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排序方式: 共有117条查询结果,搜索用时 15 毫秒
91.
Attila Sisak 《合成通讯》2013,43(24):3693-3702
2‐Aza‐1,3‐butadienes have been synthesized from carbonyl compounds and 1,1,1,3,3,3‐hexamethyl‐disilazane in the presence of cobalt‐containing catalysts. The best yields (up to 95%) were achieved in the case of aldehydes branched in the α-position and 2-methylcyclohexanone. In the case of two α,β‐unsaturated ketones, pyridine derivatives were found as the main products. 相似文献
92.
α-Chloro-α-acetoxy-β-keto-esters 9 were readily prepared from β-keto-esters 6 in good overall yields. These compounds reacted as α,β-diketo-ester equivalents 2 with amidrazones 1 yielding triazines 3, generally in good yields. Picolinates 10 provided an alternative source of α,β-diketo-ester equivalents 2 when treated with copper(II) acetate. A ‘one-pot’ reaction of the α,β-diketo-ester equivalents 2 with amidrazones 1 in the presence of 2,5-norbornadiene 5 in boiling ethanol yielded the pyridines 4 and 2,2′-bipyridines 4 (R1=2-pyridyl) directly without the need to isolate the corresponding triazines 3. Triazine 3c reacted with the aza-dienophiles 13 and 17 affording the products 16 and 18, respectively, in good yields. 相似文献
93.
Davood Nematollahi Leila Mohammadi‐Behzad Saied Saeed Hossainy Davarani 《Electroanalysis》2009,21(9):1099-1106
The electrochemical oxidation of catechols ( 1 ) have been studied in the presence of diaza‐18‐crown‐6 (DA18C6) ( 3a ), diaza‐15‐crown‐5 (DA15C5) ( 3b ), and aza‐15‐crown‐5 (A15C5) ( 3c ) as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate the participation of electrochemically generated o‐benzoquinones ( 2 ) in Michael‐type reaction with aza‐crown ethers ( 3 ) to form the corresponding new o‐benzoquinone‐aza‐crown ether adducts ( 5 ). Based on ECE mechanism, the observed homogeneous rate constants (kobs) of the reaction of o‐bezoquinones ( 2 ) with aza‐crown ethers ( 3 ) were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated observed homogeneous rate constants (kobs) was found to vary in the order DA18C6>DA15C5>A15C5. 相似文献
94.
One of the two bridging protons of the aza‐nido‐decaboranes RNB9H10X can be removed by certain bases to give nido‐anions [RNB9H9X]– [R/X = H/H ( 1 a ), Ph/H ( 1 b ), p‐MeC6H4/H ( 1 c ), Bzl/H ( 1 d ), H/N3 ( 1 ′ a )]; the stericly demanding base 1,8‐bis(dimethylamino)naphthalene (“proton sponge”, ps) is ideal. In the case of tBu anion, the deprotonation (→ C4H10) may be accompanied by a hydridation (→ C4H8), yielding the arachno‐anions [RNB9H11X]– ( 2 a , b , d , 2 ′ a ); these are the main products, when stericly non‐demanding bases like H– are applied. The Lewis acid BH3 is added to 1 a and 1 ′ a to give the aza‐arachno‐undecaborates HNB10H12X [X = H ( 3 a ), N3 (in position 2) ( 3 ′ a )]. Thia‐ and selenaaza‐arachno‐undecaborates, [S(RN)B9H10]– ( 4 b , c ) and [Se(RN)B9H10]– ( 4 ′ b , c ), are obtained from 1 b , c by the addition of sulfur or selenium, respectively. The methylation of the anions 4 c and 4 ′ c gives the thia‐ and selenaazaarachno‐undecaboranes (MeS)(RN)B9H10 ( 5 c ) and (MeSe)(RN)B9H10 ( 5 ′ c ), respectively. The action of HBF4 on the arachno‐borates [HNB10H12X]– ( 3 a , 3 ′ a ) leads to a mixture of nido‐HNB9H10X and nido‐HNB10H11X by the elimination of BH3 or H2, respectively; the aza‐nido‐decaborane predominates in the case of 3 ′ a and the aza‐nido‐undecaborane in the case of 3 a . The action of HBF4 on the anion 4 c yields the hypho‐undecaborate [S(RN)B9H10F2]– ( 6 c ). The structures of the products are elucidated on the basis of 1H and 11B NMR spectra, supported by 2D COSY and HMQC techniques. Two types of 11‐vertex‐arachno structures and an 11‐vertex‐hypho structure are found for the products. The crystal structures of 5 c and [Hps] 6 c · CH2Cl2 are reported. 相似文献
95.
Kurt Utvary Klaus Galle Alan Cowley Atta Arif 《Monatshefte für Chemie / Chemical Monthly》1986,117(11):1245-1256
The reactions of (CH3NPF3)2 and F3P(CH3N)2PF2OCH3 with lithium-1,1,1-trimethyl-N-(trimethylsilyl)-silanamide yield two new dispiro-compounds:XF2P(CH3N)2PF(NSiCH3)2PF(CH3N)2PF2
X withX=F, OCH3. Synthesis, mass-spectra and X-ray structures are discussed.
Herrn Prof. Dr.K. L. Komarek zum 60. Geburtstag gewidmet. 相似文献
96.
97.
98.
《Electroanalysis》2002,14(24):1691-1698
Three different recently synthesized aza‐thioether crowns containing a 1,10‐phenanthroline sub‐unit (L1–L3) and a corresponding acyclic ligand (L4) were studied to characterize their abilities as silver ion ionophores in PVC‐membrane electrodes. Novel conventional silver‐selective electrodes with internal reference solution (CONISE) and coated graphite‐solid contact electrodes (SCISE) were prepared based on one of the 15‐membered crowns containing two donating S atoms and two phenanthroline‐N atoms (L1). The electrodes reveal a Nernstian behavior over wide Ag+ ion concentration ranges (1.0×10?5?1.0×10?1 M for CONISE and 5.0×10?8?4.0×10?2 M for SCISE) and very low limits of detection (8.0×10?6 M for CONISE and 3.0×10?8 M for SCISE). The potentiometric response is independent from pH of the solution in the pH range 3.0–8.0. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations. The electrodes can be used for at least 2 months (for CONISE) and 4 months for (SCISE) without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of Ag+ ion and in the determination of silver in photographic emulsions and in radiographic and photographic films. 相似文献
99.
Dimpy SikriwalDinesh K. Dikshit 《Tetrahedron》2011,67(1):210-215
Aza variant of intramolecular catalytic, asymmetric nucleophile-catalyzed, aldol lactonization (NCAL) reaction has been explored to synthesize β-lactone fused nitrogen heterocycles as aza sugars’ precursors by employing achiral amino acids. The utility of these bicyclic β-lactones is presented by the formal synthesis of aza sugars, (3S,4R) and (3R,4S) 4-(hydroxymethyl)pyrrolidin-3-ol. 相似文献
100.
Summary The reactivity of some monosubstituted fluorodiazadiphosphetidines towards potassium fluoride utilizing 18-crown-6-ether as a phase transfer catalyst has been studied. The following compounds were investigated: 2,2,2,4,4-pentafluoro-4-methoxy-1,3-dimethyl-1,3,25,45-diazadiphosphetidine, 2,2,2,4,4-pentafluoro-4-methylamino-1,3-dimethyl-1,3,25,45-diazadiphosphetidine, 2,2,2,4,4-pentafluoro-4-methylthio-1,3-dimethyl-1,3,25,45-diazadiphosphetidine, and a 1:1 mixture of 2,2,2,4,4-pentafluoro-4-(N2,N2-dimentyl-hydrazino)-1,3-dimethyl-1,3,25,45-diazadiphosphetidine and 2,2,2,4,4-pentafluoro-4-methylamino-1,3-dimethyl-1,3,25,45-diazadiphosphetidine. All reactions proceeded in a similar way and led to the disubstituted derivates of the starting materials and the potassium salt K2(CH3NPF4)2. In this way 2,2,4,4-tetrafluoro-2-methylamino-4-(N2,N2-dimethylhydrazino)-1,3-dimethyl-1,3,25,45-diazadiphosphetidine has been synthesized for the first time and a new way has been found for the synthesis of several compounds reported in literature.
Verstorben 相似文献