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   363642篇
  免费   25985篇
  国内免费   12561篇
电工技术   18241篇
技术理论   56篇
综合类   19740篇
化学工业   63351篇
金属工艺   19125篇
机械仪表   21733篇
建筑科学   27580篇
矿业工程   11036篇
能源动力   10605篇
轻工业   21264篇
水利工程   5548篇
石油天然气   23140篇
武器工业   2602篇
无线电   38794篇
一般工业技术   45420篇
冶金工业   23558篇
原子能技术   3416篇
自动化技术   46979篇
  2024年   1315篇
  2023年   5465篇
  2022年   9296篇
  2021年   13173篇
  2020年   10286篇
  2019年   8561篇
  2018年   9866篇
  2017年   11025篇
  2016年   10144篇
  2015年   12990篇
  2014年   16853篇
  2013年   21038篇
  2012年   21790篇
  2011年   24502篇
  2010年   20673篇
  2009年   19746篇
  2008年   19684篇
  2007年   19021篇
  2006年   19699篇
  2005年   17342篇
  2004年   11416篇
  2003年   10059篇
  2002年   9039篇
  2001年   8007篇
  2000年   8521篇
  1999年   10183篇
  1998年   8642篇
  1997年   7209篇
  1996年   6812篇
  1995年   5773篇
  1994年   4801篇
  1993年   3515篇
  1992年   2876篇
  1991年   2189篇
  1990年   1823篇
  1989年   1552篇
  1988年   1290篇
  1987年   976篇
  1986年   821篇
  1985年   648篇
  1984年   509篇
  1983年   460篇
  1982年   435篇
  1981年   338篇
  1980年   305篇
  1979年   249篇
  1978年   198篇
  1977年   173篇
  1976年   177篇
  1975年   154篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Frontiers of Information Technology & Electronic Engineering - Reconstruction of a 12-lead electrocardiogram (ECG) from a serial 3-lead ECG has been researched in the past to satisfy the need...  相似文献   
62.
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   
63.
64.
Theabrownins (TB) are polymeric phenolic compounds associated with the multiple bioactivities of Pu-erh tea, a post-fermented Chinese dark tea. High-TB instant Pu-erh tea was produced via a novel submerged fermentation (SF) using Aspergillus tubingensis and compared with samples produced commercially via the conventional solid-state fermentation (SSF). Viable microorganisms and microbial toxins, especially aflatoxins B1, G1, B2, G2, cyclopiazonic acid, fumonisins B1, B2, B3 and ochratoxin A, were below the detection limit in all samples. Fewer microbial metabolites were found in SF instant tea compared with the SSF teas. Based on an adult consuming 1 g of instant Pu-erh tea daily, the dietary intake of investigated elements was below the safe limits recommended by various authorities. Tasters viewed the instant tea infusions as very mild, smooth, mellow and full. This suggested that submerged fermentation using A. tubingensis offers a speedy and safe alternative to commercial production of instant Pu-erh tea.  相似文献   
65.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process.  相似文献   
66.
67.
Wang  Xin  Guo  Yi  Wang  Yuanyuan  Yu  Jinhua 《Neural computing & applications》2019,31(4):1069-1081

Breast cancer is one of the most common female malignancies, as well as the second leading cause of mortality for women. Early detection and treatment can dramatically decrease the mortality rate. Recently, automated breast volume scanner (ABVS) has become one of the most frequently used diagnose methods for breast tumor screening because of its operator-independent and reproducible advantages. However, it is a challenging job to obtain the tumors’ accurate locations and shapes by reviewing hundreds of ABVS slices. In this paper, a novel computer-aided detection (CADe) system is developed to reduce clinicians’ reading time and improve the efficiency. The CADe system mainly contains three parts: tumor candidate acquisition, false-positive reduction and tumor segmentation. Firstly, a local phase-based approach is built to obtain breast tumor candidates for further recognition. Subsequently, a convolutional neural network (CNN) is applied to reduce false positives (FPs). The introduction of CNN can help to avoid complicated feature extraction as well as elevate the accuracy and efficiency. Finally, superpixel-based segmentation is used to outline the breast tumor. Here, superpixel-based local binary pattern (SLBP) is proposed to assist the segmentation, which improves the performance. The methods were evaluated on a clinical ABVS dataset whose abnormal cases were manually labeled by an experienced radiologist. The experiment results were mainly composed of two parts. At the FP reduction stage, the proposed CNN achieved 100% and 78.12% sensitivity with FPs/case of 2.16 and 0. At the segmentation stage, our SLBP obtained 82.34% true positive, 15.79% false positive and 83.59% Dice similarity. In summary, the proposed CADe system demonstrated promising potential to detect and outline breast tumors in ABVS images.

  相似文献   
68.
Yang  Luxia  Wang  Wanjun 《Microsystem Technologies》2019,25(6):2241-2247
Microsystem Technologies - In this paper, the design and fabrication of an on-chip micro flow cytometer chip with integrated micro-lens with a size of...  相似文献   
69.
JOM - The Isa/Ausmelt smelting technology with a top submerged lance (TSL) has been extensively used in copper smelting processes. However, the TSL is extremely vulnerable to damage and failure...  相似文献   
70.
为了实现对微小环片零件的自动化装配,搭建了自动装配系统.通过4根直线导向轴与4个直线轴承来提高系统的导向精度和刚度.采用直线导轨进行各装配作业模块之间的切换,保证了微小环片零件的自动装配与取出.在环片的装配方向上,螺旋升降机和光栅尺实现环片的位置精度控制.在Lab VIEW编程环境中,采用分层软件架构和模块化控制思想,避免了不必要的数据循环检测与丢失,能够达到环片组件的装配精度要求.控制系统分为系统初始化模块、参数设置模块、装配模块和取出模块,自动装配系统通过各个模块间的相互交流配合完成装配任务.采用本文中自动装配系统装配环片的实验结果表明,环片零件装配的最大位置误差为26μm,垂直度误差为17μm,平均装配时间为75 s/片,可满足环片组件所需的精度要求.  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