全文获取类型
收费全文 | 31331篇 |
免费 | 2934篇 |
国内免费 | 1836篇 |
专业分类
电工技术 | 1766篇 |
综合类 | 3249篇 |
化学工业 | 2292篇 |
金属工艺 | 3359篇 |
机械仪表 | 2851篇 |
建筑科学 | 5886篇 |
矿业工程 | 1456篇 |
能源动力 | 1011篇 |
轻工业 | 564篇 |
水利工程 | 1217篇 |
石油天然气 | 1001篇 |
武器工业 | 572篇 |
无线电 | 1946篇 |
一般工业技术 | 5625篇 |
冶金工业 | 1573篇 |
原子能技术 | 215篇 |
自动化技术 | 1518篇 |
出版年
2024年 | 135篇 |
2023年 | 322篇 |
2022年 | 657篇 |
2021年 | 762篇 |
2020年 | 938篇 |
2019年 | 812篇 |
2018年 | 782篇 |
2017年 | 1070篇 |
2016年 | 1100篇 |
2015年 | 1175篇 |
2014年 | 1838篇 |
2013年 | 1757篇 |
2012年 | 2068篇 |
2011年 | 2201篇 |
2010年 | 1810篇 |
2009年 | 2002篇 |
2008年 | 1822篇 |
2007年 | 2304篇 |
2006年 | 1952篇 |
2005年 | 1694篇 |
2004年 | 1297篇 |
2003年 | 1205篇 |
2002年 | 1050篇 |
2001年 | 946篇 |
2000年 | 774篇 |
1999年 | 609篇 |
1998年 | 513篇 |
1997年 | 522篇 |
1996年 | 366篇 |
1995年 | 328篇 |
1994年 | 260篇 |
1993年 | 195篇 |
1992年 | 178篇 |
1991年 | 139篇 |
1990年 | 118篇 |
1989年 | 112篇 |
1988年 | 75篇 |
1987年 | 39篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 33篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 2篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
本文通过对带钢窄边线状裂纹缺陷的金相显微组织观察和扫描电镜与能谱分析,确定了带钢窄边线状裂纹缺陷的形成原因,并针对原因提出了相应的预防措施,有效地控制了带钢窄边线状裂纹缺陷的重复发生。 相似文献
92.
93.
The concept of a fracture process zone where damage takes place is used to analyse the delaminations at the free edges of angle ply laminates under uniaxial tension. The use of a fracture process zone removes the singularity in the interlaminar stresses and enables the initiation and growth of delaminations to be modelled for a perfect laminate without any assumed prior defects. Two different models for the stress displacement relationship in the fracture process zone are examined: a constant stress up to critical displacement and a linear relationship. Finite element analysis shows that there is little difference in the predictions obtained from the two models. An approximate analysis is presented for the constant stress stress-displacement model which is shown to agree with a finite element solution and experimental data. Hence it is argued that the approximate method using a constant stress model for the fracture process zone is sufficient for accurate prediction of delaminations. 相似文献
94.
95.
96.
One of the symptoms of plagues, epidemics or pandemics is often a fever, so during such unprecedented times, handheld infrared thermometers are vital devices for monitoring symptomatic individuals. It is therefore very important to enhance reading efficiency when these thermometers are used for lengthy periods of time in a low illuminance environment. The need for the efficient reading of infrared thermometers or a fast reaction time when reading the information is even more relevant now during the COVID-19 pandemic. In this study, a target search experiment of digital characters is carried out through a simulated interface and use scenarios of a handheld thermometer based on three variables: the inclination angle or slant of the seven segment display characters, screen brightness, and ambient illuminance. The experimental results show that the inclination angle or slant of the characters and ambient illuminance have a significant effect on the reaction speed. In general, the slowest reaction time is found when reading characters with a slant of 10° to the left and the reaction time is the fastest with a right slant of 20°. A continued reduction in ambient illuminance does not affect the visual recognition performance but instead further enhances reading efficiency. Increasing the screen brightness increases the reaction time more in relatively low ambient illuminance conditions as opposed to relatively high ambient illuminance, which implies that in higher ambient illuminance conditions, a brighter screen needs to be used to obtain the same reaction speed as that in lower ambient illuminance conditions. 相似文献
97.
倾角是许多控制系统中需要测量的一个重要参数。针对倾角测量,设计了一种基于ARM微控制器和加速度传感器的角度测量平台。该平台采用基于ARMCortex—M3内核的STM32F103VE为数据处理的核心,利用高精度加速度传感器MMA7361L为测角传感器,同时配置液晶屏和小型键盘实现了人机交互。该平台具有测量精度高、灵敏度高、价格低的特点,应用前景广阔。 相似文献
98.
介绍了加速度传感器MMA7260的工作原理、结构及功能,设计了一个基于ARM的实时嵌入式自动检测系统,使用μC/OS-II操作系统,构造一个具有角度测量、相关数据处理以及与上位机通信等功能的现场角度测量单元,上位机则主要完成系统监控和人机交互等功能。 相似文献
99.
在对两轴稳定平台一般构型分析的基础上,指出了其在俯仰方向大角度时稳定控制存在的不足,提出了采用三正交陀螺稳定控制方式解决大俯仰角控制问题的方法,最后利用MATLAB进行了数学仿真,结果表明该方法有效提高了系统的稳定精度。 相似文献
100.
The Kirchhoff approximation is used to show that the time domain impulse response of an isolated flat crack can be given a simple geometrical interpretation in terms of the derivative of a projected length function. For an elliptical crack, this derivative can be obtained explicitly to yield the two edge-diffracted waves which originate from the flashpoints of the crack. An explicit coordinate invariant expression is obtained from this elliptical crack solution which relates the time difference, t, between the arrival of these edge-diffracted waves and the crack size and orientation. Previously, we have proposed that this expression, together with t measurements in different scattering directions, could be used in a regression analysis as the basis for performing a constrained inversion of crack scattering data (i.e., where we attempt to obtain the best equivalent flat elliptical crack that fits the scattering measurements). Here we will demonstrate some results of applying the proposed algorithm using noisy synthetic data. The sensitivity of the results to both, number of measurements and transducer orientation, will be discussed. 相似文献