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81.
82.
Johannes C. B. Dietschreit Annika Wagner T. Anh Le Philipp Klein Prof. Dr. Hermann Schindelin Prof. Dr. Till Opatz Prof. Dr. Bernd Engels Prof. Dr. Ute A. Hellmich Prof. Dr. Christian Ochsenfeld 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12769-12773
The absence of fluorine from most biomolecules renders it an excellent probe for NMR spectroscopy to monitor inhibitor–protein interactions. However, predicting the binding mode of a fluorinated ligand from a chemical shift (or vice versa) has been challenging due to the high electron density of the fluorine atom. Nonetheless, reliable 19F chemical-shift predictions to deduce ligand-binding modes hold great potential for in silico drug design. Herein, we present a systematic QM/MM study to predict the 19F NMR chemical shifts of a covalently bound fluorinated inhibitor to the essential oxidoreductase tryparedoxin (Tpx) from African trypanosomes, the causative agent of African sleeping sickness. We include many protein–inhibitor conformations as well as monomeric and dimeric inhibitor–protein complexes, thus rendering it the largest computational study on chemical shifts of 19F nuclei in a biological context to date. Our predicted shifts agree well with those obtained experimentally and pave the way for future work in this area. 相似文献
83.
Franziska Pecho Dr. You-Quan Zou Johannes Gramüller Prof. Dr. Tadashi Mori Prof. Dr. Stefan M. Huber Dr. Andreas Bauer Prof. Dr. Ruth M. Gschwind Prof. Dr. Thorsten Bach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(23):5190-5194
A chiral phosphoric acid with a 2,2’-binaphthol core was prepared that displays two thioxanthone moieties at the 3,3’-position as light-harvesting antennas. Despite its relatively low triplet energy, the phosphoric acid was found to be an efficient catalyst for the enantioselective intermolecular [2+2] photocycloaddition of β-carboxyl-substituted cyclic enones (e.r. up to 93:7). Binding of the carboxylic acid to the sensitizer is suggested by NMR studies and by DFT calculations to occur by means of two hydrogen bonds. The binding event not only enables an enantioface differentiation but also modulates the triplet energy of the substrates. 相似文献
84.
Electron induced desorption of hydrogen on polycrystalline platinum has been studied in continuation of former work. The results
remain consistent with a supposed adsorption model implying that electron induced H+ emission is restricted to hydrogen adsorbed only at particular sites occupying not more than 1 per cent coverage. These sites
are ascribed to characteristic and stable surface impurities which are not influenced by the improved target treatment applied.
Depletion of sites by sputter cleaning is cancelled by recovery during annealing. The highest observed H+ yield (all available sites filled with hydrogen) is 2 · 10−5 ions per electron. The total cross section for desorption by electron impact is 2 · 10−17 cm2. Complex interaction phenomena between the electrons and the hydrogen covered platinum surface have been observed. 相似文献
85.
86.
87.
Blood analysis by Raman spectroscopy 总被引:1,自引:0,他引:1
Concentrations of multiple analytes were simultaneously measured in whole blood with clinical accuracy, without sample processing, using near-infrared Raman spectroscopy. Spectra were acquired with an instrument employing nonimaging optics, designed using Monte Carlo simulations of the influence of light-scattering-absorbing blood cells on the excitation and emission of Raman light in turbid medium. Raman spectra were collected from whole blood drawn from 31 individuals. Quantitative predictions of glucose, urea, total protein, albumin, triglycerides, hematocrit, and hemoglobin were made by means of partial least-squares (PLS) analysis with clinically relevant precision (r(2) values >0.93). The similarity of the features of the PLS calibration spectra to those of the respective analyte spectra illustrates that the predictions are based on molecular information carried by the Raman light. This demonstrates the feasibility of using Raman spectroscopy for quantitative measurements of biomolecular contents in highly light-scattering and absorbing media. 相似文献
88.
We report, for the first time, cw room temperature laser action of Cr3+:Gd3Sc2Al3O12. These crystals show a strong band fluorescence due to the transition with a lifetime of 150 μs. Laser pumping in the blue and red spectral range yields a minimum threshold of 170 mW and slope efficiencies up to 18.5%. The emission of the free running laser is centered at 784 nm with a FWHW of 5 nm. The extension of the Ga-garnets to Al-garnets as suitable host lattices for Cr3+ reveals the variety of garnet-structured crystals having an appropriate ligand field for continuously tunable laser operation. 相似文献
89.
Huber E. Frohlich K. Grill R. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(4):642-646
The recovery of a vacuum interrupter gap after short-circuit interruption was measured by application of an overshooting transient recovery voltage (TRV) several tens of microseconds after current zero. Copper chromium contact materials were employed varying in composition (25 and 50% chromium content), gas content, and production method. The gap failure was either pure dielectric or it was dominated by a significant postarc current. Therefore, postarc current phenomena were experimentally investigated focused on the relationship among the postarc current, the power frequency current amplitude, and the gap length. It was found that two postarc current maxima exist: the first strongly dependent on the power frequency current, and the second on the field strength. A correlation among postarc current facilitated failures, the ultimately dielectric recovery, and the erosion rate of the material was found. Strong indication is given that all of these effects are dominated by the metal vapor pressure rise given by the constricted rotating arc. A significant influence of the material properties can be drawn from these experiments, allowing a good estimation of the capability for short-circuit current interruption, thus providing a useful tool for material development 相似文献
90.
G. Huber T.A. Vilgis 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):217-223
The adsorption of a single ideal polymer chain on energetically heterogeneous and rough surfaces is investigated using a variational
procedure introduced by Garel and Orland (Phys. Rev. B 55, 226 (1997)). The mean polymer size is calculated perpendicular and parallel to the surface and is compared to the Gaussian
conformation and to the results for polymers at flat and energetically homogeneous surfaces. The disorder-induced enhancement
of adsorption is confirmed and is shown to be much more significant for a heterogeneous interaction strength than for spatial
roughness. This difference also applies to the localization transition, where the polymer size becomes independent of the
chain length. The localization criterion can be quantified, depending on an effective interaction strength and the length
of the polymer chain.
Received: 29 October 1997 / Revised: 19 December 1997 / Accepted: 6 March 1998 相似文献