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51.
Seiji Yamaguchi Masao Mutoh Masaaki Shimakura Kunihiro Tsuzuki Yoshiyuki Kawase 《Journal of heterocyclic chemistry》1991,28(1):119-123
Some ω-(3-chromonyl)alkanoic acid derivatives, 1a and 2a , n = 4, 5; 3a, 4a and 5a , n = 2-6, were synthesized by cyclization of corresponding methyl ω-(2-hydroxybenzoyl)alkanoates 7b or ethyl ω-(2,4-dihydroxybenzoyl)alkanoates 8b with N,N-dimethylformamide-dimethyl acetal or acetic anhydride-DBU followed by hydrolysis. 相似文献
52.
Changes in Si(111) 7 × 7 pattern with air exposure are studied by RHEED. The relation between exposure time and air-oxidized film thickness is obtained using an ellipsometer. As a result, it is found that the 7 × 7 surface after air exposure (760 Torr, 20 h) still exhibits several 7 × 7 spots near normal ones in the RHEED pattern. The air-oxidized film thickness corresponding to this exposure is about 13 Å. The fact that the 7 × 7 spots do not disappear with HF etching of the oxide film indicates that the superstructure remains not at the oxide surface but at the substrate selvedge. The 7 × 7 spots gradually disappear after longer exposure time and no 7 × 7 spots can be observed after 40 h (about 15 Å in oxide thickness). For a sample exposed longer than 40 h, no 7 × 7 spots reappear, even if the oxide is removed by HF. Therefore, it is concluded that the structure of the substrate selvedge changes with exposure time. 相似文献
53.
54.
Seiji Miyano Shinichiro Fujii Osamu Yamashita Naoko Toraishi Kunihiro Sumoto 《Journal of heterocyclic chemistry》1982,19(6):1465-1468
A facile synthesis of Δ1[9]- and/or Δ8[9]-dehydroindolizidine and related compounds, consisting of dry distillation of γ-(N-2-piperidinonyl)butyric acid over soda-lime, is described. Reductions of these dehydroindolizidines and stereochemistry of 1-methylindolizidine are also described. 相似文献
55.
56.
Hamdan A.S. Al-Shamiri Maram T.H. Abou Kana Ahmed H.M. Elwahy 《Optics Communications》2010,283(7):1438-5338
The synthesis of new high-performance dyes and the implementation of new ways of incorporating the organic molecules into the solid host matrices have produced a great deal of activity in the field of solid-state dye lasers. In this article, the new laser dye, 2-(6-allyl-3-oxo-3H-xanthen-9-yl)-benzoic acid ethyl ester [AXBE] has been synthesized, and its chemical structure was confirmed by 1H NMR, 13C NMR, IR and elemental analysis. This new dye was covalently bonded with methyl methacrylate (MMA) and 2-hydroxy ethyl methacrylate (HEMA) copolymer backbone and evaluated as the active medium of the solid-state laser dye. Its optical properties were experimentally investigated. Amplified spontaneous emission (ASE) and photostability were studied by pumping the dye sample with 355 nm (8 ns) pulsed Nd-YAG laser. 相似文献
57.
Kuntrapakam Hema Kana M. Sureshan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2780-2785
The topochemical synthesis of a miscible polymer blend is described. The azide‐ and alkyne‐decorated tetrol 1 crystallizes as two different conformers. Both conformers exhibit self‐sorted head‐to‐tail alignment with proximally placed reacting groups such that topochemical polymerization yields two types of polymer chains, each containing only one type of conformer. The orientation of complementary reactive groups in one of the head‐to‐tail‐arranged conformers favors the formation of cis‐triazole linkages, and the other favors the trans‐triazole linkages. Crystals of 1 on heating gave a perfect polymer blend containing equal amounts of cis‐triazole‐linked and trans‐triazole‐linked polymers. As each conformer is H‐bonded to four conformers of the other kind, the polymerization yields a perfect polymer blend wherein each polymer chain is surrounded by chains of the other type. Thus, the molecular ordering in the prepolymerized state in a crystal is utilized to create a polymer blend. 相似文献
58.
Sureshan KM Trusselle M Tovey SC Taylor CW Potter BV 《The Journal of organic chemistry》2008,73(5):1682-1692
Adenophostin A (AdA) is a potent agonist of the d-myo-inositol 1,4,5-trisphosphate receptor (Ins(1,4,5)P3R). Various 2-aminopurine analogues of AdA were synthesized, all of which (guanophostin 5, 2,6-diaminopurinophostin 6, 2-aminopurinophostin 7, and chlorophostin 8) are more potent than 2-methoxy-N6-methyl AdA, the only benchmark of this class. The 2-amino-6-chloropurine nucleoside 11, from Vorbrüggen condensation of 2-amino-6-chloropurine with appropriately protected disaccharide, served as the advanced common precursor for all the analogues. Alcoholysis provided the precursor for 5, ammonolysis at high temperature the precursor for 6, and ammonolysis under mild conditions the precursor for synthesis of 7 and 8. For 8, the debenzylation of precursor leaving the chlorine untouched was achieved by judicious use of BCl3. The reduced potency of chlorophostin 8 and higher potency of guanophostin 5 in assays of Ca2+ release via recombinant Ins(1,4,5)P3R are in agreement with our model suggesting a cation-pi interaction between AdA and Ins(1,4,5)P3R. The similar potencies of 2,6-diaminopurinophostin (6) and 2-aminopurinophostin (7) concur with previous reports that the 6-NH2 moiety contributes negligibly to the potency of AdA. Molecular modeling of the 2-amino derivatives suggests an interaction between the carboxylate side chain of Glu505 of the receptor and the 2-NH2 of the ligand, but for 2-methoxy-N6-methyl AdA the carboxylate group of Glu505 is deflected away from the methoxy group. A helix-dipole interaction between the 1-phosphate of Ins(1,4,5)P3 and the 2'-phosphate of AdA with alpha-helix 6 of Ins(1,4,5)P3R is postulated. The results support a proposed model for high-affinity binding of AdA to Ins(1,4,5)P3R. 相似文献
59.
Takeuchi T Akeda K Murakami S Shinmori H Inoue S Lee WS Hishiya T 《Organic & biomolecular chemistry》2007,5(15):2368-2374
A novel photoresponsive functional monomer bearing diaminopyridine and azobenzene moieties was synthesized and applied to the preparation of photo-regulated molecularly imprinted polymers, which can recognize porphyrin derivatives through hydrogen bonding. The binding affinity of the imprinted cavities was regulated by UV irradiation, suggesting that azobenzene groups located inside the binding sites worked as photosensitizers and the trans-cis isomerization could regulate the affinity for the target compounds. Repetitive binding of the target compound to trans-IP and cis-IP was directly monitored by slab optical waveguide spectroscopy and the photo-mediated regulation of binding affinity was successfully confirmed. 相似文献
60.
The closure by cyclization with diethyl carbonate (EtO)(2)CO from aminoalcohols 1 as starting material can lead to the oxazolidinones 2a, b and 2c, respectively. In the reaction of trans-isomer (6) and (EtO)(2)CO, isolated products were also only 5-membered oxazolidinone derivative (7), containing its dehydrated derivative 8. The preferential formation of the 5-membered oxazolidinone ring system apparently indicated that this process (5-Exo-Trig ring closure) is more favorable than that of 6- or 7-membered ring derivative (3 or 9) by 6- or 7-Exo-Trig ring closure. 相似文献