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711.
712.
Multiple Zeta Values at Non-Positive Integers 总被引:2,自引:0,他引:2
Values of Euler-Zagier's multiple zeta function at non-positive integers are studied, especially at (0,0,...,–n) and (–n,0,...,0). Further we prove a symmetric formula among values at non-positive integers. 相似文献
713.
Kazunari Naka Hirofumi Sato Akihiro Morita Fumio Hirata Shigeki Kato 《Theoretical chemistry accounts》1999,102(1-6):165-169
The free-energy profile for the Menshutkin-type reaction NH3 + CH3Cl → NH3CH3
+ + Cl− in aqueous solution is studied using the RISM-SCF method. The effect of electron correlation on the free-energy profile is
estimated by the RISM-MP2 method at the HF optimized geometries along the reaction coordinate. Solvation was found to have
a large influence on the vibrational frequencies at the reactant, transition state and product; these vibrational frequencies
are utilized to calculate the zero-point energy correction of the free-energy profile. The computed barrier height and reaction
exothermicity are in reasonable agreement with those of experiment and previous calculations. The change of solvation structure
along the reaction path is represented by radial distribution functions between solute-solvent atomic sites. The mechanisms
of the reaction are discussed from the view points of solute electronic and solvation structures.
Received: 26 June 1998/Accepted: 28 August 1998 / Published online: 2 November 1998 相似文献
714.
Tetsuya Minobe Takayuki Uchihashi Takahiro Tsukamoto Shigeki Orisaka Yasuhiro Sugawara Seizo Morita 《Applied Surface Science》1999,140(3-4)
Atomic resolution imaging of the Si(111)
×
R30°–Ag surface was investigated using a noncontact atomic force microscopy (NC-AFM) in ultrahigh vacuum. NC-AFM images showed three types of contrasts depending on the distance between an AFM tip and a sample surface. When the tip–sample distance was about 1–3 Å, the images showed the honeycomb arrangement with weak contrast. When the tip–sample distance was about 0–0.5 Å, the images showed the periodic structure composed of three bright spots with relatively strong contrast. On the other hand, the contrasts of images measured at the distance of 0.5–1 Å seemed to be composed of the above-mentioned two types of contrasts. By comparing the site of bright spots in the AFM images with honeycomb-chained trimer (HCT) model, we suggested the following models: when the tip is far from the sample surface, tip–sample interaction force contributing to imaging is dominated by physical bonding interaction such as Coulomb force and/or van der Waals (vdW) force between the tip apex Si atoms and Ag trimer on the sample surface. On the other hand, just before the contact, tip–sample interaction force contributing to imaging is dominated by chemical bonding such as the force due to hybridization between the dangling bond out of the tip apex Si atom and the orbit of Si–Ag covalent bond on the sample surface. 相似文献
715.
Shigeki Habaue Hiroharu Ajiro Yoshio Okamoto 《Journal of polymer science. Part A, Polymer chemistry》2000,38(22):4088-4094
Ortho‐substituted styrenes, such as 2‐(N,N‐dimethylaminomethyl)styrene ( 1 ), 2‐(1‐pyrrolidinylmethyl)styrene ( 2 ), and 2‐[(S)‐2‐(1‐pyrrolidinylmethyl)‐1‐pyrrolidinylmethyl]styrene ( 3 ), were synthesized, and the effects of the ortho‐substituents on the polymerizability and stereoregularity of the obtained polymers using the anionic method were examined. The bulkiness and coordination of the ortho‐substituted amino groups to the counter cation significantly affected the polymerizability and stereochemistry of the obtained polymers. The anionic and radical polymerizations of 2 with a less hindered ortho‐substituent afforded polymers in good yields, whereas those of 1 and 3 resulted in lower yields. The anionic polymerization of 3 bearing an optically active diamine derivative at the ortho‐position with n‐butyllithium in toluene at 0 °C gave a polymer with a high stereoregularity and stable regular conformation based on the stereoregular backbone structure. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4088–4094, 2000 相似文献
716.
Takehiko Iida Noriyoshi Yamamoto Shigeki Matsunaga Hee-Gweon Woo Masakatsu Shibasaki 《Angewandte Chemie (International ed. in English)》1998,37(16):2223-2226
Useful chiral building blocks such as 1,2-diols can be obtained by the enantioselective ring opening of achiral epoxides with oxygen nucleophiles. The ring opening is carried out effectively (up to 94 % ee) with 4-methoxyphenol and catalytic amounts of gallium complexes. The novel complex GaSO 1 displays a particularly high catalytic activity. 相似文献
717.
Yoshio Okamoto Shigeki Habaue Yutaka Isobe Yoshikatsu Suito 《Macromolecular Symposia》2003,195(1):75-80
The radical polymerization of various (meth)acrylamides in the presence of Lewis acids such as Yb(OTf)3 and Y(OTf)3 was carried out. The polymerization with Lewis acids led to highly isotactic polymers, while the polymers synthesized without Lewis acids were atactic or syndiotactic. The dependence of the polymer properties on the tacticity was also demonstrated. 相似文献
718.
Xiushang Xu Kewei Sun Atsushi Ishikawa Akimitsu Narita Shigeki Kawai 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302534
Graphene nanoribbons (GNRs) and nanographenes synthesized by on-surface reactions using tailor-made molecular precursors offer an ideal playground for a study of magnetism towards nano-spintronics. Although the zigzag edge of GNRs has been known to host magnetism, the underlying metal substrates usually veil the edge-induced Kondo effect. Here, we report the on-surface synthesis of unprecedented, π-extended 7-armchair GNRs using 7-bromo-12-(10-bromoanthracen-9-yl)tetraphene as the precursor. Characterization by scanning tunneling microscopy/spectroscopy revealed unique rearrangement reactions leading to pentagon- or pentagon/heptagon-incorporated, nonplanar zigzag termini, which demonstrated Kondo resonances even on bare Au(111). Density functional theory calculations indicate that the nonplanar structure significantly reduces the interaction between the zigzag terminus and the Au(111) surface, leading to a recovery of the spin localization of the zigzag edge. Such a distortion of planar GNR structures offers a degree of freedom to control the magnetism on metal substrates. 相似文献
719.
Jiping Hao Akihide Nishiyama Dr. Shigeki Mori Prof. Dr. Ko Furukawa Prof. Dr. Soji Shimizu 《Angewandte Chemie (International ed. in English)》2023,62(34):e202307862
5,15-Dioxaporphyrin ( DOP ) is a novel meso-oxaporphyrin analogue and exhibits unique 20π-antiaromaticity, unlike its mother congener of 18π-aromatic 5-oxaporphyrin, commonly known as its cationic iron complex called verdohem, which is a key intermediate of heme catabolism. To reveal its reactivities and properties as an oxaporphyrin analogue, the oxidation of tetra-β-arylated DOP ( DOP-Ar4 ) was explored in this study. Stepwise oxidation from the 20π-electron neutral state was achieved, and the corresponding 19π-electron radical cation and 18π-electron dication were characterized. Further oxidation of the 18π-aromatic dication resulted in the formation of a ring-opened dipyrrindione product by hydrolysis. Considering a similar reaction of verdoheme to ring-opened biliverdin in the heme degradation in nature, the current result consolidates the ring-opening reactivity of oxaporphyrinium cation species. 相似文献
720.
Long-Tao Huang Yuta Kitakawa Kodai Yamada Futa Kamiyama Dr. Masahiro Kojima Dr. Tatsuhiko Yoshino Prof. Dr. Shigeki Matsunaga 《Angewandte Chemie (International ed. in English)》2023,62(29):e202305480
Sulfondiimines are diaza-analogues of sulfones with a chiral sulfur center. Compared to sulfones and sulfoximines, their synthesis and transformations have so far been studied to a lesser extent. Here, we report the enantioselective synthesis of 1,2-benzothiazine 1-imines, i.e., cyclic sulfondiimine derivatives from sulfondiimines and sulfoxonium ylides via C−H alkylation/cyclization reactions. The combination of [Ru(p-cymene)Cl2]2 and a newly developed chiral spiro carboxylic acid is key to achieving high enantioselectivity. 相似文献