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排序方式: 共有315条查询结果,搜索用时 46 毫秒
41.
42.
Palladium‐Catalyzed Regioselective Aromatic Extension of Internal Alkynes through a Norbornene‐Controlled Reaction Sequence
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Dr. Qingyang Zhao Dr. Wai Chung Fu Prof. Dr. Fuk Yee Kwong 《Angewandte Chemie (International ed. in English)》2018,57(13):3381-3385
A regioselective aromatic π‐extension reaction of internal alkynes is reported. The proposed method employs three easily available components, namely aryl halides, 2‐haloarylcarboxylic acids, and disubstituted acetylenes. The transformation is driven by a controlled reaction sequence of C?H activation, decarboxylation, and annulation to give poly(hetero)aromatic compounds in a site‐selective fashion. Unlike in previously reported palladium‐catalyzed three‐component annulations, alkyne carbopalladation is the last step of this tandem reaction. 相似文献
43.
A stereochemically linear strategy has been developed to prepare the heavily congested F-ring sector of lancifodilactone G (1) from commercially inexpensive (R)-carvone. Prominent operations in our synthesis include Negishi-type sp2-sp3 cross-coupling and intramolecular free-radical cyclization for the purpose of appending the sidearm links of the D and H rings onto the F platform. 相似文献
44.
Shing TK Cheng HM Wong WF Kwong CS Li J Lau CB Leung PS Cheng CH 《Organic letters》2008,10(14):3145-3148
A pseudo-1,4'- N-linked disaccharide, pseudoacarviosin 5, was constructed via a key palladium-catalyzed coupling reaction of pseudoglycosyl chloride 8 (prepared from d-glucose via a novel direct intramolecular aldol addition in 12 steps) and pseudo-4-amino-4,6-dideoxy-alpha- d-glucose 9 (prepared from l-arabinose via an unusual trans-fused isoxazolidine-selective intramolecular nitrone-alkene cycloaddition in 11 steps). Pseudoacarviosin 5 has been shown to be a potent inhibitor of alpha-glucosidases, particularly the intestinal mucosal enzymes sucrase and glucoamylase of relevance to blood glucose control. 相似文献
45.
The polyfused medium-sized CDE ring system of lancifodilactone G is assembled via B-alkyl Suzuki-Miyaura cross-coupling and SmI 2-mediated pinacol macrocyclization as the key strategic steps. 相似文献
46.
Man Kam Kwong 《Journal of Differential Equations》2008,245(8):2333-2351
We study the linear differential equation , on I=(0,1), where the coefficient f(x) is strictly positive and continuous on I, and satisfies the Hartman-Wintner condition at x=0. The four main results of the paper are: (i) a criterion for rectifiable oscillations of (P), characterized by the integrability of on I; (ii) a stability result for rectifiable and unrectifiable oscillations of (P), in terms of a perturbation on f(x); (iii) the s-dimensional fractal oscillations (for which we assume also f(x)∼cx−α when x→0, α>2, and s=max{1,3/2−2/α}); and (iv) the co-existence of rectifiable and unrectifiable oscillations in the absence of the Hartman-Wintner condition on f(x). Explicit examples related to the above results are given. 相似文献
47.
Chowdhury RR Crane AK Fowler C Kwong P Kozak CM 《Chemical communications (Cambridge, England)》2008,(1):94-96
Catalytic cross-coupling of aryl Grignard reagents with primary and secondary alkyl halides bearing beta-hydrogens is achieved using Fe(III) amine-bis(phenolate) halide complexes. 相似文献
48.
Hasan K Fowler C Kwong P Crane AK Collins JL Kozak CM 《Dalton transactions (Cambridge, England : 2003)》2008,(22):2991-2998
The structures and properties of six new iron(iii) diamine-bis(phenolate) complexes are reported. Reaction of anhydrous FeX(3) salts (where X = Cl or Br) with the diprotonated tripodal tetradentate ligands 2-pyridylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)[L(1)], and N,N-dimethyl-N',N'-bis(2-methylene-4-methyl-6-tert-butylphenol)ethylenediamine, H(2)[L(2)], produces the trigonal bipyramidal iron(iii) complexes, [L(1)]FeCl , [L(1)]FeBr , [L(2)]FeCl and [L(2)]FeBr . Reaction of FeX(3) with the related linear tetradentate ligand N,N'-bis(4,6-tert-butyl-2-methylphenol)-N,N'-bismethyl-1,2-diaminoethane, H(2)[L(3)], generates square pyramidal iron(iii) complexes, [L(3)]FeCl and [L(3)]FeBr . Complexes have been characterized using electronic absorption spectroscopy and magnetometry. Single crystal X-ray molecular structures have been determined for complexes 1, 3, 5 and 6. 相似文献
49.
A rhodium-(S)-xyl-BINAP complex-catalyzed tandem formate decarbonylation and [2 + 2 + 1] carbonylative cyclization is described; this cooperative process utilizes formate as a condensed CO source, and the newly developed cascade protocol can be extended to its enantioselective version, providing up to 94% ee of the cyclopentenone adducts. 相似文献
50.
Kwong CK Huang R Zhang M Shi M Toy PH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(8):2369-2376
A series of soluble, non-cross-linked polystyrene-supported triphenylphosphane and 4-dimethylaminopyridine reagents were prepared. Some of these polymeric reagents contained either alkyl alcohol or phenol groups on the polymer backbone. The use of these materials as organocatalysts in a range of Morita-Baylis-Hillman reactions indicated that hydroxyl groups could participate in the reactions and accelerate product formation. In the cases examined, phenol groups were more effective than alkyl alcohol groups for catalyzing the reactions. This article is one of the first reports of the synthesis and use of non-natural, bifunctional polymeric reagents for use in organic synthesis in which both functional groups can cooperatively participate in the catalysis of reactions. 相似文献