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   393142篇
  免费   32212篇
  国内免费   18168篇
电工技术   24406篇
技术理论   47篇
综合类   28687篇
化学工业   63805篇
金属工艺   23286篇
机械仪表   25307篇
建筑科学   30825篇
矿业工程   12990篇
能源动力   10799篇
轻工业   26047篇
水利工程   7790篇
石油天然气   25131篇
武器工业   3315篇
无线电   42838篇
一般工业技术   42578篇
冶金工业   20140篇
原子能技术   4077篇
自动化技术   51454篇
  2024年   1580篇
  2023年   5948篇
  2022年   10798篇
  2021年   15166篇
  2020年   11421篇
  2019年   9247篇
  2018年   10736篇
  2017年   12067篇
  2016年   11041篇
  2015年   15337篇
  2014年   19544篇
  2013年   23277篇
  2012年   25692篇
  2011年   28319篇
  2010年   25174篇
  2009年   23815篇
  2008年   23526篇
  2007年   22540篇
  2006年   22607篇
  2005年   19824篇
  2004年   13588篇
  2003年   11865篇
  2002年   10953篇
  2001年   9703篇
  2000年   9466篇
  1999年   9871篇
  1998年   7469篇
  1997年   6342篇
  1996年   6018篇
  1995年   4908篇
  1994年   3999篇
  1993年   2687篇
  1992年   2141篇
  1991年   1604篇
  1990年   1266篇
  1989年   1033篇
  1988年   846篇
  1987年   536篇
  1986年   418篇
  1985年   262篇
  1984年   210篇
  1983年   168篇
  1982年   130篇
  1981年   78篇
  1980年   103篇
  1979年   49篇
  1978年   17篇
  1977年   23篇
  1976年   28篇
  1951年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
通过对HP295封头冲压开裂件缺陷光电镜分析,查找到缺陷产生部位及其导致原因。对多组铸坯低倍样检查,发现中间裂纹是缺陷根源。此后,根据现场生产情况,分析钢中磷、硫含量、钢水过热度、铸机设备精度、拉速和二次冷却强度等因素对铸坯中间裂纹的影响。通过降低磷、硫,控制过热度,调整设备精度,降低拉速以及优化二次冷却等措施,HP295铸坯中间裂纹得到有效控制,用户加工开裂现象完全杜绝。  相似文献   
32.
Micro Aerial Vehicles (MAVs) have great potentials to be applied for indoor search and rescue missions. In this paper, we propose a modular lightweight design of an autonomous MAV with integrated hardware and software. The MAV is equipped with the 2D laser scanner, camera, mission computer and flight controller, running all the computation onboard in real time. The onboard perception system includes a laser‐based SLAM module and a custom‐designed visual detection module. A dual Kalman filter design provides robust state estimation by multiple sensor fusion. Specifically, the fusion module provides robust altitude measurement in the circumstance of surface changing. In addition, indoor‐outdoor transition is explicitly handled by the fusion module. In order to efficiently navigate through obstacles and adapt to multiple tasks, a task tree‐based mission planning method is seamlessly integrated with path planning and control modules. The MAV is capable of searching and rescuing victims from unknown indoor environments effectively. It was validated by our award‐winning performance at the 2017 International Micro Air Vehicle Competition (IMAV 2017), held in Toulouse, France. The performance video is available on https://youtu.be/8H19ppS_VXM .  相似文献   
33.
International Journal of Control, Automation and Systems - In this paper, a composite fault-tolerant control problem is studied for a class of uncertain nonlinear system with asymmetric input...  相似文献   
34.
35.
Neural Computing and Applications - Traffic identification is currently an important challenge for network management and security. In this paper, we propose a novel application identification...  相似文献   
36.
In the field of images and imaging, super-resolution (SR) reconstruction of images is a technique that converts one or more low-resolution (LR) images into a highresolution (HR) image. The classical two types of SR methods are mainly based on applying a single image or multiple images captured by a single camera. Microarray camera has the characteristics of small size, multi views, and the possibility of applying to portable devices. It has become a research hotspot in image processing. In this paper, we propose a SR reconstruction of images based on a microarray camera for sharpening and registration processing of array images. The array images are interpolated to obtain a HR image initially followed by a convolution neural network (CNN) procedure for enhancement. The convolution layers of our convolution neural network are 3×3 or 1×1 layers, of which the 1×1 layers are used to improve the network performance particularly. A bottleneck structure is applied to reduce the parameter numbers of the nonlinear mapping and to improve the nonlinear capability of the whole network. Finally, we use a 3×3 deconvolution layer to significantly reduce the number of parameters compared to the deconvolution layer of FSRCNN-s. The experiments show that the proposed method can not only ameliorate effectively the texture quality of the target image based on the array images information, but also further enhance the quality of the initial high resolution image by the improved CNN.  相似文献   
37.
A size-dependent governing equation is derived to investigate the torsional static behaviors of two-dimensionally functionally graded microtubes based on the modified couple stress theory. The shear modulus is assumed to vary along the tube’s length direction according to an exponential distribute function, and varies along the tube’s radius direction according to a power-law function. A generalized differential quadrature method is developed to determine the rotational angle and shear stresses. Some illustrative examples are given to investigate the effects of applied torques, the length scale parameter and various material compositions on the torsional angle and shear stresses.  相似文献   
38.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view.  相似文献   
39.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper.  相似文献   
40.
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