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41.
The presence of microvoids in aramid fibres has been suspected for some time. This communication reports their detection together with an investigation of their distribution and size in Kevlar 29 and 49 by electron microscopy and X-ray diffraction techniques. The voids appear to be located mainly around the periphery of the fibres and their dimensions measured from direct microscope examinations are compared with those obtained from a Guinier-type analysis of the low-angle X-ray diffraction data. 相似文献
42.
43.
J. F. Branthaver Muhammed Nazir J. C. Petersen S. M. Dorrence Michael J. Ryan 《Petroleum Science and Technology》1984,2(1):67-89
Four selected asphalts were blended with zero to five wt. percent of fractions rich in vamady cheltes prepared from two crude oils. The mixture was -coated in a teflon -support, and the whole was heated in an oven at. 113±2°C for 24 hours. The mixture then was analyzed for increases ketone, acid and anhydride functions.
in general, functions rich in vanady ponphyrims tended to promote asphalt oxidation, particularly as measured by increase in kentones. Corelation of vanadyl ponphyrim concentration with asphalt oxidation is observed to the direct only if asphalts are mixed with varying amounts of the same fraction derived from the same crude Possible reasons for this phenomenon are discussed in terms of oxidation susceptibility of aspha1ts, the importance of molecular associations, and the relative catalytic activities of metallaporphyrins and other metal chelates 相似文献
in general, functions rich in vanady ponphyrims tended to promote asphalt oxidation, particularly as measured by increase in kentones. Corelation of vanadyl ponphyrim concentration with asphalt oxidation is observed to the direct only if asphalts are mixed with varying amounts of the same fraction derived from the same crude Possible reasons for this phenomenon are discussed in terms of oxidation susceptibility of aspha1ts, the importance of molecular associations, and the relative catalytic activities of metallaporphyrins and other metal chelates 相似文献
44.
Ratliff BM Hayat MM Tyo JS 《Journal of the Optical Society of America. A, Optics, image science, and vision》2005,22(2):239-249
A generalization of a recently developed algebraic scene-based nonuniformity correction algorithm for focal plane array (FPA) sensors is presented. The new technique uses pairs of image frames exhibiting arbitrary one- or two-dimensional translational motion to compute compensator quantities that are then used to remove nonuniformity in the bias of the FPA response. Unlike its predecessor, the generalization does not require the use of either a blackbody calibration target or a shutter. The algorithm has a low computational overhead, lending itself to real-time hardware implementation. The high-quality correction ability of this technique is demonstrated through application to real IR data from both cooled and uncooled infrared FPAs. A theoretical and experimental error analysis is performed to study the accuracy of the bias compensator estimates in the presence of two main sources of error. 相似文献
45.
Advances in processing of superconductors has demonstrated that ceramic powders with exact composition, super-homogeneity,
and extremely fine particle size can be prepared by chemical processing to achieve high density and uniform microstructure.
The chemical processing routes have great advantage in preparing powder with high reactivity thus promoting solid state reactions
required to produce ‘purer’ superconducting phase. We have studied extensively the coprecipitation technique for the preparation
of superconducting ceramic powders. Chemical solution methods have been used in order to model several superconducting systems
and to predict optimum conditions for obtaining exact composition. Several improvements on the control of precipitation reaction
have been implemented in order to obtain powders of few nanometers in size. This has been done by carrying out the reaction
in the bulk of a solution or in microemlusion systems. The corecipitated precursor powder has been used for production of
20− 30 meter long Ag-clad tapes. These tapes require considerably reduced processing times. By controlled heat treatment conditions,
these tapes have been processed to carry transport critical current density, Jc <4 × 104 A/cm2 at 77K in zero applied field. 相似文献
46.
Mehmet Sagbas Umut E. Ayten Herman Sedef Muhammed Koksal 《AEUE-International Journal of Electronics and Communications》2009,63(5):423-427
In this letter, a new floating inductance simulator circuit is presented. The proposed structure consists of only one grounded capacitor without any external resistors and two different active elements. The active elements are dual-output current-controlled current conveyor (DO-CCCII) and operational transconductance amplifier (OTA). The proposed inductance simulator can be tuned electronically by changing the biasing current of the DO-CCCIIs or by changing the current of the OTA. Moreover, the circuit does not require any conditions of component matching. It has a good sensitivity performance with respect to tracking errors. As an application, the proposed inductance simulator is used to construct a fourth-order resistively terminated LC band-pass filter. The theoretical analysis is verified by the SPICE simulation results. 相似文献
47.
Muhammed A. Ibrahim Shahram Minaei Erkan Yuce 《International Journal of Circuit Theory and Applications》2012,40(5):477-488
In this paper, two new circuit configurations for realizing voltage‐mode (VM) all‐pass sections (APSs) are presented. The proposed circuits employ only two differential voltage current conveyors (DVCCs) and are cascadable with other VM circuits due to their high‐input and low‐output impedances. The first configuration uses a grounded resistor and a grounded capacitor without requiring matching constraints, whereas the second employs two grounded resistors and a grounded capacitor with a single matching condition. While the first configuration can realize only one all‐pass response, the second can provide inverting and non‐inverting all‐pass responses with selection of appropriate input port. Adding two grounded resistors to the proposed filters, variable gain APSs can also be obtained. As applications, two quadrature oscillators, each of which using one of the proposed all‐pass circuits, one grounded resistor and one grounded capacitor are presented. SPICE simulation results are included to verify the theory. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
48.
Muhammed Muhsin Varikkodan Chun-Chung Chen Tzong-Yuan Wu 《International journal of molecular sciences》2021,22(15)
Chikungunya virus (CHIKV) is a mosquito-transmitted infectious agent that causes an endemic or epidemic outbreak(s) of Chikungunya fever that is reported in almost all countries. This virus is an intense global threat, due to its high rate of contagion and the lack of effective remedies. In this study, we developed two baculovirus expression vector system (BEVS)-based approaches for the screening of anti-CHIKV drugs in Spodoptera frugiperda insect (Sf21) cells and U-2OS cells. First, structural protein of CHIKV was co-expressed through BEVS and thereby induced cell fusion in Sf21 cells. We used an internal ribosome entry site (IRES) to co-express the green fluorescent protein (EGFP) for identifying these fusion events. The EGFP-positive Sf21 cells fused with each other and with uninfected cells to form syncytia. We identified that ursolic acid has potential anti-CHIKV activity in vitro, by using this approach. Second, BacMam virus-based gene delivery has been successfully applied for the transient expression of non-structural proteins with a subgenomic promoter-EGFP (SP-EGFP) cassette in U-2OS cells to act as an in vitro CHIKV replicon system. Our BacMam-based screening system has identified that the potential effects of baicalin and baicalein phytocompounds can inhibit the replicon activity of CHIKV in U-2OS cells. In conclusion, our results suggested that BEVS can be a potential tool for screening drugs against CHIKV. 相似文献
49.
50.
The objective of this research was to investigate and compare the effect of different treatments including gaseous ozone (6-ppm/4-min), ultrasound (450 W/4 min) and coating of shellac, lysozyme–chitosan (L-C) on fresh eggs internal quality during storage for six weeks at ambient temperature. The internal quality attributes such as weight loss (WL), albumen viscosity, Haugh unit (HU), yolk index, total soluble solids, albumen and yolk's pH were monitored. Control groups had the worst HU (50.04), WL (8.35%), albumen pH (9.27) and viscosity (7.72 mPa·s) values after storage. The best interior qualities were obtained by shellac coating [HU (72.37), WL (1.37) and viscosity (30.10 mPa·s)] and sonication (albumen pH: 8.22). Thus, the shellac-coated eggs maintained all the internal quality parameters at the highest values, while the ozone and ultrasound only helped to keep the internal quality and enhance the shelf life of eggs. 相似文献