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   103653篇
  免费   19136篇
  国内免费   3174篇
电工技术   4548篇
技术理论   4篇
综合类   5314篇
化学工业   27427篇
金属工艺   4816篇
机械仪表   4812篇
建筑科学   5409篇
矿业工程   1792篇
能源动力   2248篇
轻工业   11927篇
水利工程   1921篇
石油天然气   3781篇
武器工业   607篇
无线电   12840篇
一般工业技术   20260篇
冶金工业   4928篇
原子能技术   1502篇
自动化技术   11827篇
  2023年   480篇
  2022年   1220篇
  2021年   1999篇
  2020年   2733篇
  2019年   4280篇
  2018年   4505篇
  2017年   4931篇
  2016年   5341篇
  2015年   6036篇
  2014年   6575篇
  2013年   8426篇
  2012年   6818篇
  2011年   6698篇
  2010年   6743篇
  2009年   6617篇
  2008年   6347篇
  2007年   6170篇
  2006年   5549篇
  2005年   4599篇
  2004年   3887篇
  2003年   3354篇
  2002年   3356篇
  2001年   2955篇
  2000年   2442篇
  1999年   1414篇
  1998年   779篇
  1997年   701篇
  1996年   571篇
  1995年   488篇
  1994年   470篇
  1993年   350篇
  1992年   340篇
  1991年   313篇
  1990年   282篇
  1989年   320篇
  1988年   283篇
  1986年   279篇
  1984年   300篇
  1983年   278篇
  1979年   287篇
  1978年   359篇
  1977年   342篇
  1976年   356篇
  1975年   337篇
  1974年   396篇
  1973年   379篇
  1972年   357篇
  1971年   330篇
  1970年   281篇
  1969年   277篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results.  相似文献   
2.
为满足不同规格晶体探测器对分割校准晶体条响应事件位置数据的需求,开发了一种以禁忌搜索算法为核心,结合UDP数据帧、二维高斯模型及光导折射率的位置信息分割校准方法。实验结果表明,本方法在溢出率为5%时,峰谷比可达1218,空间分辨率达17 mm,晶体条响应位置识别准确度高达99%,滤除了引发伪峰的噪声,避免了过分割问题。在面对多种规格晶体阵列的位置谱时,本方法能依照阵列规格将晶体条区域的响应自动校准编号并输出晶体位置查找表,实现响应事件的精确校准。  相似文献   
3.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
4.
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry  相似文献   
5.
Journal of Signal Processing Systems - With the latest development of automation technology, object detection technology has received more and more research attention. Automated object detection...  相似文献   
6.
Neoantigen vaccines and adoptive dendritic cell (DC) transfer are major clinical approaches to initiate personalized immunity in cancer patients. However, the immunization efficacy is largely limited by the in vivo trajectory including neoantigens’ access to resident DCs and DCs’ access to lymph nodes (LNs). Herein, an innovative strategy is proposed to improve personalized immunization through neoantigen-loaded nanovaccines synergized with adoptive DC transfer. It is found that it enables selective delivery of neoantigens to resident DCs and macrophages by coating cancer cell membranes onto neoantigen-loaded nanoparticles. In addition, the nanovaccines promote the secretion of chemokine C-C motif ligand 2 (CCL2), CCL3, and C-X-C motif ligand 10 from macrophages, thus potentiating the access of transferred DCs to LNs. This immunization strategy enables coordinated delivery of identified neoantigens and autologous tumor lysate-derived undefined antigens, leading to initiation of antitumor T cell immunity in a personalized manner. It significantly inhibits tumor growth in prophylactic and established mouse tumor models. The findings provide a new vision for potentiating adoptive cell transfer by nanovaccines, which may open the door to a transformative possibility for improving personalized immunization.  相似文献   
7.
Uzun  İlhan  Orak  İkram  Yağmur  Hatice Karaer  Karakaplan  Mehmet  Yalman  Murat 《SILICON》2021,13(12):4703-4713
Silicon - 5-(2,4-dichlorophenyl)-2-furoic acid and anthraquinone-2-carboxylic acid were reacted separately with chitin. The synthesized products were characterized by various spectroscopic methods...  相似文献   
8.
A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m?2 h?1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m?2 h?1 and 96.9% after the cycles, indicating a superior antifouling property.  相似文献   
9.
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.  相似文献   
10.
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