全文获取类型
收费全文 | 1076篇 |
免费 | 36篇 |
专业分类
化学 | 842篇 |
晶体学 | 7篇 |
力学 | 20篇 |
数学 | 25篇 |
物理学 | 218篇 |
出版年
2022年 | 5篇 |
2021年 | 17篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 34篇 |
2015年 | 33篇 |
2014年 | 19篇 |
2013年 | 51篇 |
2012年 | 60篇 |
2011年 | 72篇 |
2010年 | 33篇 |
2009年 | 37篇 |
2008年 | 63篇 |
2007年 | 46篇 |
2006年 | 49篇 |
2005年 | 49篇 |
2004年 | 52篇 |
2003年 | 47篇 |
2002年 | 39篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1968年 | 5篇 |
排序方式: 共有1112条查询结果,搜索用时 15 毫秒
31.
Fumio Sanda Masakatsu Hitomi Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2001,39(18):3159-3167
The synthesis and cationic polymerization of the following bicyclo orthoesters were examined: 4‐ethyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 1,4‐diethyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 4‐ethyl‐1‐phenyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 4‐ethyl‐1‐(4‐methoxyphenyl)‐2,6,7‐trioxabicyclo[2.2.2]octane, and 4‐ethyl‐1‐(4‐nitrophenyl)‐2,6,7‐ trioxabicyclo[2.2.2]octane. All the monomers underwent equilibrium polymerization, which was confirmed by the relationships between the polymerization temperature and monomer conversion. The obtained polymers afforded the original monomers via an acid‐catalyst treatment with a low reagent concentration in CH2Cl2 at 20 °C. The equilibrium monomer concentration was constant, regardless of the initial reagent concentration, in both polymerization and depolymerization. The bicyclo orthoesters with a bulky and electron‐withdrawing substituent showed a larger equilibrium monomer concentration. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3159–3167, 2001 相似文献
32.
33.
Summary 2-(2-Pyridyl)-1, 3-propanediol was converted into the diacetate, which was then condensed with phthalimide. The product was hydrolyzed with hydrochloric acid to give 2-(2-pyridyl)-1, 3-diaminopropane. The free amine gave 12 complexes with copper(II), nickel(II), and cobalt(III), which were characterized spectroscopically and magnetically. Features of the amine as a ligand are discussed. A few related complexes were also studied. 相似文献
34.
H. Hanabata T. Matsuo H. Suga 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):325-333
Heat capacities of crystalline-cyclodextrin undecahydrate have been measured in the temperature range between 13 and 300K by use of a miniaturized adiabatic low-temperature calorimeter. A first-order phase transition occurred at 226K with a discontinuous entropy change of 45.0 ± 1.0J
K
–1 mol–1. The highly disordered nature of the high temperature phase was considered in relation to the entropy contribution. A glass transition phenomenon observed around 150K was ascribed to the freezing of a configurational change of the protons engaged in the four-membered hydrogen-bonded ring which appeared only in the low temperature phase. 相似文献
35.
Dr. Motoki Toganoh Hideaki Matsuo Ayumi Sato Prof. Hiroyuki Furuta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8316-8322
Ruthenocene‐type hybrid complexes with N‐fused porphyrinato ligands, [Ru(NFp)Cp] (NFp=N‐fused porphyrin, Cp=cyclopentadienyl), have been prepared and characterized by NMR and UV/Vis/NIR spectroscopy, cyclovoltammetry, and X‐ray crystallography. [Ru(NFp)Cp] is a common low‐spin ruthenium(II) complex and shows strong aromaticity. The Ru–Cp distance (1.833 Å) in [Ru(NFp)Cp] is comparable to that in [RuCp2] (1.840 Å). DFT calculations on [Ru(NFp)Cp] showed the unequivocal contribution of the RuCp moiety as well as the NFp moiety to both the HOMO and LUMO, constructing a three‐dimensional d–π conjugated system. The HOMO–LUMO gaps of [Ru(NFp)Cp] are insensitive to the substituents on the NFp ligand, which is illustrated spectroscopically as well as theoretically. This is in sharp contrast to the ligand precursor, the N‐fused porphyrin, in which the HOMO–LUMO gap is affected by substituents in a similar manner to standard porphyrins and related macrocycles. 相似文献
36.
Yamamoto Y Terui N Tachiiri N Minakawa K Matsuo H Kameda T Hasegawa J Sambongi Y Uchiyama S Kobayashi Y Igarashi Y 《Journal of the American Chemical Society》2002,124(39):11574-11575
Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability. 相似文献
37.
Moriya K. Yamada T. Sakai K. Yano S. Baluja S. Matsuo T. Pritz I. Vysochanskii Y. M. 《Journal of Thermal Analysis and Calorimetry》2002,70(2):321-328
Heat capacities of the Pb2xSn2(1-x)P2Se6 crystals (x=0, 0.098, 0.251, 0.402 and 1.0) were measured using an adiabatic calorimeter at temperatures between 10 and 350 K. In the
crystal of x=0, two heat capacity anomalies corresponding to the ferroelectric commensurate - intermediate incommensurate(C-IC) phase
transition temperature T
i, and the incommensurate - paraelectric (IC-N) phase transition temperature T
c, were observed at 193.24±0.10 and 220.07±0.15 K, respectively. The phase transition temperatures decreased with an increase
in Pb2+ concentration. The anomaly at Ti disappeared at x=0.251 in the mixed systems of the Pb2xSn2(1-x)P2Se6. In the crystal of Pb2P2Se6 (x=1.0), no phase transition was observed. The normal heat capacities for the mixed crystals were determined by least squares
fitting of the Debye and Einstein functions to the experimental data. The anomalous heat capacities gave the phase transition
entropies of 8.5 and 1.5 J mol-1 K-1 for x=0. The large transition entropies are consistent with an order-disorder mechanism in the ferroelectric-paraelectric phase
transitions in x=0.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
38.
Hitomi Uno Toshikazu Takata Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1675-1685
Graft copolymerization of a bicycloorthoester (BOE) with polymer-supported sulfonium salts was studied. Several polymer-supported sulfonium salts were prepared by the homopolymerizations of p-vinylbenzyl tetramethylenesulfonium hexafluoroantimonate ( 2 ) and 4-(p-vinylphenyl)butyl tetramethylenesulfonium hexafluoroantimonate ( 3 ), and by the copolymerizations of 2 with some vinyl monomers (n-butyl vinyl ether, styrene, acrylonitrile, and p-styrenesulfonic acid potassium salt). These sulfonium salts could initiate the polymerization of BOE to give grafted polymers. Temperature dependences of the catalytic activity of them were not so dramatic as that of benzyl tetramethylenesulfonium hexafluoroantimonate ( 1 ), but the activities of them were higher than that of 1 at temperatures lower than 80°C. The conversion of BOE in the polymerizations with these polymer initiators was ca. 30–70% at 120°C for 7 h. An effect of the comonomer structure on the catalytic activity was observed and styrene was the best comonomer for 2 in terms of the reactivity of the copolymer. The spacer-modified sulfonium salt (homopolymer of 3 ) was slightly lower than polymer-supported benzyl type sulfonium salt (homopolymer of 2 ) in the catalytic activity. 相似文献
39.
Juri Takayoshi Yong-Lin Huang Yosuke Matsuo Yoshinori Saito Dian-Peng Li Takashi Tanaka 《Molecules (Basel, Switzerland)》2021,26(14)
Ellagitannins (ETs) are plant polyphenols with various health benefits. Recent studies have indicated that the biological activities of ETs are attributable to their degradation products, including ellagic acid and its gut microflora metabolites, such as urolithins. Insect tea produced in the Guangxi region, China, is made from the frass of moth larvae that feed on the ET-rich leaves of Platycarya strobilacea. Chromatographic separation of the Guangxi insect tea showed that the major phenolic constituents are ellagic acid, brevifolin carboxylic acid, gallic acid, brevifolin, and polymeric polyphenols. Chemical investigation of the feed of the larvae, the fresh leaves of P. strobilacea, showed that the major polyphenols are ETs including pedunculagin, casuarictin, strictinin, and a new ET named platycaryanin E. The new ET was confirmed as a dimer of strictinin having a tergalloyl group. The insect tea and the leaves of P. strobilacea contained polymeric polyphenols, both of which were shown to be composed of ETs and proanthocyanidins by acid hydrolysis and thiol degradation. This study clarified that Guangxi insect tea contains ET metabolites produced in the digestive tract of moth larvae, and the metabolites probably have higher bioavailabilities than the original large-molecular ETs of the leaves of P. strobilacea. 相似文献
40.
Cross-linking of ultra-high molecular weight polyethylene was performed with electron-beam irradiation in the range of radiation dose from 12 to 96 Mrad under nitrogen. Dry gel films and melt films were used as specimens. Two kinds of cross-linked specimens could be kept at 200°C for a prolonged time in an undeformed state and this tendency was independent of radiation dose. The elongation of the gel films hampered the heat-resistant effect and the drawn specimens were broken at temperatures lower than 175 °C. The elongation of the melt films could not be realized, because of a marked fixation of chains in the fiber network, even at a dose of 12 Mrad. 相似文献