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991.
Poly(ethylene-co-methacrylic acid) (EMAA) as a thermally activated healing agent in a high performance, high temperature tetra-glycidyl methylene dianiline (TGDDM)/diethyl toluene diamine (DETDA) mendable epoxy composite is reported for the first time. Despite curing above EMAAs melting point (Tm = 85 °C), healing occurred by incorporating a preliminary low temperature curing step of 5 h at 80 °C, prior to cure at 177 °C. Healing occurred via the pressure delivery mechanism derived from tertiary amine catalysed surface condensation reactions between EMAA and hydroxyl groups from the epoxy resin. Healing efficiencies of 36%, 55% and 105% were achieved after heating at 150 °C, 200 °C and 230 °C respectively, but decreased rapidly with continued healing. Healing at 150 °C and 200 °C revealed significant healing despite remaining in the glassy state. In addition, EMAA enhanced mode I interlaminar fracture toughness by more than 270% for both the DETDA and 4,4-DDS networks. 相似文献
992.
采用逐次逼近方式设计了一个12位的超低功耗模数转换电路。为减小整个ADC的芯片面积、功耗和误差,提高有效位数,对整个ADC的采样保持电路结构进行了精确的设计,重点考虑了其中的高精度比较器电路结构;对以上两个模块的版图设计进行了精细的布局。采用0.18μmCMOS工艺,该ADC的信噪比(SNR)为72dB,有效位数(ENOB)为11.7位,该ADC的芯片面积只有0.36mm2,典型的功耗仅为40μW,微分非线性误差DNL小到0.6LSB、积分非线性误差INL只有0.63LSB。整个ADC性能达到设计要求。 相似文献
993.
采用7级子ADC流水线结构设计了一个8位80MS/s的低功耗模数转换电路。为减小整个ADC的芯片面积和功耗,改善其谐波失真和噪声特性,重点考虑了第一级子ADC中MDAC的设计,将整个ADC的采样保持电路集成在第一级子ADC的MDAC中,并且采用逐级缩放技术设计7级子ADC的电路结构,在版图设计中考虑每一级子ADC中的电容及放大器的对称性。采用0.18μm CMOS工艺,该ADC的信噪比(SNR)为53dB,有效位数(ENOB)为7.98位,该ADC的芯片面积只有0.56mm2,典型的功耗电流仅为22mA。整个ADC性能达到设计要求。 相似文献
994.
分析了功率因数偏低的原因,主要原因有原有低压无功补偿装置设计不合理,器件出现故障,不能提供系统所需的无功补偿功率。通过实例给出了无功补偿装置改造的具体做法,如加装电抗器,选用耐压等级合适的电容器,采用无功补偿装置专用交流接触器,并合理规划了无功补偿柜内散热通道。最后对改造前后的经济效益进行了分析。 相似文献
995.
996.
随着中国移动数据业务迅速发展,中国移动各地数据机房将陆续建设,如何合理设置机房供电系统,对节能、节地都起着至关重要的作用。本文结合新技术的应用,提出了一种靠、高效、灵活的数据中心机房供电解决方案。 相似文献
997.
The influence of high energy electron (HEE) irradiation from a Sr-90 radio-nuclide on n-type Ni/4H–SiC samples of doping density 7.1×1015 cm−3 has been investigated over the temperature range 40–300 K. Current–voltage (I–V), capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS) were used to characterize the devices before and after irradiation at a fluence of 6×1014 electrons-cm−2. For both devices, the I–V characteristics were well described by thermionic emission (TE) in the temperature range 120–300 K, but deviated from TE theory at temperature below 120 K. The current flowing through the interface at a bias of 2.0 V from pure thermionic emission to thermionic field emission within the depletion region with the free carrier concentrations of the devices decreased from 7.8×1015 to 6.8×1015 cm−3 after HEE irradiation. The modified Richardson constants were determined from the Gaussian distribution of the barrier height across the contact and found to be 133 and 163 A cm−2 K−2 for as-deposited and irradiated diodes, respectively. Three new defects with energies 0.22, 0.40 and 0.71 eV appeared after HEE irradiation. Richardson constants were significantly less than the theoretical value which was ascribed to a small active device area. 相似文献
998.
Two new conjugated D–A polymers P3 (PBTT-d-BTT) and P4 (PBTT-d-TPD) based on same benzo[1,2-b:3,4-b′:6,5-b″] trithiophene (BTT) donor and different acceptors monomers 5,8-dibromo-2-dodecanoylbenzo[1,2-b:3,4-b′:6,5-b″] trithiophene (d-BTT), and 1,3-dibromo-5-(2-ethylhexyl)thieno[3,4]pyrrol-4,6-dione (d-TPD) respectively, were synthesized by Stille cross-coupling reaction and characterized by gel permeation chromatography (GPC), 1H NMR, UV–Vis absorption, thermal analysis and electrochemical cyclic voltammetry (CV) tests. Photovoltaic properties of the polymers were studied by using the polymers as donor and PC71BM as acceptor with a weight ratio of polymer:PC71BM 1:1, 1:2 and 1:2.5. The optimized photovoltaic device was fabricated with an active layer of a blend P3:PC71BM and P4:PC71BM with a blend ratio of 1:2 showed PCE 3.16% and 2.42%, respectively under illumination of AM 1.5 at 100 mW/cm2 with solar simulator. The PCE of the device based on P3:PC71BM processed with DIO/o-DCB has been further improved up to 4.64% with Jsc of 10.52 mA/cm2 and FF of 0.58 attributed to the increase in crystalline nature of active layer and more balanced charge transport in the device, induced by DIO additive. 相似文献
999.
《材料与设计》2015
The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature. 相似文献
1000.
AbstractThe plastic deformation of a high entropy alloy Al0.5CoCrFeNi was investigated by instrumented nanoindentation over a broad range of strain rates at room temperature. Results show that the creep behaviour depends on the strain rate remarkably. In situ scanning images showed a significant pile up around the indents, demonstrating that a highly localised plastic deformation occurred in the process of nanoindentation. Under different strain rates, contact stiffness and elastic modulus basically remain unchanged. However, the hardness decreases as indentation depth increases due to indentation size effect. For the same maximum load, serrations became less prominent as the loading rate of indentation increased. Similar serrations have been observed in the current alloy upon quasi-static compression. 相似文献