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81.
Nicole M. Else-Quest Janet S. Hyde Ahalya Hejmadi 《Mathematical Thinking and Learning》2008,10(1):5-35
Mathematics is often thought of as a purely intellectual and unemotional activity. Recently, researchers have begun to question the validity of this approach, arguing that emotions and cognition are intertwined. The emotions expressed during mathematics work may be linked to mathematics achievement. We used behavioral measures to identify the emotions expressed by U.S. mothers and their 11-year-old children while solving pre-algebra tasks in the home. The most notable positive emotions displayed by mothers and children included positive interest, affection, joy, and pride, whereas the most notable negative emotions expressed included tension, frustration, and distress. Reflecting the social aspects of doing homework together, mothers' and children's emotions were highly correlated. Independent of pre-existing differences in knowledge, children's emotions were associated with their performance on a mathematics post-test: tension was linked to poorer performance while positive interest, humor, and pride were linked to better performance. We found no evidence of gender differences in the emotions while working the tasks, although boys responded with more tension following an incorrect solution than did girls. 相似文献
82.
Richard W. Middleton John Parrick Eric D. Clarke Peter Wardman 《Journal of heterocyclic chemistry》1986,23(3):849-855
A number of novel N-substituted-1,8-naphthalimides have been prepared and their fluorescence yields measured in water at pH 7.4. The type of substitutent and the substitution pattern on the naphthalimide nucleus produce markedly different fluorescence yields, (quantum efficiencies, ø varying from ø = 0-0037 for N-(3-N'-morpholino-1-propyl)-4-amino-3-methoxy-1,8-naphthalirnide (7) to ø = 0–77 for N-(3-bromopropyl)-4-acetamido-1,8-naphthalimide (31). 相似文献
83.
The use of palladium catalysts derived from 1,1′‐bis‐diisopropylphosphino‐ferrocene and a microwave heating source allows the coupling of a range of ortho‐substituted aryl bromides to diphenylphosphine derivatives to proceed in good yield in under 30 min. Optimization studies reveal that the combination of diphenylphosphine and DABCO is superior to more basic phosphide nucleophiles such as Ph2PK or Ph2PMgBr. High yields are only observed when moderately bulky electron rich diphosphines are used as ligands. The differences between P? C coupling and other cross‐coupling reactions are discussed in the light of the reactivity observed. Studies aimed at producing industrially important 1,2‐bis‐phosphino‐benzene ligands are also described. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
84.
β-Nitrostyrenes as electrophiles in Parham cyclization chemistry: reaction with o-lithiobenzonitrile
Adam J. Clarke 《Tetrahedron letters》2009,50(24):2949-2951
β-Nitrostyrenes react with o-lithiobenzonitrile, generated from the requisite aryl bromide at −100 °C by bromine-lithium exchange with n-butyllithium in THF, to afford 2-nitro-3-phenyl-3H-inden-1-ylamines resulting from 1,4-addition to the β-nitrostyrene followed by intramolecular capture of the resultant nitronate anion by the ortho-cyano functional group. 相似文献
85.
A first principles bottom-up study is performed on the high temperature polymorph of the thiazyl radical 1,3,5-trithia-2,4,6-triazapentalenyl, TTTA, a purely organic molecule-based magnet that shows thermal bistability, with the aim of getting a quantitative understanding at the molecular level the mechanism of thermal bistability and the factors that control the existence of a hysteresis loop. Experimental studies on crystals of TTTA have shown that it is a thermally bistable material that exhibits a broad hysteresis loop encompassing room temperature (the high temperature phase is paramagnetic, while the low temperature phase is magnetically silent). Both structures present 1D π-stacks and the changes in the magnetic properties up to now have been solely attributed to changes within these stacks, which in the high temperature phase are composed of evenly-spaced radicals and in the low temperature phase the radicals are separated by alternately long and short spacings. Our study shows that the magnetic topology of the high temperature polymorph is clearly 3D with important interactions between the stacks, however a 1D magnetic model gives a qualitative reproduction of the macroscopic magnetic properties. This suggests that a proper investigation into the origin of the bistability of this material requires consideration of the inter-stack interactions as well as looking at the difference in packing within the stacks. 相似文献
86.
87.
Adam A. Stokes David J. Clarke Stefan Weidt Pat Langridge-Smith C. Logan Mackay 《International journal of mass spectrometry》2010,289(1):54-57
We report high resolution spectra for the medium molecular weight proteins myoglobin and cytochrome-c obtained using a custom desorption electrospray ionisation (DESI) source coupled to a Bruker Daltonics 12 T Apex Qe Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS). The DESI source was designed for accurate alignment and reproduction of critical geometric variables. A two axis motorised stage was included to enable automated rastering of the sample under the DESI plume. Spectra for the intact proteins have been obtained under single-acquisition conditions and a top-down analysis of cytochrome-c was performed using both collision induced dissociation (CID) and electron capture dissociation (ECD) of the isolated [M+15H]15+ charge state. The sequence coverage is comparable to that obtained using electrospray ionisation, demonstrating the utility of top-down protein analysis by DESI FTICR-MS. 相似文献
88.
Ghosh S Carty D Clarke SP Corr SA Tekoriute R Gun'ko YK Brougham DF 《Physical chemistry chemical physics : PCCP》2010,12(42):14009-14016
We report the physico-chemical characterisation of fatty acid stabilised aqueous magnetic fluids, which are ideal systems for studying the influence of nanoparticle aggregation on the emergent magnetic resonance properties of the suspensions. Stable colloids of superparamagnetic magnetite, Fe(3)O(4), nanoparticle clusters in the 80 to 100 nm size range were produced by in situ nanoparticle growth and stabilisation, and by suspending pre-formed nanoparticles. NMR relaxation analysis shows that the magnetic resonance properties of the two types of suspension differ substantially and provides new insights into how the relaxation mechanisms are determined by the organisation of the nanoparticles within the clusters. 相似文献
89.
Nancy E. Clarke Samuel Fiorini Gwenaël Joret Dirk Oliver Theis 《Graphs and Combinatorics》2014,30(1):119-124
We consider the two-player, complete information game of Cops and Robber played on undirected, finite, reflexive graphs. A number of cops and one robber are positioned on vertices and take turns in sliding along edges. The cops win if, after a move, a cop and the robber are on the same vertex. The minimum number of cops needed to catch the robber on a graph is called the cop number of that graph. Let c(g) be the supremum over all cop numbers of graphs embeddable in a closed orientable surface of genus g, and likewise ${\tilde c(g)}$ for non-orientable surfaces. It is known (Andreae, 1986) that, for a fixed surface, the maximum over all cop numbers of graphs embeddable in this surface is finite. More precisely, Quilliot (1985) showed that c(g) ≤ 2g + 3, and Schröder (2001) sharpened this to ${c(g)\le \frac32g + 3}$ . In his paper, Andreae gave the bound ${\tilde c(g) \in O(g)}$ with a weak constant, and posed the question whether a stronger bound can be obtained. Nowakowski & Schröder (1997) obtained ${\tilde c(g) \le 2g+1}$ . In this short note, we show ${\tilde c(g) \leq c(g-1)}$ , for any g ≥ 1. As a corollary, using Schröder’s results, we obtain the following: the maximum cop number of graphs embeddable in the projective plane is 3, the maximum cop number of graphs embeddable in the Klein Bottle is at most 4, ${\tilde c(3) \le 5}$ , and ${\tilde c(g) \le \frac32g + 3/2}$ for all other g. 相似文献
90.
Investigation of the intramolecular Diels-Alder reactions of 6-fumaryl 1,3,8-nonatrienes, substituted at the C5 by a vinyl group, to afford the B-ring of FR182877 are reported. The synthesis of the required 1,3,8-nonatriene was achieved quickly and in high yield. 6-Fumaryl 1,3,8-nonatrienes substituted at the C5 by a vinyl group were found to undergo competing tandem sigmatropic rearrangement/Diels-Alder cyclisation when heated under standard Diels-Alder cyclisation conditions. This rearrangement became the exclusive pathway when the reaction was performed in the presence of a Lewis acid. As expected from modeling studies, the major intramolecular Diels-Alder cyclisation product was the desired exo-trans adduct, which was required for the synthesis of FR182877. Intrigued by the rearrangements, a number of alterations were made to the 1,3,8-nonatriene. Replacement of the fumaryl group by an acetyl group resulted in the diminished reactivity of the 1,3,8-nonatriene with neither rearrangements nor cycloadditions observed. Variation of the C5 substituent was found to be very important in determining the π-diastereoselectivity of the Diels-Alder cyclisation. 相似文献