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91.
Prof. Henning Hopf Prof. Peter G. Jones Dr. Alina Nicolescu Prof. Elena Bicu Dr. Lucian M. Birsa Dr. Dalila Belei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5565-5568
A facile synthesis of Pechmann dyes has been accomplished by the reaction of substituted N‐phenacyl‐4‐dimethylaminopyridinium halides with dimethyl maleate in the presence of DBU. Based on a related 4‐DMAP elimination product and an isolated monolactone intermediate a reaction mechanism has been proposed. The scope of this synthetic method is determined by the availability of α‐haloaroyl or heteroaroyl derivatives. DBU=1,8‐diazabicycloundec‐7‐ene, DMAP=4‐dimethylaminopyridine. 相似文献
92.
A short synthesis of Hagen’s gland lactones 1 and 2 from commercially available pentanal and heptanal, respectively, is outlined. The approach relies on sequential ring closing metathesis and intramolecular oxy-Michael addition as the key transformations. 相似文献
93.
A highly efficient protocol for the library synthesis of biologically important 3H,3′H-spiro[benzofuran-2,1′isobenzofuran]-3,3′-diones has been developed by employing silica sulfuric acid (SSA) as solid acid support under solvent-free condition. The dual characteristics of SSA, as an activating agent as well as oxidizing agent, have been well exposed in these syntheses. The intrinsic advantages of the methodology are the use of solvent-free reaction condition without using any toxic reagents or metal catalyst, operational simplicity, recyclability of the solid support, good availability of the starting materials, and excellent yields which make the method attractive, economic, and ‘benign by design’. 相似文献
94.
Zhi‐Qin Liang Zhong‐Hua Gao Wen‐Qiang Jia Prof. Dr. Song Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1868-1872
Bifunctional N‐heterocyclic carbenes with a free hydroxy group are demonstrated as efficient catalysts for the [3+4] annulation of enals with aurones to give the corresponding benzofuran‐fused ε‐lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Control experiments reveal that the [3+4] cycloadducts are kinetically favored and could be transformed to the thermodynamically favored [3+2] cycloadducts with a non‐bifunctional NHC catalyst. 相似文献
95.
《Angewandte Chemie (International ed. in English)》2017,56(15):4201-4205
A carbene‐catalyzed intermolecular C−N bond formation, which initiates a highly selective cascade reaction for the synthesis of pyrrolidine fused β‐lactones, is disclosed. The nitrogen‐containing bicyclic β‐lactone products are obtained with good yields and excellent stereoselectivities. Synthetic transformations of the reaction products into useful functional molecules, such as amino catalysts, can be efficiently realized under mild reaction conditions. Mechanistically, this study provides insights into modulating the reactivities of heteroatoms, such as nitrogen atoms, in challenging carbene‐catalyzed asymmetric carbon–heteroatom bond‐forming reactions. 相似文献
96.
First Atroposelective Total Synthesis of Enantiomerically Pure Ancistrocladidine and Ancistrotectorine 下载免费PDF全文
Prof. Dr. Gerhard Bringmann Dr. Narasimhulu Manchala Dr. Tobias Büttner Dr. Barbara Hertlein‐Amslinger Raina Seupel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9792-9796
The first regio‐ and stereoselective total synthesis of the axially chiral 7,3′‐coupled naphthylisoquinoline alkaloids ancistrocladidine ( 1 ) and ancistrotectorine ( 2 ) has been described. Both possess a 7,3′‐coupled axis, which before now, was difficult to attain synthetically. Moreover, target 2 has a sensitive relative cis‐array of the two methyl groups at C1 and C3 in the tetrahydroisoquinoline part. The key step in the chosen strategy was the construction of the biaryl axis in accordance with the “lactone method”: the two molecular halves, which were activated in an “inverse‐halogenated” form, were prefixed by an ester bridge, followed by intramolecular coupling, and atroposelective cleavage of the lactone auxiliary bridge delivered the desired biaryl scaffold. 相似文献
97.
Cooperative Activation with Chiral Nucleophilic Catalysts and N‐Haloimides: Enantioselective Iodolactonization of 4‐Arylmethyl‐4‐pentenoic Acids 下载免费PDF全文
Dr. Hidefumi Nakatsuji Yasuhiro Sawamura Prof. Dr. Akira Sakakura Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2014,53(27):6974-6977
Chiral triaryl phosphates promote the enantioselective iodolactonization of 4‐substituted 4‐pentenoic acids to give the corresponding iodolactones in high yields with high enantioselectivity. N‐Chlorophthalimide (NCP) is employed as a Lewis acidic activator and oxidant of I2 for the present iodolactonization. In combination with 1.5 equivalents of NCP, only 0.5 equivalents of I2 are sufficient to generate the iodinating reagent. 相似文献
98.
Kohei Yamashita Yuji Kume Seiya Ashibe Cicilia A. D. Puspita Kotaro Tanigawa Naoki Michihata Prof. Dr. Shinnosuke Wakamori Prof. Dr. Kazutada Ikeuchi Prof. Dr. Hidetoshi Yamada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16408-16421
The total synthesis of mallotusinin, which bears a tetrahydroxydibenzofuranoyl (THDBF) bridge between the 2-oxygen and 4-oxygen of glucose on corilagin with a 3,6-O-(R)-hexahydroxydiphenoyl (HHDP) bridge, is described. The key features of the total synthesis are: 1) improvements of our previously reported method to synthesize corilagin; 2) establishment of the THDBF skeleton via an unusual intramolecular SNAr reaction of an HHDP analogue, and 3) the application of a two-step bislactonization strategy for a HHDP bridge construction into the 2,4-O-THDBF bridge. Oxidative phenol coupling of 1,2,4-orthoacetyl-3,6-di-(4-O-benzylgalloyl)-α-d -glucopyranose and the orthoester cleavage of the coupling product without the pyranose-furanose ring transformation are key reactions for the improved synthesis of corilagin, which enabled the adequate supply of a corilagin precursor that was required to develop the mallotusinin synthesis. These established methods are expected to help develop the synthesis of other ellagitannins with a bridge between the two oxygens of corilagin. 相似文献
99.
Hui-Yun Luo Jia-Wei Dong Yu-Yang Xie Xu-Feng Song Deng Zhu Tongmei Ding Prof. Dr. Yuanyuan Liu Prof. Dr. Zhi-Min Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(67):15411-15418
A divergent strategy for the facile preparation of various enantioenriched phenylthio-substituted lactones was developed based on Lewis base/Brønsted acid co-catalyzed thiolation of homoallylic acids. The acid-controlled regiodivergent cyclization (6-endo vs. 5-exo) and acid-mediated stereoselective rearrangement of phenylthio-substituted lactones were explored. Experimental and computational studies were performed to clarify the origins of the regioselectivity and enantioselectivity. The calculation results suggest that C−O and C−S bond formation might occur simultaneously, without formation of a commonly supposed catalyst-coordinated thiiranium ion intermediate and the potential π–π stacking between substrate and SPh as an important factor in the enantio-determining step. Finally, this methodology was applied in the rapid syntheses of the bioactive natural products (+)-ricciocarpin A and (R)-dodecan-4-olide. 相似文献
100.
《Mendeleev Communications》2021,31(6):847-849
New SNS-ligands were obtained by consequent ring-opening of substituted thiiranes by lithiated 2,6-lutidine, mono- functionalized SN-ligands having been isolated as the intermediate compounds. The molecular structure of ligand 2,6-Py(CH2CH2CBn2SH)2 was elucidated by XRD analysis.The reaction of AlMe3 with SNS-ligands afforded monomeric methyl aluminum complexes which have been tested in ring- opening polymerization of ε caprolactone in bulk. 相似文献