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71.
This study presents the synthesis of a crosslinkable dextran as starting material for the development of new hydrogels as drug delivery system in dental applications. 2‐Hydroxyethyl methacrylate (HEMA) was coupled to dextran after activation with carbonyldiimidazole as monitored by FTIR and 1H‐NMR spectroscopy. The Dex‐HEMA was crosslinked by visible light in the presence of camphorquinone (CQ) as photoinitiator and a coinitiator in a proper solvent. Aliphatic or aromatic amines were used as coinitiators and the content of the coinitiator was varied from 0.25 to 3.0 mol %. Diphenyliodonium chloride was added as a third component to the above photoinitiation system. It was observed that, the degree of swelling decreased upon an increase of Dex‐HEMA concentration and the water content in the solvent system due to formation of more crosslinking points, that is, increasing crosslink density (Px). The type of coinitiator shows a prominent impact on the swelling behavior and crosslinking efficiency of hydrogels. Special cryofixation and cryofracture techniques were used to investigate the surface and interior of swollen Dex‐HEMA hydrogel samples by SEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
72.
Electromigration effects in interconnect metallizations cause a need for materials with superior resistance against electromigration failure but with adequate electrical properties. In principle, Cu(Ag) alloys are potential candidates to become an interconnect material of the next generation of microelectronic devices. Therefore, in the following paper the electroplating of such Cu(Ag) alloys from a sulfuric acid electrolyte solution with varying silver content in a home built deposition tool is presented. Besides the general deposition characteristics, the growth mode of the films and the deposition into trenches will be discussed. The investigations show that Cu(Ag) alloys can be deposited with adequate homogeneity of the film thickness by electroplating. Furthermore, the electrical resistivity is low enough to assure a use of these films for interconnect applications. However, distinct island growth and insufficient trench filling capabilities lead to the fact that the additive composition needs to be optimized for Cu(Ag) thin film electroplating. 相似文献
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Triple tangent flank milling of ruled surfaces 总被引:3,自引:0,他引:3
Cornelia Menzel 《Computer aided design》2004,36(3):289-296
This paper presents a positioning strategy for flank milling ruled surfaces. It is a modification of a positioning method developed by Bedi et al. [Comput Aided Des 35 (2003) 293]. A cylindrical cutting tool is initially positioned tangential to the two boundary curves on a ruled surface. Optimization is used to move these tangential points to different curves on the ruled surface to reduce the error. A second optimization step is used to additionally make the tool tangent to a rule line, further reducing the error and resulting in a tool position, where the tool is positioned tangential to two guiding rails and one rule line. The resulting surface has 88% less under cutting than the method of Bedi et al. 相似文献
76.
In the current study the savings of CO2 emissions due to the use of ground source heat pump (GSHP) systems was investigated in comparison to conventional heating systems. Based on a subsidy program for GSHP systems in southwest Germany, the regional, average, and total CO2 savings of 1105 installed GSHP systems were determined on a regional scale. The emitted CO2 per kWh of heating demand for the studied scenario resulted in 149 g CO2/kWh for GSHP using the German electricity mix and 65 g CO2/kWh using the regional electricity mix, which results in CO2 savings of 35% or 72%, respectively. Similar CO2 avoidances of GSHP systems were found in American and European studies ranging between 15% and 77% strongly depending on the supplied energy for the heat pumps and the efficiency of installation. The resulting CO2 savings for one installed GSHP unit in the present study therefore range between 1800 and 4000 kg per year. Nevertheless, the minimum average total annual CO2 savings of all installed GSHP systems due to the subsidy program amounted to 2000 tons per year. The maximum regional avoided additional CO2 emissions are primarily associated with the affluent suburbs of the most densely populated area in the region. In 2006 the total contribution of CO2 savings due to GSHP systems in Germany was only about 3.4% of the total renewable energies. However, continuously rising numbers of installed GSHP units and the increasing use of renewable electricity demonstrate that there is a fine opportunity to substantially avoid additional CO2 emissions associated with the provision of heating (and cooling) of buildings and other facilities. 相似文献
77.
Computational Economics - We study the functioning of informal value transfer systems through the example of Hawala. By complementing the institutional theory with computational experiments that... 相似文献
78.
Fabien Paulot David Paynter Vaishali Naik Sergey Malyshev Raymond Menzel Larry W. Horowitz 《International Journal of Hydrogen Energy》2021,46(24):13446-13460
Hydrogen (H2) has been proposed as an alternative energy carrier to reduce the carbon footprint and associated radiative forcing of the current energy system. Here, we describe the representation of H2 in the GFDL-AM4.1 model including updated emission inventories and improved representation of H2 soil removal, the dominant sink of H2. The model best captures the overall distribution of surface H2, including regional contrasts between climate zones, when vd(H2) is modulated by soil moisture, temperature, and soil carbon content. We estimate that the soil removal of H2 increases with warming (2–4% per K), with large uncertainties stemming from different regional response of soil moisture and soil carbon. We estimate that H2 causes an indirect radiative forcing of 0.84 mW m?2/(Tg(H2)yr?1) or 0.13 mW m?2 ppbv?1, primarily due to increasing CH4 lifetime and stratospheric water vapor production. 相似文献
79.
Memristive valence change memory (VCM) cells show a strong non-linearity in the switching kinetics which is induced by a temperature increase. In this respect, thermal crosstalk can be observed in highly integrated crossbar arrays which may impact the resistance state of adjacent devices. Additionally, due to the thermal capacitance, a VCM cell can remain thermally active after a pulse and thus influence the temperature conditions for a possible subsequent pulse. By using a finite element model of a crossbar array, it is shown that spatio-temporal thermal correlations can occur and are capable of affecting the resistive state of adjacent cells. This new functional behavior can potentially be used for future neuromorphic computing applications. 相似文献
80.
Philipp Tröber Alfred Hackl Harald Leitner Markus Welm Peter Demmel Matthias Golle Wolfram Volk 《国际钢铁研究》2023,94(4):2200456
Meeting the increasing demands on part quality and profitability of manufacturing processes despite difficult-to-machine materials is only possible with a deep understanding of the process. Herein, knowledge about the process temperature is of critical importance since it affects the material properties, such as hardness or forming behavior, as well as the chemical and physical interactions between the tool, workpiece, and lubricant. A proven thermoelectric method of temperature measurement in machining, forming, and blanking is a tool–workpiece thermocouple. Herein, instantaneous measurement of the temperature development is allowed in this setup during the manufacturing process in situ at the contact area of the tool and workpiece. The accuracy of this method is dependent on the calibration of the thermocouple, for which the Seebeck coefficients of the tool and workpiece material have to be determined. Usually, material samples from different batches are used for this purpose, although the resulting measurement errors due to slight changes in material properties are hardly known. The effects of small changes in the chemical composition and the transformation of the crystal lattice due to hardening on the Seebeck coefficient are investigated for the first time to allow precise quantification of the measurement error resulting from the calibration process. 相似文献