首页 | 官方网站   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   31974篇
  免费   2948篇
  国内免费   1587篇
工业技术   36509篇
  2024年   113篇
  2023年   574篇
  2022年   908篇
  2021年   1337篇
  2020年   1147篇
  2019年   875篇
  2018年   966篇
  2017年   1050篇
  2016年   944篇
  2015年   1341篇
  2014年   1529篇
  2013年   1776篇
  2012年   1898篇
  2011年   2037篇
  2010年   1795篇
  2009年   1634篇
  2008年   1754篇
  2007年   1700篇
  2006年   1679篇
  2005年   1403篇
  2004年   1080篇
  2003年   1322篇
  2002年   1725篇
  2001年   1516篇
  2000年   872篇
  1999年   828篇
  1998年   534篇
  1997年   436篇
  1996年   384篇
  1995年   334篇
  1994年   264篇
  1993年   180篇
  1992年   150篇
  1991年   90篇
  1990年   86篇
  1989年   62篇
  1988年   42篇
  1987年   37篇
  1986年   24篇
  1985年   19篇
  1984年   9篇
  1983年   9篇
  1982年   5篇
  1981年   9篇
  1980年   9篇
  1979年   7篇
  1978年   5篇
  1977年   2篇
  1976年   4篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 45 毫秒
41.
运用过程中各类相关因子的变化,会使得机车柴油机配气相位出现一定程度变化,采取某种措施调整或是处理可以解决动力不足的问题。  相似文献   
42.
43.
44.
为抑制铝碳质长水口使用过程中石墨的氧化,其表面会涂覆含 20%~30%Al2O3的抗氧化涂层,但切割丝钢等特种钢冶炼过程必须严格控制钢液中夹杂的 Al2O3的含量,因此需要制备低氧化铝含量的抗氧化涂层。本文通过调节涂料组成、加水量和水玻璃加入量制备了低铝抗氧化涂层,并利用扫描电镜分析了抗氧化实验后试样断口的显微结构。结果表明:以粘土粉、钾长石粉和硅砂为主要原料,添加 10%硼砂的涂料可在 800 ℃形成良好的釉层,此时涂料中 A12O3的含量可降至 12%,得到了低铝涂料;当加入占涂料质量 80%的水和 40%的水玻璃时,涂层具有最佳的涂覆性能和抗氧化性能,涂层和长水口基体结合致密,保护了长水口中的石墨不被氧化。  相似文献   
45.
The application of deep learning in the field of object detection has experienced much progress. However, due to the domain shift problem, applying an off-the-shelf detector to another domain leads to a significant performance drop. A large number of ground truth labels are required when using another domain to train models, demanding a large amount of human and financial resources. In order to avoid excessive resource requirements and performance drop caused by domain shift, this paper proposes a new domain adaptive approach to cross-domain vehicle detection. Our approach improves the cross-domain vehicle detection model from image space and feature space. We employ objectives of the generative adversarial network and cycle consistency loss for image style transfer in image space. For feature space, we align feature distributions between the source domain and the target domain to improve the detection accuracy. Experiments are carried out using the method with two different datasets, proving that this technique effectively improves the accuracy of vehicle detection in the target domain.  相似文献   
46.
The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe (3DAP) and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni (Co-Ti) interactions than Co-Ti (Fe-Ti) interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition.  相似文献   
47.
Sun  Xiuping  Wang  Lu  Li  Chuanchuan  Wang  Debao  Sikandar  Iqbal  Man  Ruxia  Tian  Fang  Qian  Yitai  Xu  Liqiang 《Nano Research》2021,14(12):4696-4703

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as attractive alternatives for next-generation battery systems, which have promising application potential due to their earth abundance of potassium and sodium, high capacity and suitable working potential, however, the design and application of bi-functional high-performance anode still remain a great challenge up to date. Bismuth sulfide is suitable as anode owing to its unique laminar structure with relatively large interlayer distance to accommodate larger radius ions, high theoretical capacity and high volumetric capacity etc. In this study, dandelion-like Bi2S3/rGO hierarchical microspheres as anode material for PIBs displayed reversible capacity, and 206.91 mAh·g−1 could be remained after 1,200 cycles at a current density of 100 mA·g−1. When applied as anode materials for SIBs, 300 mAh·g−1 could be retained after 300 cycles at 2 A·g−1 and its initial Coulombic efficiency is as high as 97.43%. Even at high current density of 10 A·g−1, 120.3 mAh·g−1 could be preserved after 3,400 cycles. The Na3V2(PO4)3@rGO//Bi2S3/rGO sodium ion full cells were successfully assembled which displays stable performance after 60 cycles at 100 mA·g−1. The above results demonstrate that Bi2S3/rGO has application potential as high performance bi-functional anode for PIBs and SIBs.

  相似文献   
48.
Al/Cu dissimilar joint has been widely produced by using friction stir welding (FSW), but the weld quality remains limited. A recently developed ultrasonic  相似文献   
49.
The spinterface formed between ferromagnetic(FM)electrode and organic materials is vital for performance optimization in organic spin valve(OSV).Half-metallic Fe3O4with drastic change in structure,conductivity and magnetic property near Verwey transition can serve as an intrinsic spinterface regulator.However,such modulating effect of Fe3O4in OSV has not been comprehensively investigated,especially below the Verwey transition temperature(Tv).Here,we highlight the important role of Fe3O4electrode in reliable-working and controllable Fe3O4/P3HT/Co polymer spin valves by investigating the magnetoresistance(MR)above and below 7V.In order to distinguish between different contributions to charge transport and related MR responses,the systematic electronic and magnetic characterizations were carried out in full temperature range.Particularly,the first-order metal-insulator transition in Fe3O4has a dramatic effect on the MR enhancement of polymer spin valves at 7V.Moreover,both the conducting mode transformation and MR line shape modulation could be accomplished across 7V.This research renders unique scenario to multimodal storage by external thermodynamic parameters,and further reveals the importance of spin-dependent interfacial modification in polymer spin valves.  相似文献   
50.
International Journal of Control, Automation and Systems - There is a class of typical nonlinear industrial process, which can be characterized by a first-order inertia plus pure delay model in an...  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-23

京公网安备 11010802026262号