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41.
采用显微组织分析和分子动力学模拟等方法研究了退火温度对0Cr25Al5热轧态盘条钢组织及性能的影响。结果发现,晶粒尺寸随温度的升高逐渐增加并趋于稳定,但是断后伸长率和断面收缩率在950 ℃突然大幅度下降。试样组织形貌在800 ℃和950 ℃退火温度下的OM及SEM分析结果未见明显差别。于是使用分子动力学模拟对0Cr25Al5钢三元体系的自由能进行了计算,发现随着B2结构的FeAl或者DO3结构的Fe3Al有序相尺寸的增大,系统自由能先减小后增大,其最小值随着退火温度的升高向有序相颗粒尺寸减小的方向移动。在1273 K的高温下仍然会保留60 nm左右大小的有序相颗粒。因此,推测0Cr25Al5钢在大于950 ℃的温度范围内韧性下降是由于60 nm左右的B2结构的FeAl或者DO3结构的Fe3Al有序相造成,与晶粒尺寸无关。因此,针对该钢种应进行低温退火促使基体组织回复以消除缺陷,从而抑制Fe、Al等基体原子的扩散。 相似文献
42.
针对采取小批量间歇性批次生产方式、工艺介质腐蚀性强、危险性大的小型特种精细化工生产工艺研究试验过程自动化、信息化程度不高,导致工艺研究试验中获取数据较少、过程机理研究不够透彻、人工操作多、安全风险高、研究试验消耗大及效率不高等问题,综述了期待通过智能控制、在线分析、模拟仿真和虚拟制造、工况监测及预测性维护以及信息管理和生产调度等关键技术的研究和应用,提高小型特种精细化工生产工艺过程的自动化和信息化程度,实现小型特种精细化工生产工艺过程的数字化、虚拟化和智能化,降低生产安全风险和试验消耗,提高小型特种精细化工生产工艺研究试验的成功率和效率,达到小型特种精细化工生产工艺过程的数字化设计和精准生产的目标。 相似文献
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针对多泥沙水电站水轮机转轮的泥沙磨损问题,以HLA351-LJ-275水轮机为模型,对水轮机在设计工况下,运用N-S方程和标准κ-ε湍流模型,利用CFX求解器进行仿真流动模拟。水轮机转轮进口沿叶高20%、50%、80%流面的压力、泥沙速度及泥沙体积分数分布的数值结果表明,水轮机转轮叶片工作面压力大于背面且最小压力高于气化压力。泥沙速度在叶片进水边和出水口位置普遍较高。水轮机转轮叶片工作面的泥沙体积分数大于背面,叶片工作面的泥沙体积分数在叶片出水口普遍较高,叶片背面的泥沙体积分数在叶片进水边普遍较高。研究结果对多泥沙河流水轮机转轮叶片的泥沙磨损评估及维修具有指导意义。 相似文献
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Yongsen Wei 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(24):3009-3018
Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft, and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance (TCR) is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of TCR in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, inverse problem method solution is utilized as a proper method for estimation of TCR value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of TCR. A comparison between the measured values and obtained values from the simulation show the errors for flat-flat, flat-cylinder, and cylinder-cylinder configuration after 10 min from starting the experiment are 4.6074%, 0.1662%, and 0.5622%, respectively. And in steady-state condition, the corresponding errors are 6.06e-3%, 1.506%, and 0.846%, respectively. In conclusion, the final results establish the fact that the inverse problem method solution can predict TCR values between contacting surfaces. 相似文献
47.
通过矿物浮选试验、动电位测定以及吸附量测试,考察了4种淀粉抑制剂对赤铁矿和石英浮选性能的影响,并探讨了其作用机理。在碱性条件下,改性淀粉抑制剂对赤铁矿抑制效果明显,且以改性玉米淀粉效果最佳,改性磷酸酯淀粉、改性羧甲基淀粉的抑制效果次之,而普通淀粉抑制作用一般。同时4种淀粉抑制剂对主要脉石矿物石英的抑制效果均不明显。pH=10~12.5条件下,改性玉米淀粉因其羟基氧和裸露在赤铁矿表面的铁元素发生了化学键合,因而选择性抑制能力最佳。分子动力学模拟表明,改性玉米淀粉片段与赤铁矿作用更为紧密,验证了改性淀粉能更好地抑制赤铁矿。 相似文献
48.
Outcome‐based ventilation: A framework for assessing performance,health, and energy impacts to inform office building ventilation decisions 下载免费PDF全文
This article presents an outcome‐based ventilation (OBV) framework, which combines competing ventilation impacts into a monetized loss function ($/occ/h) used to inform ventilation rate decisions. The OBV framework, developed for U.S. offices, considers six outcomes of increasing ventilation: profitable outcomes realized from improvements in occupant work performance and sick leave absenteeism; health outcomes from occupant exposure to outdoor fine particles and ozone; and energy outcomes from electricity and natural gas usage. We used the literature to set low, medium, and high reference values for OBV loss function parameters, and evaluated the framework and outcome‐based ventilation rates using a simulated U.S. office stock dataset and a case study in New York City. With parameters for all outcomes set at medium values derived from literature‐based central estimates, higher ventilation rates’ profitable benefits dominated negative health and energy impacts, and the OBV framework suggested ventilation should be ≥45 L/s/occ, much higher than the baseline ~8.5 L/s/occ rate prescribed by ASHRAE 62.1. Only when combining very low parameter estimates for profitable impacts with very high ones for health and energy impacts were all outcomes on the same order. Even then, however, outcome‐based ventilation rates were often twice the baseline rate or more. 相似文献
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The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials. 相似文献