首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   77209篇
  免费   6394篇
  国内免费   3980篇
电工技术   5732篇
技术理论   1篇
综合类   7066篇
化学工业   3701篇
金属工艺   6922篇
机械仪表   12922篇
建筑科学   8303篇
矿业工程   3242篇
能源动力   1388篇
轻工业   4369篇
水利工程   1577篇
石油天然气   3081篇
武器工业   746篇
无线电   4760篇
一般工业技术   6368篇
冶金工业   3174篇
原子能技术   332篇
自动化技术   13899篇
  2024年   179篇
  2023年   1110篇
  2022年   1953篇
  2021年   2353篇
  2020年   2390篇
  2019年   1796篇
  2018年   1677篇
  2017年   2171篇
  2016年   2522篇
  2015年   2980篇
  2014年   4805篇
  2013年   3919篇
  2012年   5669篇
  2011年   5889篇
  2010年   4443篇
  2009年   4543篇
  2008年   4194篇
  2007年   5345篇
  2006年   4994篇
  2005年   4325篇
  2004年   3369篇
  2003年   2991篇
  2002年   2624篇
  2001年   2249篇
  2000年   1819篇
  1999年   1464篇
  1998年   1178篇
  1997年   911篇
  1996年   769篇
  1995年   641篇
  1994年   526篇
  1993年   359篇
  1992年   275篇
  1991年   207篇
  1990年   189篇
  1989年   156篇
  1988年   121篇
  1987年   61篇
  1986年   49篇
  1985年   45篇
  1984年   37篇
  1983年   50篇
  1982年   50篇
  1981年   14篇
  1980年   21篇
  1979年   19篇
  1978年   14篇
  1965年   17篇
  1962年   9篇
  1959年   9篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
1.
2.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。  相似文献   
3.
In actual engineering scenarios, limited fault data leads to insufficient model training and over-fitting, which negatively affects the diagnostic performance of intelligent diagnostic models. To solve the problem, this paper proposes a variational information constrained generative adversarial network (VICGAN) for effective machine fault diagnosis. Firstly, by incorporating the encoder into the discriminator to map the deep features, an improved generative adversarial network with stronger data synthesis capability is established. Secondly, to promote the stable training of the model and guarantee better convergence, a variational information constraint technique is utilized, which constrains the input signals and deep features of the discriminator using the information bottleneck method. In addition, a representation matching module is added to impose restrictions on the generator, avoiding the mode collapse problem and boosting the sample diversity. Two rolling bearing datasets are utilized to verify the effectiveness and stability of the presented network, which demonstrates that the presented network has an admirable ability in processing fault diagnosis with few samples, and performs better than state-of-the-art approaches.  相似文献   
4.
在传统的轮胎表面缺陷依靠人工检测,存在劳动强度高、受人的主观影响大以及效率低下的问题。针对这一现象,研究了一种基于机器视觉的轮胎表面缺陷3D检测系统。该系统依靠机器视觉系统获取检测轮胎的表面图像,然后创建3D模型、判定缺陷类型,最终实现实时自动预警,为轮胎生产商提供一种自动化检测方案。系统集成了先进的技术、软件和工具,配套的信息管控系统可以对轮胎型号和生产数据进行采集、存储、分析,以便在生产过程中实现更高效、更可靠的质量控制,具有较高的实际应用推广价值。  相似文献   
5.
现阶段,为了探索创新性的发展途径,生态环境监测机构应始终增强风险控制意识。应加强风险管理,立足于风险控制,以求不断健康发展。  相似文献   
6.
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM.  相似文献   
7.
核桃不仅营养价值极高,而且核桃壳的药用价值也非常高,国内小企业和家庭在核桃硬壳脱壳加工环节,一般采用人工破壳取仁的方式,这种方式劳动强度大,人工成本高且不卫生;针对这个问题设计了一款小型的硬壳脱壳,壳仁分离分选的机器来提高生产效率,减少成本,提高收入。  相似文献   
8.
为了降低机床等待过程中的能耗,提出了一种实时数据驱动的机床等待时间预测与节能控制方法。首先,建立了射频识别驱动的生产进度评估方法,并以生产进度数据作为输入,构建了基于堆栈降噪自编码的机床等待时间预测模型;其次,依据预测的机床等待时间,提出了机床状态切换方法,以降低机床能耗;最后,通过一个电梯零部件制造车间的案例分析,表明该方法的预测误差仅为4.1%,同时将机床等待过程能耗降低了57%,实现了制造车间的节能减排。  相似文献   
9.
Acoustic emission (AE) during tensile testing of three-dimensional woven SiC/SiC composites was analyzed by a statistical modeling method based on a Bayesian approach to quantitatively evaluate the fracture process. Gaussian mixture models and Weibull mixture models were utilized as candidate models describing the AE time-series data. After fitting AE time-series data to these models with Markov Chain Monte Carlo (MCMC) methods, the model selection was conducted by stochastic complexity. Among the candidate models, the two-component Weibull mixture model was automatically selected. It was confirmed that the component distributions in the two-component Weibull mixture model were corresponding to the evolution of matrix cracking and fiber breakage, respectively. Since the proposed AE analysis method can determine the number of component distributions without the decision of researchers and inspectors, it is expected to be useful for an understanding of the fracture process in newly developed materials and the reliability assessment in service.  相似文献   
10.
The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号