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71.
Nobuyuki Tomioka Daisuke Takasu Toshie Takahashi Takuzo Aida 《Angewandte Chemie (International ed. in English)》1998,37(11):1531-1534
Carboxylate and ammonium functionalities—32 of each— facilitate electrostatic interaction between oppositely charged dendrimer electrolytes and porphyrin cores, which leads in protic media to a supramolecular, fluorescence-active aggregate of two chromophores that communicate and have a predictable topology (see drawing on the right; A=acceptor, D=donor). In contrast to the complexation of linear polyelectrolytes, the contact area for the two dendrimer molecules is very limited, just as one would expect for an assembly of spherical molecules. 相似文献
72.
Evgueni L. Piatnitski Kurt D. Deshayes 《Angewandte Chemie (International ed. in English)》1998,37(7):970-972
Cleavage of one of the four bridging units in the two new types of hemicarceplexes presented here is sufficient to effect immediate guest release into the chloroform solvent (shown schematically on the right). The thermal stability and photoactivity of these hemicarceplexes indicate that incarceration is potentially useful for the controlled delivery of drugs. 相似文献
73.
Astrid M. Müller Stefan Lochbrunner Wolfram E. Schmid Werner Fuß 《Angewandte Chemie (International ed. in English)》1998,37(4):505-507
What is the standard course of the cis – trans isomerization of nonpolar polyenes? Many results support a pathway in which only a central CH group rotates out of the plane, while the remaining parts of the molecule reorient within the plane (“hula-twist” mechanism). The intermediate structure through which the molecule passes corresponds to the geometry predicted for the conical intersection of the S1 and S0 potential energy surfaces (see picture). 相似文献
74.
Dietmar Leipert Peter Heiduschka Jürgen Mack Hans-Joachim Egelhaaf Dieter Oelkrug Günther Jung 《Angewandte Chemie (International ed. in English)》1998,37(17):2337-2340
Microstructuring of surfaces: Electrochemical polymerization after removal of a photolabile protecting group (nitrobenzyl group) represents a new method for spatially resolved immobilization of ligands or receptors. Thus, the electropolymerization of 3-hydroxyphenylacetyl peptides such as 1 on electrodes can be controlled by light 相似文献
75.
Hans-Joachim Knlker Helmut Goesmann Rüdiger Klauss 《Angewandte Chemie (International ed. in English)》1999,38(5):702-705
The photochemical exchange of all three carbonyl ligands with acetonitrile converts tricarbonyliron–diene complexes into the very labile triacetonitrile-iron–diene complexes. These easily demetalate in high yields to the corresponding free ligands on injection of air at −30°C [Eq. (1)]. The novel demetalation procedure is applied to the tricarbonyliron complexes of cyclopentadienones, cyclohexa-1,3-dienes, and buta-1,3-dienes. 相似文献
76.
Kazuo Watanabe Yoshiyasu Matsumoto Margarethe Kampling Katharina Al-Shamery Hans-Joachim Freund 《Angewandte Chemie (International ed. in English)》1999,38(15):2192-2194
The mean size of the Pd clusters deposited on an Al2O3 thin film influences the efficiency of photodissociation of CD4 into CD3 and D as well as the photodesorpion upon irradiation with 193-nm laser light. The picture shows the degree of desorption on Pd clusters of various sizes (as well as on a Pd(111) single-crystal surface) as a function of temperature; the values given refer to the average thickness of the evaporated metal layer. 相似文献
77.
Tong-Ing Ho Jin-Yi Wu Shun-Li Wang 《Angewandte Chemie (International ed. in English)》1999,38(17):2558-2560
A conrotatory photocyclization , a novel [1,9] hydrogen shift, and a lateral ring opening are involved in the rearrangement of a series of 2-(4-alkylstyryl)furans 1 to 5-(3-alkylbutadienyl)benzo[b]furans 2 in dichloromethane. These novel photochemical rearrangements occur with good yields of isolated products. 相似文献
78.
New β,β′-aryl/heteroaryl 2,3-divinylfuran derivatives (9a-d) in which a hexatriene system is a part of heteroaromatic ring have been synthesized and their photochemical properties were investigated. The primary process observed was the isomerization to trans,trans-isomers 9a-d followed by photochemical rearrangement of the furan ring giving the phototransposition products (I-IV). Stilbenes (20, 21) and phenanthrenes (22, 25, and 26), formed as secondary products from the competitive intermolecular cycloadditions, were also observed. 相似文献
79.
80.
Emad Yousif Emaad Bakir Jumat Salimon Nadia Salih 《Journal of Saudi Chemical Society》2012,16(3):279-285
The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φcs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10?5 and 8.75 × 10?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested. 相似文献