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81.
82.
By irradiation, the tetrahydropyranylarylketoacetal compounds led to isomers of spiro compounds. A competition between Norrish II and Paterno-Buchi reations was observed with unsaturated heterocyclic products. In the osidic series, the reaction was not stereoselective, but the photocyclisation works with rentention of configuration at low temperature. The acidic epimerisation of spiro C-1 sugars mainly yields the trans (α or β) isomers. 相似文献
83.
Alain Bekaert Pascale Lemoine Jean Daniel Brion Bernard Viossat 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(2):m76-m77
The title compound, tris[(R)‐2‐hydroxypropanamide‐κ2O,O′]zinc(II) tetrabromozincate, [Zn(C3H7NO2)3][ZnBr4], contains one monomeric six‐coordinate zinc complex cation and one tetrahedral [ZnBr4]2− anion. Both ZnII atoms lie on threefold axes. Coordination in the cation occurs via the amide and hydroxy O atoms [Zn—O = 2.074 (5) and 2.073 (6) Å] and has a distorted octahedral geometry, with cis‐O—Zn—O angles in the range 76.2 (2)–109.2 (2)°. In the crystal structure, the cations and anions are linked by N—H⋯Br and O—H⋯O hydrogen bonds, generating a three‐dimensional network. 相似文献
84.
Alarcón SH Palleschi G Compagnone D Pascale M Visconti A Barna-Vetró I 《Talanta》2006,69(4):1031-1037
Competitive electrochemical enzyme-linked immunosorbent assays based on disposable screen-printed electrodes have been developed for quantitative determination of ochratoxin A (OTA). The assays were carried out using monoclonal antibodies in the direct and indirect format. OTA working range, I50 and detection limits were 0.05-2.5 and 0.1-7.5 μg L−1, 0.35 (±0.04) μg L−1 and 0.9 (±0.1) μg L−1, 60 and 100 μg L−1 in the direct and indirect assay format, respectively. The immunosensor in the direct format was selected for the determination of OTA in wheat. Samples were extracted with aqueous acetonitrile and the extract analyzed directly by the assay without clean-up. The I50 in real samples was 0.2 μg L−1 corresponding to 1.6 μg/kg in the wheat sample with a detection limit of 0.4 μg/kg (calculated as blank signal −3σ). Within- and between-assay variability were less than 5 and 10%, respectively. A good correlation (r = 0.9992) was found by comparative analysis of naturally contaminated wheat samples using this assay and an HPLC/immunoaffinity clean-up method based on the AOAC Official Method 2000.03 for the determination of OTA in barley. 相似文献
85.
Marie Labat Jean-Blaise Brubach Alessandra Ciavardini Marie-Emmanuelle Couprie Erik Elkaim Pierre Fertey Tom Ferte Philippe Hollander Nicolas Hubert Emmanuelle Jal Claire Laulhé Jan Luning Olivier Marcouillé Thierry Moreno Paul Morin Francois Polack Pascale Prigent Sylvain Ravy Jean-Paul Ricaud Pascale Roy Mathieu Silly Fausto Sirotti Amina Taleb Marie-Agnès Tordeux Amor Nadji 《Journal of synchrotron radiation》2018,25(2):385-398
The investigation of ultrafast dynamics, taking place on the few to sub‐picosecond time scale, is today a very active research area pursued in a variety of scientific domains. With the recent advent of X‐ray free‐electron lasers (XFELs), providing very intense X‐ray pulses of duration as short as a few femtoseconds, this research field has gained further momentum. As a consequence, the demand for access strongly exceeds the capacity of the very few XFEL facilities existing worldwide. This situation motivates the development of alternative sub‐picosecond pulsed X‐ray sources among which femtoslicing facilities at synchrotron radiation storage rings are standing out due to their tunability over an extended photon energy range and their high stability. Following the success of the femtoslicing installations at ALS, BESSY‐II, SLS and UVSOR, SOLEIL decided to implement a femtoslicing facility. Several challenges were faced, including operation at the highest electron beam energy ever, and achievement of slice separation exclusively with the natural dispersion function of the storage ring. SOLEIL's setup also enables, for the first time, delivering sub‐picosecond pulses simultaneously to several beamlines. This last feature enlarges the experimental capabilities of the facility, which covers the soft and hard X‐ray photon energy range. In this paper, the commissioning of this original femtoslicing facility is reported. Furthermore, it is shown that the slicing‐induced THz signal can be used to derive a quantitative estimate for the degree of energy exchange between the femtosecond infrared laser pulse and the circulating electron bunch. 相似文献
86.
87.
Jessie Casimiro Bénédicte Lepoittevin Caroline Boisse-Laporte Marie-Geneviève Barthés-Labrousse Pascale Jegou Fran?ois Brisset Philippe Roger 《Plasma Chemistry and Plasma Processing》2012,32(2):305-323
With the aim of introducing primary amino groups on the surface of poly(ethylene terephthalate) (PET), two methods were compared—the
use of ammonia or a combination of nitrogen and hydrogen low-pressure microwave plasma. Several plasma parameters were optimized
on the reactor to increase the –NH2 surface density, which was estimated by colorimetric titration and X-ray photoelectron spectroscopy (XPS). These techniques
show that whatever the plasma treatment, almost 2 –NH2/nm2 are incorporated on PET films. Emission spectroscopy highlighted a correlation between the density of primary amino groups
and the ratio between an NH peak intensity and an Ar peak intensity (INH/IAr). Variation in surface hydrophilicity with aging in air after plasma treatment was monitored with contact angle measurements
and showed a hydrophobic recovery. This was confirmed by XPS, which suggests also that surfaces treated by NH3 plasma are more stable than surfaces treated by N2/H2. 相似文献
88.
A general and efficient procedure for the stereoselective synthesis of (E)-(1-propenyl)phenyl esters from readily accessible allylphenols has been developed. The process involves a two-step sequence consisting of the initial acylation of the allylphenols with an acid chloride, followed by catalytic CC bond isomerization in the resulting allylphenyl esters. The latter step was performed in methanol at 80 °C using catalytic amounts (0.5 mol %) of the commercially available bis(allyl)-ruthenium(IV) dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (C10H16=2,7-dimethylocta-2,6-diene-1,8-diyl). Reactions proceeded in high yields (68–93%) and short times (4–9 h) with complete E-selectivity. 相似文献
89.
We consider a newsvendor who earns a revenue from the sales of her product to end users as well as from multiple advertisers paying to obtain access to those end users. We study the optimal decisions of a price-taking and a price-setting newsvendor when the advertisers have private information about their willingness to pay. We focus on the impact of the number of advertisers on the newsvendor’s optimal decisions. We find that regardless of the number of advertisers, the newsvendor may exclude advertisers with a low willingness to pay and distort the price and inventory from their system-efficient levels to screen the advertisers. Moreover, the newsvendor’s decision to exclude an advertiser is based exclusively on that advertiser’s characteristics, and the newsvendor’s optimal decision thus reveals independence among the advertisers. Nonetheless, the profits of the newsvendor and the advertisers also display network effects as both increase in the number of advertisers. Finally, our numerical results show that the newsvendor prefers an equivalent single advertiser to multiple advertisers due to the pooling effect. 相似文献
90.
Conducting and chiral [Ni(dmit)(2)] dithiolene salts were obtained by electrocrystallization of the radical [n-Bu(4)N][Ni(dmit)(2)] salt in the presence of chiral, enantiopure trimethylammonium cations. Three different cations were investigated, namely, (R)-Ph(Me)HC*-NMe(3)(+), (S)-((t)Bu)(Me)HC*-NMe(3)(+), and (S)-(1-Napht)MeHC*-NMe(3)(+), noted (R)-1, (S)-2, and (S)-3. Salts of 1:3 stoichiometry were obtained with (R)-1 and (S)-2, formulated as [(R)-1][Ni(dmit)(2)](3) and [(S)-2][Ni(dmit)(2)](3)·(CH(3)CN)(2). They both crystallize in the P2(1)2(1)2(1) chiral space group, with three crystallographically independent complexes exhibiting different oxidation degrees. Another salt with 2:5 stoichiometry was isolated with (S)-3. The semiconducting character of the three salts (σ(RT) = 20-30 × 10(-3) S cm(-1)) finds its origin in a strong electron localization, favored by the large number of crystallographically independent [Ni(dmit)(2)] complexes in these chiral structures and their association into weakly interacting dimeric or trimeric motifs. Racemic salts with the same cations, obtained only with difficulties with the tert-butyl-containing (rac)-2 cation, afforded similar trimerized structures. The observed unusual stoichiometry and strong charge localization is tentatively assigned to the size and anisotropic charge distribution of the cations. 相似文献