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51.
52.
Henri-Jean Cristau Marie-Benedicte Gasc Xavier Yangkou Mbianda Annabelle Geze 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract In the aim to carry out a quantitative reactivity/structure/biological activity relationship, a general four step synthesis, gives us access to a number of new phosphomycin analogues. A new synthesis of di- and tri-substituted vinylphosphonates via cuprate reactions and their epoxidation by dioxirane are described. 相似文献
53.
54.
I. Bruns A. Siebert R. Baumbach J. Miersch D. Günther B. Markert G.-J. Krauß 《Analytical and bioanalytical chemistry》1995,353(1):101-104
The water moss Fontinalis antipyretica has been investigated to estimate heavy metal pollution in the river Elbe (middle Germany). Procedures of plant separation, digestion as well as an analytical method for ICP-MS analyses have been evaluated. Reproducibility and accuracy have been demonstrated on BCR 61 (NIST) reference material and results have been compared with AAS and AES data. The distribution of heavy metals in different plant segments of indigenous material has been analyzed. Exposition of plant material in the river Elbe have shown no correlation between the heavy metal content in plants and that of water samples. Cd and Zn concentrations found in the plant material are significantly enriched relatively to control samples. To understand the sophisticated ‘real system’ experiments have been carried out under laboratory conditions to investigate induced sulphur-rich compounds in the presence of heavy metals using HPLC including on-line derivatization. 相似文献
55.
I. Bruns A. Siebert R. Baumbach J. Miersch D. Günther B. Markert G.-J. Krau? 《Fresenius' Journal of Analytical Chemistry》1995,353(1):101-104
The water moss Fontinalis antipyretica has been investigated to estimate heavy metal pollution in the river Elbe (middle Germany). Procedures of plant separation, digestion as well as an analytical method for ICP-MS analyses have been evaluated. Reproducibility and accuracy have been demonstrated on BCR 61 (NIST) reference material and results have been compared with AAS and AES data. The distribution of heavy metals in different plant segments of indigenous material has been analyzed. Exposition of plant material in the river Elbe have shown no correlation between the heavy metal content in plants and that of water samples. Cd and Zn concentrations found in the plant material are significantly enriched relatively to control samples. To understand the sophisticated real system experiments have been carried out under laboratory conditions to investigate induced sulphur-rich compounds in the presence of heavy metals using HPLC including on-line derivatization. 相似文献
56.
Shi Shun AL Chernick ET Eisler S Tykwinski RR 《The Journal of organic chemistry》2003,68(4):1339-1347
Unsymmetrically substituted 1,3-butadiynes and 1,3,5-hexatriynes are synthesized in four steps from commercially available aldehydes or carboxylic acids. The key step in this process involves a Fritsch-Buttenberg-Wiechell rearrangement, in which an alkylidene carbenoid intermediate subsequently rearranges to the desired polyyne. This rearrangement proceeds under mild conditions, and it is tolerant of a range of functionalities. In general, the procedurally facile formation of the dibromoolefinic precursors, in combination with the effectiveness of the rearrangement step, makes this procedure an attractive alternative to traditional methods for di- and triyne synthesis that utilize palladium or copper catalysis. 相似文献
57.
The two chiral spiro nucleosides 4 and 5 containing the barbituric acid moiety were efficiently synthesized from optically pure precursors, and their properties were studied. The carbocyclic nucleoside 5 is considerably more stable against ring opening than the deoxyribosyl derivative 4. Both compounds present enhanced hydrogen bonding capacity with diacetyladenosine. 相似文献
58.
Naturally occurring mosquito larvicidal acetylenes 1 and 2, and analogues 3 and 4, each containing either a 1,3-butadiynyl or a 1,3,5-hexatriynyl moiety, are synthesized via a Fritsch-Buttenberg-Wiechell rearrangement. The alkylidene carbenoid intermediate results from lithium-halogen exchange of a suitable dibromoolefin precursor, and the rearrangement is accomplished under mild conditions. Synthesis of the dibromoolefin precursors to acetylenes 1-4 is easily achieved in three steps from commercially available carboxylic acids or aldehydes, making this procedure a viable alternative to conventional methods for the synthesis of naturally occurring acetylenes. 相似文献
59.
Swanhild Bernstein Svend Ebert Rolf Sören Kraußhar 《Mathematical Methods in the Applied Sciences》2011,34(4):428-441
In this paper we study the solutions to the diffusion equation on some conformally flat cylinders and on the n‐torus. Using the Clifford algebra calculus with an appropriate Witt basis, the solutions can be expressed as multiperiodic eigensolutions to the parabolic Dirac operator. We study their fundamental properties, give representation formulas of all these solutions and develop some integral representation formulas. In particular we set up a Green type formula for the solutions to the homogeneous diffusion equation on cylinders and tori. Then we also treat the inhomogeneous diffusion equation diffusion with prescribed boundary conditions in Lipschitz domains on these manifolds. As main application, we construct well localized diffusion wavelets on this class of cylinders and tori by means of multiperiodic eigensolutions to the parabolic Dirac operator. We round off with presenting some concrete numerical simulations for the three dimensional case. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
60.
Brian J. Brisdon Michael Cartwright Annabelle G. Hodson 《Journal of organometallic chemistry》1984,277(1):85-90
Dissolution of [MoCl(CO)2(η3-C3H4R)(NCMe)2] (R = H or Me) in methanol yields yellow conducting solutions containing the [Mo(CO)2(η3-C3H4R)(HOMe)3]+ cations. The same species are formed on dissolution of [Mo(CO)2(η3-C3H4R)(NCMe)3]BF4 in methanol, and one of the cations (R = Me) has been isolated as its tetrafluoroborate salt. There is strong spectroscopic evidence that hydrated allyldicarbonylmolybdenum(II) cations [Mo(CO)2(η3-C3H4R)(H2O)x]+ are present on dissolution of [MoCl(CO)2(η3-C3H4R)(NCMe)2] in deoxygenated water, and treatment of these solutions with bi- and tridentate ligands yields neutral complexes [MoCl(CO)2(η3-C3H4R)L2] (R = H or Me; L2 = 2,2′-bipyridine (bipy) or 2,2′-bipyridylamine (bpa)), and cationic species [Mo(CO)2(η3-C3H4R)L3]+ (R = H or Me; L3 = diethylenetriamine (dien) or bis(2-pyridylmethyl)amine (bpma)) respectively. The latter were isolated as their hexafluorophosphate salts. Addition of Ph4AsCl to basic methanolic solutions of [MoCl(CO)2(η3-C3H4R)(NCMe)2] causes the precipitation of the anionic molybdenum derivatives Ph4As[Mo2(CO)4(η3-C3H4R)2(μ-OMe)3] (R = H or Me). 相似文献