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31.
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Jongbae?Heo Dagmara?S.?Antkiewicz Martin?M.?Shafer Dawn?A.?K.?Perkins Constantinos?Sioutas James?J.?SchauerEmail author 《Analytical and bioanalytical chemistry》2015,407(20):5953-5963
In order to further our understanding of the influence of chemical components and ultimately specific sources of atmospheric particulate matter (PM) on pro-inflammatory and other adverse cellular responses, we promulgate and apply a suite of chemical fractionation tools to aqueous aerosol extracts of PM samples for analysis in toxicity assays. We illustrate the approach with a study that used water extracts of quasi-ultrafine PM (PM0.25) collected in the Los Angeles Basin. Filtered PM extracts were fractionated using Chelex, a weak anion exchanger diethylaminoethyl (DEAE), a strong anion exchanger (SAX), and a hydrophobic C18 resin, as well as by desferrioxamine (DFO) complexation that binds iron. The fractionated extracts were then analyzed using high-resolution sector field inductively coupled plasma mass spectrometry (SF-ICPMS) to determine elemental composition. Cellular responses to the fractionated extracts were probed in an in vitro rat alveolar macrophages model with measurement of reactive oxygen species (ROS) production and the cytokine tumor necrosis factor-α (TNF-α). The DFO treatment that chelates iron was very effective at reducing the cellular ROS activity but had only a small impact on the TNF-α production. In contrast, the hydrophobic C18 resin treatment had a small impact on the cellular ROS activity but significantly reduced the TNF-α production. The use of statistical methods to integrate the results across all treatments led to the conclusion that sufficient iron must be present to participate in the chemistry needed for ROS activity, but the amount of ROS activity is not proportional to the iron solution concentration. ROS activity was found to be most related to cationic mono- and divalent metals (i.e., Mn and Ni) and oxyanions (i.e., Mo and V). Although the TNF-α production was not significantly affected by the chelexation of iron, it was greatly impacted by the removal of organics with the C18 resin and all other metal removal methods, suggesting that iron is not a critical pathway leading to TNF-α production, but a wide range of soluble metals and organic compounds in particulate matter play a role. Although the results are specific to the Los Angeles Basin, where the samples used in the study were collected, the method employed in the study can be widely employed to study the role of components of particulate matter in in vitro or in vivo assays. 相似文献
33.
Determination of hexavalent chromium (Cr(VI)) in plastics using organic-assisted alkaline extraction
An organic-assisted alkaline extraction method was developed for the determination of hexavalent chromium (Cr(VI)) in plastics. The solubilization of polymer as a pre-step of the alkaline extraction provided good extraction efficiency of Cr(VI) from the sample. The optimization of the experimental conditions affecting the extraction and UV–vis spectrophotometric analysis was accomplished by evaluating the recovery rate of Cr(VI) through the analysis of Cr(VI) in in-house polymer reference materials (RMs). With the proposed method, most of the Cr(VI) in polymers was released within a short extraction time of 30 min and the Cr(III)-DPCO complex can be kept stable for 24 h. The heating for the extraction of the Cr(VI) was not necessary. The optimal pH of the final solution was fixed at 2.0. The proposed extraction method was applied successfully for the determination of Cr(III) and Cr(VI) in spiked samples. The practical applicability of this new method was evaluated through the analysis of Cr(VI) in in-house polymer RMs. The good linearity was demonstrated at desired concentrations of the range 0–3.3 mg L−1. The detection limits were quite low, varying from 0.0061 to 0.0285 mg L−1. The recovery of Cr(VI) was between 97 and 106%, and the relative standard deviation (R.S.D.) was below 6%. 相似文献
34.
V. S. Grechishkin R. V. Grechishkina A. A. Shpilevoi A. A. Persichkin Hoon Heo 《Optics and Spectroscopy》2003,94(3):352-353
Remote detection of the spectra of double nuclear quadrupole resonance of nitrogen-containing compounds is considered. A comparison is made of this technique with the cross-relaxation method. 相似文献
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In situ grazing incidence small-angle X-ray scattering analysis was successfully performed during the thermal processing of film blends of polymethylsilsesquioxane (PMSSQ) precursor and triethoxysilyl-terminated six-arm poly(epsilon-caprolactone) (mPCL6) porogen. In addition, thermogravimetric analysis of the films was carried out in a nitrogen atmosphere. These measurements provide important information about the structures of the blend films and of the resulting porous films. In particular, they are used in this paper to establish the mechanism of the formation of imprinted pores within the blend films. During the heating run, the sacrificial thermal degradation of the porogen component commenced at 320 degrees C, generating pores in the resulting cured PMSSQ films. Only very limited porogen aggregation occurred during the blend film formation process (spin-coating and subsequent drying), and these porogen aggregates were of relatively small size and narrow size distribution. The observed restriction of the formation of such porogen aggregates was found to result from the favorable hybridization reaction of the porogen's reactive end groups with the reactive functional groups of the PMSSQ precursor, which competes with aggregation via reaction between the porogen molecules. The average radius (or half-size) of the porogen aggregates was in the range 2.45-3.98 nm, depending on the porogen loading (10-40 wt %). The porogen aggregates retained their size and size distribution until thermal degradation, which resulted in the imprinting of nanopores in the cured PMSSQ films with size and size distribution corresponding to those of the porogen aggregates. The porosities of the resulting nanoporous films were in the range 12.4-41.7%, depending on the initial porogen loading. 相似文献
37.
The crystal structure and thermal stability of two cadmium sulfide nanoclusters prepared in zeolite A (LTA) have been studied by XPS, TGA, and single-crystal and powder XRD. The crystal structures of Cd2.4Na3.2(Cd6S4)0.4(Cd2Na2S)0.6(H2O)> or =5.8[Si12Al12O48]-LTA (a = 12.2919(7) A, crystal 1 (hydrated)) and /Cd4Na2(Cd2O)(Na2O)/[Si12Al12O48]-LTA (a = 12.2617(4) A, crystal 2 (dehydrated)) were determined by single-crystal methods in the cubic space group Pm3m at 294(1) K. Crystal 1 was prepared by ion exchange of Na12-LTA in an aqueous stream 0.05 M in Cd2+, followed by washing in a stream of water, followed by reaction in an aqueous stream 0.05 M in Na2S. Crystal 2 was made by dehydrating crystal 1 at 623 K and 1 x 10(-6) Torr for 3 days. In crystal 1, Cd6S4(4+) nanoclusters were found in and extending out of about 40% of the sodalite cavities. Central to each Cd6S4(4+) cluster is a Cd4S4 unit (interpenetrating Cd2+ and S2- tetrahedra with near Td symmetry, Cd-S = 2.997(24) A, Cd-S-Cd = 113.8(12) degrees, and S-Cd-S = 58.1(24) degrees). Each of the two remaining Cd2+ ions bonds radially through a 6-ring of the zeolite framework to a sulfide ion of this Cd4S4 unit (Cd-S = 2.90(8) A). In each of the remaining 60% of the sodalite cavities of crystal 1, a planar Cd2Na2S4+ cluster was found (Cd-S/Na-S = 2.35(5)/2.56(14) A and Cd-S-Cd/Na-S-Na = 122(5)/92(7) degrees). Cd6S4(4+) and Cd2Na2S4+ are stable within the zeolite up to about 700 K in air. Upon vacuum dehydration at 623 K, all sulfur was lost (crystal 2). Instead as anions, only two oxide ions remain per sodalite unit. One bridges between two Cd2+ ions (Cd2O2+, Cd-O = 2.28(3) A) and the other between two Na+ ions (Na2O, Na-O = 2.21(10) A). 相似文献
38.
Jae Sang Lee Byung Ho Shin Byoung Yong Yoo Sun‐Young Nam Miji Lee Juhwan Choi Hansoo Park Young Bin Choy Chan Yeong Heo Won‐Gun Koh 《Macromolecular bioscience》2019,19(12)
The surface of poly(dimethylsiloxane) (PDMS) is grafted with poly(acrylic acid) (PAA) layers via surface‐initiated photopolymerization to suppress the capsular contracture resulting from a foreign body reaction. Owing to the nature of photo‐induced polymerization, various PAA micropatterns can be fabricated using photolithography. Hole and stripe micropatterns ≈100‐µm wide and 3‐µm thick are grafted onto the PDMS surface without delamination. The incorporation of PAA micropatterns provides not only chemical cues by hydrophilic PAA microdomains but also topographical cues by hole or stripe micropatterns. In vitro studies reveal that a PAA‐grafted PDMS surface has a lower proliferation of both macrophages (Raw 264.7) and fibroblasts (NIH 3T3) regardless of the pattern presence. However, PDMS with PAA micropatterns, especially stripe micropatterns, minimizes the aggregation of fibroblasts and their subsequent differentiation into myofibroblasts. An in vivo study also shows that PDMS samples with stripe micropatterns polarized macrophages into anti‐inflammatory M2 macrophages and most effectively inhibits capsular contracture, which is demonstrated by investigation of inflammation score, transforming‐growth‐factor‐β expression, number of macrophages, and myofibroblasts as well as the collagen density and capsule thickness. 相似文献
39.
B.-S. Jeong S.J. Pearton Y.W. Heo D.P. Norton A.F. Hebard 《Journal of magnetism and magnetic materials》2008
Hall effect measurements were performed on epitaxial CoxTi1−xO2–δ thin films grown on (0 0 1) LaAlO3 by reactive RF magnetron co-sputter deposition. Magnetization measurements reveal ferromagnetic behavior in M–H loop at room temperature for CoxTi1−xO2–δ thin films for which x?0.02. An anomalous Hall effect was observed for Co0.10Ti0.90O2−δ films grown with the partial pressure of water P(H2O)=4×10−4 Torr or less. These films exhibit a positive ordinary Hall coefficient and a positive magnetoresistance. X-ray diffraction on films grown under these conditions shows evidence for TinO2n−1 phase due to the deficiency of oxygen. In contrast, Hall measurements taken for undoped and Co-doped TiO2 thin films grown under more oxidizing conditions show only the ordinary Hall effect with a negative Hall coefficient consistent with n-type conduction. For these films, the magnetoresistance was positive and increased monotonically with increasing magnetic field. The results suggest that Co-doped TinO2n−1 may be a dilute magnetic semiconducting oxide for which the carriers couple to the spin polarization. 相似文献
40.
Dr. Jun Wang Jaeyoung Heo Dr. Changqiang Chen Dr. Andrew J. Wilson Prof. Prashant K. Jain 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18588-18592
We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyzes the electrochemical oxidation of ammonia to liberate hydrogen and the Au component absorbs visible light by the excitation of localized surface plasmon resonances. Under visible-light excitation, this catalyst exhibits enhanced electrochemical ammonia oxidation kinetics, outperforming previously reported electrochemical schemes. We trace the enhancement to a photochemical potential resulting from electron–hole carriers generated in the electrocatalyst by plasmonic excitation. The photopotential responsible for enhanced kinetics scales linearly with the light intensity—a general design principle for eliciting superlative photoelectrochemical performance from catalysts comprised of plasmonic metals or hybrids. We also determine a photochemical conversion coefficient. 相似文献