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891.
Dr. Zhu Wu Fabian Dinkelbach Dr. Florian Kerner Dr. Alexandra Friedrich Prof. Dr. Lei Ji Dr. Vladimir Stepanenko Prof. Dr. Frank Würthner Prof. Dr. Christel M. Marian Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200525
Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers ( o -, m - and p - BrTAB ) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o - BrTAB , the short lifetime component is ascribed to the T1M state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T1A state of an aggregate, with multiple intermolecular interactions existing in crystalline o - BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently. 相似文献
892.
Dr. Fabian Reiß Dr. Alexander Villinger Dr. Harald Brand Dr. Wolfgang Baumann Dr. Dirk Hollmann Prof. Dr. Axel Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(33):e202200854
The oxidation of silylated hydrazine, (Me3Si)2N−N(H)SiMe3, with silver salts led to the formation of a highly labile hydrazinium-yl radical cation, [(Me3Si)2N−N(H)SiMe3].+, at very low temperatures (decomposition > −40 °C). EPR, NMR, DFT and Raman studies revealed the formation of a nitrogen-centered radical cation along the N−N unit of the hydrazine. In the presence of the weakly coordinating anion [Al{OCH(CF3)2}4]−, crystallization and structural characterization in the solid state were achieved. The hydrazinium-yl radical cation has a significantly shortened N−N bond and a nearly planar N2Si3 framework, in contrast to the starting material. According to DFT calculations, the shortened N−N bond has a total bond order of 1.5 with a π-bond order of 0.5. The π bond can be regarded as a three-π-electron, two-center bond. 相似文献
893.
Patrick Federmann Dr. Robert Müller Fabian Beckmann Caroline Lau Dr. Beatrice Cula Prof. Dr. Martin Kaupp Prof. Dr. Christian Limberg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(25):e202200404
Frustrated Lewis pairs (FLPs) composed of acidic alane and basic phosphane functions, separated by a xanthene linker, can be prepared through the corresponding Me3Sn derivative and methyl aluminum compounds with elimination of Me4Sn. This way MeClAl-, Cl2Al- and (C6F5)2Al- moieties could be introduced and the resulting FLPs are stabilized by a further equivalent of the alane precursors. In contact with the FLPs CO2 is bound via the C atom at the phosphane functions and the two O atoms at the Al centers. The residues at the latter determine the binding strength. Hence, in case of MeClAl CO2 capture occurs at higher pressure and under ambient conditions CO2 is released again, while for Cl2Al and (C6F5)2Al CO2 binding becomes irreversible. The results of DFT calculations rationalize these findings by the high thermodynamic stabilization in case of more electronegative residues, which concomitantly lead to higher barriers, and in case of (C6F5)2Al further stabilization is achieved through a low reorganization energy. 相似文献
894.
Peña-Cabrera E Aguilar-Aguilar A Gonzalez-Domínguez M Lager E Zamudio-Vazquez R Godoy-Vargas J Villanueva-García F 《Organic letters》2007,9(20):3985-3988
An unprecedented synthesis of 8-substituted-borondipyrromethenes is described starting from 8-thiomethylbodipy 1. Aryl, heteroaryl, alkenyl, and organometallic boronic acids smoothly reacted with 1 in the presence of a catalytic amount of Pd(0) and a stoichiometric amount of Cu(I)-2-thienylcarboxylate under neutral conditions to give the corresponding Bodipy analogues in good to quantitative yields (20 examples). A remarkable reactivity was observed in some cases, e.g., ferrocenylboronic acid gave the product in 98% isolated yield after only 10 min at 55 degrees C. 相似文献
895.
896.
Lower branch coherent states in plane Couette flow have an asymptotic structure that consists of O(1) streaks, O(R(-1)) streamwise rolls and a weak sinusoidal wave that develops a critical layer, for large Reynolds number R. Higher harmonics become negligible. These unstable lower branch states appear to have a single unstable eigenvalue at all Reynolds numbers. These results suggest that lower branch coherent states control transition to turbulence and that they may be promising targets for new turbulence prevention strategies. 相似文献
897.
Braunschweig H Kupfer T Radacki K Schneider A Seeler F Uttinger K Wu H 《Journal of the American Chemical Society》2008,130(25):7974-7983
A range of new iminoborylcomplexes of the type [L(n)M-B[triple bond]N-R], which are isoelectronic with sigma-alkynyl complexes [L(n)M-C[triple bond]C-R], was obtained by systematically varying the metal M, the coligands L, and the nitrogen bound substituent R. Selected examples include, for example, trans-[(Cy3P)2(Br)Pt(B[triple bond]N iBu)], which is characterized by a sterically less demanding N-R group or the unprecedented rhodium species cis,mer-[(Br)2(Me3P)3Rh(B[triple bond]NSiMe3)]. All compounds were fully characterized in solution by multinuclear NMR spectroscopy and, where appropriate, in the solid state by X-ray crystallography. Subsequent reactivity studies revealed that particularly the combination of smaller N-R groups with Pt-B linkages of increased stability opens up opportunities for novel reactivity patterns of this class of compounds. Within the scope of these study, we inter alia succeeded in synthesizing the unusual bridged boryl species 1,4-trans-[{(Cy3P)2(Br)Pt(B{NH iBu}NH)}2C6H4] and a complex bearing both an acetylide ligand and an iminoboryl ligand, respectively. 相似文献
898.
Walter M. F. Fabian 《Monatshefte für Chemie / Chemical Monthly》2008,139(4):309-318
The answer to the title question is definitely “yes” – at least for fairly small molecules. Computational procedures, namely the Weizmann (Wn) and Gaussian-3 (G3) family of methods, the complete basis set extrapolation scheme (CBS-x), the “high accuracy extrapolated ab initio thermochemistry” (HEAT) as well as the “correlation consistent composite approach” (ccCA), aimed at energies with chemical accuracy or even better (sub kJ?mol?1) are described and several applications illustrating the level of accuracy that can be achieved are presented. 相似文献
899.
Youzhi Xu Fabian Steudel Ming-Yi Leung Biao Xia Max von Delius Vivian Wing-Wah Yam 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302978
Both pillar[n]arenes (P[n]As) and [n]cycloparaphenylenes ([n]CPPs) play an important role in supramolecular chemistry. Herein, we report the precise synthesis of two multifunctional bismacrocycles [n]CPP-P[5]A by integrating P[5]A into the [n]CPP backbone. The photoluminescence quantum yield (ΦF) of the bismacrocycles was found to show a dramatic increase relative to the corresponding [n]CPPs. The chiral enantiomers (pR)/(pS)-[8]CPP-P[5]A were successfully isolated by chiral HPLC, and showed promising properties of circularly polarized luminescence (glum≈0.02). In addition, [n]CPP-P[5]A bismacrocycles are capable of binding pyridinium salts and fullerene derivatives with high affinity and specificity within the two distinct cavities. Transient absorption studies showed that photo-induced electron transfer occurs in [10]CPP-P[5]A⊃C60 complex. Our results suggest that [n]CPP-P[5]A are potentially useful in CPL-active materials, multiple guest recognition and supramolecular polymer preparation. 相似文献
900.
Chungseok Choi Fengyi Zhao James L Hart Yuanzuo Gao Fabian Menges Conor L. Rooney Nia J. Harmon Bo Shang Zihao Xu Sa Suo Quynh Sam Judy J. Cha Tianquan Lian Hailiang Wang 《Angewandte Chemie (International ed. in English)》2023,62(23):e202302152
We report a ternary hybrid photocatalyst architecture with tailored interfaces that boost the utilization of solar energy for photochemical CO2 reduction by synergizing electron and heat flows in the photocatalyst. The photocatalyst comprises cobalt phthalocyanine (CoPc) molecules assembled on multiwalled carbon nanotubes (CNTs) that are decorated with nearly monodispersed cadmium sulfide quantum dots (CdS QDs). The CdS QDs absorb visible light and generate electron-hole pairs. The CNTs rapidly transfer the photogenerated electrons from CdS to CoPc. The CoPc molecules then selectively reduce CO2 to CO. The interfacial dynamics and catalytic behavior are clearly revealed by time-resolved and in situ vibrational spectroscopies. In addition to serving as electron highways, the black body property of the CNT component can create local photothermal heating to activate amine-captured CO2, namely carbamates, for direct photochemical conversion without additional energy input. 相似文献