全文获取类型
收费全文 | 203325篇 |
免费 | 23147篇 |
国内免费 | 16573篇 |
专业分类
电工技术 | 19608篇 |
技术理论 | 2篇 |
综合类 | 20728篇 |
化学工业 | 24837篇 |
金属工艺 | 13803篇 |
机械仪表 | 14226篇 |
建筑科学 | 16856篇 |
矿业工程 | 7370篇 |
能源动力 | 5746篇 |
轻工业 | 20930篇 |
水利工程 | 6912篇 |
石油天然气 | 6939篇 |
武器工业 | 2868篇 |
无线电 | 22564篇 |
一般工业技术 | 17579篇 |
冶金工业 | 7722篇 |
原子能技术 | 3249篇 |
自动化技术 | 31106篇 |
出版年
2024年 | 1215篇 |
2023年 | 3234篇 |
2022年 | 7162篇 |
2021年 | 9265篇 |
2020年 | 6820篇 |
2019年 | 5022篇 |
2018年 | 5417篇 |
2017年 | 6265篇 |
2016年 | 5487篇 |
2015年 | 8663篇 |
2014年 | 11064篇 |
2013年 | 12703篇 |
2012年 | 15948篇 |
2011年 | 16867篇 |
2010年 | 15921篇 |
2009年 | 15821篇 |
2008年 | 16132篇 |
2007年 | 15564篇 |
2006年 | 14066篇 |
2005年 | 11374篇 |
2004年 | 8696篇 |
2003年 | 6462篇 |
2002年 | 6810篇 |
2001年 | 6100篇 |
2000年 | 4250篇 |
1999年 | 2023篇 |
1998年 | 904篇 |
1997年 | 696篇 |
1996年 | 581篇 |
1995年 | 486篇 |
1994年 | 406篇 |
1993年 | 314篇 |
1992年 | 261篇 |
1991年 | 212篇 |
1990年 | 151篇 |
1989年 | 162篇 |
1988年 | 99篇 |
1987年 | 77篇 |
1986年 | 64篇 |
1985年 | 23篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 23篇 |
1981年 | 28篇 |
1980年 | 44篇 |
1979年 | 44篇 |
1978年 | 2篇 |
1959年 | 40篇 |
1958年 | 2篇 |
1951年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
改性膨润土对甲基橙的吸附 总被引:4,自引:0,他引:4
在用Cu^2 A‘^3 Fe^3 对膨润土改性中,Fe^3 改性的膨润土对甲基橙的吸附性能最好,在振荡20分钟后即可达到吸附平衡。pH=3~7、用量为3g/L、25℃时对甲基橙的吸附量达到最大,在pH=7及常温条件下,铁基膨润土的用量为11g/L时,对浓度为250mg/L甲基橙的吸附量和去除率分别为22.2mg/g98.6%;对浓度为40mg/L的甲基橙去除率达97.1%。 相似文献
84.
ZHOU An-qi CUI Li 《计算机辅助绘图.设计与制造(英文版)》2014,(4):26-32
This essay concentrates on two key procedures of image mosaic--image registration and imagefusion.Becauseof the character of geometric transformation invariance of edge points, wecalculate the angle difference of the direction vector ofedge points in different images anddraw an angle difference histogramto adjust the rotationproblem. Through this way, algorithm based on gray information is expandedandcan be used in images withdisplacementand rotation. Inthe term of image fusion, wavelet multi-scale analysis is used to fuse spliced images. In order to choose the best method of imagefusion,weevaluate the results of different methods of image fusion by cross entropy. 相似文献
85.
86.
水蒸气蒸馏法提取广西百色地区迷迭香茎、叶中的挥发油,利用GC-MS联用仪进行了分析。共分离出36个峰,鉴定了其中31个化学成分,占总含量的97.08%。其主要成分为1,8-桉叶素、α-蒎烯、樟脑、莰烯、α-松油醇、乙酸龙脑酯及龙脑等。 相似文献
87.
In this paper, the control synthesis problem for a class of large‐scale systems with multi‐modes that are called large‐scale switched systems is addressed. By introducing the concept of decentralized switching signal and the relevant decentralized average dwell time, the asymptotic stability and weighted ?2 gain performance are investigated. It should be noted that the decentralized switching covers general switching cases for large‐scale switched systems, namely, it admits both time‐dependent switching signal and arbitrary switching signal blended in the decentralized switching. Then, on the basis of the analysis results, the decentralized weighted control scheme including state feedback controller gains and switching signals is studied. Several design algorithms are proposed to meet different controller design problems. Finally, numerical examples are provided to illustrate theoretical findings within this paper. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
88.
ZHOU HaiQiang JU Ping YANG Hui & SUN Ran Electrical Engineering School HoHai University Nanjing China Henan Power Dispatching & Communication Center Zhengzhou 《中国科学:信息科学(英文版)》2010,(4)
The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus... 相似文献
89.
Based on controls of structural style and the position in coalbed methane(CBM)development,we used a method of curvatures to study its relations with CBM development parameters.We calculated structural curvatures of contours of the No.3coal seam floor of the Shanxi Formation in the Zaoyuan block of the Qinshui Basin and analyzed its relations with development parameters of coalbed methane wells.The results show that structural curvature is negatively related to coal reservoir pressure,while positively related to permeability.With an increase in structural curvature,the average production of coalbed methane wells increases at first and then decreases,reaching the highest production at 0.02 m-1 of structural curvature.Therefore,structural curvature can be an important index for potential evaluation of coalbed methane development and provide a basis for siting coalbed methane wells. 相似文献
90.
An ILRIS-36D 3-D laser image scanning system was used to monitor the Anjialing strip mine slope on Pingshuo in Shanxi province.The basic working principles,performance indexes,features and data collection and processing methods are illustrated.The point cloud results are analyzed in detail.The rescale range analysis method was used to analyze the deformation characteristics of the slope.The results show that the trend of slope displacement is stable and that the degree of landslide danger is low.This work indicates that 3-D laser image scanning can supply multi-parameter,high precision real time data over long distances.These data can be used to study the distortion of the slope quickly and accurately. 相似文献