same bimetallic amide mixture leads to the manganation of ferrocene to generate the first trimanganese, trinuclear ferrocenophane, [{Fe(C5H4)2}3{Mn3Na2(NiPr2)2 (HNiPr2)2}] ( 2 ) in an isolated crystalline yield of 81 %. Both 1 and 2 have been characterised by X‐ray crystallographic studies. The magnetic properties of paramagnetic 1 and 2 have also been examined by variable‐temperature magnetisation measurements on powdered samples. For 1 , the room‐temperature value for χT is 3.45 cm3 K mol?1, and on lowering the temperature a strong antiferromagnetic coupling between the two Mn ions is observed. For 2 , the room‐temperature value for χT is 4.06 cm3 K mol?1, which is significantly lower than the expected value for three isolated paramagnetic MnII ions. 相似文献
89.
William Clegg Prof. Ben Conway David V. Graham Eva Hevia Dr. Alan R. Kennedy Dr. Robert E. Mulvey Prof. Luca Russo Dr. Dominic S. Wright Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7074-7082
Two potassium–dialkyl–TMP–zincate bases [(pmdeta)K(μ‐Et)(μ‐tmp)Zn(Et)] ( 1 ) (PMDETA=N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine, TMP=2,2,6,6‐tetramethylpiperidide), and [(pmdeta)K(μ‐nBu)(μ‐tmp)Zn(nBu)] ( 2 ), have been synthesized by a simple co‐complexation procedure. Treatment of 1 with a series of substituted 4‐R‐pyridines (R=Me2N, H, Et, iPr, tBu, and Ph) gave 2‐zincated products of the general formula [{2‐Zn(Et)2‐μ‐4‐R‐C5H3N}2 ? 2{K(pmdeta)}] ( 3 – 8 , respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51 %, respectively; the treatment of 2 with 4‐tBu‐pyridine gave [{2‐Zn(nBu)2‐μ‐4‐tBu‐C5H3N}2 ? 2{K(pmdeta)}] ( 9 ) in an isolated crystalline yield of 58 %. Single‐crystal X‐ray crystallographic and NMR spectroscopic characterization of 3 – 9 revealed a novel structural motif consisting of a dianionic dihydroanthracene‐like tricyclic ring system with a central diazadicarbadizinca (ZnCN)2 ring, face‐capped on either side by PMDETA‐wrapped K+ cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3 , 7 , 8 , and 9 appear to be essentially clean reactions, in contrast to those producing 4 , 5 , and 6 , which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium–zincate base acts as an amido transfer agent with a subsequent ligand‐exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4‐coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl–zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn? N bonds for efficient zincation. 相似文献
90.
Inma Angurell Dr. Oriol Rossell Prof. Miquel Seco Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(12):2932-2940
Onion structures : Carbosilane dendrimers containing up to four metal layers have been constructed (see picture). The metal layers are linked by di‐ or tritopic N,P ligands. Selective deconstruction of the dendrimers is achieved by using salts of chloride or iodide anions.