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81.
Patrick M. O'Donnell Kenneth B. Wagener 《Journal of polymer science. Part A, Polymer chemistry》2003,41(18):2816-2827
Precise graft copolymer architectures were achieved by combining the macromonomer technique with the acyclic diene metathesis (ADMET) reaction. These well‐defined copolymer structures were the result of proper monomer design before metathesis polymerization. Features such as length of the graft, nature, and concentration of the graft site along the backbone were manipulated via the combination of living atom transfer radical polymerization methods with ADMET chemistry. Furthermore, the physical behavior of these materials was altered such that they presented dissimilar thermal properties of either the homopolymers or random copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2816–2827, 2003 相似文献
82.
Recep Özen Kutalmis Guven Hatice Can Metin Balci 《Journal of chemical crystallography》2004,34(7):477-481
The title compound 6-phenyl-4,6,8-triazatetracyclo[9.2.1.02,10.04,8]tetradec-2(10)-ene-5,7-dione (6) has been synthesized by the addition of 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) to 2,3-dimethylenebicyclo[2.2.1]heptane. The cell parameters are a = 9.991(5), b = 11.754(9), c = 6.549(5) Å, = 101.08(7)°, = 103.31(5)°, = 98.24(5)°. The crystal structure of 6 was determined. The obtained geometrical parameters were highly correlated with the DFT calculations. The experimentally determined folding angle of the double bond was found to be 8.44°. The effect of the electron-withdrawing ability of nitrogen atom on the degree of pyramidalization is discussed. 相似文献
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Regio‐and stereo‐selective Diels–Alder reaction of 3‐methylpenta‐1,2,4‐trienyl phenyl sulfoxide with maleic anhydride in the absence or presence of a Lewis acid as catalyst with formation of sulfinyl‐substituted benzofuran or norbornene cycloadducts, respectively, is described. 相似文献
87.
Rachel E. M. Brooner Dr. Timothy J. Brown Prof. Ross A. Widenhoefer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8276-8284
Cationic, two‐coordinate triphenylphosphine–gold(I)–π complexes of the form [(PPh3)Au(π ligand)]+ SbF6? (π ligand=4‐methylstyrene, 1? SbF6), 2‐methyl‐2‐butene ( 3? SbF6), 3‐hexyne ( 6? SbF6), 1,3‐cyclohexadiene ( 7? SbF6), 3‐methyl‐1,2‐butadiene ( 8? SbF6), and 1,7‐diphenyl‐3,4‐heptadiene ( 10? SbF6) were generated in situ from reaction of [(PPh3)AuCl], AgSbF6, and π ligand at ?78 °C and were characterized by low‐temperature, multinuclear NMR spectroscopy without isolation. The π ligands of these complexes were both weakly bound and kinetically labile and underwent facile intermolecular exchange with free ligand (ΔG≠≈9 kcal mol?1 in the case of 6? SbF6) and competitive displacement by weak σ donors, such as trifluoromethane sulfonate. Triphenylphosphine–gold(I)–π complexes were thermally unstable and decomposed above ?20 °C to form the bis(triphenylphosphine) gold cation [(PPh3)2Au]+SbF6? ( 2? SbF6). 相似文献
88.
J. Wayne Mullinax David S. Hollman Prof. Henry F. Schaefer III 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7487-7495
Germanium has been a central feature in the renaissance of main‐group inorganic chemistry. Herein, we present the stationary‐point geometries of tetragermacyclobutadiene and its related isomers on the singlet potential energy surface at the CCSD(T)/cc‐pVTZ level of theory. Three of these 12 structures are reported for the first time and one of them is predicted to lie only 0.4 kcal mol?1 above the previously reported global minimum. Focal‐point analyses has provided electronic energies at the CCSD(T) level of theory, which are extrapolated to the complete basis‐set limit and demonstrate the convergence behavior of the electronic energies with improving levels of theory and increasing basis‐set size. The lowest‐energy structure is the bicyclic structure, which lies 35 kcal mol?1 below the “all‐Ge” cyclobutadiene structure. The reaction energies for the association of known Ge hydrides (e.g., digermene) to form Ge4H4 indicate that Ge4H4 could be observed experimentally. We investigate the bonding patterns by examining the frontier molecular orbitals. Our results demonstrate that: 1) the cyclic isomers of (GeH)4 distort to maximize the mixing of the p orbitals that are involved in the π system of tetragermacyclobutadiene and 2) the lowest‐energy isomers exhibit unusual bonding arrangements (e.g., bridging H bonds) that maximize the nonbonding electron density at the Ge centers. 相似文献
89.
James Y. Hamilton Nicole Hauser Dr. David Sarlah Prof. Dr. Erick M. Carreira 《Angewandte Chemie (International ed. in English)》2014,53(40):10759-10762
An enantioselective allyl–allylsilane cross‐coupling involving racemic branched allylic alcohols and allylsilanes is reported. An iridium‐(P,olefin) phosphoramidite complex enables the transformation with high regio‐ and stereoselectivity under operationally simple conditions. The utility of the coupling is demonstrated in a concise catalytic, enantioselective synthesis of a pyrethroid insecticide protrifenbute. 相似文献
90.
Asymmetric Hetero‐Diels–Alder Reaction of Danishefsky’s Diene with α‐Ketoesters and Isatins Catalyzed by a Chiral N,N′‐Dioxide/Magnesium(II) Complex
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Jianfeng Zheng Dr. Lili Lin Kai Fu Yulong Zhang Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14493-14498
A highly enantioselective hetero‐Diels–Alder reaction of Danishefsky’s diene with α‐ketoesters and isatins has been realized by using a chiral N,N′‐dioxide/MgII complex. In the presence of only 0.1–0.5 mol % catalyst, a series of substrates were transformed into the corresponding tetrasubstituted 2,3‐dihydropyran‐4‐ones in up to 99 % yield and more than 99 % ee in two hours. 相似文献