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871.
The previously formulated semiclassical theory (Zhao, Liang, and Nakamura, J. Phys. Chem. A 2006, 110, 8204) is used to study electron transfer in the Marcus inverted case by considering multidimensional potential energy surfaces of donor and acceptor. The Zhu-Nakamura formulas of nonadiabatic transition in the case of Landau-Zener type are incorporated into the approach. The theory properly takes into account the nonadiabatic transition coupled with the nuclear tunneling and can cover the whole range from weak to strong coupling regime uniformly under the assumption of fast solvent relaxation. The numerical calculations are performed for the 12-dimensional model of shifted harmonic oscillators and demonstrate that the reaction rate with respect to the electronic coupling shows a maximum, confirming the adiabatic suppression in the strong coupling limit. The adiabatic suppression is dramatically reduced by the effect of nuclear tunneling compared to the case that the Landau-Zener formula is used. The possible extension and applications to the case of the slow solvent dynamics are discussed. 相似文献
872.
Okumura Y Mizushima H Fujinaga K Sunamoto J 《Colloids and surfaces. B, Biointerfaces》2007,55(2):235-240
Immobilization of liposomal phospholipids onto Sephacryl S-1000 gels that were chemically conjugated with hydrophobic alkyl moieties, octyl, dodecyl and hexadecyl, was examined in batch mode interaction. Compared with the octyl gel, the dodecyl and the hexadecyl gels were found to immobilize the three to four times more phospholipids with the less hydrophobic moieties. The encapsulation of a water-soluble marker, with other evidences, suggests that the majority of the immobilized phospholipids maintained liposomal morphology. As the lipid of the interacting liposomes, egg yolk phosphatidylcholine (eggPC), 1,2-dimyristoylphosphatidylcholine (DMPC) and a mixture of DMPC and 1,2-dimyristamido-1,2-deoxyphosphatidylcholine were examined. At 22 °C, DMPC liposomes showed higher extent of immobilization than at 37 °C but not eggPC liposomes, suggesting that the phase of liposomal membrane could have influence on the immobilization. Exchange between the immobilized liposomes and free ones was found to be small, less than 3%. The gel that had been first interacted with liposomes to apparent saturation could further immobilize the newly added liposomes. The rate of this second immobilization was similar to that of the slow adsorption process; the both could be based on the same mechanism, possibly involving rearrangement of the immobilized liposomes on the gel as proposed by Lundahl. As had been observed in the flow mode, the immobilization had preference for smaller liposomes. In application of the system in batch mode, the size distributions of the immobilized liposomes and of those left in the supernatant may differ from that of the originally added liposomes. 相似文献
873.
Shigeru Shimizu Yujirou Aiki Hiroki Ikake Kimio Kurita 《Journal of Polymer Science.Polymer Physics》1999,37(16):2195-2199
Segment‐segment interaction of poly(methylmethacrylate) in t‐butyl alcohol‐water mixtures in poor solvent regime was studied. From the small‐angle X‐ray scattering measurements of semidilute solution range, the binary and ternary cluster integrals of polymer segments were determined from concentration dependence of the correlation length at various temperatures just above the upper critical solution temperature. We have calculated the contributions of the segment–segment interaction to the entropy and enthalpy from the measured temperature dependence of these interaction parameters and found that both quantities are negative and decrease with decreasing t‐butyl alcohol content. FT‐IR absorption peak of carbonyl group of poly(methylmethacrylate) shifts to the lower frequency with increasing water content. The implications of these findings are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2195–2199, 1999 相似文献
874.
Photosensitization mechanisms in photopolymer coating film containing an aminochalcone‐type dye sensitizer and a radical generating reagent, sensitizer dyes, (E)‐3‐(9‐julolidinyl)‐1‐phenyl‐2‐propen‐1‐one (A), (E)‐2‐(9‐julolidinyl)‐methylene‐1‐indanone (B), 9‐benzoyl‐2,3,6,7‐tetrahydro‐1H,5H‐benzo[i,j]‐furano‐[3,2‐g]quinolizine (C), 4‐(dimethylamino) chalcone (D) and a radical‐generating reagent, 2,4,6‐tris (trichloromethyl)‐1,3,5‐triazine (TCT), were investigated by laser flash photolysis using a total reflection cell. Weak fluorescence and strong broad triplet absorption were detected. The fluorescence was statically quenched by TCT at quenching distances (Rf) of 15, 14, 20 and 14 Å for A, B, C and D as well as the triplet initial absorption, at quenching distances (Rt) of 16, 16, 16 and 14 for A, B, C and D, similar to the fluorescence quenching distances. The triplet decay time of the dyes was inefficiently quenched by TCT with the rate constants (k q) of 1.9, 3.1, 0.7 and 1.0×105 mol−1/dm3/s for A, B, C and D. The sensitivity of photopolymers containing a sensitizer dye and a TCT was obtained at an excitation of 488 nm corresponding to the emission peaks of argon ion laser of 1.1, 0.2, 0.54 and 9.1 mJ cm2 for A, B, C and D. The results indicated that the static sensitization process from the fluorescent singlet excited state of the dyes to the ground state of TCT was predominant, and the high sensitivity for A and B was caused by the high absorbance at 488 nm and that for C by the high fluorescent quenching distance. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
875.
The synthesis and structure determination of adenosine‐derived monomeric building blocks for new oligonucleosides are described. Addition of Me3Si‐acetylide to the aldehyde derived from the known partially protected adenosine 1 led to the epimeric propargylic alcohols 2 and 3 , which were oxidised to the same ketone 4 , while silylation and deprotection led to 7 and 9 (Scheme 1). Introduction of an I substituent at C(8) of the propargylic silyl ethers 10 and 11 was not satisfactory. The protected adenosine 12 was, therefore, transformed in high yield into the 8‐chloro derivative 13 by deprotonation and treatment with PhSO2Cl; the iodide 15 was obtained in a similar way (Scheme 2). The 8‐Cl and the 8‐I derivatives 13 and 15 were transformed into the propargylic alcohols 17 , 18 , 25 , and 26 , respectively (Scheme 3). The propargylic derivatives 2 , 10 , 17 , 19 , 23 , 25 , and 27 were correlated, and their (5′R) configuration was determined on the basis of NOEs of the anhydro nucleoside 19 ; similarly, correlation of 3 , 11 , 18 , 20 , 24 , 26 , and 28 , and NOE's of 20 evidenced their (5′S)‐configuration. 相似文献
876.
Deprotection of the tetramer 24 , obtained by coupling the iodinated dimer 18 with the alkyne 23 gave the 8′,5‐ethynediyl‐linked adenosine‐derived tetramer 27 (Scheme 3). As direct iodination of C(5′)‐ethynylated adenosine derivatives failed, we prepared 18 via the 8‐amino derivative 17 that was available by coupling the imine 15 with the iodide 7 ; 15 , in its turn, was obtained from the 8‐chloro derivative 12 via the 4‐methoxybenzylamine 14 (Scheme 2). This method for the introduction of the 8‐iodo substituent was worked out with the N‐benzoyladenosine 1 that was transformed into the azide 2 by lithiation and treatment with tosyl azide (Scheme 1). Reduction of 2 led to the amine 3 that was transformed into 7 . 1,3‐Dipolar cycloaddition of 3 and (trimethylsilyl)acetylene gave 6 . The 8‐substituted derivatives 4a – d were prepared similarly to 2 , but could not be transformed into 7 . The known chloride 8 was transformed into the iodide 11 via the amines 9 and 10 . The amines 3 , 10 , and 16 form more or less completely persistent intramolecular C(8)N−H⋅⋅⋅O(5′) H‐bonds, while the dimeric amine 17 forms a ca. 50% persistent H‐bond. There is no UV evidence for a base‐base interaction in the protected and deprotected dimers and tetramers. 相似文献
877.
878.
The electronic and geometric structures of some novel donor-acceptor polymers containing alternating electron donating group X (X=CH2, SiH2, S, O or NH) and electron accepting group Y (Y=>C=CH2, >C=O, >C=CF2 or >C=C(CN)2) along the conjugated cis-polyacetylene backbone, obtained on the basis of the one-dimensional tight-binding self-consistent field-crystal orbital (SCF-CO) method at the MNDO-AMl level of approximation, are presented. 相似文献
879.
Metabolomics approach for determining growth-specific metabolites based on Fourier transform ion cyclotron resonance mass spectrometry 总被引:2,自引:0,他引:2
Takahashi H Kai K Shinbo Y Tanaka K Ohta D Oshima T Altaf-Ul-Amin M Kurokawa K Ogasawara N Kanaya S 《Analytical and bioanalytical chemistry》2008,391(8):2769-2782
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) is the best MS technology for obtaining exact mass
measurements owing to its great resolution and accuracy, and several outstanding FT-ICR/MS-based metabolomics approaches have
been reported. A reliable annotation scheme is needed to deal with direct-infusion FT-ICR/MS metabolic profiling. Correlation
analyses can help us not only uncover relations between the ions but also annotate the ions originated from identical metabolites
(metabolite derivative ions). In the present study, we propose a procedure for metabolite annotation on direct-infusion FT-ICR/MS
by taking into consideration the classification of metabolite-derived ions using correlation analyses. Integrated analysis
based on information of isotope relations, fragmentation patterns by MS/MS analysis, co-occurring metabolites, and database
searches (KNApSAcK and KEGG) can make it possible to annotate ions as metabolites and estimate cellular conditions based on
metabolite composition. A total of 220 detected ions were classified into 174 metabolite derivative groups and 72 ions were
assigned to candidate metabolites in the present work. Finally, metabolic profiling has been able to distinguish between the
growth stages with the aid of PCA. The constructed model using PLS regression for OD600 values as a function of metabolic profiles is very useful for identifying to what degree the ions contribute to the growth
stages. Ten phospholipids which largely influence the constructed model are highly abundant in the cells. Our analyses reveal
that global modification of those phospholipids occurs as E. coli enters the stationary phase. Thus, the integrated approach involving correlation analyses, metabolic profiling, and database
searching is efficient for high-throughput metabolomics.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
880.
Toshiyuki Hamura Takamitsu Hosoya Hiroki Yamaguchi Yokusu Kuriyama Mitsujiro Tanabe Makoto Miyamoto Yoshizumi Yasui Takashi Matsumoto Keisuke Suzuki 《Helvetica chimica acta》2002,85(11):3589-3604
A facile, divergent access to highly oxygenated benzocyclobutene derivatives was developed via the regioselective [2+2] cycloaddition of α‐alkoxybenzynes and ketene silyl acetals. The cycloadducts could be converted to selectively protected alkoxybenzocyclobutenediones, an attractive class of compounds for the synthesis of polyaromatic compounds. As one possible application, divergent access to a regioisomer pair of sulfonylphthalides for the Hauser approach to polyaromatic compounds is described. 相似文献