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1.
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO4) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σg, less than 1.43 when the total volumetric flow rate Qtotal was larger than 10 ml/min. By selecting Qtotal and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σg = 1.22) could be achieved at Qtotal of 160 ml/min.  相似文献   
2.
Tracking-by-detection (TBD) is a significant framework for visual object tracking. However, current trackers are usually updated online based on random sampling with a probability distribution. The performance of the learning-based TBD trackers is limited by the lack of discriminative features, especially when the background is full of semantic distractors. We propose an attention-driven data augmentation method, in which a residual attention mechanism is integrated into the TBD tracking network as supplementary references to identify discriminative image features. A mask generating network is used to simulate changes in target appearances to obtain positive samples, where attention information and image features are combined to identify discriminative features. In addition, we propose a method for mining hard negative samples, which searches for semantic distractors with the response of the attention module. The experiments on the OTB2015, UAV123, and LaSOT benchmarks show that this method achieves competitive performance in terms of accuracy and robustness.  相似文献   
3.
建立车辆动力学模型,研究车辆在高速避让工况下的路径跟踪控制策略。基于自抗扰控制设计车辆横摆角速度以及道路曲率2种不同的路径跟踪控制器;设计基于车辆偏航位移和偏航角度加权的线性二次最优控制器;对3种控制器控制效果进行仿真验证,分析路径跟踪侧向位移误差、侧向加速度、前轮转向角以及偏航角度变化。越野车实车测试结果表明,路径跟踪控制策略正确。  相似文献   
4.
陈玲  李洁 《计算机仿真》2020,(4):347-351
现阶段所采用的跟踪方法对后继帧视频图像目标跟踪存在跟踪效果不理想、跟踪效率较低等问题。提出基于视觉传达的后继帧视频图像目标跟踪方法。利用图像差分方法获取视频图像运动目标可能出现的区域,并对这个区域视频图像目标进行运动估计,采用形态学方法来降低聚类区域的数量,得到后继帧视频图像目标区域;采用均值漂移法估计后继帧视图像核概率密度,对后继帧视频图像进行分割处理,找出后继帧视频图像目标区域最显著的特征,通过迭代运算找到目标位置,实现目标跟踪。实验结果表明,所提算法具有较好的后继帧视频图像跟踪效果、并且跟踪效率较高,具有一定的应用价值。  相似文献   
5.
This paper presents a novel approach to the localization of moving targets in a complex environment based on the measurement of the perturbations induced by the target presence on an independently‐generated time‐varying electromagnetic field. Field perturbations are measured via a set of sensors deployed over the domain of interest and used to detect and track a possible target by resorting to a particle Bernoulli filter (PBF). To comply with real‐time operation, the PBF works along with an artificial neural network (ANN) model of the environment trained offline via finite elements (FEs). The performance of the proposed algorithm is assessed via simulation experiments.  相似文献   
6.
The effects of titanium ion implantation on the stress corrosion cracking (SCC) behaviour of 304 austenitic stainless steel were studied. Slow strain rate tests (SSRTs) were conducted on 304 steel in air and in 5?wt-% NaCl solution. The microscopic effects of ion implantation were evaluated by Stopping and Range of Ions in Matter Procedures (SRIM). Fracture morphologies and microstructures were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The fracture surfaces illustrate that ion implantation significantly inhibits the corrosion pits that initiate SCC. A dense passive film, which inhibits SCC, was formed during the ion implantation process. SCC initiation was restrained due to the dense dislocation nets that were generated by titanium ion implantation.

Highlights
  • Ion implantation inhibits SCC susceptibility.

  • The lack of Cr at the grain boundary leads to the expansion of SCC along the grain boundary.

  • Implantation-induced damage leads to high-density dislocations.

  • The surface was amorphised due to high-density dislocations.

  相似文献   
7.
针对船载卫星通信三轴天线跟踪系统,介绍了船载三轴天线的系统组成,提出了一种基于捷联惯导的船载三轴天线跟踪搜索技术。天线以目标地理角为中心,通过坐标转换将目标地理角转换为天线的目标甲板角,调整AEC三轴使其及时准确地跟随目标甲板角。目前,该方法已经成功应用于多种船载三轴天线。实践表明,该方法能够快速准确地搜索到目标卫星,并实现对目标卫星的稳定跟踪。  相似文献   
8.
Aircraft accident investigation has played a pivotal role in improving the safety of aviation. Advances in recorder technology, specifically Cockpit Voice Recorders (CVRs) and Flight Data Recorders (FDR) have made a huge contribution to the understanding of occurrences for accident investigators. However, even these recorders have limitations such as the evidence they provide about pilots' situation awareness or behaviours. Supplementing audio and data recordings with video has been discussed for many years and whilst there continues to be debate among regulators, operators, manufacturers and pilot unions, the International Civil Aviation Organization (ICAO) has mandated Airborne Image Recorders (AIR) from 2023. The purpose of installing such systems is to provide evidence of crew operational behaviours in terms of both human-human and human-computer interactions (HCI) on the flight deck. Video alone is unlikely to provide sufficient evidence for investigators. This study examines the additional value that eye-tracking technology may provide through the case study of an accident involving an Airbus A330-300 aircraft which experienced a rejected landing. Currently, the investigation of such events, where crew interaction with automation is critical to their situation awareness, relies heavily on interview data. Such data may be unavailable (in the case of serious injury) or unreliable (based on hindsight bias). By integrating eye tracking technology into an AIR, accident investigators will potentially gain a better understanding of pilots’ visual scan patterns across flight deck instrumentation. This has implications for flight deck and procedural design as well as training and simulation.  相似文献   
9.
白明 《中州煤炭》2018,(3):86-90
目前在定向钻进过程中,往往因没有更好地开展工程实施跟踪与工程设计预测控制技术,导致后续施工出现偏差,钻进成本和钻井施工难度增大。为此,根据定向钻进设计原理,采用最小二乘法求出修正系数,运用轨迹预测模型,开展了定向钻进随钻跟踪设计与控制技术的研究。采用常用的Excel编制程序,输入实钻数据后,自动分析出后续定向轨迹设计。做到随时输入随时预测,可有效防止定向偏差。经现场应用,可有效快速预测后续定向钻进参数,及时指导后续定向钻进工作,减少工程失误风险。  相似文献   
10.
目的 调查评估GB 7718—2011《食品安全国家标准 预包装食品标签通则》、GB 28050—2011《食品安全国家标准 预包装食品营养标签通则》、GB 13432—2013《食品安全国家标准 预包装特殊膳食食用食品标签》在陕西省的执行情况,为标准的修订完善提供依据。方法 采用横断面调查法,于2017年5~10月对陕西省食品相关生产企业人员、监管人员、检验人员及科研人员通过会议现场发放问卷、微信网络问卷的方式进行调查。调查内容包含调查对象基本信息、对标准的知晓情况及合理性和可操作性评价、对标准的技术性评价情况及遇到的主要问题、修改意见和建议。结果 本次调查共发放问卷310份,收回有效问卷305份;4类人员对GB 7718—2011、GB 28050—2011、GB 13432—2013的总知晓率分别为76.1%(86/113)、73.5%(83/113)、64.6%(51/79);分别有90.7%(78/86)、84.3%(70/83)、78.4%(40/51)的调查对象认为GB 7718—2011、GB 28050—2011、GB 13432—2013基本合理;部分调查对象提出一些关于标准细节的建议。结论 陕西省食品相关工作人员对GB 7718—2011和GB 28050—2011的知晓率较高,对GB 13432—2013的知晓率与前2个标准相比较低。本次调查还观察到调查对象对标准的内容理解不够充分,执行情况仍然存在应用推广不够的情况。标准在应用过程中还存在问题,现行标准有待改进。  相似文献   
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