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71.
Correlations predicting frictional pressure drop and liquid holdup during horizontal gas-liquid pipe flow with a small liquid holdup 总被引:1,自引:0,他引:1
Experimental data and correlations available in the literature for the liquid holdup εL and the pressure gradient ΔPTP/L for gas-liquid pipe flow, generally, do not cover the domain 0 < εL < 0.06. Reliable pressure-drop correlations for this holdup range are important for calculating flow rates of natural gas, containing traces of condensate. In the present paper attention is focused on reliable measurements of εL and ΔPTPIL values and on the development of a phenomenological model for the liquid-holdup range 0 < εL < 0.06. This model is called the “apparent rough surface” model and is referred to as the ARS model. The experimental results presented in this paper refer to air-water and air-water + ethyleneglycol systems with varying transport properties in horizontal straight smooth glass tubes under steady-state conditions. The holdup and pressure gradient values predicted with the ARS model agree satisfactorily with both our experimental results and data obtained from the literature referring to small liquid-holdup values 0 < εL < 0.06. Further, it has been shown that in the domain 38 < < 72 mPa m the interfacial tension of the gas-liquid system has no significant effect on the liquid holdup. The pressure gradient, however, increases slightly with decreasing surface tension values. 相似文献
72.
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
73.
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
74.
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
75.
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
76.
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
77.
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
78.
Using a previous qualitative explanation to describe the transport properties of polycrystalline La2/3Ca1/3MnO3 thick films, we achieved a good fit of the temperature dependence of the resistance R(T). Depending on the sample, we have observed different metal–insulator (MI) transitions while the magnetic behavior is always similar. Small regions of depleted Tc adjacent to the grain boundary could have an important resistance contribution without affecting the magnetic properties in an appreciable manner. In this work, we achieve a quantitative explanation for the different transport behaviors that we have observed experimentally. 相似文献
79.
80.