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301.
Zusammenfassung Primäre und sekundäre Enaminderivate aus Acetessigester und -Diketonen reagieren beim Erhitzen mit Diketen zu Derivaten des -Pyridons.
Syntheses of heterocycles, CXX: Synthesis of 2,6-dimethyl-4-pyridones from enamines and diketene
Primary and secondary enamines derived from ethyl acetoacetate or -diketones react with diketene to yield -pyridones.相似文献
302.
303.
Zusammenfassung Die Synthese einiger einfach substituierter Indigoderivate nach einem kürzlich entwickelten Verfahren wird beschrieben.
The synthesis of some substituted indigos according to a recently developed method is described.相似文献
304.
The Wittig reaction of quinisatines ( 1a,b ) with 1-ethoxycarbonylethyliden- ( 2a ) and ethoxycarbonylmeth-ylenetriphenylphosphorane ( 2b ) has been investigated. In both cases unusual reaction products ( 3a,b and 12a,b respectively) were isolated in high yields and converted to potential antiinflammatory acids 6, 8, 15 and lactones 4 , 7. 相似文献
305.
The palladium-catalyzed cross-coupling of cyclic thioamides with arylboronic acids in the presence of stoichiometric amounts of a copper(I) cofactor is described. The desulfitative carbon-carbon cross-coupling protocol is performed under neutral conditions and can be applied to a range of heterocyclic structures with embedded thioamide fragments. Successful carbon-carbon cross-coupling is independent of the ring size, aromaticity/nonaromaticity, the presence of additional heteroatoms, or other functional groups in the starting thioamide structure. Employing controlled microwave irradiation at 100 degrees C, most cross-couplings can be completed within 2 h and proceed in high yields. An advantage of using thioamides as starting materials is the fact that the system can be tuned to an alternative carbon-sulfur cross-coupling pathway by changing to stoichiometric copper(II) under oxidative conditions. Both types of thioamide cross-couplings are orthogonal to the traditional base-catalyzed Suzuki-Miyaura cross-coupling of aryl halides with boronic acids. 相似文献
306.
Several important types of ozonolysis reactions have been performed in a continuous flow device that is able to perform both the ozonolysis and quenching steps in flow mode. This technique allows safe and scalable ozonolysis reactions to be performed on a laboratory scale. 相似文献
307.
Bianca C. Wallfisch Tamara Egger Werner Heilmayer C. Oliver Kappe Curt Wentrup Karsten Gloe 《Supramolecular chemistry》2013,25(5):383-397
The unusual chiral heterocyclic systems, trioxabicyclo[3.3.1]nona-3,7-dienes ("bridged bisdioxines"), are incorporated as novel spacer molecules into macrocyclic polyether ring systems of various sizes (8, 9 as well as 11-15) by cyclocondensation reaction of the bisacid chloride 4b or bisesters 6,7 and 10, with several ethylene glycols. The 2:2 macrocycles 12-14 are obtained in approximately 50:50 mixtures of diastereomers. These conclusions are mainly based on HPLC data presented in Table I as well as X-ray analyses of (1R,5R)-8c (space group Pbca, a =10.163(3) Å, b =18.999(4) Å, c =36.187(10) Å, V =6987(3) Å3 , Z =8, d calc =1.218 g cmm 3, 6974 reflections, R =0.0553), meso/rac-11 (space group P1 ¥ , a =10.472(5) Å, b=16.390(5) Å, c =17.211(5) Å, f =98.69(2)°, g =93.04(2)°, n =98.52(2)°, V =2879.3(18) Å 3 , Z =2, d calc =1.173 g cm m 3 , 11,162 reflections, R =0.0945) and meso-12 (space group P21/c, a =9.927(2), b =18.166(3), c =17.820(3) Å, g =96.590(10)°, V =3192.3(10) Å 3 , Z =4, D c =1.109 g cmm 3, 3490 reflections, R =0.0646). The 1:1 macrocycles 8b,c are also formed by intramolecular transesterification of the open-chain bisesters 7b,c and their formation is favored by the use of metal ions as templates. The bridged bisdioxine moieties in 8b and 12 are converted into the corresponding chiral tetraoxaadamantane spacers to afford macrocycles 16 and 17. Preliminary metal ion complexation studies with selected species (8c, 11-14) were also performed. 相似文献
308.
In this review, published applications of microwave-assisted derivatization procedures for gas chromatography/mass spectrometry
(GC/MS) are summarized. Among the broad range of analytical techniques available, GC/MS is still the method of choice for
most high-throughput screening procedures in forensic/clinical toxicology, doping control and food and environmental analysis.
Despite the many advantages of the GC/MS method, time-consuming derivatization steps are often required in order to obtain
desirable chromatographic characteristics or to improve the stability and detectability of the target analytes. These derivatization
processes typically require reaction times from 30 min up to several hours at elevated temperature. In contrast, microwave
protocols have demonstrated to be able to reduce the time required for derivatization to a few minutes, and can thus very
effectively shorten the overall analysis time, in particular when carried out in a high-throughput format. Herein, the literature
in this field is summarized and recent experimental techniques for performing parallel GC/MS derivatization protocols are
discussed. 相似文献