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排序方式: 共有311条查询结果,搜索用时 15 毫秒
31.
Eoin Moriarty 《Tetrahedron letters》2009,50(37):5251-2730
The preparation of alicyclic ring-fused tetracyclic and pentacyclic benzimidazoles containing one and two fused aryl rings, respectively, is achieved conveniently in three steps, including Bu3SnH-mediated 6-exo-trig cyclization of σ-aryl radicals generated from 1-allyl-2-(ω-bromoaryl)benzimidazoles. Inclusion of 4,7-dimethoxy substituents on the radical precursors allows access to aryl ring-fused benzimidazolequinones, a unique family of potential bioreductive anti-cancer agents. 相似文献
32.
In the presence of a Ni/phosphine ligand catalyst, dimethylzinc, alkyne, butadiene, aldehyde, and primary amine were successively combined via dimerization of butadiene to provide (3E,7E,10Z)-dodecatrienylamine in good yields with excellent regio and stereoselectivities. 相似文献
33.
Xue-Min Tan Qiao-Mei Lai Zhi-Wei Yang Xiao Long Hai-Lin Zhou Xiao-Lin You Xiao-Jie Jiang Hai-Lei Cui 《Tetrahedron letters》2017,58(2):163-167
A La(OTf)3 catalyzed synthesis of tetrasubstituted pyrroles under microwave irradiation has been developed affording various α-aryl tetrasubstituted pyrroles in acceptable to good yields (36–82% yield) through condensation/alkyne azacyclization/isomerization sequence. Functionalized α-aryl pentasubstituted pyrroles could be prepared from tetrasubstituted pyrroles through easy transformations. 相似文献
34.
A modular approach to 5-acylated naphtho[2,1-b]benzofurans was developed where Sonogashira cross-coupling and intramolecular alkyne carbonyl metathesis were sequentially employed to build the aromatic benzene C ring of naphtho[2,1-b]benzofuran with an acyl group at the C5 position. 相似文献
35.
Innus Mohammad JiYoung Mun Amber Onorato Martha D. Morton Abdullah I. Saleh Michael B. Smith 《Tetrahedron letters》2017,58(44):4162-4165
When compared to a long-straight chain terminal alkyne, a long chain terminal alkyne with a distal isopropyl unit (isobranched) isomerizes about two times faster when treated with strong base under identical conditions, and appears to follow pseudo first order kinetics. In both cases, equilibration to a 95–97:5–3 mixture of terminal:internal alkyne accompanies isomerization. The difference in rate may be due to an unusual folding of both long-chain alkynes, bringing the distal substituent close to the carbon-carbon-triple bond moiety. The distal isopropyl moiety may provide unanticipated steric hindrance that disrupts such folding, making the propargylic proton more available for reaction with base. 相似文献
36.
A new method for constructing the polycyclic skeleton of psiguadial B (1), a meroterpenoid isolated from an evergreen shrub of Myrtaceae, was developed. The terpenoid substructure of 1 was constructed on the basis of a cascade double cyclization reaction of an alkyne dicobalt complex, which afforded the bicyclo[4.3.1]decane derivative having a benzyl group with the correct configuration. The substituted aromatic ring was introduced to the bridgehead position of the intermediate, and bromination under radical conditions followed by intramolecular cyclization reaction resulted in formation of the benzopyran moiety in a stereoselective manner. 相似文献
37.
Yun-Hua Wang 《Tetrahedron》2010,66(35):7136-6130
A simply performed procedure for the [Rh(cod)Cl]2/cationic 2,2′-bipyridyl system-catalyzed [2+2+2] cycloaddition of α,ω-diynes with terminal and internal alkynes was achieved in water under air at 60 °C. The reaction proceeded smoothly with 1 equiv α,ω-diynes and 3 equiv alkynes in the presence of 20 mol % KOH for 1 h or 9 h, resulting in the formation of tri- and tetra-substituted benzene derivatives in moderate to high yields. After separation of the organic products by extraction, the residual aqueous solution could be reused for further reactions until complete degradation of its catalytic activity. 相似文献
38.
Christopher S. Chambers 《Tetrahedron letters》2010,51(37):4859-5151
Intramolecular 1,3-dipolar cycloaddition between an alkyne and an azide leads to a series of 1,2,3-triazolo-fused 1,4-benzodiazepines, 1,2,5-benzothiadiazepines, pyrrolobenzodiazepines and pyrrolobenzothiadiazepines (eight examples). The products are privileged structures in medicinal chemistry. The precursor azido alkynes are obtained, usually as transient intermediates, by treatment of the corresponding aldehydes (derived from α-amino acids) with the Bestmann-Ohira reagent. 相似文献
39.
Björn Hellbach 《Journal of organometallic chemistry》2006,691(9):1814-1816
The reaction of 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene with silver(I)triflate yielded a 1:2 complex. X-ray investigations revealed that each silver ion is tetrahedrally coordinated to one triple bond and three oxygen atoms of the triflate anion. 相似文献
40.
Crystal Structure of Cesium Phenylacetylide,CsC2C6H5, Solved and Refined from Synchrotron Powder Diffraction Data
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The crystal structure of cesium phenylacetylide, CsC2C6H5, was solved and refined from synchrotron powder diffraction data (Pbca, Z = 8). Each Cs+ cation is coordinated by five ligands: four acetylide groups coordinate side‐on and one end‐on. A similar arrangement is found in the crystal structure of NaC2H (P4/nmm, Z = 2). There is a group‐subgroup relationship between both structures. Most importantly, the crystal structure of CsC2C6H5 could only be solved with the help of synchrotron data, as the very good peak:noise ratio allowed the assignment of several very weak reflections, which finally led to the correct space group, in which a structural solution was possible using direct space methods. 相似文献