全文获取类型
收费全文 | 27270篇 |
免费 | 4316篇 |
国内免费 | 3228篇 |
专业分类
电工技术 | 1465篇 |
技术理论 | 12篇 |
综合类 | 3213篇 |
化学工业 | 1534篇 |
金属工艺 | 509篇 |
机械仪表 | 1513篇 |
建筑科学 | 1275篇 |
矿业工程 | 802篇 |
能源动力 | 369篇 |
轻工业 | 515篇 |
水利工程 | 293篇 |
石油天然气 | 910篇 |
武器工业 | 337篇 |
无线电 | 4606篇 |
一般工业技术 | 2007篇 |
冶金工业 | 1240篇 |
原子能技术 | 133篇 |
自动化技术 | 14081篇 |
出版年
2024年 | 128篇 |
2023年 | 518篇 |
2022年 | 1070篇 |
2021年 | 1257篇 |
2020年 | 1245篇 |
2019年 | 906篇 |
2018年 | 769篇 |
2017年 | 931篇 |
2016年 | 1072篇 |
2015年 | 1159篇 |
2014年 | 1789篇 |
2013年 | 1685篇 |
2012年 | 2113篇 |
2011年 | 2288篇 |
2010年 | 1745篇 |
2009年 | 1807篇 |
2008年 | 1790篇 |
2007年 | 2007篇 |
2006年 | 1788篇 |
2005年 | 1469篇 |
2004年 | 1227篇 |
2003年 | 1129篇 |
2002年 | 890篇 |
2001年 | 646篇 |
2000年 | 551篇 |
1999年 | 448篇 |
1998年 | 390篇 |
1997年 | 323篇 |
1996年 | 243篇 |
1995年 | 226篇 |
1994年 | 177篇 |
1993年 | 165篇 |
1992年 | 132篇 |
1991年 | 78篇 |
1990年 | 75篇 |
1989年 | 84篇 |
1988年 | 52篇 |
1987年 | 30篇 |
1986年 | 27篇 |
1985年 | 37篇 |
1984年 | 39篇 |
1983年 | 47篇 |
1982年 | 40篇 |
1981年 | 37篇 |
1980年 | 30篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1977年 | 27篇 |
1976年 | 23篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
本文提出一种基于轮廓线匹配的二维重迭物体的识别算法,并采用一种点模式匹配的快
速算法进行特征点序列的匹配,通过引进形状移位数的概念和利用问题中的各种约束条件,提
高了物体识别速度. 相似文献
102.
103.
Sherman Seth J.; Atri Alireza; Hasselmo Michael E.; Stern Chantal E.; Howard Marc W. 《Canadian Metallurgical Quarterly》2003,117(3):526
Eight subjects studied a set of complex visual images after administration of 0.4 mg scopolamine. Another 8 subjects performed the same task without drug administration. On a subsequent item recognition test, subjects rated, on a 5-point scale, their confidence that the studied pictures and an equal number of unstudied lures were actually presented. Results showed that scopolamine affected responses to studied items, but not unstudied lures, demonstrating an unambiguous effect of scopolamine on recognition memory. To describe the scopolamine-injected subjects' data, the authors constructed a new model of 2-process recognition that includes the A. P. Yonelinas (1994) model as a limiting case. The model analysis suggests that scopolamine affected both familiarity and recollection. In particular, scopolamine did not affect the frequency with which recollection took place, but rather, affected the amount of recollected information. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
LU Jian-dong Science Technology Department Xi'an Institute of Posts Telecommunications Xi'an P.R. China 《中国邮电高校学报(英文版)》2004,11(3)
1 Introduction SinceZadeh[1] establishedfuzzysettheoryin 196 5 ,fuzzysetmakesgreatachievementintheoryandapplica tion[2~ 5] .Becausethereexistintrinsicfuzzinessinpat ternrecognition ,usingfuzzysettopatternrecognitionacquiregreatsuccess.Toexplainthedifferentandrela tionbetweenfuzzysetandprobabilitytheory ,Zadeh[6 ]introducedpossibilitytheoryin 1978.Possibilitytheoryhadbeenusedinfuzzyreason ,fuzzycontrolandexpertsystem[7~ 9] .Applingpossibilitytheoryto patternrecognitionisattemptedbyHalland… 相似文献
105.
W. J. PLUMBRIDGE Y. KARIYA 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(8):723-734
With continuing miniaturisation, increased performance demands and the requirement to remove lead from solder alloys, the challenges to structural integrity and reliability of electronic equipment are substantial and increasing. This paper outlines typical features in electronic equipment of which the structural integrity community may be generally unaware. Potential failure modes in service are described, and the problems of scale and material characteristics are considered. Progress in the application of fracture mechanics to the life prediction of interconnections is reviewed. The limited evidence available suggests that the crack growth resistance of silver‐containing lead‐free solders is superior to that of the traditional Sn‐37Pb under cycle‐controlled conditions but there is no difference when time‐dependent conditions prevail. In several respects, it is contended that the electronics sector is faced with challenges at least equivalent to those encountered in gas turbines and nuclear power generation. 相似文献
106.
107.
This paper presents an orientation-based representation for planar curves and shapes. The new representation can uniquely represent all types, of planar shapes, be it convex, nonconvex, polygonal, smoothly curved, or piecewise smooth shapes. It is based on a new parameterization, theabsolute integral orientation. This representation is invariant under translation and rotation. The absolute integral orientation is a parameter invariant under scaling. As a result, matching of similar shapes (i.e., determination of the relative orientation and the scaling factor) using the absolute integral orientation as the parameter is easier than using the arclength as the parameter. In addition, the new representation has the feature of adaptive sampling, making it more compact and efficient than arc-length-based representations. 相似文献
108.
109.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献
110.
In many automatic face recognition systems,posture constraining is a key factor preventing them from application.In this paper a series of strategies will be described to achieve a system which enables face recognition under varying pose.These approaches include the multi-view face modeling,the threschold image based face feature detection,the affine transformation based face posture normalization and the template matching based face identification.Combining all of these strategies,a face recognition system with the pose invariance is designed successfully,Using a 75MHZ Pentium PC and with a database of 75 individuals,15 images for each person,and 225 test images with various postures,a very good recognition rate of 96.89% is obtained. 相似文献