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101.
A monolithic white light-emitting diode (LED) with blue and yellow light active regions has been de-signed and studied. With the AlxGa1-xN/InyGa1-yN distributed Bragg reflector (DBR) resonant-cavity, the extraction efficiency and power of the yellow light are enhanced so that high quality white light can be obtained. 相似文献
102.
基于极化分解的抗角反射器干扰研究 总被引:2,自引:0,他引:2
角反射器干扰是舰船应对反舰导弹的一种重要无源干扰形式,为了提高反舰导弹的作战效能,利用目标宽带条件下极化分解比重邻频差异的统计特性,将Krogager极化分解算法用于舰船和角反射器阵列的鉴别。该算法采用双门限的设定,不仅可以判别待识别模式极化分解在频率上的稳定性,而且可以进一步判别在姿态上的稳定性。结果表明角反射器阵列的极化分解比重不仅随频率变化具有稳定性,并且随角反射器个数的变化也具有稳定性,而舰船的极化分解比重随频率的变化具有敏感性,达到较好的鉴别效果。 相似文献
103.
104.
《International Journal of Hydrogen Energy》2019,44(5):2519-2532
Hydrogen production can be achieved via combined concentrated photovoltaic (CPV) and concentrated solar power (CSP) in which concentrated radiation is spectrally split and then converted in a photovoltaic receiver and a thermal absorber. This study thus proposes an innovative solar process design integrating both thermal and quantum components of solar energy while providing a complete assessment of its global performance to demonstrate its practical interest. A stand-alone solar-to-hydrogen path was modeled and numerically simulated, which was both electrically and thermally supplied by a solar power generation unit to feed the electrolyzer power utilization unit with enhanced solar-to-hydrogen conversion efficiency. Following balance of plant (BoP), the heliostat field and cavity receiver were designed to match the entire system in which the receiver only intercepts a definite range of infrared wavelength while the rest is converted by separately insulated PV cells. Moreover, dichroic reflectors and optimum cutoff wavelength were applied to fulfill separate optimization and heat load reduction of each solar cell. Finally, the solid oxide electrolysis cell (SOEC) was designed to utilize the generated thermal and electrical power appropriately. In best case scenario, a solar-to-hydrogen conversion efficiency of 36.5% was achieved under 899 W/m2 direct normal irradiance (DNI) and 1000 suns concentration. The solar plant outputs at this operating point were 850 g/h H2 and 6754 g/h O2. Further improvement in efficiency can be achieved through alignment in regard to the site location and annual insolation variation. 相似文献
105.
设计了一款用于脑活动探测的超宽带定向天线。该天线采用了平面菱形单极天线的宽频带特性,通过缺陷地结构实现小型化。为了增强天线的定向辐射能力,设计了一种花瓣形谐振式反射器,在较宽频带内产生同相反射,并可减少剖面高度至0.1λ0。该天线整体结构具有尺寸小、重量轻的特点。对天线结构进行仿真优化并加工实测,测试结果与仿真的一致性表明了该天线具有超宽带的特点,实测阻抗带宽为0.91~2.42 GHz(91%),且远场方向图表明了天线具有良好的定向性能,因而该天线可以应用于人脑活动探测等领域。 相似文献
106.
This article presents two designs of matched feed for an offset fed reflector. Circular microstrip patch antennas are used in the proposed designs. Both the matched feeds achieve conjugate field matching by generating TM21 mode at an appropriate ratio to the fundamental TM11 mode. The first matched feed generates the required dual mode field distributions using a dual layer stacked patch antenna. The second matched feed is a novel design using centered circular array with the central element generating the required TM21 mode and the surrounding circular ring antenna elements operating in the TM11 mode. Both the designs are studied analytically using cavity model and are implemented in High frequency System Simulator (HFSS) and Computer Simulation Technology (CST). The matched feed designs are investigated for an offset reflector with the projected diameter, D = 50λ, focal length, F = 30λ and clearance height, H = 5λ operating at 20 GHz. The secondary field patterns of the offset reflector fed by the matched feeds are evaluated numerically using a MATLAB code based on geometrical optics technique and verified by HFSS‐PO results. Offset reflector performance such as cross‐polarization, ?30 dB cross‐polar bandwidth, gain, and first side‐lobe level are investigated for the both matched feeds. 相似文献
107.
Caroline Murawski Andreas Mischok Jonathan Booth Jothi Dinesh Kumar Emily Archer Laura Tropf Chang‐Min Keum Ya‐Li Deng Kou Yoshida Ifor D. W. Samuel Marcel Schubert Stefan R. Pulver Malte C. Gather 《Advanced materials (Deerfield Beach, Fla.)》2019,31(42)
Fluorescence imaging is an indispensable tool in biology, with applications ranging from single‐cell to whole‐animal studies and with live mapping of neuronal activity currently receiving particular attention. To enable fluorescence imaging at cellular scale in freely moving animals, miniaturized microscopes and lensless imagers are developed that can be implanted in a minimally invasive fashion; but the rigidity, size, and potential toxicity of the involved light sources remain a challenge. Here, narrowband organic light‐emitting diodes (OLEDs) are developed and used for fluorescence imaging of live cells and for mapping of neuronal activity in Drosophila melanogaster via genetically encoded Ca2+ indicators. In order to avoid spectral overlap with fluorescence from the sample, distributed Bragg reflectors are integrated onto the OLEDs to block their long‐wavelength emission tail, which enables an image contrast comparable to conventional, much bulkier mercury light sources. As OLEDs can be fabricated on mechanically flexible substrates and structured into arrays of cell‐sized pixels, this work opens a new pathway for the development of implantable light sources that enable functional imaging and sensing in freely moving animals. 相似文献
108.
八木天线实现超宽带和高增益的关键分别是展宽馈源带宽、增加引向器数量或提高馈源增益。基于上述思路,采用U 形管折合振子馈源、管内塞入同轴电缆变换段,在两管中间增加一个平行寄生导体片;将引向器增加至20个并优化它们的直径、长度和间距;最后,在馈源振子和反射板之间增加一根导体反射器。运用上述创新方法,八木天线实现了超宽带工作,带宽达到46.3%(1.36-2.18 GHz,VSWR£2.0),增益高达17.16 dBi,前后比大于17 dB,效率大于90%, 性能显著提升,将使八木天线应用领域进一步扩展。 相似文献
109.
110.
A high gain dual-band printed antenna is proposed for LTE base stations applications. The established 60 × 60 mm2 broadband antenna structure is composed of two perpendicular U-shaped and L-shaped monopole antennas which are located vertically on ground plane printed on 1.6 mm thick FR4 substrate. A metallized wall is connected to the substrate which forms a corner reflector. A coaxial cable at the common center of the monopoles is adopted to excite the antenna. Wise implementation of the conductive elements and finely tuning of the monopoles dimensions yield the excitation of two resonances and dual band operation achievement. The presented antenna achieves bandwidths of 1.61–1.86 GHz and 2.25–2.45 GHz suitable for LTE applications. Stable radiation pattern, small size, cost effective fabrication, and high peak gain values of 10 dBi and 9.5 dBi at two operating bands are the prominent features of the proposed antenna topology. 相似文献