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281.
282.
Kosuke Makiguchi Tatsuya Saito Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2014,52(14):2032-2039
The ring‐opening polymerization (ROP) of β‐butyrolactone (β‐BL) has been studied using the organocatalysts of diphenyl phosphate (DPP) and bis(4‐nitrophenyl) phosphate (BNPP). The controlled ROP of β‐BL was achieved using BNPP, whereas that of using DPP was insufficient because of its low acidity. For the BNPP‐catalyzed ROP of β‐BL, the dual activation property for β‐BL and the chain‐end models of poly(β‐butyrolactone) (PBL) were confirmed by NMR measurements. The optimized polymerization condition for the ROP of β‐BL proceeded through an O‐acyl cleavage to produce the well‐defined PBLs with molecular weights up to 10,650 g mol?1 and relatively narrow polydispersities of 1.19–1.39. Functional initiators were utilized for producing the end‐functionalized PBLs with the ethynyl, maleimide, pentafluorophenyl, methacryloyl, and styryl groups. Additionally, the diblock copolymers consisting of the PBL segment with the polyester or polycarbonate segments were prepared by the BNPP‐catalyzed ROPs of ε‐caprolactone or trimethylene carbonate without quenching. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2032–2039 相似文献
283.
284.
Experimental data for the nuclear excitation of115In by positron annihilation with K-shell electrons have been examined, taking account of the effective thickness of an In target used, and then the cross section
res for resonance excitation to the 1078 keV energy level by positron annihilation has been reevaluated. The cross section for the process is induced by the measured effective cross section
eff of nuclear excitation of the isomeric level115mIn. In this work the effective thicknesses of the In target for positrons with kinetic energies 83.9 and 470 keV have been estimated. The effective thickness r has been determined from a relation r=E/ ¦dE/dr¦, where E is the positron energy width at 83.9 or 470 keV, r is the mean distance traversed by them, and ¦dE/dr¦ the stopping power of indium for them. In the present case,
K, the atomic-level width of the K-level of indium, is used as E. Neglecting a contribution from the 1464 keV level being much smaller than that from the 1078 keV level, a reevaluated value of
res has been obtained as 1.7×10–25 cm2. 相似文献
285.
Qian Duan Yutaka Miura Atsushi Narumi Xiande Shen Shin‐Ichiro Sato Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1117-1124
N–Isopropylacrylamide (NIPAM) was polymerized using 1‐pyrenyl 2‐chloropropionate (PyCP) as the initiator and CuCl/tris[2‐(dimethylamino)ethyl]amine (Me6TREN) as the catalyst system. The polymerizations were performed using the feed ratio of [NIPAM]0/[PyCP]0/[CuCl]0/[Me6TREN]0 = 50/1/1/1 in DMF/water of 13/2 at 20 °C to afford an end‐functionalized poly(N‐isopropylacrylamide) with the pyrenyl group (Py–PNIPAM). The characterization of the Py–PNIPAM using matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry provided the number–average molecular weight (Mn,MS). The lower critical solution temperature (LCST) for the liquid–solid phase transition was 21.7, 24.8, 26.5, and 29.3 °C for the Py–PNIPAMs with the Mn,MS's of 3000, 3400, 4200, and 5000, respectively; hence, the LCST was dramatically lowered with the decreasing Mn,MS. The aqueous Py–PNIPAM solution below the LCST was characterized using a static laser light scattering (SLS) measurement to determine its molar mass, Mw,SLS. The aqueous solutions of the Py–PNIPAMs with the Mn,MS's of 3000, 3400, 4200, and 5000 showed the Mw,SLS of 586,000, 386,000, 223,000, and 170,000, respectively. Thus, lowering the LCST for Py–PNIPAM should be attributable to the formation of the PNIPAM aggregates. The LCST of 21.7 °C for Py–PNIPAM with the Mn,MS of 3000 was effectively raised by adding β‐cyclodextrin (β‐CD) and reached the constant value of ~26 °C above the molar ratio of [β‐CD]/[Py–PNIPAM] = 2/1, suggesting that β‐CD formed an inclusion complex with pyrene in the chain‐end to disturb the formation of PNIPAM aggregates, thus raising the LCST. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1117–1124, 2006 相似文献
286.
287.
Chunhong Zhang Fangbin Liu Yufa Li Xiande Shen Xiaodong Xu Ryosuke Sakai Toshifumi Satoh Toyoji Kakuchi Yoshio Okamoto 《Journal of polymer science. Part A, Polymer chemistry》2013,51(10):2271-2278
Stereoregular poly(phenylacetylene) derivatives bearing L ‐leucine ethyl ester pendants, poly‐1 and poly‐2a , were, respectively, synthesized by the polymerization of N‐(4‐ethynylphenylcarbamoyl)‐L ‐leucine ethyl ester ( 1 ) and N‐(4‐ethynylphenyl‐carbonyl)‐L ‐leucine ethyl ester ( 2 ) using Rh(nbd)BPh4 as a catalyst, while stereoirregular poly‐2b was synthesized by solid‐state thermal polymerization of 2 . Their chiral recognition abilities for nine racemates were evaluated as chiral stationary phases (CSPs) for high‐performance liquid chromatography (HPLC) after coating them on silica gel. Both poly‐1 and poly‐2a with a helical conformation showed their characteristic recognition depending on coating solvents and the linkage groups between poly(phenylacetylene) and L ‐leucine ethyl ester pendants. Poly‐2a with a shorter amide linkage showed higher chiral recognition than poly‐1 with a longer urea linkage. Coating solvents played an important role in the chiral recognition of both poly‐1 and poly‐2a due to the different conformation of the polymer main chains induced by the solvents. A few racemates were effectively resolved on the poly‐2a coated with a MeOH/CHCl3 (3/7, v/v) mixture. The separation factors for these racemates were comparable to those obtained on the very popular CSPs derived from polysaccharide phenylcarbamates. Stereoirregular poly‐2b exhibited much lower chiral recognition than the corresponding stereoregular, helical poly‐2a , suggesting that the regular structure of poly(phenylacetylene) main chains is essential to attain high chiral recognition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
288.
Kosuke Makiguchi Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2011,49(17):3769-3777
The ring‐opening polymerizations (ROPs) of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) with pentafluorophenylbis(triflyl)methane (C6F5CHTf2) as the organocatalyst and alcohol initiators were carried out. For the ROP using 3‐phenyl‐1‐propanol (PPA) as the initiator in CH2Cl2 at room temperature with the [ε‐CL or δ‐VL]0/[PPA]0/[C6F5CHTf2] ratio of 50/1/0.1, the polymerization homogeneously proceeded to afford poly(ε‐caprolactone) (PCL) and poly(δ‐valerolactone) (PVL) having narrow polydispersity indices. The molecular weights of the obtained polymers determined from 1H NMR spectra showed good agreement with those estimated from the initial ratio of [ε‐CL or δ‐VL]0/[PPA]0 and monomer conversions. The 1H NMR, size exclusion chromatography, and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry measurements strongly indicated that PCL and PVL possessed the 3‐phenylpropoxy group as the α‐chain‐end and the hydroxy group as the ω‐chain‐end. In addition, the controlled/living nature for the C6F5CHTf2‐catalyzed ROP of lactones was confirmed by kinetic and chain‐extension experiments. The block copolymerization of PCL and PVL successfully proceeded to afford PCL‐b‐PVL and PVL‐b‐PCL. In addition, various end‐functionalized PCLs and PVLs with narrow molecular weight distributions were synthesized by the ROP of ε‐CL and δ‐VL using functional initiators, such as 6‐azido‐1‐hexanol, 2‐hydroxyethyl methacrylate, propargyl alcohol, N‐(2‐hydroxyethyl)maleimide, 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 5‐norbornene‐2‐methanol. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
289.
290.
Keita Fuchise Ryohei Kakuchi Sung‐Tso Lin Ryosuke Sakai Shin‐Ichiro Sato Toshifumi Satoh Wen‐Chang Chen Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2009,47(22):6259-6268
The precise synthesis and variation in the thermoresponsive property based on the supramolecular assembly of a novel urea end‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) were studied. A series of PNIPAMs with different diphenylurea groups at the chain end (X? Ph? NH? CO? NH? Ph? trz? PNIPAM: X = H, OCH3, CH3, NO2, Cl, and CF3) were synthesized by using a combination of the atom transfer radical polymerization and the copper(I)‐catalyzed azide‐alkyne cycloaddition. The cloud point of the obtained polymers depended on the hydrogen‐bonding ability of the introduced urea group. The 1H NMR measurement suggested that the obtained PNIPAM assembled in water via the intermolecular hydrogen bonding by the terminal urea group. From the dynamic light scattering and transmission electron microscopy measurements, the aggregated nanoparticles of the resulting polymer were directly observed in water at a temperature below its cloud point. The hydrogen‐bonding property of the chain end urea group was concluded to be involved in the aggregation of the PNIPAM in water, leading to the variation in its cloud point. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6259–6268, 2009 相似文献