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71.
Arrays of nanoscale interfaces between immiscible electrolyte solutions were formed using silicon nitride nanopore array membranes. Nanopores in the range from 75 nm radius down to 17 nm radius were used to form the nano-interfaces. It was found that the liquid organic phase electrolyte solution filled the pores so that inlaid nano-interfaces were formed with the aqueous phase. Cyclic voltammetry at these nano-interface arrays demonstrated steady-state behaviour at the larger interfaces but the voltammetric wave-shape became progressively worse as the interface size decreased. It was found that the ion transfer currents were ca. 50% of those expected based on theoretical calculations, which is attributed to overlap of diffusion zones at adjacent nano-interfaces. Here, the separation between adjacent nano-interfaces was 20-times the interface radius. The analytical sensitivity for ion transfer from the aqueous to the 1,6-dichlorohexane organic phase was estimated from calibration plots of current density versus concentration of aqueous tetraethylammonium cation. The sensitivity was in the range of 65 μA cm(-2) μM(-1) (at 75 nm radius interfaces) to 265 μA cm(-2) μM(-1) (at 17 nm radius interfaces). The sensitivity depended directly on the inverse of the nano-interface radius, implying that smaller interfaces will provide better sensitivity, due to the enhanced flux of analyte arising from convergent diffusion to smaller electrochemical interfaces. 相似文献
72.
Scalable and cost effective patterning of polymer structures and their surface textures is essential to engineer material properties such as liquid wetting and dry adhesion, and to design artificial biological interfaces. Further, fabrication of high-aspect-ratio microstructures often requires controlled deep-etching methods or high-intensity exposure. We demonstrate that carbon nanotube (CNT) composites can be used as master molds for fabrication of high-aspect-ratio polymer microstructures having anisotropic nanoscale textures. The master molds are made by growth of vertically aligned CNT patterns, capillary densification of the CNTs using organic solvents, and capillary-driven infiltration of the CNT structures with SU-8. The composite master structures are then replicated in SU-8 using standard PDMS transfer molding methods. By this process, we fabricated a library of replicas including vertical micro-pillars, honeycomb lattices with sub-micron wall thickness and aspect ratios exceeding 50:1, and microwells with sloped sidewalls. This process enables batch manufacturing of polymer features that capture complex nanoscale shapes and textures, while requiring only optical lithography and conventional thermal processing. 相似文献
73.
Hydrogen peroxide was employed as the terminal oxidant in the osmium tetroxide mediated oxidative cleavage of olefins, producing the corresponding aldehyde and ketone products. Aryl olefins are cleaved in good to excellent yield regardless of arene electronics. Alkyl olefins cleave in moderate to good yield for di- and tri-substituted alkenes. 相似文献
74.
Diimine and diamine ligands that are unable to coordinate to a single metal favour the formation of unusual, high-nuclearity Zn chlorometallate and palladium chloride complexes. 相似文献
75.
Erik D. Demaine Martin L. Demaine Vi Hart John Iacono Stefan Langerman Joseph O��Rourke 《Graphs and Combinatorics》2011,27(3):363-376
We construct the first two continuous bloomings of all convex polyhedra. First, the source unfolding can be continuously bloomed. Second, any unfolding of a convex polyhedron can be refined (further cut, by a linear number of cuts) to have a continuous blooming. 相似文献
76.
Denis A. Brosnan John P. Sanders Stephanie A. Hart 《Journal of Thermal Analysis and Calorimetry》2011,106(1):109-115
Thermal analysis techniques have been used in characterizing building materials from significant historic properties in the
Charleston, South Carolina area. Determining the chemical and physical effects of deterioration resulting from long periods
of exposure is a first step in formulating preservation strategies. In this regard, simultaneous thermal analysis coupled
with evolved gas analysis has been used to study reactions between air, seawater, and masonry materials. Further, the traditional
petrographic identification of mortar composition is greatly facilitated through use of thermal analysis. Simultaneous thermal
analysis allows for an exact determination of the calcium carbonate content in mortars as an alternative to the use of an
inferred value based on chemical analysis data. The partial dissolution of calcium carbonate in the presence of sea salt is
a major deterioration process. Further, natural cements manufactured in the United States are identified, in part, based on
their thermogravimetric (TG) traces and their evolved gases. The data indicates that natural cements form some carbonate phases
in addition to the major hydrate phases. Clay bricks are found to exhibit interaction with sea water, with uptake of bicarbonate
suggested. Additionally, there is evidence of re-hydroxylation in the 160 year old bricks. The bricks made in coastal zones
contain a considerable free silica fraction that is composed of a small percentage of cristobalite. The silica content of
the clay bricks is seen to result in very high thermal expansion coefficients in the area of 10 × 10−6 to 12 × 10−6 K−1. These studies provide guidance in restoration efforts where authenticity of cements is important. In the event that replacement
bricks are required, matching the thermal expansion coefficient of the original bricks is a requirement for preservation of
the masonry structure. 相似文献
77.
Aubert B Barate R Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges-Pous E Palano A Pappagallo M Pompili A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Borgland AW Breon AB Brown DN Button-Shafer J Cahn RN Charles E Day CT Gill MS Gritsan AV Groysman Y Jacobsen RG Kadel RW Kadyk J Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Oddone PJ Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA Barrett M Ford KE Harrison TJ Hart AJ Hawkes CM 《Physical review letters》2005,95(4):042001
We report the first measurement of the branching fraction f(00) for Gamma(4S) --> B(0)B(0). The data sample consists of 81.7 fb(-1) collected at the Gamma(4S) resonance with the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring. Using partial reconstruction of the decay B(0) --> D(*+) l(-)nu(l) in which only the charged lepton and the soft pion from the decay D(*+) --> D(0)pi(+) are reconstructed, we obtain f(00) = 0.487 +/- 0.010(stat) +/- 0.008(syst). Our result does not depend on the branching fractions of B(0) --> D(*+)l(-)nu(l) and D(*+) --> D(0)pi(+) decays, on the ratio of the charged and neutral B meson lifetimes, nor on the assumption of isospin symmetry. 相似文献
78.
This paper reports on the development of a novel electrochemical assay for Zn2+ in human sweat, which involves the use of disposable screen-printed carbon electrodes (SPCEs). Initially, SPCEs were used in conjunction with cyclic voltammetry to study the redox characteristics of Zn2+ in a selection of supporting electrolytes. The best defined cathodic and anodic peaks were obtained with 0.1 M NaCl/0.1 M acetate buffer pH 6.0. The anodic peak was sharp and symmetrical which is typical for the oxidation of a thin metal film on the electrode surface. This behaviour was exploited in the development of a differential pulse anodic stripping voltammetric (DPASV) assay for zinc. It was shown that a deposition potential of −1.6 V versus Ag/AgCl and deposition time of 60 s with stirring (10 s equilibration) produced a well-defined stripping peak with Epa = −1.2 V versus Ag/AgCl. Using these conditions, the calibration plot was linear over the range 1 × 10−8 to 5 × 10−6 M Zn2+. The precision was examined by carrying out six replicate measurements at a concentration of 2 × 10−6 M; the coefficient of variation was calculated to be 5.6%. The method was applied to the determination of the analyte in sweat from 10 human volunteers. The concentrations were between 0.39 and 1.56 μg/mL, which agrees well with previously reported values. This simple, low-cost sensitive assay should have application in biomedical studies and for stress and fatigue in sports studies. 相似文献
79.
80.
Leslie Hart 《Fresenius' Journal of Analytical Chemistry》1933,95(1-3):62-63
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