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不同堆置状态粗粒土剪切强度试验研究 总被引:1,自引:1,他引:0
为研究不同堆置条件下排土场粗粒土的力学响应规律, 开展了终排土体固结排水三轴压缩试验和在排土体快剪试验。研究结果表明, 土体固结排水三轴压缩应力-应变曲线呈现先弹性后屈服再弱硬化的规律, 体积-应变曲线有拐点, 低围压时先剪缩后剪胀, 高围压时以剪缩为主。在排土体快剪试验具有峰值强度, 100~400 kPa时, 峰值强度出现在剪切位移20%~30%之间, 且剪应力-位移曲线呈弱化趋势; 600~1 200 kPa时, 峰值强度出现在剪切位移30%~40%, 随剪切位移增加, 土体抗剪强度基本保持恒定或略有增大。不同堆置状态排土体抗剪强度参数取值各不相同。 相似文献
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目的改善NiCrAlY涂层微观组织并提高其力学性能。方法采用直接激光沉积方法制备100%NiCrAlY、NiCrAlY+10%Al_2O_3和Ni CrAlY+20%Al_2O_3三种样件,分别利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、X射线能量色散谱仪(EDS)、电子探针X射线显微分析仪(EPMA),对不同成分样件进行相组成分析、微观组织观察以及元素组成检测,使用维式显微硬度测试计和万能摩擦磨损试验机,分别检测各个涂层的显微硬度和摩擦系数。结果在NiCrAlY中添加Al_2O_3后,Al_2O_3以不规则形状或球形分布在晶内或者晶界处,其尺寸小于2μm。三种复合涂层样件均由γ-Ni和β-NiAl相组成,添加Al_2O_3陶瓷颗粒后,涂层一次枝晶臂间距均减小,且Ni-Y相显著减少,Y2O3陶瓷颗粒弥散分布在基体的晶内与晶界处。NiCrAlY、NiCrAlY+10%Al_2O_3和NiCrAlY+20%Al_2O_3涂层的平均硬度分别为(440.69±30)HV0.2、(482.18±30)HV0.2和(453.09±20)HV0.2,100%NiCrAlY、NiCrAlY+10%Al_2O_3和NiCrAlY+20%Al_2O_3涂层的摩擦系数分别为0.77、0.55和0.52。结论加入Al_2O_3后,基体晶粒有一定程度的细化。在晶粒细化作用以及陶瓷颗粒弥散作用下,涂层的显微硬度有所提高,其中NiCrAlY+10%Al_2O_3的硬度最高,相比NiCrAlY基体提高了约9.5%。此外,发现添加Al_2O_3后,NiCrAlY+10%Al_2O_3和NiCrAlY+20%Al_2O_3样件的摩擦系数比NiCrAlY样件下降均超过25%,其中NiCrAlY+10%Al_2O_3样件的磨损量最小,相对于NiCrAlY涂层下降了近13.5%,耐磨性明显改善。 相似文献
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An innovative negative group delay (NGD) circuit theory on unity direct chain (UDC) topology is developed in this paper. The NGD UDC cells are based on the operational amplifier adder with feedback series impedance. Innovative topologies of high-pass NGD UDC cell composed of RL-series network, all-pass RC-parallel network and low-pass RC-series network are identified. It is a first time that all-pass NGD original topologies are defined. NGD analyses and synthesis methods of each NGD UDC cells are provided. The UDC cell based NGD functions are validated with SPICE simulations. The proofs-of-concept (POC) of UDCs behave as all-pass and low-pass NGD functions with group delay equal to −1 ms at very low frequencies. The low-pass NGD cut-off frequency is 424 Hz. The high pass NGD circuit generates −1 µs at the optimal NGD frequency of about 5.15 kHz. Further analysis of the operational amplifier gain and bandwidth effects is performed. The operational amplifier gain affects significantly the NGD level and bandwidth for the all considered UDC cells. Nevertheless, only the RC-parallel feedback based UDC cell is particularly sensitive to the operational bandwidth. 相似文献
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R. S. Chaudhary C. Patel V. Sevak M. Chan 《Drug development and industrial pharmacy》2018,44(1):19-29
The study evaluates use of Kollidon VA®64 and a combination of Kollidon VA®64 with Kollidon VA®64 Fine as excipient in direct compression process of tablets. The combination of the two grades of material is evaluated for capping, lamination and excessive friability. Inter particulate void space is higher for such excipient due to the hollow structure of the Kollidon VA®64 particles. During tablet compression air remains trapped in the blend exhibiting poor compression with compromised physical properties of the tablets. Composition of Kollidon VA®64 and Kollidon VA®64 Fine is evaluated by design of experiment (DoE). A scanning electron microscopy (SEM) of two grades of Kollidon VA®64 exhibits morphological differences between coarse and fine grade. The tablet compression process is evaluated with a mix consisting of entirely Kollidon VA®64 and two mixes containing Kollidon VA®64 and Kollidon VA®64 Fine in ratio of 77:23 and 65:35. A statistical modeling on the results from the DoE trials resulted in the optimum composition for direct tablet compression as combination of Kollidon VA®64 and Kollidon VA®64 Fine in ratio of 77:23. This combination compressed with the predicted parameters based on the statistical modeling and applying main compression force between 5 and 15?kN, pre-compression force between 2 and 3?kN, feeder speed fixed at 25?rpm and compression range of 45–49?rpm produced tablets with hardness ranging between 19 and 21?kp, with no friability, capping, or lamination issue. 相似文献
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《Advanced functional materials》2018,28(35)
A photoresponsive organogel surface (POS), which integrates characteristics of the photothermal property of Fe3O4 nanoparticles and the low hysteresis feature of lubricant‐infused organogels, is shown. A photothermally induced dynamic temperature gradient can be formed rapidly at the location of near‐infrared‐light irradiation (NIR) on POS with suitable Fe3O4 nanoparticles content. Thus, various droplets (e.g., water, glycerol, ethylene glycol, propylene glycol, and ethanol) can be transported effectively and nimbly (e.g., along desired trajectories with controllable velocity and direction, even run uphill and deliver solid particles). This work reveals a synergistic effect between the asymmetrical droplet deformation and the inside Marangoni flows, which forms a unique driving force for droplet transport with high efficiency. This finding offers insight into the design of novel responsive interface materials for droplet transportation, which would be significant for laboratory‐on‐a‐chip contexts, mass transportation, and microengines. 相似文献
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