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691.
Total synthesis of echinopine A and B have been accomplished, based on a strategy that involved two transition-metal-mediated ene-yne cycloisomerizations. A modified Pd-catalyzed enyne cycloisomerization/intramolecular Diels-Alder cascade rendered a more streamlined synthesis of tricyclic ketone 15, and a Ru-catalyzed ene-yne cycloisomerization/cyclopropanation resembled the late-stage [5/7] → [3/5/5/7] ring-forming sequence in the proposed biosynthetic pathway. 相似文献
692.
A coumarin derivative was employed for the detection of biogenic amines in buffered aqueous solution by UV-Vis or fluorescence spectroscopy. Incorporated in a polymeric matrix, the dye can also be used for the optical detection of gaseous amines. 相似文献
693.
A simple assay for the detection of fluoride in water by fluorescence spectroscopy was developed. The assay is based on commercially available reagents and allows sensing of fluoride in the low millimolar concentration range with high selectivity over other anions. 相似文献
694.
Suddapalli Chaitanya Kumar Adolfo Esteban‐Martin Takuro Ideguchi Ming Yan Simon Holzner Theodor W. Hnsch Nathalie Picqu Majid Ebrahim‐Zadeh 《Laser \u0026amp; Photonics Reviews》2014,8(5):L86-L91
A few‐cycle, broadband, singly‐resonant optical parametric oscillator (OPO) for the mid‐infrared based on MgO‐doped periodically‐poled LiNbO3 (MgO:PPLN), synchronously pumped by a 20‐fs Ti:sapphire laser is reported. By using crystal interaction lengths as short as 250 µm, and careful dispersion management of input pump pulses and the OPO resonator, near‐transform‐limited, few‐cycle idler pulses tunable across the mid‐infrared have been generated, with as few as 3.7 optical cycles at 2682 nm. The OPO can be continuously tuned over 2179‐3732 nm (4589‐2680 cm‐1) by cavity delay tuning, providing up to 33 mW of output power at 3723 nm. The idler spectra exhibit stable broadband profiles with bandwidths spanning over 422 nm (FWHM) recorded at 3732 nm. The effect of crystal length on spectral bandwidth and pulse duration is investigated at a fixed wavelength, confirming near‐transform‐limited idler pulses for all grating interaction lengths. By locking the repetition frequency of the pump laser to a radio‐frequency reference, and without active stabilization of the OPO cavity length, an idler power stability better than 1.6% rms over >2.75 hours is obtained when operating at maximum output power, in excellent spatial beam quality with TEM00 mode profile. Photograph shows a multigrating MgO:PPLN crystal used as a nonlinear gain medium in the few‐cycle femtosecond mid‐IR OPO. The visible light is the result of non‐phase‐matched sum‐frequency mixing between the interacting beams. 相似文献
695.
Severin N. Habisreutinger Prof. Lukas Schmidt‐Mende Dr. Jacek K. Stolarczyk 《Angewandte Chemie (International ed. in English)》2013,52(29):7372-7408
Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail. 相似文献
696.
Aurel Pui Theodor MalutanLucia Tataru Corina MalutanDoina Humelnicu Gabriela Carja 《Polyhedron》2011,30(12):2127-2131
Some new Schiff bases derivates from 2-furaldehyde and phenylenediamines (L1-3) and their complexes with lanthanum (La), samarium (Sm), gadolinium (Gd) and erbium (Er) have been synthesized. These complexes with general formula [Ln(L1-3)2(NO3)2]NO3·nH2O (Ln = La, Sm, Gd, Er) were characterized by elemental analysis, UV-Vis, FT-IR and fluorescence spectroscopy, molar conductivity and thermal analysis. The metallic ions were found to be eight coordinated. The emission spectra of these complexes indicate the typical luminescence characteristics of the Sm(III), La(III), Er(III) and Gd(III) ions. 相似文献
697.
698.
Paul Varava Tak Hin Wong Zhaowen Dong Anastasia Yu. Gitlina Andrzej Sienkiewicz Wolfram Feuerstein Rosario Scopelliti Farzaneh Fadaei-Tirani Kay Severin 《Angewandte Chemie (International ed. in English)》2023,62(25):e202303375
The head-to-tail dimerization of N-heterocyclic diazoolefins is described. The products of these formal (3+3) cycloaddition reactions are strongly reducing quinoidal tetrazines. Oxidation of the tetrazines occurs in a stepwise fashion, and we were able to isolate a stable radical cation and diamagnetic dications. The latter are also accessible by oxidative dimerization of diazoolefins. 相似文献
699.
Fang-Che Hsueh Thayalan Rajeshkumar Bastiaan Kooij Rosario Scopelliti Kay Severin Laurent Maron Ivica Zivkovic Marinella Mazzanti 《Angewandte Chemie (International ed. in English)》2023,62(9):e202215846
Thorium redox chemistry is extremely scarce due to the high stability of ThIV. Here we report two unique examples of thorium arenide complexes prepared by reduction of a ThIV-siloxide complex in presence of naphthalene, the mononuclear arenide complex [K(OSi(OtBu)3)3Th(η6-C10H8)] ( 1 ) and the inverse-sandwich complex [K(OSi(OtBu)3)3Th]2(μ-η6,η6-C10H8)] ( 2 ). The electrons stored in these complexes allow the reduction of a broad range of substrates (N2O, AdN3, CO2, HBBN). Higher reactivity was found for the complex 1 which reacts with the diazoolefin IDipp=CN2 to yield the unexpected ThIV amidoalkynyl complex 5 via a terminal N-heterocyclic vinylidene intermediate. This work showed that arenides can act as convenient redox-active ligands for implementing thorium-ligand cooperative multielectron transfer and that the reactivity can be tuned by the arenide binding mode. 相似文献
700.