全文获取类型
收费全文 | 323篇 |
免费 | 13篇 |
专业分类
化学 | 242篇 |
晶体学 | 7篇 |
力学 | 9篇 |
数学 | 15篇 |
物理学 | 63篇 |
出版年
2024年 | 1篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 19篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 28篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有336条查询结果,搜索用时 31 毫秒
261.
A computational model is proposed for simulating the flow of polymer nanocomposites. This model is based on a multiphase suspension
of disc-like particles and polymers. The particles are represented by oblate spheroid particles that interact with each other
via the Gay-Berne (GB) potential, and the polymers are modeled by finitely extensible nonlinear elastic (FENE) chains that
interact with each other via the repulsive Lennard-Jones potential. The interaction between an oblate spheroid particle and
a FENE chain is also considered using a modified GB potential. A Brownian dynamics simulation of the shear flows of this system
was conducted to investigate the orientation behavior of disc-like particles and the rheological properties of this system.
The orientation of disc-like particles was affected by polymers, and the particles in a suspension were well aligned in flows
because of the flow orientation property of polymers. The predicted shear viscosity exhibited shear thinning, and the normal
stress differences agree qualitatively with experimental measurements of polymer/clay nanocomposites. The simulation results
suggest that the present model has the potential to be used as a computational model for polymer nanocomposites. 相似文献
262.
Reiko Ando Yoshinori Makino Tomohide Tamura Noboru Yamamoto Rena Nishigaki Takehiro Kimura Nobuaki Yokote Hiroshi Yamamoto 《Biomedical chromatography : BMC》2010,24(3):301-306
A simple and sensitive high‐performance liquid chromatographic (HPLC) method was developed for determination of amrubicin and its metabolite amrubicinol in human plasma. After protein precipitation with methanol without evaporation procedure, large volume samples were injected and separated by two monolithic columns with a guard column. The mobile phase consisted of tetrahydrofuran–dioxane–water (containing 2.3 mM acetic acid and 4 mM sodium 1‐octanesulfonate; 2:6:15, v/v/v). Wavelengths of fluorescence detection were set at 480 nm for excitation and 550 nm for detection. Under these conditions, linearity was confirmed in the 2.5–5000 ng/mL concentration range of both compounds. The intra‐ and inter‐day precision and intra‐ and inter‐day accuracy for both compounds were less than 10%. The method was successfully applied to a clinical pharmacokinetic study of amrubicin and amrubicinol in cancer patients. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
263.
Takehiro Watanabe Keisuke Nakanishi Tomoyuki Ozawa Hideya Kawasaki Koichi Ute Ryuichi Arakawa 《Rapid communications in mass spectrometry : RCM》2010,24(13):1835-1841
We have designed a semi‐online liquid chromatography/matrix‐assisted laser desorption/ionization mass spectrometry (LC/MALDI‐MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI‐MS analysis. Our novel semi‐online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,‐hexafluoroisopropyl alcohol (HFIP), to be used to achieve cost‐effective analysis. Using the semi‐online LC/MALDI‐MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size‐exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed‐phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI‐MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size‐exclusion separation; the reversed‐phase separation by interaction with the ODS functions may have less influence on column separation. The semi‐online monolithic capillary LC/MALDI‐MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
264.
265.
Takehiro Watanabe Masanori Okabayashi Daisuke Kurokawa Yukari Nishimoto Tomoyuki Ozawa Hideya Kawasaki Ryuichi Arakawa 《Journal of mass spectrometry : JMS》2010,45(7):799-805
Ultrasonic degradation of poly(ethylene oxide‐block‐propylene oxide) copolymers consisting of a hydrophilic and a hydrophobic portion was studied with the aim to determine the location of bonds involved in the initial scission of the copolymers. LC–APCI‐IT‐MS and LC–APCI‐orbitrap‐MS were used for the detailed structural analysis of degradation products. The results indicated that initial bond scissions occurred principally at the boundary regions between backbones of polyethylene oxide (PEO) and polypropylene oxide (PPO) chains. Further structural analysis revealed the presence of oxygen adducts in the degradation products. Comparison with a thermal degradation carried out in helium atmosphere, one can conclude that the oxygen adducts are formed by radical reaction with water or dissolving oxygen molecules. The study demonstrated that chemical reactions as well as physical bond stress scissions are involved in the ultrasonic degradation of the copolymers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
266.
We have developed surface-assisted laser desorption/ionization mass spectrometry using zinc oxide (ZnO) nanoparticles with anisotropic shapes (ZnO-SALDI-MS). The mass spectra showed low background noises in the low m/z, i.e. less than 500 u region. Thus, we succeeded in SALDI ionization on low molecular weight organic compounds, such as verapamil hydrochloride, testosterone, and polypropylene glycol (PPG) (average molecular weight 400) without using a liquid matrix or buffers such as citric acids. In addition, we found that ZnO-SALDI has advantages in post-source decay (PSD) analysis and produced a simple mass spectrum for phospholipids. The ZnO-SALDI spectra for synthetic polymers of polyethylene glycol (PEG), polystyrene (PS) and polymethylmethacrylate (PMMA) showed the sensitivity and molecular weight distribution to be comparable to matrix-assisted laser desorption/ionization (MALDI) spectra with a 2,5-dihydroxybenzoic acid (DHB) matrix. ZnO-SALDI shows good performance for synthetic polymers as well as low molecular weight organic compounds. 相似文献
267.
Halohydrination of epoxy resins using sodium halides as cationizing agents in matrix-assisted laser desorption/ionization (MALDI) and desorption ionization on porous silicon mass spectrometry (DIOS-MS) were investigated. Different mass spectra were observed when NaClO(4) and NaI were used as the cationizing agents at the highest concentration of 10.0 mM, which is much higher than that normally used in MALDI-MS. MALDI mass spectra of epoxy resins using NaI revealed iodohydrination to occur as epoxy functions of the polymers. The halohydrination also occurred using NaBr, but not NaCl, due to the differences in their nucleophilicities. On the basis of the results of experiments using deuterated CD(3)OD as the solvent, the hydrogen atom source was probably ambient water or residual solvent, rather than being derived from matrices. Halohydrination also occurred with DIOS-MS in which no organic matrix was used; in addition, reduction of epoxy functions was observed with DIOS. NaI is a useful cationizing agent for changing the chemical form of epoxy resins due to iodohydrination and, thus, for identifying the presence of epoxy functions. 相似文献
268.
Fluorescence and electrochemical detection of pyrimidine/purine transversion by a ferrocenyl aminonaphthyridine derivative 总被引:1,自引:0,他引:1
A novel hydrogen bond-forming ligand for pyrimidine/purine transversion, which contains both a fluorescent naphthyridine moiety and a ferrocenyl group as an electrochemical indicator, is described. Hydrogen bond-mediated recognition for a target nucleobase at an abasic site in a DNA duplex is confirmed by both fluorescence and electrochemical measurements. The analysis by fluorescence titration reveals that the ligand shows significant fluorescent quenching upon formation of a 1 : 1 complex with the target nucleobase opposite the abasic site, and the selectivity is in the order of cytosine > thymine > adenine, guanine, reflecting the stability of the hydrogen bond formation. 相似文献
269.
Hiroaki Shimomoto Dai Fukami Shokyoku Kanaoka Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2011,49(9):2051-2058
Partially fluorinated poly(vinyl ether)s with C4F9 and C6F12H groups in the side chain were synthesized via living cationic polymerization in the presence of an added base in a fluorine‐containing solvent, dichloropentafluoropropanes. For comparison, the polymerization of vinyl ether monomers with C2F5 and C6F13 groups and nonfluorinated monomers were also carried out. The characterization of the product polymers using size exclusion chromatography with a fluorinated solvent as an eluent indicated that all polymers had narrow molecular weight distributions (Mw/Mn ~ 1.1). Interestingly, the moderately fluorinated polymers with C4F9 exhibited upper critical solution temperature‐type phase separation in various organic solvents with wide‐ranging polarities, whereas highly fluorinated polymers with C6F13 are insoluble in nonfluorinated solvents. Polymers with C4F9 groups exhibited temperature dependent solubility transitions not only in common organic solvents (e.g., toluene, chloroform, tetrahydrofuran, and acetone) but also in perfluoro solvents [e.g., perfluoro(methylcyclohexane) and perfluorodecalin]. On the other hand, the solubility of polymers with C6F12H showed completely different from that of polymers with C6F13, despite their similar fluorine content. In addition, various types of fluorinated block copolymers were prepared in a living manner. The block copolymers with a thermosensitive fluorinated segment underwent temperature‐induced micellization and sol–gel transition in various organic solvents. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
270.
A method for the catalytic hydrophosphinylation of internal ynamides with H-phosphinates has been developed for the first time. The protocol employing the catalyst generated from NiBr2 and PPh3 could be applied to several types of ynamides and H-phosphinates, affording (E)-β-aminovinylphosphinates in a highly regio- and stereoselective manner. 相似文献