全文获取类型
收费全文 | 37467篇 |
免费 | 8307篇 |
国内免费 | 5961篇 |
专业分类
电工技术 | 1510篇 |
综合类 | 4982篇 |
化学工业 | 846篇 |
金属工艺 | 712篇 |
机械仪表 | 3297篇 |
建筑科学 | 1166篇 |
矿业工程 | 494篇 |
能源动力 | 257篇 |
轻工业 | 1028篇 |
水利工程 | 283篇 |
石油天然气 | 418篇 |
武器工业 | 512篇 |
无线电 | 10341篇 |
一般工业技术 | 3454篇 |
冶金工业 | 374篇 |
原子能技术 | 200篇 |
自动化技术 | 21861篇 |
出版年
2024年 | 355篇 |
2023年 | 860篇 |
2022年 | 1420篇 |
2021年 | 1724篇 |
2020年 | 1648篇 |
2019年 | 1353篇 |
2018年 | 1216篇 |
2017年 | 1584篇 |
2016年 | 1685篇 |
2015年 | 2031篇 |
2014年 | 2672篇 |
2013年 | 2531篇 |
2012年 | 3354篇 |
2011年 | 3340篇 |
2010年 | 2926篇 |
2009年 | 2889篇 |
2008年 | 3042篇 |
2007年 | 3207篇 |
2006年 | 2600篇 |
2005年 | 2286篇 |
2004年 | 1819篇 |
2003年 | 1428篇 |
2002年 | 1118篇 |
2001年 | 884篇 |
2000年 | 683篇 |
1999年 | 535篇 |
1998年 | 436篇 |
1997年 | 395篇 |
1996年 | 308篇 |
1995年 | 238篇 |
1994年 | 206篇 |
1993年 | 172篇 |
1992年 | 145篇 |
1991年 | 106篇 |
1990年 | 109篇 |
1989年 | 77篇 |
1988年 | 65篇 |
1987年 | 40篇 |
1986年 | 45篇 |
1985年 | 44篇 |
1984年 | 35篇 |
1983年 | 36篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1965年 | 4篇 |
1964年 | 3篇 |
1960年 | 4篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
本文所提出的新算法 BANDC 是 BAyes Normal Dynamic Clustering 的缩写。这个算法的目的是从遥感图象识别地理环境。它的优点是:能由机器自动按照图象估算出分类器的参数;作为一种特殊的 Bayes 分类器,它能够依靠计算机估算出{wi}的先验概率,于是能剔除野点,提高分类器的鲁棒性。这个算法的关键是应用拟合法从灰度等级直方图估算出参数。 相似文献
32.
No authorship indicated 《Canadian Metallurgical Quarterly》2004,59(8):787
Provides the biography of Cortney S. Warren and announces that she has received the APA Psi Chi/APA Edwin B. Newman Graduate Research Award (2004) for an outstanding research paper whose findings examine the potential for ethnicity to protect against body image disturbance by moderating the relationships between awareness and internalization of a thin physical ideal and body dissatisfaction. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
V Arvis B Michalet‐Doreau C Debain 《Journal of the science of food and agriculture》2004,84(14):1848-1854
We present a new computer vision method for measuring the physical characteristics of maize silages based on the extraction of image textural features, namely five Haralick features, the moments of order 1 and 2 on the grey levels of the image, and a fractal parameter. To show the effectiveness of these features for characterising the physical properties of the maize silage, a trial was performed on three maize cultivars (Zea mays L, a mid–early hybrid and an early hybrid) to study the effects of the ensiling process. The features could discern effects of the ensiling process on the physical properties of the maize silage. These effects were neither significant by comparing particle size distributions, nor with chemical compositions, whereas a biological response (degradation in the rumen) to the ensiling process exists. Thus image textural features seemed to give new and interesting measurements of the physical properties of the silage, explaining the biological response better than other methods. Furthermore, the ensiling effect was not the same with all the maize types and varied with the proportion of large particles in the silages. Linear relations between features before and after the ensiling process made it possible to predict a measure on a silage knowing its value on the parent forage. Copyright © 2004 Society of Chemical Industry 相似文献
34.
主要论述了采用图像边缘检测和图像跟踪算法对采集的关节镜图像进行图像处理和分析的过程。在图像处理的基础上,系统自动测量出指定目标的形状参数,实现了系统的测量要求。本研究为实现关节镜手术过程图像的保存和手术的准确性提供了可行的方法。 相似文献
35.
Sarrazin Jean-Christophe; Giraudo Marie-Dominique; Pailhous Jean; Bootsma Reinoud J. 《Canadian Metallurgical Quarterly》2004,30(3):411
In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
37.
一种固定阈值的毫米波图像边缘检测方法 总被引:1,自引:0,他引:1
文章提出了一种固定阈值的毫米波图像边缘检测方法。根据图像的统计特征确定出像素的标准梯度强度,并采用单阈值对图像进行边缘粗定位,然后施行非最大抑制处理和滤波,得到最终检测结果。由于该算法对各幅毫米波图像设置相同的阈值,故能实现自动检测,同时还具有计算量小的特点。实验结果表明该方法进行毫米波图像边缘检测的有效性和可行性。 相似文献
38.
为了适应MMS(多媒体短信息业务)的发展,提出了一个基于图像扭曲的变形动画生成机制。该机制不仅能够实时地产生效果新奇、富于戏剧性的GIF动画,而且能够根据不同终端的特点实现图像的自适应处理,从而使在无线网络上传输丰富多彩的图像文件变得更为方便。 相似文献
39.
Many research projects require accurate delineation of different secondary succession (SS) stages over large regions/subregions of the Amazon basin. However, the complexity of vegetation stand structure, abundant vegetation species, and the smooth transition between different SS stages make vegetation classification difficult when using traditional approaches such as the maximum likelihood classifier (MLC). Most of the time, classification distinguishes only between forest/non-forest. It has been difficult to accurately distinguish stages of SS. In this paper, a linear mixture model (LMM) approach is applied to classify successional and mature forests using Thematic Mapper (TM) imagery in the Rondônia region of the Brazilian Amazon. Three endmembers (i.e., shade, soil, and green vegetation or GV) were identified based on the image itself and a constrained least-squares solution was used to unmix the image. This study indicates that the LMM approach is a promising method for distinguishing successional and mature forests in the Amazon basin using TM data. It improved vegetation classification accuracy over that of the MLC. Initial, intermediate, and advanced successional and mature forests were classified with overall accuracy of 78.2% using a threshold method on the ratio of shade to GV fractions, a 7.4% increase over the MLC. The GV and shade fractions are sensitive to the change of vegetation stand structures and better capture biophysical structure information. 相似文献
40.
E. Gorges L. M. Raez A. Schillings I. Egry 《International Journal of Thermophysics》1996,17(5):1163-1172
Electromagnetic levitation is a useful tool for measuring thermophysical properties of high-temperature melts such as liquid metals. Due to its noncontact nature, the undercooled regime is also accessible. Density and thermal expansion of a levitated drop can be derived from volume measurements, if its mass is known. Assuming cylindrical symmetry, the volume of a drop can be determined from its cross section. Using photography, such measurements on liquid metals have been performed in the past. Here we present an improvement of this method, which replaces the photographic camera with a CCD videocamera and subsequent digital image processing. This reduces the time effect required to obtain the results and allows one to average over disturbing surface oscillations. The specific problems of digital image processing, namely resolution and edge detection, are addressed and results on nickel are presented.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1991, Köln, Germany. 相似文献