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141.
Cinchona alkaloids exhibit remarkable catalytic activities in a wide range of organic transformations. This review summarizes the recent advances of computational studies in understanding the mechanism and origins of enantioselectivities in cinchona alkaloid-catalyzed asymmetric Michael additions. Key activation model and controlling factors of reactivity and selectivity are elucidated. 相似文献
142.
《Journal of mass spectrometry : JMS》2017,52(6):378-396
This study reports an applicable analytical strategy of comprehensive identification and structure characterization of target components from Gelsemium elegans by using high‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry (LC‐QqTOF MS) based on the use of accurate mass databases combined with MS/MS spectra. The databases created included accurate masses and elemental compositions of 204 components from Gelsemium and their structural data. The accurate MS and MS/MS spectra were acquired through data‐dependent auto MS/MS mode followed by an extraction of the potential compounds from the LC‐QqTOF MS raw data of the sample. The same was matched using the databases to search for targeted components in the sample. The structures for detected components were tentatively characterized by manually interpreting the accurate MS/MS spectra for the first time. A total of 57 components have been successfully detected and structurally characterized from the crude extracts of G. elegans , but has failed to differentiate some isomers. This analytical strategy is generic and efficient, avoids isolation and purification procedures, enables a comprehensive structure characterization of target components of Gelsemium and would be widely applicable for complicated mixtures that are derived from Gelsemium preparations. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
143.
Ping Tang Dong Lin Chen Qiao Hong Chen Xi Xian Jian Feng Peng Wang Department of Chemistry of Medicinal Natural Products West China College of Pharmacy Sichuan University Chengdu China 《中国化学快报》2007,18(6):700-703
Three new lycoctonine-type C19-diterpenoid alkaloids, laxicymine 1, laxicymisine 2, and laxicyminine 3 have been isolated from the whole herb of Delphinium laxicymosum var. pilostachyum W.T. Wang. Their structures were established by spectra data. 相似文献
144.
Weifang Wang Taiko Oda Remy E.P. Mangindaan Kazuyo Ukai Michio Namikoshi 《Tetrahedron》2007,63(2):409-412
Three new sulfur-containing alkaloids, polycarpaurines A (1), B (2), and C (3) were isolated from the tropical ascidian Polycarpa aurata collected in Indonesia, together with six known compounds (4-9). The structures of new compounds were assigned on the basis of their spectral data. Compounds 1, 3, 4, and 8 inhibited colony formation of Chinese hamster V79 cells with EC50 values of 6.8, 8.6, 3.8, and 10 μM, respectively. Compounds 2 and 7 showed modest activity against V79 cells (EC50>10 μM). 相似文献
145.
Prof. Laxmidhar Rout Dr. Bibhuti Bhusan Parida Dr. Jean‐Claude Florent Dr. Ludger Johannes Santosh Kumar Choudhury Dr. Ganngam Phaomei Prof. Joe Scanlon Dr. Emmanuel Bertounesque 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):14812-14815
C(sp)?H Bond activation of acetylene molecule still remains a challenge for synthetic organic chemists. In practice, acetylenes are activated by strong bases and metals. The first example for activating acetylenic protons under base and metal‐free conditions is reported here. It involves a general method for synthesizing propargylic derivatives of cotarnine. An array of tetrahydroisoquinolines alkaloids was synthesized by C(sp)?H bond activation of aromatic acetylenes with cotarnine at room temperature. A DFT‐based mechanism is proposed for the reaction. 相似文献
146.
A facile synthetic path to isoindolobenzazepine alkaloids, lennoxamine, 13-deoxychilenine, and chilenine, was established by employing a palladium-catalyzed intramolecular α-arylation of the ketone, as the key step. 相似文献
147.
148.
Qiao Hong CHEN Feng Peng WANG* Department of Chemistry of Medicinal Natural Products School of Pharmacy West China University of Medical Sciences Chengdu 《中国化学快报》2001,(5)
Lappaconitine 1, a bisnorditerpenoid alkaloid, was isolated from many plants of Aconitum species such as A. barbatum var. pulerulum and A. sinomontanum (Ranunculaceae)1-3, and used clinically for treatment of analgic disease as a nonaddicted drug in China4, and as an antiarrythmic in Uzbekistan5. In order to search for high activity, low toxicity compounds, we have carried out the structure modifications of lappaconitine. In this case, an attempt to induce the oxygenated group at C-10 in 1 b… 相似文献
149.
Racemic C2-symmetric 1,2-diols were kinetically resolved by the acylation reaction catalyzed by the phosphinite derivative of quinidine to afford the corresponding monoacylated product with good to high enantioselectivities. 相似文献
150.
D. U. Abdullaeva K. K. Turgunov B. Tashkhodzhaev K. Samikov R. Shakirov 《Chemistry of Natural Compounds》2004,40(4):394-397
The new steroidal alkaloid sevedinine was isolated from the aerial part of Korolkovia severtzovii. The structure of sevedinine wasestablished as 6,12-dihydroxy-5-cevanin-3-one using spectral data, chemical transformations, and an x-ray structure analysis. The location of the tertiary hydroxyl in ten cevine alkaloids from Korolkovia severtzovii was corrected based on the results. 相似文献