全文获取类型
收费全文 | 212篇 |
免费 | 15篇 |
专业分类
化学 | 160篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 10篇 |
物理学 | 55篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 18篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 13篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有227条查询结果,搜索用时 31 毫秒
71.
Daisuke Nagai Kensuke Yokota Takuma Ogawa Bungo Ochiai Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2008,46(2):733-739
Cationic ring‐opening copolymerization behavior of trioxane (TOX) and a seven‐membered cyclic carbonate, 1,3‐dioxepan‐2‐one (7CC) is described. When TOX and 7CC were cationically copolymerized under various feed ratios using trifluoromethane sulfonic acid (TfOH) as an initiator in nitrobenzene at 30 °C, 7CC was consumed faster than TOX and the decarboxylation was accompanied to afford the corresponding polyacetal–polycarbonate type copolymers containing poly(oxytetramethylene) units. The copolymer composition could be controlled by the feed ratio of 7CC, whose increase resulted in the high copolymer composition of the 7CC unit. The solubility of the copolymers increased as the increase of the 7CC content. Thermogravimetric, size‐exclusion chromatographic, and X‐ray analyses of the copolymers suggest that the sequences of the copolymer chains consist of the segments containing the units originated from 7CC and those with TOX unit‐rich compositions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 733–739, 2008 相似文献
72.
The lineshape of the ν1 Raman band of methane is measured as a function of pressure between 1 and 50 atm by inverse Raman spectroscopy using the 488 nm output of a cw Ar+ laser as a probe beam and the output of a pulsed dye laser as a Stokes pump beam. The linewidth is found to increase linearly in this pressure region, and the fwhm Δν (in cm?1) can be expressed as Δν = 0.32 + 0.012p, p being the methane pressure in atm. 相似文献
73.
Nishiwaki N Ogihara T Takami T Tamura M Ariga M 《The Journal of organic chemistry》2004,69(24):8382-8386
beta-Nitroenamines having a formyl group at the beta-position behave as the synthetic equivalent of unstable nitromalonaldehyde, which is a useful synthon for syntheses of versatile nitro compounds. High solubility of the nitroenamines into general organic solvents enables us to conduct reactions in the organic media accompanied by easy experimental manipulations and considerable safety. When nitroenamines are treated with 1,2-bifunctional nucleophiles such as hydrazines, hydroxylamine and glycine ester, nitrated pyrazoles, isoxazole and pyrrole-2-carboxylate were readily prepared. This methodology was also applicable to guanidines and 1,2-diamines, leading to pyrimidines and 1,4-diazepines, respectively. 相似文献
74.
Takakazu Yamamoto Takuma Yasuda Yoshimasa Sakai Shinji Aramaki 《Macromolecular rapid communications》2005,26(15):1214-1217
Summary: A π‐conjugated charge transfer‐type copolymer consisting of an electron‐donating thiophene and an electron‐accepting 1,3,4‐thiadiazole, P(ThdzTh), underwent facile electrochemical p‐ and n‐doping, as revealed by cyclic voltammetry. The copolymer gave a new ambipolar field‐effect transistor (FET), which showed typical IDS (source–drain current)–VDS (source–drain voltage) curves in both a p‐type working mode and an n‐type working mode. In the n‐type working mode, the polymer showed a carrier mobility of about 5 × 10−3 cm2 · V−1 · s−1 and an on/off ratio of about 3 × 104.
75.
76.
Daitaro Ishikawa Kodai Murayama Kimie Awa Takuma Genkawa Makoto Komiyama Sergei G. Kazarian Yukihiro Ozaki 《Analytical and bioanalytical chemistry》2013,405(29):9401-9409
We have recently developed a novel portable NIR imaging device (D-NIRs), which has a high speed and high wavelength resolution. This NIR imaging approach has been developed by utilizing D-NIRs for studying the dissolution of a model tablet containing 20 % ascorbic acid (AsA) as an active pharmaceutical ingredient and 80 % hydroxypropyl methylcellulose, where the tablet is sealed by a special cell. Diffuse reflectance NIR spectra in the 1,000 to 1,600 nm region were measured during the dissolution of the tablet. A unique band at around 1,361 nm of AsA was identified by the second derivative spectra of tablet and used for AsA distribution NIR imaging. Two-dimensional change of AsA concentration of the tablet due to water penetration is clearly shown by using the band-based image at 1,361 nm in NIR spectra obtained with high speed. Moreover, it is significantly enhanced by using the intensity ratio of two bands at 1,361 and 1,354 nm corresponding to AsA and water absorption, respectively, showing the dissolution process. The imaging results suggest that the amount of AsA in the imaged area decreases with increasing water penetration. The proposed NIR imaging approach using the intensity of a specific band or the ratio of two bands combined with the developed portable NIR imaging instrument, is a potentially useful practical way to evaluate the tablet at every moment during dissolution and to monitor the concentration distribution of each drug component in the tablet. Figure
Visible photo and NIR image for tablet dissolution obtained by using a newly developed portable NIR imaging device: D-NIRs 相似文献
77.
Anomalous diffusion in lipid bilayers is usually attributed to viscoelastic behavior. We compute the scaling exponent of relative fluctuations of the time-averaged mean square displacement in a lipid bilayer, by using a molecular dynamics simulation. According to the continuous time random walk theory, this exponent indicates non-Gaussian behavior caused by a power-law trapping time. Our results provide the first evidence that a lipid bilayer has not only viscoelastic properties but also trapping times distributed according to a power law. 相似文献
78.
A Palladium‐Nanoparticle and Silicon‐Nanowire‐Array Hybrid: A Platform for Catalytic Heterogeneous Reactions 下载免费PDF全文
Dr. Yoichi M. A. Yamada Yoshinari Yuyama Dr. Takuma Sato Dr. Shigenori Fujikawa Dr. Yasuhiro Uozumi 《Angewandte Chemie (International ed. in English)》2014,53(1):127-131
We report the development of a silicon nanowire array‐stabilized palladium nanoparticle catalyst, SiNA‐Pd. Its use in the palladium‐catalyzed Mizoroki‐Heck reaction, the hydrogenation of an alkene, the hydrogenolysis of nitrobenzene, the hydrosilylation of an α,β‐unsaturated ketone, and the C‐H bond functionalization reactions of thiophenes and indoles achieved a quantitative production with high reusability. The catalytic activity reached several hundred‐mol ppb of palladium, reaching a TON of 2 000 000. 相似文献
79.
Koseki T Onishi H Takahashi Y Uchida M Machida Y 《Chemical & pharmaceutical bulletin》2008,56(10):1384-1388
It was attempted to produce novel furosemide (FS) fast-disintegrating tablets by direct compression. The combination of FS, microcrystalline cellulose, croscarmellose sodium and xylitol was used as the basic formulation, and sucrose stearic acid ester (SSE) was chosen as an additional additive. The tablets with SSE were prepared by the simple addition of SSE, using a lyophilized mixture of FS and SSE or using a FS/SSE mixture obtained by evaporation of their ethanol solution. Only the tablets, produced using the FS/SSE mixture obtained by organic solvent (ethanol) evaporation, showed hardness of more than 30 N and a disintegration time of less than 20 s, which were the properties suitable for fast-disintegrating tablets. These properties were considered to result from well-mixed and fine-powdered SSE and FS. 相似文献
80.
Takashi Otani Takuma Sasayama Masashi Horiuchi Shunnosuke Okauchi Hidetoshi Kawai Maho Kitahara Yoshitane Imai Takanori Shibata 《Helvetica chimica acta》2021,104(4):e2100016
We achieved a two-type synthesis of quinoxaline-fused polyaza[5]- and [7]helicenes through consecutive N−H/C−H coupling with a hypervalent iodine reagent as a key reaction. By fusing electron-deficient quinoxaline, these polyazahelicenes constitute an efficient donor-acceptor type of molecule with absorption edges that reach up to approximately 650 nm. Evaluating the chiroptical properties reveals that the polyazahelicene exhibits a rare orange circularly polarized glow with a luminescence dissymmetry factor (glum value) of 0.003. 相似文献