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71.
Akiko Ohno Nana Kawasaki Kiyoshi Fukuhara Haruhiro Okuda Teruhide Yamaguchi 《Magnetic resonance in chemistry : MRC》2010,48(2):168-172
Complete NMR analysis of oxytocin (OXT) in phosphate buffer was elucidated by one‐dimensional (1D)‐ and two‐dimensional (2D)‐NMR techniques, which involve the assignment of peptide amide NH protons and carbamoyl NH2 protons. The 1H? 15N correlation of seven amide NH protons and three carbamoyl NH2 protons were also shown by HSQC NMR of OXT without 15N enrichment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
72.
Hideya Kawasaki Naoyuki Takahashi Hiroki Fujimori Kouji Okumura Takehiro Watanabe Chisato Matsumura Syusuke Takemine Takeshi Nakano Ryuichi Arakawa 《Rapid communications in mass spectrometry : RCM》2009,23(20):3323-3332
The pyrolytic highly oriented graphite polymer film (PGS) was first employed to analyze low‐mass analytes in environmental analysis by surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS). PGS is a synthetic uniform and highly oriented graphite polymer film with high thermal anisotropic conductivity. We have found that negative ion mode SALDI‐MS using oxidized PGS (PGS‐SALDI‐MS) can be used to detect [M–H]? ions from perfluorooctanoic acid (PFOA) and other perfluoroalkylcarboxylic acids when the PGS surface is modified with the cationic polymer polyethyleneimine (PEI). The signal intensity of PFOA when employing the PEI modification showed a ten‐fold increase over that obtained from desorption/ionization on porous silicon (DIOS). PFOA was quantified using PGS‐SALDI‐MS and the calibration curve showed a wide linear dynamic range of response (20–1000 ppb). The combination of atmospheric pressure ionization and PGS (AP‐PGS‐SALDI) showed greater signal intensity than vacuum PGS‐SALDI for deprotonated PFOA. Several other environmentally important chemicals, including perfluoroalkylsulfonic acid, pentachlorophenol, bisphenol A, 4‐hydroxy‐2‐chlorobiphenyl, and benzo[a]pyrene, were also successfully used to evaluate PGS‐SALDI‐MS. In addition, we found that nonafluoro‐1‐butanesulfonic acid was able to produce protonated peptides in positive ion PGS‐SALDI‐MS, but that perfluoropentanoic acid and trifluoroacetic acid were not. It is suggested that perfluoroalkylsulfonic acids are better protonating agents than perfluoroalkylcarboxylic acids in SALDI‐MS. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
73.
74.
We develop a statistical theory of growing domain structures in quenched systems with multiple-degenerate ground states where the order parameter is not conserved. Exact formulas are derived for the non-equilibrium structure functions for growing domains. As concrete examples the theory is applied to the p-state Johnson-Mehl model and the p-state cell model where the structure functions of the growing domains and the volume fraction of the metastable domain are calculated explicitly. 相似文献
75.
H. Katsuura H. Kawamura M. Manabe H. Kawasaki H. Maeda 《Colloid and polymer science》2002,280(1):30-37
The binding of a cationic surfactant, dodecylpyridinium (C12Py) chloride, with a low-charge-density poly (methacrylic acid)
(PMA) was investigated in buffer solutions under the condition of constant pH. The binding isotherms with PMA consisted of
two and three steps at a pH lower and higher than 3.2, respectively. Bindings in the first step were independent of pH and
this step was considered to correspond to the solubilization of the hydrocarbon chains of C12Py into the nonpolar region of
the compact form of PMA. This is the indication of the compact form from the binding isotherm. At pH higher than 3.2, the
second step was discriminated and it depended on the pH. In the third step, a sharp rise in the degree of binding (β) was
observed accompanying the solubilization of the precipitates of the PMA–C12Py complex. The binding with poly(acrylic acid)
(PAA) and PMA in conventional unbuffered NaCl solutions was also examined and the pH profile of the solution during the binding
process was determined. In the case of unbuffered NaCl solutions, the binding with PAA took place cooperatively at the critical
association concentration (cac). The binding isotherm consisted of two steps and the pH decreased with the increase in β.
The binding isotherm of PMA, on the other hand, consisted of three steps: the pH decreased slightly in the first step and
considerably in the second step with the increase in β but it increased with β in the third step, exhibiting a pH minimum
around 3.2. The binding in the first step coincided with that obtained in the buffered solutions. Linear relationships between
β and the pH were found for both polymers. In the case of PMA, no cac was observed in both buffered and unbuffered NaCl solutions.
Received: 24 January 2001 Accepted: 23 May 2001 相似文献
76.
Dr. Hideya Kawasaki Teruyuki Yao Takashi Suganuma Kouji Okumura Dr. Yuichi Iwaki Prof. Tetsu Yonezawa Tatsuya Kikuchi Prof. Ryuichi Arakawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(35):10832-10843
We report a new and facile method for synthesizing 3D platinum nanoflowers (Pt Nfs) on a scratched silicon substrate by electroless galvanic displacement and discuss the applications of the Pt Nfs in surface‐assisted laser desorption/ionization‐mass spectrometry (SALDI‐MS). Surface scratching of n‐type silicon is essential to induce Pt Nf growth on a silicon substrate (to obtain a Pt Nf silicon hybrid plate) by the galvanic displacement reaction. The Pt Nf silicon hybrid plate showed excellent SALDI activity in terms of the efficient generation of protonated molecular ions in the absence of a citrate buffer. We propose that the acidity of the Si? OH moieties on silicon increases because of the electron‐withdrawing nature of the Pt Nfs; hence, proton transfer from the Si? OH groups to the analyte molecules is enhanced, and finally, thermal desorption of the analyte ions from the surface occurs. Signal enhancement was observed for protonated molecular ions produced from a titania nanotube array (TNA) substrate on which Pt nanoparticles had been photochemically deposited. Moreover, surface modification of the Pt Nf silicon hybrid plate by perfluorodecyltrichlorosilane (FDTS) (to obtain an FDTS‐Pt Nf silicon hybrid plate) was found to facilitate soft SALDI of labile compounds. More interestingly, the FDTS‐Pt Nf silicon hybrid plate acts 1) as a high‐affinity substrate for phosphopeptides and 2) as a SALDI substrate. The feasibility of using the FDTS‐Pt Nf silicon hybrid plate for SALDI‐MS has been demonstrated by using a β‐casein digest and various analytes, including small molecules, peptides, phosphopeptides, phospholipids, carbohydrates, and synthetic polymers. The hybridization of Pt Nfs with a scratched silicon substrate has been found to be important for achieving excellent SALDI activity. 相似文献
77.
Tsuneomi Kawasaki 《Journal of fluorine chemistry》2010,131(4):525-1118
Amplification of enantiomeric enrichment is a key feature for the chemical evolution of biological homochirality from the origin of chirality. The aggregations of the enantiomers by diastereomeric interactions enable the modification of their enantiomeric excess during some chemical processes. Fluorine-containing chiral compounds possess large amplification effect via distillation, sublimation and achiral chromatography by self-disproportionation. Asymmetric amplifications in enantioselective catalysis occur by the differential formation and reactivity between homochiral and heterochiral aggregate in solution.We described the amplification of ee in asymmetric autocatalysis of 5-pyrimidyl alkanol in the reaction between diisopropylzinc and pyrimidine-5-carbaldehdye. During the reactions extremely low ee (ca. 0.00005% ee) can be amplified to achieve more than 99.5% ee. Since the proposed origins of chirality such as CPL, quartz, chiral organic crystals of achiral compounds and statistical fluctuation of ee can initiate the asymmetric autocatalysis with amplification of ee, the proposed origin of chirality can be linked with enantiopure organic compound in conjunction with amplification of ee by asymmetric autocatalysis. In addition, we described that the carbon isotopically chiral compound triggers the asymmetric autocatalysis of 5-pyrimiodyl alkanol to afford the enantioenriched product with the absolute configuration correlated with that of carbon isotope chirality, that is, isotope chirality including hydrogen isotopes can control the enantioselectivity of asymmetric addition of alkyl metal reagent to aldehyde. 相似文献
78.
79.
Takesi Kawasaki 《代数通讯》2013,41(12):4385-4396
Let A be a Noetherian ring.We consider the existence of Cohen-Macaulay Rees algebras of A. If the non-Cohen-Macaulay locus of A is of dimension 0, then we already know that such a Rees algebra exists. In the present paper, we show that such a Rees algebra also exists when the non-Cohen-Macaulay locus of A is of dimension 1. 相似文献
80.
Stereoselective reactions. XVIII. Synthesis and cytotoxicity of the demethyl derivatives of steganes
Demethyl derivatives of steganes and deoxypodorhizon, 3, 4, 6, 7, 9, 10, 12, 13, 18, 23, were prepared by the selective demethylation of the methoxy group of steganes and deoxypodorhizon, 2, 5, 8, 11, 22. The cytotoxicity of these derivatives was evaluated against KB cell and was found not to exceed that of the parent steganes. 4-Demethyldeoxypodorhizon (18) was found to show more potent cytotoxicity than deoxypodorhizon. 相似文献