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71.
The differential solubility of two poly(ethyleneterphthalate) (PET) fibres was determined in one thermally treated substrate
and in another thermally untreated. In both cases, mixtures of phenol/tetrachloroethane with the appropriate composition were
used.
The non-dissolved fractions of the untreated PET fibre display a molecular mass and a crystallinity which increase on increase
of the temperature of the differential solubility test. In the case of the thermally treated substrate, both the molecular
mass and the crystallinity of the residual fraction remain constant on increase of the test temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
72.
The collision-induced dissociation of C(2)X(5)(+) (C(2)Cl(2)F(3)(+), C(2)Cl(3)F(2)(+) and C(2)Cl(4)F(+)) and C(2)X(4)(+.) ions (C(2)ClF(3)(+*), C(2)Cl(2)F(2)(+*), and C(2)ClF(3)(+*)) derived from three chlorofluoroethanes (the isomeric 1,1,1- and 1,1,2-trichlorotrifluoroethane and 1,1,1,2-tetrachlorodifluoroethane) was investigated by means of multi-stage mass spectrometric (MS(n)) experiments in an ion trap mass spectrometer. The observation of a common dissociation pattern for ions of any given elemental composition suggests that the experiments could not differentiate isomeric C(2)X(5)(+) ions formed from different neutral precursors and originally having different structures. For any given elemental composition, a common dissociation pattern was observed, suggesting that energy barriers for isomer interconversion are lower than for dissociation. For ions containing two or more fluorine atoms, the major (in some cases unique) dissociation involves C-C cleavage to form CX(3)(+) and CF(2). Energetically, CF(2) loss is always the most favorable reaction; mechanistically it implies, at least in some cases, rearrangement via halogen transfer from one carbon to the other (for example, in the case of the C(2)Cl(2)F(3)(+) species derived from 1,1,1-trichlorotrifluoroethane, which should have initially the Cl(2)C(+)-CF(3) structure). Similar behavior was observed with C(2)X(4)(+*) ions produced both from the three chlorofluoroethanes and from model alkenes (trifluorochloroethene and tetrachloroethene). The dissociation behavior of these C(2)X(4)(+*) species is characteristic of the ion composition, with no memory of the original neutral precursor structure. Specifically, C(2)Cl(2)F(2)(+*) ions dissociate uniquely via loss of CF(2), C(2)ClF(3)(+*) ions eliminate preferentially CF, with CF(2) loss being only a minor reaction, whereas C(2)Cl(3)F(+*) and C(2)Cl(4)(+*) dissociate exclusively via Cl elimination. 相似文献
73.
Carolina Carrillo‐Carrin Raquel Martínez María F. NavarroPoupard Beatriz Pelaz Ester Polo Ana Arenas‐Vivo Alessandro Olgiati Pablo Taboada Mahmoud G. Soliman Úrsula Cataln Sara Fernndez‐Castillejo Rosa Sol Wolfgang J. Parak Patricia Horcajada Ramon A. Alvarez‐Puebla Pablo delPino 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7152-7156
A plasmonic core–shell gold nanostar/zeolitic‐imidazolate‐framework‐8 (ZIF‐8) nanocomposite was developed for the thermoplasmonic‐driven release of encapsulated active molecules inside living cells. The nanocomposites were loaded, as a proof of concept, with bisbenzimide molecules as functional cargo and wrapped with an amphiphilic polymer that prevents ZIF‐8 degradation and bisbenzimide leaking in aqueous media or inside living cells. The demonstrated molecule‐release mechanism relies on the use of near‐IR light coupled to the plasmonic absorption of the core gold nanostars, which creates local temperature gradients and thus, bisbenzimide thermodiffusion. Confocal microscopy and surface‐enhanced Raman spectroscopy (SERS) were used to demonstrate bisbenzimide loading/leaking and near‐IR‐triggered cargo release inside cells, thereby leading to DNA staining. 相似文献
74.
Chelo Ferreira Jos L. Lpez Ester Prez Sinusía 《Journal of Computational and Applied Mathematics》2008,217(1):88-109
It has been shown in Ferreira et al. [Asymptotic relations in the Askey scheme for hypergeometric orthogonal polynomials, Adv. in Appl. Math. 31(1) (2003) 61–85], López and Temme [Approximations of orthogonal polynomials in terms of Hermite polynomials, Methods Appl. Anal. 6 (1999) 131–146; The Askey scheme for hypergeometric orthogonal polynomials viewed from asymptotic analysis, J. Comput. Appl. Math. 133 (2001) 623–633] that the three lower levels of the Askey table of hypergeometric orthogonal polynomials are connected by means of asymptotic relations. In Ferreira et al. [Limit relations between the Hahn polynomials and the Hermite, Laguerre and Charlier polynomials, submitted for publication] we have established new asymptotic connections between the fourth level and the two lower levels. In this paper, we continue with that program and obtain asymptotic expansions between the fourth level and the third level: we derive 16 asymptotic expansions of the Hahn, dual Hahn, continuous Hahn and continuous dual Hahn polynomials in terms of Meixner–Pollaczek, Jacobi, Meixner and Krawtchouk polynomials. From these expansions, we also derive three new limits between those polynomials. Some numerical experiments show the accuracy of the approximations and, in particular, the accuracy in the approximation of the zeros of those polynomials. 相似文献
75.
Development of Selective RabGGTase Inhibitors and Crystal Structure of a RabGGTase–Inhibitor Complex
76.
Manrubia SC Lázaro E Pérez-Mercader J Escarmís C Domingo E 《Physical review letters》2003,90(18):188102
We explore a mean-field model for the evolution of exponentially growing populations of mutating replicators. Motivated by recent in vitro experiments devised to analyze phenotypic properties of bacterial and viral populations subjected to serial population transfers, we allow our in silico individuals to undergo unrestricted growth before applying bottleneck events. Different dynamical regimes of our model can be mapped to different experimental situations. Numerical and analytical results for fitness distributions calculated at the statistically stationary states of the dynamics compare favorably with available experimental data. Our model and results provide a common framework to better understand populations evolving under different selection pressures. 相似文献
77.
Bennasar ML Zulaica E Juan C Alonso Y Bosch J 《The Journal of organic chemistry》2002,67(21):7465-7474
Several 4-substituted dihydropyridones or 2-pyridones have been prepared by nucleophilic addition of alpha-(methylsulfanyl)ester enolates to N-alkyl-2-fluoropyridinium salts, followed by acid hydrolysis or oxidation with concomitant hydrolysis, of the intermediate 2-fluoro-1,4-dihydropyridine adducts, respectively. Addition of the enolate derived from isopropyl alpha-(methylsulfanyl)butyrate to N-(quinolylmethyl)-2-fluoropyridinium triflate 21 followed by DDQ treatment gave pyridone 29, from which (+/-)-20-deoxycamptothecin (31), a known precursor of camptothecin, was synthesized by a radical cyclization-desulfurization, with subsequent elaboration of the lactone E ring by chemoselective reduction. A similar sequence starting from the enolate of a chiral 2-hydroxybutyric acid derivative (33) provides access to natural (+)-camptothecin (37). 相似文献
78.
Ester Gabetta 《Meccanica》1988,23(1):11-14
Summary Wave propagation in a stack of n slabs of equal thickness L/n, whose index of refraction is assumed to be random is considered. The behaviour of the wave function as n goes to infinity is studied.
Presented at the VIII Congresso Nazionale dell'Associazione Italiana Di Meccanica Teorica ed Applicata (AIMETA), Torino, Ottobre 1986. 相似文献
Sommario Si considera la propagazione ondosa in uno strato di materiale suddiviso in n parti di uguale spessore L/n, il cui indice di rifrazione è assunto aleatorio. Si studia il comportamento della funzione d'onda per n tendente a infinito.
Presented at the VIII Congresso Nazionale dell'Associazione Italiana Di Meccanica Teorica ed Applicata (AIMETA), Torino, Ottobre 1986. 相似文献
79.
The thermal and catalyzed Diels-Alder reactions of (+)-apoverbenone (1) with isoprene, 2, 3-dimethyl-1,3-butadiene, (E)-piperylene, (E)-1-methoxy-1,3-butadiene and cyclopentadiene are described; structural analysis by 1H and 13C-NMR spectroscopy is reported, and the syn-anti and endo-exo diastereoselectivity of the reactions is discussed. 相似文献
80.
Kristina Kotnik Tina Kosjek Uroš Krajnc Ester Heath 《Analytical and bioanalytical chemistry》2014,406(13):3179-3190
This study describes a procedure for determining eight benzophenone-derived compounds in surface waters and sediments. These include the pharmaceutical ketoprofen, its phototransformation products 3-ethylbenzophenone and 3-acetylbenzophenone, and five benzophenone-type ultraviolet (UV) filters. The proposed analytical method involves the pre-concentration of water samples by solid-phase extraction (SPE) and microwave-assisted extraction (MAE) of sediment samples followed by derivatization and analysis by gas chromatography–mass spectrometry. Different parameters were investigated to achieve optimal method performance. Recoveries of 91 to 96 % from water samples were obtained using HLB Oasis SPE cartridges, whereas MAE of sediments (30 min at 150 °C) gave recoveries of 80 to 99 %. Limits of detection were between 0.1 and 1.9 ng L?1 for water samples and from 0.1 to 1.4 ng g?1 for sediment samples. The developed method was applied to environmental samples and revealed the presence of UV filters in the majority of the surface waters with up to 690 ng L?1 of 2-hydroxy-4-methoxybenzophenone. By contrast, ketoprofen (≤2,900 ng L?1) and its degradation products (≤320 ng L?1) were found in only two rivers, both receiving wastewater treatment plant effluents. Sediment analysis revealed benzophenone to be present in concentrations up to 650 ng g?1, whereas concentrations of other compounds were considerably lower (≤32 ng L?1). For the first time, quantifiable amounts of two ketoprofen transformation products in the aqueous environment are reported. 相似文献