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21.
《Tetrahedron letters》2019,60(24):1582-1586
Rh(II)-catalyzed decomposition of certain cyclic α-diazocarbonyl compounds in the presence of cyclic ethers has been shown to give bicyclic ring expansion products. These are thought to arise from a [1,4]-alkyl shift toward the carbonyl oxygen atom and are in contrast with the recently observed spirocyclic products of a Stevens-type [1,2]-alkyl shift within the postulated oxonium ylide intermediate. Quantum chemical calculations performed at the B3LYP/6-31G* level of theory showed that the former reaction pathway (toward fused bicycles) is kinetically preferred. 相似文献
22.
Priyabrata Pattanaik Sabita Nayak Deepak Ranjan Mishra Pravati Panda Bishnu Prasad Raiguru Nilima Priyadarsini Mishra Seetaram Mohapatra N. Arjunreddy Mallampudi Chandra Shekhar Purohit 《Tetrahedron letters》2018,59(27):2688-2694
A competent and highly discriminating one-pot synthesis of highly diversified novel functionalized indenoquinoxalone grafted spiropyrrolidine linked chromene-3-carbonitrile conjugates accumulating three pharmocophoric cores, heterocyclic indenoquinoxalone, pyrrolidines and chromene-3-carbonitrile in a single molecular framework by means of 1,3-dipolar cycloaddition reaction between indenoquinoxalone, proline/benzyl amine and chromene-3-carbonitrile in ethanol under classical and microwave conditions is described. The three component 1,3-dipolar cycloaddition reaction proceeds via in situ generation of azomethine ylides by the decarboxylative condensation of indenoquinoxalone with proline/benzyl amine and their selectivity towards the endo cyclic double bonds of dipolarophile (chromene-3-carbonitrile) leading to the formation of highly functionalised regio- and diastereoselective molecular hybrids. This methodology exemplifies the green chemistry protocol such as mild reaction conditions, high yields, one-pot procedure and operational simplicity. 相似文献
23.
酮与稳定膦叶立德在家用微波炉中加热,在无任何溶剂或固体介质条件下,4.5min之内完成反应,得到了良好产率的Wittig反应产物,较之液相苯中回流反应的传统方法,此法具有时间短、操作步骤简单、无毒害等优点,同时使一些在传统方法中与稳定叶立德不反应或难反应的酮得以进行并有较好收率。此外,在得到α,β-不饱和酯的同时,还发现了少量重排产物β,γ-不饱和酯,并对其机理进行了推测与证明。 相似文献
24.
A new, one-step procedure for the generation of azomethine ylides, 4 and 20, via chloroiminium salts, 3 and 19, is reported. The generation of the azomethine ylides was confirmed by their trapping with dimethyl acetylenedicarboxylate (DMAD) which, upon spontaneous 1,4-dehydrochlorination, gave the corresponding pyrroles 17 and 21. 相似文献
25.
Although several different groups have studied the photolysis of phosphorus ylides, none have utilized e. s. r. to support the postulated decomposition mechanisms. The fundamental question which awaits a definitive answer is which bond breaks first upon photolysis. Tschesche1 and de Silva2 utilizing the ylides (1) and (2) suggested that the carbon-phosphorus double bond was initially broken while Nagao3 using (3) proposed phenyl-phosphorus bond cleavage. 相似文献
26.
M. M. Sidky M. R. Mahran A. A. El-kateb I. T. Hennawy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):409-412
Abstract Trialkyl phosphites react with quinisatin (1) and its monohydrate 3 to give the corresponding phosphate derivatives 2a-c. The same compounds are obtained upon reacting 1 and/or 3 with the proper dialkyl phosphite. Structural reasonings based on IR, MS and NMR spectral data, are presented. 相似文献
27.
Malek Taher Maghsoodlou Norollah Hazeri Ghafar Afshari Uranous Niroumand 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2681-2689
The reaction of triphenylphosphine with dialkyl acetylenedicarboxylates in the presence of a strong SH-acid or NH-acid, such as 2-mercaptobenzoxazole and 2-benzoxazolinone, has been studied. In some cases, stable phosphorus ylides are obtained in excellent yields. The ylide moiety of these compounds is strongly conjugated with the adjacent carbonyl group, and the rotation about the partial double bond in (E) and (Z) geometrical isomers is slow on the NMR time scale at an ambient temperature. Thus, these exist as a mixture of geometrical isomers. 相似文献
28.
Yoshiaki Miyamoto Norihiro Wada Dr. Takahiro Soeta Dr. Shuhei Fujinami Prof. Dr. Katsuhiko Inomata Prof. Dr. Yutaka Ukaji 《化学:亚洲杂志》2013,8(4):824-831
The stereoselective direct transformation of N‐(propargylic)hydroxylamines into cis‐2‐acylaziridines was achieved by the combined use of AgBF4 and CuCl. Copper salts were found to promote the transformation of the intermediary 4‐isoxazolines into 2‐acylaziridines and both 3‐aryl‐ and 3‐alkyl‐substituted 2‐acylaziridines could be prepared by using this method. Furthermore, subsequent 1,3‐dipolar cycloaddition of azomethine ylides that were generated in situ from the intermediary 2‐acylaziridines with maleimides was achieved in a stereoselective one‐pot procedure to afford the corresponding 2‐acylpyrrolidines, which consisted of an octahydropyrrolo[3,4‐c]pyrrole skeleton. 相似文献
29.
30.
Subban Kathiravan 《合成通讯》2013,43(20):3068-3076
Facile synthesis of a series of naphtho[2,1,b]pyrano pyrrolo thiazoles was accomplished in good yields in a one-pot reaction through intramolecular 1,3-dipolar cycloaddition of cyclic azomethine ylides with Baylis–Hillman adducts as dipolarophiles. The protocol is applicable to a wide variety of photochromic and biologically active napthopyrano products. The regio- and stereochemical outcome of the cycloaddition reaction was ascertained by x-ray crystallographic study of one of the cycloadducts. 相似文献