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   8474篇
  免费   781篇
  国内免费   179篇
电工技术   557篇
综合类   240篇
化学工业   1672篇
金属工艺   336篇
机械仪表   576篇
建筑科学   723篇
矿业工程   339篇
能源动力   283篇
轻工业   646篇
水利工程   124篇
石油天然气   432篇
武器工业   31篇
无线电   812篇
一般工业技术   1138篇
冶金工业   328篇
原子能技术   34篇
自动化技术   1163篇
  2024年   53篇
  2023年   201篇
  2022年   284篇
  2021年   454篇
  2020年   343篇
  2019年   331篇
  2018年   394篇
  2017年   397篇
  2016年   314篇
  2015年   414篇
  2014年   589篇
  2013年   696篇
  2012年   772篇
  2011年   778篇
  2010年   670篇
  2009年   548篇
  2008年   511篇
  2007年   445篇
  2006年   482篇
  2005年   355篇
  2004年   163篇
  2003年   110篇
  2002年   58篇
  2001年   22篇
  2000年   20篇
  1999年   12篇
  1998年   4篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1986年   2篇
  1985年   2篇
  1979年   2篇
排序方式: 共有9434条查询结果,搜索用时 0 毫秒
31.
Comprehensive study on novel Linear-Dispersion Division Multiple-Access(LDDMA) for multi-user uplink Multiple-Input Multiple-Output(MIMO)systems is proposed.In the new multiplexing scheme,each user’s information symbol is dispersed by a User-Specific Matrix(USM)both in space and time domain and linearly combined at base-station side.And a simple random search algorithm,based on capacity maximization criteria,is developed to generate a bank of USMs.Simulation results are presented to demonstrate the advantages of LDDMA.When the Bit Error Rate(BER) reaches 10^–3,the performance gains are 3dB and 5dB,compared with Time-Division Linear Dispersion Codes(TD-LDC)and BLAST,respectively.  相似文献   
32.
论文根据小型无人直升机的机理建立了数学模型,并在悬停状态下近似线性化,运用Matlab的非线性控制工具箱(NCD)设计了具有很强鲁棒性的控制器,实现了对于小型无人直升机的纵向和横向的解耦控制,仿真结果证明了方法的有效性。  相似文献   
33.
主要介绍用VB实现无线通信的软件设计。并且提出了使系统应用程序更有效和可靠的方法。  相似文献   
34.
基于LabVIEW串口通信的研究   总被引:10,自引:2,他引:10  
LabVIEW是NI公司开发的图形化编程开发平台,具备强大的实时数据处理功能与显示功能。通常情况下,在Lab—VIEW开发环境中进行串口通信使用VISA和ActiveX控件两种方式均可以进行,通过结合实例比较,发现VISA方式只能提供查询缓冲区方式接收数据,这需要占用大量的CPU时间,且实时性不佳。相对而言,使用微软提供的MSCOMM32控件的中断函数处理功能,可以实现中断方式的接收数据。同时,MSCOMM32控件可以单独设置串口的每一个引脚,便于实现高级的用户自定义功能。  相似文献   
35.
Practical applications of lithium-ion batteries(LIBs) with both high energy and power density are urgently demanded,which require suitable charge/discharge platform,fast charge-transfer kinetics,as well as optimal solid electrolyte interphase(SEI) layer of electrode materials.In this work,a high-performance lithium-ion battery(LIB) full cell was assembled by using commercial LiNi_(0.33)Co_(0.33)Mn_(0.33)O_2(NCM111) as the positive electrode and mixed Li_4 Li_5 O_(12)(LTO)/hard carbon(HC) as the negative electrode.It reveals that the component ratio between LTO and HC plays a critical role in manipulating the electric conductivity and the electro-reaction platform.The electrochemical test results show that when the content of HC is 10 wt%,the as-constructed full cell demonstrates the best electrochemical,with a maximum energy density of 149.2 Wh·kg~(-1) and a maximum power density of2195 W·kg~(-1) at 10 A·g~(-1)(30 C).This outperforms all the assembled systems within our work range and the state-ofthe-art literatures.The NCM//Li_4 Ti_5 O_(12)+10 wt% HC battery system also exhibits a good capacity retention after1000 cycles at the current density of 1 A·g~(-1).This work provides a new approach to enhance the full-cell performance by mixing electrode materials with different charge potentials and reaction kinetics.  相似文献   
36.
Excessive input of nitrogen fertilizer not only causes a great waste of resources but brings about a series of ecological and environmental problems. Although Small Auxin Up-regulated RNAs (SAURs) participate in diverse biological processes, the function of SAURs in the nitrogen starvation response has not been well-studied. Here, we identified 308 TaSAURs in wheat and divided them into 10 subfamilies. The promoter regions of most TaSAURs contain hormone responsive elements, and their expression levels change under the treatment of different hormones, such as IAA, MeJA, and ABA. Interestingly, overexpression of one of the TaSAUR family members, a nitrogen starvation responsive gene, TaSAUR66-5B, can promote the growth of Arabidopsis and wheat roots. In addition, overexpression of TaSAUR66-5B in Arabidopsis up-regulates the expression levels of auxin biosynthesis related genes, suggesting that overexpression TaSAUR66-5B may promote root growth by increasing the biosynthesis of auxin. Furthermore, overexpression of TaSAUR66-5B in wheat can increase the biomass and grain yields of transgenic plants, as well as the nitrogen concentration and accumulation of both shoots and grains, especially under low nitrogen conditions. This study provides important genomic information of the TaSAUR gene family and lays a foundation for elucidating the functions of TaSAURs in improving nitrogen utilization efficiency in wheat.  相似文献   
37.
首先分析了电路板的常用制作方法,然后介绍了一种既能减少污染,又能保证加工精度与效率的基于物理雕刻的电路板雕刻机系统.主要对电路板雕刻过程中的刀路生成作了详细论述,并在采用环切与行切相结合的加工方法的基础上,提出了一种基于电路板雕刻的行切刀路规划算法,最后用VC 编写了相应的程序,经程序验证此算法准确可靠,能够满足电路板的加工要求.  相似文献   
38.
As one of the most important factors in alternative splicing (AS) events, serine/arginine-rich (SR) proteins not only participate in the growth and development of plants but also play pivotal roles in abiotic stresses. However, the research about SR proteins in cotton is still lacking. In this study, we performed an extensive comparative analysis of SR proteins and determined their phylogeny in the plant lineage. A total of 169 SR family members were identified from four Gossypium species, and these genes could be divided into eight distinct subfamilies. The domain, motif distribution and gene structure of cotton SR proteins are conserved within each subfamily. The expansion of SR genes is mainly contributed by WGD and allopolyploidization events in cotton. The selection pressure analysis showed that all the paralogous gene pairs were under purifying selection pressure. Many cis-elements responding to abiotic stress and phytohormones were identified in the upstream sequences of the GhSR genes. Expression profiling suggested that some GhSR genes may involve in the pathways of plant resistance to abiotic stresses. The WGCNA analysis showed that GhSCL-8 co-expressed with many abiotic responding related genes in a salt-responding network. The Y2H assays showed that GhSCL-8 could interact with GhSRs in other subfamilies. The subcellular location analysis showed that GhSCL-8 is expressed in the nucleus. The further VIGS assays showed that the silencing of GhSCL-8 could decrease salt tolerance in cotton. These results expand our knowledge of the evolution of the SR gene family in plants, and they will also contribute to the elucidation of the biological functions of SR genes in the future.  相似文献   
39.
Drought stress is an important factor that severely affects crop yield and quality. Autophagy has a crucial role in the responses to abiotic stresses. In this study, we explore TaNBR1 in response to drought stress. Expression of the TaNBR1 gene was strongly induced by NaCl, PEG, and abscisic acid treatments. The TaNBR1 protein is localized in the Golgi apparatus and autophagosome. Transgenic Arabidopsis plants overexpressing TaNBR1 exhibited reduced drought tolerance. When subjected to drought stress, compared to the wild-type (WT) lines, the transgenic overexpressing TaNBR1 plants had a lower seed germination rate, relative water content, proline content, and reduced accumulation of antioxidant enzymes, i.e., superoxide dismutase, peroxidase, and catalase, as well as higher chlorophyll losses, malondialdehyde contents, and water loss. The transgenic plants overexpressing TaNBR1 produced much shorter roots in response to mannitol stress, in comparison to the WT plants, and they exhibited greater sensitivity to abscisic acid treatment. The expression levels of the genes related to stress in the transgenic plants were affected in response to drought stress. Our results indicate that TaNBR1 negatively regulates drought stress responses by affecting the expression of stress-related genes in Arabidopsis.  相似文献   
40.
张晓艳  张宝华  吕晓琪  谷宇  王月明  刘新  任彦  李建军 《光电工程》2021,48(5):200388-1-200388-9
在行人重识别任务中存在数据集标注难度大,样本量少,特征提取后细节特征缺失等问题。针对以上问题提出深度双重注意力的生成与判别联合学习的行人重识别。首先,构建联合学习框架,将判别模块嵌入生成模块,实现图像生成和判别端到端的训练,及时将生成图像反馈给判别模块,同时优化生成模块与判别模块。其次,通过相邻的通道注意力模块间连接和相邻空间注意力模块间连接,融合所有通道特征和空间特征,构建深度双重注意力模块,将其嵌入教师模型,使模型能更好地提取行人细节身份特征,提高模型识别能力。实验结果表明,该算法在Market-1501和DukeMTMC-ReID数据集上具有较好的鲁棒性、判别性。  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