全文获取类型
收费全文 | 15590篇 |
免费 | 2880篇 |
国内免费 | 1419篇 |
学科分类
工业技术 | 19889篇 |
出版年
2024年 | 87篇 |
2023年 | 441篇 |
2022年 | 572篇 |
2021年 | 728篇 |
2020年 | 731篇 |
2019年 | 648篇 |
2018年 | 675篇 |
2017年 | 745篇 |
2016年 | 811篇 |
2015年 | 944篇 |
2014年 | 1295篇 |
2013年 | 1084篇 |
2012年 | 1354篇 |
2011年 | 1338篇 |
2010年 | 911篇 |
2009年 | 824篇 |
2008年 | 829篇 |
2007年 | 938篇 |
2006年 | 876篇 |
2005年 | 759篇 |
2004年 | 615篇 |
2003年 | 556篇 |
2002年 | 368篇 |
2001年 | 293篇 |
2000年 | 241篇 |
1999年 | 205篇 |
1998年 | 174篇 |
1997年 | 155篇 |
1996年 | 152篇 |
1995年 | 100篇 |
1994年 | 101篇 |
1993年 | 64篇 |
1992年 | 59篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 6篇 |
1986年 | 51篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
“空中B超”——遥感影像用于考古 总被引:1,自引:0,他引:1
结合全球卫星定位系统GPS,遥感成像技术能提供大量对考古研究极为有价值的田野影像信息。结合不同年代拍摄的航空照片,考古学家从这些遥感影像中获得大量信息,并得以在近些年来取得很多举世瞩目的成果。本文列举了一系列典型事例,也披露了我国一些古迹的演变情况。 相似文献
82.
激光扫描三角法是近十年发展起来的三维传感新技术,其实现扫描测量的方法可分为两类:一是采用阵列器件,用相应的同步扫描机构实现;另一则采用单通道器件,由扫描装置进行步进扫描实现。虽然这种技术在陆地及空气系统中已得到广泛应用,但在水下却存在着许多问题。本文提出了一种新型空间差频扫描测量方式,并对扫描测量原理、测量周期、分辨率及速率进行了深入讨论,最后的应用结果显示了这种新型方式用于水下三维传感的特殊优越性。 相似文献
83.
成形反射面天线的设计与综合是近年来卫星天线发展的一个热点问题 ,本文对日本、北美和欧洲成形反射面天线的技术发展和综合方法作了介绍和比较。 相似文献
84.
卫星包装箱的随机隔振优化分析 总被引:1,自引:0,他引:1
用钢丝绳隔振器将卫星包装箱支承在运输车上,将卫星与车辆简化为二自由度体系,优化分析了在随机路面上行驶时使包装箱响应最小之隔振参数,对实测得到的钢丝绳减振器的非线性迟滞性能作了描述,提出了统计线性化分析的方法。 相似文献
85.
PLC在电厂输煤系统中的应用 总被引:3,自引:0,他引:3
介绍了可编程序控制器在电厂皮带机输煤控制系统中的应用,详细说明了远程I/O控制系统的特点和功能。 相似文献
86.
The UK's vast marine energy resource is mostly located in remote areas west and north of Scotland, and transmission of this energy to the mainland will be required. This may be achieved by using this ‘stranded’ power to generate hydrogen electrolytically, which may in turn be stored or transported using sponge iron technology. This paper reviews the technology and research needed to bring such a process on stream. We propose utilising techniques that have been developed for the oxygen carriers used in chemical looping, and also those used in early processes for hydrogen generation in the chemical industry. We briefly outline the design requirements for an energy efficient sponge iron plant. It is shown that the iron sponge system presents better energy efficiencies than alternative forms of bulk storage such as liquid hydrogen, magnesium hydride slurry, some at least of the metal hydrides, or methylcyclohexane–toluene–hydrogen, provided that requirements can be met for particle durability and reactivity. 相似文献
87.
Research presented in this paper deals with the systematic examination, development, and evaluation of a novel multimodal registration approach that can perform accurately and robustly for relatively close range surveillance applications. An analysis of multimodal image registration gives insight into the limitations of assumptions made in current approaches and motivates the methodology of the developed algorithm. Using calibrated stereo imagery, we employ maximization of mutual information in sliding correspondence windows that inform a disparity voting algorithm to demonstrate successful registration of objects in color and thermal imagery. Extensive evaluation of scenes with multiple objects at different depths and levels of occlusion shows high rates of successful registration. Ground truth experiments demonstrate the utility of the disparity voting techniques for multimodal registration by yielding qualitative and quantitative results that outperform approaches that do not consider occlusions. A basic framework for multimodal stereo tracking is investigated and promising experimental studies show the viability of using registration disparity estimates as a tracking feature. 相似文献
88.
用PSD检测长直导轨准直度 总被引:4,自引:0,他引:4
介绍了用光电位置传感器(PSD)检测长直导轨的原理和方法。利用PSD作为位置传感的检测系统能实时、连续地对被测件三维空间准直度进行检测,更好地解决了以往移动桥板分段测量、人工读数(数格)局部检测的方法存在的问题。 相似文献
89.
90.
Monitoring water quality in reservoirs with IRS-1A-LISS-I 总被引:1,自引:1,他引:0
V. K. Choubey 《Water Resources Management》1994,8(2):121-136
An attempt has been made to quantify the relationship between the variation in IRS-IA-LISS-I (Indian Remote Sensing Satellite-1A Linear Imaging Self-Scanning System) radiance data and field measured change in secchi disc depth. Secchi disc depth was measured for 47 predetermined sampling locations on reservoir surface water. At extinction depth (secchi depth), water samples were collected from all the sampling locations. Suspended sediments of eight locations representing various reaches of the reservoir were selected for mineralogical, particle size and optical properties analysis. The LISS-I radiance value in band 1 (0.45–0.52µm) band 2 (0-52–0.59 µm) and band 3 (0.62–0.68 µm) were used in a regression analysis. The absorption infrared band 4 (0.77–0.86 µm) was not included in the analysis. In these, the dependable variable was secchi depth (SD) and the LISS-I-radiance data was the estimator variable. Forty-seven data sets of 20 October 1988 from Tawa reservoir surface water were used to obtain an estimator equation for SD. The verification of the estimator equation was tested by applying it to a data set of 21 measurements of 28 September 1988 for this reservoir. The coefficient of correlation between observed and estimated values for the 28 September 1988 data set wasr=0.92 for SD, indicating that the equation could accurately predict the water clarity (SD) for this reservoir on new occasions from IRS-IA-LISS-I spectral data. It is shown that mineral composition and optical properties of suspended sediments influence the reflected radiance of water quality. It is concluded that IRS-IA-LISS-I data provide a useful means of mapping water quality in reservoir. 相似文献