全文获取类型
收费全文 | 225篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 198篇 |
数学 | 13篇 |
物理学 | 17篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 15篇 |
2007年 | 10篇 |
2006年 | 18篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有228条查询结果,搜索用时 0 毫秒
81.
A one-carbon ring enlarged cyclopropanation or vinylation reaction of cyclic keto eaters or sulfones
On treating potassium salts of n-membered cyclic keto esters or sulfones with phenyl 1-propenyl selenone, a one-carbon ring expansion reaction involving cyclopropanation or vinylation takes place to give the corresponding bicyclo[(n - 1).1.0]alkanones or (n + 1)-membered cyclic ketones bearing vinyl group at their 3-position. 相似文献
82.
Makoto MurataTakayoshi Hara Kohsuke MoriMasahiko Ooe Tomoo MizugakiKohki Ebitani Kiyotomi Kaneda 《Tetrahedron letters》2003,44(27):4981-4984
Hydroxyapatite-bound Pd catalyst was found to be highly effective for the deprotection of N-benzyloxycarbonyl group from amino acids in the presence of molecular hydrogen. The catalyst was also applicable to the hydrogenolysis of a sterically encumbered core-Z-protected poly(amido amine) dendrimer, affording the dendritic amino compound in 99% yield. 相似文献
83.
Yamamoto A Tomoo K Miyagawa H Takaoka Y Sumiya S Kitamura K Ishida T 《Chemical & pharmaceutical bulletin》2000,48(4):480-485
To promote our better understanding of the dynamic stability of the bovine cathepsin B structure, which is characterized by an extra disulfide bond at Cys148-Cys252 from the other species, and of the binding stability of CA074 (a cathepsin B-specific inhibitor), molecular dynamics (MD) simulations were performed for the enzyme and its CA074 complex, assuming a system in aqueous solution at 300 K. The MD simulation covering 400 ps indicated that the existence of a Cys148-Cys252 disulfide bond increases the conformational flexibility of the occluding loop, although the conformational stability of the overall structure is little affected. The structural characteristics of the complex elucidated by X-ray analysis were suggested to be also intrinsic and stable in the dynamic state; the hydrogen bonding/electrostatic interactions between the main and side chains of CA074 and the Sn and Sn' subsites of the enzyme were maintained throughout the MD simulation. Furthermore, the simulation made clear that the binding of CA074 significantly restricted the conformational flexibility of the substrate binding region, especially the occluding loop, of cathepsin B. Statistical analyses during the simulation suggest that the selectivity of CA074 for cathepsin B stems from the tight P1'-S1' and P2'-S2' interactions, assisted in particular by double hydrogen bonds between the carboxyl two oxygens of the CA074 C-terminus and the imidazole NH groups of His110 and His111 residues. 相似文献
84.
Kiyokazu Imai Tomoo Shiomi Yasuyuki Tezuka Toshiaki Kawanishi Tomofumi Jin 《Journal of polymer science. Part A, Polymer chemistry》1988,26(7):1961-1968
Bulk and/or solution polymerizations of a series of vinyl esters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, and vinyl benzoate were conducted. Iodine-coloration, 1,2-glycol structure, molecular weight, and tacticity (triad and pentad) were measured for the resulting poly(vinyl alcohol)s (PVAs). The iodine-coloration abilities of PVAs, derived from poly(vinyl ester)s that were obtained through bulk polymerization at 60°C, depended on the starting monomer, increasing in the following order: vinyl benzoate < vinyl acetate < vinyl propionate < vinyl butyrate < vinyl pivalate. In solution polymerizations of vinyl propionate and vinyl butyrate, it was revealed that the tacticity of the derived PVAs apparently depended on the type and amount of polymerization solvent employed, as found previously in the case for vinyl acetate. The iodine-coloration of these PVA samples varied in the same order as their syndiotactic content, while no relationship was observed toward their 1,2-glycol content. The probabilities of the syndiotactic propagation at 60°C were estimated as 0.49 (benzoate), 0.54 (acetate), 0.55 (propionate), 0.56 (butyrate), and 0.60 (pivalate), respectively. 相似文献
85.
The first synthesis of a stereoisomeric mixture of hormone α1, the mating hormone of Phytophthora, was achieved, and the synthetic mixture was confirmed to be hormonally active. 相似文献
86.
Jeffrey W BodeYoshifumi Hachisu Tomoo MatsuuraKeisuke Suzuki 《Tetrahedron letters》2003,44(17):3555-3558
Base-promoted cyclocondensation of hindered nitrile oxides and cyclic diketones affords highly functionalized, sterically-encumbered isoxazole products in good yield. The mild reaction conditions (NEt3, EtOH) are tolerant to a wide variety of functionality and permit the preparation of precursors to complex polycycles typically inaccessible via direct, intermolecular carboncarbon bond forming reactions. The ability to effect the cyclocondensation reaction with a catalytic amount of amine points to the intermediacy of an ammonium enolate as a key reactive species. A convenient, single step preparation of crystalline, stable nitrile oxides from the corresponding oximes enhances the advantages of this methodology for the preparation of functionalized polycycles. 相似文献
87.
Summary Less than 1 milligram of suspended particulate matter in a 50-ml water sample was separated by centrifugation, decomposed with 22l of 21010 perchloric-nitric-hydrofluoric acid mixture, and analyzed for copper, lead, cadmium and zinc by microscale differential pulse anodic stripping voltammetry with a hanging mercury drop electrode in 300l of 0.06M perchloric acid. The procedure was simple and rapid, because a single Teflon microvessel was used throughout the whole procedure.
Bestimmung von Schwermetallspuren in suspendierten Teilchen in Teichwasser durch Anodic Stripping Voltammetry im Mikromaßstab
Zusammenfassung Weniger als 1 mg suspendierter Teilchenmaterie wurde durch Zentrifugieren abgetrennt, mit 22l eines Gemisches HClO4HNO3HF (21010) zersetzt und darin Cu, Pb, Cd und Zn durchDifferential-Pulse-Anodic-Stripping-Voltammetrymit hängender Hg-Tropfelektrode in 300 l 0.06M Perchlorsäure bestimmt. Das Verfahren ist einfach und schnell, es bedarf dazu nur eines Mikrokölbchens aus Teflon.相似文献
88.
89.
Kimiak Yamamura Kazumi Nakatsu Kenji Nakao Tomoo Nakazawa Ichiro Murata 《Tetrahedron letters》1979,20(52):4999-5002
A series of o-tropyliobiphenyl tetradfluoroborates has been synthesized. Evidences are presented to show that exhibit strong intramolecular charge-transfer interaction between tropylium ion and remote aryl ring. The structure of was determined by single crystal X-ray diffraction study. 相似文献
90.
Zen Maeno Kaoru Midogochi Takato Mitsudome Tomoo Mizugaki Koichiro Jitsukawa 《Tetrahedron letters》2018,59(9):832-835
A convenient and sustainable method for the synthesis of glycol diesters was developed through the depolymerization of polyethylene glycols (PEGs) with carboxylic acids using proton-exchanged montmorillonite as an efficient solid acid catalyst. Several functionalized glycol diesters were obtained in good yields from PEGs and readily available carboxylic acids. Upon reaction completion, the catalyst could be easily separated by filtration and reused with its activity remaining unchanged. 相似文献