全文获取类型
收费全文 | 45227篇 |
免费 | 7186篇 |
国内免费 | 5351篇 |
专业分类
电工技术 | 4576篇 |
技术理论 | 1篇 |
综合类 | 6852篇 |
化学工业 | 1535篇 |
金属工艺 | 835篇 |
机械仪表 | 3676篇 |
建筑科学 | 1405篇 |
矿业工程 | 1189篇 |
能源动力 | 768篇 |
轻工业 | 995篇 |
水利工程 | 1011篇 |
石油天然气 | 895篇 |
武器工业 | 790篇 |
无线电 | 5857篇 |
一般工业技术 | 2593篇 |
冶金工业 | 1286篇 |
原子能技术 | 101篇 |
自动化技术 | 23399篇 |
出版年
2024年 | 224篇 |
2023年 | 678篇 |
2022年 | 1370篇 |
2021年 | 1544篇 |
2020年 | 1681篇 |
2019年 | 1361篇 |
2018年 | 1236篇 |
2017年 | 1476篇 |
2016年 | 1735篇 |
2015年 | 1898篇 |
2014年 | 2769篇 |
2013年 | 2806篇 |
2012年 | 3370篇 |
2011年 | 3763篇 |
2010年 | 2910篇 |
2009年 | 3087篇 |
2008年 | 3223篇 |
2007年 | 3751篇 |
2006年 | 3338篇 |
2005年 | 2794篇 |
2004年 | 2224篇 |
2003年 | 2001篇 |
2002年 | 1620篇 |
2001年 | 1266篇 |
2000年 | 1111篇 |
1999年 | 915篇 |
1998年 | 734篇 |
1997年 | 533篇 |
1996年 | 418篇 |
1995年 | 369篇 |
1994年 | 283篇 |
1993年 | 233篇 |
1992年 | 196篇 |
1991年 | 107篇 |
1990年 | 89篇 |
1989年 | 124篇 |
1988年 | 71篇 |
1987年 | 41篇 |
1986年 | 28篇 |
1985年 | 37篇 |
1984年 | 36篇 |
1983年 | 52篇 |
1982年 | 40篇 |
1981年 | 35篇 |
1980年 | 28篇 |
1979年 | 25篇 |
1978年 | 23篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 831 毫秒
61.
介绍了池27井实施机抽排水工艺取得累计排水13 334.4m3的明显效果.分析了五次检泵的原因.提出了对池27井机抽排水的四点认识. 相似文献
62.
ZHU Liye FANG Yuan ZHANG Weidong 《机械工程学报(英文版)》2008,21(1):91-93
According to a type of normal nonlinear system, an indirect adaptive fuzzy (IAF) controller has been applied to those systems where no accurate mathematical models of the systems under control are available. To satisfy with system performance, an indirect accelerated adaptive fuzzy (IAAF) controller is proposed, and its general form is presented. The general form IAAF controller ensures necessary control criteria and system's global stability using Lyapunov Theorem. It has been proved that the close-loop system error converges to a small neighborhood of equilibrium point. The optimal IAAF controller is derived to guarantee the process's shortest settling time. Simulation results indicate the IAAF controller make the system more stable, accurate, and fast. 相似文献
63.
64.
提出了一种考虑分布电容的故障测距新算法。该算法基于微分方程描述的线路数学模型,利用单端信息对高压输电线路进行故障测距,保留了解微分方程算法的简单可靠、现实可行、不必考虑衰减直流分量和谐波及电网频率波动影响的特点,同时考虑过渡电阻和分布电容的影响,克服了传统解微分方程法中在经高阻接地故障时测距误差过大和忽略分布电容引起的故障定位不准确的缺点。为了检验算法的精度,进行了大量的动模实验。结果表明,算法原理正确并具有较高的测距精度。 相似文献
65.
66.
The goal of face recognition is to distinguish persons via their facial images. Each person's images form a cluster, and a new image is recognized by assigning it to the correct cluster. Since the images are very high-dimensional, it is necessary to reduce their dimension. Linear discriminant analysis (LDA) has been shown to be effective at dimension reduction while preserving the cluster structure of the data. It is classically defined as an optimization problem involving covariance matrices that represent the scatter within and between clusters. The requirement that one of these matrices be nonsingular restricts its application to datasets in which the dimension of the data does not exceed the sample size. For face recognition, however, the dimension typically exceeds the number of images in the database, resulting in what is referred to as the small sample size problem. Recently, the applicability of LDA has been extended by using the generalized singular value decomposition (GSVD) to circumvent the nonsingularity requirement, thus making LDA directly applicable to face recognition data. Our experiments confirm that LDA/GSVD solves the small sample size problem very effectively as compared with other current methods. 相似文献
67.
A manufacturability evaluation decision model is formulated and analyzed based on fuzzy logic and multiple attribute decision-making under the concurrent engineering environment. The study emphasizes on the treatment of the linguistic and vagueness at the early product development stage. The study also considers the function integration of the total life cycle of a product. Hence, the integrated decision model covers the multi-level, multi-goal requirements of the products. Multiple criteria such as the goal space, the decision space, the function space, the development (i.e., product & process design) space, and the activity space, are then applied under different analysis of decision-making methods. For instances, the fuzzy multiple attribute decision-making (FMADM) combined with activity-based costing (ABC) can be used in the activity decision space. The fuzzy logic decision model can be applied in the goal decision space. The results of this study point out the importance of early decision making capability. An example of a high-pressure vessel is provided to demonstrate the proposed model for evaluating the manufacturability. 相似文献
68.
Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
介绍了一种基于人工神经网络(ANN)的声目标识别系统,概述了用MATLAB专用工具箱对神经网络权值进行训练及仿真的过程,叙述了ANN目标识别系统的数字信号处理器(DSP)实时实现过程,并着重分析定点实现过程中程序变量的定标、非线性运算的实现、溢出的处理等关键步骤.对不同字长的识别结果进行比较表明,基于定点实时实现的系统数据保持很高的精度,可以得到与浮点处理相同的识别率. 相似文献
70.