全文获取类型
收费全文 | 355224篇 |
免费 | 41776篇 |
国内免费 | 30204篇 |
专业分类
电工技术 | 32583篇 |
综合类 | 39677篇 |
化学工业 | 42319篇 |
金属工艺 | 25567篇 |
机械仪表 | 25180篇 |
建筑科学 | 26423篇 |
矿业工程 | 16100篇 |
能源动力 | 9134篇 |
轻工业 | 41651篇 |
水利工程 | 12258篇 |
石油天然气 | 12415篇 |
武器工业 | 5502篇 |
无线电 | 36324篇 |
一般工业技术 | 27920篇 |
冶金工业 | 15596篇 |
原子能技术 | 6247篇 |
自动化技术 | 52308篇 |
出版年
2024年 | 2328篇 |
2023年 | 6118篇 |
2022年 | 14439篇 |
2021年 | 18461篇 |
2020年 | 12984篇 |
2019年 | 8937篇 |
2018年 | 9516篇 |
2017年 | 11372篇 |
2016年 | 9963篇 |
2015年 | 16084篇 |
2014年 | 20202篇 |
2013年 | 23785篇 |
2012年 | 29964篇 |
2011年 | 31453篇 |
2010年 | 29675篇 |
2009年 | 28169篇 |
2008年 | 29505篇 |
2007年 | 28597篇 |
2006年 | 24520篇 |
2005年 | 20148篇 |
2004年 | 14294篇 |
2003年 | 9243篇 |
2002年 | 8470篇 |
2001年 | 7583篇 |
2000年 | 6062篇 |
1999年 | 2136篇 |
1998年 | 506篇 |
1997年 | 383篇 |
1996年 | 344篇 |
1995年 | 234篇 |
1994年 | 178篇 |
1993年 | 199篇 |
1992年 | 180篇 |
1991年 | 133篇 |
1990年 | 144篇 |
1989年 | 136篇 |
1988年 | 81篇 |
1987年 | 67篇 |
1986年 | 53篇 |
1985年 | 36篇 |
1984年 | 32篇 |
1983年 | 38篇 |
1982年 | 41篇 |
1981年 | 63篇 |
1980年 | 102篇 |
1979年 | 68篇 |
1965年 | 8篇 |
1959年 | 70篇 |
1957年 | 5篇 |
1951年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
131.
132.
134.
THz source based on optical Cherenkov radiation 总被引:1,自引:0,他引:1
135.
By analysis of the basic properties of entanglement swapping of high-dimensional Bell states,a universal and general deterministic secure quantum communication(DSQC)protocol is proposed,in which unitary operation is not required.By making use of the results of high-dimensional Bell measurement,the sender and the receiver can encode and decode the message respectively by performing the modular addition and subtraction.Two mutually complementary bases are constructed;and according to the property of mutual complement,a method for checking security of the high-dimensional quantum channel is put forward.Some common attack strategies are analyzed,and the corresponding error rates are calculated.Then the upper bound of the threshold of error rate is deduced. 相似文献
136.
When the initial frequencies and chirp rates of multi-component linear frequency modulation (LFM or chirp) signals are close,the signals may not be distinguished in the fractional Fourier domain (FRFD).Consequently,some signals cannot be detected.In this paper,first,the spectral distribution characteristics of a continuous LFM signal in the FRFD are analyzed,and then the spectral distribution characteristics of a LFM signal in the discrete FRFD are analyzed.Second,the critical resolution distance between the peaks of two LFM signals in the FRFD is deduced,and the relationship between the dimensional normalization parameter and the distance between two LFM signals in the FRFD is also deduced.It is discovered that selecting a proper dimensional normalization parameter can increase the distance.Finally,a method to select the parameter is proposed,which can improve the resolution ability of the fractional Fourier transform (FRFT).Its effectiveness is verified by simulation results. 相似文献
137.
In the training of feedforward neural networks,it is usually suggested that the initial weights should be small in magnitude in order to prevent premature saturation.The aim of this paper is to point out the other side of the story:In some cases,the gradient of the error functions is zero not only for infinitely large weights but also for zero weights.Slow convergence in the beginning of the training procedure is often the result of sufficiently small initial weights.Therefore,we suggest that,in these cases,the initial values of the weights should be neither too large,nor too small.For instance,a typical range of choices of the initial weights might be something like(0.4,0.1) ∪(0.1,0.4),rather than(0.1,0.1) as suggested by the usual strategy.Our theory that medium size weights should be used has also been extended to a few commonly used transfer functions and error functions.Numerical experiments are carried out to support our theoretical findings. 相似文献
138.
森林火灾探测一直是森林资源保护工作中的老大难问题。早期的火灾探测技术多是基于火灾的烟雾和温度特征的,但其判别标准过于单一,误报率较高。随着计算机技术的发展和红外探测器的发明,出现了基于红外图像处理的森林火灾防护技术,该技术主要对红外探测器获得的森林现场的红外图像进行一定的处理后识别图像中是否有火灾出现。本文的主要工作是进行红外图像增强算法的研究,通过对各种算法的描述和仿真实验结果分析,提出一种相对较适合森林背景红外图像的处理算法一将基于频域处理的提升小波变换与直方图修正结合起来的红外图像增强算法。 相似文献
139.
The automated fare collection(AFC) system,also known as the transit smart card(SC) system,has gained more and more popularity among transit agencies worldwide.Compared with the conventional manual fare collection system,an AFC system has its inherent advantages in low labor cost and high efficiency for fare collection and transaction data archival.Although it is possible to collect highly valuable data from transit SC transactions,substantial efforts and methodologies are needed for extracting such data because most AFC systems are not initially designed for data collection.This is true especially for the Beijing AFC system,where a passenger’s boarding stop(origin) on a flat-rate bus is not recorded on the check-in scan.To extract passengers’ origin data from recorded SC transaction information,a Markov chain based Bayesian decision tree algorithm is developed in this study.Using the time invariance property of the Markov chain,the algorithm is further optimized and simplified to have a linear computational complexity.This algorithm is verified with transit vehicles equipped with global positioning system(GPS) data loggers.Our verification results demonstrated that the proposed algorithm is effective in extracting transit passengers’ origin information from SC transactions with a relatively high accuracy.Such transit origin data are highly valuable for transit system planning and route optimization. 相似文献
140.
物联网方兴未艾,正在世界各地掀起发展的热潮,这种发展更多的是和相关领域的应用结合在一起的。国际陆港作为典型现代物流服务产业集聚平台,成为近年来内陆地区发展外向型经济的重要模式。物联网与国际陆港发展的结合不仅是先进信息技术与物流业的融合,更为国际陆港这一现代服务业代表的发展提升注入了强大的动力,也为陆港的"智慧"发展带来了新的契机。 相似文献