全文获取类型
收费全文 | 1404篇 |
免费 | 64篇 |
国内免费 | 3篇 |
专业分类
化学 | 1111篇 |
晶体学 | 10篇 |
力学 | 39篇 |
数学 | 97篇 |
物理学 | 214篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 24篇 |
2021年 | 37篇 |
2020年 | 27篇 |
2019年 | 38篇 |
2018年 | 20篇 |
2017年 | 22篇 |
2016年 | 46篇 |
2015年 | 42篇 |
2014年 | 73篇 |
2013年 | 93篇 |
2012年 | 144篇 |
2011年 | 158篇 |
2010年 | 82篇 |
2009年 | 65篇 |
2008年 | 100篇 |
2007年 | 82篇 |
2006年 | 78篇 |
2005年 | 72篇 |
2004年 | 55篇 |
2003年 | 49篇 |
2002年 | 55篇 |
2001年 | 13篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1471条查询结果,搜索用时 15 毫秒
1.
Young Joo Kim Pil Ho Huh Byung Kyu Kim 《Journal of Polymer Science.Polymer Physics》2015,53(7):468-474
Supramolecular polyurethane ureas are expected to have superior mechanical properties primarily due to the reversible, noncovalent interactions such as hydrogen bonding interactions. We synthesized polyurethane prepolymers from small molecular weight of poly(tetramethylene ether)glycol and isophorone diisocyanates, which were end capped with propylamine to synthesize polyurethane ureas with high contents of urea and urethane groups for hydrogen‐bonding formations to facilitate self‐healing. The effects of polyurethane urea molecular weight (3000 ≤ Mn ≤ 9000), crosslinking, and cutting direction were studied in terms of thermal, mechanical, and morphological properties with an emphasis on the self‐healing efficiency. It was found that the thermal self‐healability was more pronounced as the molecular weight of polyurethane urea decreased, showing a maximum of more than 96% with 3000 Mn when the sample was cut along the stretch direction. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 468–474 相似文献
2.
Aiqing Zhang Xiangdan Li Changwoon Nah Keejun Hwang Myong‐Hoon Lee 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):22-29
A soluble aromatic polyimide was chloromethylated via a reaction with chloromethyl methyl ether in the presence of tin(IV) chloride to produce a new starting material for the modification of aromatic polyimides. The chemical structure of the resulting polymer was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The maximum number of chloromethyl groups per repeat unit was 1.81. The chloromethylated polyimide was stable up to 250 °C and soluble in both chloroform and tetrahydrofuran. So that its utilization for further modification could be demonstrated, cinnamic acid was reacted with the formed polyimide, and it produced a new photosensitive polyimide with a cinnamoyl side chain. The photosensitivity of the resulting polyimide was investigated with ultraviolet spectroscopic methods. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 22–29, 2003 相似文献
3.
Sang Kyu Lee Min Ju Cho Jung‐Il Jin Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):531-542
New photocrosslinkable maleimide copolymers have been synthesized by the attachment of a tricyanopyrrolidene‐based chromophore. The 2‐(3‐cyano‐4‐(2‐{4‐[hexyl‐(6‐hydroxy‐hexyl)‐amino]‐phenyl}‐vinyl)‐5‐oxo‐1‐{4‐[4‐(3‐oxo‐3‐phenyl‐propenyl)‐ phenoxy]‐butyl}‐1,5‐dihydro‐pyrrol‐2‐ylidene)‐malononitrile chromophore exhibits nonlinear optical activity and contains a chalcone moiety that is sensitive to UV light (λ = 330–360 nm) for crosslink formation. The maleimide monomers have also been functionalized with chalcone moieties. The resultant copolymers exhibit great processability, and one of them shows a maximum electrooptic coefficient of 90 pm/V at 1300 nm. We could control the thermal stability of the electrooptic coefficient with the newly synthesized photoreactive copolymers successfully. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 531–542, 2007 相似文献
4.
Ju Yeon Woo Eun Hee Kim Tae Hoon Yoon Jae Chang Kim Byung Kyu Kim 《Liquid crystals》2007,34(9):1115-1120
Chiral dopants were added to the formulation of holographic polymer-dispersed liquid crystals and the effects studied in terms of grating formation dynamics, morphology, diffraction efficiency, contrast ratio and electro-optical properties of the films. A gradual increase of real-time diffraction efficiency, decrease of droplet size and increase of diffraction efficiency of the composite film were obtained with the addition and increasing content of chiral dopant, due to the increased viscosity of the liquid crystal (LC) doped with the chiral dopant leading to decreased droplet coalescence. The contrast ratio decreased with increasing content of chiral dopant due to the difficult orientation of LC molecules caused by the formation of a helical structure. Addition of a small amount of the chiral dopant increased the driving voltage slightly, whereas the decay time is decreased significantly as a result of the high twisting of the helical structure. 相似文献
5.
ω-Tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides are prepared as Grignard reagents containing protected mercaptoalkyl chains, which are useful for the direct introduction of ω-mercaptoalkyl chains to electrophiles. In order to prove the usefulness of these reagents, they were reacted with buckminsterfullerene (C60) to give 1-(ω-mercaptoalkyl)-1,2-dihydrobuck minsterfullerenes after the deprotection of THP group with TFA. 相似文献
6.
CHIP-mediated hyperubiquitylation of tau promotes its self-assembly into the insoluble tau filaments
Ji Hyeon Kim Jeeyoung Lee Won Hoon Choi Seoyoung Park Seo Hyeong Park Jung Hoon Lee Sang Min Lim Ji Young Mun Hyun-Soo Cho Dohyun Han Young Ho Suh Min Jae Lee 《Chemical science》2021,12(15):5599
The tau protein is a highly soluble and natively unfolded protein. Under pathological conditions, tau undergoes multiple post-translational modifications (PTMs) and conformational changes to form insoluble filaments, which are the proteinaceous signatures of tauopathies. To dissect the crosstalk among tau PTMs during the aggregation process, we phosphorylated and ubiquitylated recombinant tau in vitro using GSK3β and CHIP, respectively. The resulting phospho–ub-tau contained conventional polyubiquitin chains with lysine 48 linkages, sufficient for proteasomal degradation, whereas unphosphorylated ub-tau species retained only one–three ubiquitin moieties. Mass-spectrometric analysis of in vitro reconstituted phospho–ub-tau revealed seven additional ubiquitylation sites, some of which are known to stabilize tau protofilament stacking in the human brain with tauopathy. When the ubiquitylation reaction was prolonged, phospho–ub-tau transformed into insoluble hyperubiquitylated tau species featuring fibrillar morphology and in vitro seeding activity. We developed a small-molecule inhibitor of CHIP through biophysical screening; this effectively suppressed tau ubiquitylation in vitro and delayed its aggregation in cultured cells including primary cultured neurons. Our biochemical findings point to a “multiple-hit model,” where sequential events of tau phosphorylation and hyperubiquitylation function as a key driver of the fibrillization process, thus indicating that targeting tau ubiquitylation may be an effective strategy to alleviate the course of tauopathies.Multiple-hit model for tau aggregation, where sequential events of tau phosphorylation and hyperubiquitylation function as a key driver of the fibrillization process. 相似文献
7.
Poly(dimethylsiloxane) microchip for precolumn reaction and micellar electrokinetic chromatography of biogenic amines 总被引:2,自引:0,他引:2
We have demonstrated that precolumn derivatization and capillary electrophoresis separation on a poly(dimethylsiloxane) (PDMS) microchip can be realized as efficient as those on glass microchips. In an optimized condition of micellar electrokinetic chromatography (MEKC), using 25 mM sodium borate buffer (pH 10.0) with 25 mM sodium dodecyl sulfate (SDS) and 5% v/v methanol, the electroosmotic flow in an oxidized PDMS microchip is stabilized within 3% for days. By employing a fluorometric derivatization with o-phthaldialdehyde (OPA) in an optimally designed reaction chamber, four most important biogenic amines occurring in foods, histamine, tyramine, putrescine, and tryptamine, are quantitatively determined in less than 1 min at the levels applicable to real samples. The migration behaviors of anionic OPA-derivatized biogenic amines under the MEKC conditions are analyzed, and it has been found that under our separation conditions, the electrophoretic mobility of the SDS micelles is significantly greater than those of the anions in the aqueous phase. The channel manifold in a PDMS substrate is fabricated using replica molding against a thick photoresist, SU-8, pattern generated by photolithography. The plate with the microchannel pattern is strongly, irreversibly bonded to another PDMS plate by using a new bonding technique, which employs surface oxidation by corona discharge generated from a cheap, handy source, Tesla coil. 相似文献
8.
Dal Ho Huh 《Tetrahedron》2004,60(44):9857-9862
Various 2-arylmethylimidazolines were prepared by treating readily available 2-aryl-1,1-dibromoethenes with ethylenediamine under mild conditions and further converted into the corresponding imidazoles smoothly with Swern oxidation. 相似文献
9.
A fluorimetric flow-injection procedure with a single reagent solution containing p-hydroxyphenylacetic acid, peroxidase and ammonia permits the determination of aqueous hydrogen peroxide in the range 10?8?10?4 M; 30–60 samples can be processed per hour. The method exhibits a wide linear range and is insensitive to sample pH within the range 2–6. 相似文献
10.
We synthesized the new photosensitive oligomer containing a chalcone moiety in the main chain by end-capping reaction of diepoxide compound with methacrylic acid. The chalcone-epoxy oligomeric compound was synthesized with 4,4′-dihydroxychalcone and epichlorohydrin. Investigation of the photosensitivity of the newly synthesized chalcone oligomer was carried out by using UV-Vis absorption and infrared spectroscopies under UV exposure. We observed the photodimerization behavior under UV irradiation. At the same time, we could also observe the photopolymerization of the compound with a trace amount of dimethoxyphenyl acetophenone. Thermal properties of UV-cured dimethacrylate compounds were also studied. 相似文献